WorldWideScience

Sample records for holocene sea-level change

  1. Holocene sea-level changes in the Falkland Islands

    Science.gov (United States)

    Newton, Tom; Gehrels, Roland; Daley, Tim; Long, Antony; Bentley, Mike

    2014-05-01

    In many locations in the southern hemisphere, relative sea level (RSL) reached its maximum position during the middle Holocene. This highstand is used by models of glacial isostatic adjustment (GIA) to constrain the melt histories of the large ice sheets, particularly Antarctica. In this paper we present the first Holocene sea-level record from the Falkland Islands (Islas Malvinas), an archipelago located on the Patagonian continental shelf about 500 km east of mainland South America at a latitude of ca. 52 degrees. Unlike coastal locations in southernmost South America, Holocene sea-level data from the Falklands are not influenced by tectonics, local ice loading effects and large tidal ranges such that GIA and ice-ocean mass flux are the dominant drivers of RSL change. Our study site is a salt marsh located in Swan Inlet in East Falkland, around 50 km southwest of Stanley. This is the largest and best developed salt marsh in the Falkland Islands. Cores were collected in 2005 and 2013. Lithostratigraphic analyses were complemented by analyses of foraminifera, testate amoebae and diatoms to infer palaeoenvironments. The bedrock, a Permian black shale, is overlain by grey-brown organic salt-marsh clay, up to 90 cm thick, which, in a landward direction, is replaced by freshwater organic sediments. Overlying these units are medium-coarse sands with occasional pebbles, up to 115 cm thick, containing tidal flat foraminifera. The sandy unit is erosively overlain by a grey-brown organic salt-marsh peat which extends up to the present surface. Further away from the sea this unit is predominantly of freshwater origin. Based on 13 radiocarbon dates we infer that prior to ~9.5 ka sea level was several metres below present. Under rising sea levels a salt marsh developed which was suddenly drowned around 8.4 ka, synchronous with a sea-level jump known from northern hemisphere locations. Following the drowning, RSL rose to its maximum position around 7 ka, less than 0.5 m above

  2. Reconstructing Mid- to Late Holocene Sea-Level Change from Coral Microatolls, French Polynesia

    Science.gov (United States)

    Hallmann, N.; Camoin, G.; Eisenhauer, A.; Vella, C.; Samankassou, E.; Botella, A.; Milne, G. A.; Pothin, V.; Dussouillez, P.; Fleury, J.

    2017-12-01

    Coral microatolls are sensitive low-tide recorders, as their vertical accretion is limited by the mean low water springs level, and can be considered therefore as high-precision recorders of sea-level change. They are of pivotal importance to resolving the rates and amplitudes of millennial-to-century scale changes during periods of relative climate stability such as the Mid- to Late Holocene, which serves as an important baseline of natural variability prior to the Anthropocene. It provides therefore a unique opportunity to study coastal response to sea-level rise, even if the rates of sea-level rise during the Mid- to Late Holocene were lower than the current rates and those expected in the near future. Mid- to Late Holocene relative sea-level changes in French Polynesia encompassing the last 6,000 years were reconstructed based on the coupling between absolute U/Th dating of in situ coral microatolls and their precise positioning via GPS RTK (Real Time Kinematic) measurements. The twelve studied islands represent ideal settings for accurate sea-level studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets (far-field), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. A sea-level rise of less than 1 m is recorded between 6 and 3-3.5 ka, and is followed by a gradual fall in sea level that started around 2.5 ka and persisted until the past few centuries. In addition, growth pattern analysis of coral microatolls allows the reconstruction of low-amplitude, high-frequency sea-level change on centennial to sub-decadal time scales. The reconstructed sea-level curve extends the Tahiti last deglacial sea-level curve [Deschamps et al., 2012, Nature, 483, 559-564], and is in good agreement with a geophysical model tuned to

  3. The Caribbean conundrum of Holocene sea level.

    Science.gov (United States)

    Jackson, Luke; Mound, Jon

    2014-05-01

    In the tropics, pre-historic sea-level curve reconstruction is often problematic because it relies upon sea-level indicators whose vertical relationship to the sea surface is poorly constrained. In the Caribbean, fossil corals, mangrove peats and shell material dominate the pre-historic indicator record. The common approach to reconstruction involves the use of modern analogues to these indicators to establish a fixed vertical habitable range. The aim of these reconstructions is to find spatial variability in the Holocene sea level in an area gradually subsiding (different depths. We use the first catalogue to calibrate 14C ages to give a probabilistic age range for each indicator. We use the second catalogue to define a depth probability distribution function (pdf) for mangroves and each coral species. The Holocene indicators are grouped into 12 sub-regions around the Caribbean. For each sub-region we apply our sea-level reconstruction, which involves stepping a fixed-length time window through time and calculating the position (and rate) of sea-level (change) using a thousand realisations of the time/depth pdfs to define an envelope of probable solutions. We find that the sub-regional relative sea-level curves display spatio-temporal variability including a south-east to north-west 1500 year lag in the arrival of Holocene sea level to that of the present day. We demonstrate that these variations are primarily due to glacial-isostatic-adjustment induced sea-level change and that sub-regional variations (where sufficient data exists) are due to local uplift variability.

  4. Holocene Sea-Level Database For The Caribbean Region

    Science.gov (United States)

    Khan, N. S.; Horton, B.; Engelhart, S. E.; Peltier, W. R.; Scatena, F. N.; Vane, C. H.; Liu, S.

    2013-12-01

    Holocene relative sea-level (RSL) records from far-field locations are important for understanding the driving mechanisms controlling the nature and timing of the mid-late Holocene reduction in global meltwaters and providing background rates of late Holocene RSL change with which to compare the magnitude of 20th century RSL rise. The Caribbean region has traditionally been considered far-field (i.e., with negligible glacio-isostatic adjustment (GIA) influence), although recent investigations indicate otherwise. Here, we consider the spatial variability in glacio-isostatic, tectonic and local contributions on RSL records from the circum-Caribbean region to infer a Holocene eustatic sea-level signal. We have constructed a database of quality-controlled, spatially comprehensive, Holocene RSL observations for the circum-Caribbean region. The database contains over 500 index points, which locate the position of RSL in time and space. The database incorporates sea-level observations from a latitudinal range of 5°N to 25°N and longitudinal range of 55°W to 90°W. We include sea-level observations from 11 ka BP to present, although the majority of the index points in the database are younger than 8 ka BP. The database is sub-divided into 13 regions based on the distance from the former Laurentide Ice Sheet and regional tectonic setting. The index points were primarily derived from mangrove peat deposits, which in the Caribbean form in the upper half of the tidal range, and corals (predominantly Acropora palmata), the growth of which is constrained to the upper 5 m of water depth. The index points are classified on the basis of their susceptibility to compaction (e.g., intercalated, basal). The influence of temporal changes in tidal range on index points is also considered. The sea-level reconstructions demonstrate that RSL did not exceed the present height (0 m) during the Holocene in the majority of locations, except at sites in Suriname/Guayana and possibly Trinidad

  5. Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China)

    Science.gov (United States)

    Rolett, Barry V.; Zheng, Zhuo; Yue, Yuanfu

    2011-04-01

    Neolithic seafaring across the Taiwan Strait began approximately 5000 years ago and involved open-sea voyages over distances of at least 130 km. Rapid sea-level rise preceded the emergence of open-sea voyaging, but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood. We investigate this problem by presenting a record of Holocene sea-level change and coastal transformation based on sediment cores obtained from the Fuzhou Basin on the coast of Fujian, China. The cores are located in direct proximity to archaeological sites of the Tanshishan Neolithic culture (5000-4300 cal BP), which is significant for its similarity to the earliest Neolithic cultures of Taiwan. Multiple lines of evidence record the early Holocene inundation of the Fuzhou Basin around 9000 cal BP, the mid-Holocene sea-level highstand, and the final Holocene marine transgression. This final transition is precisely documented, with AMS dates showing the change occurred close to 1900 cal BP. Our paleogeographic reconstruction shows that a large estuary filled the Fuzhou Basin during the mid-Holocene. Tanshishan and Zhuangbianshan, two of the major Fuzhou Basin Neolithic sites, are located today on hills nearly 80 km from the modern coastline. However, when the sites were settled around 5500-5000 cal BP, the marine transgression had transformed these hills into islands in the upper estuary. We suggest that the Neolithic era estuary setting, together with the lack of land suitable for rice paddy agriculture, inhibited intensive food production but favored a maritime orientation and the development of seafaring.

  6. Holocene sea level, a semi-empirical contemplation

    Science.gov (United States)

    Bittermann, K.; Kemp, A.; Vermeer, M.; Rahmstorf, S.

    2017-12-01

    Holocene eustatic sea level from approximately -10,000-1800 CE was characterized by an increase of about 60m, with the rate progressively slowing down until sea level almost stabilizes between 500-1800 CE. Global and northern-hemisphere temperatures rose from the last glacial termination until the `Holocene Optimum'. From ­­there, up to the start of the recent anthropogenic rise, they almost steadily decline. How are the sea-level and temperature evolutions linked? We investigate this with semi-empirical sea-level models. We found that, due to the nature of Milankovitch forcing, northern-hemisphere temperature (we used the Greenland temperature by Vinther et al., 2009) is a better model driver than global mean temperature because the evolving mass of northern-hemisphere land ice was the dominant cause of Holocene global sea-level trends. The adjustment timescale for this contribution is 1200 years (900-1500 years; 90% confidence interval). To fit the observed sea-level history, the model requires a small additional constant rate (Bittermann 2016). This rate turns out to be of the same order of magnitude as reconstructions of Antarctic sea-level contributions (Briggs et al. 2014, Golledge et al. 2014). In reality this contribution is unlikely to be constant but rather has a dominant timescale that is large compared to the time considered. We thus propose that Holocene sea level can be described by a linear combination of a temperature driven rate, which becomes negative in the late Holocene (as Northern Hemisphere ice masses are diminished), and a positive, approximately constant term (possibly from Antarctica), which starts to dominate from the middle of the Holocene until the start of industrialization. Bibliography: Bittermann, K. 2016. Semi-empirical sea-level modelling. PhD Thesis University of Potsdam. Briggs, R.D., et al. 2014. A data-constrained large ensemble analysis of Antarctic evolution since the Eemian. Quaternary science reviews, 103, 91

  7. Changes in Holocene relative sea-level and coastal morphology

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Sander, Lasse; Clemmensen, Lars B

    2015-01-01

    Changes in relative sea-level (RSL) during the Holocene are reconstructed based on ground-penetrating radar (GPR) data collected across a raised beach ridge system on the island of Samsø, Denmark. The internal architecture of the beach ridge and swale deposits is divided into characteristic radar...... ridge progradation through time. The vertical levels of identified downlap points are combined with an age model based on optically stimulated luminescence-dated samples to reconstruct RSL for the past c. 5000 years. Overall, the reconstruction shows that the period between c. 4800 and 3800 yr BP...

  8. Holocene relative sea-level changes from North America and the Caribbean

    Science.gov (United States)

    Horton, Benjamin; Engelhart, Simon; Vacchi, Matteo; Khan, Nicole; Peltier, Dick; Roy, Keven

    2014-05-01

    Reconstructions of Holocene relative sea level (RSL) are important for identifying the ice equivalent meltwater contribution to sea-level change during deglaciation. Holocene RSL reconstructions from near, intermediate and far field regions enable the assessment of earth and ice parameters of Glacial Isostatic Adjustment (GIA) models. RSL reconstructions provide data for estimating rates of spatially variable and ongoing vertical land motion; a requirement for understanding the variation in modern and late Holocene sea level as recorded by instrumental and proxy records. Here we explain the methodology employed to reconstruct former sea levels, which follows the practice of the International Geoscience Programme (IGCP). We produce sea level index points from the Pacific and Atlantic coasts of North America and the Caribbean. Index points are defined as the most reliable observations of former sea levels. They consist of an estimate of X (age) and Y (the position of former RSL). Where a suite of index points are developed for a locality or region, they describe changes in RSL through time and estimate rates of change. A valid index point must meet the following four criteria; (1) location of the sample is known; (2) the altitude of the sample (and the error associated with measuring that altitude) is known; (3) the indicative meaning (the relationship between the sample and a tide level) is estimated; and (4) the age of the sample, which is commonly radiocarbon dated is calibrated to sidereal years using the latest calibration curves. In total databases have over 2000 sea-level index points from formerly ice covered, uplifting regions of Canada, to the region of forebulge collapse along the subsiding mid-Atlantic and mid-Pacific coastlines of the United States, to the tropical regions of the Caribbean. Recent analyses of these new published databases have led to a further refinement of the most recent of the ICE-NG (VMX) series of global models of GIA. The records

  9. Late Holocene higher sea level and its radiocarbon dates in Okierabu-jima, Ryukyus

    International Nuclear Information System (INIS)

    Koba, Motoharu; Omoto, Kunio; Takahashi, Tatsuo.

    1980-01-01

    Okierabu-jima of the Ryukyu Islands, which is a poly-terraced Pleistocene raised coral reef island, doesn't have a Holocene raised coral reef, but coastal erosional features showing higher sea levels in Holocene. The authors obtained some data indicating the period of one of the Holocene higher sea levels. All radiocarbon dates concerning Okierabu-jima's Holocene sea-level changes are plotted on the date-height coordinates. The paleo sea level between 5000 and 2000 y. B. P. lies above the broken line drawn from 6 m below to 2.18 m above the present sea level. The period of the highest sea level in Holocene seems to be about 3000 to 2000 y. B. P. in this island. Its height is presumably 2.4 m a. s. l. derived on an average from heights of stacks and coastal benches in the almost all coasts of the island (Koba, 1974). Beach rocks were already formed at the landward extremity of the reef flat corresponding to the almost present sea level about 1300 y. B. P. (author)

  10. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction.

    Science.gov (United States)

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A; Leorri, Eduardo

    2016-12-08

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

  11. Holocene sea-level changes along the Strait of Magellan and Beagle Channel, southernmost South America

    Science.gov (United States)

    Porter, Stephen C.; Stuiver, Minze; Heusser, Calvin J.

    1984-07-01

    Radiocarbon-dated marine sediments from five coastal sites along the Strait of Magellan and Beagle Channel in southernmost Chile permit construction of a curve of relative sea-level fluctuations during the Holocene. Morphologic and stratigraphic data point to coastal submergence during the early Holocene as the sea rose to a maximum level at least 3.5 m higher than present about 5000 yr ago. Progressive emergence then followed during the late Holocene. Data from widely separated localities define a smooth curve, the form of which is explainable in terms of isostatic and hydroisostatic deformation of the crust resulting from changing ice and water loads. Apparently anomalous data from one site located more than 100 km behind the outer limit of the last glaciation may reflect isostatic response to deglaciation. The sea-level curve resembles one derived by Clark and Bloom (1979, In "Proceedings of the 1978 International Symposium on Coastal Evolution in the Quaternary, Sao Paulo, Brasil," pp. 41-60. Sao Paulo) using a spherical Earth model, both in amplitude and in the timing of the maximum submergence.

  12. Holocene sea-level changes in King George Island, West Antarctica, by virtue of geomorphological coastal evidences and diatom assemblages of sediment sections.

    Science.gov (United States)

    Poleshchuk, Ksenia; Verkulich, Sergey; Pushina, Zina; Jozhikov, Ilya

    2015-04-01

    A new curve of relative sea-level change is presented for the Fildes peninsula, King George Island, West Antarctic. This work is based on renewed paleogeography data, including coastal geomorphological evidence, diatom assemblages of lakes bottom sediments and radiocarbon datings of organics. The new data were obtained in several sections of quaternary sediments and groups of terraces, and allows us to expand and improve relevant conception about relative sea level changes in the King George Island region. The new radiocarbon datings of organics (mosses and shells) allows reconstructing Holocene conditions that maintain and cause the sea-level changes. Sea diatom assemblages of Dlinnoye lake bottom sediment core (that complies period about 8000 years B.P.) mark altitude of marine water penetrated into the lake. The altitudes of shell remains, which have certain life habits and expect specific salinity and depth conditions, coupled with their absolute datings, indicate the probable elevation of the past sea level. The Mid-Holocene marine transgression reached its maximum level of 18-20 m by 5760 years B.P. The transgression influenced the deglaciation of the Fildes peninsula and environment conditions integrally. The ratio of glacio-isostatic adjustment velocity and Holocene transgression leaded to the decrease of relative sea level during the Late Holocene excluding the short period of rising between 2000 and 1300 years B.P. Comparing this data with the curve for Bunger oasis, East Antarctica, introduced earlier gives an interesting result. Despite the maximum altitudes of relative sea-level rise in King George region were higher and occurred later than in Bunger oasis region, the short-term period of Late Holocene sea-level rising contemporizes. Besides that, this work allow to realize a correlation between regions of Antarctica and adjacent territory. That, in turn, lets answer the question of tectonic and eustatic factors ratio and their contribution to the

  13. Late mid-Holocene sea-level oscillation: A possible cause

    Science.gov (United States)

    Scott, D. B.; Collins, E. S.

    Sea level oscillated between 5500 and 3500 years ago at Murrells Inlet, South Carolina, Chezzetcook and Baie Verte, Nova Scotia and Montmagny, Quebec. The oscillation is well constrained by foraminiferal marsh zonations in three locations and by diatoms in the fourth one. The implications are: (1) there was a eustatic sea-level oscillation of about 2-10 m in the late mid-Holocene on the southeast coast of North America (South Carolina to Quebec) that is not predicted by present geophysical models of relative sea-level change; (2) this oscillation coincides with oceanographic cooling on the east coast of Canada that we associate with melting ice; and (3) this sea- level oscillation/climatic event coincides exactly with the end of pyramid building in Egypt which is suggested to have resulted from a climate change (i.e. drought, cooling). This sea-level/climatic change is a prime example of feedback where climatic warming in the mid-Holocene promoted ice melt in the Arctic which subsequently caused climatic cooling by opening up Arctic channels releasing cold water into the Inner Labrador Current that continued to intensify until 4000 years ago. This sea-level event may also be the best way of measuring when the final ice melted since most estimates of the ages of the last melting are based on end moraine dates in the Arctic which may not coincide with when the last ice actually melted out, since there is no way of dating the final ice positions.

  14. Holocene sea-level fluctuation in the southern hemisphere

    Science.gov (United States)

    Isla, Federico Ignacio

    If rising sea levels dominate in the northern hemisphere (NH), falling or fluctuating sea levels predominate in the southern hemisphere (SH). Endogenic processes (tectonics, isostasy or geoidal changes) could explain local or regional mean sea level (MSL) fluctuations but not an hemispherical one. Evidence from South America, Africa, Antarctica, Australia and the Pacific and Indian Oceans suggest that the Holocene transgression rose above the present MSL, in higher latitudes before the tropics. By plotting latitude against the age of MSL arrival at present coasts, good correlation is observed. Oceanic salinity mixing has been already proposed to explain this mid-Holocene sea-level fluctuation. Climate could be the only factor responsible for this hemisphere-wide behavior of MSL. It has been suggested previously that the climate of the SH precedes that of the NH by 3000 years. The climatic optimum, or maximum warmth, occurred predominantly about 6000 BP in the NH, but about 10-9000 BP in the SH. Short-term climatic effects on the sea level (monsoons, southern oscillation/El Niño phenomena) should have significant occurrences during the past in the windiest oceanic hemisphere. This latitudinal trend in former MSL should be considered when using shorelines as reference points for measuring vertical crustal movements.

  15. Roles of Sea Level and Climate Change in the Development of Holocene Deltaic Sequences in the Yellow Sea

    Science.gov (United States)

    Liu, J.; Milliman, J. D.

    2002-12-01

    Both post-glacial sea-level and climatic changes are preserved in the the shallow, low gradient, sediment-dominated Yellow Sea. As a result of rapid flooding during melt-water pulse (MWP) 1A, 14.3-14.1 ka BP, sea level reached the southern edge of the North Yellow Sea (NYS), and after MWP-1B (11.6-11.4 ka BP) sea level entered the Bohai Sea. The first major Yellow River-derived deltaic deposit formed in the NYS during decelerated transgression following MWP-1B and increased river discharge in response to re-intensification of the summer monsoon about 11 ka cal BP. A second subaqueous delta formed in the South Yellow Sea about 9-7 ka BP during decelerated transgression after MWP-1C flooding and in response to the southern shift of the Yellow River mouth. The modern subaqueous and subaerial deltas in the west Bahai Gulf and (to a lesser extent) along the Jiangus coast have formed during the modern sea-level highstand. These changing Holocene patterns are most clearly illustrated by a short film clip.

  16. The magnitude of a mid-Holocene sea-level highstand in the Strait of Makassar

    NARCIS (Netherlands)

    Mann, T.; Rovere, A.; Schöne, T.; Klicpera, A.; Stocchi, P.; Lukman, M.; Westphal, H.

    2016-01-01

    Knowledge on the timing andmagnitude of past sea-level changes is essential to understandmodern and futuresea-level variability.Holocene sea-level data fromliterature on thewest coast of Sulawesi, central Indonesia, suggestthat this region experienced two relative sea-level highstands over the last

  17. Holocene sea levels of Visakhapatnam shelf, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, K.M.; Rao, T.C.S.

    The Holocene sea level changes in the shelf areas off Visakhapatnam was studied from sediment distribution pattern and shallow seismic profiling. Morphological features on the shelf indicate a Late Pleistocene regression down to about -130 m below...

  18. Ground-Penetrating Radar Study of Fort Morgan Peninsula Holocene Beach Ridges as Sea-level Indicators

    Science.gov (United States)

    Philbin, A.; Frederick, B.; Blum, M. D.; Tsoflias, G. P.

    2017-12-01

    Holocene sea-level change along the northern Gulf of Mexico (GoM) coast is controversial. One view interprets basal peats from the Mississippi Delta to indicate continual sea-level (SL) rise for the GoM as a whole. An alternate view proposes that data from the subsiding delta is primarily a subsidence signal, and that sandy non-deltaic shorelines indicate that regional SL reached present elevations by the middle Holocene, with minor oscillations since then. In fact, new regional long-term subsidence records from biostratigraphic indicators display significant subsidence in deltaic areas where basal-peat data were collected, and negligible rates along the GoM shoreline to the east. However, the use of sandy progradational shorelines, commonly known as "beach ridge systems", has been criticized for a lack of precise sea-level indicators, and therefore discounted. This research focuses on developing Holocene progradational sandy shorelines along the Alabama coast in the eastern GoM as SL indicators. Sandy shorelines in this area are ideal to examine SL change because they are well preserved, sufficiently distant from the subsiding delta, well mapped, and ages are known from previous work. Two-dimensional ground-penetrating radar imaging of well-dated beach-ridge successions is used here to examine and identify changes through time in the elevation of the shoreface clinoform topset-foreset break, which represents the transition between flat-lying foreshore and seaward-dipping shoreface facies, and forms in the intertidal zone. Beach-ridge successions with optical luminescence ages of ca. 5500-4800 yrs BP display topset-foreset breaks at current mean sea-level elevation, whereas beach-ridge successions from ca. 3500-2400 yrs BP display topset-foreset breaks that are 1 m above present mean SL and the elevation of modern topset-foreset breaks. These data support the view that current sea-level was reached by the middle Holocene, and was higher than present for at least

  19. Application of /sup 14/C-dating to sedimentary geology and climatology: Sea-level and climate change during the Holocene

    Energy Technology Data Exchange (ETDEWEB)

    Nakai, Nobuyuki; Ohishi, Shyoji; Kuriyama, Toyoko; Nakamura, Toshio

    1987-11-01

    AMS /sup 14/C dating of small sized fossil shells, wood chips and sedimentary humic matter has been applied to the investigation of paleoclimatic and sea-level changes in the Holocene, using three estuarine and brackish lake sediment cores, drilled in Kawasaki city and Lake Hamanako, Japan. Precise and detailed ages at differing depths clarified large transitions of Holocene sedimentation rates, of two orders of magnitude. The vertical variation in delta/sup 13/C and C/N results for sedimentary organic matter, combined with AMS /sup 14/C ages, established continous climatic and sea-level fluctuation patterns through time and indicated the existence of neoglaciation coincident with the marine regression at 7500 to 7000 yr BP.

  20. Bayesian Statistical Analysis of Historical and Late Holocene Rates of Sea-Level Change

    Science.gov (United States)

    Cahill, Niamh; Parnell, Andrew; Kemp, Andrew; Horton, Benjamin

    2014-05-01

    A fundamental concern associated with climate change is the rate at which sea levels are rising. Studies of past sea level (particularly beyond the instrumental data range) allow modern sea-level rise to be placed in a more complete context. Considering this, we perform a Bayesian statistical analysis on historical and late Holocene rates of sea-level change. The data that form the input to the statistical model are tide-gauge measurements and proxy reconstructions from cores of coastal sediment. The aims are to estimate rates of sea-level rise, to determine when modern rates of sea-level rise began and to observe how these rates have been changing over time. Many of the current methods for doing this use simple linear regression to estimate rates. This is often inappropriate as it is too rigid and it can ignore uncertainties that arise as part of the data collection exercise. This can lead to over confidence in the sea-level trends being characterized. The proposed Bayesian model places a Gaussian process prior on the rate process (i.e. the process that determines how rates of sea-level are changing over time). The likelihood of the observed data is the integral of this process. When dealing with proxy reconstructions, this is set in an errors-in-variables framework so as to take account of age uncertainty. It is also necessary, in this case, for the model to account for glacio-isostatic adjustment, which introduces a covariance between individual age and sea-level observations. This method provides a flexible fit and it allows for the direct estimation of the rate process with full consideration of all sources of uncertainty. Analysis of tide-gauge datasets and proxy reconstructions in this way means that changing rates of sea level can be estimated more comprehensively and accurately than previously possible. The model captures the continuous and dynamic evolution of sea-level change and results show that not only are modern sea levels rising but that the rates

  1. New constraints on late Holocene eustatic sea-level changes from Mahé, Seychelles

    Science.gov (United States)

    Woodroffe, Sarah A.; Long, Antony J.; Milne, Glenn A.; Bryant, Charlotte L.; Thomas, Alexander L.

    2015-05-01

    This study provides new estimates of globally integrated ice sheet melt during the late Holocene (since 4 ka BP) from Seychelles in the western Indian Ocean, a tectonically stable, far field location where the necessary Glacial-Isostatic Adjustment (GIA) correction is small and is relatively insensitive to predictions using different Earth viscosity profiles. We compare sea level data from Seychelles to estimates of eustasy from two GIA models, ICE-5G and EUST3, which represent end-members in the quantity of global melt during the late Holocene. We use data from a range of coastal environments including fringing reef, present day beaches, fossil plateau and mangrove deposits on the largest island of the Seychelles archipelago, Mahé to reconstruct relative sea-level changes. Our data suggest that extensive coastal deposits of carbonate-rich sands that fringe the west coast formed in the last 2 ka and the horizontal nature of their surface topography suggests RSL stability during this period. Mangrove sediments preserved behind these deposits and in river mouths date to c. 2 ka and indicate that RSL was between -2 m and present during this interval. Correcting the reconstructed sea level data using a suite of optimal GIA models based on the two ice models mentioned above and a large number (c. 350) of Earth viscosity models gives a result that is consistent with the sedimentological constraints. When uncertainties in both model results and data are considered, it is possible to rule out eustatic sea levels below c. 2 m and more than a few decimetres above present during the past two millennia. This uncertainty is dominated by error in the reconstructions rather than the model predictions. We note, however, that our estimates of eustasy are more compatible with the EUST3 model compared to the ICE-5G model during the late Holocene (2-1 ka BP). Our evidence from Seychelles shows that the timing of when eustatic sea level first rose close to present is between the

  2. Coastal lagoons and beach ridges as complementary sedimentary archives for the reconstruction of Holocene relative sea-level changes

    DEFF Research Database (Denmark)

    Sander, Lasse; Hede, Mikkel Ulfeldt; Fruergaard, Mikkel

    2016-01-01

    Coastal lagoons and beach ridges are genetically independent, though non-continuous, sedimentary archives. We here combine the results from two recently published studies in order to produce an 8000-year-long record of Holocene relative sea-level changes on the island of Samsø, southern Kattegat,...

  3. Sea-level change and demography during the last glacial termination and early Holocene across the Australian continent

    Science.gov (United States)

    Williams, Alan N.; Ulm, Sean; Sapienza, Tom; Lewis, Stephen; Turney, Chris S. M.

    2018-02-01

    Future changes in sea-level are projected to have significant environmental and social impacts, but we have limited understanding of comparable rates of change in the past. Using comprehensive palaeoenvironmental and archaeological datasets, we report the first quantitative model of the timing, spatial extent and pace of sea-level change in the Sahul region between 35-8 ka, and explore its effects on hunter-gatherer populations. Results show that the continental landmass (excluding New Guinea) increased to 9.80 million km2 during the Last Glacial Maximum (LGM), before a reduction of 2.12 million km2 (or ∼21.6%) to the early Holocene (8 ka). Almost 90% of this inundation occurs during and immediately following Meltwater Pulse (MWP) 1a between 14.6 and 8 ka. The location of coastlines changed on average by 139 km between the LGM and early Holocene, with some areas >300 km, and at a rate of up to 23.7 m per year (∼0.6 km land lost every 25-year generation). Spatially, inundation was highly variable, with greatest impacts across the northern half of Australia, while large parts of the east, south and west coastal margins were relatively unaffected. Hunter-gatherer populations remained low throughout (hypothesis that late Pleistocene coastal populations were low, with use of coastal resources embedded in broad-ranging foraging strategies, and which would have been severely disrupted in some regions and at some time periods by sea-level change outpacing tolerances of mangals and other near-shore ecological communities.

  4. Discontinuity surfaces and event stratigraphy of Okha Shell Limestone Member: Implications for Holocene sea level changes, western India

    Science.gov (United States)

    Bhonde, Uday; Desai, Bhawanisingh G.

    2011-08-01

    The Okha Shell Limestone Member of Chaya Formation is the coarse grained, shell rich deposit commonly recognized as the beach rocks. It has been age bracketed between Late Pleistocene and Holocene. Late Quaternary sea level changes have been studied with beach rocks along the Saurashtra coastal region. The present study has been carried out in the Okhamandal area of the Saurashtra peninsula especially on the Okha Shell Limestone Member as exposed at various locations along the coast from north to south. Temporal and spatial correlations of the observations have revealed three events in the Okha Shell Limestone Member of Chaya Formation that are correlated laterally. The events show depositional breaks represented by discontinuity surfaces, the taphofacies varieties and ichnological variations. The present study in the context of available geochrnological data of the region suggests a prominent depositional break representing low sea level stand (regression) during an Early Holocene during the deposition of Okha Shell Limestone Member.

  5. A Mid-Holocene Relative Sea-Level Stack, New Jersey, USA

    Science.gov (United States)

    Horton, B.; Walker, J. S.; Kemp, A.; Shaw, T. J.; Kopp, R. E.

    2017-12-01

    Most high resolution (decimeter- and decadal-scale) relative sea-level (RSL) records using salt-marsh microfossils as a proxy only extend through the Common Era, limiting our understanding of driving mechanisms of RSL change and how sea-level is influenced by changing climate. Records beyond the Common Era are limited by the depth of continuous sequences of salt-marsh peat suitable for high resolution reconstructions, as well as contamination by local processes such as sediment compaction. In contrast, sequences of basal peats have produced compaction-free RSL records through the Holocene, but at a low resolution (meter- and centennial-scale). We devise a new Multi-Proxy Presence/Absence Method (MP2AM) to develop a mid-Holocene RSL stack. We stack a series of 1 m basal peat cores that overlap along a uniform elevational gradient above an incompressible basal sand. We analyzed three sea-level indicators from 14 cores: foraminifera, testate amoebae, and stable carbon isotope geochemistry. To reconstruct RSL, this multi-proxy approach uses the timesaving presence/absence of forams and testates to determine the elevation of the highest occurrence of forams and the lowest occurrence of testates in each basal core. We use stable carbon isotope geochemistry to determine the C3/C4 vegetation boundary in each core. We develop age-depth models for each core using a series of radiocarbon dates. The RSL records from each 1 m basal core are combined to create a stack or, in effect, one long core of salt-marsh material. This method removes the issue of compaction to create a continuous RSL record to address temporal changes and periods of climate and sea-level variability. We reconstruct a southern NJ mid-Holocene RSL record from Edwin B. Forsythe National Wildlife Refuge, where Kemp et al. (2013) completed a 2500 yr RSL record using a foraminifera-based transfer function approach. Preliminary radiocarbon dates suggest the basal sequence is at least 4246-4408 cal yrs BP

  6. Coastal Marsh Longevity, Ecological Succession, and Organic Carbon Dynamics During Early Holocene Sea-Level Rise

    Science.gov (United States)

    Vetter, L.; Schreiner, K. M.; Rosenheim, B. E.; Tornqvist, T. E.

    2016-02-01

    Coastal marsh environments perform essential ecosystem services, including nutrient filtering, soil organic matter storage, and storm surge abatement, yet much is still unknown about their formation and fate under periods of sea-level change. During the early Holocene (7-10 ka), rapid sea-level rise in coastal Louisiana was one of the primary controls over marsh development and longevity. Here, we investigate plant community composition and succession and soil organic matter storage in early Holocene coastal marshes in Louisiana using bulk elemental ratios, lignin phenol biomarkers and stable isotopes from peat layers. Sediment cores were collected in southeastern Louisiana and contain a record of an early Holocene transgressive sea-level sequence 16-25 m below present sea-level. The sedimentary record consists of an immature paleosol overlain by basal peat that accumulated in an estuarine marsh, overlain by marine lagoonal muds. A re-established marsh peat is present 1-4 m above the initial transition to marine conditions, indicating a sequence of marsh development, sea-level rise and onset of marine conditions, and then further marsh development as the rate of relative sea-level rise decelerated. Plant community composition in coastal marshes was determined through cupric oxide oxidation and lignin-phenol and non-lignin-phenol biomarker abundances. The degradation state of soil organic matter and the specific source of stabilized organic matter within the sedimentary peats were determined through lignin-phenol biomarker ratios. Organic matter sources ranged from terrestrial to marine over the course of sea-level rise, and different sites showed different amounts of marine organic matter influence and different levels of terrestrial organic matter degradation. These results have important implications for reconstructing the response of coastal marshes and their plant communities to accelerated rates of sea-level rise projected through 2100.

  7. Glacial-interglacial changes and Holocene variations in Arabian Sea denitrification

    Science.gov (United States)

    Gaye, Birgit; Böll, Anna; Segschneider, Joachim; Burdanowitz, Nicole; Emeis, Kay-Christian; Ramaswamy, Venkitasubramani; Lahajnar, Niko; Lückge, Andreas; Rixen, Tim

    2018-01-01

    At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific. We calculated composite sea surface temperature (SST) and δ15N ratios in time slices of 1000 years of the last 25 kyr to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Low δ15N values of 4-7 ‰ during the last glacial maximum (LGM) and stadials (Younger Dryas and Heinrich events) suggest that denitrification was inactive or weak during Pleistocene cold phases, while warm interstadials (ISs) had elevated δ15N. Fast changes in upwelling intensities and OMZ ventilation from the Antarctic were responsible for these strong millennial-scale variations during the glacial. During the entire Holocene δ15N values > 6 ‰ indicate a relatively stable OMZ with enhanced denitrification. The OMZ develops parallel to the strengthening of the SW monsoon and monsoonal upwelling after the LGM. Despite the relatively stable climatic conditions of the Holocene, the δ15N records show regionally different trends in the Arabian Sea. In the upwelling areas in the western part of the basin, δ15N values are lower during the mid-Holocene (4.2-8.2 ka BP) compared to the late Holocene ( ventilation of the OMZ during the period of the most intense southwest monsoonal upwelling. In contrast, δ15N values in the northern and eastern Arabian Sea rose during the last 8 kyr. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position in the northeast was established during the middle and late Holocene. This was

  8. Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification

    Directory of Open Access Journals (Sweden)

    B. Gaye

    2018-01-01

    Full Text Available At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific. We calculated composite sea surface temperature (SST and δ15N ratios in time slices of 1000 years of the last 25 kyr to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Low δ15N values of 4–7 ‰ during the last glacial maximum (LGM and stadials (Younger Dryas and Heinrich events suggest that denitrification was inactive or weak during Pleistocene cold phases, while warm interstadials (ISs had elevated δ15N. Fast changes in upwelling intensities and OMZ ventilation from the Antarctic were responsible for these strong millennial-scale variations during the glacial. During the entire Holocene δ15N values  >  6 ‰ indicate a relatively stable OMZ with enhanced denitrification. The OMZ develops parallel to the strengthening of the SW monsoon and monsoonal upwelling after the LGM. Despite the relatively stable climatic conditions of the Holocene, the δ15N records show regionally different trends in the Arabian Sea. In the upwelling areas in the western part of the basin, δ15N values are lower during the mid-Holocene (4.2–8.2 ka BP compared to the late Holocene ( <  4.2 ka BP due to stronger ventilation of the OMZ during the period of the most intense southwest monsoonal upwelling. In contrast, δ15N values in the northern and eastern Arabian Sea rose during the last 8 kyr. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position

  9. Patch-reef morphology as a proxy for Holocene sea-level variability, Northern Florida Keys, USA

    Science.gov (United States)

    Brock, J.C.; Palaseanu-Lovejoy, M.; Wright, C.W.; Nayegandhi, A.

    2008-01-01

    A portion of the northern Florida Keys reef tract was mapped with the NASA Experimental Advanced Airborne Research Lidar (EAARL) and the morphology of patch reefs was related to variations in Holocene sea level. Following creation of a lidar digital elevation model (DEM), geospatial analyses delineated morphologic attributes of 1,034 patch reefs (reef depth, basal area, height, volume, and topographic complexity). Morphometric analysis revealed two morphologically different populations of patch reefs associated with two distinct depth intervals above and below a water depth of 7.7 m. Compared to shallow reefs, the deep reefs were smaller in area and volume and showed no trend in topographic complexity relative to water depth. Shallow reefs were more variable in area and volume and became flatter and less topographically complex with decreasing water depth. The knoll-like morphology of deep reefs was interpreted as consistent with steady and relatively rapidly rising early Holocene sea level that restricted the lateral growth of reefs. The morphology of shallow 'pancake-shaped' reefs at the highest platform elevations was interpreted as consistent with fluctuating sea level during the late Holocene. Although the ultimate cause for the morphometric depth trends remains open to interpretation, these interpretations are compatible with a recent eustatic sea-level curve that hindcasts fluctuating late Holocene sea level. Thus it is suggested that the morphologic differences represent two stages of reef accretion that occurred during different sea-level conditions. ?? 2008 Springer-Verlag.

  10. New evidence for "far-field" Holocene sea level oscillations and links to global climate records

    Science.gov (United States)

    Leonard, N. D.; Welsh, K. J.; Clark, T. R.; Feng, Y.-x.; Pandolfi, J. M.; Zhao, J.-x.

    2018-04-01

    Rising sea level in the coming century is of significant concern, yet predicting relative sea level change in response to eustatic sea level variability is complex. Potential analogues are provided by the recent geological past but, until recently, many sea level reconstructions have been limited to millennial scale interpretations due to age uncertainties and paucity in proxy derived records. Here we present a sea level history for the tectonically stable "far-field" Great Barrier Reef, Australia, derived from 94 high precision uranium-thorium dates of sub-fossil coral microatolls. Our results provide evidence for at least two periods of relative sea level instability during the Holocene. These sea level oscillations are broadly synchronous with Indo-Pacific negative sea surface temperature anomalies, rapid global cooling events and glacial advances. We propose that the pace and magnitude of these oscillations are suggestive of eustatic/thermosteric processes operating in conjunction with regional climatic controls.

  11. Regional, holocene records of the human dimension of global change: sea-level and land-use change in prehistoric Mexico

    Science.gov (United States)

    Sluyter, Andrew

    1997-02-01

    Regional, Holocene records hold particular relevance for understanding the reciprocal nature of global environmental change and one of its major human dimensions: "sustainable agriculture", i.e., food production strategies which entail fewer causes of and are less susceptible to environmental change. In an epoch of accelerating anthropogenic transformation, those records reveal the protracted regional causes and consequences of change (often agricultural) in the global system as well as informing models of prehistoric, intensive agriculture which, because of long tenures and high productivities, suggest strategies for sustainable agricultural in the present. This study employs physiographic analysis and the palynological, geochemical record from cores of basin fill to understand the reciprocal relation between environmental and land-use change in the Gulf of Mexico tropical lowland, focusing on a coastal basin sensitive to sea-level change and containing vestiges of prehistoric settlement and wetland agriculture. Fossil pollen reveals that the debut of maize cultivation in the Laguna Catarina watershed dates to ca. 4100 BC, predating the earliest evidence for that cultivar anywhere else in the lowlands of Middle America. Such an early date for a cultivar so central to Neotropical agroecology and environmental change, suggests the urgency of further research in the study region. Moreover, the longest period of continuous agriculture in the basin lasted nearly three millennia (ca. 2400 BC-AD 550) despite eustatic sea-level rise. Geochemical fluxes reveal the reciprocity between land-use and environmental change: slope destabilization, basin aggradation, and eutrophication. The consequent theoretical implications pertain to both applied and basic research. Redeploying ancient agroecologies in dynamic environments necessitates reconstructing the changing operational contexts of putative high productivity and sustainability. Adjusting land use in the face of global

  12. Holocene paleo-sea level changes along the coast of Rio de Janeiro, southern Brazil: Comment on Castro et al. (2014).

    Science.gov (United States)

    Angulo, Rodolfo J; Giannini, Paulo C F; Souza, Maria Cristina DE; Lessa, Guilherme C

    2016-01-01

    The present work discusses and reinterprets paleo-sea level indicators used to build Holocene sea-level curve for the coast of Rio de Janeiro at former works. We conclude that: (a) the paleo-sea levels inferred by vermetid remains show that sea-level has fallen over the past 4400 years, at least; (b) the paleo-sea level inferred by the beachrock facies and dated shells of Jaconé shows that sea-level was near the present elevation between 8198 and 5786 years before present; and (c) several shells from other beachrocks were deposited probably thousands of years after the specimens died and consequently do not allow precise reconstructions of paleo-sea levels. These conclusions differ from the conclusions of the original paper.

  13. Late Glacial to Holocene evolution and sea-level history of Gulf of Gemlik, Sea of Marmara, Turkey

    Science.gov (United States)

    Sabuncu, Asen; Kadir Eriş, K.; Kaslilar, Ayse; Namık Çaǧatay, M.; Gasperini, Luca; Filikçi, Betül

    2016-04-01

    The Gulf of Gemlik is an E-W elongated trans-tensional basin with a maximum depth of 113 m, located on the middle strand of the North Anatolian Fault (NAF) in the south eastern part of the Sea of Marmara (SoM). While during the Holocene the sea level in the Gulf of Gemlik changed in tandem with the water level changes in the SoM, it may have been different in the late glacial when the Sea of Marmara was lacustrine. Beside the tectonic activity related to the NAFZ, eustatic sea level changes would have controlled the basin evolution and consequent sedimentary history during the different paleocanographic phases of the SoM. Considering the limited studies on the late glacial-Holocene stratigraph of the Gulf of Gemlik, this study aims to investigate the depositional units and their environments with respect to different allogenic and autogenic controls. For these purposes, we analyzed over 300 2 - 7 kHz bandwidth high-resolution gridded seismic sub-bottom CHIRP profiles together with 70 kHz high resolution multibeam bathymetry with backscatter data. Four seismic stratigraphic units were defined and correlated with chronstratigraphic units in five piston cores covering the last 15.8 ka BP according to radiocarbon ages (14C). The depth-scale accuracy of chronostratigraphic units in cores is of key importance for the precise calculation of sedimentation rates. Correlation between the seismic profiles and cores were made by matching Multi-Sensor Core-Logger (MSCL) data and seismic reflection coefficients and amplitudes for different stratigraphic units. The impedance data derived from the logger were used to generate a synthetic seismogram. We used an approach to display, estimate, and correct the depth-scale discrepancies due to oversampling affecting the upper part of sedimentary series during piston coring. The method is based on the resynchronization of synthetic seismograms computed from high-quality physical property logs to the corresponding CHIRP profiles. Each

  14. A marine to freshwater sediment succession from Kowhai Beach wetland, Northland : implications for Holocene sea level

    International Nuclear Information System (INIS)

    Hicks, H.; Nichol, S.L.

    2007-01-01

    An infilled wetland located behind coastal dunes in north-east Northland is used to reconstruct a local history of environmental change spanning early Holocene (c. 7000 yr BP) to modern time. Proxy indicators (sediment texture, diatoms and pollen) provide evidence for a transition from marginal marine- to brackish- to freshwater-conditions in the wetland. Radiocarbon ages constrain the chronology of this succession to 7880-7430 cal. yr BP for the early period of marine conditions, 3570-3210 cal. yr BP for the latter brackish phase and 1060-800 cal. yr BP for the change to freshwater conditions. Within this succession, the diatom record preserves a strong brackish signal at core depths above the limit of the modern tidal range. This is presented as preliminary evidence for a mid-Holocene sea level highstand for northern New Zealand of approximately 1.2 m above present mean sea level. (author). 40 refs., 7 figs., 1 tab

  15. Last Glacial Maximum to Holocene climate evolution controlled by sea-level change, Leeuwin Current, and Australian Monsoon in the Northwestern Australia

    Science.gov (United States)

    Ishiwa, T.; Yokoyama, Y.; McHugh, C.; Reuning, L.; Gallagher, S. J.

    2017-12-01

    The transition from cold to warm conditions during the last deglaciation influenced climate variability in the Indian Ocean and Pacific as a result of submerge of continental shelf and variations in the Indonesian Throughflow and Australian Monsoon. The shallow continental shelf (Program Expedition 356 Indonesian Throughflow drilled in the northwestern Australian shallow continental shelf and recovered an interval from the Last Glacial Maximum to Holocene in Site U1461. Radiocarbon dating on macrofossils, foraminifera, and bulk organic matter provided a precise age-depth model, leading to high-resolved paleoclimate reconstruction. X-ray elemental analysis results are interpreted as an indicator of sedimentary environmental changes. The upper 20-m part of Site U1461 apparently records the climate transition from the LGM to Holocene in the northwestern Australia, which could be associated with sea-level change, Leeuwin Current activity, and the Australian Monsoon.

  16. Past sea level changes along the western continental margins of India: Evidences from morphology of the sea bed

    Digital Repository Service at National Institute of Oceanography (India)

    Vora, K.H.

    -wide have been affected to a considerable extent by Pleistocene glaciations (Emery, 1968). The rate of sea-level rise has varied frequently and the sea-level still stands produced wave-cut terraces and platforms. In other words, the surface of a terrace... Merh (1992) while reviewing Quaternary sea level changes along India’s coasts observed that the Last Glacial Stage was a period of regression when the sea level went down to almost -150 m. With the advent of the Holocene, the sea started rising...

  17. Millennial, centennial and decadal sea- level change in Florida, USA

    Science.gov (United States)

    Kemp, A.; Hawkes, A. D.; Donnelly, J. P.; Horton, B. P.

    2012-12-01

    Reconstructions of relative sea-level changes on millennial timescales provide data against which to test and calibrate Earth-Ice models. On the U.S. mid-Atlantic coast they constrain the geometry of the Laurentide Ice Sheet's collapsing forebulge. Sea -level data from southeastern Atlantic coast additionally constrain ice-equivalent meltwater input. Here we produce the first Holocene sea-level curve for Florida and Georgia from the St. Mary's River using agglutinated foraminifera preserved in radiocarbon-dated brackish and salt-marsh sediment. The use of foraminfera as sea-level indicators was underpinned by local and regional datasets describing the modern distribution of assemblages that are analogues for those preserved in buried sediment. This approach produced 25 index points that record 5.2 m of relative sea level rise over the last 8000 years with no evidence of a mid Holocene high stand. These reconstructions indicate that existing GIA models do not replicate proxy reconstructions and that northern Florida is subsiding in response to ongoing forebulge collapse at an estimated rate of approximately 0.3 mm/yr. Over multi decadal time scales, detailed sea level reconstructions provide an appropriate geological context for modern rates of sea-level rise. Reconstructions spanning the last 2000 years of known climate variability are important for developing models with predictive capacity that link climate and sea level changes. A reconstruction of sea-level changes since 2000 years BP was developed using a core of brackish marsh sediment from the Nassau River in Florida. Foraminifera estimated the elevation of former sea level with an uncertainty of ± 10 cm. Consistent downcore assemblages indicate that the marsh maintained its tidal elevation for 2000 years. An age depth model was developed for the core results from radiocarbon dating, 210Pb and 137Cs. The resulting relative sea level record was adjusted for the contribution made by glacio

  18. Fluvial Responses to Holocene sea Level Variations Along the Macdonald River, New South Wales, Australia

    Science.gov (United States)

    Rustomji, P.; Chappell, J.; Olley, J.

    2003-12-01

    The Macdonald River drains the rugged eastern flanks of Australia's Great Dividing Range. It has a catchment area of 2000km2, restricted alluvial lowlands confined by bedrock interfluves and flows into the Hawkesbury River, a larger estuarine valley. The Macdonald valley is presently tidal for 14km from the Hawkesbury. At about 8000 year before present (BP), rising sea level invaded the Macdonald Valley for at least 35km upstream of the Hawkesbury River. Rapid aggradation occurred between 8000 and 6000 years BP and a sand bed river was established in the Macdonald Valley, its mouth prograding rapidly towards the Hawkesbury. Little is known about the character of the sand bed river during the +2 meter sea level highstand occurring between 5000 and 4000 BP. However, from 3000 to 1500 BP when sea level was consistently at +1 to +1.5m, major floodplain and levee-like structures, now virtually inactive, were established. The bed is inferred to have been elevated above its present day level and consequently intersected mean sea level (MSL) downstream of its present location. This is consistent with reported sea levels at +1 to +2m above present levels for the New South Wales coast at this time. From 1500 years BP, local sea level fell rapidly to its present level. Aggradation of the levee crests ceased and sedimentation along the valley became restricted to aggradation of an inset floodplain, within the pre-1500 BP deposits. The channel contracted and the sandy river bed incised. An equivalent and synchronous change in sedimentation style is observed along the Tuross River 400km south of the Macdonald, lending support to sea level variations being the factor driving this change. By 1850 AD, the bed dipped below MSL about 10km upstream of its inferred position prior to 1500 years BP. A series of large floods between 1949 and 1955 eroded significant volumes of sandy sediment from the Holocene deposits. The channel bed widened from between 25 and 50m width to ˜100m along

  19. Late Holocene sea-level rise in Tampa Bay: Integrated reconstruction using biomarkers, pollen, organic-walled dinoflagellate cysts, and diatoms

    NARCIS (Netherlands)

    Soelen, E.E. van; Lammertsma, E.I.; Cremer, H.; Donders, T.H.; Sangiorgi, F.; Brooks, G.R.; Larson, R.A.; Sinninghe Damsté, J.S.; Wagner-Cremer, F.; Reichart, G.J.

    2010-01-01

    A suite of organic geochemical, micropaleontological and palynological proxies was applied to sediments from Southwest Florida, to study the Holocene environmental changes associated with sea-level rise. Sediments were recovered from Hillsborough Bay, part of Tampa Bay, and studied using biomarkers,

  20. Early-to-middle Holocene sea-level fluctuations, coastal progradation and the Neolithic occupations in Yaojiang valley of southern Hangzhou bay, eastern China

    Science.gov (United States)

    Liu, Y.; Sun, Q.; Fan, D.; Chen, Z.

    2017-12-01

    The formation of Holocene coast in eastern China provided material base for the development of Neolithic civilizations. The coastal Yaojiang valley of south Hangzhou bay was one of the examples where the well-known Neolithic Hemudu Culture (HC) of Eastern China initiated. Here, we studied the early-to-middle Holocene environment changes in relation to sea-level fluctuations on the basis of a serial of sediment cores based on a set of new Accelerator Mass Spectrometry radiocarbon (AMS 14C) chronology. The result indicated that relative sea-level rose rapidly in the Yaojiang valley at the early Holocene, reaching its maximum at ca. 8000-7800 cal yr BP and then decelerated at ca. 7800-7500 cal yr BP. The alluvial plain in Yaojiang valley began to form at the foothills first and then grew towards the valley center accompanying with the sea-level stabilization after ca. 7500 cal yr BP. This progressive progradation of alluvial plain would attract the early arrivals of foragers to dwell at the foothills to engaging in rice farming after ca.7000 cal yr BP and starting the epic Hemudu Culture. The HC people then move down to the valley center as more land became available thanks to sediment aggregation and progradation. The rise and development of HC were closely associated with the sea-level induced landscape changes in Yaojiang valley at the early-middle Holocene, and the unstable hydraulic condition in the valley after 5000 cal yr BP could be accountable for the cultural termination.

  1. Stratigraphic response of salt marshes to slow rates of sea-level change

    Science.gov (United States)

    Daly, J.; Bell, T.

    2006-12-01

    Conventional models of salt-marsh development show an idealized spatial relationship between salt-marsh floral and foraminiferal zones, where the landward margin of the marsh gradually migrates inland in response to sea-level rise. This model predicts that transgression will result in persistent and possibly expanded salt marshes at the surface, depending on a variety of factors including sediment supply, hydrologic conditions, tidal range, and rate of sea-level rise. However, in areas with abundant sediment supply and slow rates of sea- level rise, the extent of back-barrier salt marshes may decline over time as the barrier-spits mature. Sea level around the northeast coast of Newfoundland is rising at a very slow rate during the late Holocene (flora. These transitions are interpreted to reflect the progradation of the spit, decreased tidal exchange in the back-barrier, and increased influence of freshwater streams discharging into the back-barrier setting. Decreased marine influence on the back-barrier environment leads to a floral and faunal shift associated with a regressive stratigraphy in an area experiencing sea-level rise. For studies of Holocene sea-level change requiring salt-marsh stratigraphic records, it is necessary to account for changing micro-environments to locate sites appropriate for study; salt marshes may play an important role in defining the record, but may not exist at the surface to guide investigation.

  2. Relative sea-level changes and glacio-isostatic adjustment on the Magdalen Islands archipelago (Atlantic Canada) from MIS 5 to the late Holocene

    Science.gov (United States)

    Rémillard, Audrey M.; St-Onge, Guillaume; Bernatchez, Pascal; Hétu, Bernard; Buylaert, Jan-Pieter; Murray, Andrew S.; Lajeunesse, Patrick

    2017-09-01

    The Magdalen Islands (Québec, Canada) in the centre of the Gulf of St. Lawrence are located in a strategic position for providing an overview of the relative sea-level (RSL) history of the Maritime Provinces of eastern Canada. Although data are available for the coastal terrestrial areas of the Maritimes, data from the Gulf are very scarce and both the RSL and glacio-isostatic adjustment (GIA) models extrapolate for this central region. This study provides new stratigraphic and chronological data from four outcrops and two coring sites on the Magdalen Islands. In addition to the five samples used mainly for age control purposes, nine new luminescence ages are presented. With these new data added to the available literature, a new RSL curve is reconstructed for the LGM to the late Holocene period and a partial curve is proposed for the interval between the late MIS 4 to the MIS 3. Data also indicate a few insights for the MIS 5 period. Results reveal that for the LGM to the late Holocene, the curve corresponds to the J-shaped curve scenario recognized in the literature. The RSL changes during this period are the result of glacio-isostatic rebound, migration and collapse of the peripheral forebulge, and eustatic sea-level changes. For the LGM to the early Holocene, glacio-isostatic depression curves displaying a few local differences are also proposed. For the late Holocene, the data constrain the curve between two types of indicators, i.e. marine and terrestrial, and indicate that the RSL has risen at least 3 m during the last two millennia. Sediments dated to the MIS 5 and the interval between the late MIS 4 and the MIS 3 illustrate that the GIA following the LGM also occurred for the MIS 5 interglacial and the MIS 3 interstadial. Finally, recent GIA models are discussed in light of the results of this paper.

  3. Holocene glacier variations and sea level change in Wahlenbergfjorden, Nordaustlandet, Svalbard

    Science.gov (United States)

    Schomacker, A.; Farnsworth, W. R.; Ingolfsson, O.; Allaart, L.; Håkansson, L.; Retelle, M.

    2017-12-01

    Here we present preliminary results on the Holocene glacier variations in Wahlenbergfjorden on Nordaustlandet, Svalbard. The reconstructions are based on lake sediment records from Lake Kl\\overbladvatna covering the last 9500 years. This lake captures meltwater from the Etonbreen glacier, a main outlet of the Austfonna ice cap, when the glacier extends further than present. Additionally, Kl\\overbladvatna is an isolation basin capturing the postglacial isolation from the marine to lacustrine environment due to glacioisostatic rebound. The chronology is based on radiocarbon dating of terrestrial and marine macrofossils. The lake sediment record also reveals that glacial meltwater exceeded the threshold into Lake Kl\\overbladvatna during the Little Ice Age as witnessed by glacial meltwater clay in the upper part of the sediment cores. In periods of less advanced glaciers, the lake sediment record is dominated by laminated clayey gyttja. Based on radiocarbon datings of driftwood, whalebone, and marine mollusc shells in raised beaches and marine deposits in Pallanderbukta, south Wahlenbergfjorden, we also present a new postglacial sea level curve from this region.

  4. Can molluscan assemblages give insights into Holocene environmental changes other than sea level rise? A case study from a macrotidal bay (Marennes-Oleron, France)

    OpenAIRE

    Poirier, Clement; Sauriau, Pierre-guy; Chaumillon, Eric; Allard, Jonathan

    2009-01-01

    During the Late Holocene, the rate of sea level rise decreased and climate changes, hydrodynamic processes or anthropogenic impacts became predominant parameters governing the sedimentary infill of estuarine environments. The aim of this study is to describe the response of past benthic mollusc communities to these forcing factors. Mollusc skeletal remains were sampled from three 8000, 5500 and 2600 year-long sedimentary records in the Marennes-Oleron Bay (Atlantic Coast, France), where envir...

  5. Postglacial relative sea level change at Fildes Peninsula, King George Island (West Antarctic

    Directory of Open Access Journals (Sweden)

    K. V. Polishchuk

    2016-01-01

    Full Text Available Analysis and integration of data obtained in our field and laboratory investigations of 2008–2012 together with results of previous paleogeographic studies were conducted to reveal parameters and factors of the post-glacial changes in the relative sea-level on the Fildes Peninsula and the King George Island. Results of dating of organic material taken from cross-sections of Quaternary deposits, data on morphology of marine landforms as well as on bottom sediments in lakes were used to construct a curve of changes in the relative sea-level.Our research has shown that the rapid rise of relative sea level in the area (since the beginning of the Holocene decelerated about 8000 years BP, achieving its maximum about 7000 years BP. This was followed by the fall of relative sea-level (the land elevation by 18–20  m in total, and it was characterized by relatively high rate of fall during periods of 6000– 5000 years BP, 4000–2500 years BP, and during the last 1500 years; the rate decreased in 5000–4000 years BP and 2500– 1600 years BP. The changes in relative sea level in this region were determined by the following factors: the eustatic component of the global changes in sea-level and, possibly, oscillations in the global sea level of another nature; local parameters of the Last glacial maximum; a course of the Peninsula deglaciation; regional physical characteristics of the Earth's crust and the mantle substances; local tectonic processes, including the isostatic rebound. Since the beginning of the Holocene up to about 7000 years BP, the main contribution to changes of the relative sea-level in this area was made by the global eustatic factor. The subsequent fall of the relative sea-level (elevation of the Peninsula surface proceeded under condition of reduced role of the eustatic factor and predominance of other factors.

  6. Holocene relative sea level variations at the spit system Feddet (Denmark) resolved by ground-penetrating radar and geomorphological data

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Bendixen, Mette; Clemmensen, Lars B

    Estimates of Holocene sea-level variations have been presented in a range of studies based on different approaches, including interpretation of internal beach ridge characteristics from ground-penetrating radar (GPR) and geomorphological data. We present GPR data and geomorphological observations...... of independent GPR and geomorphologic data collected across the recent and sub-recent beach ridge deposits. The data analyses include coastal topography, internal dips of beach ridge layers, and sea-level measurements. A clear change in characteristic layer dip is observed between beach face and upper shoreface...

  7. Sedimentary alkenone distributions reflect salinity changes in the Baltic Sea over the Holocene

    NARCIS (Netherlands)

    Warden, L.A.; van der Meer, M.T.J.; Moros, Matthias; Sinninghe Damsté, J.S.

    2016-01-01

    The Baltic Sea has had a complex salinity history since the last deglaciation. Here we show how distributions of alkenones and their δD values varied with past fluctuations in salinity in the Baltic Sea over the Holocene by examining a Holocene record (11.2–0.1 cal kyr BP) from the Arkona Basin.

  8. Sea level change

    Digital Repository Service at National Institute of Oceanography (India)

    Church, J.A.; Clark, P.U.; Cazenave, A.; Gregory, J.M.; Jevrejeva, S.; Levermann, A.; Merrifield, M.A.; Milne, G.A.; Nerem, R.S.; Nunn, P.D.; Payne, A.J.; Pfeffer, W.T.; Stammer, D.; Unnikrishnan, A.S.

    This chapter considers changes in global mean sea level, regional sea level, sea level extremes, and waves. Confidence in projections of global mean sea level rise has increased since the Fourth Assessment Report (AR4) because of the improved...

  9. Deglacial and Holocene sea-ice variability north of Iceland and response to ocean circulation changes

    Science.gov (United States)

    Xiao, Xiaotong; Zhao, Meixun; Knudsen, Karen Luise; Sha, Longbin; Eiríksson, Jón; Gudmundsdóttir, Esther; Jiang, Hui; Guo, Zhigang

    2017-08-01

    Sea-ice conditions on the North Icelandic shelf constitute a key component for the study of the climatic gradients between the Arctic and the North Atlantic Oceans at the Polar Front between the cold East Icelandic Current delivering Polar surface water and the relatively warm Irminger Current derived from the North Atlantic Current. The variability of sea ice contributes to heat reduction (albedo) and gas exchange between the ocean and the atmosphere, and further affects the deep-water formation. However, lack of long-term and high-resolution sea-ice records in the region hinders the understanding of palaeoceanographic change mechanisms during the last glacial-interglacial cycle. Here, we present a sea-ice record back to 15 ka (cal. ka BP) based on the sea-ice biomarker IP25, phytoplankton biomarker brassicasterol and terrestrial biomarker long-chain n-alkanols in piston core MD99-2272 from the North Icelandic shelf. During the Bølling/Allerød (14.7-12.9 ka), the North Icelandic shelf was characterized by extensive spring sea-ice cover linked to reduced flow of warm Atlantic Water and dominant Polar water influence, as well as strong meltwater input in the area. This pattern showed an anti-phase relationship with the ice-free/less ice conditions in marginal areas of the eastern Nordic Seas, where the Atlantic Water inflow was strong, and contributed to an enhanced deep-water formation. Prolonged sea-ice cover with occasional occurrence of seasonal sea ice prevailed during the Younger Dryas (12.9-11.7 ka) interrupted by a brief interval of enhanced Irminger Current and deposition of the Vedde Ash, as opposed to abruptly increased sea-ice conditions in the eastern Nordic Seas. The seasonal sea ice decreased gradually from the Younger Dryas to the onset of the Holocene corresponding to increasing insolation. Ice-free conditions and sea surface warming were observed for the Early Holocene, followed by expansion of sea ice during the Mid-Holocene.

  10. Sea-Level Change in the Russian Arctic Since the Last Glacial Maximum

    Science.gov (United States)

    Horton, B.; Baranskaya, A.; Khan, N.; Romanenko, F. A.

    2017-12-01

    Relative sea-level (RSL) databases that span the Last Glacial Maximum (LGM) to present have been used to infer changes in climate, regional ice sheet variations, the rate and geographic source of meltwater influx, and the rheological structure of the solid Earth. Here, we have produced a quality-controlled RSL database for the Russian Arctic since the LGM. The database contains 394 index points, which locate the position of RSL in time and space, and 244 limiting points, which constrain the minimum or maximum limit of former sea level. In the western part of the Russian Arctic (Barents and White seas,) RSL was driven by glacial isostatic adjustment (GIA) due to deglaciation of the Scandinavian ice sheet, which covered the Baltic crystalline shield at the LGM. RSL data from isolation basins show rapid RSL from 80-100 m at 11-12 ka BP to 15-25 m at 4-5 ka BP. In the Arctic Islands of Franz-Joseph Land and Novaya Zemlya, RSL data from dated driftwood in raised beaches show a gradual fall from 25-35 m at 9-10 ka BP to 5-10 m at 3 ka BP. In the Russian plain, situated at the margins of the formerly glaciated Baltic crystalline shield, RSL data from raised beaches and isolation basins show an early Holocene rise from less than -20 m at 9-11 ka BP before falling in the late Holocene, illustrating the complex interplay between ice-equivalent meltwater input and GIA. The Western Siberian Arctic (Yamal and Gydan Peninsulas, Beliy Island and islands of the Kara Sea) was not glaciated at the LGM. Sea-level data from marine and salt-marsh deposits show RSL rise at the beginning of the Holocene to a mid-Holocene highstand of 1-5 m at 5-1 ka BP. A similar, but more complex RSL pattern is shown for Eastern Siberia. RSL data from the Laptev Sea shelf show RSL at -40- -45 m and 11-14 ka BP. RSL data from the Lena Delta and Tiksi region have a highstand from 5 to 1 ka BP. The research is supported by RSF project 17-77-10130

  11. Sea-level proxies in Holocene raised beach ridge deposits (Greenland) revealed by ground-penetrating radar.

    Science.gov (United States)

    Nielsen, Lars; Bendixen, Mette; Kroon, Aart; Hede, Mikkel Ulfeldt; Clemmensen, Lars B; Weβling, Ronny; Elberling, Bo

    2017-04-19

    Identification of sea-level proxies is important for reconstruction of past sea-level variation. Methods for reconstructing Holocene relative sea-level curves are crucial for quantification of the impact of Greenland ice thickness variation on global sea level and vertical land movement. Arctic beach ridges constitute important potential archives of sea-level variation. However, their surface morphology may have undergone modification since deposition due to freezing/thawing processes and erosion, and their morphology may therefore not be trustworthy for sea-level reconstruction. Therefore, geophysical imaging is used to examine the internal structures of the beach ridges and to define a sea-level proxy unaffected by surface processes. The GPR reflections from study sites in West and South Greenland show deposition of beachface deposits and upper shoreface deposits; the contact between steeply dipping beachface reflections and less-dipping shoreface reflections is used as sea-level proxy. Numerous points are identified along GPR transects facilitating reconstruction of relative sea-level variation of hitherto unprecedented resolution. Erosional events and deformation caused by freezing/thawing processes are clearly delineated. The approach constitutes a solid base for reconstruction of relative sea-level curves affected by a well-defined vertical land movement history since the studied beach ridge systems represent long time intervals and only relatively small spatial extents.

  12. Holocene evolution of a drowned melt-water valley in the Danish Wadden Sea

    DEFF Research Database (Denmark)

    Pedersen, Jørn Bjarke Torp; Svinth, Steffen; Bartholdy, Jesper

    2009-01-01

    Cores from the salt marshes along the drowned melt-water valley of river Varde Å in the Danish Wadden Sea have been dated and analysed (litho- and biostratigraphically) to reconstruct the Holocene geomorphologic evolution and relative sea level history of the area. The analysed cores cover...... the total post-glacial transgression, and the reconstructed sea level curve represents the first unbroken curve of this kind from the Danish Wadden Sea, including all phases from the time where sea level first reached the Pleistocene substrate of the area. The sea level has been rising from - 12 m below...... the present level at c. 8400 cal yr BP, interrupted by two minor drops of sea level rise, and the Holocene sequence consists in most places of clay atop...

  13. Evolution of the Rømø barrier island in the Wadden Sea: Impacts of sea-level change on coastal morphodynamics

    DEFF Research Database (Denmark)

    Clemmensen, Lars B; Andersen, Thorbjørn Joest; Johannessen, Peter

    , and falling sea-level, whereas wash-over sedimentation was promoted during periods of rapid sea-level rise when shoreface, beach and coastal dune deposits were reworked. In contrast, lagoonal sedimentation has been relatively continuous and kept pace with the long-term Holocene sea-level rise. Our findings...

  14. The sensitivity of the Arctic sea ice to orbitally induced insolation changes: a study of the mid-Holocene Paleoclimate Modelling Intercomparison Project 2 and 3 simulations

    Directory of Open Access Journals (Sweden)

    M. Berger

    2013-04-01

    Full Text Available In the present work the Arctic sea ice in the mid-Holocene and the pre-industrial climates are analysed and compared on the basis of climate-model results from the Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2 and phase 3 (PMIP3. The PMIP3 models generally simulate smaller and thinner sea-ice extents than the PMIP2 models both for the pre-industrial and the mid-Holocene climate. Further, the PMIP2 and PMIP3 models all simulate a smaller and thinner Arctic summer sea-ice cover in the mid-Holocene than in the pre-industrial control climate. The PMIP3 models also simulate thinner winter sea ice than the PMIP2 models. The winter sea-ice extent response, i.e. the difference between the mid-Holocene and the pre-industrial climate, varies among both PMIP2 and PMIP3 models. Approximately one half of the models simulate a decrease in winter sea-ice extent and one half simulates an increase. The model-mean summer sea-ice extent is 11 % (21 % smaller in the mid-Holocene than in the pre-industrial climate simulations in the PMIP2 (PMIP3. In accordance with the simple model of Thorndike (1992, the sea-ice thickness response to the insolation change from the pre-industrial to the mid-Holocene is stronger in models with thicker ice in the pre-industrial climate simulation. Further, the analyses show that climate models for which the Arctic sea-ice responses to increasing atmospheric CO2 concentrations are similar may simulate rather different sea-ice responses to the change in solar forcing between the mid-Holocene and the pre-industrial. For two specific models, which are analysed in detail, this difference is found to be associated with differences in the simulated cloud fractions in the summer Arctic; in the model with a larger cloud fraction the effect of insolation change is muted. A sub-set of the mid-Holocene simulations in the PMIP ensemble exhibit open water off the north-eastern coast of Greenland in summer, which can provide a fetch

  15. Early to Middle Holocene sea level fluctuation, coastal progradation and the Neolithic occupation in the Yaojiang Valley of southern Hangzhou Bay, Eastern China

    Science.gov (United States)

    Liu, Yan; Sun, Qianli; Fan, Daidu; Dai, Bin; Ma, Fuwei; Xu, Lichen; Chen, Jing; Chen, Zhongyuan

    2018-06-01

    The Yaojiang Valley (YJV) of southern Hangzhou Bay was the birthplace of the well-known Hemudu Culture (HC), one of the representatives of Neolithic civilization in eastern China. To explore the magnitude of natural environmental effects on the HC trajectory, the palaeo-embayment setting of the YJV was studied in detail for the first time in terms of 3D Holocene strata supported by a series of new radiocarbon-dated cores. The results indicated that the local relative sea level rose rapidly during the Early Holocene in the YJV, reached its maximum flooding surface ca. 7900 cal yr BP, and then remained stable ca. 7900-7600 cal yr BP. Thereupon, an estuary stretching inland was first formed by marine transgression, and then, it was transformed to an alluvial-coastal plain by regressive progradation. The alluvial plain was initiated in the foothills and then spread towards the valley centre after sea level stabilization ca. 7600 cal yr BP. Accompanying these natural environmental changes, the earliest arrivals of foragers in the valley occurred no later than ca. 7000 cal yr BP. They engaged in rice farming and fostered the HC for approximately two millennia from ca. 7000-5000 cal yr BP as more lands developed from coastal progradation. The rise and development of the HC are closely associated with the sea level-induced landscape changes in the YJV in the Early-Middle Holocene, but the enigmatic exodus of the HC people after ca. 5000 cal yr BP is still contentious and possibly linked with the rapid waterlogging and deterioration of this setting in such a low-lying coastal plain as well as with associated social reasons.

  16. New high-resolution record of Holocene climate change in the Weddell Sea from combined biomarker analysis of the Patriot Hills blue ice area

    Science.gov (United States)

    Fogwill, Christopher; Turney, Chris; Baker, Andy; Ellis, Bethany; Cooper, Alan; Etheridge, David; Rubino, Mauro; Thornton, David; Fernando, Francisco; Bird, Michale; Munksgaard, Niels

    2017-04-01

    We report preliminary analysis of biomarkers (including dissolved organic matter (DOM) and DNA) from the Patriot Hills blue ice area (BIA), from the Ellsworth Mountains in the Weddell Sea Embayment. Preliminary isotopic and multiple gas analysis (CO2, CH4, N2O and CO) demonstrate that the Holocene comprises more than 50% of the 800m long BIA record, and in combination isotopic and biomarker analysis reveals a remarkable record of centennial variability through the Holocene in this sector of the Weddell Sea. Analysis using a Horiba Aqualog - which measures the fluorescence of DOM by producing a map of the fluorescence through an excitation-emission matrix (EEM) - identifies the presence of two marine protein-like components in both modern snow pit samples and within the Holocene part of Patriot Hills BIA transect. Intriguingly, the modern seasonal trends in DOM, recorded in contemporary snow pits, have relatively low signals compared to those recorded in the mid-Holocene record, suggesting a reduction in DOM signal in contemporary times. Given that the δD excess data suggests the source of precipitation has remained constant through the Holocene, the biomarker signal must relate to multi-year marine productivity signals from the Weddell Sea. The marked variability in DOM between the mid-Holocene and contemporary times can only relate to periods of sustained, enhanced biological productivity in the Weddell Sea associated with shifts in Southern Annular Mode, sea ice variability, changes in ventilation or polynya activity. Here we discuss the possible drivers of these changes and describe how this approach at this BIA could benefit conventional ice core records regionally.

  17. Palaeoenvironmental Evolution of Cenote Aktun Ha (Carwash) on the Yucatan Peninsula, Mexico and its Response to Holocene Sea-Level Rise

    Science.gov (United States)

    Gabriel, J. J.; Reinhardt, E. G.; Peros, M. C.; Davidson, D. E.; van Hengstum, P. J.; Beddows, P. A.

    2008-12-01

    A 61-cm core was obtained from 4 metres below the water table in Cenote Aktun Ha, on the Yucatan Peninsula, Mexico. The cenote is 8.6 km from the Caribbean coast and its formation and evolution have been largely affected by sea-level change. The base of the core dates to 6940 - 6740 cal yr BP and overlying sediments were deposited rapidly over the subsequent ~200 years. The pollen record shows that the cenote evolved from a marsh dominated by red mangrove (Rhizophora mangle) and fern (Polypodiaceae) to an open-water system. These vegetation changes were controlled by water level and salinity and are thus useful indicators of past sea level. At the base, the d13C isotopic ratios reveal the influence of terrestrial vegetation (-29‰), but shift to more negative values up-core (-33‰), indicating an influence from particulate matter in the flooded cenote pool. Although microfossil populations were nearly absent through most of the core, the microfossil assemblage in the upper 6 cm of the core is dominated by juvenile Ammonia tepida and the thecamoebian genus Centropyxis. These populations indicate open-water conditions in the cenote and a major environmental shift around 6600 cal yr BP, which is related to sea-level rise in the Caribbean basin. These data fit well with previously established sea-level curves for the Caribbean Sea. Our reconstruction of the environmental history of Cenote Aktun Ha helps elucidate the floral and hydrological history of the region, and highlights the utility of cenote sediments for studying the Holocene sea-level history of the Caribbean Sea.

  18. History of Aral Sea level variability and current scientific debates

    Science.gov (United States)

    Cretaux, Jean-François; Letolle, René; Bergé-Nguyen, Muriel

    2013-11-01

    The Aral Sea has shrunk drastically over the past 50 years, largely due to water abstraction from the Amu Darya and Syr Darya rivers for land irrigation. Over a longer timescale, Holocene palaeolimnological reconstruction of variability in water levels of the Aral Sea since 11,700 BP indicates a long history of alternating phases of regression and transgression, which have been attributed variously to climate, tectonic and anthropogenic forcing. The hydrological history of the Aral Sea has been investigated by application of a variety of scientific approaches, including archaeology, palaeolimnological palaeoclimate reconstruction, geophysics, sedimentology, and more recently, space science. Many issues concerning lake level variability over the Holocene and more recent timescales, and the processes that drive the changes, are still a matter for active debate. Our aim in this article is to review the current debates regarding key issues surrounding the causes and magnitude of Aral Sea level variability on a variety of timescales from months to thousands of years. Many researchers have shown that the main driving force of Aral Sea regressions and transgressions is climate change, while other authors have argued that anthropogenic forcing is the main cause of Aral Sea water level variations over the Holocene. Particular emphasis is made on contributions from satellite remote sensing data in order to improve our understanding of the influence of groundwater on the current hydrological water budget of the Aral Sea since 2005. Over this period of time, water balance computation has been performed and has shown that the underground water inflow to the Aral Sea is close to zero with an uncertainty of 3 km3/year.

  19. Late Holocene sea ice conditions in Herald Canyon, Chukchi Sea

    Science.gov (United States)

    Pearce, C.; O'Regan, M.; Rattray, J. E.; Hutchinson, D. K.; Cronin, T. M.; Gemery, L.; Barrientos, N.; Coxall, H.; Smittenberg, R.; Semiletov, I. P.; Jakobsson, M.

    2017-12-01

    Sea ice in the Arctic Ocean has been in steady decline in recent decades and, based on satellite data, the retreat is most pronounced in the Chukchi and Beaufort seas. Historical observations suggest that the recent changes were unprecedented during the last 150 years, but for a longer time perspective, we rely on the geological record. For this study, we analyzed sediment samples from two piston cores from Herald Canyon in the Chukchi Sea, collected during the 2014 SWERUS-C3 Arctic Ocean Expedition. The Herald Canyon is a local depression across the Chukchi Shelf, and acts as one of the main pathways for Pacific Water to the Arctic Ocean after entering through the narrow and shallow Bering Strait. The study site lies at the modern-day seasonal sea ice minimum edge, and is thus an ideal location for the reconstruction of past sea ice variability. Both sediment cores contain late Holocene deposits characterized by high sediment accumulation rates (100-300 cm/kyr). Core 2-PC1 from the shallow canyon flank (57 m water depth) is 8 meter long and extends back to 4200 cal yrs BP, while the upper 3 meters of Core 4-PC1 from the central canyon (120 mwd) cover the last 3000 years. The chronologies of the cores are based on radiocarbon dates and the 3.6 ka Aniakchak CFE II tephra, which is used as an absolute age marker to calculate the marine radiocarbon reservoir age. Analysis of biomarkers for sea ice and surface water productivity indicate stable sea ice conditions throughout the entire late Holocene, ending with an abrupt increase of phytoplankton sterols in the very top of both sediment sequences. The shift is accompanied by a sudden increase in coarse sediments (> 125 µm) and a minor change in δ13Corg. We interpret this transition in the top sediments as a community turnover in primary producers from sea ice to open water biota. Most importantly, our results indicate that the ongoing rapid ice retreat in the Chukchi Sea of recent decades was unprecedented during the

  20. Holocene environmental change and archaeology, Yangtze River Valley, China: Review and prospects

    Directory of Open Access Journals (Sweden)

    Li Wu

    2012-11-01

    Full Text Available Holocene environmental change and environmental archaeology are important components of an international project studying the human-earth interaction system. This paper reviews the progress of Holocene environmental change and environmental archaeology research in the Yangtze River Valley over the last three decades, that includes the evolution of large freshwater lakes, Holocene transgression and sea-level changes, Holocene climate change and East Asian monsoon variation, relationship between the rise and fall of primitive civilizations and environmental changes, cultural interruptions and palaeoflood events, as well as relationship between the origin of agriculture and climate change. These research components are underpinned by the dating of lacustrine sediments, stalagmites and peat to establish a chronology of regional environmental and cultural evolution. Interdisciplinary and other environment proxy indicators need to be used in comparative studies of archaeological site formation and natural sedimentary environment in the upper, middle and lower reaches of the Yangtze River Valley. Modern technology such as remote sensing, molecular bioarchaeology, and virtual reality, should be integrated with currently used dating, geochemical, sedimentological, and palaeobotanical methods of analysis in environmental archaeology macro- and micro-studies, so as to provide a greater comprehensive insight into Holocene environmental and cultural interaction and change in the Yangtze River Valley area.

  1. Holocene coastal dune development and environmental changes in Helis area (NW Peloponnese, Greece

    Directory of Open Access Journals (Sweden)

    L. STAMATOPOULOS

    2017-12-01

    Full Text Available The coastal area of western Peloponnese is characterized by Pleistocene and Holocene marine deposits. The study area shows the effects of different phases of coastal morphology evolution and is located along a wave-dominated and microtidal coast in the northwestern Peloponnese, 40 km southwest of Patras city. Three significant morphogenetic phases occurred during the Holocene. The first was radiometrically aged from 7000 to 3810 years BP, marking the end of the rapid postglacial transgression. The second, between 3810 and 1400 years BP, was characterized by high rates of sedimentation, possibly because of the proximity of the mouth of the Peneus River, and resulted in the accumulation of predominantly fluvial sediments. During the third and younger phase, from 1400 years BP to the present, landward migration of the coast and deposition of aeolian sands occurred. Archaeological and morphological evidences suggest that this last phase should be related to a low sea-level stand followed by a slow sea-level rise, up to the present-day position and by humid-temperate climate. The collected data concerning the Holocene coastal dune belts, suggest that main phases of dune development could be related to the effects of sea-level changes, climatic conditions, and in a subordinate way, to human activity.

  2. Middle-Holocene sea-level fluctuations interrupted the developing Hemudu culture in the lower Yangtze River, China

    Science.gov (United States)

    He, Keyang; Lu, Houyuan; Zheng, Yunfei; Zhang, Jianping; Xu, Deke; Huan, Xiujia; Wang, Jiehua; Lei, Shao

    2018-05-01

    The eastern coastal zone of China is densely populated and widely recognized as a center of rice domestication, which has undergone dramatic sea-level fluctuation during the Holocene epoch. Hemudu culture is distributed mainly in the eastern coastal area and was once presumed as a mature agricultural economy based on rice, making it an ideal case for examining the remarkable human-environment interaction in the Lower Yangtze River. Though numerous studies have been conducted on the cultural evolution, ecological environment, and rice domestication of Hemudu culture, the impact of sea-level fluctuation on human settlement and food production remains controversial. In this study, we report high-resolution pollen, phytolith, and diatom records, and accurately measured elevation from the Yushan site, which is the closest site of Hemudu culture to the modern coastline. Based on the data gathered, we suggest that the Hemudu culture and subsequent Liangzhu culture developed in the context of regression and were interrupted by two transgressions that occurred during 6300-5600 BP and 5000-4500 BP. The regional ecological environment of the Yushan site alternated between intertidal mudflat and freshwater wetlands induced by sea-level fluctuations in the mid-late Holocene. Though rice was cultivated in the wetland as early as 6700 BP, this cultivation was subsequently discontinued due to the transgression; thus, full domestication of rice did not occur until 5600 BP in this region. Comprehensive analysis of multiple proxies in this study promote the understanding of the relationship between environmental evolution, cultural interruption, and rice domestication.

  3. Impact of sea-level rise on Everglades carbon storage capacity in the Holocene

    Science.gov (United States)

    Jones, M.; Bernhardt, C. E.; Wingard, G. L. L.; Keller, K.; Stackhouse, B.; Landacre, B.

    2017-12-01

    Sea-level rise (SLR) and climate have driven environmental changes in South Florida over time. Florida Bay, a shallow carbonate bay located to the south of the Florida Peninsula, contains carbonate islands and mudbanks that formed over the last few thousand years and once comprised the freshwater Everglades. The islands, often ringed with mangroves, provide wildlife habitat, physical barriers to storm surge, tidal flux, and wave development along South Florida's coastline. Because most of South Florida is only 1-2 m above mean sea level, and IPCC AR5 projections of 0.26 to 0.98 m of SLR by 2100, vertical accommodation space could outpace sediment accretion in the southern freshwater Everglades and Florida Bay islands, impacting carbon (C) storage, as well as wildlife habitat and the ability to protect shorelines from coastal storms. We analyzed sediment cores that reached the Plio-Pleistocene limestone bedrock from four islands in Florida Bay to determine how floral and faunal communities and source C change in response to Holocene sea level transgression. We used pollen and mollusk assemblages, δ13C, and C/N ratios, along with radiometric dating, bulk density, and organic C content to calculate changes in C accumulation rates (CAR) over the last 4 ka, as deposition transitioned from freshwater peat to estuarine carbonate mud, to mangrove peat and ultimately to the hyper-saline playa-like carbonate sediments deposited today. Results show that CAR are more than twice as high in the basal freshwater Everglades peat than in the overlying estuarine sediments and slightly greater than the short-lived period of Rhizophora (red mangrove) peat accumulation. Avicennia (black mangrove) and playa-like environments have similar CAR as the estuarine carbonate mud and hypersaline carbonate sediments but accretion rates are less than the current rate of SLR. These results suggest that with current rates of accretion and SLR, these islands could disappear in <200 years, and the C

  4. Barrier response to Holocene sea-level rise

    DEFF Research Database (Denmark)

    Pejrup, Morten; Andersen, Thorbjørn Joest; Johannessen, Peter N

    Normally it is believed that sea-level rise causes coastal barrier retreat. However, sea-level is only one of the parameters determining the long term coastal development of barrier coasts. Sediment supply is an equally important determinant and may overshadow the effects of sea-level rise....... Conceptually this has been known for a long time but for the first time we can show the relative effect of these two parameters. We have studied three neighboring barrier islands in the Wadden Sea, and described their 3D morphological evolution during the last 8000 years. It appears that the barrier islands...... a much stronger component of sea-level control. The distance between the islands is only 50 km, and therefore our study shows that prediction of barrier development during a period of rising sea level may be more complicated than formerly believed....

  5. Holocene vegetational and coastal environmental changes from the Lago Crispim record in northeastern Pará State, eastern Amazonia.

    Science.gov (United States)

    Behling, H; Lima da Costa, M

    2001-04-01

    Vegetational and coastal environmental changes have been interpreted from a 600cm long and 764014C yr B.P. old sediment core from Lago Crispim located in the northeastern Pará State in northern Brazil. The radiocarbon dated sediment core was studied by multi-element geochemistry, pollen and charcoal analysis.Holocene Atlantic sea-level rise caused an elevation of local water table, which allowed the formation of organic deposits in a probably former inter-dune valley. Dense, diverse and tall Amazon rain forest, and some restinga (coastal vegetation) covered the study area at the beginning of the record at 764014C yr B.P. Mangrove vegetation developed along rivers close to the core site at that time. Subsequent decrease in less mangrove vegetation near the study site indicates a sea-level regression, beginning since around 700014C yr B.P. Lower sea-levels probably favoured the formation of a local Mauritia/Mauritiella palm swamp at 662014C yr B.P. Oscillations of higher and lower sea-level stands probably changed the size of the local palm swamp area several times between 6620 and 363014C yr B.P. Sea-level transgression at around 363014C yr B.P., caused marked coastal environmental changes: the development of mangroves near the site, the replacement of the local palm swamp by a Cyperaceae swamp, the substitution of the surrounding former Amazon rain forest and some restinga vegetation mainly by salt marshes. High amount carbonised particles suggest a strong human impact by burning on the coastal ecosystems during this late Holocene period.Highest concentrations of NaCl and also Ca, Mg and K in the upper sediment core indicate that the Atlantic was close during the late Holocene period. The core site, which is today 500m from the coastline and only 1-2m above modern sea-level, was apparently never reached by marine excursions during the Holocene.Less representation of mangrove since ca. 184014C yr B.P., may be related due to a slightly lower sea-level or to human

  6. Development of small carbonate banks on the south Florida platform margin: Response to sea level and climate change

    Science.gov (United States)

    Mallinson, David J.; Hine, Albert C.; Hallock, Pamela; Locker, Stanley D.; Shinn, Eugene; Naar, David; Donahue, Brian; Weaver, Douglas C.

    2003-01-01

    Geophysical and coring data from the Dry Tortugas, Tortugas Bank, and Riley’s Hump on the southwest Florida margin reveal the stratigraphic framework and growth history of these carbonate banks. The Holocene reefs of the Dry Tortugas and Tortugas Bank are approximately 14 and 10 m thick, respectively, and are situated upon Pleistocene reefal edifices. Tortugas Bank consists of the oldest Holocene corals in the Florida Keys with earliest coral recruitment occurring at ∼9.6 cal ka. Growth curves for the Tortugas Bank reveal slow growth (demise at ∼4.2 cal ka. Coral reef development at the Dry Tortugas began at ∼6.4 cal ka. Aggradation at the Dry Tortugas was linear, and rapid (∼3.7 mm/yr) and kept pace with sea-level change. The increase in aggradation rate of Tortugas Bank at 6.2 cal ka is attributed to the growth of the Dry Tortugas reefs, which formed a barrier to inimical shelf water. Termination of shallow (<15 m below sea level) reef growth at Tortugas Bank at ∼4.2 cal ka is attributed to paleoclimate change in the North American interior that increased precipitation and fluvial discharge. Reef growth rates and characteristics are related to the rate of sea-level rise relative to the position of the reef on the shelf margin, and are additionally modified by hydrographic conditions related to climate change.

  7. On the interpretation of millennium-scale level variations of the Black Sea during the first quarter of the Holocene

    Science.gov (United States)

    Kislov, Alexander

    2016-04-01

    Introduction. During the first quarter of the Holocene, the Black Sea (BS) experienced large changes: amid the gradually rising water surface, Black Sea level (BSL) fluctuations occurred. We calculated based on records (e.g., Balabanov, 2007) that the standard deviation is ˜3.5 ÷ 5 m. Their typical duration was ˜1000 years. Time of occurrence of positive and negative anomalies of the BS is different in different reconstructions. The source of these discrepancies could be tectonically induced vertical motions. Before ˜7 ka BP the BSL was higher than the level of the World Ocean. The rising BS spilled over a rocky sill at the Bosphorus (Chepalyga, 2007). It is clear that if the water discharge were quite large, the long-term BSL anomalies could not be. This study focuses on the quantification of this concept. Methodology. I use the equation of the water balance of the BS in term of the annual averaged level anomalies. Time scales of the BSL fluctuations were determined based on the BS basin morphology and averaged volumes of rivers runoff and water discharge via the Bosphorus Sill. The short-term (1-2 year) contribution (like random white noise) to level changes are due to variations of river runoff and precipitation mines evaporation. From this perspective, the water balance equation is represented as a stochastic Langevin equation (Kislov, 2015). In another case, the BSL anomaly could be destructed due to relation "BSL anomaly - value of water discharge via the Bosphorus Sill" which acts as a negative feedback. Results. To quantify the parameters, I use the present day information about hydrological regime of the BS. It should not lead to serious errors, because the first and last quarters of the Holocene exhibit similarity in their hydroclimatic regimes (Panin, Matlakhova, 2014). As well, the paleohydrological data about dynamics of the Dnieper River runoff was used (Swetc, 1978). It was found that the time scale of the BSL fluctuations due to water discharge

  8. People, lakes and seashores: Studies from the Baltic Sea basin and adjacent areas in the early and Mid-Holocene

    Science.gov (United States)

    Groß, Daniel; Zander, Annabell; Boethius, Adam; Dreibrodt, Stefan; Grøn, Ole; Hansson, Anton; Jessen, Catherine; Koivisto, Satu; Larsson, Lars; Lübke, Harald; Nilsson, Björn

    2018-04-01

    During the Early and Mid-Holocene significant changes in the ecology and socio-cultural spheres occurred around the Baltic Sea. Because of the underlying climatic changes and thus environmental alterations, the area was the scene for various cultural developments during the period under investigation. In the course of the melting of the glaciers at the end of the last Ice Age, isostatic and eustatic movements caused continual changes to the Baltic Sea basin. Changes in water level, however, affected not only the Early and Mid-Holocene coastlines, but also the whole Baltic Sea drainage system, including large lakes, rivers and watersheds in the hinterland were also dramatically impacted by these ecological changes. Prehistoric people were thus affected by changes in resource availability and reduction or enlargement of their territories, respectively. In order to evaluate the impact of changes in the water and land networks on the environment, resource availability, and human behaviour, and to reconstruct human responses to these changes, we pursue an interdisciplinary approach connecting environmental and archaeological research highlighted through different case studies.

  9. Eustatic and Relative Sea Level Changes

    NARCIS (Netherlands)

    Rovere, A.; Stocchi, P.; Vacchi, M.

    2016-01-01

    Sea level changes can be driven by either variationsin the masses or volume of the oceans, or bychanges of the land with respect to the sea surface. Inthe first case, a sea level change is defined ‘eustatic’;otherwise, it is defined ‘relative’. Several techniques canbe used to observe changes in sea

  10. Diatom-inferred hydrological changes and Holocene geomorphic transitioning of Africa's largest estuarine system, Lake St Lucia

    Science.gov (United States)

    Gomes, M.; Humphries, M. S.; Kirsten, K. L.; Green, A. N.; Finch, J. M.; de Lecea, A. M.

    2017-06-01

    The diverse lagoons and coastal lakes along the east coast of South Africa occupy incised valleys that were flooded during the rise and subsequent stabilisation of relative sea-level during the Holocene. Sedimentary deposits contained within these waterbodies provide an opportunity to investigate complex hydrological and sedimentological processes, and examine sea-level controls governing system geomorphic evolution. In this paper, we combine diatom and sulfur isotope analyses from two sediment cores extracted from the northern sub-basins of Lake St Lucia, a large shallow estuarine lake that is today largely isolated from direct ocean influence behind a Holocene-Pleistocene barrier complex. Analyses allow the reconstruction of hydrological changes associated with the geomorphic development of the system over the mid-to late Holocene. The sedimentary sequences indicate that St Lucia was a shallow, partially enclosed estuary/embayment dominated by strong tidal flows prior to ∼6200 cal. BP. Infilling was initiated when sea-level rise slowed and stabilised around present day levels, resulting in the accumulation of fine-grained sediment behind an emergent proto-barrier. Diatom assemblages, dominated by marine benthic and epiphytic species, reveal a system structured by marine water influx and characterised by marsh and tidal flat habitats until ∼4550 cal. BP. A shift in the biological community at ∼4550 cal. BP is linked to the development of a back-barrier water body that supported a brackish community. Marine planktonics and enrichments in δ34S suggest recurrent, large-scale barrier inundation events during this time, coincident with a mid-Holocene sea-level highstand. Periodic marine incursions associated with episodes of enhanced storminess and overwash remained prevalent until ∼1200 cal. BP, when further barrier construction ultimately isolated the northern basins from the ocean. This study provides the first reconstruction of the palaeohydrological

  11. Paleohydrology reconstruction and Holocene climate variability in the South Adriatic Sea

    Directory of Open Access Journals (Sweden)

    G. Siani

    2013-02-01

    Full Text Available Holocene paleohydrology reconstruction is derived combining planktonic and benthic stable oxygen and carbon isotopes, sea surface temperatures (SSTs and oxygen isotope composition of seawater (δ18Ow from a high sedimentation core collected in the South Adriatic Sea (SAS. Core chronology is based on 10 AMS 14C measures on planktonic foraminifera and tephra layers. Results reveal two contrasted paleohydrological periods that reflect (i a marked lowering of δ18Ow/salinity during the early to mid-Holocene (11.5 ka to 6.3 ka, including the two-step sapropel S1 deposition, followed during the mid- to upper Holocene by (ii a prevailing period of increased salinity and enhanced arid conditions in the South Adriatic Basin. Superimposed on these trends, short-term centennial-scale hydrological events punctuated the Holocene period in the SAS. During the early to mid-Holocene, two main SST coolings together with prominent δ18Ow/salinity lowering delineate the sapropel S1 interruption and the post-sapropel phase between 7.3 to 6.3 ka. After 6 ka, centennial-scale δ18Ow and G. bulloides δ13C lowering, mostly centered between 3 to 0.6 ka, reflect short-term hydrological changes related to more intensive runoff of the Po and/or Apennine rivers. These short-term events, even of lesser amplitude compared to the early to mid-Holocene period, may have induced a lowering of sea surface density and consequently reduced and/or inhibited the formation of deep bottom waters in the SAS. Comparison of the emerging centennial- to millennial-scale hydrological record with previous climatic records from the central Mediterranean area and north of the Alps reveal possible synchronicities (within the radiocarbon-dating uncertainty between phases of lower salinity in the SAS and periods of wetter climatic conditions around the north-central Adriatic Sea. Finally, wavelet analyses provide new clues about the potential origin of climate variability in the SAS, confirming

  12. Sensitivity of sediment magnetic records to climate change during Holocene for the northern South China Sea

    Science.gov (United States)

    Ouyang, Tingping; Li, Mingkun; Zhao, Xiang; Zhu, Zhaoyu; Tian, Chengjing; Qiu, Yan; Peng, Xuechao; Hu, Qiao

    2016-05-01

    Magnetic property has been proved to be a sensitive proxy to climate change for both terrestrial and marine sediments. Based on the schedule frame established by AMS 14C dating of foraminifera, detail magnetic analyses were performed for core PC24 sediments at sampling intervals of 2 cm to discuss magnetic sensitivity of marine sediment to climate during Holocene for the northern South China Sea. The results indicated that: 1) Concentration dependent magnetic parameters are positive corresponding to variation of temperature. The frequency dependent susceptibility coefficient basically reflected the variation in humidity; 2) XARM/SIRM was more sensitive to detrital magnetite particles and SIRM/X was more effective to biogenic magnetite particles. Variations of XARM/SIRM and SIRM/X are corresponding to precipitation and temperature, respectively; 3) the Holocene Megathermal in the study area was identified as 7.5-3.4 cal. ka BP. The warmest stage of Holocene for the study area should be during 6.1 to 3.9 cal. ka BP; 4) The 8 ka cold event was characterized as cold and dry during 8.55 to 8.25 cal. ka BP; 5) During early and middle Holocene, the climate combinations were warm dry and cold wet. It turned to warm and wet after 2.7 cal. ka BP.

  13. Sensitivity of sediment magnetic records to climate change during Holocene for the northern South China Sea

    Directory of Open Access Journals (Sweden)

    Tingping eOuyang

    2016-05-01

    Full Text Available Magnetic property has been proved to be a sensitive proxy to climate change for both terrestrial and marine sediments. Based on the schedule frame established by AMS 14C dating of foraminifera, detail magnetic analyses were performed for core PC24 sediments at sampling intervals of 2 cm to discuss magnetic sensitivity of marine sediment to climate during Holocene for the northern South China Sea. The results indicated that: 1 Concentration dependent magnetic parameters are positive corresponding to variation of temperature. The frequency dependent susceptibility coefficient basically reflected the variation in humidity; 2 XARM/SIRM was more sensitive to detrital magnetite particles and SIRM/X was more effective to biogenic magnetite particles. Variations of XARM/SIRM and SIRM/X are corresponding to precipitation and temperature, respectively; 3 the Holocene Megathermal in the study area was identified as 7.5-3.4 cal. ka BP. The warmest stage of Holocene for the study area should be during 6.1 to 3.9 cal. ka BP; 4 The 8 ka cold event was characterized as cold and dry during 8.55 to 8.25 cal. ka BP; 5 During early and middle Holocene, the climate combinations were warm dry and cold wet. It turned to warm and wet after 2.7 cal. ka BP.

  14. Dynamics of marsh-mangrove ecotone since the mid-Holocene: A palynological study of mangrove encroachment and sea level rise in the Shark River Estuary, Florida.

    Science.gov (United States)

    Yao, Qiang; Liu, Kam-Biu

    2017-01-01

    Sea level rise and the associated inland shift of the marsh-mangrove ecotone in south Florida have raised many scientific and management concerns in recent years. Holocene paleoecological records can provide an important baseline to shed light on the long-term dynamics of vegetation changes across this ecotone in the past, which is needed to predict the future. In this study, we present palynological, X-ray fluorescence, and loss-on ignition data from four sedimentary cores recovered from a 20-km marine-to-freshwater transect along the Shark River Estuary, southwest Everglades, to document the patterns and processes of coastal vegetation changes in response to sea level rise since the mid-Holocene. Our record indicates that freshwater marsh progressively replaced marl prairies at the Shark River Estuary between 5700 and 4400 cal yr BP. As marine transgression continued, marine influence reached the threshold necessary for mangroves to establish at the current mouth of the Shark River Slough at 3800 cal yr BP. During the next 3000 years, although sea level rise in the Western North Atlantic slowed down to 0.4 mm/yr, a spatial and temporal gradient was evident as the marsh-mangrove ecotone shifted inland by 20 km from 3800 to 800 cal yr BP, accompanied by a gradual landward replacement of freshwater marsh by mangrove forest. If sea level continues to rise at 2.33 mm/yr in the 21st century in south Florida, it is possible that marine influence will reach the threshold for mangroves to establish in the central Everglades, and we could expect a much more aggressive mangrove encroachment toward the northern and interior parts of south Florida in the next few centuries.

  15. Neoglacial Antarctic sea-ice expansion driven by mid-Holocene retreat of the Ross Ice Shelf.

    Science.gov (United States)

    Bendle, J. A.; Newton, K.; Mckay, R. M.; Crosta, X.; Etourneau, J.; Anya, A. B.; Seki, O.; Golledge, N. R.; Bertler, N. A. N.; Willmott, V.; Schouten, S.; Riesselman, C. R.; Masse, G.; Dunbar, R. B.

    2017-12-01

    Recent decades have seen expanding Antarctic sea-ice coverage, coeval with thinning West Antarctic Ice Sheet (WAIS) ice shelves and the rapid freshening of surface and bottom waters along the Antarctic margin. The mid-Holocene Neoglacial transition represents the last comparable baseline shift in sea-ice behaviour. The drivers and feedbacks involved in both the recent and Holocene events are poorly understood and characterised by large proxy-model mismatches. We present new records of compound specific fatty acid isotope analyses (δ2H-FA), highly-branched isoprenoid alkenes (HBIs) TEX86L temperatures, grain-size, mass accumulations rates (MARs) and image analyses from a 171m Holocene sediment sequence from Site U1357 (IODP leg 318). In combination with published records we reconstruct Holocene changes in glacial meltwater, sedimentary inputs and sea-ice. The early Holocene (11 to 10 ka) is characterised by large fluctuations in inputs of deglacial meltwater and sediments and seismic evidence of downlapping material from the south, suggesting a dominating influence from glacial retreat of the local outlet glaciers. From 10 to 8 ka there is decreasing meltwater inputs, an onlapping drift and advection of material from the east. After ca. 8 ka positively correlated δ2H-FA and MARs infer that pulses of glacial melt correlate to stronger easterly currents, driving erosion of material from upstream banks and that the Ross Ice Shelf (RIS) becomes a major influence. A large mid-Holocene meltwater pulse (preceded by warming TEX86L temperatures) is evident between ca. 6 to 4.5 ka, culminating in a rapid and permanent increase in sea-ice from 4.5 ka. This is coeval with cosmogenic nuclide evidence for a rapid thinning of the Antarctic ice sheet during the mid-Holocene (Hein et al., 2016). We suggest this represents a final major pulse of deglaciation from the Ross Ice Shelf, which initiates the Neoglacial, driving cool surface waters along the coast and greater sea

  16. Causes for contemporary regional sea level changes.

    Science.gov (United States)

    Stammer, Detlef; Cazenave, Anny; Ponte, Rui M; Tamisiea, Mark E

    2013-01-01

    Regional sea level changes can deviate substantially from those of the global mean, can vary on a broad range of timescales, and in some regions can even lead to a reversal of long-term global mean sea level trends. The underlying causes are associated with dynamic variations in the ocean circulation as part of climate modes of variability and with an isostatic adjustment of Earth's crust to past and ongoing changes in polar ice masses and continental water storage. Relative to the coastline, sea level is also affected by processes such as earthquakes and anthropogenically induced subsidence. Present-day regional sea level changes appear to be caused primarily by natural climate variability. However, the imprint of anthropogenic effects on regional sea level-whether due to changes in the atmospheric forcing or to mass variations in the system-will grow with time as climate change progresses, and toward the end of the twenty-first century, regional sea level patterns will be a superposition of climate variability modes and natural and anthropogenically induced static sea level patterns. Attribution and predictions of ongoing and future sea level changes require an expanded and sustained climate observing system.

  17. Holocene vegetation and climate changes in the central Mediterranean inferred from a high-resolution marine pollen record (Adriatic Sea

    Directory of Open Access Journals (Sweden)

    N. Combourieu-Nebout

    2013-09-01

    Full Text Available The high-resolution multiproxy study of the Adriatic marine core MD 90-917 provides new insights to reconstruct vegetation and regional climate changes over the southcentral Mediterranean during the Younger Dryas (YD and Holocene. Pollen records show the rapid forest colonization of the Italian and Balkan borderlands and the gradual installation of the Mediterranean association during the Holocene. Quantitative estimates based on pollen data provide Holocene precipitations and temperatures in the Adriatic Sea using a multi-method approach. Clay mineral ratios from the same core reflect the relative contributions of riverine (illite and smectite and eolian (kaolinite contributions to the site, and thus act as an additional proxy with which to evaluate precipitation changes in the Holocene. Vegetation climate reconstructions show the response to the Preboreal oscillation (PBO, most likely driven by changes in temperature and seasonal precipitation, which is linked to increasing river inputs from Adriatic rivers recorded by increase in clay mineral contribution to marine sediments. Pollen-inferred temperature declines during the early–mid Holocene, then increases during the mid–late Holocene, similar to southwestern Mediterranean climatic patterns during the Holocene. Several short vegetation and climatic events appear in the record, indicating the sensitivity of vegetation in the region to millennial-scale variability. Reconstructed summer precipitation shows a regional maximum (170–200 mm between 8000 and 7000 similar to the general pattern across southern Europe. Two important shifts in vegetation occur at 7700 cal yr BP (calendar years before present and between 7500 and 7000 cal yr BP and are correlated with increased river inputs around the Adriatic Basin respectively from the northern (7700 event and from the central Adriatic borderlands (7500–7000 event. During the mid-Holocene, the wet summers lead to permanent moisture all year

  18. Sea Level Changes: Determination and Effects

    Science.gov (United States)

    Woodworth, P. L.; Pugh, D. T.; DeRonde, J. G.; Warrick, R. G.; Hannah, J.

    The measurement of sea level is of fundamental importance to a wide range of research in climatology, oceanography, geology and geodesy. This volume attempts to cover many aspects of the field. The volume opens with a description by Bolduc and Murty of one of the products stemming from the development of tide gauge networks in the northern and tropical Atlantic. This work is relevant to the growth of the Global Sea Level Observing System (GLOSS), the main goal of which is to provide the world with an efficient, coherent sea level monitoring system for océanographie and climatological research. The subsequent four papers present results from the analysis of existing tide gauge data, including those datasets available from the Permanent Service for Mean Sea Level and the TOGA Sea Level Center. Two of the four, by Wroblewski and by Pasaric and Orlic, are concerned with European sea level changes, while Yu Jiye et al. discuss inter-annual changes in the Pacific, and Wang Baocan et al. describe variability in the Changjiang estuary in China. The papers by El- Abd and A wad, on Red Sea levels, are the only contributions to the volume from the large research community of geologists concerned with sea level changes.

  19. Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes

    Science.gov (United States)

    Bartlein, P.J.; Edwards, M.E.; Hostetler, Steven W.; Shafer, Sarah; Anderson, P.M.; Brubaker, L. B; Lozhkin, A. V

    2015-01-01

    Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modeling and paleo-observations. The subcontinental region of Beringia (northeastern Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering–Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia's early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present-day simulations of regional climate – one with modern and one with 11 ka geography – plus another simulation for 6 ka. In addition, we performed five ~ 11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka Control, which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present-day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf boreal

  20. Extended late Holocene relative sea-level histories for North Carolina, USA

    Science.gov (United States)

    Kemp, Andrew C.; Kegel, Jessica J.; Culver, Stephen J.; Barber, Donald C.; Mallinson, David J.; Leorri, Eduardo; Bernhardt, Christopher E.; Cahill, Niamh; Riggs, Stanley R.; Woodson, Anna L.; Mulligan, Ryan P.; Horton, Benjamin P.

    2017-03-01

    We produced ∼3000-year long relative sea-level (RSL) histories for two sites in North Carolina (USA) using foraminifera preserved in new and existing cores of dated salt-marsh sediment. At Cedar Island, RSL rose by ∼2.4 m during the past ∼3000 years compared to ∼3.3 m at Roanoke Island. This spatial difference arises primarily from differential GIA that caused late Holocene RSL rise to be 0.1-0.2 mm/yr faster at Roanoke Island than at Cedar Island. However, a non-linear difference in RSL between the two study regions (particularly from ∼0 CE to ∼1250 CE) indicates that additional local- to regional-scale processes drove centennial-scale RSL change in North Carolina. Therefore, the Cedar Island and Roanoke Island records should be considered as independent of one another. Between-site differences on sub-millennial timescales cannot be adequately explained by non-stationary tides, sediment compaction, or local sediment dynamics. We propose that a period of accelerating RSL rise from ∼600 CE to 1100 CE that is present at Roanoke Island (and other sites north of Cape Hatteras at least as far as Connecticut), but absent at Cedar Island (and other sites south of Cape Hatteras at least as far as northeastern Florida) is a local-to regional-scale effect of dynamic ocean and/or atmospheric circulation.

  1. Holocene climate changes in eastern Beringia (NW North America) – A systematic review of multi-proxy evidence

    Science.gov (United States)

    Kaufman, Darrell S.; Axford, Yarrow L.; Henderson, Andrew C.G.; McKay, Nicolas P.; Oswald, W. Wyatt; Saenger, Casey; Anderson, R. Scott; Bailey, Hannah L.; Clegg, Benjamin; Gajewski, Konrad; Hu, Feng Sheng; Jones, Miriam C.; Massa, Charly; Routson, Cody C.; Werner, Al; Wooller, Matthew J.; Yu, Zicheng

    2016-01-01

    Reconstructing climates of the past relies on a variety of evidence from a large number of sites to capture the varied features of climate and the spatial heterogeneity of climate change. This review summarizes available information from diverse Holocene paleoenvironmental records across eastern Beringia (Alaska, westernmost Canada and adjacent seas), and it quantifies the primary trends of temperature- and moisture-sensitive records based in part on midges, pollen, and biogeochemical indicators (compiled in the recently published Arctic Holocene database, and updated here to v2.1). The composite time series from these proxy records are compared with new summaries of mountain-glacier and lake-level fluctuations, terrestrial water-isotope records, sea-ice and sea-surface-temperature analyses, and peatland and thaw-lake initiation frequencies to clarify multi-centennial- to millennial-scale trends in Holocene climate change. To focus the synthesis, the paleo data are used to frame specific questions that can be addressed with simulations by Earth system models to investigate the causes and dynamics of past and future climate change. This systematic review shows that, during the early Holocene (11.7–8.2 ka; 1 ka = 1000 cal yr BP), rather than a prominent thermal maximum as suggested previously, temperatures were highly variable, at times both higher and lower than present (approximate mid-20th-century average), with no clear spatial pattern. Composited pollen, midge and other proxy records average out the variability and show the overall lowest summer and mean-annual temperatures across the study region during the earliest Holocene, followed by warming over the early Holocene. The sparse data available on early Holocene glaciation show that glaciers in southern Alaska were as extensive then as they were during the late Holocene. Early Holocene lake levels were low in interior Alaska, but moisture indicators show pronounced differences across the region. The highest

  2. Caribbean mangroves adjust to rising sea level through biotic controls on change in soil elevation

    Science.gov (United States)

    McKee, K.L.; Cahoon, D.R.; Feller, Ilka C.

    2007-01-01

    Aim The long-term stability of coastal ecosystems such as mangroves and salt marshes depends upon the maintenance of soil elevations within the intertidal habitat as sea level changes. We examined the rates and processes of peat formation by mangroves of the Caribbean Region to better understand biological controls on habitat stability. Location Mangrove-dominated islands on the Caribbean coasts of Belize, Honduras and Panama were selected as study sites. Methods Biological processes controlling mangrove peat formation were manipulated (in Belize) by the addition of nutrients (nitrogen or phosphorus) to Rhizophora mangle (red mangrove), and the effects on the dynamics of soil elevation were determined over a 3-year period using rod surface elevation tables (RSET) and marker horizons. Peat composition and geological accretion rates were determined at all sites using radiocarbon-dated cores. Results The addition of nutrients to mangroves caused significant changes in rates of mangrove root accumulation, which influenced both the rate and direction of change in elevation. Areas with low root input lost elevation and those with high rates gained elevation. These findings were consistent with peat analyses at multiple Caribbean sites showing that deposits (up to 10 m in depth) were composed primarily of mangrove root matter. Comparison of radiocarbon-dated cores at the study sites with a sea-level curve for the western Atlantic indicated a tight coupling between peat building in Caribbean mangroves and sea-level rise over the Holocene. Main conclusions Mangroves common to the Caribbean region have adjusted to changing sea level mainly through subsurface accumulation of refractory mangrove roots. Without root and other organic inputs, submergence of these tidal forests is inevitable due to peat decomposition, physical compaction and eustatic sea-level rise. These findings have relevance for predicting the effects of sea-level rise and biophysical processes on tropical

  3. Sea level and shoreline reconstructions for the Red Sea: isostatic and tectonic considerations and implications for hominin migration out of Africa

    Science.gov (United States)

    Lambeck, Kurt; Purcell, Anthony; Flemming, Nicholas. C.; Vita-Finzi, Claudio; Alsharekh, Abdullah M.; Bailey, Geoffrey N.

    2011-12-01

    The history of sea level within the Red Sea basin impinges on several areas of research. For archaeology and prehistory, past sea levels of the southern sector define possible pathways of human dispersal out of Africa. For tectonics, the interglacial sea levels provide estimates of rates for vertical tectonics. For global sea level studies, the Red Sea sediments contain a significant record of changing water chemistry with implications on the mass exchange between oceans and ice sheets during glacial cycles. And, because of its geometry and location, the Red Sea provides a test laboratory for models of glacio-hydro-isostasy. The Red Sea margins contain incomplete records of sea level for the Late Holocene, for the Last Glacial Maximum, for the Last Interglacial and for earlier interglacials. These are usually interpreted in terms of tectonics and ocean volume changes but it is shown here that the glacio-hydro-isostatic process is an additional important component with characteristic spatial variability. Through an iterative analysis of the Holocene and interglacial evidence a separation of the tectonic, isostatic and eustatic contributions is possible and we present a predictive model for palaeo-shorelines and water depths for a time interval encompassing the period proposed for migrations of modern humans out of Africa. Principal conclusions include the following. (i) Late Holocene sea level signals evolve along the length of the Red Sea, with characteristic mid-Holocene highstands not developing in the central part. (ii) Last Interglacial sea level signals are also location dependent and, in the absence of tectonics, are not predicted to occur more than 1-2 m above present sea level. (iii) For both periods, Red Sea levels at 'expected far-field' elevations are not necessarily indicative of tectonic stability and the evidence points to a long-wavelength tectonic uplift component along both the African and Arabian northern and central sides of the Red Sea. (iv) The

  4. Biogeochemical analysis of ancient Pacific Cod bone suggests Hg bioaccumulation was linked to paleo sea level rise and climate change

    Directory of Open Access Journals (Sweden)

    Maribeth S. Murray

    2015-02-01

    Full Text Available Deglaciation at the end of the Pleistocene initiated major changes in ocean circulation and distribution. Within a brief geological time, large areas of land were inundated by sea-level rise and today global sea level is 120 m above its minimum stand during the last glacial maximum. This was the era of modern sea shelf formation; climate change caused coastal plain flooding and created broad continental shelves with innumerable consequences to marine and terrestrial ecosystems and human populations. In Alaska, the Bering Sea nearly doubled in size and stretches of coastline to the south were flooded, with regional variability in the timing and extent of submergence. Here we suggest how past climate change and coastal flooding are linked to mercury bioaccumulation that could have had profound impacts on past human populations and that, under conditions of continued climate warming, may have future impacts. Biogeochemical analysis of total mercury (tHg and 13C/15N ratios in the bone collagen of archaeologically recovered Pacific Cod (Gadus macrocephalus bone shows high levels of tHg during early/mid-Holocene. This pattern cannot be linked to anthropogenic activity or to food web trophic changes, but may result from natural phenomena such as increases in productivity, carbon supply and coastal flooding driven by glacial melting and sea-level rise. The coastal flooding could have led to increased methylation of Hg in newly submerged terrestrial land and vegetation. Methylmercury is bioaccumulated through aquatic food webs with attendant consequences for the health of fish and their consumers, including people. This is the first study of tHg levels in a marine species from the Gulf of Alaska to provide a time series spanning nearly the entire Holocene and we propose that past coastal flooding resulting from climate change had the potential to input significant quantities of Hg into marine food webs and subsequently to human consumers.

  5. Low post-glacial rebound rates in the Weddell Sea due to Late Holocene ice-sheet readvance

    Science.gov (United States)

    Bradley, Sarah L.; Hindmarsh, Richard C. A.; Whitehouse, Pippa; Bentley, Michael J.; King, Matt

    2014-05-01

    The Holocene deglaciation of West Antarctica resulted in widespread ice surface lowering. While many ice-sheet reconstructions generally assume a monotone Holocene retreat for the West Antarctica Ice sheet (WAIS) [Ivins et al., 2013; Peltier, 2004; Whitehouse et al., 2012], an increasing number of glaciological observations infer it is readvancing, following retreat behind the present-day margin[Siegert et al., 2013]. We will show that a readvance in the Weddell Sea region can reconcile two outstanding problems: (i) the present-day widespread occurrence of seemingly stable ice-streams grounded on beds that deepen inland in apparent contradiction to theory [Schoof, 2007]; and (ii) the inability of models of Glacial Isostatic Adjustment (GIA) to match present-day uplift rates [Whitehouse et al., 2012]. Combining a suite of ice loading histories that include a readvance with a model of GIA provides significant improvements to predictions of present-day uplift rates, and we are able to reproduce previously unexplained observations of subsidence in the southern sector of the Weddell Sea. We hypothesize that retreat behind present grounding lines occurred when the bed was lower, and isostatic recovery led to shallowing, ice sheet re-grounding and readvance. We will conclude that some sections of the current WAIS grounding line that are theoretically unstable, may be advancing and that the volume change of the WAIS may have been more complex in the Late Holocene than previously posited. This revised Holocene ice-loading history would have important implications for the GIA correction applied to Gravity Recovery and Climate Experiment (GRACE) data, likely resulting in a reduction in the GIA correction and a smaller estimate of present-day ice mass loss within the Weddell Sea region of the WAIS. Ivins, E. R., T. S. James, J. Wahr, E. J. O. Schrama, F. W. Landerer, and K. M. Simon (2013), Antarctic contribution to sea level rise observed by GRACE with improved GIA correction

  6. MIS 5e relative sea-level changes in the Mediterranean Sea: Contribution of isostatic disequilibrium

    Science.gov (United States)

    Stocchi, Paolo; Vacchi, Matteo; Lorscheid, Thomas; de Boer, Bas; Simms, Alexander R.; van de Wal, Roderik S. W.; Vermeersen, Bert L. A.; Pappalardo, Marta; Rovere, Alessio

    2018-04-01

    Sea-level indicators dated to the Last Interglacial, or Marine Isotope Stage (MIS) 5e, have a twofold value. First, they can be used to constrain the melting of Greenland and Antarctic Ice Sheets in response to global warming scenarios. Second, they can be used to calculate the vertical crustal rates at active margins. For both applications, the contribution of glacio- and hydro-isostatic adjustment (GIA) to vertical displacement of sea-level indicators must be calculated. In this paper, we re-assess MIS 5e sea-level indicators at 11 Mediterranean sites that have been generally considered tectonically stable or affected by mild tectonics. These are found within a range of elevations of 2-10 m above modern mean sea level. Four sites are characterized by two separate sea-level stands, which suggest a two-step sea-level highstand during MIS 5e. Comparing field data with numerical modeling we show that (i) GIA is an important contributor to the spatial and temporal variability of the sea-level highstand during MIS 5e, (ii) the isostatic imbalance from the melting of the MIS 6 ice sheet can produce a >2.0 m sea-level highstand, and (iii) a two-step melting phase for the Greenland and Antarctic Ice Sheets reduces the differences between observations and predictions. Our results show that assumptions of tectonic stability on the basis of the MIS 5e records carry intrinsically large uncertainties, stemming either from uncertainties in field data and GIA models. The latter are propagated to either Holocene or Pleistocene sea-level reconstructions if tectonic rates are considered linear through time.

  7. Late holocene primary productivity and sea surface temperature variations in the northeastern Arabian Sea: Implications for winter monsoon variability.

    Digital Repository Service at National Institute of Oceanography (India)

    Boll, A.; Luckge, A.; Munz, P.; Forke, S.; Schulz, H.; Ramaswamy, V.; Rixen, T.; Gaye, B.; Emeis, K.-C.

    changes in winter monsoon strength with winds from the northeast that drive convective mixing and high surface ocean productivity in the northeastern Arabian Sea. To establish a high-resolution record of winter monsoon variability for the late Holocene, we...

  8. Mediterranean moisture source for an Early-Holocene humid period in the Northern Red Sea

    NARCIS (Netherlands)

    Arz, H.W.; Lamy, F.; Paetzold, J.; Mueller, P.J.; Prins, M.A.

    2003-01-01

    Paleosalinity and terrigenous sediment input changes reconstructed on two sediment cores from the northernmost Red Sea were used to infer hydrological changes at the southern margin of the Mediterranean climate zone during the Holocene. Between approximately 9.25 and 7.25 thousand years ago, about

  9. Holocene megathermal abrupt environmental changes derived from {sup 14}C dating of a coral reef at Leizhou Peninsula, South China Sea

    Energy Technology Data Exchange (ETDEWEB)

    Shen Chengde; Yi Weixi E-mail: cdshen@gig.ac.cn; Yu Kefu; Sun Yanmin; Liu Tungsheng; Beer, J.; Hajdas, I.; Bonani, G

    2004-08-01

    A depth profile of a Goniopora coral reef at Leizhou Peninsula, South China Sea, was radiocarbon dated using liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS). The time of formation, during 6600-7400 cal BP, can be divided into nine stages, each terminated by abrupt growth cessation of Goniopora and appearance of Ostrea shells. The results show that, during the Holocene megathermal (8.2-3.3 ka BP), large climatic changes have occurred in the South China Sea area.

  10. Extended late Holocene relative sea-level histories for North Carolina, USA

    Science.gov (United States)

    Kemp, Andrew C.; Kegel, Jessica J.; Culver, Stephen J.; Barber, Donald C.; Mallinson, David J.; Leorri, Eduardo; Bernhardt, Christopher E.; Cahill, Niamh; Riggs, Stanley R.; Woodson, Anna L.; Mulligan, Ryan P.; Horton, Benjamin P.

    2017-01-01

    We produced ∼3000-year long relative sea-level (RSL) histories for two sites in North Carolina (USA) using foraminifera preserved in new and existing cores of dated salt-marsh sediment. At Cedar Island, RSL rose by ∼2.4 m during the past ∼3000 years compared to ∼3.3 m at Roanoke Island. This spatial difference arises primarily from differential GIA that caused late Holocene RSL rise to be 0.1–0.2 mm/yr faster at Roanoke Island than at Cedar Island. However, a non-linear difference in RSL between the two study regions (particularly from ∼0 CE to ∼1250 CE) indicates that additional local- to regional-scale processes drove centennial-scale RSL change in North Carolina. Therefore, the Cedar Island and Roanoke Island records should be considered as independent of one another. Between-site differences on sub-millennial timescales cannot be adequately explained by non-stationary tides, sediment compaction, or local sediment dynamics. We propose that a period of accelerating RSL rise from ∼600 CE to 1100 CE that is present at Roanoke Island (and other sites north of Cape Hatteras at least as far as Connecticut), but absent at Cedar Island (and other sites south of Cape Hatteras at least as far as northeastern Florida) is a local-to regional-scale effect of dynamic ocean and/or atmospheric circulation.

  11. Contrasting trends in North Atlantic deep-water formation in the Labrador Sea and Nordic Seas during the Holocene

    NARCIS (Netherlands)

    Renssen, H.; Goosse, H.; Fichefet, T.

    2005-01-01

    The Holocene North Atlantic deep-water formation is studied in a 9,000-year long simulation with a coupled climate model of intermediate complexity, forced by changes in orbital forcing and atmospheric trace gas concentrations. During the experiment, deep-water formation in the Nordic Seas is

  12. Timing and magnitude of the Caribbean mid-Holocene highstand

    Science.gov (United States)

    Ashe, E.; Khan, N.; Horton, B.; Brocard, G. Y.; Dutton, A.; Engelhart, S. E.; Kopp, R. E.; Hill, D. F.; Peltier, W. R.; Scatena, F. N.

    2015-12-01

    We present a database of published and new relative sea-level (RSL) data for the past 13 ka, which constrains the Holocene sea-level histories of the Caribbean coast of Central and South America (Florida Keys, USA to Guyana) and the Bahamas and Greater and Lesser Antilles islands. Our evaluation of mangrove peat and Acropora palmata sea-level indicators from geological investigations provides 503 sea-level index points and 242 limiting dates. We subdivide the database into 21 regions based on the availability of data, tectonic setting, and distance from the former Laurentide ice sheet. Most index points (75%) and limiting dates (90%) are <8 ka, although there is an unusual temporal distribution with the greatest amount of the data (~28%) occurring between 6-8 ka. We reassess and screen radiocarbon and U/Th ages of mangrove peat and coral data. We use the stratigraphic position (overburden thickness) of index points account for sediment compaction, and use the paleotidal model of Hill et al. (2011) to account for Holocene changes in paleotidal range. A noisy-input Gaussian process regression model calculates that the rates of RSL change were highest during the early Holocene (3-8 mm/yr) and have decreased over time (< 2 mm/yr), which is related to the reduction of ice equivalent meltwater input and collapse of the proglacial forebulge during the Holocene. The sea-level reconstructions demonstrate that RSL did not exceed the present height (0 m) during the Holocene in the majority of locations, with the exception of a small highstand (<2 m) on the northern coast of South America along the Orinoco Delta and Suriname/Guyana located furthest away from the former Laurentide Ice Sheet. The different sea-level histories are an ongoing isostatic response to deglaciation of the Laurentide Ice Sheet and suggest subsidence resulting from collapse of the proglacial forebulge reaches further south than previously considered.

  13. Final deglaciation of the Scandinavian Ice Sheet and implications for the Holocene global sea-level budget

    Science.gov (United States)

    Cuzzone, Joshua K.; Clark, Peter U.; Carlson, Anders E.; Ullman, David J.; Rinterknecht, Vincent R.; Milne, Glenn A.; Lunkka, Juha-Pekka; Wohlfarth, Barbara; Marcott, Shaun A.; Caffee, Marc

    2016-08-01

    The last deglaciation of the Scandinavian Ice Sheet (SIS) from ∼ 21, 000 to 13,000 yr ago is well-constrained by several hundred 10Be and 14C ages. The subsequent retreat history, however, is established primarily from minimum-limiting 14C ages and incomplete Baltic-Sea varve records, leaving a substantial fraction of final SIS retreat history poorly constrained. Here we develop a high-resolution chronology for the final deglaciation of the SIS based on 79 10Be cosmogenic exposure dates sampled along three transects spanning southern to northern Sweden and Finland. Combining this new chronology with existing 10Be ages on deglaciation since the Last Glacial Maximum shows that rates of SIS margin retreat were strongly influenced by deglacial millennial-scale climate variability and its effect on surface mass balance, with regional modulation of retreat associated with dynamical controls. Ice-volume estimates constrained by our new chronology suggest that the SIS contributed ∼ 8 m sea-level equivalent to global sea-level rise between ∼14.5 ka and 10 ka. Final deglaciation was largely complete by ∼10.5 ka, with highest rates of sea-level rise occurring during the Bølling-Allerød, a 50% decrease during the Younger Dryas, and a rapid increase during the early Holocene. Combining our SIS volume estimates with estimated contributions from other remaining Northern Hemisphere ice sheets suggests that the Antarctic Ice Sheet (AIS) contributed 14.4 ± 5.9 m to global sea-level rise since ∼13 ka. This new constraint supports those studies that indicate that an ice volume of 15 m or more of equivalent sea-level rise was lost from the AIS during the last deglaciation.

  14. Sea-level standstill and dominant hermatypic coral from the holocene raised reef terraces at the Kikai Island, Ryukyu Islands

    International Nuclear Information System (INIS)

    Hongo, Chuki

    2010-01-01

    Coral reef terraces are one of the best recorders of biological response to environmental change events (e.g., sea-level changes). Kikai Island provides a rare opportunity to show biological and ecological frameworks (e.g., competition, coexistence, and succession) during a recent geological period. The island is fringed by raised Holocene raised reef terraces, which formed as a result of periodic tectonic uplifts. This study aims to characterize the spatial and temporal changes of corals at this island during the Holocene. The analysis is based on topographical and biological data obtained for the three sites (Shidooke, Kadon, and Nakugama reefs). Three raised reef terraces (Terrace II, III, and IV) grew from 7300 to 4500 years ago (during 2800 years), from 4500 to 2900 years ago (during 1600 years), and from 2900 to 1800 years ago (during 1100 years), respectively. Terrace II and III were uplifted 1-2 m around 4500 years ago and around 2900 years ago. Terrace IV was uplifted 1-2 m around 1800 years ago. The modern reef has been composed of corals for 1800 years. Sixteen coral genera and 53 species were recorded from the reef terraces. Terrace III and IV were dominated by four coral species (A. digitifera, A. robusta, G. retiformis, and F. stelligera), but Terrace II was predominantly composed of A. digitifera and A. robusta. These biological and ecological variations between the terraces represent a growth strategy responding to differences of reef growth time and/or insolation. (author)

  15. On the evolution of a holocene barrier coast

    DEFF Research Database (Denmark)

    Fruergaard, Mikkel

    in a distinct stratal stacking pattern of each of the investigated coastal barrier systems. We conclude that the overall infilling of the barrier systems over the Holocene was mainly controlled by sea-level rise and sediment supply. However, major storms and tidal channel migration have greatly affected......This thesis investigates the sedimentary evolution of a Holocene barrier coast with special focus on how barrier system stratigraphy is affected by changes in sea-level and sediment supply. Coastal barrier systems comprise about 13% of the world’s coastlines and they are mportant components...... of the stratigraphic record of the Earth. Sea-level rise and sediment supply are the two most important factors controlling barrier system evolution. Detailed depositional reconstructions of a number of barrier systems from the Danish Wadden Sea area have been carried out in order to evaluate the sedimentary effects...

  16. Grain-size based sea-level reconstruction in the south Bohai Sea during the past 135 kyr

    Science.gov (United States)

    Yi, Liang; Chen, Yanping

    2013-04-01

    and sea level. Nature 324, 137-140. Charman, D.J., Roe, H.M., Roland Gehrels, W., 2002. Modern distribution of saltmarsh testate amoebae: regional variability of zonation and response to environmental variables. Journal of Quaternary Science 17, 387-409. Horton, B.P., 1997. Quantification of the indicative meaning of a range of Holocene sea-level index points from the western North Sea, Department of Geography. University of Durham, Durham City, UK, p. 509. Horton, B.P., Corbett, R., Culver, S.J., Edwards, R.J., Hillier, C., 2006. Modern saltmarsh diatom distributions of the Outer Banks, North Carolina, and the development of a transfer function for high resolution reconstructions of sea level. Estuarine, Coastal and Shelf Science 69, 381-394. IOCAS (Institute of Oceanology, Chinese Academy of Sciences), 1985. Bohai Sea Geology. Science Press, Beijing, China. Madsen, A.T., Murray, A.S., Andersen, T.J., Pejrup, M., 2007. Temporal changes of accretion rates on an estuarine salt marsh during the late Holocene -Reflection of local sea level changes? The Wadden Sea, Denmark. Marine Geology 242, 221-233. Mauz, B., Hassler, U., 2000. Luminescence chronology of Late Pleistocene raised beaches in southern Italy: new data of relative sea-level changes. Marine Geology 170, 187-203. Yi, L., Yu, H.J., Ortiz, J.D., Xu, X.Y., Qiang, X.K., Huang, H.J., Shi, X., Deng, C.L., 2012. A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis. Sedimentary Geology 281, 88-100. Zong, Y., Shennan, I., Combellick, R.A., Hamilton, S.L., Rutherford, M.M., 2003. Microfossil evidence for land movements associated with the AD 1964 Alaska earthquake. The Holocene 13, 7-20.

  17. Ice volume and climate changes from a 6000 year sea-level record in French Polynesia.

    Science.gov (United States)

    Hallmann, N; Camoin, G; Eisenhauer, A; Botella, A; Milne, G A; Vella, C; Samankassou, E; Pothin, V; Dussouillez, P; Fleury, J; Fietzke, J

    2018-01-18

    Mid- to late-Holocene sea-level records from low-latitude regions serve as an important baseline of natural variability in sea level and global ice volume prior to the Anthropocene. Here, we reconstruct a high-resolution sea-level curve encompassing the last 6000 years based on a comprehensive study of coral microatolls, which are sensitive low-tide recorders. Our curve is based on microatolls from several islands in a single region and comprises a total of 82 sea-level index points. Assuming thermosteric contributions are negligible on millennial time scales, our results constrain global ice melting to be 1.5-2.5 m (sea-level equivalent) since ~5500 years before present. The reconstructed curve includes isolated rapid events of several decimetres within a few centuries, one of which is most likely related to loss from the Antarctic ice sheet mass around 5000 years before present. In contrast, the occurrence of large and flat microatolls indicates periods of significant sea-level stability lasting up to ~300 years.

  18. Living with sea-level rise and climate change: a case study of the Netherlands

    NARCIS (Netherlands)

    van Koningsveld, M.; Mulder, J.P.M. P.M.; Stive, M.J.F.; van der Valk, L.; van der Weck, A.W.

    2008-01-01

    Based on historical hindsight, this paper shows that sea-level rise has played a fundamental role in the development of the low-lying environment of the Netherlands. It was beneficial in morphological terms during the mid-Holocene, but from Roman times, it has been a threat to the coastal zone

  19. Reconstruction of Redox Conditions and Productivity in Coastal Waters of the Bothnian Sea during the Holocene

    Science.gov (United States)

    Dijkstra, N.; Quintana Krupinski, N. B.; Slomp, C. P.

    2014-12-01

    Hypoxia is a growing problem in coastal waters worldwide, and is a well-known cause of benthic mortality. The semi-enclosed Baltic Sea is currently the world's largest human-induced dead zone. During the early Holocene, it experienced several periods of natural hypoxia following the intrusion of seawater into the previous freshwater lake. Recent studies suggest that at that time, the hypoxia expanded north to include the deep basin of the Bothnian Sea. In this study, we assess whether the coastal zone of the Bothnian Sea was also hypoxic during the early Holocene. We analysed a unique sediment record (0 - 30 mbsf) from the Ångermanälven estuary, which was retrieved during the International Ocean Discovery Programme (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. Using geochemical proxies and foraminifera abundances, we reconstruct the changes in redox conditions, salinity and productivity in the estuary. Our preliminary results suggest that bottom waters in this coastal basin became anoxic upon the intrusion of brackish seawater in the early Holocene and that the productivity was elevated. The presence of benthic foraminifera in this estuary during the mid-Holocene suggests more saline conditions in the Bothnian Sea than today. Due to isostatic uplift, the estuary likely gradually became more isolated from the Bothnian Sea, which itself became more isolated from the Baltic Sea. Both factors likely explain the subsequent re-oxygenation of bottom waters and gradual refreshening of the estuary as recorded in the sediments. Interestingly, the upper meters of sediment are enriched in minerals that contain iron, phosphorus and manganese. We postulate that the refreshening of the estuary triggered the formation of these minerals, thereby increasing the phosphorus retention in these sediments and further reducing primary productivity. This enhanced retention linked to refreshening may contribute to the current oligotrophic conditions in the Bothnian Sea.

  20. Multidecadal variations in the early Holocene outflow of Red Sea Water into the Arabian Sea

    Science.gov (United States)

    Jung, S. J. A.; Ganssen, G. M.; Davies, G. R.

    2001-12-01

    We present Holocene stable oxygen isotope data from the deep Arabian Sea off Somalia at a decadal time resolution as a proxy for the history of intermediate/upper deep water. These data show an overall δ18O reduction by 0.5‰ between 10 and ˜6.5 kyr B.P. superimposed upon short-term δ18O variations at a decadal-centennial timescale. The amplitude of the decadal variations is 0.3‰ prior, and up to 0.6‰ subsequent, to ˜8.1 kyr B.P. We conclude from modeling experiments that the short-term δ18O variations between 10 and ˜6.5 kyr B.P. most likely document changes in the evaporation-precipitation balance in the central Red Sea. Changes in water temperature and salinity cause the outflowing Red Sea Water to settle roughly 800 m deeper than today.

  1. Present day sea level changes: observation and causes

    International Nuclear Information System (INIS)

    Lombard, A.

    2005-11-01

    Whereas sea level has changed little over the last 2000 years, it has risen at a rate of about 2 mm/year during the 20. century. This unexpected sea level rise has been attributed to the anthropogenic global warming, recorded over several decades. Sea level variations have been measured globally and precisely for about 12 years due to satellite altimeter missions Topex/Poseidon and Jason-1. These observations indicate a global mean sea level rise of about 3 mm/year since 1993, a value significantly larger than observed during previous decades. Recent observations have allowed us to quantify the various climatic factors contributing to observed sea level change: thermal expansion of sea water due to ocean warming, melting of mountain glaciers and ice sheets, and changes in the land water reservoirs. A water budget based on these new observations allows us to partly explain the observed sea level rise. In particular, we show that the thermal expansion explains only 25% of the secular sea level rise as recorded by tide-gauges over the last 50 years, while it contributes about 50% of sea level rise observed over the last decade. Meanwhile, recent studies show that glacier and ice sheet melting could contribute the equivalent of 1 mm/year in sea level rise over the last decade. In addition, the high regional variability of sea level trends revealed by satellite altimetry is mainly due to thermal expansion. There is also an important decadal spatio-temporal variability in the ocean thermal expansion over the last 50 years, which seems to be controlled by natural climate fluctuations. We question for the first time the link between the decadal fluctuations in the ocean thermal expansion and in the land reservoirs, and indeed their climatic contribution to sea level change. Finally a preliminary analysis of GRACE spatial gravimetric observations over the oceans allows us to estimate the seasonal variations in mean sea level due to ocean water mass balance variations

  2. Hydrologic Control on Bacterial Nitrogen Fixation in the Holocene Black Sea

    Science.gov (United States)

    Fulton, J. M.; Arthur, M. A.; Freeman, K. H.

    2008-12-01

    Stratified oceans of the Phanerozoic Oceanic Anoxic Events apparently were dominated by bacterial nitrogen fixation. Decreased marine N:P nutrient ratios resulting from increased denitrification and decreased phosphate burial efficiency under anoxic waters drove this nutrient regime. This model is upheld by the presence of cyanobacterial hopanoid biomarkers in sedimentary records and δ15N values indicative of nitrogen fixation. However, in the largest modern redox-stratified marine basin, the Black Sea, bacterial nitrogen fixation seems to be only a minor contributor to the nitrogen cycle. In this study, we use geochemical proxies to evaluate the role of bacterial nitrogen fixation during the deposition of the Holocene Black Sea sapropel, starting 7.8 ka. We report compound-specific nitrogen and carbon stable isotope values of pyropheophytin a, a chlorophyll degradation product, and bacteriochlorophyll e produced by green sulfur bacteria. We also present the surprising finding of scytonemin, a pigment produced only by filamentous cyanobacteria exposed to ultraviolet radiation, in certain intervals in these sediments. In the Holocene, nitrogen fixation in the Black Sea is most prominent during times of reduced river water influx. This directly decreases the external flux of nitrate into the surface waters. Reduced freshwater influx also decreases the volume of low salinity water dispersed around the sea by the Rim Current, allowing the chemocline to shoal along the margins. Previous geochemical studies have described this changing chemocline geometry. The exposure of shallow water sediments to anoxic waters further stimulates nitrogen fixation by releasing more phosphorus to the system. Nitrogen fixation is recorded in the sediments as bulk and compound-specific pyropheophytin a δ15N values near 0 ‰ and -5 ‰, respectively. We have also detected scytonemin in two intervals characterized by especially low δ15N values. This compound suggests abundant filamentous

  3. Course of sea-level change

    Science.gov (United States)

    Carlowicz, Michael

    This summer, the Environment and Climate Program of the European Union will offer an advanced study course on “sea-level changes on micro to macro timescales: measurements, modeling, interpretation, and application.” The short course will be taught from July 1-12 at the Aesclepon Conference Center on the island of Kos, Greece.The interdisciplinary course is designed to bring together at least 40 students from different disciplines in an attempt to share and disseminate fundamental ideas about sea level change, focusing particularly on changes influenced by anthropogenic factors. Participants will be selected by a scientific panel; the European Union will conduct the course free of charge and will provide free lodging. Students must pay for their own travel expenses and food.

  4. Influences of Holocene sea level, regional tectonics, and fluvial, gravity and slope currents induced sedimentation on the regional geomorphology of the continental slope off northwestern India

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.; Almeida, F.

    the Holocene sea level. The Bombay high area has slope breaks between 400 and 600 m, whereas off Saurashtra steep breaks in the slope occur between 560 and 960 m depth. Further southwards, at the slope, elevations and depressions are present. Variations...

  5. Land-Sea Correlation of Holocene Records in NW Iberian Peninsula

    Science.gov (United States)

    Gonzalez-Alvare, R.; Costas, S.; Bernardez, P.; Frances, G.; Alejo, I.

    2005-12-01

    Holocene climate fluctuations in the temperate region of the Northeast Atlantic have been established by comparing marine and terrestrial proxies. This work is based on suction-cores collected in the Cies Islands lagoon (NW Spain) and vibro-cores from the adjacent continental shelf. The lower Holocene marine record (9400-7000 yr BP) consists on sandy transgressive facies overlying fluvial Pleistocene deposits. During this time the continental shelf was dominated by high energy processes linked to the progressive and fast sea level rise. The rate of sea level rise sharply decelerated at 7000 yr BP and a high productive marine environment was fully established, as revealed by planktonic foraminifera assemblages and biogeochemical markers. In the terrestrial areas, peat deposits were formed beginning around 6000 yr BP in the deeper parts of the paleo-relief that was developed above the granitic basement. The peat was deposited in a fresh-water shallow coastal lake under warm and humid conditions that are brought about by prevailing SW winds. From 4800 yr BP, a progressive rainfall decrease provoked the lowering of the lake level and a weaker fluvial influence on the adjacent shelf. The prevailing eastern winds caused significantly drier conditions between 4000 and 3200 yr BP. During this period the coastal lake dried and the peat layer was covered by aeolian deposits. At the continental shelf a strong stratification of the water column induced a fall in the productivity. The end of this period is marked by the increase of storm regimes caused by a shift to prevailing SW winds. The last 3000 years are characterized by humid and warm conditions, and the enhancement of upwelling regime and terrestrial sediment supply. In Cies Islands, a sand barrier-lagoon complex was developed as a consequence of both the sea level rise and the inundation of the lower areas in the island.

  6. NW Pacific mid-depth ventilation changes during the Holocene

    Science.gov (United States)

    Rella, S.; Uchida, M.

    2010-12-01

    During the last 50 years the oxygen content of North Pacific Intermediate Water primarily originating in the Okhotsk Sea has declined suggesting decreased mid-depth water circulation, likely leading to changes in biological productivity in the NW Pacific realm and a decrease in CO2 drawdown. It is therefore of high interest to elucidate the climate-oceanic interconnections of the present interglacial period (Holocene) in the NW Pacific, in order to predict possible future climate and surface productivity changes associated with a decrease in mid-depth ventilation in this ecologically sensitive region. However, such efforts have been hampered so far by the lack of appropriate sediment cores with fast sedimentation rates during the Holocene. Core CK05-04 that was recovered in 2005 from off Shimokita peninsula, Japan, at ~1000 m depth shows sedimentation rates of ~80 cm/kyr during the Holocene and therefore presents an ideal opportunity to reconstruct for the first time the Holocene ventilation history of the NW Pacific Ocean. We employ Accelerator Mass Spectroscopy (NIES-TERRA, Tsukuba) radiocarbon analysis of co-existing benthic and planktonic foraminifera to conclude on the ventilation age of the mid-depth water using benthic-planktonic radiocarbon age differences. At the conference we would like to present the results.

  7. Reconciling late Quaternary transgressions in the Bohai Sea, China to the global sea level changes, and new linkage of sedimentary records to three astronomical rhythms

    Science.gov (United States)

    Yi, Liang

    2013-04-01

    The Bohai Sea in China was formed by subsidence during the Cenozoic. Some 2000-3000 m of fluvial, lacustrine and marine sediments has been deposited in the basin (IOCAS 1985), and these sediments have great potentials in high-/low-latitude interaction, environmental impacts on ancient human activities, and other important issues (Liu, 2009; Yi et al. 2012a), because it is influenced by the Siberian-Mongolian Highs and the ITCZ, and is close to the Nihewan basin and the Zhoukoudian site which are both world-renowned for the discovery of Homo erectus. Since the 1970s, hundreds of studies have been conducted around the Bohai Sea and the major results could be summarized as follows (Zhao et al., 1978; IOCAS, 1985; Liu, 2009, and references therein): (1) constrained by radiocarbon dating, TL/OSL or geomagnetic excursion, three transgressions (T1, T2, T3) developed during the Holocene, marine isotopic stage (MIS) 3 and MIS 5, respectively; and (2) regressions occurred at the beginning of glacial stages, i.e. MIS2 and MIS4. However, apparent inconsistency could be found between T2 and T3, and the question is that in the context that MIS 3 is an inter-stadial stage with a global sea level of 60~80 m lower than the present (Chappell et al. 1996), how did T2 occur in the Bohai Sea, and why did T2 have much larger influence than T3 which occurred at the beginning of MIS 5? To correlate regional environmental changes with global pattern and thus to detect the potential interaction between various driving factors on orbital timescales, three cores with a high recovery rate were drilled in the south Bohai Sea. This study was conducted following three perspectives: chronology (Yi et al. 2012b), sea-level change (Yi et al. 2012c) and paleoclimatology (Yi et al. 2012a), and the main results are as follows: 1. Chronology. Luminescence and radiocarbon dating methods were applied in dating these coastal/marine sediments: (1) For Holocene samples, most of the radiocarbon dates agree

  8. Global change and the measurement of absolute sea-level

    Science.gov (United States)

    Diamante, John M.; Pyle, Thomas E.; Carter, William E.; Scherer, Wolfgang

    To quantify properly the long-term response of sea-level to climate change, land motions must be separated from the apparent or relative sea-level change recorded by conventional tide/sea-level gauges. Here we present a concept for global measurement of the true or “absolute” sea-level change, which combines recent advances in space-based geodetic techniques with plans for a global sea-level network under the World Climate Research Programme (WCRP). Data from initial feasibility tests show that land motion, due to global (plate tectonic), regional (glacial rebound), or local (fluid withdrawal) effects, can probably be measured to ±1cm (on a single measurement basis) by an innovative combination of Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) tevhniques. By making repeated observations of position at a number of tide gauges using portable, economical GPS receivers in a differential mode relative to the fewer, more stable, but more expensive VLBI observatories, it will be possible to subtract land motion from the relative sea-level signal. Decadal to century scale trends at the 1-2mm y -1 level will be resolvable in the sea-level and vertical land motion time series within about a decade. Detection of subsidence or uplift at specific gauges will allow correction for land motion or deletion of bad data when computing regional or global, i.e. eustatic, sea-level changes. In addition to their applications in oceanography and climate studies, such data will test models by Peltier and other that relate mantle viscosity and deglaciation history to present rates of crustal subsidence or uplift. If the predicted crustal motions are confirmed, we can also have more confidence in the use of historical tide/sea-level gauge records in retrospective studies of sea-level change related to climate variability on decadal or longer time scales. It is concluded that as few as one-third (about 100) of the total number of tide/sea-level gauges (250

  9. Sea level change since 2005: importance of salinity

    Science.gov (United States)

    Llovel, W.; Purkey, S.; Meyssignac, B.; Kolodziejczyk, N.; Blazquez, A.; Bamber, J. L.

    2017-12-01

    Sea level rise is one of the most important consequences of the actual global warming. Global mean sea level has been rising at a faster rate since 1993 (over the satellite altimetry era) than previous decades. This rise is expected to accelerate over the coming decades and century. At global scale, sea level rise is caused by a combination of freshwater increase from land ice melting and land water changes (mass component) and ocean warming (thermal expansion). Estimating the causes is of great interest not only to understand the past sea level changes but also to validate projections based on climate models. In this study, we investigate the global mass contribution to recent sea level changes with an alternative approach by estimating the global ocean freshening. For that purpose, we consider the unprecedented amount of salinity measurements from Argo floats for the past decade (2005-2015). We compare our results to the ocean mass inferred by GRACE data and based on a sea level budget approach. Our results bring new constrains on the global water cycle (ocean freshening) and energy budget (ocean warming) as well as on the global ocean mass directly inferred from GRACE data.

  10. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    Science.gov (United States)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted swamp formation in

  11. Holocene Paleoceanographic Environments at the Chukchi-Alaskan Margin: Implications for Future Changes

    Science.gov (United States)

    Polyak, L.; Nam, S. I.; Dipre, G.; Kim, S. Y.; Ortiz, J. D.; Darby, D. A.

    2017-12-01

    The impacts of the North Pacific oceanic and atmospheric system on the Arctic Ocean result in accelerated sea-ice retreat and related changes in hydrography and biota in the western Arctic. Paleoclimatic records from the Pacific sector of the Arctic are key for understanding the long-term history of these interactions. As opposed to stratigraphically long but strongly compressed sediment cores recovered from the deep Arctic Ocean, sediment depocenters on the Chukchi-Alaskan margin yield continuous, medium to high resolution records formed since the last deglaciation. While early Holocene conditions were non-analogous to modern environments due to the effects of prolonged deglaciation and insufficiently high sea levels, mid to late Holocene sediments are more relevant for recent and modern climate variability. Notably, a large depocenter at the Alaskan margin has sedimentation rates estimated as high as a few millimeters per year, thus providing a decadal to near-annual resolution. This high accumulation can be explained by sediment delivery via the Alaskan Coastal Current originating from the Bering Sea and supposedly controlled by the Aleutian Low pressure center. Preliminary results from sediment cores recovering the last several centuries, along with a comparison with other paleoclimatic proxy records from the Arctic-North Pacific region, indicate a persistent role of the Aleutian Low in the Bering Strait inflow and attendant deposition. More proxy studies are underway to reconstruct the history of this circulation system and its relationship with sea ice extent. The expected results will improve our understanding of natural variability in oceanic and atmospheric conditions at the Chukchi-Alaskan margin, a critical area for modulating the Arctic climate change.

  12. Seychelles coral record of changes in sea surface temperature bimodality in the western Indian Ocean from the Mid-Holocene to the present

    Science.gov (United States)

    Zinke, J.; Pfeiffer, M.; Park, W.; Schneider, B.; Reuning, L.; Dullo, W.-Chr.; Camoin, G. F.; Mangini, A.; Schroeder-Ritzrau, A.; Garbe-Schönberg, D.; Davies, G. R.

    2014-08-01

    We report fossil coral records from the Seychelles comprising individual time slices of 14-20 sclerochronological years between 2 and 6.2 kyr BP to reconstruct changes in the seasonal cycle of western Indian Ocean sea surface temperature (SST) compared to the present (1990-2003). These reconstructions allowed us to link changes in the SST bimodality to orbital changes, which were causing a reorganization of the seasonal insolation pattern. Our results reveal the lowest seasonal SST range in the Mid-Holocene (6.2-5.2 kyr BP) and around 2 kyr BP, while the highest range is observed around 4.6 kyr BP and between 1990 and 2003. The season of maximum temperature shifts from austral spring (September to November) to austral autumn (March to May), following changes in seasonal insolation over the past 6 kyr. However, the changes in SST bimodality do not linearly follow the insolation seasonality. For example, the 5.2 and 6.2 kyr BP corals show only subtle SST differences in austral spring and autumn. We use paleoclimate simulations of a fully coupled atmosphere-ocean general circulation model to compare with proxy data for the Mid-Holocene around 6 kyr BP. The model results show that in the Mid-Holocene the austral winter and spring seasons in the western Indian Ocean were warmer while austral summer was cooler. This is qualitatively consistent with the coral data from 6.2 to 5.2 kyr BP, which shows a similar reduction in the seasonal amplitude compared to the present day. However, the pattern of the seasonal SST cycle in the model appears to follow the changes in insolation more directly than indicated by the corals. Our results highlight the importance of ocean-atmosphere interactions for Indian Ocean SST seasonality throughout the Holocene. In order to understand Holocene climate variability in the countries surrounding the Indian Ocean, we need a much more comprehensive analysis of seasonally resolved archives from the tropical Indian Ocean. Insolation data alone only

  13. Projecting twenty-first century regional sea-level changes

    NARCIS (Netherlands)

    Slangen, A.B.A.; Carson, M.; Katsman, C.A.; van de Wal, R.S.W.; Köhl, A.; Vermeersen, L.L.A.; Stammer, D.

    2014-01-01

    We present regional sea-level projections and associated uncertainty estimates for the end of the 21 (st) century. We show regional projections of sea-level change resulting from changing ocean circulation, increased heat uptake and atmospheric pressure in CMIP5 climate models. These are combined

  14. Sea level change: lessons from the geologic record

    Science.gov (United States)

    ,

    1995-01-01

    Rising sea level is potentially one of the most serious impacts of climatic change. Even a small sea level rise would have serious economic consequences because it would cause extensive damage to the world's coastal regions. Sea level can rise in the future because the ocean surface can expand due to warming and because polar ice sheets and mountain glaciers can melt, increasing the ocean's volume of water. Today, ice caps on Antarctica and Greenland contain 91 and 8 percent of the world's ice, respectively. The world's mountain glaciers together contain only about 1 percent. Melting all this ice would raise sea level about 80 meters. Although this extreme scenario is not expected, geologists know that sea level can rise and fall rapidly due to changing volume of ice on continents. For example, during the last ice age, about 18,000 years ago, continental ice sheets contained more than double the modem volume of ice. As ice sheets melted, sea level rose 2 to 3 meters per century, and possibly faster during certain times. During periods in which global climate was very warm, polar ice was reduced and sea level was higher than today.

  15. Geochemical record of Holocene to Recent sedimentation on the Western Indus continental shelf, Arabian Sea

    Science.gov (United States)

    Limmer, David R.; BöNing, Philipp; Giosan, Liviu; Ponton, Camilo; KöHler, Cornelia M.; Cooper, Matthew J.; Tabrez, Ali R.; Clift, Peter D.

    2012-01-01

    We present a multiproxy geochemical analysis of two cores recovered from the Indus Shelf spanning the Early Holocene to Recent (<14 ka). Indus-23 is located close to the modern Indus River, while Indus-10 is positioned ˜100 km further west. The Holocene transgression at Indus-10 was over a surface that was strongly weathered during the last glacial sea level lowstand. Lower Holocene sediments at Indus-10 have higherɛNdvalues compared to those at the river mouth indicating some sediment supply from the Makran coast, either during the deposition or via reworking of older sediments outcropping on the shelf. Sediment transport from Makran occurred during transgressive intervals when sea level crossed the mid shelf. The sediment flux from non-Indus sources to Indus-10 peaked between 11 ka and 8 ka. A hiatus at Indus-23 from 8 ka until 1.3 ka indicates non-deposition or erosion of existing Indus Shelf sequences. HigherɛNdvalues seen on the shelf compared to the delta imply reworking of older delta sediments in building Holocene clinoforms. Chemical Index of Alteration (CIA), Mg/Al and Sr isotopes are all affected by erosion of detrital carbonate, which reduced through the Holocene. K/Al data suggest that silicate weathering peaked ca. 4-6 ka and was higher at Indus-10 compared to Indus-23. Fine-grained sediments that make up the shelf have geochemical signatures that are different from the coarser grained bulk sediments measured in the delta plain. The Indus Shelf data highlight the complexity of reconstructing records of continental erosion and provenance in marine settings.

  16. Holocene environmental change along the southern Cape coast of South Africa - Insights from the Eilandvlei sediment record spanning the last 8.9 kyr

    Science.gov (United States)

    Wündsch, Michael; Haberzettl, Torsten; Cawthra, Hayley C.; Kirsten, Kelly L.; Quick, Lynne J.; Zabel, Matthias; Frenzel, Peter; Hahn, Annette; Baade, Jussi; Daut, Gerhard; Kasper, Thomas; Meadows, Michael E.; Mäusbacher, Roland

    2018-04-01

    This study investigates Holocene sediments from Eilandvlei, a coastal lake located within the Wilderness embayment at the southern Cape coast of South Africa. The evolution of the present estuarine/coastal lake system is reconstructed based on seismic data as well as a multi-proxy approach on a 30.5 m sediment core spanning the last 8.9 kyr. Geochemical (Ca, TOC/S, Br/TOC) and micropalaeontological data (diatoms, foraminifera) reflect changes in the degree of marine influence at the core site. The embayment likely developed via distinct phases of connectivity to the Indian Ocean caused by sea level changes and dune progradation. Marine conditions prevailed at the core site from 8900 to 4700 cal BP. The rapid sea level rise during the early Holocene caused the inundation of a palaeovalley that most likely had formed at lower sea levels during the Pleistocene. Towards the mid-Holocene the sea level exceeded its present height around 7500 cal BP creating a marine embayment. At 4700 cal BP, the embayment became distinctly more disconnected from the ocean turning into a lagoon system that persisted until 1200 cal BP. Subsequently, the marine influence further decreased and the present estuarine/coastal lake system was established. Grain size and geochemical data (Fe, Si/Al, chemical index of alteration (CIA)) further reflect changes in the deposition of terrigenous sediments at the core site. While the sedimentation of fine-grained (climatic conditions than today from 8900 to 7900 cal BP and 6400 to 3000 cal BP. In contrast, the periods between 7900-6400 cal BP and 3000 cal BP-present were likely characterized by high river discharge and thus, generally more rainfall. The reconstructed palaeoclimatic variations are discussed within the context of e.g., shifts in the position of the Antarctic sea ice extent and the mid-latitude westerly wind belt as well as changes in the El Niño-Southern Oscillation (ENSO).

  17. Holocene transgression of the Rhine river-mouth area, The Netherlands/Southern North Sea: palaeogeography and sequence stratigraphy

    NARCIS (Netherlands)

    Hijma, M.P.; Cohen, K.M.

    2011-01-01

    We present a detailed reconstruction of the palaeogeography of the Rhine valley (western Netherlands) during the Holocene transgression with systems tracts placed in a precise sea-level context. A high level of detail could be reached because of 1) favourable antecedent topography and subsidence

  18. Volcanic influence on centennial to millennial Holocene Greenland temperature change.

    Science.gov (United States)

    Kobashi, Takuro; Menviel, Laurie; Jeltsch-Thömmes, Aurich; Vinther, Bo M; Box, Jason E; Muscheler, Raimund; Nakaegawa, Toshiyuki; Pfister, Patrik L; Döring, Michael; Leuenberger, Markus; Wanner, Heinz; Ohmura, Atsumu

    2017-05-03

    Solar variability has been hypothesized to be a major driver of North Atlantic millennial-scale climate variations through the Holocene along with orbitally induced insolation change. However, another important climate driver, volcanic forcing has generally been underestimated prior to the past 2,500 years partly owing to the lack of proper proxy temperature records. Here, we reconstruct seasonally unbiased and physically constrained Greenland Summit temperatures over the Holocene using argon and nitrogen isotopes within trapped air in a Greenland ice core (GISP2). We show that a series of volcanic eruptions through the Holocene played an important role in driving centennial to millennial-scale temperature changes in Greenland. The reconstructed Greenland temperature exhibits significant millennial correlations with K + and Na + ions in the GISP2 ice core (proxies for atmospheric circulation patterns), and δ 18 O of Oman and Chinese Dongge cave stalagmites (proxies for monsoon activity), indicating that the reconstructed temperature contains hemispheric signals. Climate model simulations forced with the volcanic forcing further suggest that a series of large volcanic eruptions induced hemispheric-wide centennial to millennial-scale variability through ocean/sea-ice feedbacks. Therefore, we conclude that volcanic activity played a critical role in driving centennial to millennial-scale Holocene temperature variability in Greenland and likely beyond.

  19. Climate Sensitivity, Sea Level, and Atmospheric Carbon Dioxide

    Science.gov (United States)

    Hansen, James; Sato, Makiko; Russell, Gary; Kharecha, Pushker

    2013-01-01

    Cenozoic temperature, sea level and CO2 covariations provide insights into climate sensitivity to external forcings and sea-level sensitivity to climate change. Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise palaeoclimate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity of 3+/-1deg C for a 4 W/sq m CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial is less ambiguous and implies a sensitivity in the upper part of the above range, i.e. 3-4deg C for a 4 W/sq m CO2 forcing. Slow feedbacks, especially change of ice sheet size and atmospheric CO2, amplify the total Earth system sensitivity by an amount that depends on the time scale considered. Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated. We use a global model, simplified to essential processes, to investigate state dependence of climate sensitivity, finding an increased sensitivity towards warmer climates, as low cloud cover is diminished and increased water vapour elevates the tropopause. Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.

  20. Evaluating model simulations of 20th century sea-level rise. Part 1: global mean sea-level change

    NARCIS (Netherlands)

    Slangen, A.B.A.; Meyssignac, B.; Agosta, C.; Champollion, N.; Church, J.A.; Fettweis, X.; Ligtenberg, S.R.M.; Marzeion, B.; Melet, A.; Palmer, M.D.; Richter, K.; Roberts, C.D.; Spada, G.

    2017-01-01

    Sea level change is one of the major consequences of climate change and is projected to affect coastal communities around the world. Here, global mean sea level (GMSL) change estimated by 12 climate models from phase 5 of the World Climate Research Programme’s Climate Model Intercomparison Project

  1. Holocene North Atlantic Overturning in an atmosphere-ocean-sea-ice model compared to proxy-based reconstructions

    NARCIS (Netherlands)

    Blaschek, M.; Renssen, H.; Kissel, C.; Thornalley, D.

    2015-01-01

    Climate and ocean circulation in the North Atlantic region changed over the course of the Holocene, partly because of disintegrating ice sheets and partly because of an orbital-induced insolation trend. In the Nordic Seas, this impact was accompanied by a rather small, but significant, amount of

  2. Holocene reef development where wave energy reduces accommodation

    Science.gov (United States)

    Grossman, Eric E.; Fletcher, Charles H.

    2004-01-01

    Analyses of 32 drill cores obtained from the windward reef of Kailua Bay, Oahu, Hawaii, indicate that high wave energy significantly reduced accommodation space for reef development in the Holocene and produced variable architecture because of the combined influence of sea-level history and wave exposure over a complex antecedent topography. A paleostream valley within the late Pleistocene insular limestone shelf provided accommodation space for more than 11 m of vertical accretion since sea level flooded the bay 8000 yr BP. Virtually no net accretion (pile-up of fore-reef-derived rubble (rudstone) and sparse bindstone, and (3) a final stage of catch-up bindstone accretion in depths > 6 m. Coral framestone accreted at rates of 2.5-6.0 mm/yr in water depths > 11 m during the early Holocene; it abruptly terminated at ~4500 yr BP because of wave scour as sea level stabilized. More than 4 m of rudstone derived from the upper fore reef accreted at depths of 6 to 13 m below sea level between 4000 and 1500 yr BP coincident with late Holocene relative sea-level fall. Variations in the thickness, composition, and age of these reef facies across spatial scales of 10-1000 m within Kailua Bay illustrate the importance of antecedent topography and wave-related stress in reducing accommodation space for reef development set by sea level. Although accommodation space of 6 to 17 m has existed through most of the Holocene, the Kailua reef has been unable to catch up to sea level because of persistent high wave stress.

  3. Coupling of sea level and tidal range changes, with implications for future water levels.

    Science.gov (United States)

    Devlin, Adam T; Jay, David A; Talke, Stefan A; Zaron, Edward D; Pan, Jiayi; Lin, Hui

    2017-12-05

    Are perturbations to ocean tides correlated with changing sea-level and climate, and how will this affect high water levels? Here, we survey 152 tide gauges in the Pacific Ocean and South China Sea and statistically evaluate how the sum of the four largest tidal constituents, a proxy for the highest astronomical tide (HAT), changes over seasonal and interannual time scales. We find that the variability in HAT is significantly correlated with sea-level variability; approximately 35% of stations exhibit a greater than ±50 mm tidal change per meter sea-level fluctuation. Focusing on a subset of three stations with long records, probability density function (PDF) analyses of the 95% percentile exceedance of total sea level (TSL) show long-term changes of this high-water metric. At Hong Kong, the increase in tides significantly amplifies the risk caused by sea-level rise. Regions of tidal decrease and/or amplification highlight the non-linear response to sea-level variations, with the potential to amplify or mitigate against the increased flood risk caused by sea-level rise. Overall, our analysis suggests that in many regions, local flood level determinations should consider the joint effects of non-stationary tides and mean sea level (MSL) at multiple time scales.

  4. Holocene transgression of the Rhine river mouth area, The Netherlands/Southern North Sea: palaeogeography and sequence stratigraphy

    NARCIS (Netherlands)

    Cohen, K.M.; Hijma, M.P.

    2011-01-01

    This study presents a detailed reconstruction of the palaeogeography of the Rhine valley (western Netherlands) during the Holocene transgression with systems tracts placed in a precise sea-level context. This approach permits comparison of actual versus conceptual boundaries of the lowstand,

  5. Sea-level changes on multiple spatial scales: estimates and contributing processes

    NARCIS (Netherlands)

    Frederikse, T.

    2018-01-01

    Being one of the major consequences of anthropogenic climate change, sea level rise forms a threat for many coastal areas and their inhabitants. Because all processes that cause sea-level changes have a spatially-varying fingerprint, local sea-level changes deviate substantially from the global

  6. Instability of seawater pH in the South China Sea during the mid-late Holocene: Evidence from boron isotopic composition of corals

    Science.gov (United States)

    Liu, Yajing; Liu, W.; Peng, Z.; Xiao, Y.; Wei, G.; Sun, W.; He, J.; Liu, Gaisheng; Chou, C.-L.

    2009-01-01

    We used positive thermal ionization mass spectrometry (PTIMS) to generate high precision ??11B records in Porites corals of the mid-late Holocene from the South China Sea (SCS). The ??11B values of the Holocene corals vary significantly, ranging from 22.2??? to 25.5???. The paleo-pH records of the SCS, reconstructed from the ??11B data, were not stable as previously thought but show a gradual increase from the Holocene thermal optimal and a sharp decrease to modern values. The latter is likely caused by the large amount of anthropogenic CO2 emissions since the Industrial Revolution but variations of atmospheric pCO2 cannot explain the pH change of the SCS before the Industrial Revolution. We suggest that variations of monsoon intensity during the mid-late Holocene may have driven the sea surface pH increase from the mid to late Holocene. Results of this study indicate that the impact of anthropogenic atmospheric CO2 emissions may have reversed the natural pH trend in the SCS since the mid-Holocene. Such ocean pH records in the current interglacial period can help us better understand the physical and biological controls on ocean pH and possibly predict the long-term impact of climate change on future ocean acidification. ?? 2008 Elsevier Ltd. All rights reserved.

  7. Past and future changes in extreme sea levels and waves

    Digital Repository Service at National Institute of Oceanography (India)

    Lawe, J.A.; Woodworth, P.L.; Knutson, T.; McDonald, R.E.; Mclnnes, K.L.; Woth, K.; Von Storch, H.; Wolf, J.; Swail, V.; Bernier, N.B.; Gulev, S.; Horsburgh, K.J.; Unnikrishnan, A.S.; Hunter, J.R.; Weisse, R.

    of Extreme Sea Level 11.3.1 An Introduction to Storms Both mid-latitude and tropical storms are associated with extremes of sea level. Storm surges are generated by low atmospheric pressure and intense winds over the ocean. The latter also cause high wave... timescales, extremes and mean-sea-level change are both major factors in determining coastal evolution including the development of coastal ecosystems. It will be seen below that, although it is difficult to determine how mean sea level has changed...

  8. Land uplift and relative sea-level changes in the Loviisa area, southeastern Finland, during the last 8000 years

    International Nuclear Information System (INIS)

    Miettinen, A.; Eronen, M.; Hyvaerinen, H.

    1999-09-01

    Southeastern Finland belongs to the area covered by the Weichselian ice sheet, where the release of the ice load caused a rapid isostatic rebound during the postglacial time. While the mean overall apparent uplift is of the order of 2 mm/yr today, in the early Holocene time it was several times higher. A marked decrease in the rebound rate occurred around 8500 BP, however, since then the uplift rate has remained high until today, with a slightly decreasing trend towards the present time. According to current understanding there have neither been temporary increases nor decreases in the rate of uplift during the postglacial time. Even so, it is not known for sure whether there are regional irregularities on the rebound in Finland. Concurrently with land uplift, relative sea-level changes in the Baltic basin were also strongly affected by the global eustatic rise of sea-level. During the early Litorina Sea stage on the southern coast of Finland around 7000 BP, the rise in sea-level exceeded the rate of land uplift, and resulted in a short-lived transgression. The most accurate information on relative sea-level changes in an uplifting area may be obtained from radiocarbon dated events of isolation in small lake basins, as they were cut off from larger bodies of water. The isolations of such basins from the sea may be reliably determined by the recorded changes in the diatom flora in the sediment sequences, at horizons which may be radiometrically dated. In the present study, the isolation-horizons of 13 basins were dated by 26 conventional and 2 AMS radiocarbon dates. According to the available sets of dates, the time span of emergence extends from 8300 BP to the past few hundred years, for lakes from c. 30 m to 1.1 m above the present sea-level. Due to the global rise in sea-level, during the period of 7500-6500 BP, the sea-level rise clearly exceeded the rate of uplift, and resulted in the Litorina transgression, which had an amplitude of around one metre. The

  9. Land uplift and relative sea-level changes in the Loviisa area, southeastern Finland, during the last 8000 years

    Energy Technology Data Exchange (ETDEWEB)

    Miettinen, A.; Eronen, M.; Hyvaerinen, H. [Helsinki Univ. (Finland). Dept. of Geology

    1999-09-01

    Southeastern Finland belongs to the area covered by the Weichselian ice sheet, where the release of the ice load caused a rapid isostatic rebound during the postglacial time. While the mean overall apparent uplift is of the order of 2 mm/yr today, in the early Holocene time it was several times higher. A marked decrease in the rebound rate occurred around 8500 BP, however, since then the uplift rate has remained high until today, with a slightly decreasing trend towards the present time. According to current understanding there have neither been temporary increases nor decreases in the rate of uplift during the postglacial time. Even so, it is not known for sure whether there are regional irregularities on the rebound in Finland. Concurrently with land uplift, relative sea-level changes in the Baltic basin were also strongly affected by the global eustatic rise of sea-level. During the early Litorina Sea stage on the southern coast of Finland around 7000 BP, the rise in sea-level exceeded the rate of land uplift, and resulted in a short-lived transgression. The most accurate information on relative sea-level changes in an uplifting area may be obtained from radiocarbon dated events of isolation in small lake basins, as they were cut off from larger bodies of water. The isolations of such basins from the sea may be reliably determined by the recorded changes in the diatom flora in the sediment sequences, at horizons which may be radiometrically dated. In the present study, the isolation-horizons of 13 basins were dated by 26 conventional and 2 AMS radiocarbon dates. According to the available sets of dates, the time span of emergence extends from 8300 BP to the past few hundred years, for lakes from c. 30 m to 1.1 m above the present sea-level. Due to the global rise in sea-level, during the period of 7500-6500 BP, the sea-level rise clearly exceeded the rate of uplift, and resulted in the Litorina transgression, which had an amplitude of around one metre. The

  10. Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska

    Science.gov (United States)

    Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Jones, Benjamin M.; Wiles, Gregory C.; Groves, Pamela; Kunz, Michael L.; Baughman, Carson A.; Reanier, Richard E.

    2017-08-01

    Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500-7500 calibrated 14C years before present; 13.5-7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owc values from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9-11.7 ka), and the Holocene Thermal Maximum (11.7-9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar

  11. Changes in extreme regional sea level under global warming

    NARCIS (Netherlands)

    Brunnabend, S. E.; Dijkstra, H. A.; Kliphuis, Michael; Bal, Henri E.; Seinstra, Frank J.; van Werkhoven, Ben; Maassen, J.; van Meersbergen, Maarten

    2017-01-01

    An important contribution to future changes in regional sea level extremes is due to the changes in intrinsic ocean variability, in particular ocean eddies. Here, we study a scenario of future dynamic sea level (DSL) extremes using a high-resolution version of the Parallel Ocean Program and

  12. Modelling and simulation of Holocene marine terrace development in Boso Peninsula, central Japan

    Science.gov (United States)

    Noda, Akemi; Miyauchi, Takahiro; Sato, Toshinori; Matsu'ura, Mitsuhiro

    2018-04-01

    In the southern part of Boso Peninsula, central Japan, we can observe a series of well-developed Holocene marine terraces. We modeled the development of these marine terraces by considering sea-level fluctuation and steady land uplift. The evolution of coastal landform is generally described as follows: altitude change = - erosion + deposition - sea-level rise + land uplift. In this study, the erosion rate is supposed to be proportional to the dissipation rate of wave energy, and the deposition rate of eroded materials to decay exponentially as they are transported seaward. The rate of sea-level rise is given by the time derivative of a sea-level curve obtained from the sediment core records of oxygen isotope ratios. Steady plate subduction generally brings about steady crustal uplift/subsidence independently of earthquake occurrence, and so the land-uplift rate is regarded as time independent on a long-term average. Our simulation results show that a pair of sea cliff and abrasion platform is efficiently formed about a stationary point of the sea-level curve. The Holocene sea-level curve has four peaks and three troughs, and so basically seven terraces are formed one by one during the past 10,000 yr. However, when the land-uplift rate is low, most of the terraces formed at older times sink in the sea. When the land-uplift rate is high, the overlap and/or reverse of older and younger terraces occur frequently, and so the correspondence between the age and present altitude of terraces is not necessarily one-to-one. Taking the land-uplift rate to be 3-4 mm/yr, we can reproduce a series of well-developed Holocene marine terraces in Boso Peninsula independently of coseismic uplifts. From these simulation results, we may conclude that the Holocene marine terraces in Boso Peninsula were developed as a result of the composite process of sea-level fluctuation and steady coastal uplift.

  13. Portrait of a Warming Ocean and Rising Sea Levels: Trend of Sea Level Change 1993-2008

    Science.gov (United States)

    2008-01-01

    Warming water and melting land ice have raised global mean sea level 4.5 centimeters (1.7 inches) from 1993 to 2008. But the rise is by no means uniform. This image, created with sea surface height data from the Topex/Poseidon and Jason-1 satellites, shows exactly where sea level has changed during this time and how quickly these changes have occurred. It's also a road map showing where the ocean currently stores the growing amount of heat it is absorbing from Earth's atmosphere and the heat it receives directly from the Sun. The warmer the water, the higher the sea surface rises. The location of heat in the ocean and its movement around the globe play a pivotal role in Earth's climate. Light blue indicates areas in which sea level has remained relatively constant since 1993. White, red, and yellow are regions where sea levels have risen the most rapidly up to 10 millimeters per year and which contain the most heat. Green areas have also risen, but more moderately. Purple and dark blue show where sea levels have dropped, due to cooler water. The dramatic variation in sea surface heights and heat content across the ocean are due to winds, currents and long-term changes in patterns of circulation. From 1993 to 2008, the largest area of rapidly rising sea levels and the greatest concentration of heat has been in the Pacific, which now shows the characteristics of the Pacific Decadal Oscillation (PDO), a feature that can last 10 to 20 years or even longer. In this 'cool' phase, the PDO appears as a horseshoe-shaped pattern of warm water in the Western Pacific reaching from the far north to the Southern Ocean enclosing a large wedge of cool water with low sea surface heights in the eastern Pacific. This ocean/climate phenomenon may be caused by wind-driven Rossby waves. Thousands of kilometers long, these waves move from east to west on either side of the equator changing the distribution of water mass and heat. This image of sea level trend also reveals a significant

  14. Sea level report

    International Nuclear Information System (INIS)

    Schwartz, M.L.

    1979-01-01

    Study of Cenozoic Era sea levels shows a continual lowering of sea level through the Tertiary Period. This overall drop in sea level accompanied the Pleistocene Epoch glacio-eustatic fluctuations. The considerable change of Pleistocene Epoch sea level is most directly attributable to the glacio-eustatic factor, with a time span of 10 5 years and an amplitude or range of approximately 200 m. The lowering of sea level since the end of the Cretaceous Period is attributed to subsidence and mid-ocean ridges. The maximum rate for sea level change is 4 cm/y. At present, mean sea level is rising at about 3 to 4 mm/y. Glacio-eustacy and tectono-eustacy are the parameters for predicting sea level changes in the next 1 my. Glacio-eustatic sea level changes may be projected on the basis of the Milankovitch Theory. Predictions about tectono-eustatic sea level changes, however, involve predictions about future tectonic activity and are therefore somewhat difficult to make. Coastal erosion and sedimentation are affected by changes in sea level. Erosion rates for soft sediments may be as much as 50 m/y. The maximum sedimentation accumulation rate is 20 m/100 y

  15. Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

    Science.gov (United States)

    Cronin, Thomas M.; O'Regan, Matt; Pearce, Christof; Gemery, Laura; Toomey, Michael; Semiletov, Igor; Jakobsson, Martin

    2017-09-01

    Deglacial (12.8-10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM; ˜ 24 kiloannum or ka) minimum sea level of ˜ 125-130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ˜ 400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42-47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

  16. Holocene emerged coral reef in Takarajima and Kodakarajima, Ryukyu islands, Southwest Japan

    International Nuclear Information System (INIS)

    Nakata, Takashi; Omoto, Kunio; Koba, Motoharu

    1978-01-01

    Due to the recent development of radiometric dating, coral reefs emerged in Holocene epoch are studied intensively worldwidely in relation to sea level change and coral reef formation. Attempt was made to determine the age, pattern and growth rate of coral reefs in the marginal area of coral sea in the Northwest Pacific. Field observation was made in the emerged coral reefs in Takarajima and Kodakarajima islands and the samples for radiocarbon dating were taken from geological sections across the emerged reefs. These islands are located at about 29 deg 10 min N, 129 deg 15 min E, where warm Kuroshio current pushes the margin of coral sea northward, and furnished with flourishing development of coral reefs emerged in both pleistocence and Holocene epochs. Though without earthquake records, it is assumed that Holocene reefs have been terraced due to sudden uplift associated with major earthquakes. (Mori, K.)

  17. Holocene emerged coral reef in Takarajima and Kodakarajima, Ryukyu islands, Southwest Japan

    Energy Technology Data Exchange (ETDEWEB)

    Nakata, T; Omoto, K; Koba, M [Tohoku Univ., Sendai (Japan). Faculty of Science

    1978-06-01

    Due to the recent development of radiometric dating, coral reefs emerged in Holocene epoch are studied intensively worldwidely in relation to sea level change and coral reef formation. Attempt was made to determine the age, pattern and growth rate of coral reefs in the marginal area of coral sea in the Northwest Pacific. Field observation was made in the emerged coral reefs in Takarajima and Kodakarajima islands and the samples for radiocarbon dating were taken from geological sections across the emerged reefs. These islands are located at about 29 deg 10 min N, 129 deg 15 min E, where warm Kuroshio current pushes the margin of coral sea northward, and furnished with flourishing development of coral reefs emerged in both pleistocence and Holocene epochs. Though without earthquake records, it is assumed that Holocene reefs have been terraced due to sudden uplift associated with major earthquakes.

  18. Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska

    Science.gov (United States)

    Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Jones, Benjamin M.; Wiles, Gregory C.; Groves, Pamela; Kunz, Michael L.; Baughman, Carson; Reanier, Richard E.

    2017-01-01

    Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500–7500 calibrated 14C years before present; 13.5–7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owcvalues from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9–11.7 ka), and the Holocene Thermal Maximum (11.7–9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by seaice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are

  19. Sea level and global ice volumes from the Last Glacial Maximum to the Holocene.

    Science.gov (United States)

    Lambeck, Kurt; Rouby, Hélène; Purcell, Anthony; Sun, Yiying; Sambridge, Malcolm

    2014-10-28

    The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet's dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ∼40 m in sea level, the main phase of deglaciation occurred from ∼16.5 ka BP to ∼8.2 ka BP at an average rate of rise of 12 m⋅ka(-1) punctuated by periods of greater, particularly at 14.5-14.0 ka BP at ≥40 mm⋅y(-1) (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ∼11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ∼2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100-150 y ago, with no evidence of oscillations exceeding ∼15-20 cm in time intervals ≥200 y from 6 to 0.15 ka BP.

  20. Holocene Evolution of Qing'ao Embayment, Southern China

    Science.gov (United States)

    Switzer, A. D.; Yu, F.; Chen, B.; Zheng, Z.; Wang, D.

    2012-12-01

    The Holocene evolution of the Qing'ao embayment, Nan'ao Island, southern China, is primarily the result of the interaction of tectonic activity, climate variation and changes in relative sea level. Characterizing the evolutionary history of the relatively small Qing'ao embayment during the Holocene will help improve our understanding of the driving mechanisms of coastal evolution in the area. To reconstruct the Holocene evolution history we analyzed the grain size, loss on ignition (LOI) and carbonate content of modern and core samples. Modern environmental analogs were examined in surface samples ranging from the coastal sand dunes through to offshore. The results of these modern samples suggest that dune sand (mean size of ~2.33Phi) are slightly finer than beach sand (mean size of 2.13Phi), and nearshore sediment is much coarser than offshore sediment (mean size of 5.90Phi). This modern analogs were then applied to 8 percussion cores from the Qing'ao embayment. A chronological framework obtained from 11 radiocarbon samples suggests that the embayment started to accept deposition since early Holocene, ~8500 cal. yr. BP. Three main phases of Holocene evolution were identified. A basin wide shell-rich sand sheet forms the basal Holocene facies and overlies clay rich presumably Pleistocene sediments or bedrock. This facies records an initial sedimentation phase associated with the early Holocene transgression into the embayment (~8500-6000 cal. yr. BP). The basal facies grades upward to a mixed sandy-mud facies which includes lagoonal clayey-silts, flood tide delta sands and records an estuarine phase lasting from ~6000-1000 cal. yr. BP that appears coincident with falling regional sea levels. Coincident with the estuarine phase is a period of coastal dune building recorded as yet undated massive sands that are found in the upper fill. Toward the end of the estuarine phase it is apparent that dune migration has restricted the lagoon entrance and that this was

  1. Holocene climate variability and oceanographic changes off western South Africa

    Science.gov (United States)

    Zhao, Xueqin; Dupont, Lydie; E Meadows, Michael; Schefuß, Enno; Bouimetarhan, Ilham; Wefer, Gerold

    2017-04-01

    and nutrient-rich waters with active upwelling. Thus, sea surface temperatures are dominated by upwelling dynamics influenced by the latitudinal position of the southern westerlies rather than warm waters via the Agulhas leakage. The paleo-productivity changes during the late Holocene are controlled by the freshwater influx of the Orange River indicated by abundant fluvial-related taxa such as Brigantedinium spp., Protoperidinium americanum and Lejeunecysta oliva. This corroborates the increase of Poaceae/Asteraceae ratio suggesting increased summer rainfall in the SRZ. Therefore, the terrestrial (pollen) and marine (dinoflagellate cyst) records generated from the same sediment sequence enable a clear understanding of the mechanisms driving variability in the Holocene of South Africa and provide significant insight into the land-ocean linkages.

  2. Modelling regional sea-level changes in recent past and future

    NARCIS (Netherlands)

    Slangen, A.B.A.

    2012-01-01

    Sea-level change is one of the most important consequences of a warming climate, affecting many densely populated coastal communities. To improve coastal management and the planning of flood defences, information on the future development of sea-level rise is needed. However, sea-level rise is not

  3. Impacts of Sea-Level Rise and Human Activity on a Tropical Continental Shelf, RN State, NE Brazil

    Science.gov (United States)

    Vital, H.; Barros Pereira, T. R.; Lira, H. F.; Tabosa, W. F.; Eichler, P.; Stattegger, K.; Sen Gupta, B. K.; Gomes, M. P.; Nogueira, M. L. D. S.; Pierri, G. C. S.

    2014-12-01

    The northeastern Brazilian, tropical coast-shelf system along the Atlantic Ocean is a sediment-starved zone, because of low relief, small drainage basins, and a semiarid climate. This work presents the major results of a study of environmental changes, particularly those related to Holocene sea-level rise, affecting the coast and shallow waters of Rio Grande do Norte (RN) State, NE Brazil. The methods included bottom-sediment characterization, bioindicator tracking, and integrated shallow-water geophysical investigation. This coastline is marked by active sea cliffs carved into tablelands alternating with reef- or dune-barrier sections, beach rocks and lagoons, whereas the shelf is a narrow, very shallow, and highly energetic system. Overall, the area is under the natural influence of tides (with a semidiurnal mesotidal regime) and the anthropogenic influence of salt exploration, oil industry, shrimp farms, tourism, and wind-farms. Sedimentation during the Holocene has been controlled mainly by sea-level variation, longshore currents, and the advance and westward propagation of active dunes along the coast. As in other areas around the world, growing numbers of permanent and seasonal residents choose to live at or near the ocean. Coastal erosion is a cause for concern along many Brazilian beaches, and several erosion hot spots are already recognized in RN State. Curves of Holocene relative sea-level variation were established for RN State, but the absence of long-term oceanographic observations in the last centuries or that of detailed altimetry maps hinders the evaluation of different risk scenarios at the local level. Nevertheless, impacts of the current sea-level rise and human activity can be observed along the RN coastal-shelf system. Particular aspects of the study, such as oil-spill monitoring, coastal-water sewage contamination, and coastal erosion, will be highlighted.

  4. Sea-level rise caused by climate change and its implications for society

    Science.gov (United States)

    MIMURA, Nobuo

    2013-01-01

    Sea-level rise is a major effect of climate change. It has drawn international attention, because higher sea levels in the future would cause serious impacts in various parts of the world. There are questions associated with sea-level rise which science needs to answer. To what extent did climate change contribute to sea-level rise in the past? How much will global mean sea level increase in the future? How serious are the impacts of the anticipated sea-level rise likely to be, and can human society respond to them? This paper aims to answer these questions through a comprehensive review of the relevant literature. First, the present status of observed sea-level rise, analyses of its causes, and future projections are summarized. Then the impacts are examined along with other consequences of climate change, from both global and Japanese perspectives. Finally, responses to adverse impacts will be discussed in order to clarify the implications of the sea-level rise issue for human society. PMID:23883609

  5. Sea ice and wind variability during the Holocene in East Antarctica: Insight on middle high latitude coupling

    NARCIS (Netherlands)

    Denis, D.; Crosta, X.; Barbera, L.; Masse, G.; Renssen, H.; Ther, O.; Giraudeau, J.

    2010-01-01

    Micropaleontological and biomarker data from two high-accumulation marine sites from the Coastal and Continental Shelf Zone (CCSZ) off East Antarctica (Adélie Land at ∼140°E and eastern Prydz Bay at ∼77°E) are used to reconstruct Holocene changes in sea ice and wind stress at the basin-wide scale.

  6. Quantitative estimation of Holocene surface salinity variation in the Black Sea using dinoflagellate cyst process length

    DEFF Research Database (Denmark)

    Mertens, Kenneth Neil; Bradley, Lee R.; Takano, Yoshihito

    2012-01-01

    Reconstruction of salinity in the Holocene Black Sea has been an ongoing debate over the past four decades. Here we calibrate summer surface water salinity in the Black Sea, Sea of Azov and Caspian Sea with the process length of the dinoflagellate cyst Lingulodinium machaerophorum. We then apply ...

  7. The Influence of Sediment Isostatic Adjustment on Sea Level Change and Land Motion Along the U.S. Gulf Coast

    Science.gov (United States)

    Kuchar, Joseph; Milne, Glenn; Wolstencroft, Martin; Love, Ryan; Tarasov, Lev; Hijma, Marc

    2018-01-01

    Sea level rise presents a hazard for coastal populations, and the Mississippi Delta (MD) is a region particularly at risk due to the high rates of land subsidence. We apply a gravitationally self-consistent model of glacial and sediment isostatic adjustment (SIA) along with a realistic sediment load reconstruction in this region for the first time to determine isostatic contributions to relative sea level (RSL) and land motion. We determine optimal model parameters (Earth rheology and ice history) using a new high-quality compaction-free sea level indicator database. Using the optimal model parameters, we show that SIA can lower predicted RSL in the MD area by several meters over the Holocene and so should be taken into account when modeling these data. We compare modeled contemporary rates of vertical land motion with those inferred using GPS. This comparison indicates that isostatic processes can explain the majority of the observed vertical land motion north of latitude 30.7°N, where subsidence rates average about 1 mm/yr; however, subsidence south of this latitude shows large data-model discrepancies of greater than 3 mm/yr, indicating the importance of nonisostatic processes. This discrepancy extends to contemporary RSL change, where we find that the SIA contribution in the Delta is on the order of 10-1 mm/yr. We provide estimates of the isostatic contributions to 20th and 21st century sea level rates at Gulf Coast Permanent Service for Mean Sea Level tide gauge locations as well as vertical and horizontal land motion at GPS station locations near the MD.

  8. IODP Expedition 310 Reconstructs Sea Level, Climatic, and Environmental Changes in the South Pacific during the Last Deglaciation

    Directory of Open Access Journals (Sweden)

    Yasufumi Iryu

    2007-07-01

    Full Text Available The timing and course of the last deglaciation (19,000–6,000 years BP are essential components for understanding the dynamics of large ice sheets (Lindstrom and MacAyeal, 1993 and their effects on Earth’s isostasy (Nakada and Lambeck, 1989; Lambeck, 1993; Peltier, 1994, as well as the complex relationship between freshwater fluxes to the ocean, thermohaline circulation, and, hence, global climate during the Late Pleistocene and the Holocene. Moreover, the lastdeglaciation is generally seen as a possible analogue for the environmental changes and increased sea level that Earth may experience because of the greenhouse effect, related thermal expansion of oceans, and the melting of polar ice sheets.

  9. Contributions of a Strengthened Early Holocene Monsoon and Sediment Loading to Present-Day Subsidence of the Ganges-Brahmaputra Delta

    Science.gov (United States)

    Karpytchev, M.; Ballu, V.; Krien, Y.; Becker, M.; Goodbred, S.; Spada, G.; Calmant, S.; Shum, C. K.; Khan, Z.

    2018-02-01

    The contribution of subsidence to relative sea level rise in the Ganges-Brahmaputra delta (GBD) is largely unknown and may considerably enhance exposure of the Bengal Basin populations to sea level rise and storm surges. This paper focuses on estimating the present-day subsidence induced by Holocene sediment in the Bengal Basin and by oceanic loading due to eustatic sea level rise over the past 18 kyr. Using a viscoelastic Earth model and sediment deposition history based on in situ measurements, results suggest that massive sediment influx initiated in the early Holocene under a strengthened South Asian monsoon may have contributed significantly to the present-day subsidence of the GBD. We estimate that the Holocene loading generates up to 1.6 mm/yr of the present-day subsidence along the GBD coast, depending on the rheological model of the Earth. This rate is close to the twentieth century global mean sea level rise (1.1-1.7 mm/yr). Thus, past climate change, by way of enhanced sedimentation, is impacting vulnerability of the GBD populations.

  10. Sources and characteristics of terrestrial carbon in Holocene-scale sediments of the East Siberian Sea

    Science.gov (United States)

    Keskitalo, Kirsi; Tesi, Tommaso; Bröder, Lisa; Andersson, August; Pearce, Christof; Sköld, Martin; Semiletov, Igor P.; Dudarev, Oleg V.; Gustafsson, Örjan

    2017-09-01

    Thawing of permafrost carbon (PF-C) due to climate warming can remobilise considerable amounts of terrestrial carbon from its long-term storage to the marine environment. PF-C can be then be buried in sediments or remineralised to CO2 with implications for the carbon-climate feedback. Studying historical sediment records during past natural climate changes can help us to understand the response of permafrost to current climate warming. In this study, two sediment cores collected from the East Siberian Sea were used to study terrestrial organic carbon sources, composition and degradation during the past ˜ 9500 cal yrs BP. CuO-derived lignin and cutin products (i.e., compounds solely biosynthesised in terrestrial plants) combined with δ13C suggest that there was a higher input of terrestrial organic carbon to the East Siberian Sea between ˜ 9500 and 8200 cal yrs BP than in all later periods. This high input was likely caused by marine transgression and permafrost destabilisation in the early Holocene climatic optimum. Based on source apportionment modelling using dual-carbon isotope (Δ14C, δ13C) data, coastal erosion releasing old Pleistocene permafrost carbon was identified as a significant source of organic matter translocated to the East Siberian Sea during the Holocene.

  11. Sea-level rise caused by climate change and its implications for society.

    Science.gov (United States)

    Mimura, Nobuo

    2013-01-01

    Sea-level rise is a major effect of climate change. It has drawn international attention, because higher sea levels in the future would cause serious impacts in various parts of the world. There are questions associated with sea-level rise which science needs to answer. To what extent did climate change contribute to sea-level rise in the past? How much will global mean sea level increase in the future? How serious are the impacts of the anticipated sea-level rise likely to be, and can human society respond to them? This paper aims to answer these questions through a comprehensive review of the relevant literature. First, the present status of observed sea-level rise, analyses of its causes, and future projections are summarized. Then the impacts are examined along with other consequences of climate change, from both global and Japanese perspectives. Finally, responses to adverse impacts will be discussed in order to clarify the implications of the sea-level rise issue for human society.(Communicated by Kiyoshi HORIKAWA, M.J.A.).

  12. Late-Holocene environment and climatic changes in Ameralik Fjord, southwest Greenland: evidence from the sedimentary record

    DEFF Research Database (Denmark)

    Møller, Henrik S.; Jensen, Karin G.; Kuijpers, Antoon

    2006-01-01

      Sedimentological and geochemical (XRF) data together with information from diatom and benthic foraminifera records of a 3.5 m long gravity core from Ameralik fjord, southern West Greenland, is used for reconstructing late Holocene environmental changes in this area. The changes are linked...... to large-scale North Atlantic ocean and climate variability. AMS 14C-dating of benthic foraminifera indicates that the sediment core covers the last 4400 years and may include the termination of the Holocene Thermal Maximum (HTM). The late HTM (4.4-3.2 ka BP) is characterized by high accumulation rates...... conditions were further characterised by limited sea ice probably related to a mild and relatively windy winter climate. After 3.2 ka BP lower fine-grained sedimentation rates, but a larger input from sea-ice rafted or aeolian coarse material prevailed. This can be related to colder atmospheric conditions...

  13. Simultaneous estimation of lithospheric uplift rates and absolute sea level change in southwest Scandinavia from inversion of sea level data

    DEFF Research Database (Denmark)

    Nielsen, Lars; Hansen, Jens Morten; Hede, Mikkel Ulfeldt

    2014-01-01

    the relative sea level data. Similar independent data do not exist for ancient times. The purpose of this study is to test two simple inversion approaches for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates for ancient times in areas where a dense coverage of relative...... sea level data exists and well-constrained average lithospheric movement values are known from, for example glacial isostatic adjustment (GIA) models. The inversion approaches are tested and used for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates in southwest...... Scandinavia from modern relative sea level data series that cover the period from 1900 to 2000. In both approaches, a priori information is required to solve the inverse problem. A priori information about the average vertical lithospheric movement in the area of interest is critical for the quality...

  14. Guiding Users to Sea Level Change Data Through Content

    Science.gov (United States)

    Quach, N.; Abercrombie, S. P.; Boening, C.; Brennan, H. P.; Gill, K. M.; Greguska, F. R., III; Huang, T.; Jackson, R.; Larour, E. Y.; Shaftel, H.; Tenenbaum, L. F.; Zlotnicki, V.; Boeck, A.; Moore, B.; Moore, J.

    2017-12-01

    The NASA Sea Level Change Portal (https://sealevel.nasa.gov) is an immersive and innovative web portal for sea level change research that addresses the needs of diverse audiences, from scientists across disparate disciplines to the general public to policy makers and businesses. Since sea level change research involves vast amounts of data from multiple fields, it becomes increasingly important to come up with novel and effective ways to guide users to the data they need. News articles published on the portal contains links to relevant data. The Missions section highlights missions and projects as well as provide a logical grouping of the data. Tools available on the portal, such as the Data Analysis Tool, a data visualization and high-performance environment for sea level analysis, and the Virtual Earth System Laboratory, a 3D simulation application, describes and links to the source data. With over 30K Facebook followers and over 23K Twitter follower, the portal outreach team also leverages social media to guide users to relevant data. This presentation focuses on how the portal uses news articles, mission and project pages, tools, and social media to connect users to the data.

  15. Holocene environmental and parasequence development of the St. Jones Estuary, Delaware (USA): Foraminiferal proxies of natural climatic and anthropogenic change

    Science.gov (United States)

    Leorri, E.; Martin, R.; McLaughlin, P.

    2006-01-01

    The benthic foraminiferal record of marshes located along western Delaware Bay (St. Jones Estuary, USA) reflects the response of estuaries to sea-level and paleoclimate change during the Holocene. System tracts are recognized and within them parasequences based on sedimentological and foraminiferal assemblages identification. The parasequences defined by foraminiferal assemblages appear correlative with rapid Holocene climate changes that are of worldwide significance: 6000-5000, 4200-3800, 3500-2500, 1200-1000, and 600??cal years BP. Following postglacial sea-level rise, modern subestuaries and marshes in the region began to develop between 6000 and 4000??years BP, depending on their proximity to the mouth of Delaware Bay and coastal geomorphology. Initial sediments were fluvial in origin, with freshwater marshes established around 4000??years BP. The subsequent sea-level transgression occurred sufficiently slowly that freshwater marshes alternated with salt marshes at the same sites to around 3000??years BP. Locally another two transgressions are identified at 1800 and 1000??years BP respectively. Marine influence increased in the estuaries until 600??years BP (Little Ice Age), when regression occurred. Sea-level began to rise again during the mid-19th Century at the end of the Little Ice Age, when marshes became established. The presence of a sand lens in the upper and middle estuary and the reduction in the number of tests in the top samples in cores from the same area also suggest an anthropogenic influence. The estuary infill resulted in a sharp transgressive sequence, represented by salt marsh foraminiferal assemblages in the upper part of the cores. The increase in marsh foraminifera in both areas suggests an increase in marine influence that might be due to the transgression beginning at the end of the Little Ice Age about 150-180??years ago coupled with anthropogenic straightening of the channel in 1913. ?? 2006 Elsevier B.V. All rights reserved.

  16. Sea level change along the Black Sea coast from satellite altimetry, tide gauge and GPS observations

    Directory of Open Access Journals (Sweden)

    Nevin B. Avsar

    2016-01-01

    Full Text Available Sea level change affects human living conditions, particularly ocean coasts. However, sea level change is still unclear along the Black Sea coast due to lack of in-situ measurements and low resolution satellite data. In this paper, sea level change along the Black Sea coast is investigated from joint satellite altimetry, tide gauge (TG and Global Positioning System (GPS observations. The linear trend and seasonal components of sea level change are estimated at 8 TG stations (Amasra, Igneada, Trabzon-II, Sinop, Sile, Poti, Tuapse, and Batumi located along the Black Sea coast, which are compared with Satellite Altimetry and GPS. At the tide gauge stations with long-term records such as Poti (about 21 years and Tuapse (about 19 years, the results obtained from the satellite altimetry and tide gauge observations show a remarkably good agreement. While some big differences are existed between Satellite Altimetry and TG at other stations, after adding vertical motion from GPS, correlation coefficients of the trend have been greatly improved from 0.37 to 0.99 at 3 co-located GPS and TG stations (Trabzon-II, Sinop and Sile.

  17. Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

    Science.gov (United States)

    Cronin, Thomas M.; O'Regan, Matt; Pearce, Christof; Gemery, Laura; Toomey, Michael; Semiletov, Igor

    2017-01-01

    Deglacial (12.8–10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM;  ∼  24 kiloannum or ka) minimum sea level of  ∼  125–130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ∼  400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42–47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

  18. Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

    Directory of Open Access Journals (Sweden)

    T. M. Cronin

    2017-09-01

    Full Text Available Deglacial (12.8–10.7 ka sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1 and multicore SWERUS-L2-4-MC1 (4-MC1, and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1. Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM;  ∼  24 kiloannum or ka minimum sea level of  ∼  125–130 meters below sea level (m b.s.l.. Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1 followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ∼  400 cm of core depth is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42–47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

  19. Multidecadal variations in the early Holocene outflow of Red Sea Water into the Arabian Sea

    NARCIS (Netherlands)

    Jung, S.J.A.; Ganssen, G.M.; Davies, G.R.

    2001-01-01

    We present Holocene stable oxygen isotope data from the deep Arabian Sea off Somalia at a decadal time resolution as a proxy for the history of intermediate/upper deep water. These data show an overall δ18O reduction by 0.5‰ between 10 and ~6.5 kyr B.P. superimposed upon short-term δ18O variations

  20. Groundwater reorganization in the Floridan aquifer following Holocene sea-level rise

    Science.gov (United States)

    Morrissey, Sheila K.; Clark, Jordan F.; Bennett, Michael; Richardson, Emily; Stute, Martin

    2010-10-01

    Sea-level fluctuations, particularly those associated with glacial-interglacial cycles, can have profound impacts on the flow and circulation of coastal groundwater: the water found at present in many coastal aquifers may have been recharged during the last glacial period, when sea level was over 100m lower than present, and thus is not in equilibrium with present recharge conditions. Here we show that the geochemistry of the groundwater found in the Floridan Aquifer System in south Florida is best explained by a reorganization of groundwater flow following the sea-level rise at the end of the Last Glacial Maximum approximately 18,000 years ago. We find that the geochemistry of the fresh water found in the upper aquifers at present is consistent with recharge from meteoric water during the last glacial period. The lower aquifer, however, consists of post-sea-level-rise salt water that is most similar to that of the Straits of Florida, though with some dilution from the residual fresh water from the last glacial period circulation. We therefore suggest that during the last glacial period, the entire Floridan Aquifer System was recharged with meteoric waters. After sea level rose, the increased hydraulic head reduced the velocity of the groundwater flow. This velocity reduction trapped the fresh water in the upper aquifers and initiated saltwater circulation in the lower aquifer.

  1. PLEISTOCENE-HOLOCENE PALAEOENVIRONMENTAL RECORDS FROM PERMAFROST SEQUENCES AT THE KARA SEA COAST (NW SIBERIA, RUSSIA

    Directory of Open Access Journals (Sweden)

    Irina Streletskaya

    2013-01-01

    Full Text Available The Kara Sea coasts were studied using comprehensive stratigraphic and geocryological methods. The paper presents the new analytical studies of ground ice and Quaternary deposits of Western Taymyr and presents the results of spore and pollen, foraminifera, grain-size, mineralogical, geochemical, oxygen isotopic, and other analyses. Several stratigraphic-geocryological transects from Yenisey and Gydan Bays enable us to refine the stratigraphy and palaeogeographical reconstruction of the environments and freezing of Late Pleistocene-Holocene sediments. Marine sedimentation conditions during the late Kargino time (MIS3 changed to continental conditions in MIS2 and MIS1. Marine sediments were frozen syn- and epigenetically with cryotexture and ground ice formation. Ice wedges formation corresponds to the end of the Pleistocene (MIS2 and during cooler periods of the Holocene.

  2. High- and low-latitude forcing of the Nile River regime during the Holocene inferred from laminated sediments of the Nile deep-sea fan

    NARCIS (Netherlands)

    Blanchet, C.; Tjallingii, R.; Frank, M.; Lorenzen, J.; Reitz, A.; Brown, K.; Feseker, T.; Brückmann, W.

    2013-01-01

    Sediments deposited on deep-sea fans are an excellent geological archive to reconstruct past changes in fluvial discharge. Here we present a reconstruction of changes in the regime of the Nile River during the Holocene obtained using bulk elemental composition, grain-size analyses and radiogenic

  3. Accurately measuring sea level change from space: an ESA Climate Change Initiative for MSL closure budget studies

    DEFF Research Database (Denmark)

    Legeais, Jean-Francois; Cazenave, Anny; Larnicol, Gille

    Sea level is a very sensitive index of climate change and variability. Sea level integrates the ocean warming, mountain glaciers and ice sheet melting. Understanding the sea level variability and changes implies an accurate monitoring of the sea level variable at climate scales, in addition...... to understanding the ocean variability and the exchanges between ocean, land, cryosphere, and atmosphere. That is why Sea Level is one of the Essential Climate Variables (ECV) selected in the frame of the ESA Climate Change Initiative (CCI) program. It aims at providing long-term monitoring of the sea level ECV...... validation, performed by several groups of the ocean and climate modeling community. At last, the main improvements derived from the algorithms development dedicated to the 2016 full reprocessing of the dataset are described. Efforts have also focused on the improvement of the sea level estimation...

  4. Sea-level and solid-Earth deformation feedbacks in ice sheet modelling

    Science.gov (United States)

    Konrad, Hannes; Sasgen, Ingo; Klemann, Volker; Thoma, Malte; Grosfeld, Klaus; Martinec, Zdeněk

    2014-05-01

    The interactions of ice sheets with the sea level and the solid Earth are important factors for the stability of the ice shelves and the tributary inland ice (e.g. Thomas and Bentley, 1978; Gomez et al, 2012). First, changes in ice extent and ice thickness induce viscoelastic deformation of the Earth surface and Earth's gravity field. In turn, global and local changes in sea level and bathymetry affect the grounding line and, subsequently, alter the ice dynamic behaviour. Here, we investigate these feedbacks for a synthetic ice sheet configuration as well as for the Antarctic ice sheet using a three-dimensional thermomechanical ice sheet and shelf model, coupled to a viscoelastic solid-Earth and gravitationally self-consistent sea-level model. The respective ice sheet undergoes a forcing from rising sea level, warming ocean, and/or changing surface mass balance. The coupling is realized by exchanging ice thickness, Earth surface deformation and sea level periodically. We apply several sets of viscoelastic Earth parameters to our coupled model, e.g. simulating a low-viscous upper mantle present at the Antarctic Peninsula (Ivins et al., 2011). Special focus of our study lies on the evolution of Earth surface deformation and local sea level changes, as well as on the accompanying grounding line evolution. N. Gomez, D. Pollard, J. X. Mitrovica, P. Huybers, and P. U. Clark 2012. Evolution of a coupled marine ice sheet-sea level model, J. Geophys. Res., 117, F01013, doi:10.1029/2011JF002128. E. R. Ivins, M. M. Watkins, D.-N. Yuan, R. Dietrich, G. Casassa, and A. Rülke 2011. On-land ice loss and glacial isostatic adjustment at the Drake Passage: 2003-2009, J. Geophys. Res. 116, B02403, doi: 10.1029/2010JB007607 R. H. Thomas and C. R. Bentley 1978. A model for Holocene retreat of the West Antarctic Ice Sheet, Quaternary Research, 10 (2), pages 150-170, doi: 10.1016/0033-5894(78)90098-4.

  5. An approach to palaeoseismicity in the Olkiluoto (sea) area during the early holocene

    International Nuclear Information System (INIS)

    Hutri, K.L.

    2007-06-01

    Olkiluoto Island is situated in the northern Baltic Sea, near the southwestern coast of Finland, and is the proposed location of a spent nuclear fuel repository. This study examined Holocene palaeoseismicity in the Olkiluoto area and in the surrounding sea areas by computer simulations together with acoustic-seismic, sedimentological and dating methods. The most abundant rock type on the island is migmatic mica gneiss, intruded by tonalites, granodiorites and granites. The surrounding Baltic Sea seabed consists of Palaeoproterozoic crystalline bedrock, which is to a great extent covered by younger Mesoproterozoic sedimentary rocks. The area contains several ancient deep-seated fracture zones that divide it into bedrock blocks. The response of bedrock at the Olkiluoto site was modelled considering four future ice-age scenarios. Each scenario produced shear displacements of fractures with different times of occurrence and varying recovery rates. Generally, the larger the maximum ice load, the larger were the permanent shear displacements. For a basic case, the maximum shear displacements were a few centimetres at the proposed nuclear waste repository level, at proximately 500 m b.s.l. high-resolution, low-frequency echo-sounding was used to examine the Holocene submarine sedimentary structures and possible direct and indirect indicators of palaeoseismic activity in the northern Baltic Sea. Echo-sounding profiles of Holocene submarine sediments revealed slides and slumps, normal faults, debris flows and turbidite-type structures. The profiles also showed pockmarks and other structures related to gas or groundwater seepages, which might be related to fracture zone activation. Evidence of postglacial reactivation in the study area was derived from the spatial occurrence of some of the structures, especial the faults and the seepages, in the vicinity of some old bedrock fracture zones. Palaeoseismic event(s) (a single or several events) in the Olkiluoto area were dated

  6. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland

    Science.gov (United States)

    Geirsdóttir, Áslaug; Miller, Gifford H.; Axford, Yarrow; Ólafsdóttir, Sædís

    2009-10-01

    Multiproxy climate records from Iceland document complex changes in terrestrial climate and glacier fluctuations through the Holocene, revealing some coherent patterns of change as well as significant spatial variability. Most studies on the Last Glacial Maximum and subsequent deglaciation reveal a dynamic Iceland Ice Sheet (IIS) that responded abruptly to changes in ocean currents and sea level. The IIS broke up catastrophically around 15 ka as the Polar Front migrated northward and sea level rose. Indications of regional advance or halt of the glaciers are seen in late Alleröd/early Younger Dryas time and again in PreBoreal time. Due to the apparent rise of relative sea level in Iceland during this time, most sites contain evidence for fluctuating, tidewater glacier termini occupying paleo fjords and bays. The time between the end of the Younger Dryas and the Preboreal was characterized by repeated jökulhlaups that eroded glacial deposits. By 10.3 ka, the main ice sheet was in rapid retreat across the highlands of Iceland. The Holocene thermal maximum (HTM) was reached after 8 ka with land temperatures estimated to be 3 °C higher than the 1961-1990 reference, and net precipitation similar to modern. Such temperatures imply largely ice-free conditions across Iceland in the early to mid-Holocene. Several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8.5 and 8 ka, but no moraines have been detected from that time. Termination of the HTM and onset of Neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4.5 and 4.0 ka, intensifying between 3.0 and 2.5 ka. Although a distinct warming during the Medieval Warm Period is not dramatically apparent in Icelandic records, the interval from ca AD 0 to 1200 is commonly characterized by relative stability with slow rates of change. The literature most commonly describes Little Ice Age moraines (ca AD 1250-1900) as representing the

  7. Early Holocene hydroclimate of Baffin Bay: Understanding the interplay between abrupt climate change events and ice sheet fluctuations

    Science.gov (United States)

    Corcoran, M. C.; Thomas, E. K.; Castañeda, I. S.; Briner, J. P.

    2017-12-01

    Understanding the causes of ice sheet fluctuations resulting in sea level rise is essential in today's warming climate. In high-latitude ice-sheet-proximal environments such as Baffin Bay, studying both the cause and the rate of ice sheet variability during past abrupt climate change events aids in predictions. Past climate reconstructions are used to understand ice sheet responses to changes in temperature and precipitation. The 9,300 and 8,200 yr BP events are examples of abrupt climate change events in the Baffin Bay region during which there were multiple re-advances of the Greenland and Laurentide ice sheets. High-resolution (decadal-scale) hydroclimate variability near the ice sheet margins during these abrupt climate change events is still unknown. We will generate a decadal-scale record of early Holocene temperature and precipitation using leaf wax hydrogen isotopes, δ2Hwax, from a lake sediment archive on Baffin Island, western Baffin Bay, to better understand abrupt climate change in this region. Shifts in temperature and moisture source result in changes in environmental water δ2H, which in turn is reflected in δ2Hwax, allowing for past hydroclimate to be determined from these compound-specific isotopes. The combination of terrestrial and aquatic δ2Hwax is used to determine soil evaporation and is ultimately used to reconstruct moisture variability. We will compare our results with a previous analysis of δ2Hwax and branched glycerol dialkyl glycerol tetraethers, a temperature and pH proxy, in lake sediment from western Greenland, eastern Baffin Bay, which indicates that cool and dry climate occurred in response to freshwater forcing events in the Labrador Sea. Reconstructing and comparing records on both the western and eastern sides of Baffin Bay during the early Holocene will allow for a spatial understanding of temperature and moisture balance changes during abrupt climate events, aiding in ice sheet modeling and predictions of future sea level

  8. Holocene Enviromental Changes in AN Amazonian Floodplain Lake

    Science.gov (United States)

    Moreira, L.; Moreira-Turcq, P. F.; Turcq, B.; Cordeiro, R. C.

    2011-12-01

    The floodplains lakes are built due to the fluctuations in the level of the rivers, which causes the formation of bars and accumulation of sediment carried by the rivers and its tributaries. Thus, significant quantities of organic matter can accumulate within these lakes that might represent important carbon sinks. The organic sedimentation process in the floodplains remains unknown as well as very little is known about past conditions in the Amazonian floodplains. Because these gaps, the aim of this work is to provide, through sedimentological, mineralogical and organic geochemical analysis of a 124-cm long core collected in Lago Comprido (eastern Amazonia), evidences of paleoenviromental changes during the Holocene. The core COM1 was analysed using radiocarbon dates, organic carbon concentration, C/N ratio, delta 13C and diatoms. The core points out different sedimentary environments that occurs in the last 9900 years cal BP. The record is divided into three phases: - phase III (124-94 cm, 9900 to 3200 cal years BP): this interval is characterized by delta 13C values typical of graminea, suggesting dry conditions with longer low water levels of the Amazon River. Supporting evidence for driest conditions during this period comes from low organic carbon values due to oxidation and absence of diatoms in the sediment. The carbon flux was very low, reaching an average of 0.9 g C/m2/year. - phase II (93-46 cm, 3200 to 940 years cal BP): increasing lake level beginning in this phase. The delta 13C values ranged between -25% and -29%, which are thought to represent terrestrial plants. This may indicate the presence of a flooded vegetation in this site. The freshwater planktonic diatoms Aulacoseira sp start to increase in this phase, additional evidence that the period of the annual high water stands was probably longer than before. Carbon flux increases, reaching an average of 5 g C/m2/year. - phase I (45-0cm, < 940 years cal BP): the delta 13C values and CN ratios did

  9. Southern Dobrogea coastal potable water sources and Upper Quaternary Black Sea level changes

    Science.gov (United States)

    Caraivan, Glicherie; Stefanescu, Diana

    2013-04-01

    Maximum (MIS 2), the shoreline retreats eastwards, reaching the 100-120 m isobaths. In these conditions, the surface drainage base level was very low. Phreatic nape closely followed the river valleys dynamics. Mean depth aquifer discharged on the inner shelf , where Sarmatian limestones outcrop. The deep aquifer discharge was restricted by the Capidava- Ovidiu Fault to the north-east and by a presumed seawards longitudinal Fault. This process enabled the migration of the prehistoric human communities, from Asia to Europe, who established settlements on the newly created alluvial plain on the western Black Sea shelf. The Holocene Transgression (MIS 1) determined a sea level rise up to the modern one, and probably higher. Under the pressure of these environmental changes, the Neolithic settlements slowly retreated upstream. During the Greek colonization, the rising sea level caused the salinisation of the previous drinking water phreatic sources. In these conditions, in the Roman Age, a new hydraulic infrastructure had to be developed, using aqueducts for available inland water delivery.

  10. Acropora palmata reef framework: A reliable indicator of sea level in the western atlantic for the past 10,000 years

    Science.gov (United States)

    Lighty, R. G.; MacIntyre, I. G.; Stuckenrath, R.

    1982-10-01

    A minimum sea-level curve for the past 10,000 years has been constructed on the basis of radiocarbon dates of Acropora palmata (Lamarck) samples from the shallow-water framework of both relict and modern reefs of the tropical western Atlantic. A. palmata framework is a reliable reference for reconstructing the history of late Quaternary sea levels owing to its restricted depth range (palmata framework, the ease of obtaining uncontaminated samples, and the minimal compaction of A. palmata reef facies. The minimum sea-level curve constructed in this study is useful not only in evaluating the reliability of present and future Holocene sea-level curves for the western Atlantic, but also in estimating paleo-water depths in the study of Holocene reef history of this area.

  11. On the regional characteristics of past and future sea-level change (Invited)

    Science.gov (United States)

    Timmermann, A.; McGregor, S.

    2010-12-01

    Global sea-level rise due to the thermal expansion of the warming oceans and freshwater input from melting glaciers and ice-sheets is threatening to inundate low-lying islands and coast-lines worldwide. At present global mean sea level rises at 3.1 ± 0.7 mm/yr with an accelerating tendency. However, the magnitude of recent decadal sea-level trends varies greatly spatially attaining values of up to 10 mm/yr in some areas of the western tropical Pacific. Identifying the causes of recent regional sea-level trends and understanding the patterns of future projected sea-level change is of crucial importance. Using a wind-forced simplified dynamical ocean model, we show that the regional features of recent decadal and multidecadal sea-level trends in the tropical Indo-Pacific can be attributed to changes in the prevailing wind-regimes. Furthermore it is demonstrated that within an ensemble of ten state-of-the art coupled general circulation models, forced by increasing atmospheric CO2 concentrations over the next century, wind-induced re-distributions of upper-ocean water play a key role in establishing the spatial characteristics of projected regional sea-level rise. Wind-related changes in near- surface mass and heat convergence near the Solomon Islands, Tuvalu, Kiribati, the Cook Islands and French Polynesia oppose, but can not cancel the regional signal of global mean sea-level rise.

  12. Extending the Instrumental Record of Sea-Level Change: A 1300-Year Sea-Level Record From Eastern Connecticut

    Science.gov (United States)

    Donnelly, J. P.; Cleary, P.

    2002-12-01

    The instrumental record of sea-level change in the northeastern United States extends back to the early 20th century and at New York City (NYC) extends back to 1856. These tide gauge records indicate that sea level has risen at a rate of 2.5 to 4 mm/year over the last 100-150 years. Geologic evidence of sea-level change in the region over the last 2,000 years indicates rates of sea-level rise of about 1 mm/year or less. The discordance between the instrumental and geologic records is frequently cited as potentially providing evidence that anthropogenic warming of the climate system has resulted in an increase in the rate of sea-level rise. In order to begin to test the hypothesis that acceleration in the rate of sea-level rise has occurred in the last 150 years due to anthropogenic climate warming, accurate and precise information on the timing of the apparent acceleration in sea-level rise are needed. Here we construct a high-resolution relative sea-level record for the past 1350 years by dating basal salt marsh peat samples above a glacial erratic in a western Connecticut salt marsh. Preservation of marsh vegetation remains in the sediment record that has a narrow vertical habitat range at the upper end of the tidal range provides information on past sea levels. { \\it Spartina patens} (marsh hay) and { \\it Juncus gerardi} (black rush) dominate both the modern marsh and their remains are the major constituent of the marsh sediments and occur in the modern marsh between mean high water (MHW) and mean highest high water. We use the elevation distribution of modern plant communities to estimate the relationship of sediment samples to paleo-mean high water. The chronology is based on 15 radiocarbon ages, supplemented by age estimates derived from the horizons of industrial Pb pollution and pollen indicative of European land clearance. Thirteen of the radiocarbon ages and the Pb and pollen data come from samples taken along a contact between marsh peat and a glacial

  13. The interaction of prehistoric human settlement, sea level change and tectonic uplift of the Coastal Range, eastern Taiwan

    Science.gov (United States)

    Yang, H.; Chen, W. S.

    2017-12-01

    The late Cenozoic mountain belt of Taiwan, resulting from the collision between the Eurasian and Philippine Sea plates, is known for its rapid tectonic uplift. As postglacial sea level rose ca. 15,000 yr ago, the eastern coast of Taiwan, due to the rapid tectonic uplift rate, displayed a totally different scenario comparing with most of the coastal plains around the world. At the beginning of postglacial era, the sea level rising rate was greater than the tectonic uplift rate which induced the original piedmont alluvial fan or coastal plain to be overwhelmed by sea water rapidly. Around 13.5 ka, the tectonic uplift rate caught up with the sea level rising and broad wave-cut platform formed. The approximation of tectonic uplift and sea level rising rates was lasting from 13.5 to 5ka, but shoreline progradation may have been enhanced by increased slope erosion which resulted in the alluvial fan forming at the later time of this period. As soon as the eustasy stabilized, the landmass continued to uplift which might have enhanced the river incising and wave erosion rapidly. Therefore the topographic expression along the eastern fringing of Coastal Range forms extended alluvial-fan, stream, and marine terraces and are covered by late Holocene colluvium and marine deposits. 88 archaeological sites were chosen in this study based on surface survey where the archaeological chronology of cultural stage is established primarily through examining pottery series and associated manual excavation. It is interesting that most of the archaeological sites were located on the alluvial fan although the Holocene marine terraces have formed after 5ka. There are no clear evidences to support a shore-oriented settlement, but the abundant alluvial depositional structures observed from the overlaying formation reveals the stream depositional system was still active at this time. If the Neolithic people wanted to come to the "new born" coastal region for the abundant ocean resources, they

  14. Holocene depositional history of a large glaciated estuary, Penobscot Bay, Maine

    Science.gov (United States)

    Knebel, H.J.

    1986-01-01

    Data from seismic-reflection profiles, sidescan sonar images, and sediment samples reveal the Holocene depositional history of the large (1100 km2) glaciated Penobscot Bay estuary of coastal Maine. Previous work has shown that the late Wisconsinan ice sheet retreated from the three main passages of the bay between 12,700 and 13,500 years ago and was accompanied by a marine transgression during which ice and sea were in contact. Isostatic recovery of the crust caused the bay to emerge during the immediate postglacial period, and relative sea level fell to at least -40 m sometime between 9000 and 11,500 years ago. During lowered sea level, the ancestral Penobscot River flowed across the subaerially exposed head of the bay and debouched into Middle Passage. Organic-matter-rich mud from the river was deposited rapidly in remnant, glacially scoured depressions in the lower reaches of Middle and West Passages behind a shallow (???20 m water depth) bedrock sill across the bay mouth. East Passage was isolated from the rest of the bay system and received only small amounts of locally derived fine-grained sediments. During the Holocene transgression that accompanied the eustatic rise of sea level, the locus of sedimentation shifted to the head of the bay. Here, heterogeneous fluvial deposits filled the ancestral valley of the Penobscot River as base level rose, and the migrating surf zone created a gently dipping erosional unconformity, marked by a thin (energy conditions and the waning influence of the Penobscot River at the head of the bay. In contrast, relatively thick (up to 25 m) silty clays accumulated within a subbottom trough in the western half of the bay head. This deposit apparently developed late in the transgression after sea level had reached -20 m and after the westward transport of fine-grained sediments from the Penobscot River had been established. During and since the late Holocene transgression of sea level, waves and currents have eroded, reworked, and

  15. Sea level change in Great Britain between 1859 and the present

    Science.gov (United States)

    Woodworth, Philip L.

    2018-04-01

    Short records of sea level measurements by the Ordnance Survey at 31 locations in 1859-1860, together with recent Mean Sea Level (MSL) information from the UK tide gauge network, have been used to estimate the average rates of sea level change around the coast of Great Britain since the mid-19th century. Rates are found to be approximately 1 mm yr-1 in excess of those expected for the present day based on geological information, providing evidence for a climate-change related component of the increase in UK sea level. In turn, the rates of change of MSL for the past 60 yr are estimated to be ˜1 mm yr-1 in excess of the long-term rates since 1859, suggesting an acceleration in the rate of sea level rise between the 19th and 20th/21st centuries. Although the historical records are very short (approximately a fortnight), this exercise in `data archaeology' shows how valuable to research even the shortest records can be, as long as the measurements were made by competent people and the datums of the measurements were fully documented.

  16. Remote coral reefs can sustain high growth potential and may match future sea-level trends.

    Science.gov (United States)

    Perry, Chris T; Murphy, Gary N; Graham, Nicholas A J; Wilson, Shaun K; Januchowski-Hartley, Fraser A; East, Holly K

    2015-12-16

    Climate-induced disturbances are contributing to rapid, global-scale changes in coral reef ecology. As a consequence, reef carbonate budgets are declining, threatening reef growth potential and thus capacity to track rising sea-levels. Whether disturbed reefs can recover their growth potential and how rapidly, are thus critical research questions. Here we address these questions by measuring the carbonate budgets of 28 reefs across the Chagos Archipelago (Indian Ocean) which, while geographically remote and largely isolated from compounding human impacts, experienced severe (>90%) coral mortality during the 1998 warming event. Coral communities on most reefs recovered rapidly and we show that carbonate budgets in 2015 average +3.7 G (G = kg CaCO3 m(-2) yr(-1)). Most significantly the production rates on Acropora-dominated reefs, the corals most severely impacted in 1998, averaged +8.4 G by 2015, comparable with estimates under pre-human (Holocene) disturbance conditions. These positive budgets are reflected in high reef growth rates (4.2 mm yr(-1)) on Acropora-dominated reefs, demonstrating that carbonate budgets on these remote reefs have recovered rapidly from major climate-driven disturbances. Critically, these reefs retain the capacity to grow at rates exceeding measured regional mid-late Holocene and 20th century sea-level rise, and close to IPCC sea-level rise projections through to 2100.

  17. Uplift rates from a new high-density GPS network in Palmer Land indicate significant late Holocene ice loss in the southwestern Weddell Sea

    Science.gov (United States)

    Wolstencroft, Martin; King, Matt A.; Whitehouse, Pippa L.; Bentley, Michael J.; Nield, Grace A.; King, Edward C.; McMillan, Malcolm; Shepherd, Andrew; Barletta, Valentina; Bordoni, Andrea; Riva, Riccardo E. M.; Didova, Olga; Gunter, Brian C.

    2015-10-01

    The measurement of ongoing ice-mass loss and associated melt water contribution to sea-level change from regions such as West Antarctica is dependent on a combination of remote sensing methods. A key method, the measurement of changes in Earth's gravity via the GRACE satellite mission, requires a potentially large correction to account for the isostatic response of the solid Earth to ice-load changes since the Last Glacial Maximum. In this study, we combine glacial isostatic adjustment modelling with a new GPS dataset of solid Earth deformation for the southern Antarctic Peninsula to test the current understanding of ice history in this region. A sufficiently complete history of past ice-load change is required for glacial isostatic adjustment models to accurately predict the spatial variation of ongoing solid Earth deformation, once the independently-constrained effects of present-day ice mass loss have been accounted for. Comparisons between the GPS data and glacial isostatic adjustment model predictions reveal a substantial misfit. The misfit is localized on the southwestern Weddell Sea, where current ice models under-predict uplift rates by approximately 2 mm yr-1. This under-prediction suggests that either the retreat of the ice sheet grounding line in this region occurred significantly later in the Holocene than currently assumed, or that the region previously hosted more ice than currently assumed. This finding demonstrates the need for further fieldwork to obtain direct constraints on the timing of Holocene grounding line retreat in the southwestern Weddell Sea and that GRACE estimates of ice sheet mass balance will be unreliable in this region until this is resolved.

  18. Marine water from mid-Holocene sea level highstand trapped in a coastal aquifer: Evidence from groundwater isotopes, and environmental significance

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Stephen [School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne (Australia); Currell, Matthew, E-mail: Matthew.currell@rmit.edu.au [School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne (Australia); Cendón, Dioni I. [Australian Nuclear Science and Technology Organisation, Kirrawee (Australia); Connected Water Initiative, School of Biological, Earth and Environmental Sciences, University of New South Wales (UNSW), Sydney (Australia)

    2016-02-15

    A multi-layered coastal aquifer in southeast Australia was assessed using environmental isotopes, to identify the origins of salinity and its links to palaeo-environmental setting. Spatial distribution of groundwater salinity (electrical conductivity values ranging from 0.395 to 56.1 mS/cm) was examined along the coastline along with geological, isotopic and chemical data. This allowed assessment of different salinity sources and emplacement mechanisms. Molar chloride/bromide ratios range from 619 to 1070 (621 to 705 in samples with EC > 15 mS/cm), indicating salts are predominantly marine. Two distinct vertical salinity profiles were observed, one with increasing salinity with depth and another with saline shallow water overlying fresh groundwater. The saline shallow groundwater (EC = 45.4 to 55.7 mS/cm) has somewhat marine-like stable isotope ratios (δ{sup 18}O = − 2.4 to − 1.9 ‰) and radiocarbon activities indicative of middle Holocene emplacement (47.4 to 60.4 pMC). This overlies fresher groundwater with late Pleistocene radiocarbon ages and meteoric stable isotopes (δ{sup 18}O = − 5.5 to − 4.6‰). The configuration suggests surface inundation of the upper sediments by marine water during the mid-Holocene (c. 2–8 kyr BP), when sea level was 1–2 m above today's level. Profiles of chloride, stable isotopes, and radiocarbon indicate mixing between this pre-modern marine water and fresh meteoric groundwater to varying degrees around the coastline. Mixing calculations using chloride and stable isotopes show that in addition to fresh-marine water mixing, some salinity is derived from transpiration by halophytic vegetation (e.g. mangroves). The δ{sup 13}C ratios in saline water (− 17.6 to − 18.4‰) also have vegetation/organic matter signatures, consistent with emplacement by surface inundation and extensive interaction between vegetation and recharging groundwater. Saline shallow groundwater is preserved only in areas where low

  19. Groundwater reorganization in the Floridan aquifer following Holocene sea-level rise

    OpenAIRE

    Morrissey, SK; Clark, JF; Bennett, M; Richardson, E; Stute, M

    2010-01-01

    Sea-level fluctuations, particularly those associated with glacial-interglacial cycles, can have profound impacts on the flow and circulation of coastal groundwater: the water found at present in many coastal aquifers may have been recharged during the last glacial period, when sea level was over 100 m lower than present, and thus is not in equilibrium with present recharge conditions. Here we show that the geochemistry of the groundwater found in the Floridan Aquifer System in south Florida ...

  20. Updating the results of glacier contribution to the sea level change

    Science.gov (United States)

    Dyurgerov, Mark B.; Abdalati, Waleed Dr. (Technical Monitor)

    2005-01-01

    I have completed an update of global glacier volume change. All data of glacier annual mass balances, surface area over the period 1945/46 till 2004, outside the Greenland and Antarctic ice sheets were included in this update. As the result global glacier volume change have been calculated, also in terms of glacier contribution to sea level change. These results were sent to Working Group 1 and 2 of IPCC-4 as the basis for modeling of sea level towards the end of 2100. In this study I have concentrated on studying glacier systems of different scales, from primary (e.g. Devon ice cap) to regional (e.g. Canadian Arctic), continental scale (e,g., entire Arctic), and global (e.g., change in glacier volume and contribution to sea level rise).

  1. Ancient DNA derived from alkenone-biosynthesizing haptophytes and other algae in Holocene sediments from the Black Sea

    NARCIS (Netherlands)

    Coolen, M.J.L.; Boere, A.; Abbas, M.; Wakeham, S.G.; Sinninghe Damsté, J.S.

    2006-01-01

    Holocene sea surface temperatures (SST) of the Black Sea have been reconstructed using sedimentary C37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte Emiliania huxleyi, whose fossil coccoliths are an important constituent of the unit I sediments. However,

  2. Holocene palaeoenvironmental history of the Amazonian mangrove belt

    Science.gov (United States)

    Cohen, Marcelo Cancela Lisboa; Pessenda, Luiz Carlos Ruiz; Behling, Hermann; de Fátima Rossetti, Dilce; França, Marlon Carlos; Guimarães, José Tasso Felix; Friaes, Yuri; Smith, Clarisse Beltrão

    2012-11-01

    Wetland dynamic in the northern Brazilian Amazon region during the Holocene was reviewed using palynological, carbon and nitrogen isotopes records, and C/N ratio previously published. The integration of 72 radiocarbon dates recorded in 34 sediment cores sampled along the marine and fluvial littoral, and mainly influenced by the Amazon River, reveals that marine influence and mangrove vegetation were wider than today on the mouth of Amazon River between >8990-8690 and 2300-2230 cal yr BP, forming a continuous mangrove belt along the northern Brazilian Amazon littoral. The establishment of this mangrove strip is a direct consequence of the marine incursion caused by post-glacial sea-level rise possibly associated with tectonic subsidence during the Early and Middle Holocene. In the Late Holocene, in areas influenced by the Amazon River discharge, the mangroves were replaced by freshwater vegetation, and the coast morphology evolved from an estuarine dominated into a rectilinear coast due to coastal progradation. Nevertheless, the marine-influenced littoral, which is currently dominated by mangroves and salt-marsh vegetation, has persistently had brackish water vegetation over tidal mud flats throughout the entire Holocene. Likely, the fragmentation of this continuous mangrove line during the Late Holocene was caused by the increase of river freshwater discharge associated to the change from dry into wet climates in the Late Holocene. This caused a significant decrease of tidal water salinity in areas near the mouth of Amazon River. These changes in the Amazon discharge are probably associated with dry and wet periods in the northern Amazon region during the Holocene.

  3. Changing Sea Levels

    Science.gov (United States)

    Pugh, David

    2004-04-01

    Flooding of coastal communities is one of the major causes of environmental disasters world-wide. This textbook explains how sea levels are affected by astronomical tides, weather effects, ocean circulation and climate trends. Based on courses taught by the author in the U.K. and the U.S., it is aimed at undergraduate students at all levels, with non-basic mathematics being confined to Appendices and a website http://publishing.cambridge.org/resources/0521532183/.

  4. Integrated analysis of beach ridge and lagoon systems as indicator of sea-level changes

    Science.gov (United States)

    Sander, Lasse; Hede, Mikkel U.; Fruergaard, Mikkel; Morigi, Caterina; Johannessen, Peter N.; Nielsen, Lars; Clemmensen, Lars B.; Nielsen, Lars H.; Pejrup, Morten

    2015-04-01

    Beach ridges and lagoons are common features of the modern coastal landscape in much of Denmark and represent an important part of the Holocene raised marine deposits. We here present our results from investigations into the possibilities of retrieving continuous relative sea-level (RSL) information from these sedimentary archives, as facilitated by the analysis of surface morphology, coring, subsurface imaging, absolute chronology, and modern analogues. The island of Samsø (55˚51'N, 10˚36'E) was chosen as a case study example. While each of the used archives merely covers a part of the mid to late Holocene developments, their joint analysis allows identifying and separating periods of rapid RSL rise, stability and fall over most of the island's marine stage. We present possible correlations of the data from the lagoons with data from a wide beach-ridge system and suggest causal relations of the RSL reconstruction with the spatial arrangements of marine and glacial landforms on Samsø. The integrated use of a geographical perspective combined with geological precision and methodology has proven to be of great value for understanding temporal, spatial, and process relations in the investigated coastal environment. The study stresses the value of analyzing genetically independent though complementary sedimentary archives to retrieve more complete and potentially more robust results. The presented approach may be useful in microtidal, sediment-surplus environments with a transgressive-regressive Holocene RSL history.

  5. Measuring the Rate of Change in Sea Level and Its Adherence to USACE Sea Level Rise Planning Scenarios Using Timeseries Metrics

    Science.gov (United States)

    White, K. D.; Huang, N.; Huber, M.; Veatch, W.; Moritz, H.; Obrien, P. S.; Friedman, D.

    2017-12-01

    In 2013, the United States Army Corps of Engineers (USACE) issued guidance for all Civil Works activities to incorporate the effects of sea level change as described in three distinct planning scenarios.[1] These planning scenarios provided a useful framework to incorporate these effects into Civil Works activities, but required the manual calculation of these scenarios for a given gage and set of datum. To address this need, USACE developed the Sea Level Change Curve Calculator (SLCCC) in 2014 which provided a "simple, web-based tool to provide repeatable analytical results."[2]USACE has been developing a successor to the SLCCC application which retains the same, intuitive functionality to calculate these planning scenarios, but it also allows the comparison of actual sea level change between 1992 and today against the projections, and builds on the user's ability to understand the rate of change using a variety of timeseries metrics (e.g. moving averages, trends) and related visualizations. These new metrics help both illustrate and measure the complexity and nuances of sea level change. [1] ER 1000-2-8162. http://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1100-2-8162.pdf. [2] SLCC Manual. http://www.corpsclimate.us/docs/SLC_Calculator_Manual_2014_88.pdf.

  6. A complete Holocene record of trematode-bivalve infection and implications for the response of parasitism to climate change.

    Science.gov (United States)

    Huntley, John Warren; Fürsich, Franz T; Alberti, Matthias; Hethke, Manja; Liu, Chunlian

    2014-12-23

    Increasing global temperature and sea-level rise have led to concern about expansions in the distribution and prevalence of complex-lifecycle parasites (CLPs). Indeed, numerous environmental variables can influence the infectivity and reproductive output of many pathogens. Digenean trematodes are CLPs with intermediate invertebrate and definitive vertebrate hosts. Global warming and sea level rise may affect these hosts to varying degrees, and the effect of increasing temperature on parasite prevalence has proven to be nonlinear and difficult to predict. Projecting the response of parasites to anthropogenic climate change is vital for human health, and a longer term perspective (10(4) y) offered by the subfossil record is necessary to complement the experimental and historical approaches of shorter temporal duration (10(-1) to 10(3) y). We demonstrate, using a high-resolution 9,600-y record of trematode parasite traces in bivalve hosts from the Holocene Pearl River Delta, that prevalence was significantly higher during the earliest stages of sea level rise, significantly lower during the maximum transgression, and statistically indistinguishable in the other stages of sea-level rise and delta progradation. This stratigraphic paleobiological pattern represents the only long-term high-resolution record of pathogen response to global change, is consistent with fossil and recent data from other marine basins, and is instructive regarding the future of disease. We predict an increase in trematode prevalence concurrent with anthropogenic warming and marine transgression, with negative implications for estuarine macrobenthos, marine fisheries, and human health.

  7. Holocene Lake-Level Fluctuations of Lake Aricota, Southern Peru

    Science.gov (United States)

    Placzek, Christa; Quade, Jay; Betancourt, Julio L.

    2001-09-01

    Lacustrine deposits exposed around Lake Aricota, Peru (17° 22‧S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (<350 yr). Diatomites associated with highstands several meters above the modern lake level indicate wet episodes. Maximum Holocene lake level was attained before 6100 14C yr B.P. and ended ∼2700 14C yr B.P. Moderately high lake levels occurred at 1700 and 1300 14C yr B.P. The highstand at Lake Aricota during the middle Holocene is coeval with a major lowstand at Lake Titicaca (16°S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes.

  8. Response of northern hemisphere environmental and atmospheric conditions to climate changes using Greenland aerosol records from the Eemian to the Holocene

    Science.gov (United States)

    Fischer, H.

    2017-12-01

    The Northern Hemisphere experienced dramatic climate changes over the last glacial cycle, including vast ice sheet expansion and frequent abrupt climate events. Moreover, high northern latitudes during the last interglacial (Eemian) were warmer than today and may provide guidance for future climate change scenarios. However, little evidence exists regarding the environmental alterations connected to these climate changes. Using aerosol concentration records in decadal resolution from the North Greenland Eemian Ice Drilling (NEEM) over the last 128,000 years we extract quantitative information on environmental changes, including the first comparison of northern hemisphere environmental conditions between the warmer than present Eemian and the early Holocene. Separating source changes from transport effects, we find that changes in the ice concentration greatly overestimate the changes in atmospheric concentrations in the aerosol source region, the latter mirroring changes in aerosol emissions. Glacial times were characterized by a strong reduction in terrestrial biogenic emissions (only 10-20% of the early Holocene value) reflecting the net loss of vegetated area in mid to high latitudes, while rapid climate changes during the glacial had essentially no effect on terrestrial biogenic aerosol emissions. An increase in terrestrial dust emissions of approximately a factor of eight during peak glacial and cold stadial intervals indicates higher aridity and dust storm activity in Asian deserts. Glacial sea salt aerosol emissions increased only moderately (by approximately 50%), likely due to sea ice expansion, while marked stadial/interstadial variations in sea salt concentrations in the ice reflect mainly changes in wet deposition en route. Eemian ice contains lower aerosol concentrations than ice from the early Holocene, due to shortened atmospheric residence time during the warmer Eemian, suggesting that generally 2°C warmer climate in high northern latitudes did not

  9. A High-Resolution Reconstruction of Late-Holocene Relative Sea Level in Rhode Island, USA

    Science.gov (United States)

    Stearns, R. B.; Engelhart, S. E.; Kemp, A.; Cahill, N.; Halavik, B. T.; Corbett, D. R.; Brain, M.; Hill, T. D.

    2017-12-01

    Studies on the US Atlantic and Gulf coasts have utilized salt-marsh peats and the macro- and microfossils preserved within them to reconstruct high-resolution records of relative sea level (RSL). We followed this approach to investigate spatial and temporal RSL variability in southern New England, USA, by reconstructing 3,300 years of RSL change in lower Narragansett Bay, Rhode Island. After reconnaisance of lower Narragansett Bay salt marshes, we recovered a 3.4m core at Fox Hill Marsh on Conanicut Island. We enumerated foraminiferal assemblages at 3cm intervals throughout the length of the core and we assessed trends in δ13C at 5 cm resolution. We developed a composite chronology (average resolution of ±50 years for a 1 cm slice) using 30 AMS radiocarbon dates and historical chronological markers of known age (137Cs, heavy metals, Pb isotopes, pollen). We assessed core compaction (mechanical compression) by collecting compaction-free basal-peat samples and using a published decompaction model. We employed fossil foraminifera and bulk sediment δ13C to estimate paleomarsh elevation using a Bayesian transfer function trained by a previously-published regional modern foraminiferal dataset. We combined the proxy RSL reconstruction and local tide-gauge measurements from Newport, Rhode Island (1931 CE to present) and estimated past rates of RSL change using an Errors-in-Variables Integrated Gaussian Process (EIV-IGP) model. Both basal peats and the decompaction model suggest that our RSL record is not significantly compacted. RSL rose from -3.9 m at 1250 BCE reaching -0.4 m at 1850 CE (1 mm/yr). We removed a Glacial Isostatic Adjustment (GIA) contribution of 0.9 mm/yr based on a local GPS site to facilitate comparison to regional records. The detrended sea-level reconstruction shows multiple departures from stable sea level (0 mm/yr) over the last 3,300 years and agrees with prior reconstructions from the US Atlantic coast showing evidence for sea-level changes that

  10. The Holocene History of Placentia Bay, Newfoundland

    DEFF Research Database (Denmark)

    Sheldon, Christina; Seidenkrantz, Marit-Solveig; Reynisson, Njall

    2013-01-01

    Marine sediments analyzed from cores taken in Placentia Bay, Newfoundland, located in the Labrador Sea, captured oceanographic and climatic changes from the end of the Younger Dryas through the Holocene. Placentia Bay is an ideal site to capture changes in both the south-flowing Labrador Current ...

  11. Holocene sea level fluctuations on western Indian continental margin: An update

    Digital Repository Service at National Institute of Oceanography (India)

    Hashimi, N.H.; Nigam, R.; Nair, R.R.; Rajagopalan, G.

    A new Holocene curve is generated for the western Indian continental margin. While constructing this curve careful selection of the dates were made by giving due considerations to the genetic characteristics of the dated material. This new curve...

  12. Modelling the increased frequency of extreme sea levels in the Ganges-Brahmaputra-Meghna delta due to sea level rise and other effects of climate change.

    Science.gov (United States)

    Kay, S; Caesar, J; Wolf, J; Bricheno, L; Nicholls, R J; Saiful Islam, A K M; Haque, A; Pardaens, A; Lowe, J A

    2015-07-01

    Coastal flooding due to storm surge and high tides is a serious risk for inhabitants of the Ganges-Brahmaputra-Meghna (GBM) delta, as much of the land is close to sea level. Climate change could lead to large areas of land being subject to increased flooding, salinization and ultimate abandonment in West Bengal, India, and Bangladesh. IPCC 5th assessment modelling of sea level rise and estimates of subsidence rates from the EU IMPACT2C project suggest that sea level in the GBM delta region may rise by 0.63 to 0.88 m by 2090, with some studies suggesting this could be up to 0.5 m higher if potential substantial melting of the West Antarctic ice sheet is included. These sea level rise scenarios lead to increased frequency of high water coastal events. Any effect of climate change on the frequency and severity of storms can also have an effect on extreme sea levels. A shelf-sea model of the Bay of Bengal has been used to investigate how the combined effect of sea level rise and changes in other environmental conditions under climate change may alter the frequency of extreme sea level events for the period 1971 to 2099. The model was forced using atmospheric and oceanic boundary conditions derived from climate model projections and the future scenario increase in sea level was applied at its ocean boundary. The model results show an increased likelihood of extreme sea level events through the 21st century, with the frequency of events increasing greatly in the second half of the century: water levels that occurred at decadal time intervals under present-day model conditions occurred in most years by the middle of the 21st century and 3-15 times per year by 2100. The heights of the most extreme events tend to increase more in the first half of the century than the second. The modelled scenarios provide a case study of how sea level rise and other effects of climate change may combine to produce a greatly increased threat to life and property in the GBM delta by the end

  13. Caspian Sea level changes during the last millennium: historical and geological evidences from the south Caspian Sea

    Science.gov (United States)

    Naderi Beni, A.; Lahijani, H.; Mousavi Harami, R.; Arpe, K.; Leroy, S. A. G.; Marriner, N.; Berberian, M.; Andrieu-Ponel, V.; Djamali, M.; Mahboubi, A.

    2013-03-01

    Historical literature may constitute a valuable source of information to reconstruct sea level changes. Here, historical documents and geological records have been combined to reconstruct Caspian sea-level (CSL) changes during the last millennium. In addition to a literature survey, new data from two short sediment cores were obtained from the south-eastern Caspian coast to identify coastal change driven by water-level changes. Two articulated bivalve shells from the marine facies were radiocarbon dated and calibrated to establish a chronology and to compare them with historical findings. The overall results indicate a high-stand during the Little Ice Age, up to -19 m, with a -28 m low-stand during the Medieval Climate Anomaly, while presently the CSL stands at -26.5 m. A comparison of the CSL curve with other lake systems and proxy records suggests that the main sea-level oscillations are essentially paced by solar irradiance. Although the major controller of the long-term CSL changes is driven by climatological factors, the seismicity of the basin could create locally changes in base level. These local base-level changes should be considered in any CSL reconstruction.

  14. Caspian sea-level changes during the last millennium: historical and geological evidence from the south Caspian Sea

    Science.gov (United States)

    Naderi Beni, A.; Lahijani, H.; Mousavi Harami, R.; Arpe, K.; Leroy, S. A. G.; Marriner, N.; Berberian, M.; Andrieu-Ponel, V.; Djamali, M.; Mahboubi, A.; Reimer, P. J.

    2013-07-01

    Historical literature may constitute a valuable source of information to reconstruct sea-level changes. Here, historical documents and geological records have been combined to reconstruct Caspian sea-level (CSL) changes during the last millennium. In addition to a comprehensive literature review, new data from two short sediment cores were obtained from the south-eastern Caspian coast to identify coastal change driven by water-level changes and to compare the results with other geological and historical findings. The overall results indicate a high-stand during the Little Ice Age, up to -21 m (and extra rises due to manmade river avulsion), with a -28 m low-stand during the Medieval Climate Anomaly, while presently the CSL stands at -26.5 m. A comparison of the CSL curve with other lake systems and proxy records suggests that the main sea-level oscillations are essentially paced by solar irradiance. Although the major controller of the long-term CSL changes is driven by climatological factors, the seismicity of the basin creates local changes in base level. These local base-level changes should be considered in any CSL reconstruction.

  15. Reconstruction of Holocene environmental changes in Southern Kurils (North-Western Pacific) based on palaeolake sediment proxies from Shikotan Island

    Science.gov (United States)

    Nazarova, Larisa; Grebennikova, Tatiana A.; Razjigaeva, Nadezhda G.; Ganzey, Larisa A.; Belyanina, Nina I.; Arslanov, Khikmat A.; Kaistrenko, Victor M.; Gorbunov, Aleksey O.; Kharlamov, Andrey A.; Rudaya, Natalia; Palagushkina, Olga; Biskaborn, Boris K.; Diekmann, Bernhard

    2017-12-01

    We investigated a well-dated sediment section of a palaeolake situated in the coastal zone of Shikotan Island (Lesser Kurils) for organic sediment-geochemistry and biotic components (diatoms, chironomids, pollen) in order to provide a reconstruction of the palaeoenvironmental changes and palaeo-events (tsunamis, sea-level fluctuations and landslides) in Holocene. During the ca 8000 years of sedimentation the changes in organic sediment-geochemistry and in composition of the diatoms and chironomids as well as the shifts in composition of terrestrial vegetation suggest that the period until ca 5800 cal yr BP was characterized by a warm and humid climate (corresponds to middle Holocene optimum) with climate cooling thereafter. A warm period reconstructed from ca 900 to at least ca 580 cal yr BP corresponds to a transition to a Nara-Heian-Kamakura warm stage and can be correlated to a Medieval Warm Period. After 580 cal yr PB, the lake gradually dried out and climatic signals could not be obtained from the declining lacustrine biological communities, but the increasing role of spruce and disappearance of the oak from the vegetation give evidences of the climate cooling that can be correlated with the LIA. The marine regression stages at the investigated site are identified for ca 6200-5900 (at the end of the middle Holocene transgression), ca 5500-5100 (Middle Jomon regression or Kemigawa regression), and ca 1070-360 cal yr BP (at the end of Heian transgression). The lithological structure of sediments and the diatom compositions give evidences for the multiple tsunami events of different strengths in the Island. Most remarkable of them can be dated at around ca 7000, 6460, 5750, 4800, 950 cal yr BP. The new results help to understand the Holocene environmental history of the Southern Kurils as a part of the Kuril-Kamchatka and Aleutian Marginal Sea-Island Arc Systems in the North-Western Pacific region.

  16. Human responses to Middle Holocene climate change on California's Channel Islands

    Science.gov (United States)

    Kennett, Douglas J.; Kennett, James P.; Erlandson, Jon M.; Cannariato, Kevin G.

    2007-02-01

    High-resolution archaeological and paleoenvironmental records from California's Channel Islands provide a unique opportunity to examine potential relationships between climatically induced environmental changes and prehistoric human behavioral responses. Available climate records in western North America (7-3.8 ka) indicate a severe dry interval between 6.3 and 4.8 ka embedded within a generally warm and dry Middle Holocene. Very dry conditions in western North America between 6.3 and 4.8 ka correlate with cold to moderate sea-surface temperatures (SST) along the southern California Coast evident in Ocean Drilling Program (ODP) Core 893A/B (Santa Barbara Basin). An episode of inferred high marine productivity between 6.3 and 5.8 ka corresponds with the coldest estimated SSTs of the Middle Holocene, otherwise marked by warm/low productivity marine conditions (7.5-3.8 ka). The impact of this severe aridity on humans was different between the northern and southern Channel Islands, apparently related to degree of island isolation, size and productivity of islands relative to population, fresh water availability, and on-going social relationships between island and continental populations. Northern Channel Islanders seem to have been largely unaffected by this severe arid phase. In contrast, cultural changes on the southern Channel Islands were likely influenced by the climatically induced environmental changes. We suggest that productive marine conditions coupled with a dry terrestrial climate between 6.3 and 5.8 ka stimulated early village development and intensified fishing on the more remote southern islands. Contact with people on the adjacent southern California Coast increased during this time with increased participation in a down-the-line trade network extending into the western Great Basin and central Oregon. Genetic similarities between Middle Holocene burial populations on the southern Channel Islands and modern California Uto-Aztecan populations suggest

  17. NASA Sea Level Change Portal - It not just another portal site

    Science.gov (United States)

    Huang, T.; Quach, N.; Abercrombie, S. P.; Boening, C.; Brennan, H. P.; Gill, K. M.; Greguska, F. R., III; Jackson, R.; Larour, E. Y.; Shaftel, H.; Tenenbaum, L. F.; Zlotnicki, V.; Moore, B.; Moore, J.; Boeck, A.

    2017-12-01

    The NASA Sea Level Change Portal (https://sealevel.nasa.gov) is designed as a "one-stop" source for current sea level change information, including interactive tools for accessing and viewing regional data, a virtual dashboard of sea level indicators, and ongoing updates through a suite of editorial products that include content articles, graphics, videos, and animations. With increasing global temperatures warming the ocean and melting ice sheets and glaciers, there is an immediate need both for accelerating sea level change research and for making this research accessible to scientists in disparate discipline, to the general public, to policy makers and business. The immersive and innovative NASA portal debuted at the 2015 AGU attracts thousands of daily visitors and over 30K followers on Facebook®. Behind its intuitive interface is an extensible architecture that integrates site contents, data for various sources, visualization, horizontal-scale geospatial data analytic technology (called NEXUS), and an interactive 3D simulation platform (called the Virtual Earth System Laboratory). We will present an overview of our NASA portal and some of our architectural decisions along with discussion on our open-source, cloud-based data analytic technology that enables on-the-fly analysis of heterogeneous data.

  18. Climate-change-driven accelerated sea-level rise detected in the altimeter era.

    Science.gov (United States)

    Nerem, R S; Beckley, B D; Fasullo, J T; Hamlington, B D; Masters, D; Mitchum, G T

    2018-02-27

    Using a 25-y time series of precision satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3, we estimate the climate-change-driven acceleration of global mean sea level over the last 25 y to be 0.084 ± 0.025 mm/y 2 Coupled with the average climate-change-driven rate of sea level rise over these same 25 y of 2.9 mm/y, simple extrapolation of the quadratic implies global mean sea level could rise 65 ± 12 cm by 2100 compared with 2005, roughly in agreement with the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) model projections. Copyright © 2018 the Author(s). Published by PNAS.

  19. Holocene millennial to centennial scale carbonate cycles (leeward margin, Great Bahama Bank)

    Science.gov (United States)

    Roth, S.; Reijmer, J. J. G.

    2003-04-01

    The main research topic of this project is the evaluation of Holocene to Recent climatic variability and the impact on shallow-water sediment production of carbonate platforms. A 38m long sediment core (MD992201) was analyzed, obtained from 290m water depth on the leeward margin of Great Bahama Bank. Fourteen Accelerator Mass Spectrometry (AMS) dates determined a core bottom age of 7,230 years BP and permitted the construction of a precise time frame. With a sampling interval of 5cm, a decadal time resolution could be achieved. Sedimentation rates varied between 3 to 14m/kyr. Carbonate content ranges from 96 to almost 100wt%, most of which is aragonite (83-92wt%). High Magnesium Calcite (HMC) makes up the second major fraction with 2-9wt%, while Low Magnesium Calcite occurs with minor percentages (0.5-4wt%). Singular Spectrum Analysis (SSA) of the aragonitic carbonate phase showed two different trends and two primary oscillatory signals. Aragonite production on Great Bahama Bank started at 7,230yr BP when the Holocene sea-level rise flooded the shallow platform top. The first eigenvector captures this long-term trend extending over the entire Mid to Late Holocene succession displaying the Holocene sea-level fluctuations. The second trend indicates millennial scale variations, which can be attributed to a combination of geomagnetic shielding and solar parameters. The two quasi-periodic signals show wavelengths of 400-600 years and approx. 210 years. These oscillations are interpreted in terms of instabilities of the thermohaline circulation and solar parameters, respectively. The oscillatory aragonite signals and oxygen isotope derived temperatures (planktonic foraminifers) agree with northern hemisphere temperature changes (e.g. Medieval Warm Period and Little Ice Age) and the delta-14C record of tree rings (e.g. Oort to Dalton solar minima). This study shows that carbonate platform systems not only respond to sea-level variations but also are precise recorders of

  20. Recent Changes in Land Water Storage and Its Contribution to Sea Level Variations

    Science.gov (United States)

    Wada, Yoshihide; Reager, John T.; Chao, Benjamin F.; Wang, Jida; Lo, Min-Hui; Song, Chunqiao; Li, Yuwen; Gardner, Alex S.

    2016-01-01

    Sea level rise is generally attributed to increased ocean heat content and increased rates glacier and ice melt. However, human transformations of Earth's surface have impacted water exchange between land, atmosphere, and ocean, ultimately affecting global sea level variations. Impoundment of water in reservoirs and artificial lakes has reduced the outflow of water to the sea, while river runoff has increased due to groundwater mining, wetland and endorheic lake storage losses, and deforestation. In addition, climate-driven changes in land water stores can have a large impact on global sea level variations over decadal timescales. Here, we review each component of negative and positive land water contribution separately in order to highlight and understand recent changes in land water contribution to sea level variations.

  1. Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation

    Science.gov (United States)

    Baker, P. A.; Fritz, S. C.; Garland, J.; Ekdahl, E.

    2005-10-01

    A growing number of sites in the Northern Hemisphere show centennial- to millennial-scale climate variation that has been correlated with change in solar variability or with change in North Atlantic circulation. However, it is unclear how (or whether) these oscillations in the climate system are manifest in the Southern Hemisphere because of a lack of sites with suitably high sampling resolution. In this paper, we reconstruct the lake-level history of Lake Titicaca, using the carbon isotopic content of sedimentary organic matter, to evaluate centennial- to millennial-scale precipitation variation and its phasing relative to sites in the Northern Hemisphere. The pattern and timing of lake-level change in Lake Titicaca is similar to the ice-rafted debris record of Holocene Bond events, demonstrating a possible coupling between precipitation variation on the Altiplano and North Atlantic sea-surface temperatures (SSTs). The cold periods of the Holocene Bond events correspond with periods of increased precipitation on the Altiplano. Holocene precipitation variability on the Altiplano is anti-phased with respect to precipitation in the Northern Hemisphere monsoon region. More generally, the tropical Andes underwent large changes in precipitation on centennial-to-millennial timescales during the Holocene.

  2. Sea level hazards: Altimetric monitoring of tsunamis and sea level rise

    Science.gov (United States)

    Hamlington, Benjamin Dillon

    Whether on the short timescale of an impending tsunami or the much longer timescale of climate change-driven sea level rise, the threat stemming from rising and inundating ocean waters is a great concern to coastal populations. Timely and accurate observations of potentially dangerous changes in sea level are vital in determining the precautionary steps that need to be taken in order to protect coastal communities. While instruments from the past have provided in situ measurements of sea level at specific locations across the globe, satellites can be used to provide improved spatial and temporal sampling of the ocean in addition to producing more accurate measurements. Since 1993, satellite altimetry has provided accurate measurements of sea surface height (SSH) with near-global coverage. Not only have these measurements led to the first definitive estimates of global mean sea level rise, satellite altimetry observations have also been used to detect tsunami waves in the open ocean where wave amplitudes are relatively small, a vital step in providing early warning to those potentially affected by the impending tsunami. The use of satellite altimetry to monitor two specific sea level hazards is examined in this thesis. The first section will focus on the detection of tsunamis in the open ocean for the purpose of providing early warning to coastal inhabitants. The second section will focus on estimating secular trends using satellite altimetry data with the hope of improving our understanding of future sea level change. Results presented here will show the utility of satellite altimetry for sea level monitoring and will lay the foundation for further advancement in the detection of the two sea level hazards considered.

  3. Relative sea level in the Western Mediterranean basin: A regional test of the ICE-7G_NA (VM7) model and a constraint on late Holocene Antarctic deglaciation

    Science.gov (United States)

    Roy, Keven; Peltier, W. R.

    2018-03-01

    The Mediterranean Basin is a region of special interest in the study of past and present relative sea level evolution, given its location south of the ice sheets that covered large fractions of Northern Europe during the last glaciation, the large number of biological, geological and archaeological sea level indicators that have been retrieved from its coastal regions, as well as its high density of modern coastal infrastructure. Models of the Glacial Isostatic Adjustment (GIA) process provide reconstructions of past relative sea level evolution, and can be tested for validity against past sea level indicators from the region. It is demonstrated herein that the latest ICE-7G_NA (VM7) model of the GIA process, the North American component of which was refined using a full suite of geophysical observables, is able to reconcile the vast majority of uniformly analyzed relative sea level constraints available for the Western part of the Mediterranean basin, a region to which it was not tuned. We also revisit herein the previously published interpretations of relative sea level information obtained from Roman-era coastal Mediterranean "fish tanks", analyze the far-field influence of the rate of late Holocene Antarctic ice sheet melting history on the exceptionally detailed relative sea level history available from southern Tunisia, and extend the analysis to complementary constraints on the history of Antarctic ice-sheet melting available from islands in the equatorial Pacific Ocean. The analyses reported herein provide strong support for the global "exportability" of the ICE-7G_NA (VM7) model, a result that speaks directly to the ability of spherically symmetric models of the internal viscoelastic structure to explain globally distributed observations, while also identifying isolated regions of remaining misfit which will benefit from further study.

  4. Uncertainties in Steric Sea Level Change Estimation During the Satellite Altimeter Era: Concepts and Practices

    Science.gov (United States)

    MacIntosh, C. R.; Merchant, C. J.; von Schuckmann, K.

    2017-01-01

    This article presents a review of current practice in estimating steric sea level change, focussed on the treatment of uncertainty. Steric sea level change is the contribution to the change in sea level arising from the dependence of density on temperature and salinity. It is a significant component of sea level rise and a reflection of changing ocean heat content. However, tracking these steric changes still remains a significant challenge for the scientific community. We review the importance of understanding the uncertainty in estimates of steric sea level change. Relevant concepts of uncertainty are discussed and illustrated with the example of observational uncertainty propagation from a single profile of temperature and salinity measurements to steric height. We summarise and discuss the recent literature on methodologies and techniques used to estimate steric sea level in the context of the treatment of uncertainty. Our conclusions are that progress in quantifying steric sea level uncertainty will benefit from: greater clarity and transparency in published discussions of uncertainty, including exploitation of international standards for quantifying and expressing uncertainty in measurement; and the development of community "recipes" for quantifying the error covariances in observations and from sparse sampling and for estimating and propagating uncertainty across spatio-temporal scales.

  5. Sensitivity analysis of hydrogeological parameters affecting groundwater storage change caused by sea level rise

    Science.gov (United States)

    Shin, J.; Kim, K.-H.; Lee, K.-K.

    2012-04-01

    Sea level rise, which is one of the representative phenomena of climate changes caused by global warming, can affect groundwater system. The rising trend of the sea level caused by the global warming is reported to be about 3 mm/year for the most recent 10 year average (IPCC, 2007). The rate of sea level rise around the Korean peninsula is reported to be 2.30±2.22 mm/yr during the 1960-1999 period (Cho, 2002) and 2.16±1.77 mm/yr (Kim et al., 2009) during the 1968-2007 period. Both of these rates are faster than the 1.8±0.5 mm/yr global average for the similar 1961-2003 period (IPCC, 2007). In this study, we analyzed changes in the groundwater environment affected by the sea level rise by using an analytical methodology. We tried to find the most effective parameters of groundwater amount change in order to estimate the change in fresh water amount in coastal groundwater. A hypothetical island model of a cylindrical shape in considered. The groundwater storage change is bi-directional as the sea level rises according to the natural and hydrogeological conditions. Analysis of the computation results shows that topographic slope and hydraulic conductivity are the most sensitive factors. The contributions of the groundwater recharge rate and the thickness of aquifer below sea level are relatively less effective. In the island with steep seashore slopes larger than 1~2 degrees or so, the storage amount of fresh water in a coastal area increases as sea level rises. On the other hand, when sea level drops, the storage amount decreases. This is because the groundwater level also rises with the rising sea level in steep seashores. For relatively flat seashores, where the slope is smaller than around 1-2 degrees, the storage amount of coastal fresh water decreases when the sea level rises because the area flooded by the rising sea water is increased. The volume of aquifer fresh water in this circumstance is greatly reduced in proportion to the flooded area with the sea

  6. Sea Level Change and Coastal Climate Services: The Way Forward

    Directory of Open Access Journals (Sweden)

    Gonéri Le Cozannet

    2017-10-01

    Full Text Available For many climate change impacts such as drought and heat waves, global and national frameworks for climate services are providing ever more critical support to adaptation activities. Coastal zones are especially in need of climate services for adaptation, as they are increasingly threatened by sea level rise and its impacts, such as submergence, flooding, shoreline erosion, salinization and wetland change. In this paper, we examine how annual to multi-decadal sea level projections can be used within coastal climate services (CCS. To this end, we review the current state-of-the art of coastal climate services in the US, Australia and France, and identify lessons learned. More broadly, we also review current barriers in the development of CCS, and identify research and development efforts for overcoming barriers and facilitating their continued growth. The latter includes: (1 research in the field of sea level, coastal and adaptation science and (2 cross-cutting research in the area of user interactions, decision making, propagation of uncertainties and overall service architecture design. We suggest that standard approaches are required to translate relative sea level information into the forms required to inform the wide range of relevant decisions across coastal management, including coastal adaptation.

  7. Changes in Absolute Sea Level Along U.S. Coasts

    Data.gov (United States)

    U.S. Environmental Protection Agency — This map shows changes in absolute sea level from 1960 to 2016 based on satellite measurements. Data were adjusted by applying an inverted barometer (air pressure)...

  8. Hydrologic-energy balance constraints on the Holocene lake-level history of lake Titicaca, South America

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, H.D.; Dunbar, R.B. [Stanford University, Geological and Environmental Sciences, Stanford, CA (United States)

    2004-09-01

    A basin-scale hydrologic-energy balance model that integrates modern climatological, hydrological, and hypsographic observations was developed for the modern Lake Titicaca watershed (northern Altiplano, South America) and operated under variable conditions to understand controls on post-glacial changes in lake level. The model simulates changes in five environmental variables (air temperature, cloud fraction, precipitation, relative humidity, and land surface albedo). Relatively small changes in three meteorological variables (mean annual precipitation, temperature, and/or cloud fraction) explain the large mid-Holocene lake-level decrease ({proportional_to}85 m) inferred from seismic reflection profiling and supported by sediment-based paleoproxies from lake sediments. Climatic controls that shape the present-day Altiplano and the sediment-based record of Holocene lake-level change are combined to interpret model-derived lake-level simulations in terms of changes in the mean state of ENSO and its impact on moisture transport to the Altiplano. (orig.)

  9. Hydrologic-energy balance constraints on the Holocene lake-level history of lake Titicaca, South America

    Science.gov (United States)

    Rowe, H. D.; Dunbar, R. B.

    2004-09-01

    A basin-scale hydrologic-energy balance model that integrates modern climatological, hydrological, and hypsographic observations was developed for the modern Lake Titicaca watershed (northern Altiplano, South America) and operated under variable conditions to understand controls on post-glacial changes in lake level. The model simulates changes in five environmental variables (air temperature, cloud fraction, precipitation, relative humidity, and land surface albedo). Relatively small changes in three meteorological variables (mean annual precipitation, temperature, and/or cloud fraction) explain the large mid-Holocene lake-level decrease (˜85 m) inferred from seismic reflection profiling and supported by sediment-based paleoproxies from lake sediments. Climatic controls that shape the present-day Altiplano and the sediment-based record of Holocene lake-level change are combined to interpret model-derived lake-level simulations in terms of changes in the mean state of ENSO and its impact on moisture transport to the Altiplano.

  10. ICE-6G models of postglacial relative sea-level history applied to Holocene coral reef and mangrove records of the western Caribbean

    Science.gov (United States)

    Toscano, M. A.; Peltier, W. R.; Drummond, R.; Gonzalez, J.

    2012-12-01

    Fossil coral reefs and mangrove peat accumulations at western Caribbean sites along a latitudinal gradient from the Florida Keys through Belize and Panama provide dated and interpreted 8,000 year Holocene sea-level records for comparison with RSL predictions of the ICE-6G (VM5A, VM5B; L90) models of glacio-hydro-isostatic adjustment, with and without rotational feedback. These presumably passive continental margin sites provide the means to establish a N-S spatial trend in the varying influences of GIA, eustatic components of Holocene sea level, extent of forebulge collapse and influence of rotational feedback over a 20° latitudinal range. Previous ICE6G (VM5A) model-coral data comparisons for St Croix, USVI, Antigua, Martinique and Barbados (Toscano, Peltier and Drummond, 2011, QSR) along the eastern Caribbean plate and island arc illustrated the close model-data compatibility, the influence of rotational feedback acting as a significant factor in reducing misfits, and the need for high quality in situ data to confirm the extension of the proglacial forebulge into tropical latitudes. The gradient of western Caribbean continental shelf sites comprises a much more varied range of model-data relationships based on extensive combined Acropora palmata (reef crest coral) and Rhizophora mangle (microtidal mangrove) peat datasets in all cases. Starting at the northernmost region with the Florida Keys, there exist negative model misfits to the data, suggesting the possibility of a positive tectonic overprint upon expectations related to the glacial isostatic adjustment process acting alone, even though this region is normally believed to be tectonically stable. The largest multi-proxy database from Belize supports the likelihood of increasing rates of subsidence from north to south in the Belize Lagoon, which may account for numerous positive GIA model-data misfits. The southernmost site at Panama is most similar to Belize in the possible nature of tectonic influences on

  11. Geologic records of Pleistocene, Holocene and Anthropocene beach profiles?

    Science.gov (United States)

    Dougherty, Amy; Choi, Jeong-Heon; Dosseto, Anthony

    2017-04-01

    The Anthropocene Working Group recently concluded that we have entered a new Epoch; starting during the last century when carbon dioxide, temperatures, and sea level all exceeding previous Holocene measurements. Climate change models predict a 1m rise in sea-level by 2100 coupled with increased storm intensity. Determining how vulnerable coasts will respond to global warming in the future, requires past records of sea-level and storm impacts to be deciphered. Paying specific attention to any changes prior to, and since, the onset of the Industrial Revolution. Coastal change over centennial time-scales has long fallen within a knowledge gap that exists between our understanding of shoreline behaviour measured over decades and that inferred from the landscape over millennia. Insight on shoreline behaviour across spatial and temporal scales is gained using computers to integrate models of short-term morphodynamics along beaches with longer-term coastal landscape evolution models. However, limitations exist as process-based engineering models depend on wave climate and beach profile data that is restricted to regional/historical records, while large-scale coastal behaviour models are based on general chronostratographic data from topographic profiles, interpolated cores, and isochrons extrapolated from deep radiocarbon ages. Here we demonstrate a unique methodology combining state-of-the-art geophysics, luminescence, and remote sensing techniques on prograded barriers to extract comprehensive chronostratigraphic records. Ground Penetrating Radar (GPR) data document beach and dune stratigraphy at decimetre resolution. Optically Stimulated Luminescence (OSL) directly date the formation of paleo-beachfaces and dunes. Light Detection and Ranging (LiDAR) image the lateral extent of strandplain ridge morphology. The resulting record of paleo-beach profiles spanning from the present-day beach through Holocene and Pleistocene barriers, enables our in-depth understanding of

  12. Accurately measuring sea level change from space: an ESA climate change initiative for MSL closure budget studies

    Science.gov (United States)

    Legeais, JeanFrancois; Benveniste, Jérôme

    2016-07-01

    Sea level is a very sensitive index of climate change and variability. Sea level integrates the ocean warming, mountain glaciers and ice sheet melting. Understanding the sea level variability and changes implies an accurate monitoring of the sea level variable at climate scales, in addition to understanding the ocean variability and the exchanges between ocean, land, cryosphere, and atmosphere. That is why Sea Level is one of the Essential Climate Variables (ECV) selected in the frame of the ESA Climate Change Initiative (CCI) program. It aims at providing long-term monitoring of the sea level ECV with regular updates, as required for climate studies. The program is now in its second phase of 3 year (following phase I during 2011-2013). The objectives are firstly to involve the climate research community, to refine their needs and collect their feedbacks on product quality. And secondly to develop, test and select the best algorithms and standards to generate an updated climate time series and to produce and validate the Sea Level ECV product. This will better answer the climate user needs by improving the quality of the Sea Level products and maintain a sustain service for an up-to-date production. This has led to the production of a first version of the Sea Level ECV which has benefited from yearly extensions and now covers the period 1993-2014. Within phase II, new altimeter standards have been developed and tested in order to reprocess the dataset with the best standards for climate studies. The reprocessed ECV will be released in summer 2016. We will present the main achievements of the ESA CCI Sea Level Project. On the one hand, the major steps required to produce the 22 years climate time series are briefly described: collect and refine the user requirements, development of adapted algorithms for climate applications and specification of the production system. On the other hand, the product characteristics are described as well as the results from product

  13. Contemporary sea level rise.

    Science.gov (United States)

    Cazenave, Anny; Llovel, William

    2010-01-01

    Measuring sea level change and understanding its causes has considerably improved in the recent years, essentially because new in situ and remote sensing observations have become available. Here we report on most recent results on contemporary sea level rise. We first present sea level observations from tide gauges over the twentieth century and from satellite altimetry since the early 1990s. We next discuss the most recent progress made in quantifying the processes causing sea level change on timescales ranging from years to decades, i.e., thermal expansion of the oceans, land ice mass loss, and land water-storage change. We show that for the 1993-2007 time span, the sum of climate-related contributions (2.85 +/- 0.35 mm year(-1)) is only slightly less than altimetry-based sea level rise (3.3 +/- 0.4 mm year(-1)): approximately 30% of the observed rate of rise is due to ocean thermal expansion and approximately 55% results from land ice melt. Recent acceleration in glacier melting and ice mass loss from the ice sheets increases the latter contribution up to 80% for the past five years. We also review the main causes of regional variability in sea level trends: The dominant contribution results from nonuniform changes in ocean thermal expansion.

  14. Observed Sea-Level Changes along the Norwegian Coast

    Directory of Open Access Journals (Sweden)

    Kristian Breili

    2017-07-01

    Full Text Available Norway’s national sea level observing system consists of an extensive array of tide gauges, permanent GNSS stations, and lines of repeated levelling. Here, we make use of this observation system to calculate relative sea-level rates and rates corrected for glacial isostatic adjustment (GIA along the Norwegian coast for three different periods, i.e., 1960 to 2010, 1984 to 2014, and 1993 to 2016. For all periods, the relative sea-level rates show considerable spatial variations that are largely due to differences in vertical land motion due to GIA. The variation is reduced by applying corrections for vertical land motion and associated gravitational effects on sea level. For 1960 to 2010 and 1984 to 2014, the coastal average GIA-corrected rates for Norway are 2.0 ± 0.6 mm/year and 2.2 ± 0.6 mm/year, respectively. This is close to the rate of global sea-level rise for the same periods. For the most recent period, 1993 to 2016, the GIA-corrected coastal average is 3.5 ± 0.6 mm/year and 3.2 ± 0.6 mm/year with and without inverse barometer (IB corrections, respectively, which is significantly higher than for the two earlier periods. For 1993 to 2016, the coastal average IB-corrected rates show broad agreement with two independent sets of altimetry. This suggests that there is no systematic error in the vertical land motion corrections applied to the tide-gauge data. At the same time, altimetry does not capture the spatial variation identified in the tide-gauge records. This could be an effect of using altimetry observations off the coast instead of directly at each tide gauge. Finally, we note that, owing to natural variability in the climate system, our estimates are highly sensitive to the selected study period. For example, using a 30-year moving window, we find that the estimated rates may change by up to 1 mm/year when shifting the start epoch by only one year.

  15. Holocene climatic fluctuations and periodic changes in the Asian southwest monsoon region

    Science.gov (United States)

    Zhang, Wenxiang; Niu, Jie; Ming, Qingzhong; Shi, Zhengtao; Lei, Guoliang; Huang, Linpei; Long, Xian'e.; Chang, Fengqin

    2018-05-01

    Climatic changes in the Asian southwest monsoon (ASWM) during the Holocene have become a topic of recent studies. It is important to understand the patterns and causes of Holocene climatic changes and their relationship with global changes. Based on the climate proxies and wavelet analysis of Lugu Lake in the ASWM region, the climatic fluctuations and periodic changes in the ASWM region during the Holocene have been reconstructed with a high-precision chronology. The results indicate the intensification of ASWM began to increase with Northern Hemisphere low-latitude solar insolation (LSI) and solar activity during the early Holocene, and gradually decreased during the late Holocene, exhibiting an apparent synchrony with numerous records of ASWM region. Meanwhile, an apparent 1000-a quasi-periodic signal is present in the environment proxies, and it demonstrates that the environmental change in the ASWM region has been driven mainly by LSI and solar activity.

  16. Coralgal reef morphology records punctuated sea-level rise during the last deglaciation.

    Science.gov (United States)

    Khanna, Pankaj; Droxler, André W; Nittrouer, Jeffrey A; Tunnell, John W; Shirley, Thomas C

    2017-10-19

    Coralgal reefs preserve the signatures of sea-level fluctuations over Earth's history, in particular since the Last Glacial Maximum 20,000 years ago, and are used in this study to indicate that punctuated sea-level rise events are more common than previously observed during the last deglaciation. Recognizing the nature of past sea-level rises (i.e., gradual or stepwise) during deglaciation is critical for informing models that predict future vertical behavior of global oceans. Here we present high-resolution bathymetric and seismic sonar data sets of 10 morphologically similar drowned reefs that grew during the last deglaciation and spread 120 km apart along the south Texas shelf edge. Herein, six commonly observed terrace levels are interpreted to be generated by several punctuated sea-level rise events forcing the reefs to shrink and backstep through time. These systematic and common terraces are interpreted to record punctuated sea-level rise events over timescales of decades to centuries during the last deglaciation, previously recognized only during the late Holocene.

  17. Effect of changes in seafloor temperature and sea-level on gas hydrate stability

    Energy Technology Data Exchange (ETDEWEB)

    Garg, S.K.; Pritchett, W. [Science Applications International Corp., San Diego, CA (United States)

    2008-07-01

    Natural gas hydrates occur in oceanic sediments and in permafrost regions around the world. As a greenhouse gas, large amounts of methane released from the global hydrate reservoir would have a significant impact on Earth's climate. The role of methane released by hydrate dissociation in climate change is uncertain. However, changes in global climate such as glaciation and warming can destabilize the hydrates. During the last glacial maximum, the sea level dropped about 100 meters. It has been suggested that the sea-level fall was associated with gas hydrate instability and seafloor slumping. This paper investigated the effect of changes in seafloor temperature and sea level on gas hydrate stability and on gas venting at the seafloor. A one-dimensional numerical computer model (simulator) was developed to describe methane hydrate formation, decomposition, reformation, and distribution with depth below the seafloor in the marine environment. The simulator was utilized to model hydrate distributions at two sites, notably Blake Ridge, located offshore South Carolina and Hydrate Ridge, located off the coast of Oregon. The numerical models for the two sites were conditioned by matching the sulfate, chlorinity, and hydrate distribution measurements. The effect of changes in seafloor temperature and sea-level on gas hydrate stability were then investigated. It was concluded that for Blake Ridge, changes in hydrate concentration were small. Both the changes in seafloor temperature and sea-level led to a substantial increase in gas venting at the seafloor for Hydrate Ridge. 17 refs., 8 figs.

  18. Contemporary Arctic Sea Level

    Science.gov (United States)

    Cazenave, A. A.

    2017-12-01

    During recent decades, the Arctic region has warmed at a rate about twice the rest of the globe. Sea ice melting is increasing and the Greenland ice sheet is losing mass at an accelerated rate. Arctic warming, decrease in the sea ice cover and fresh water input to the Arctic ocean may eventually impact the Arctic sea level. In this presentation, we review our current knowledge of contemporary Arctic sea level changes. Until the beginning of the 1990s, Arctic sea level variations were essentially deduced from tide gauges located along the Russian and Norwegian coastlines. Since then, high inclination satellite altimetry missions have allowed measuring sea level over a large portion of the Arctic Ocean (up to 80 degree north). Measuring sea level in the Arctic by satellite altimetry is challenging because the presence of sea ice cover limits the full capacity of this technique. However adapted processing of raw altimetric measurements significantly increases the number of valid data, hence the data coverage, from which regional sea level variations can be extracted. Over the altimetry era, positive trend patterns are observed over the Beaufort Gyre and along the east coast of Greenland, while negative trends are reported along the Siberian shelf. On average over the Arctic region covered by satellite altimetry, the rate of sea level rise since 1992 is slightly less than the global mea sea level rate (of about 3 mm per year). On the other hand, the interannual variability is quite significant. Space gravimetry data from the GRACE mission and ocean reanalyses provide information on the mass and steric contributions to sea level, hence on the sea level budget. Budget studies show that regional sea level trends over the Beaufort Gyre and along the eastern coast of Greenland, are essentially due to salinity changes. However, in terms of regional average, the net steric component contributes little to the observed sea level trend. The sea level budget in the Arctic

  19. Morphological changes within Florida Bay as a result of sea level rise

    Science.gov (United States)

    Holmes, C. W.

    2011-12-01

    Data from Florida Bay indicates that from 10,000 year BP to 6000 BP, the rate of sea level rise averaged about 10 mm/yr. The rate slowed at the end of this period flooding the shallow shelves surrounding the reef platforms of the western Atlantic. The relative flat South Florida shelf, because of its slight tilt to the southwest is an ideal local to assess the effects of this flooding. From 6000 BP to the present, numerous banks were formed within Florida Bay. A morphological model of bank formation based on the sea level oscillations was constructed from analysis of over 120 cores. These cores record sedimentological changes which are correlated to climatic events. In the central bay, the sediment accumulation was controlled by variations in rate of progressive sea-level rise. The Key West sea-level record shows that sea level has been rising incrementally over the last century. Between 1931 and 1950, sea level rose at a rate of 5 mm/yr. After 1950, it remained stable until 1971, when it again began to rise, but at a rate of 3 mm/yr. On the leeward side of mud banks, these variations resulted in shifts in sediment- accumulation rates, with accretion increasing during rising sea level and decreasing during stable periods. Between late 1970 and early 1972, a sharp jump in sea-level rise occurred that was approximately 10 cm higher than the preceding period. This jump coincided with a strongly positive North Atlantic Oscillation (NAO), a la Niña (negative ENSO), and a negative Pacific Decadal Oscillation (PDO). Water driven northward into Florida Bay eroded banks along the northern coastline, increased sediment accumulation in the northern lakes, and increased accretion rates on the banks. In addition to the sedimentological variations in the central portion of the bay, there was significant changes along the northern fringe. Around 1950, the northern fringe of the bay morphed from a fresh water environment to a marine environment. As a result, carbonate production

  20. A study on Sea Level Change for Coast of Korean Peninsular from Global Warming and Its Influences I

    Energy Technology Data Exchange (ETDEWEB)

    Cho, K.W.; Kim, J.H. [Korea Environment Institute, Seoul (Korea)

    2001-12-01

    The Third Assessment Report(2001) of the Intergovernmental Panel on Climate Change(IPCC) concluded that the global warming will be accelerated during the 21st century due to the human activities. The projected warming will increase the steric sea level rise which have large adverse effects on the natural and human systems in the coastal zone. This study intends to assess the sea level change and potential impacts of the future sea level rise on the coastal zone of the Korean Peninsula in which much socioeconomic activities have been already occurred. The contents of the present study include reviews on climate change and its impact, assessments of the current and future sea level change in the global scale and seas ne,ar Korea, and impact assessment methodology. The second year study(2002) will be focused on the impact assessment on the coastal zone of the Korea, especially on the inundation problem on human dimension due to the steric sea level rise, storm surge, and tide. Based on the tide gauge data, IPCC(2001) assessed the global average sea level rise during the 20th century is in the range of 10{approx}20cm, which is higher than that of 19th century. The contributing elements to the sea level rise are in the order of ocean thermal expansion, melting of glacier, mass balance change of the Greenland and Antarctic ice sheets, and surface and ground water storage and permafrost change. The satellite altimeter data during l990s shows higher trend than the mean trend of tide gauge data during 20th century. The recent high trend of the sea level rise by the altimetry is not clear whether it represents the recent acceleration of the global sea level the differences of the two observation methods, or short observation period of altimetry. In the 21st century, the global mean sea level is projected to increase much due to the acceleration of the warming. Based on the 35 IPCC emission scenarios, the sea level rise in the 21st century will be in the range of 9{approx}88

  1. The evolution of the Dogger Bank, North Sea: A complex history of terrestrial, glacial and marine environmental change

    Science.gov (United States)

    Cotterill, Carol J.; Phillips, Emrys; James, Leo; Forsberg, Carl Fredrik; Tjelta, Tor Inge; Carter, Gareth; Dove, Dayton

    2017-09-01

    This paper presents a summary of the results of a detailed multidisciplinary study of the near surface geology of the Dogger Bank in the southern central North Sea, forming part of a site investigation for a major windfarm development undertaken by the Forewind consortium. It has revealed that the Dogger Bank is internally complex rather than comprising a simple ;layer cake; of the Quaternary sediments as previously thought. Regional and high-resolution seismic surveys have enabled a revised stratigraphic framework to be established for the upper part of this sequence which comprises the Eem (oldest), Dogger Bank, Bolders Bank formations and Botney Cut Formation (youngest), overlain by a typically thin Holocene sequence. Detailed mapping of key horizons identified on the high-resolution seismic profiles has led to the recognition of a series of buried palaeo-landsystems which are characterised by a range of features including; glacial, glacifluvial and fluvial channels, a large-scale glacitectonic thrust-moraine complex with intervening ice-marginal basins, a lacustrine basin and marine ravinement surfaces. Interpretation of these buried landscapes has enabled the development of an environmental change model to explain the evolution of the Dogger Bank. This evolution was driven by the complex interplay between climate change, ice sheet dynamics and sea level change associated with the growth and subsequent demise of the British and Irish and Fennoscandian ice sheets during the Weichselian glaciation. Following the decay of these ice sheets the Dogger Bank entered a period of significant climatic and environmental flux which saw a terrestrial landscape being progressively inundated as sea levels rose during the Holocene.

  2. Development of sea level rise scenarios for climate change assessments of the Mekong Delta, Vietnam

    Science.gov (United States)

    Doyle, Thomas W.; Day, Richard H.; Michot, Thomas C.

    2010-01-01

    Rising sea level poses critical ecological and economical consequences for the low-lying megadeltas of the world where dependent populations and agriculture are at risk. The Mekong Delta of Vietnam is one of many deltas that are especially vulnerable because much of the land surface is below mean sea level and because there is a lack of coastal barrier protection. Food security related to rice and shrimp farming in the Mekong Delta is currently under threat from saltwater intrusion, relative sea level rise, and storm surge potential. Understanding the degree of potential change in sea level under climate change is needed to undertake regional assessments of potential impacts and to formulate adaptation strategies. This report provides constructed time series of potential sea level rise scenarios for the Mekong Delta region by incorporating (1) aspects of observed intra- and inter-annual sea level variability from tide records and (2) projected estimates for different rates of regional subsidence and accelerated eustacy through the year 2100 corresponding with the Intergovernmental Panel on Climate Change (IPCC) climate models and emission scenarios.

  3. Last glacial-Holocene temperatures and hydrology of the Sea of Galilee and Hula Valley from clumped isotopes in Melanopsis shells

    Science.gov (United States)

    Zaarur, Shikma; Affek, Hagit P.; Stein, Mordechai

    2016-04-01

    The carbonate clumped isotope (Δ47) thermometer was applied to fresh water snails (Melanopsis spp.) grown in the waters of the Sea of Galilee and Hula Valley, in the north of Israel. Modern shells, grown at known temperatures agree with the Δ47-T calibration of Zaarur et al. (2013). Fossil Melanopsis shells from 2 locations, Gesher Bnot Ya'aqov (at the southern tip of the Hula Valley) and the Sea of Galilee provide a temperature record for the region during the time interval of the past 20 kyrs. Glacial temperatures are ∼5 °C cooler than mid-Holocene and ∼3 °C cooler than modern, similar to other records in the region. These Δ47-derived temperatures are combined with δ18O of the shell carbonate to calculate the oxygen isotopic composition of the habitat waters. Contrary to global trends and other regional records, reconstructed δ18Owater values increase from the late glacial through the Holocene. This reversed signal reflects a decrease in the relative contribution of snowmelt to the watershed post-LGM and a transition to a more rain dominated inflow. A fairly constant difference in δ18Owater values between the Hula Valley and Sea of Galilee waters, suggests that the hydrological relationship of the two water bodies had remained constant, with the temperature changes playing only a minor role in the extent of evaporation of the Sea of Galilee relative to the Hula.

  4. A Record of Holocene Paleoclimate Evolution from Robertson Bay, Victoria Land, Antarctica

    Science.gov (United States)

    Riesselman, C. R.; Truax, O.; Wilson, G. S.; Parker, R. L.; Yoo, K. C.; Lee, J. I.; Levy, R. H.; Mckay, R. M.

    2017-12-01

    Regionally representative records of how Antarctica responded to the transition from the Last Glacial Maximum into the Holocene are an essential component of understanding the processes by which the Antarctic cryosphere responds to a changing climate. Here, we present a high-resolution record of Holocene Antarctic paleoclimate evolution from a previously unstudied section of the Victoria Land margin. In 2015 the Korea Polar Research Institute collected a 571 cm sediment core, GC57, from Robertson Bay, a protected embayment west of Cape Adare and adjacent to the outlet glaciers of the Transantarctic Mountains. Using diatom assemblages, bulk sediment geochemistry, and the magnetic properties of GC57, we aim to reconstruct the response of the East Antarctic Ice Sheet to warming associated with deglaciation and the Holocene climatic optima at the interface between the Ross Sea and the Southern Ocean. Our multiproxy approach allows us to study sea ice extent, seasonality, ocean stratification and circulation, and primary productivity from the mid-Holocene (7,400 14C year BP) to the present. A sea-ice associated diatom assemblage indicative of summer sea surface temperatures below 0˚C dominates the basal section of GC57. Although diatoms are well preserved, the unit is characterized by low wt% biogenic silica (average 9%) and a high concentration of magnetic minerals, indicating that biogenic production persisted despite substantial terrigenous input into the bay. A rapid transition at 4708 14C yr BP is identified by a steep increase in wt% BSi (average 13%), a decrease in magnetic minerals, and a subtle assemblage change towards sea-ice associated diatoms with slightly warmer temperature tolerances. The novel ramped pyrolosis 14C dating methodology allows us to date the carbon fixed concurrent with deposition and generate a robust age model for GC57 with an accuracy previously difficult to achieve given the uncertainties associated with dating bulk acid insoluble

  5. Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan

    Science.gov (United States)

    Chen, Y.-G.; Liu, J.C.-L.; Shieh, Y.-N.; Liu, T.-K.

    2004-01-01

    A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

  6. Holocene oceanographic changes in SW Labrador Sea, off Newfoundland

    DEFF Research Database (Denmark)

    Sheldon, Christina; Seidenkrantz, Marit-Solveig; Pearce, Christof

    2016-01-01

    Benthic foraminiferal assemblages supported by selected geochemical data from three marine sediment cores collected in Placentia Bay, SE Newfoundland, are used to construct an ~13,000-year-long record of regional oceanographic changes in the SW Labrador Sea. The area is located in the boundary zo....... The Northern Hemisphere neoglacial cooling around 2.8 cal. kyr BP was characterized off SE Newfoundland by a further stabilization of the current system, dominated by the LC with some continued influx of GS water....

  7. Toward explaining the Holocene carbon dioxide and carbon isotope records: Results from transient ocean carbon cycle-climate simulations

    Science.gov (United States)

    Menviel, L.; Joos, F.

    2012-03-01

    The Bern3D model was applied to quantify the mechanisms of carbon cycle changes during the Holocene (last 11,000 years). We rely on scenarios from the literature to prescribe the evolution of shallow water carbonate deposition and of land carbon inventory changes over the glacial termination (18,000 to 11,000 years ago) and the Holocene and modify these scenarios within uncertainties. Model results are consistent with Holocene records of atmospheric CO2 and δ13C as well as the spatiotemporal evolution of δ13C and carbonate ion concentration in the deep sea. Deposition of shallow water carbonate, carbonate compensation of land uptake during the glacial termination, land carbon uptake and release during the Holocene, and the response of the ocean-sediment system to marine changes during the termination contribute roughly equally to the reconstructed late Holocene pCO2 rise of 20 ppmv. The 5 ppmv early Holocene pCO2 decrease reflects terrestrial uptake largely compensated by carbonate deposition and ocean sediment responses. Additional small contributions arise from Holocene changes in sea surface temperature, ocean circulation, and export productivity. The Holocene pCO2 variations result from the subtle balance of forcings and processes acting on different timescales and partly in opposite direction as well as from memory effects associated with changes occurring during the termination. Different interglacial periods with different forcing histories are thus expected to yield different pCO2 evolutions as documented by ice cores.

  8. Sea Level Rise Data Discovery

    Science.gov (United States)

    Quach, N.; Huang, T.; Boening, C.; Gill, K. M.

    2016-12-01

    Research related to sea level rise crosses multiple disciplines from sea ice to land hydrology. The NASA Sea Level Change Portal (SLCP) is a one-stop source for current sea level change information and data, including interactive tools for accessing and viewing regional data, a virtual dashboard of sea level indicators, and ongoing updates through a suite of editorial products that include content articles, graphics, videos, and animations. The architecture behind the SLCP makes it possible to integrate web content and data relevant to sea level change that are archived across various data centers as well as new data generated by sea level change principal investigators. The Extensible Data Gateway Environment (EDGE) is incorporated into the SLCP architecture to provide a unified platform for web content and science data discovery. EDGE is a data integration platform designed to facilitate high-performance geospatial data discovery and access with the ability to support multi-metadata standard specifications. EDGE has the capability to retrieve data from one or more sources and package the resulting sets into a single response to the requestor. With this unified endpoint, the Data Analysis Tool that is available on the SLCP can retrieve dataset and granule level metadata as well as perform geospatial search on the data. This talk focuses on the architecture that makes it possible to seamlessly integrate and enable discovery of disparate data relevant to sea level rise.

  9. Multidecadal variations in the early Holocene outflow of Red Sea Water into the Arabian Sea

    OpenAIRE

    Jung, S.J.A.; Ganssen, G.M.; Davies, G.R.

    2001-01-01

    We present Holocene stable oxygen isotope data from the deep Arabian Sea off Somalia at a decadal time resolution as a proxy for the history of intermediate/upper deep water. These data show an overall δ18O reduction by 0.5‰ between 10 and ~6.5 kyr B.P. superimposed upon short-term δ18O variations at a decadal-centennial timescale. The amplitude of the decadal variations is 0.3‰ prior, and up to 0.6‰ subsequent, to ~8.1 kyr B.P. We conclude from modeling experiments that the short-term δ18O v...

  10. An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

    DEFF Research Database (Denmark)

    Legeais, Jean-Francois; Ablain, Michael; Zawadzki, Lionel

    2018-01-01

    , the sea level ECV has been measured from space by different altimetry missions that have provided global and regional observations of sea level variations. As part of the Climate Change Initiative (CCI) program of the European Space Agency (ESA) (established in 2010), the Sea Level project (SL_cci) aimed...... to provide an accurate and homogeneous long-term satellite-based sea level record. At the end of the first phase of the project (2010-2013), an initial version (v1.1) of the sea level ECV was made available to users (Ablain et al., 2015). During the second phase of the project (2014-2017), improved altimeter...

  11. Greenhouse warming and changes in sea level

    NARCIS (Netherlands)

    Oerlemans, J.

    1989-01-01

    It is likely that the anticipated warming due to the effect of increasing concentration of carbon dioxide and other greenhouse gases will lead to a further and faster rise in world mean sea level. There are many processes in the climate system controlling sea level, but the most important

  12. Heat export from the tropics drives mid to late Holocene palaeoceanographic changes offshore southern Australia

    Science.gov (United States)

    Perner, Kerstin; Moros, Matthias; De Deckker, Patrick; Blanz, Thomas; Wacker, Lukas; Telford, Richard; Siegel, Herbert; Schneider, Ralph; Jansen, Eystein

    2018-01-01

    The Leeuwin Current (LC), an eastern boundary current, transports tropical waters from the Indo-Pacific Warm Pool (IPWP) towards southern latitudes and modulates oceanic conditions offshore southern Australia. New, high-resolution planktic foraminifer assemblage data and alkenone-derived sea surface temperatures (SST) provide an in-depth view on LC variability and mechanisms driving the current's properties during the mid to late Holocene (last c. 7.4 ka BP). Our marine reconstructions highlight a longer-term mid to late Holocene reduction of tropical heat export from the IPWP area into the LC. Mid Holocene (c. 7.4 to 3.5 ka BP) occurrence of high SSTs (>19.5 °C), tropical planktic foraminifera and a well-stratified water column document an enhanced heat export from the tropics. From c. 3.5 ka BP onwards, a weaker LC and a notably reduced tropical heat export cause oceanic cooling offshore southern Australia. The observed mid to late Holocene trends likely result from large-scale changes in the IPWP's heat storage linked to the El Niño-Southern Oscillation (ENSO) phenomenon. We propose that a strong and warm LC occurs in response to a La Niña-like state of ENSO during the mid Holocene. The late Holocene LC cooling, however, results from a shift towards an El Niño-like state and a more variable ENSO system that causes cooling of the IPWP. Superimposed on these longer-term trends we find evidence of distinct late Holocene millennial-scale phases of enhanced El Niño/La Niña development, which appear synchronous with northern hemispheric climatic variability. Phases of dominant El Niño-like states occur parallel to North Atlantic cold phases: the '2800 years BP cooling event', the 'Dark Ages' and the 'Little Ice Age', whereas the 'Roman Warm Period' and the 'Medieval Climate Anomaly' parallel periods of a predominant La Niña-like state. Our findings provide further evidence of coherent interhemispheric climatic and oceanic conditions during the mid to late

  13. Validation on groundwater flow model including sea level change. Modeling on groundwater flow in coastal granite area

    International Nuclear Information System (INIS)

    Hasegawa, Takuma; Miyakawa, Kimio

    2009-01-01

    It is important to verify the groundwater flow model that reproduces pressure head, water chemistry, and groundwater age. However, water chemistry and groundwater age are considered to be influenced by historical events. In this study, sea level change during glacial-interglacial cycle was taken into account for simulating salinity and groundwater age at coastal granite area. As a result of simulation, salinity movement could not catch up with sea level changes, and mixing zone was formed below the fresh-water zone. This mixing zone was observed in the field measurement, and the observed salinities were agreed with simulated results including sea level change. The simulated residence time including sea level change is one-tenth of steady state. The reason is that the saline water was washed out during regression and modern sea-water was infiltrated during transgression. As mentioned before, considering sea level change are important to reproduce salinity and helium age at coastal area. (author)

  14. Looking Back to the Future: Insight on Anthropocene beaches from Holocene and Pleistocene barriers

    Science.gov (United States)

    Dougherty, A. J.; Choi, J. H.; Turney, C. S.; Dosseto, A.

    2017-12-01

    `Super' storms and accelerated rates of sea-level rise are forecast in the Anthropocene, but how coasts will respond (or even if they have started to be impacted) remain uncertain. The onset of this new anthropogenic age is considered mid-1900s when multiple indices including sea level exceed previous Holocene measurements. Centuries of sea surface elevation data, used to project an increase of up to 2m by 2100, show that the current rise started 200 years ago. Similar records of storms or shoreline evolution over these centennial time-scales do not exist. With empirical studies of coastal morphodynamics concentrated during decades of accelerated sea-level rise, present-day beaches can be considered Anthropocene features. To determine the future of vulnerable sandy shorelines, climate change scenarios of increased sea level and storm intensity have been combined with computer models integrating short-term process data with large-scale coastal evolution. The uncertainty in these models can be reduced with longer sea level and storm records as well as filling the gap between detailed beach profile/wave buoy data and generalized barrier stratigraphy. High-resolution chronostratigraphic models necessary to achieve this can be constructed using Light Detection And Ranging (LiDAR), Ground Penetrating Radar (GPR), and Optically Stimulated Luminescence (OSL). Combined GPR, OSL and LiDAR (GOaL) on prograded barriers enables analysis of shorelines back through time, by comparing behaviour since the onset of anthropogenic global warming to that in the preceding millennia. Extracting a record of coastal evolution prior to and since seas began to rise two centuries ago offers the opportunity to detect any difference indicating if/how shorelines have responded. In double barrier systems with composite Holocene and Pleistocene components GOaL can extend the Anthropocene record back to when seas were known to have been higher than today. To demonstrate the potential of GOaL, data

  15. Paleocene-Eocene and Plio-Pleistocene sea-level changes as "species pumps" in Southeast Asia: Evidence from Althepus spiders.

    Science.gov (United States)

    Li, Fengyuan; Li, Shuqiang

    2018-05-17

    Sea-level change has been viewed as a primary driver in the formation of biodiversity. Early studies confirmed that Plio-Pleistocene sea-level changes led to the isolation and subsequent genetic differentiation of Southeast (SE) Asian organisms over short geological timescales. However, long-time consequences of sea-level fluctuations remain unclear. Herein, we analyze the evolutionary history of Althepus (spiders) whose distribution encompasses Indo-Burma and the Sunda shelf islands to understand how sea-level changes over shallow and deep timescales effected their history. Our integrative analyses, including phylogeny, divergence times, ancestral area reconstruction and diversification dynamics, reveal an intricate pattern of diversification, probably triggered by sea-level fluctuations during the Paleocene-Eocene and Plio-Pleistocene. The timing of one early divergence between the Indo-Burmese and Sundaic species coincides with late Paleocene and early Eocene high global sea levels, which induced the formation of inland seaways in the Thai-Malay Peninsula. Subsequent lowered sea levels could have provided a land bridge for its dispersal colonization across the Isthmus of Kra. Analyses suggest that Plio-Pleistocene sea-level rises contributed to recent divergence of many species. Thus, our findings cannot reject the hypothesis that sea-level changes during the Paleocene-Eocene and Plio-Pleistocene played a major role in generating biodiversity in SE Asia; sea-level changes can act as "species pumps". Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Correspondence of Mesozoic Eustatic Sea-Level Change with Palaeoclimate Proxies: Evidence for Glacio-Eustasy?

    Science.gov (United States)

    Simmons, M.; Davies, A.; Gréselle, B.

    2011-12-01

    Large-scale changes in stratigraphic architecture and facies that are brought about by changes in relative sea-level have been the focus of much academic and industry study over the last few decades. The authors, plus numerous colleagues, have studied over 11,000 stratigraphic sections worldwide. By applying biostratigraphic and chemostratigraphic calibration in suitable locations from this dataset it is possible to demonstrate over 250 synchronous global sequence stratigraphic events in the Phanerozoic including over 100 in the Mesozoic. This then raises the question - what causes globally synchronous eustatic sea-level change? To answer this question requires an understanding of both the pace and amplitude of the observed eustatic sea-level change. In successions where duration can be deduced from orbital forcing cycles, our observed sea-level changes appear to be relatively rapid - less than 500,000 years, for example, for sea-level rises in the Late Jurassic. The amplitude of such rises is in the order of tens of metres. Such rates and amplitudes as inferred from our global model preclude tectonism as a primary driver and implicate glacio-eustacy as a key driving mechanism, even in supposed "greenhouse times". Given the clear economic importance of understanding the underlying mechanisms driving this eustatic change we have compiled records of key isotopic proxies through the entire Mesozoic in an effort to explore the relationship between global sea-level and palaeoclimate. Our research reveals a clear link between many large-scale maximum flooding events with known episodes of palaeoclimatic warming and between climatic cooling events and lowstand intervals, further implicating glacio-eustacy. In addition to the isotopic proxy evidence we have also compiled direct indicators for the occurrence of cold polar conditions, including the presence of ice sheets, in the Mesozoic (e.g. tillites, glendonites). This has been incorporated into plate tectonic

  17. An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

    Science.gov (United States)

    Legeais, Jean-François; Ablain, Michaël; Zawadzki, Lionel; Zuo, Hao; Johannessen, Johnny A.; Scharffenberg, Martin G.; Fenoglio-Marc, Luciana; Joana Fernandes, M.; Baltazar Andersen, Ole; Rudenko, Sergei; Cipollini, Paolo; Quartly, Graham D.; Passaro, Marcello; Cazenave, Anny; Benveniste, Jérôme

    2018-02-01

    Sea level is a very sensitive index of climate change since it integrates the impacts of ocean warming and ice mass loss from glaciers and the ice sheets. Sea level has been listed as an essential climate variable (ECV) by the Global Climate Observing System (GCOS). During the past 25 years, the sea level ECV has been measured from space by different altimetry missions that have provided global and regional observations of sea level variations. As part of the Climate Change Initiative (CCI) program of the European Space Agency (ESA) (established in 2010), the Sea Level project (SL_cci) aimed to provide an accurate and homogeneous long-term satellite-based sea level record. At the end of the first phase of the project (2010-2013), an initial version (v1.1) of the sea level ECV was made available to users (Ablain et al., 2015). During the second phase of the project (2014-2017), improved altimeter standards were selected to produce new sea level products (called SL_cci v2.0) based on nine altimeter missions for the period 1993-2015 (https://doi.org/10.5270/esa-sea_level_cci-1993_2015-v_2.0-201612; Legeais and the ESA SL_cci team, 2016c). Corresponding orbit solutions, geophysical corrections and altimeter standards used in this v2.0 dataset are described in detail in Quartly et al. (2017). The present paper focuses on the description of the SL_cci v2.0 ECV and associated uncertainty and discusses how it has been validated. Various approaches have been used for the quality assessment such as internal validation, comparisons with sea level records from other groups and with in situ measurements, sea level budget closure analyses and comparisons with model outputs. Compared with the previous version of the sea level ECV, we show that use of improved geophysical corrections, careful bias reduction between missions and inclusion of new altimeter missions lead to improved sea level products with reduced uncertainties on different spatial and temporal scales. However, there

  18. Age accuracy and resolution of Quaternary corals used as proxies for sea level

    Science.gov (United States)

    Edinger, E. N.; Burr, G. S.; Pandolfi, J. M.; Ortiz, J. C.

    2007-01-01

    The accuracy of global eustatic sea level curves measured from raised Quaternary reefs, using radiometric ages of corals at known heights, may be limited by time-averaging, which affects the variation in coral age at a given height. Time-averaging was assessed in uplifted Holocene reef sequences from the Huon Peninsula, Papua New Guinea, using radiocarbon dating of coral skeletons in both horizontal transects and vertical sequences. Calibrated 2σ age ranges varied from 800 to 1060 years along horizontal transects, but weighted mean ages calculated from 15-18 dates per horizon were accurate to a resolution within 154-214 yr. Approximately 40% of the variability in age estimate resulted from internal variability inherent to 14C estimates, and 60% was due to time-averaging. The accuracy of age estimates of sea level change in studies using single dated corals as proxies for sea level is probably within 1000 yr of actual age, but can be resolved to ≤ 250 yr if supported by dates from analysis of a statistical population of corals at each stratigraphic interval. The range of time-averaging among reef corals was much less than that for shelly benthos. Ecological time-averaging dominated over sedimentological time averaging for reef corals, opposite to patterns reported from shelly benthos in siliciclastic environments.

  19. Estimation of past sea-level variations based on ground-penetrating radar mapping of beach-ridges - preliminary results from Feddet, Faxe Bay, eastern Denmark

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Nielsen, Lars; Clemmensen, Lars B

    2011-01-01

    Estimates of past sea-level variations based on different methods and techniques have been presented in a range of studies, including interpretation of beach ridge characteristics. In Denmark, Holocene beach ridge plains have been formed during the last c. 7700 years, a period characterised by both...... isostatic uplift and changes in eustatic sea-level, and therefore represent an archive of past relative sea-level variations. Here, we present preliminary results from investigation of beach ridges from Feddet, a small peninsula located in Faxe Bay (Baltic Sea) in the eastern part of Denmark. Feddet has...... been chosen as a key-locality in this project, as it is located relatively close to the current 0-isobase of isostatic rebound. GPR reflection data have been acquired with shielded 250 MHz Sensors & software antennae along a number of profile lines across beach ridge and swale structures of the Feddet...

  20. SEA LEVEL AND PALAEOCLIMATIC CHANGES IN THE SOUTH AND MIDDLE CASPIAN SEA REGION SINCE THE LATEGLACIAL FROM PALYNOLOGICAL ANALYSES OF MARINE SEDIMENT CORES

    Directory of Open Access Journals (Sweden)

    Suzanne Leroy

    2010-01-01

    Full Text Available A review of pollen, spores, non-pollen palynomorphs and dinocyst analyses made in the last two decades is proposed here. Building on spare palynological analyses before 1990, a series of new projects have allowed taking cores in the deeper parts of the Caspian Sea, hence providing access to low-stand sediment. However, still nowadays no complete record exists for the Holocene. The first steps towards quantification of the palynological spectra have been taken. Some of the most urgent problems to solve are the uncertainties related to radiocarbon dating, which are especially acute in the Caspian Sea.

  1. Depositional Architecture of Late Pleistocene-Holocene Coastal Alluvial-fan System in the Coastal Range, Taiwan

    Science.gov (United States)

    Chen, S. T.; Chen, W. S.

    2016-12-01

    Holocene marine deposits rest above the fluvial deposits. The crustal high uplift rates of relative sea-level changes led to form a well-developed multiple Holocene marine terraces.

  2. Holocene climate and fjord glaciations in Northeast Greenland: implications for IRD deposition in the North Atlantic

    DEFF Research Database (Denmark)

    Reeh, Niels

    2004-01-01

    been released by intensive sub-glacial melting during the long stay of the ice-islands in coastal waters. The Holocene glacial geological record from Northeast Greenland is compared to the record of ice rafted debris (IRD) from North Atlantic deep-sea sediment cores. The comparison shows that transport...... by icebergs in the form of basal debris is unlikely to be the dominant transport mechanism of IRD to deposition sites in the North Atlantic during the Holocene. The ice rafted debris is more likely to be carried at the surface of sea- (or glacier) ice. This supports the result of previous studies by other...... workers that changes of atmospheric and ocean-surface circulation and temperature are the likely causes of Holocene cycles in IRD concentration in North Atlantic deep-sea sediments....

  3. Mid-Holocene hydrology change in the south Taihu area of the Yangtze delta plain, China, and its relationship to the development of Neolithic cultures

    Science.gov (United States)

    Chen, T.; Ryves, D.; Wang, Z.; Lewis, J.

    2017-12-01

    During the middle Holocene, the hydrological environments in the Taihu Plain, Yangtze Delta, China, varied tremendously under the influence of sea-level and climate change. Simultaneously, several Neolithic cultures, such as, the Majiabang, Songze, and Liangzhu culture, developed in this region. Basing on AMS14C dating, diatom identification, measurements of C-N elements and their stable isotopes of sediments from core DTX4 and DTX10, obtained in the East Tiaoxi Plain, south Taihu plain, we discussed the influence of hydrology changes on the development of Neolithic cultures. The results revealed that the East Tiaoxi River plain was in an estuary (the Palaeo-Taihu Estuary) condition at 7500 cal. yr BP, undergoing elevated in-fill in response to rapid sea-level rise. After 7500 cal. yr BP, low salinity conditions occurred, likely influenced by the Yangtze freshwater evidenced by constant occurrence of Aulacoseira granulata, which implied Yangtze runoff discharged along the channel of Palaeo-incised Taihu valley into the Hangzhou Bay during the middle Holocene. Sea-water penetration interrupted after 7000 cal. yr BP caused by an abrupt sea-level rise. During 6500-5600 cal. yr BP, sea-water retreated gradually, corresponding to the infilling of Palaeo-Taihu Estuary. Combing records from previously studied cores in the Taihu plain, stable freshwater condition (or dry land) established in most area of the Taihu plain after 5600 cal. yr BP due to the closure of the Palaeo-Taihu Estuary. We speculate that the low-salinity marsh started at about 7500-7000 cal. yr BP probably attracted the early Majiabang people to live around the Palaeo-Taihu Estuary. The sea water penetration between 7000-6500 cal. yr BP matches the left of the late Majiabang and the early-middle Songze people lived in the east of the Palaeo-Taihu Estuary, to the north and east of the Taihu Plain. The context of stable freshwater condition (or dry land) in the East Tiaoxi River plain promoted the

  4. Sedimentary Evidence for a Rapid Sea Level Rise at 7,600 cal yr BP from North-Central Cuba

    Science.gov (United States)

    Peros, M. C.; Agosta G'meiner, A. M.; Collins, S.

    2016-12-01

    A lack of high-resolution relative sea level (RSL) proxy data has meant that the pattern of early Holocene RSL change in the Caribbean is poorly understood. A RSL curve published by Toscano and Macintyre (2003) using inter-tidal mangrove peats and submerged corals suggests RSL underwent a relatively fast and `smooth' curvilinear increase during the Holocene. However, others, such as Blanchon and Shaw (1995), suggest that RSL increased rapidly at around 7600 cal yr BP, in response to the final stages of the melting of the Laurentide Ice Sheet (melt water pulse 1C or catastrophic rise event 3). We investigated this question using multi-proxy data from a flooded sinkhole (Cenote Jennifer) on the north coast of central Cuba. Cenote Jennifer is located 7 m above mean sea level and 2 km from the Bahamas Channel and appears to have a high degree of connectivity with the ocean through a network of underground caverns. The water depth is 13 m and the bottommost 5 m is anoxic. A sediment core collected from Cenote Jennifer was studied using loss-on-ignition, pollen analysis, high-resolution XRF core-scanning, and grain size analysis. An age-depth model was generated for the core by AMS dating. The results show that the bottommost stratigraphic unit ( 9000 to 7600 cal yr BP) is a fine-grained carbonate-rich mud (i.e., marl). This unit abruptly transitions into finely laminated organic-rich sediment from 7600 cal yr BP to the present. The pollen analysis shows that the sinkhole supported a cattail (Typha) community until 7600 cal yr BP, indicating low water levels ( 1 m). At 7600 cal yr BP, the cattail community disappeared and the vegetation of the surrounding bedrock became dominated by a thorny coastal scrubland. In addition, a 3 cm thick fining-upward siliciclastic unit is present immediately above the marl-organic contact, suggesting: 1) a marine sediment source given the limestone-dominated nature of the region, and 2) the presence of a short-duration, high

  5. Middle Holocene Organic Carbon and Biomarker Records from the South Yellow Sea: Relationship to the East Asian Monsoon

    Science.gov (United States)

    Zou, Liang; Hu, Bangqi; Li, Jun; Dou, Yanguang; Xie, Luhua; Dong, Liang

    2018-03-01

    The East Asian monsoon system influences the sedimentation and transport of organic matter in East Asian marginal seas that is derived from both terrestrial and marine sources. In this study, we determined organic carbon (OC) isotope values, concentrations of marine biomarkers, and levels of OC and total nitrogen (TN) in core YSC-1 from the central South Yellow Sea (SYS). Our objectives were to trace the sources of OC and variations in palaeoproductivity since the middle Holocene, and their relationships with the East Asian monsoon system. The relative contributions of terrestrial versus marine organic matter in core sediments were estimated using a two-end-member mixing model of OC isotopes. Results show that marine organic matter has been the main sediment constituent since the middle Holocene. The variation of terrestrial organic carbon concentration (OCter) is similar to the EASM history. However, the variation of marine organic carbon concentration (OCmar) is opposite to that of the EASM curve, suggesting OCmar is distinctly influenced by terrestrial material input. Inputs of terrestrial nutrients into the SYS occur in the form of fluvial and aeolian dust, while concentrations of nutrients in surface water are derived mainly from bottom water via the Yellow Sea circulation system, which is controlled by the East Asian winter monsoon (EAWM). Variations in palaeoproductivity represented by marine organic matter and biomarker records are, in general, consistent with the recent EAWM intensity studies, thus, compared with EASM, EAWM may play the main role to control the marine productivity variations in the SYS.

  6. High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution.

    Science.gov (United States)

    Lecavalier, Benoit S; Fisher, David A; Milne, Glenn A; Vinther, Bo M; Tarasov, Lev; Huybrechts, Philippe; Lacelle, Denis; Main, Brittany; Zheng, James; Bourgeois, Jocelyne; Dyke, Arthur S

    2017-06-06

    We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4-5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800-7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland.

  7. Holocene reef accretion: southwest Molokai, Hawaii, U.S.A.

    Science.gov (United States)

    Engels, Mary S.; Fletcher, Charles H.; Field, Michael E.; Storlazzi, Curt D.; Grossman, Eric E.; Rooney, John J.B.; Conger, Christopher L.; Glenn, Craig

    2004-01-01

    extension across Hawaii in general, is controlled by wave-induced near-bed shear stress related to refracted North Pacific swell. Holocene accretion patterns here also reflect the long-term influence of wave-induced near-bed shear stress from north swell during late Holocene time. This finding is consistent with other studies (e.g., Grigg 1998; Cabioch et al. 1999) that reflect the dominance of swell energy and sea level in controlling modern and late Holocene accretion elsewhere in Hawaii and across the Pacific and Indian oceans. Notably, however, this result is refined and clarified for Hawaii in the hypothesis of Rooney et al. (2003) stating that enhancement of the El Niño Southern Oscillation beginning approximately 5000 years ago led to increased north swell energy and signaled the end to net accretion along exposed coastlines in Hawaii. The exposure of Hale O Lono to north swell and the age of sea floor there (ca. 4,800 cal yr BP), coupled with the lack of north swell incidence at Hikauhi and the continuous accretion that has occurred there over the last millennium, strongly supports the ENSO reef hypothesis as outlined by Rooney et al. (2003). Other factors controlling Holocene reef accretion at the study site are relative sea-level position and rate of rise, and wave sheltering by Laau Point. Habitat suitable for reef accretion on the southwest shore of Molokai has shrunk throughout the Holocene.

  8. Carbon sequestration in Southeast Asian tropical peatlands over the Holocene period: large-scale hydrological controls

    Science.gov (United States)

    Dommain, R.; Couwenberg, J.; Cobb, A.; Gandois, L.; Kai, F.; Su'ut, N.; Abu Salim, K.; Harvey, C. F.; Glaser, P. H.; Joosten, H.

    2012-12-01

    support the hypothesis that the water table elevation and not temperature is the primary control of the carbon balance of tropical peatlands. The period of fastest peatland expansion and highest CAR was the wettest period in the Holocene with the lowest hydraulic gradient imposed by the highstand in sea-level. The period with the lowest and nearly quiescent CAR was associated with higher drought stress and a steeper hydraulic gradient, implying lower water tables. The remarkably high carbon sequestration rates of Southeast Asian peatlands can be explained by the high production of woody biomass throughout the year under waterlogged conditions. Woody organic matter is principally resistant to decomposition in an anaerobic setting causing rapid rates of carbon accumulation as long as the water table remains high. Increased drought severity, possibly in association with changes in the El Niño-Southern Oscillation under a warmer future climate could potentially switch Southeast Asian carbon sequestering peatlands to carbon sources.

  9. Mid-Holocene paleoclimatic changes and solar activity in San'in District, mid-latitude North Pacific Region

    Science.gov (United States)

    Okazaki, Y.; Seto, K.; Sakai, T.; Ooki, A.; yamada, K.; Dettman, D. L.

    2011-12-01

    Evidence shows that solar activity influences climate on a global scale. In the mid-latitude region, climate change is expected to change precipitation patterns. Concurrently, variation in solar activity may influence phytoplankton productivity. It seems that these changes should be recorded in sediment and organic matter deposits in coastal lagoons. In this study, we discuss the relationship between climate change and solar activity in the mid-Holocene in the northern hemisphere mid-latitude region based on grain size analysis, total organic carbon (TOC) content and organic carbon accumulation rates (Corg A.R.) in coastal lagoon sediment core samples. The INB core was drilled to produce a high resolution record of Holocene paleoenvironmental change in the San'in District, western Japan. The core is 19.17m in total length and is divided into Unit I~VII by lithofacies. Holocene sediment, primarily organic silt, forms Unit III and above in this core. Unit III was deposited from 8.4 to 5.4 ka, when sea level rose during the Jomon transgression; its depositional environment is a coastal lagoon. Progradation of the river mouth during the sea level rise lead to an increase in the C/N ratio of organic matter. Unit IV contains the volcanic Shigaku pyroclastic flow (the sixth stage of volcanic activity of the Sanbe volcano), and Unit V reflects deposition in a freshwater lake or swamp. Above this aggredational sediments were deposited by small rivers. This study focused on the coastal lagoon sediments of Unit III (8.4 to 5.4 ka); we carried out CNS elemental analysis and grain size analysis with a resolution of approximately five years. TOC content is variable and increases from 0.5 to 5%. Variation in TOC content is relatively well correlated with atmospheric radiocarbon 14C (Delta 14C) and therefore with solar activity, although the relationship is unclear in the upper portion of Unit III. The trend in Corg A.R. is different than TOC contents, about 40g/m/yr at ~8ka and

  10. Projecting future sea level

    Science.gov (United States)

    Cayan, Daniel R.; Bromirski, Peter; Hayhoe, Katharine; Tyree, Mary; Dettinger, Mike; Flick, Reinhard

    2006-01-01

    California’s coastal observations and global model projections indicate that California’s open coast and estuaries will experience increasing sea levels over the next century. Sea level rise has affected much of the coast of California, including the Southern California coast, the Central California open coast, and the San Francisco Bay and upper estuary. These trends, quantified from a small set of California tide gages, have ranged from 10–20 centimeters (cm) (3.9–7.9 inches) per century, quite similar to that estimated for global mean sea level. So far, there is little evidence that the rate of rise has accelerated, and the rate of rise at California tide gages has actually flattened since 1980, but projections suggest substantial sea level rise may occur over the next century. Climate change simulations project a substantial rate of global sea level rise over the next century due to thermal expansion as the oceans warm and runoff from melting land-based snow and ice accelerates. Sea level rise projected from the models increases with the amount of warming. Relative to sea levels in 2000, by the 2070–2099 period, sea level rise projections range from 11–54 cm (4.3–21 in) for simulations following the lower (B1) greenhouse gas (GHG) emissions scenario, from 14–61 cm (5.5–24 in) for the middle-upper (A2) emission scenario, and from 17–72 cm (6.7–28 in) for the highest (A1fi) scenario. In addition to relatively steady secular trends, sea levels along the California coast undergo shorter period variability above or below predicted tide levels and changes associated with long-term trends. These variations are caused by weather events and by seasonal to decadal climate fluctuations over the Pacific Ocean that in turn affect the Pacific coast. Highest coastal sea levels have occurred when winter storms and Pacific climate disturbances, such as El Niño, have coincided with high astronomical tides. This study considers a range of projected future

  11. Late Post-glacial Sea Level Rise and Its Effects On Human Activity In Asia

    Science.gov (United States)

    Oppenheimer, S. J.

    Three rapid post-glacial sea-level rises flooded coastlines with large continental shelves. The last of these, shortly before the interglacial optimum c.7,500BP, not only changed coastal Neolithic societies, but may also have stimulated maritime skills. Two Asian examples explore these aspects. First, during the Mid-Holocene, the Arabian Gulf transgressed as far inland as Ur probably laying down Woolley's famous Ur Flood silt layer between 7,000-5,500 BP. Stratigraphy and dating suggests the phase of rapid sea level rise immediately preceded the start of the 'Ubaid pottery period. Red-slipped Uruk pottery and copper items then appear from about 6,000BP, but above Woolley's silt layer. The Sumerian King Lists also record a major upheaval and dynastic change after 'the Flood'. Second, the final flooding of the Sunda shelf in Southeast Asia was followed by a maritime extension of human occupation from Northern Melanesia south into the Solomon Islands 6,000 years ago. Simultaneously, further west on the north coast of New Guinea, new archaeological assemblages ap- pear beneath a silt layer left by a pro-grading 6,000 year-old inland sea. The presence of arboriculture items such as betel nuts and the contemporary arrival of dogs and pigs in the same region suggests intrusion from Southeast Asia. This supports Solheim's suggestion that rapid sea-level rise on the eastern edge of the Sunda Shelf stimulated maritime skills and invention in Southeast Asia. This may have provided the initial stimulus to the first maritime expansion that was later to colonise the whole Pacific.

  12. Impacts of climate change and sea level rise to Danish near shore ecosystems

    International Nuclear Information System (INIS)

    Vestergaard, P.

    2001-01-01

    Salt marshes and sand dunes are important types of coastal, terrestrial nature, which like other terrestrial ecosystems will be sensible to the future changes in climate, which have been predicted. Due to the processes acting in their morphogenesis and in the development and composition of their ecosystems, they will not least be influenced by sea level rise. Especially a strong impact of a sea level rise of about 50 cm (midrange of the projected global sea level rise) for the next century can be expected on Danish salt marshes, considering their limited vertical range (50-100 cm). (LN)

  13. Coastal lagoon systems as indicator of Holocene sea-level development in a periglacial soft-sediment setting: Samsø, Denmark

    DEFF Research Database (Denmark)

    Sander, Lasse; Fruergaard, Mikkel; Johannessen, Peter N.

    2014-01-01

    . Stratigraphy, grain-size distribution, fossil and organic matter content of cores retrieved from the lagoons were analyzed and compared. Age control was established using radiocarbon and optically stimulated luminescence dating. Our data produced a surprisingly consistent pattern for the sedimentary......Confined shallow-water environments are encountered many places along the coast of the inner Danish waters. Despite their common occurrence, these environments have rarely been studied as sedimentary archives. In this study we set out to trace back changes in relative sea-level and associated...... geomorphological responses in sediment cores retrieved from coastal lagoon systems on the island of Samsø, central Denmark. In the mid-Atlantic period, the post-glacial sea-level rise reached what is today the southern Kattegat Sea. Waves, currents and tides began to erode the unconsolidated moraine material...

  14. Lithostratigraphy, depositional history and sea level changes of the Cauvery Basin, southern India

    Directory of Open Access Journals (Sweden)

    Muthuvairvasamy Ramkumar

    2003-01-01

    Full Text Available The sedimentary sequence exposed in the erstwhile Tiruchirapalli district hosts a more or less complete geological record of the Upper Cretaceous-Tertiary period. Systematic field mapping, collation of data on the micro-meso scale lithology, sedimentary structures, petrography, faunal assemblage and facies relationships of these rocks, in the light of modern stratigraphic concepts, helped to enumerate the lithostratigraphic setup and depositional history of the basin. Spatial and temporal variations of the lithologies and revised stratigraphic units are presented in this paper. Many high frequency sea level cycles (presumably fourth or higher order which stack up to form third order sea level cycles (six in number, which in turn form part of second order cycles (two in number, including seven eustatic sea level peaks, have been recorded in this basin. Trend analysis of sea level curves indicates a gradual increase of the sea level from Barremian to Coniacian and a gradual decrease from Coniacian to Danian. Such lasting sea level trends had their influence on the sedimentation pattern and facies association. It is inferred that depositional bathymetry was maintained at a shallow-moderate level, primarily influenced by a lack of major subsidence during the depositional history of this basin. The study also revealed a prevalent simple basin filling process and dominant control by sea level changes, rather than tectonic movements over the depositional regime.

  15. Seismic Facies of Pleistocene–Holocene Channel-fill Deposits in Bawean Island and Adjacent Waters, Southeast Java Sea

    Directory of Open Access Journals (Sweden)

    Ali Albab

    2017-08-01

    Full Text Available The late Pleistocene-Holocene stratigraphic architecture of the Bawean Island and surrounding waters, southeast Java Sea has been analyzed by using sparker seismic profiles. Geological interpretation of these seismic profiles revealed the widespread distribution of paleochannels with different shape and size in the present-day Java Sea. Two channel types can be distinguished based on its morphology: U-shaped channels in the western part and V-shaped channels in the eastern part. The stratigraphic successions were grouped into two major seismic units separated by different seismic boundaries. Characters of marine and fluvial deposits were determined based on seismic boundaries and internal reflectors. Three seismic facies can be identified within late Pleistocene – Holocene incised channel fills associated with SB2. The internal structure of incised-channels consist of chaotic reflector at the bottom, covered by parallel–sub parallel and almost reflection-free indicating the homogenous sediment deposited during the succession.

  16. A stable-isotope tree-ring timescale of the Late Glacial/Holocene boundary

    International Nuclear Information System (INIS)

    Becker, Bernd; Kromer, Bernd; Trimborn, Peter

    1991-01-01

    Late Glacial and Holocene tree-ring chronologies, like deep-sea sediments or polar ice cores, contain information about past environments. Changes in tree-ring growth rates can be related to past climate anomalies and changes in the isotope composition of tree-ring cellulose reflect changes in the composition of the atmosphere and the hydrosphere. We have established a 9,928-year absolutely dated dendrochronological record of Holocene oak (Quercus robur, Quercus petraea)-and a 1,604-year floating Late Glacial and Early Holocene chronology of pine (Pinus sylvestris) from subfossil tree remnants deposited in alluvial terraces of south central European rivers. The pine sequence provides records of dendro-dated 14 C, 13 C and 2 H patterns for the late Younger Dryas and the entire Preboreal (10,100-9,000 yr BP). Through the use of dendrochronology, radiocarbon age calibration and stable isotope analysis, we suggest that the Late Glacial/Holocene transition may be identified and dated by 13 C and 2 H tree-ring chronologies. (author)

  17. Sea level changes from monthly solutions of ice sheet mass balance

    DEFF Research Database (Denmark)

    Barletta, Valentina Roberta; Sørensen, Louise Sandberg; Forsberg, René

    We present mass change time series at basin scale for both Greenland and Antarctica, de-rived from GRACE data, and use these data to find the associated global sea level changes. We use two independent methods for GRACE ice mass loss estimation, including use of different GIA models and estimatio...

  18. Estuarine Response to River Flow and Sea-Level Rise under Future Climate Change and Human Development

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhaoqing; Wang, Taiping; Voisin, Nathalie; Copping, Andrea E.

    2015-04-01

    Understanding the response of river flow and estuarine hydrodynamics to climate change, land-use/land-cover change (LULC), and sea-level rise is essential to managing water resources and stress on living organisms under these changing conditions. This paper presents a modeling study using a watershed hydrology model and an estuarine hydrodynamic model, in a one-way coupling, to investigate the estuarine hydrodynamic response to sea-level rise and change in river flow due to the effect of future climate and LULC changes in the Snohomish River estuary, Washington, USA. A set of hydrodynamic variables, including salinity intrusion points, average water depth, and salinity of the inundated area, were used to quantify the estuarine response to river flow and sea-level rise. Model results suggest that salinity intrusion points in the Snohomish River estuary and the average salinity of the inundated areas are a nonlinear function of river flow, although the average water depth in the inundated area is approximately linear with river flow. Future climate changes will shift salinity intrusion points further upstream under low flow conditions and further downstream under high flow conditions. In contrast, under the future LULC change scenario, the salinity intrusion point will shift downstream under both low and high flow conditions, compared to present conditions. The model results also suggest that the average water depth in the inundated areas increases linearly with sea-level rise but at a slower rate, and the average salinity in the inundated areas increases linearly with sea-level rise; however, the response of salinity intrusion points in the river to sea-level rise is strongly nonlinear.

  19. Holocene Millennial Time Scale Hydrological Changes In Central-east Africa

    Science.gov (United States)

    Jolly, D.; Bonnefille, R.; Beaufort, L.

    The Holocene hydrological changes of a tropical swamp is reconstructed using a high resolution pollen record (ca 50 yrs) from the Kuruyange valley (Burundi, Africa, 3°35'S, 29°41'E), at 2000 m elevation. The sequence was dated by 10 radiocarbon dates, allowing reconstruction between ca 12 500 and 1000 cal yr B.P. In the Kuruyange swamp, peat accumulated rapidly at a sedimentation rate varying from 0.73 (prior to 6200 cal yr B.P.) to 1.51 mm/yr (during the late Holocene). A pollen index of water table, based on a ratio of aquatic versus non-aquatic plants has been used in order to test the hypothesis of hydrological constraints on the swampy ecosystem. Eight arid phases are evidenced by the index minima at 12 200, 11 200, 9900, 8600, 6500, 5000, 3400, 1600 cal yr B.P. The good agreement existing between this index and independent data such as (i) low-resolution East-African lake level reconstruct ions (Gillespie et al., 1983) and (ii) ?18O analyses from Arabian Sea (Sirocko et al., 1993) suggests the water table level responds to the monsoon dynamic. The Index varies periodically with a combination of 1/1515, 1/880 and 1/431 years-1 frequencies, revealed by time series analyses (Blackman-Tukey and Maximum Entropy). The extrapolation of the composite curve based on these 3 periodicities show that two major climatic events defined in the high latitudes between 1000 and 660 cal yr B.P. (Medieval Warm Period) and between 500 and 100 cal yr B.P. (Little Ice Age) are recorded in our data and show respectively high and low stands of the water table. Our results support some previous pollen-derived climate estimates in Ethiopia done by Bonnefille and Umer (1994). Moreover, the "1500 year" cycle registered in our data from the tropics, already evidenced in higher latitudes (Wijmstra et al., 1984; Bondet al., 1997; Schulz et al., 1999; Bond et al., 2001) support the hypothesis of strong teleconnections between tropical/subtropical and polar climates during the deglaciation

  20. Assessing Flood Risk Under Sea Level Rise and Extreme Sea Levels Scenarios: Application to the Ebro Delta (Spain)

    Science.gov (United States)

    Sayol, J. M.; Marcos, M.

    2018-02-01

    This study presents a novel methodology to estimate the impact of local sea level rise and extreme surges and waves in coastal areas under climate change scenarios. The methodology is applied to the Ebro Delta, a valuable and vulnerable low-lying wetland located in the northwestern Mediterranean Sea. Projections of local sea level accounting for all contributions to mean sea level changes, including thermal expansion, dynamic changes, fresh water addition and glacial isostatic adjustment, have been obtained from regionalized sea level projections during the 21st century. Particular attention has been paid to the uncertainties, which have been derived from the spread of the multi-model ensemble combined with seasonal/inter-annual sea level variability from local tide gauge observations. Besides vertical land movements have also been integrated to estimate local relative sea level rise. On the other hand, regional projections over the Mediterranean basin of storm surges and wind-waves have been used to evaluate changes in extreme events. The compound effects of surges and extreme waves have been quantified using their joint probability distributions. Finally, offshore sea level projections from extreme events superimposed to mean sea level have been propagated onto a high resolution digital elevation model of the study region in order to construct flood hazards maps for mid and end of the 21st century and under two different climate change scenarios. The effect of each contribution has been evaluated in terms of percentage of the area exposed to coastal hazards, which will help to design more efficient protection and adaptation measures.

  1. Abrupt decadal-to-centennial hydroclimate changes in the Mediterranean region since the mid-Holocene

    Science.gov (United States)

    Hu, Hsun-Ming; Shen, Chuan-Chou; Jiang, Xiuyang; Wang, Yongjin; Mii, Horng-Sheng; Michel, Véronique

    2016-04-01

    A series of severe drought events in the Mediterranean region over the past two decades has posed a threat on both human society and biosystem. Holocene hydrological dynamics can offer valuable clues for understanding future climate and making proper adaption strategy. Here, we present a decadal-resolved stalagmite record documenting various hydroclimatic fluctuations in the north central Mediterranean region since the middle Holocene. The stalagmite δ18O sequence shows dramatic instability, characterized by abrupt shifts between dry and wet conditions Mycenaean Greece, Akkadian Empire, Egyptian Old Kingdom, and Uruk, occurred during the drought events, suggesting an important role of climate impact on human civilization. The unstable hydroclimate evolution is related to transferred North Atlantic Oscillation states. Rate of rapid transfer of precipitation patterns, which can be pin-pointed by our good chronology, improves the prediction to future climate changes in North Atlantic region. We also found that a strong correlation between this stalagmite δ18O and sea surface temperatures especially in Pacific Ocean. This agreement suggests a distant interregional climate teleconnection.

  2. Present-day sea level rise: a synthesis

    International Nuclear Information System (INIS)

    Cazenave, A.; Llovel, W.; Lombard, A.

    2008-01-01

    Measuring sea level change and understanding its causes have improved considerably in the recent years, essentially because new in situ and remote sensing data sets have become available. Here we report on the current knowledge of present-day sea level change. We briefly present observational results on sea level change from satellite altimetry since 1993 and tide gauges for the past century. We next discuss recent progress made in quantifying the processes causing sea level change on time scales ranging from years to decades, i.e., thermal expansion, land ice mass loss and land water storage change. For the 1993-2003 decade, the sum of climate-related contributions agree well (within the error bars) with the altimetry-based sea level, half of the observed rate of rise being due to ocean thermal expansion, land ice plus land waters explaining the other half. Since about 2003, thermal expansion increase has stopped, whereas the sea level continues to rise, although at a reduced rate compared to the previous decade (2.5 mm/yr versus 3.1 mm/yr). Recent increases in glacier melting and ice mass loss from the ice sheets appear able to account alone for the rise in sea level reported over the last five years. (authors)

  3. Paleoclimate from ice cores : abrupt climate change and the prolonged Holocene

    International Nuclear Information System (INIS)

    White, J.W.C.

    2001-01-01

    Ice cores provide valuable information about the Earth's past climates and past environments. They can also help in predicting future climates and the nature of climate change. Recent findings in ice cores have shown large and abrupt climate changes in the past. This paper addressed abrupt climate changes and the peculiar nature of the Holocene. An abrupt climate change is a shift of 5 degrees C in mean annual temperature in less than 50 years. This is considered to be the most threatening aspect of potential future climate change since it leaves very little time for adaptation by humans or any other part of the Earth's ecosystem. This paper also discussed the arrival of the next glacial period. In the past 50 years, scientists have recognized the importance of the Earth's orbit around the sun in pacing the occurrence of large ice sheets. The timing of orbital forcing suggests that the Earth is overdue for the next major glaciation. The reason for this anomaly was discussed. Abrupt climate shifts seem to be caused by mode changes in sensitive points in the climate system, such as the North Atlantic Deep Water Formation and its impact on sea ice cover in the North Atlantic. These changes have been observed in ice cores in Greenland but they are not restricted to Greenland. Evidence from Antarctic ice cores suggest that abrupt climate change may also occur in the Southern Hemisphere. The Vostok ice core in Antarctica indicates that the 11,000 year long interglacial period that we are in right now is longer than the previous four interglacial periods. The Holocene epoch is unique because both methane and carbon dioxide rise in the last 6,000 years, an atypical response from these greenhouse gases during an interglacial period. It was suggested that the rise in methane can be attributed to human activities. 13 refs., 2 figs

  4. Intermittent sea-level acceleration

    Science.gov (United States)

    Olivieri, M.; Spada, G.

    2013-10-01

    Using instrumental observations from the Permanent Service for Mean Sea Level (PSMSL), we provide a new assessment of the global sea-level acceleration for the last ~ 2 centuries (1820-2010). Our results, obtained by a stack of tide gauge time series, confirm the existence of a global sea-level acceleration (GSLA) and, coherently with independent assessments so far, they point to a value close to 0.01 mm/yr2. However, differently from previous studies, we discuss how change points or abrupt inflections in individual sea-level time series have contributed to the GSLA. Our analysis, based on methods borrowed from econometrics, suggests the existence of two distinct driving mechanisms for the GSLA, both involving a minority of tide gauges globally. The first effectively implies a gradual increase in the rate of sea-level rise at individual tide gauges, while the second is manifest through a sequence of catastrophic variations of the sea-level trend. These occurred intermittently since the end of the 19th century and became more frequent during the last four decades.

  5. Holocene productivity changes off Adélie Land (East Antarctica) on decadal to millennial timescales

    NARCIS (Netherlands)

    Denis, D.; Crosta, X.; Schmidt, S.; Carson, D.; Ganeshram, R.; Renssen, H.; Crespin, J.; Ther, O.; Billy, I.; Giraudeau, J.

    2009-01-01

    This study presents the first high-resolution multiproxy investigation of primary productivity (PP) during the Holocene from the Antarctic continental margins. Micropaleontological and geochemical data from the sediment core MD03-2601,associated to sea ice model outputs, give unprecedented insights

  6. Global Climate Change Consequences Changing the Middle Sea Level in the Brazilian Coast: Impacts on Ceará State

    Science.gov (United States)

    Lacerda, E. G.; Pires, L. B. M.; Pinto, V. K. E.

    2015-12-01

    Since the Industrial Revolution, man started to generate increasing amounts of waste and pollutants, which on a large scale in the long term is causing a series of climate change consequences, both globally as well as locally. One of the many effects of these changes has been reflected in the ocean levels, depending on various factors. Thus, the population living in coastal areas suffers from the negative effects of the advancement of ocean waters. The coast of northeastern Brazil is an example of this, especially the state of Ceará coast. The state of Ceará has 573 km of coastline, a region that has suffered extensive erosion, in which the Middle Sea Level (MSL) changes exert a significant influence. The coastal plain is a strip of land of small extent, with an average width of 2.5 km, formed depending on the availability of high sediment stocks provided through the action of wind, marine, or river processes, individually in combination with each other. In many beaches it is observed that the strip of beach is narrow due to the presence of topographic elevations carved into sharp cliffs. Between periods of high tide and low tide, often rocky beach features are observed that have recently formed. The waves control the stretches of beach which are mostly sandy. This paper presents a survey about the evidence already apparent on the rise in the MSL and correlates it with the advance of the sea on the coast of Ceará, as well as assesses the possible consequences of this process. Therefore, a literature search was conducted in relevant scientific publications. The data used are from the station "Global Sea Level Observing System - GLOSS" which maintains a tide gauge installed in Ceará in Fortaleza. The analyses show that the phenomenon has caused a lot of inconvenience to the people, streets have disappeared, as well as several buildings located along the coast. The sea advances destroyed beaches and have promoted an accelerated level of erosion, changing the

  7. Contribution of climate-driven change in continental water storage to recent sea-level rise

    Science.gov (United States)

    Milly, P. C. D.; Cazenave, A.; Gennero, C.

    2003-01-01

    Using a global model of continental water balance, forced by interannual variations in precipitation and near-surface atmospheric temperature for the period 1981–1998, we estimate the sea-level changes associated with climate-driven changes in storage of water as snowpack, soil water, and ground water; storage in ice sheets and large lakes is not considered. The 1981–1998 trend is estimated to be 0.12 mm/yr, and substantial interannual fluctuations are inferred; for 1993–1998, the trend is 0.25 mm/yr. At the decadal time scale, the terrestrial contribution to eustatic (i.e., induced by mass exchange) sea-level rise is significantly smaller than the estimated steric (i.e., induced by density changes) trend for the same period, but is not negligibly small. In the model the sea-level rise is driven mainly by a downtrend in continental precipitation during the study period, which we believe was generated by natural variability in the climate system. PMID:14576277

  8. The Barbados Sea Level Record

    Science.gov (United States)

    Fairbanks, R. G.; Mortlock, R. A.; Abdul, N. A.; Wright, J. D.; Cao, L.; Mey, J. L.

    2013-12-01

    Additional offshore drill cores, nearly 100 new radiometric dates, and more than 1000 kilometers of Multibeam mapping greatly enhance the Barbados Sea Level record. Extensive Multibeam mapping around the entire island covers approximately 2650 km2 of the sea bottom and now integrates the offshore reef topography and Barbados Sea Level Record with the unparalleled onshore core collection, digital elevation maps, and Pleistocene sea level record spanning the past one million years. The reef crest coral, Acropora palmata, remains the stalwart indicator of sea level for many reasons that are validated by our redundant sea level records and redundant dating via Th/U and Pa/U analyses. Microanalysis and densitometry studies better explain why Acropora palmata is so well preserved in the Pleistocene reef records and therefore why it is the species of choice for sea level reconstructions and radiometric dating. New drill cores into reefs that formed during Marine Isotope Stage 3 lead us to a model of diagenesis that allows us to better prospect for unaltered coral samples in older reefs that may be suitable for Th/U dating. Equally important, our diagenesis model reinforces our rigorous sample quality criteria in a more quantitative manner. The Barbados Sea Level record has a sampling resolution of better than 100 years throughout much of the last deglaciation showing unprecedented detail in redundant drill cores. The Melt Water Pulses (MWP1A and MWP1B) are well resolved and the intervening interval that includes the Younger Dryas reveals sea level changes in new detail that are consistent with the terrestrial records of ice margins (see Abdul et al., this section). More than 100 paired Th/U and radiocarbon ages place the Barbados Sea Level Record unambiguously on the radiocarbon time scale for direct comparisons with the terrestrial records of ice margin changes.

  9. Revised paleoenvironmental analysis of the Holocene portion of the Barbados sea-level record: Cobbler's Reef revisited

    Science.gov (United States)

    Toscano, Marguerite A.

    2016-06-01

    Sample elevations corrected for tectonic uplift and assessed relative to local modeled sea levels provide a new perspective on paleoenvironmental history at Cobbler's Reef, Barbados. Previously, 14C-dated surface samples of fragmented Acropora palmata plotted above paleo sea level based on their present (uplifted) elevations, suggesting supratidal rubble deposited during a period of extreme storms (4500-3000 cal BP), precipitating reef demise. At several sites, however, A. palmata persisted, existing until ~370 cal BP. Uplift-corrected A. palmata sample elevations lie below the western Atlantic sea-level curve, and ~2 m below ICE-6G-modeled paleo sea level, under slow rates of sea-level rise, negating the possibility that Cobbler's Reef is a supratidal storm ridge. Most sites show limited age ranges from corals likely damaged/killed on the reef crest, not the mixed ages of rubble ridges, strongly suggesting the reef framework died off in stages over 6500 yr. Reef crest death assemblages invoke multiple paleohistoric causes, from ubiquitous hurricanes to anthropogenic impacts. Comparison of death assemblage ages to dated regional paleotempestological sequences, proxy-based paleotemperatures, recorded hurricanes, tsunamis, European settlement, deforestation, and resulting turbidity, reveals many possible factors inimical to the survival of A. palmata along Cobbler's Reef.

  10. Impact of glacial/interglacial sea level change on the ocean nitrogen cycle

    Science.gov (United States)

    Ren, Haojia; Sigman, Daniel M.; Martínez-García, Alfredo; Anderson, Robert F.; Chen, Min-Te; Ravelo, Ana Christina; Straub, Marietta; Wong, George T. F.; Haug, Gerald H.

    2017-08-01

    The continental shelves are the most biologically dynamic regions of the ocean, and they are extensive worldwide, especially in the western North Pacific. Their area has varied dramatically over the glacial/interglacial cycles of the last million years, but the effects of this variation on ocean biological and chemical processes remain poorly understood. Conversion of nitrate to N2 by denitrification in sediments accounts for half or more of the removal of biologically available nitrogen (“fixed N”) from the ocean. The emergence of continental shelves during ice ages and their flooding during interglacials have been hypothesized to drive changes in sedimentary denitrification. Denitrification leads to the occurrence of phosphorus-bearing, N-depleted surface waters, which encourages N2 fixation, the dominant N input to the ocean. An 860,000-y record of foraminifera shell-bound N isotopes from the South China Sea indicates that N2 fixation covaried with sea level. The N2 fixation changes are best explained as a response to changes in regional excess phosphorus supply due to sea level-driven variations in shallow sediment denitrification associated with the cyclic drowning and emergence of the continental shelves. This hypothesis is consistent with a glacial ocean that hosted globally lower rates of fixed N input and loss and a longer residence time for oceanic fixed N—a “sluggish” ocean N budget during ice ages. In addition, this work provides a clear sign of sea level-driven glacial/interglacial oscillations in biogeochemical fluxes at and near the ocean margins, with implications for coastal organisms and ecosystems.

  11. Contrasting records of sea-level change in the eastern and western North Atlantic during the last 300 years

    Science.gov (United States)

    Long, A. J.; Barlow, N. L. M.; Gehrels, W. R.; Saher, M. H.; Woodworth, P. L.; Scaife, R. G.; Brain, M. J.; Cahill, N.

    2014-02-01

    We present a new 300-year sea-level reconstruction from a salt marsh on the Isle of Wight (central English Channel, UK) that we compare to other salt-marsh and long tide-gauge records to examine spatial and temporal variability in sea-level change in the North Atlantic. Our new reconstruction identifies an overall rise in relative sea level (RSL) of c. 0.30 m since the start of the eighteenth century at a rate of 0.9±0.3 mm yr. Error-in-variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset. The reconstruction is broadly comparable to other tide-gauge and salt-marsh records from the European Atlantic, demonstrating coherence in sea level in this region over the last 150-300 years. In contrast, we identify significant differences in the rate and timing of RSL with records from the east coast of North America. The absence of a strong late 19th/early 20th century RSL acceleration contrasts with that recorded in salt marsh sediments along the eastern USA coastline, in particular in a well-dated and precise sea-level reconstruction from North Carolina. This suggests that this part of the North Carolina sea level record represents a regionally specific sea level acceleration. This is significant because the North Carolina record has been used as if it were globally representative within semi-empirical parameterisations of past and future sea-level change. We conclude that regional-scale differences of sea-level change highlight the value of using several, regionally representative RSL records when calibrating and testing semi-empirical models of sea level against palaeo-records. This is because by using records that potentially over-estimate sea-level rise in the past such models risk over-estimating sea-level rise in the future.

  12. The impact of early Holocene Arctic Shelf flooding on climate in an atmosphere–ocean–sea–ice model

    NARCIS (Netherlands)

    Blaschek, M.; Renssen, H.

    2013-01-01

    Glacial terminations are characterized by a strong rise in sea level related to melting ice sheets. This rise in sea level is not uniform all over the world, because regional effects (uplift and subsidence of coastal zones) are superimposed on global trends. During the early Holocene the Siberian

  13. 1300 km long late Pleistocene-Holocene shelf edge barrier reef system along the western continental shelf of India: Occurrence and significance

    Digital Repository Service at National Institute of Oceanography (India)

    Vora, K.H.; Wagle, B.G.; Veerayya, M.; Almeida, F.; Karisiddaiah, S.M.

    . It is surmised that coral/algal reef growth commenced with the advent of the Holocene trangression and favorable antecedent topography, and continued until early Holocene. Subsequently, rapid sea level rise drowned the reefs. The shelf edge reefs, therefore...

  14. What are driving the long-term Caspian Sea level change?

    Science.gov (United States)

    Chen, J.

    2017-12-01

    Caspian Sea level (CSL) has undergone substantial fluctuations during the past several hundred years. The causes over the entire historical period are uncertain, but we investigate here large changes seen in the past several decades. We use climate model predicted precipitation (P), evaporation (E), and observed river runoff (R) to reconstruct long-term CSL changes for 1979-2015, and show that PER (P-E+R) flux predictions agree very well with observed CSL changes. The observed rapid CSL increase (about 12.74 cm/yr) and significant drop ( -6.72 cm/yr) during the periods 1979-1995 and 1996-2015 are well accounted for by integrated PER flux predictions of +12.38 and -6.79 cm/yr, respectively. We show that increased evaporation rates over the Caspian Sea play a dominant role in reversing the increasing trend in CSL during the past 37 years. The current long-term decline in CSL is expected to continue into the foreseeable future, under global warming scenarios.

  15. Climate change, sea-level rise, and conservation: keeping island biodiversity afloat.

    Science.gov (United States)

    Courchamp, Franck; Hoffmann, Benjamin D; Russell, James C; Leclerc, Camille; Bellard, Céline

    2014-03-01

    Island conservation programs have been spectacularly successful over the past five decades, yet they generally do not account for impacts of climate change. Here, we argue that the full spectrum of climate change, especially sea-level rise and loss of suitable climatic conditions, should be rapidly integrated into island biodiversity research and management. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Influence of Climate Change and Trophic Coupling across Four Trophic Levels in the Celtic Sea

    Science.gov (United States)

    Lauria, Valentina; Attrill, Martin J.; Pinnegar, John K.; Brown, Andrew; Edwards, Martin; Votier, Stephen C.

    2012-01-01

    Climate change has had profound effects upon marine ecosystems, impacting across all trophic levels from plankton to apex predators. Determining the impacts of climate change on marine ecosystems requires understanding the direct effects on all trophic levels as well as indirect effects mediated by trophic coupling. The aim of this study was to investigate the effects of climate change on the pelagic food web in the Celtic Sea, a productive shelf region in the Northeast Atlantic. Using long-term data, we examined possible direct and indirect ‘bottom-up’ climate effects across four trophic levels: phytoplankton, zooplankton, mid-trophic level fish and seabirds. During the period 1986–2007, although there was no temporal trend in the North Atlantic Oscillation index (NAO), the decadal mean Sea Surface Temperature (SST) in the Celtic Sea increased by 0.66±0.02°C. Despite this, there was only a weak signal of climate change in the Celtic Sea food web. Changes in plankton community structure were found, however this was not related to SST or NAO. A negative relationship occurred between herring abundance (0- and 1-group) and spring SST (0-group: p = 0.02, slope = −0.305±0.125; 1-group: p = 0.04, slope = −0.410±0.193). Seabird demographics showed complex species–specific responses. There was evidence of direct effects of spring NAO (on black-legged kittiwake population growth rate: p = 0.03, slope = 0.0314±0.014) as well as indirect bottom-up effects of lagged spring SST (on razorbill breeding success: p = 0.01, slope = −0.144±0.05). Negative relationships between breeding success and population growth rate of razorbills and common guillemots may be explained by interactions between mid-trophic level fish. Our findings show that the impacts of climate change on the Celtic Sea ecosystem is not as marked as in nearby regions (e.g. the North Sea), emphasizing the need for more research at regional scales. PMID:23091621

  17. Influence of climate change and trophic coupling across four trophic levels in the Celtic Sea.

    Directory of Open Access Journals (Sweden)

    Valentina Lauria

    Full Text Available Climate change has had profound effects upon marine ecosystems, impacting across all trophic levels from plankton to apex predators. Determining the impacts of climate change on marine ecosystems requires understanding the direct effects on all trophic levels as well as indirect effects mediated by trophic coupling. The aim of this study was to investigate the effects of climate change on the pelagic food web in the Celtic Sea, a productive shelf region in the Northeast Atlantic. Using long-term data, we examined possible direct and indirect 'bottom-up' climate effects across four trophic levels: phytoplankton, zooplankton, mid-trophic level fish and seabirds. During the period 1986-2007, although there was no temporal trend in the North Atlantic Oscillation index (NAO, the decadal mean Sea Surface Temperature (SST in the Celtic Sea increased by 0.66 ± 0.02 °C. Despite this, there was only a weak signal of climate change in the Celtic Sea food web. Changes in plankton community structure were found, however this was not related to SST or NAO. A negative relationship occurred between herring abundance (0- and 1-group and spring SST (0-group: p = 0.02, slope = -0.305 ± 0.125; 1-group: p = 0.04, slope = -0.410 ± 0.193. Seabird demographics showed complex species-specific responses. There was evidence of direct effects of spring NAO (on black-legged kittiwake population growth rate: p = 0.03, slope = 0.0314 ± 0.014 as well as indirect bottom-up effects of lagged spring SST (on razorbill breeding success: p = 0.01, slope = -0.144 ± 0.05. Negative relationships between breeding success and population growth rate of razorbills and common guillemots may be explained by interactions between mid-trophic level fish. Our findings show that the impacts of climate change on the Celtic Sea ecosystem is not as marked as in nearby regions (e.g. the North Sea, emphasizing the need for more research at regional scales.

  18. Tropical vegetation evidence for rapid sea level changes associated with Heinrich Events

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Catalina; Dupont, Lydie M, E-mail: catalina@uni-bremen.d, E-mail: dupont@uni-bremen.d [MARUM - Centre for Marine Environmental Sciences, University of Bremen, Leobener Strasse, D-28359 Germany (Germany)

    2010-03-15

    A Cariaco Basin pollen record shows the development of tropical salt marshes during marine isotope stage 3. Rapid and abrupt expansions of salt marsh vegetation in tropical South America are associated with north Atlantic Heinrich Events stadials (HE-stadials). Intervals of salt marsh expansion have an internal structure, which consists of a recurrent alternation of species that starts with pollen increments of Chenopodiaceae, that are followed by increments of grasses, and subsequently by increments of Cyperaceae. This pattern suggests a successional process that is determined by the close relationship between sea-level and plant community dynamics. The salt tolerant Chenopodiaceae, indicate hypersaline intertidal environments, which were most likely promoted by extremely dry atmospheric conditions. Rapid sea-level rise characterizes the onset of HE-stadials, causing the continued recruitment of pioneer species, which are the only ones tolerating rapid rates of disturbance. Once sea-level rise decelerates, marsh plants are able to trap and stabilize sediments, favouring the establishment of more competitive species. These results add to the scarce knowledge on the dynamics of tropical salt marsh ecosystems, and provide independent paleoclimatic evidence on sea-level changes following Antarctic climate variability.

  19. Diatom Stratigraphy of FA-1 Core, Qarun Lake, Records of Holocene Environmental and Climatic Change in Faiyum Oasis, Egypt

    Directory of Open Access Journals (Sweden)

    Zalat Abdelfattah A.

    2017-06-01

    Full Text Available This study evaluates changes in the environmental and climatic conditions in the Faiyum Oasis during the Holocene based on diatom analyses of the sediment FA-1 core from the southern seashore of the Qarun Lake. The studied FA-1 core was 26 m long and covered the time span ca. 9.000 cal. yrs BP. Diatom taxa were abundant and moderately to well-preserved throughout the core sediments. Planktonic taxa were most abundant than the benthic and epiphytic forms, which were very rare and sparsely distributed. The most dominant planktonic genera were Aulacoseira and Stephanodiscus followed by frequently distribution of Cyclostephanos and Cyclotella species. The stratigraphic distribution patterns of the recorded diatoms through the Holocene sediments explained five ecological diatom groups. These groups represent distinctive environmental conditions, which were mainly related to climatic changes through the early and middle Holocene, in addition to anthropogenic activity during the late Holocene. Comparison of diatom assemblages in the studied sediment core suggests that considerable changes occurred in water level as well as salinity. There were several high stands of the freshwater lake level during humid, warmer-wet climatic phases marked by dominance of planktonic, oligohalobous and alkaliphilous diatoms alternated with lowering of the lake level and slight increases in salinity and alkalinity during warm arid conditions evident by prevalence of brackish water diatoms.

  20. Variability and change of sea level and its components in the Indo-Pacific region during the altimetry era

    Science.gov (United States)

    Wu, Quran; Zhang, Xuebin; Church, John A.; Hu, Jianyu

    2017-03-01

    Previous studies have shown that regional sea level exhibits interannual and decadal variations associated with the modes of climate variability. A better understanding of those low-frequency sea level variations benefits the detection and attribution of climate change signals. Nonetheless, the contributions of thermosteric, halosteric, and mass sea level components to sea level variability and trend patterns remain unclear. By focusing on signals associated with dominant climate modes in the Indo-Pacific region, we estimate the interannual and decadal fingerprints and trend of each sea level component utilizing a multivariate linear regression of two adjoint-based ocean reanalyses. Sea level interannual, decadal, and trend patterns primarily come from thermosteric sea level (TSSL). Halosteric sea level (HSSL) is of regional importance in the Pacific Ocean on decadal time scale and dominates sea level trends in the northeast subtropical Pacific. The compensation between TSSL and HSSL is identified in their decadal variability and trends. The interannual and decadal variability of temperature generally peak at subsurface around 100 m but that of salinity tend to be surface-intensified. Decadal temperature and salinity signals extend deeper into the ocean in some regions than their interannual equivalents. Mass sea level (MassSL) is critical for the interannual and decadal variability of sea level over shelf seas. Inconsistencies exist in MassSL trend patterns among various estimates. This study highlights regions where multiple processes work together to control sea level variability and change. Further work is required to better understand the interaction of different processes in those regions.

  1. Rates and limits of climatic change: Discussion of possible targets; Rates and limits of temperature, precipitation, and sea-level changes

    Energy Technology Data Exchange (ETDEWEB)

    Gleick, P H [Pacific Inst. for SiDES, Berkeley, CA (US); Sassin, W [Landl (AT)

    1990-10-01

    The rate of sea-level rise over the next century is likely to accelerate rapidly and exceed rates of rise experienced over the last several thousand years. Under these conditions, adverse effects on natural ecosystems such as coastal marshes and coral reef islands would be widely observable by 2050, and would be noticeable in vulnerable ecosystems by the year 2000, even under low sea-level rise scenario. Non-linearities and sudden events such as storm surges and a change in storm frequency and intensity could lead to damages even earlier. Similarly, change in temperature and precipitation patterns far greater than those experienced in the last 10000to 100000 years seem likely unless strong actions are taken soon. Rates of change in temperature, precipitation, and sea level over geologic time have often exceeded the rates expected over the next century from global warming. These large excursions, however, were often accompanied by dramatic changes in ecosystems and by large species extinctions, and they occurred when no human infrastructure existed. The adaptive abilities of natural ecosystems can be used to define targets of maximum rates of rise. For coral reef islands and coastal marshes, the maximum rate of accretion of materials is 10 to 15 mm/yr. At this rate, however, many reefs and marshes that accrete materials at slower rates will be inundated and destroyed. Average rates of accretion for marshes are lower - between 2 and 5 mm/yr, and between 5 and 10 mm/yr for coral reefs. Even at these lower rates, some ecosystem losses are to be expected. This information leads to a recommended target for the rate of sea-level rise of between 20 and 50 mm per decade, and a target for absolute sea-level rise of between 0.2 and 0.5 above the 1990 global mean sea level. (authors).

  2. Sea level rise and the geoid: factor analysis approach

    Directory of Open Access Journals (Sweden)

    Alexey Sadovski

    2013-08-01

    Full Text Available Sea levels are rising around the world, and this is a particular concern along most of the coasts of the United States. A 1989 EPA report shows that sea levels rose 5-6 inches more than the global average along the Mid-Atlantic and Gulf Coasts in the last century. The main reason for this is coastal land subsidence. This sea level rise is considered more as relative sea level rise than global sea level rise. Thus, instead of studying sea level rise globally, this paper describes a statistical approach by using factor analysis of regional sea level rates of change. Unlike physical models and semi-empirical models that attempt to approach how much and how fast sea levels are changing, this methodology allows for a discussion of the factor(s that statistically affects sea level rates of change, and seeks patterns to explain spatial correlations.

  3. Monitoring sea level and sea surface temperature trends from ERS satellites

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per; Beckley, B.

    2002-01-01

    Data from the two ESA satellites ERS-1 and ERS-2 are used in global and regional analysis of sea level and sea surface temperature trends over the last, 7.8 years. T he ERS satellites and in the future the ENVISAT satellite provide unique opportunity for monitoring both changes in sea level and sea...

  4. Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy

    Science.gov (United States)

    Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

    2010-01-01

    Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

  5. ACCELERATION OF SEA LEVEL RISE OVER MALAYSIAN SEAS FROM SATELLITE ALTIMETER

    Directory of Open Access Journals (Sweden)

    A. I. A. Hamid

    2016-09-01

    Full Text Available Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS. Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

  6. Acceleration of Sea Level Rise Over Malaysian Seas from Satellite Altimeter

    Science.gov (United States)

    Hamid, A. I. A.; Din, A. H. M.; Khalid, N. F.; Omar, K. M.

    2016-09-01

    Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS). Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA) are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

  7. Present day sea level changes: observation and causes; Les variations actuelles du niveau de la mer: observations et causes

    Energy Technology Data Exchange (ETDEWEB)

    Lombard, A

    2005-11-15

    Whereas sea level has changed little over the last 2000 years, it has risen at a rate of about 2 mm/year during the 20. century. This unexpected sea level rise has been attributed to the anthropogenic global warming, recorded over several decades. Sea level variations have been measured globally and precisely for about 12 years due to satellite altimeter missions Topex/Poseidon and Jason-1. These observations indicate a global mean sea level rise of about 3 mm/year since 1993, a value significantly larger than observed during previous decades. Recent observations have allowed us to quantify the various climatic factors contributing to observed sea level change: thermal expansion of sea water due to ocean warming, melting of mountain glaciers and ice sheets, and changes in the land water reservoirs. A water budget based on these new observations allows us to partly explain the observed sea level rise. In particular, we show that the thermal expansion explains only 25% of the secular sea level rise as recorded by tide-gauges over the last 50 years, while it contributes about 50% of sea level rise observed over the last decade. Meanwhile, recent studies show that glacier and ice sheet melting could contribute the equivalent of 1 mm/year in sea level rise over the last decade. In addition, the high regional variability of sea level trends revealed by satellite altimetry is mainly due to thermal expansion. There is also an important decadal spatio-temporal variability in the ocean thermal expansion over the last 50 years, which seems to be controlled by natural climate fluctuations. We question for the first time the link between the decadal fluctuations in the ocean thermal expansion and in the land reservoirs, and indeed their climatic contribution to sea level change. Finally a preliminary analysis of GRACE spatial gravimetric observations over the oceans allows us to estimate the seasonal variations in mean sea level due to ocean water mass balance variations

  8. Revisiting global mean sea level budget closure : Preliminary results from an integrative study within ESA's Climate Change Initiative -Sea level Budget Closure-Climate Change Initiative

    Science.gov (United States)

    Palanisamy, H.; Cazenave, A. A.

    2017-12-01

    The global mean sea level budget is revisited over two time periods: the entire altimetry era, 1993-2015 and the Argo/GRACE era, 2003-2015 using the version '0' of sea level components estimated by the SLBC-CCI teams. The SLBC-CCI is an European Space Agency's project on sea level budget closure using CCI products. Over the entire altimetry era, the sea level budget was performed as the sum of steric and mass components that include contributions from total land water storage, glaciers, ice sheets (Greenland and Antarctica) and total water vapor content. Over the Argo/GRACE era, it was performed as the sum of steric and GRACE based ocean mass. Preliminary budget analysis performed over the altimetry era (1993-2015) results in a trend value of 2.83 mm/yr. On comparison with the observed altimetry-based global mean sea level trend over the same period (3.03 ± 0.5 mm/yr), we obtain a residual of 0.2 mm/yr. In spite of a residual of 0.2 mm/yr, the sea level budget result obtained over the altimetry era is very promising as this has been performed using the version '0' of the sea level components. Furthermore, uncertainties are not yet included in this study as uncertainty estimation for each sea level component is currently underway. Over the Argo/GRACE era (2003-2015), the trend estimated from the sum of steric and GRACE ocean mass amounts to 2.63 mm/yr while that observed by satellite altimetry is 3.37 mm/yr, thereby leaving a residual of 0.7 mm/yr. Here an ensemble GRACE ocean mass data (mean of various available GRACE ocean mass data) was used for the estimation. Using individual GRACE data results in a residual range of 0.5 mm/yr -1.1 mm/yr. Investigations are under way to determine the cause of the vast difference between the observed sea level and the sea level obtained from steric and GRACE ocean mass. One main suspect is the impact of GRACE data gaps on sea level budget analysis due to lack of GRACE data over several months since 2011. The current action plan

  9. Evidence for coral island formation during rising sea level in the central Pacific Ocean

    Science.gov (United States)

    Kench, Paul S.; Owen, Susan D.; Ford, Murray R.

    2014-02-01

    The timing and evolution of Jabat Island, Marshall Islands, was investigated using morphostratigraphic analysis and radiometric dating. Results show the first evidence of island building in the Pacific during latter stages of Holocene sea level rise. A three-phase model of development of Jabat is presented. Initially, rapid accumulation of coarse sediments on Jabat occurred 4800-4000 years B.P. across a reef flat higher than present level, as sea level continued to rise. During the highstand, island margins and particularly the western margin accreted vertically to 2.5-3.0 m above contemporary ridge elevations. This accumulation phase was dominated by sand-size sediments. Phase three involved deposition of gravel ridges on the northern reef, as sea level fell to present position. Jabat has remained geomorphically stable for the past 2000 years. Findings suggest reef platforms may accommodate the oldest reef islands in atoll systems, which may have profound implications for questions of prehistoric migration through Pacific archipelagos.

  10. Sea level and climate variations

    NARCIS (Netherlands)

    Oerlemans, J.

    1985-01-01

    Review paper, ESA Symposium on Application of Satellite Data to Climate Modelling. Alpbach (Austria) Sea level is an essential component of the climate system, on which many human activities in the coastal zone depend. Climate variations leading to changes in relative sea level are

  11. A multiproxy fjord sediment record of Holocene climate change from the subantarctic Auckland Islands

    Science.gov (United States)

    Browne, I. M.; Moy, C. M.; Wilson, G. S.; Neil, H.; Riesselman, C. R.

    2014-12-01

    The Southern Hemisphere Westerly Winds (SHWW) and the associated oceanic fronts have a major influence on atmospheric and oceanic circulation in the Southern Hemisphere. Sediment cores recovered from fjords along the eastern margin of the sub-Antarctic Auckland Islands (51°S, 166°E) are ideally located to sensitively record changes in the strength and position of the SHWW throughout the Holocene. A 5.75m core from Hanfield Inlet preserves both marine and terrestrial environmental components, which we use to develop a multiproxy record of past climatic conditions. This core, composed entirely of brown marine mud and silt, was recovered from a depth of 44m. Based on the entrance sill depth of the fjord (10mbsl) and our knowledge of regional sea level rise, we infer that the base of the core will be early Holocene in age, which will be confirmed using radiocarbon age dating. Benthic foraminiferal assemblages (125-500μm fraction) in surface and downcore samples are dominated by three taxa, Nonionellina flemingi, Cassidulina carinata and Quinqueloculina seminula. These species are either shallow infaunal or infaunal. We will use stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope geochemistry of the benthic foraminifera Nonionellina flemingi, Bolivina cf. earlandi, Trifarina angulosa, Bulimina marginata f. marginata and Cibicides species (all identified from Rose Bengal stained box-core samples) to reconstruct water column fluctuations associated with frontal migration. These results will compliment bulk sediment C and N concentration and isotope reconstructions of terrestrial organic matter delivery to fjord sub-basins over the past 12,000 years.

  12. Biomarker Evidence of Relatively Stable Community Structure in the Northern South China Sea during the Last Glacial and Holocene

    Directory of Open Access Journals (Sweden)

    Juan He

    2008-01-01

    Full Text Available High-resolution molecular abundance records for several marine biomarkers during the last glacial and Holocene have been generated for core MD05-2904 (19 _ 116 _ 2066 mwater depth from the northern South China Sea. The UK' 37 SST record indicates a 4.4 C cooling during the Last Glacial Maximum for this site, consistent with previous reconstructions. The contents of C37 alkenones, dinosterol, brassicasterol, and C30 alkyl diols are used as productivity proxies for haptophytes, dinoflagellates, diatoms, and eustigmatophytes, respectively. These records reveal that both individual phytoplankton group and total productivity increased by several factors during the LGM compared with those for the Holocene, in response to increased nutrient supply. However, the community structure based on biomarker percentages remained relatively stable during the last glacial-Holocene transition, although there were short-term oscillations.

  13. Late Quaternary sea level and environmental changes from relic ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Keywords. Late Quaternary sea level; western margin of India; subsidence; uplift; depositional environment. ...... sea level rise by about 80m (between 12,000 and. 7,000 yr BP) or, .... from the Florida Keys; Palaentology 28 189–206. Carballo ...

  14. Postglacial relative sea-level history of the Prince Rupert area, British Columbia, Canada

    Science.gov (United States)

    Letham, Bryn; Martindale, Andrew; Macdonald, Rebecca; Guiry, Eric; Jones, Jacob; Ames, Kenneth M.

    2016-12-01

    This paper presents a history of relative sea level (RSL) change for the last 15,000 years in the Prince Rupert region on the northern coast of British Columbia, Canada. One hundred twenty-three radiocarbon ages of organic material from isolation basin cores, sediment sequence exposures, and archaeological sites having a recognized relation to past sea levels constrain postglacial RSL. The large number of new measurements relating to past sea-level provides a well constrained RSL curve that differs in significant ways from previously published results. After deglaciation following the Last Glacial Maximum, the region experienced an isostatically-induced rapid RSL drop from as much 50 m asl to as low as -6.3 m asl in as little as a few centuries between 14,500 BP and 13,500 BP. After a lowstand below current sea level for about 2000 years during the terminal Pleistocene, RSL rose again to a highstand at least 6 m asl after the end of the Younger Dryas. RSL slowly dropped through the Holocene to close to its current position by 2000-1500 BP, with some potential fluctuations between 3500 and 1500 BP. This study highlights variation in RSL histories across relatively short distances, which must be accounted for by local RSL reconstructions such as this one. This RSL curve aided in the identification of an 8000-9000 year old archaeological site on a 10-12 m asl terrace, which is currently the earliest dated archaeological site in the area, and it provides guidance for searching for even older archaeological remains. We highlight the utility and potential of this refined RSL history for developing surveys for other archaeological sites associated with paleoshorelines.

  15. Sea-level variability over five glacial cycles.

    Science.gov (United States)

    Grant, K M; Rohling, E J; Ramsey, C Bronk; Cheng, H; Edwards, R L; Florindo, F; Heslop, D; Marra, F; Roberts, A P; Tamisiea, M E; Williams, F

    2014-09-25

    Research on global ice-volume changes during Pleistocene glacial cycles is hindered by a lack of detailed sea-level records for time intervals older than the last interglacial. Here we present the first robustly dated, continuous and highly resolved records of Red Sea sea level and rates of sea-level change over the last 500,000 years, based on tight synchronization to an Asian monsoon record. We observe maximum 'natural' (pre-anthropogenic forcing) sea-level rise rates below 2 m per century following periods with up to twice present-day ice volumes, and substantially higher rise rates for greater ice volumes. We also find that maximum sea-level rise rates were attained within 2 kyr of the onset of deglaciations, for 85% of such events. Finally, multivariate regressions of orbital parameters, sea-level and monsoon records suggest that major meltwater pulses account for millennial-scale variability and insolation-lagged responses in Asian monsoon records.

  16. PALEOENVIRONMENTAL RECONSTRUCTION FROM BENTHIC FORAMINIFERAL ASSEMBLAGES OF EARLY HOLOCENE, SHALLOW MARINE DEPOSITS IN GOMBONG, CENTRAL JAVA

    Directory of Open Access Journals (Sweden)

    Luli Gustiani

    2017-07-01

    Full Text Available A 30m-long sediment core covering the Holocene period was taken from the area of Gombong in the southern part of Central Java. The sediments were deposited in a shallow marine to lagoonal environment that was confirmed by the dominance of Ammonia beccarii along the core intervals. In addition, the species Quinqueloculina poeyana, Miliolinella lakemacquariensis, and Miliolinella subrotunda were also found in the sediments that are typical of normal shallow marine conditions. The decrease and increase in the abundance of these species throughout the core is an expression of sea level change in the area, which results the environmental changes. Low sea level is expressed by the dominance of Ammonia beccarii, and the low abundances or absence of the other three species. In contrast, high sea level stands are reflected by the presence of all four species. The high sea level would imply favorable conditions for benthic foraminifera because it would result in normal shallow marine conditions in the area. Finally, from this benthic assemblages study, it can be assumed that the environmental transformation from the originally shallow marine environment into land was occurred at level 5.5m depths of the sediment core, when all benthic foraminifera were terminated, including Ammonia beccarii. These new results from the shallow marine deposits in the Gombong area are a new contribution to the understanding of paleoenvironmental change in the region, which in turn is important for understanding sea level change as well as climate change in the region.

  17. Radiation dates of holocene shorelines in Peninsula Malaysia

    International Nuclear Information System (INIS)

    Tjia, H.D.; Kigoshi, K.

    1977-01-01

    Fifteen newly determined radiocarbon dates indicate the presence of former shorelines up to 3 meters above present high tide level in the tectonically stable Peninsula of Malaysia. The sea level indicators consist of oysters in growth position (9 samples), molluscs in beach deposits (2), corals in growth position (3), and beachrock (1). In the Peninsula living oysters occur up to or slightly above high tide, modern beach deposits may occur as high as 1.5 meters above high tide, and corals live up to low tide level. The literature shows that high tide, and corals live up to low tide level. The literature shows that beachrock marks intertidal zones. Combined with seven previously published ages of raised shorelines in the region, strong evidence is presented for one or more high Holocene, eustatic sea level stands in the continental part of Southeast Asia. Periods of high sea levels occur between 2500 and 2900 yr BP, and between 4200 and 5700 yr BP. There is also some indication of high sea level between 8300 and 9500 yr BP. (author)

  18. Holocene lake-level fluctuations of Lake Aricota, Southern Peru

    Science.gov (United States)

    Placzek, C.; Quade, Jay; Betancourt, J.L.

    2001-01-01

    Lacustrine deposits exposed around Lake Aricota, Peru (17?? 22???S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (Titicaca (16?? S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes. ?? 2001 University of Washington.

  19. Cyclicity in the Late Holocene monsoonal changes from the western Bay of Bengal: Foraminiferal approach.

    Digital Repository Service at National Institute of Oceanography (India)

    Rana, S.S.; Nigam, R.

    .; Imbrie, J.; Hays, J.; Kukla, G.; Saltzman, B.. NATO ASI Ser. C: Math. Phys. Sci.; 126: 349-366. Sarkar, A., Ramesh, R., Somayajulu, B.L.K., Agnihotri, R., Jull, A.J.T., Burr, G.S. 2000. High resolution Holocene monsoon record from the eastern Arabian Sea...

  20. Flooded! An Investigation of Sea-Level Rise in a Changing Climate

    Science.gov (United States)

    Gillette, Brandon; Hamilton, Cheri

    2011-01-01

    Explore how melting ice sheets affect global sea levels. Sea-level rise (SLR) is a rise in the water level of the Earth's oceans. There are two major kinds of ice in the polar regions: sea ice and land ice. Land ice contributes to SLR and sea ice does not. This article explores the characteristics of sea ice and land ice and provides some hands-on…

  1. Environmental changes of the last 30,000 years in the gas hydrate area of Joetsu Basin, eastern margin of Japan Sea

    Energy Technology Data Exchange (ETDEWEB)

    Freire, A.F.M.; Sugai, T. [Tokyo Univ., Kashiwanoha Campus, Chiba (Japan). Dept. of Natural Environmental Studies; Takeuchi, E.; Nagasaka, A.; Hiruta, A.; Ishizaki, O.; Matsumoto, R. [Tokyo Univ., Hongo Campus, Bunkyo-ku, Tokyo (Japan). Dept. of Earth and Planetary Science

    2008-07-01

    The Japan Sea is a semi-isolated marginal sea with an average depth of 1350 metres and a maximum water depth of approximately 3700 metres in the northern basin. This paper presented a study that inferred the age and the nature of the environmental events of the last 30 thousand years using geochemical and sedimentary records from piston cores collected on the gas hydrates bearing-sediments of Joetsu Basin, eastern margin of Japan Sea, south of Sado Islands. Interbedded dark gray thinly laminates and dark brown to gray bioturbated units are common throughout the quaternary sediments of the Japan Sea. They have been explained in terms of glacio-eustatic sea-level change. Active methane venting and gas hydrates have also been recognized, which are widely distributed just beneath the sea floor in the Joetsu Basin, in the eastern margin of the Japan Sea. In order to identify the nature of the organic matter present in the study area and to make a correlation with samples collected in the Pacific Ocean, the study utilized total organic carbon contents and carbon isotopic composition of the gas hydrates bearing-sediments. Using X-ray diffraction analysis, these data were used to apply sequence stratigraphy concepts to locate the holocene/pleistocene boundary and to identify key stratigraphic surfaces, and also to recognize methane flux variations and sulfate-methane interfaces. The paper discussed total organic carbon in the Holocene/Pleistocene boundaries; nature of the organic matter and terrestrial versus marine phytoplankton production; and terrigenous material input. Sulfate oxidation of methane was also discussed. It was concluded that the correlation between the Japan Sea and Pacific Ocean was possible using piston cores. 13 refs., 13 figs.

  2. Sediment biomarkers elucidate the Holocene ontogeny of a shallow lake.

    Directory of Open Access Journals (Sweden)

    T E Arnold

    Full Text Available We carried out geochemical analyses on a sediment core from Lake Harris, Florida (USA to identify sources of organic matter to the sediment throughout the Holocene, and relate changes in those sources to shifts in past climate and environmental conditions. We hypothesized that the sources of organic matter changed in response to regional hydrologic shifts following de-glaciation, and to human population expansion in the state during the 20th century. Hydroclimate shifts in Florida were related to: 1 a steady rise in relative sea level and the fresh water table that began in the early Holocene, 2 wetland formation and expansion ca. 5,000 cal yrs BP, and 3 the onset of the modern El Niño (ENSO cycle ~3,000 cal yrs BP. Stratigraphic changes in sediment variables from Lake Harris reflect each of these hydroclimate periods. Early in the Holocene, Lake Harris was a marsh-like system in a relatively dry, open-prairie environment. Organic sediments deposited at that time were derived largely from terrestrial sources, as inferred from high TOC/TN ratios, a dominance of longer-chain of n-alkanes (n-C29-31, relatively negative organic carbon isotope values (δ13CTOC, and low biogenic silica concentrations. In the middle Holocene, a positive shift in δ13CTOC coincided with the onset of wetter conditions in Florida. Submerged macrophyte biomarkers (n-C21-23 dominated, and during that period bulk organic carbon isotope values were most similar to δ13C values of mid-chain-length n-alkanes. In the late Holocene, δ13CTOC values declined, CaCO3 levels decreased to trace amounts, organic carbon concentrations increased and diatom biogenic silica concentrations increased from 10 to 120 mg g-1. Around 2,900 cal yrs BP, the effects of ENSO intensified and many Florida lakes deepened to their current limnetic state. Concentrations of algal and cyanobacterial biomarkers in the Lake Harris core increased by orders of magnitude after about AD 1940, in response to

  3. Greenland uplift and regional sea level changes from ICESat observations and GIA modelling

    DEFF Research Database (Denmark)

    Spada, G.; Ruggieri, G.; Sørensen, Louise Sandberg

    2012-01-01

    ‐resolution GrIS mass balance, we study the time‐variations of various geophysical quantities in response to the current mass loss. They include vertical uplift and subsidence, geoid height variations, global patterns of sea level change (or fingerprints), and regional sea level variations along the coasts...... of Greenland. Long‐wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation, which accounts for both the elastic and the viscoelastic components of deformation. To capture the short‐wavelength components of vertical uplift...... in response to current ice mass loss, which is not resolved by satellite gravity observations, we have specifically developed a high‐resolution regional elastic rebound (ER) model. The elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated...

  4. Sea level rise in the Arctic Ocean

    OpenAIRE

    Proshutinsky, Andrey; Pavlov, Vladimir; Bourke, Robert H.

    2001-01-01

    The article of record as published may be found at http://dx.doi.org/10.1029/2000GL012760 About 60 tide-gauge stations in the Kara, Laptev, East-Siberian and Chukchi Seas have recorded the sea level change from the 1950s through 1990s. Over this 40-year period, most of these stations show a significant sea level rise (SLR). In light of global change, this SLR could be a manifestation of warming in the Artic coupled with a decrease of sea ice extent, warming of Atlantic waters, changes in...

  5. Sea level and turbidity controls on mangrove soil surface elevation change

    Science.gov (United States)

    Lovelock, Catherine E.; Fernanda Adame, Maria; Bennion, Vicki; Hayes, Matthew; Reef, Ruth; Santini, Nadia; Cahoon, Donald R.

    2015-01-01

    Increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees; however, tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise. Sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level, enabling intertidal habitats to maintain their position relative to mean sea level, but there are few tests of these predictions in mangrove forests. Here we used variation in sea level and the availability of sediments caused by seasonal and inter-annual variation in the intensity of La Nina-El Nino to assess the effects of increasing sea level on surface elevation gains and contributing processes (accretion on the surface, subsidence and root growth) in mangrove forests. We found that soil surface elevation increased with mean sea level (which varied over 250 mm during the study) and with turbidity at sites where fine sediment in the water column is abundant. In contrast, where sediments were sandy, rates of surface elevation gain were high, but not significantly related to variation in turbidity, and were likely to be influenced by other factors that deliver sand to the mangrove forest. Root growth was not linked to soil surface elevation gains, although it was associated with reduced shallow subsidence, and therefore may contribute to the capacity of mangroves to keep pace with sea level rise. Our results indicate both surface (sedimentation) and subsurface (root growth) processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location, and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine, but not coarse, sediments are abundant.

  6. Sea level changes along the Indian coast: Observations and projections

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Kumar, K.R.; Fernandes, S.E.; Michael, G.S.; Patwardhan, S.K.

    : CLIMATE CHANGE AND INDIA CURRE NT SCIENCE, VOL. 90, NO. 3, 10 FEBRUARY 2006 *For correspondence. (e - mail: unni@darya.nio.org ) Sea level changes along the Indian coast: Observ a tions and projections A. S. Unnikrishnan 1, *, K. Rupa Kumar... with the occu r rence of tropical cyclones in the Bay of Bengal and associated storm surges in a future climate scenario. Projections for the future are needed for decision making by planners and policy makers. Future pr o jecti ons are made for different...

  7. Rapid response of a marine mammal species to holocene climate and habitat change.

    Directory of Open Access Journals (Sweden)

    Mark de Bruyn

    2009-07-01

    Full Text Available Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ. This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500-8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population approximately 8,000 YBP, followed by directional migration away from VLC and the loss of diversity at approximately 1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, approximately 7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available.

  8. Rapid response of a marine mammal species to holocene climate and habitat change.

    Science.gov (United States)

    de Bruyn, Mark; Hall, Brenda L; Chauke, Lucas F; Baroni, Carlo; Koch, Paul L; Hoelzel, A Rus

    2009-07-01

    Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC) in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ). This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500-8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population approximately 8,000 YBP, followed by directional migration away from VLC and the loss of diversity at approximately 1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, approximately 7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available.

  9. Sea-Level Allowances along the World Coastlines

    Science.gov (United States)

    Vandewal, R.; Tsitsikas, C.; Reerink, T.; Slangen, A.; de Winter, R.; Muis, S.; Hunter, J. R.

    2017-12-01

    Sea level changes as a result of climate change. For projections we take ocean mass changes and volume changes into account. Including gravitational and rotational fingerprints this provide regional sea level changes. Hence we can calculate sea-level rise patterns based on CMIP5 projections. In order to take the variability around the mean state, which follows from the climate models, into account we use the concept of allowances. The allowance indicates the height a coastal structure needs to be increased to maintain the likelihood of sea-level extremes. Here we use a global reanalysis of storm surges and extreme sea levels based on a global hydrodynamic model in order to calculate allowances. It is shown that the model compares in most regions favourably with tide gauge records from the GESLA data set. Combining the CMIP5 projections and the global hydrodynamical model we calculate sea-level allowances along the global coastlines and expand the number of points with a factor 50 relative to tide gauge based results. Results show that allowances increase gradually along continental margins with largest values near the equator. In general values are lower at midlatitudes both in Northern and Southern Hemisphere. Increased risk for extremes are typically 103-104 for the majority of the coastline under the RCP8.5 scenario at the end of the century. Finally we will show preliminary results of the effect of changing wave heights based on the coordinated ocean wave project.

  10. Continuous record of Holocene sea-level changes and coastal development of the Kattegat island Laeso (4900 years BP to present)

    DEFF Research Database (Denmark)

    Hansen, Jens Morten; Aagaard, Troels; Stockmarr, Jens

    2016-01-01

    in order to transform the ridge elevations to a detailed curve of the RSL/age relation. The curve reveals eight centennial sea-level oscillations of 0.5–1.1 m superimposed on the general trend of the RSL curve, including a Little Ice Age lowstand of 0.6 m at 1300 AD. The island grew from now eroded...

  11. Assessing the impact of sea level rise due to climate change on seawater intrusion in Mekong Delta, Vietnam.

    Science.gov (United States)

    Vu, D T; Yamada, T; Ishidaira, H

    2018-03-01

    In the context of climate change, salinity intrusion into rivers has been, and will be, one of the most important issues for coastal water resources management. A combination of changes, including increased temperature, change in regional rainfall, especially sea level rise (SLR) related to climate change, will have significant impacts on this phenomenon. This paper presents the outcomes of a study conducted in the Mekong Delta of Vietnam (MKD) for evaluating the effect of sea water intrusion under a new SLR scenario. Salinity intrusion was simulated by one-dimensional (1D) modeling. The relative sea level projection was constructed corresponding to the RCP 6.0 emission scenario for MKD based on the statistical downscaling method. The sea level in 2050 is projected to increase from 25 cm to 30 cm compared to the baseline period (in 2000). Furthermore, the simulated results suggested that salinity greater than 4 g/l, which affects rice yield, will intrude up to 50-60 km into the river. Approximately 30,000 ha of agricultural area will be affected if the sea level rise is 30 cm.

  12. Recently studied sedimentary records from the eastern Arabian Sea: Implications to Holocene monsoonal variability

    Digital Repository Service at National Institute of Oceanography (India)

    Agnihotri, R.; Kurian, S.

    stream_size 72460 stream_content_type text/plain stream_name Earth_Sci_India_1_258.pdf.txt stream_source_info Earth_Sci_India_1_258.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Agnihotri http://www....earthscienceindia.info/Agnihotri.htm 1 of 14 10/15/2008 9:41 AM Earth Science India Vol.1 (IV), October, 2008, pp. 258-287 http://www.earthscienceindia.info/ Recently studied sedimentary records from the eastern Arabian Sea: Implications to Holocene monsoonal variability Rajesh...

  13. Holocene environmental change in the Albertine Rift : sediment-based evidence from Virunga volcanoes

    OpenAIRE

    McGlynn, Gayle

    2012-01-01

    The Albertine Rift is one of the most important conservation areas in tropical Africa, with exceptionally high levels of biodiversity (including rare and endemic montane flora and fauna) and high human population densities. Environmental changes in the Albertine Rift during the Holocene have been influenced both by long-term climate change and by human activity, although establishing clear cause-effect relationships is often problematic - particularly as this area is known to have had a long ...

  14. Continuous sea-level reconstructions beyond the Pleistocene: improving the Mediterranean sea-level method

    Science.gov (United States)

    Grant, K.; Rohling, E. J.; Amies, J.

    2017-12-01

    Sea-level (SL) reconstructions over glacial-interglacial timeframes are critical for understanding the equilibrium response of ice sheets to sustained warming. In particular, continuous and high-resolution SL records are essential for accurately quantifying `natural' rates of SL rise. Global SL changes are well-constrained since the last glacial maximum ( 20,000 years ago, ky) by radiometrically-dated corals and paleoshoreline data, and fairly well-constrained over the last glacial cycle ( 150 ky). Prior to that, however, studies of ice-volume:SL relationships tend to rely on benthic δ18O, as geomorphological evidence is far more sparse and less reliably dated. An alternative SL reconstruction method (the `marginal basin' approach) was developed for the Red Sea over 500 ky, and recently attempted for the Mediterranean over 5 My (Rohling et al., 2014, Nature). This method exploits the strong sensitivity of seawater δ18O in these basins to SL changes in the relatively narrow and shallow straits which connect the basins with the open ocean. However, the initial Mediterranean SL method did not resolve sea-level highstands during Northern Hemisphere insolation maxima, when African monsoon run-off - strongly depleted in δ18O - reached the Mediterranean. Here, we present improvements to the `marginal basin' sea-level reconstruction method. These include a new `Med-Red SL stack', which combines new probabilistic Mediterranean and Red Sea sea-level stacks spanning the last 500 ky. We also show how a box model-data comparison of water-column δ18O changes over a monsoon interval allows us to quantify the monsoon versus SL δ18O imprint on Mediterranean foraminiferal carbonate δ18O records. This paves the way for a more accurate and fully continuous SL reconstruction extending back through the Pliocene.

  15. Arctic sea level change over the past 2 decades from GRACE gradiometry and multi-mission satellite altimetry

    DEFF Research Database (Denmark)

    Andersen, O. B.; Stenseng, L.; Sørensen, C. S.

    2014-01-01

    The Arctic is still an extremely challenging region for theuse of remote sensing for sea level studies. Despite the availability of 20 years of altimetry, only very limited sea level observations exist in the interior of the Arctic Ocean. However, with Cryosat-2 SAR altimetry the situation...... gradiometer observations from the ESA GOCE mission, we are now able to derive a mean dynamic topography of the Arctic Ocean with unprecedented accuracy to constrain the Arctic Ocean circulation controlling sea level variations in the Arctic. We present both a new estimation of the mean ocean circulation...... and new estimates of large scale sea level changes based on satellite data and perform an estimation of the fresh waterstorage increase over the last decade using temporal gravity changes from the GRACE satellite....

  16. Millennial-scale variability in Holocene aquatic productivity from Burial Lake, Arctic Alaska

    Science.gov (United States)

    Finkenbinder, Matthew S.; Abbott, Mark B.; Stoner, Joseph S.; Ortiz, Joseph D.; Finney, Bruce P.; Dorfman, Jason M.; Stansell, Nathan D.

    2018-05-01

    Ocean proxy records and numerous other marine and terrestrial paleorecords. Comparison of diatom productivity against a sea-ice inferred reconstruction of the Arctic Oscillation (AO) from the Beaufort Sea (Darby et al., 2012) shows that periods of reduced productivity at Burial Lake coincide with inferred positive phases of the AO (AO+). Combined with modern observations of sea ice extent and meteorological data, we hypothesize that AO + conditions and a strengthened polar jet correspond with a shortened ice-free growing season, a decrease in the availability of limiting nutrients, and lower levels of diatom production at Burial Lake. Comparison of the spectral properties between opal and the AO reconstruction reveal similar millennial scale variations with ∼1500-yr variability during the middle Holocene that transition to ∼1000-yr variability during the late Holocene. In light of these findings, we suggest the possibility that millennial variations in diatom productivity observed in the Burial Lake record are related to millennial variability in high-latitude atmospheric circulation similar to the AO. These results shed light on the sensitivity of aquatic ecosystems in northern Alaska to changes in the duration of the ice-free growing season, the availability of limiting nutrients for phytoplankton growth, and Arctic-wide atmospheric circulation dynamics over the Holocene on millennial timescales.

  17. A review on the Holocene evolution of an inner-shelf mud deposit in the southeastern Yellow Sea: the Huksan Mud Belt

    Science.gov (United States)

    Lee, Hee Jun

    2015-12-01

    The Huksan Mud Belt (HMB) has been extensively investigated with respect to its source and evolution since the 1980s. Studies on sediment budget or accumulation rates suggested two different origins, Korean and combined Korean and Chinese. However, neither of the suggested origins appears reliable because they were based on insufficient or inaccurate datasets on the basic sedimentological characteristics of the HMB. Although a major mud transport was inferred to be closely associated with either the Korean Coastal Current or the Yellow Sea Warm Current, their physical characters during the Holocene transgression have been rarely hind-casted thus far. The majority of studies on high-resolution seismic stratigraphy along with core log have suggested that the HMB stratigraphy consists of two units divided by an erosional boundary. The lower unit is further divided into two subunits by a subtle discontinuity that is laterally correlated with the erosional boundary. In line with the stratigraphy, the studies theorized that the erosion of the HMB had produced a re-deposited distal lobe, the younger lower subunit. In addition, this lobe was inferred to have prograded rapidly during the relatively short period of 6,500-5,500 yr B.P. Although the time interval of the erosion coincides with the decelerating rise in sea level, the hydrodynamic cause and effect of the erosion remain inexplicable. Therefore, the source and evolution of the HMB continue to be controversial, due largely to poor understanding of the paleo-physical oceanography of the Yellow Sea during the Holocene.

  18. Long-term and seasonal Caspian Sea level change from satellite gravity and altimeter measurements

    Science.gov (United States)

    Chen, J. L.; Wilson, C. R.; Tapley, B. D.; Save, H.; Cretaux, Jean-Francois

    2017-03-01

    We examine recent Caspian Sea level change by using both satellite radar altimetry and satellite gravity data. The altimetry record for 2002-2015 shows a declining level at a rate that is approximately 20 times greater than the rate of global sea level rise. Seasonal fluctuations are also much larger than in the world oceans. With a clearly defined geographic region and dominant signal magnitude, variations in the sea level and associated mass changes provide an excellent way to compare various approaches for processing satellite gravity data. An altimeter time series derived from several successive satellite missions is compared with mass measurements inferred from Gravity Recovery and Climate Experiment (GRACE) data in the form of both spherical harmonic (SH) and mass concentration (mascon) solutions. After correcting for spatial leakage in GRACE SH estimates by constrained forward modeling and accounting for steric and terrestrial water processes, GRACE and altimeter observations are in complete agreement at seasonal and longer time scales, including linear trends. This demonstrates that removal of spatial leakage error in GRACE SH estimates is both possible and critical to improving their accuracy and spatial resolution. Excellent agreement between GRACE and altimeter estimates also provides confirmation of steric Caspian Sea level change estimates. GRACE mascon estimates (both the Jet Propulsion Laboratory (JPL) coastline resolution improvement version 2 solution and the Center for Space Research (CSR) regularized) are also affected by leakage error. After leakage corrections, both JPL and CSR mascon solutions also agree well with altimeter observations. However, accurate quantification of leakage bias in GRACE mascon solutions is a more challenging problem.

  19. Ice sheet-ocean interactions and sea level change

    Science.gov (United States)

    Heimbach, Patrick

    2014-03-01

    Mass loss from the Greenland and Antarctic ice sheets has increased rapidly since the mid-1990s. Their combined loss now accounts for about one-third of global sea level rise. In Greenland, a growing body of evidence points to the marine margins of these glaciers as the region from which this dynamic response originated. Similarly, ice streams in West Antarctica that feed vast floating ice shelves have exhibited large decadal changes. We review observational evidence and present physical mechanisms that might explain the observed changes, in particular in the context of ice sheet-ocean interactions. Processes involve cover 7 orders of magnitudes of scales, ranging from mm boundary-layer processes to basin-scale coupled atmosphere-ocean variability. We discuss observational needs to fill the gap in our mechanistic understanding.

  20. Present day sea level changes: observations and climatic causes

    International Nuclear Information System (INIS)

    Lombard, A.

    2007-01-01

    After a few thousand years of relative stability, sea level has risen of about 20 cm since the beginning of the 20. century. It currently rises at an average rate of about 3 mm/yr in response to global warming. About half of this rate is directly attributed to thermal expansion of sea water due to ocean warming, while the other half is mainly due to the melting of mountain glaciers and ice sheets. Satellite observations show that sea level rise is highly non-uniform. (author)

  1. Late quaternary sea level changes of Gabes coastal plain and shelf ...

    Indian Academy of Sciences (India)

    site to study coastal changes at time scale, rang- ing from ... regional shoreline during MIS 5c (100 ka) and MIS .... Remote sensing drainage network anal- ... Around Gabes city, the Pleistocene deposits are ... tems are well developed and fluvial discharges are ..... relative sea-level rise: A case study from trab el makhadha.

  2. Calcite raft geochemistry as a hydrological proxy for Holocene aquifer conditions in Hoyo Negro and Ich Balam (Sac Actun Cave System), Quintana Roo, Mexico

    Science.gov (United States)

    Kovacs, Shawn E.; Reinhardt, Eduard G.; Chatters, James C.; Rissolo, Dominique; Schwarcz, Henry P.; Collins, Shawn V.; Kim, Sang-Tae; Nava Blank, Alberto; Luna Erreguerena, Pilar

    2017-11-01

    Two cores from calcite rafts deposits located in Cenote Ich Balam and Hoyo Negro were dated and analyzed for 87Sr/86Sr, δ18O, δ13C, Sr/Ca and Cl/Ca. The geochemical records show changing aquifer salinity spanning the last ∼ 8.5 cal kyrs BP and interrelationships with Holocene climate trends (wet and dry periods). During the wet mid-Holocene, the salinity of the meteoric Water Mass (WM; at 7.8-8.3 cal kyrs BP) was relatively high at 1.5-2.7 ppt and then became less saline (1.0-1.5 ppt) during the last ∼ 7000 yrs as climate became progressively drier. High salinity of the meteoric WM during the wet mid-Holocene is attributed to increased turbulent mixing between the meteoric and underlying marine WM. Increased precipitation, in terms of amount, frequency, and intensity (e.g. hurricanes) causes higher flow of meteoric water towards the coast and mixing at the halocline, a phenomenon recorded with recent instrumental monitoring of the aquifer. Conversely, during dry periods reduced precipitation and flow in the meteoric WM would result in lower salinity. Karst properties and Holocene sea-level rise also seem to have an effect on the aquifer. When the regionally extensive network of shallow cave passages (∼ 10-12 m water depth) are flooded at ∼ 8000 cal yrs BP, there is a rapid shift in salinity. This study demonstrates that calcite raft deposits can be used as paleo-environmental recorders documenting the effects of sea level and climate change on aquifer condition.

  3. Late Holocene evolution of the Northeast intertidal region of Sepetiba Bay, Rio de Janeiro (Brazil)

    OpenAIRE

    Anita Fernandes Souza Pinto; Maria Virgínia Alves Martins; Maria Antonieta da Conceição Rodrigues; Leandro Nogueira; Lazaro Luiz Mattos Laut; Egberto Pereira

    2016-01-01

    This work is based on the study of the core T1 collected in the Guaratiba Mangrove, located on the northeastern margin of Sepetiba Bay. Few studies dealing with the application of benthic foraminifera to study sea level changes during the Holocene have been conducted in Sepetiba Bay, State of Rio de Janeiro, Brazil. In order to fill this gap, the core T1 was studied using textural, geochemical (carbonate, total organic carbon, total sulfur and stable isotopes evaluated in Ammonia tepida) and ...

  4. Extremely low genetic diversity across mangrove taxa reflects past sea level changes and hints at poor future responses.

    Science.gov (United States)

    Guo, Zixiao; Li, Xinnian; He, Ziwen; Yang, Yuchen; Wang, Wenqing; Zhong, Cairong; Greenberg, Anthony J; Wu, Chung-I; Duke, Norman C; Shi, Suhua

    2018-04-01

    The projected increases in sea levels are expected to affect coastal ecosystems. Tropical communities, anchored by mangrove trees and having experienced frequent past sea level changes, appear to be vibrant at present. However, any optimism about the resilience of these ecosystems is premature because the impact of past climate events may not be reflected in the current abundance. To assess the impact of historical sea level changes, we conducted an extensive genetic diversity survey on the Indo-Malayan coast, a hotspot with a large global mangrove distribution. A survey of 26 populations in six species reveals extremely low genome-wide nucleotide diversity and hence very small effective population sizes (N e ) in all populations. Whole-genome sequencing of three mangrove species further shows the decline in N e to be strongly associated with the speed of past changes in sea level. We also used a recent series of flooding events in Yalong Bay, southern China, to test the robustness of mangroves to sea level changes in relation to their genetic diversity. The events resulted in the death of half of the mangrove trees in this area. Significantly, less genetically diverse mangrove species suffered much greater destruction. The dieback was accompanied by a drastic reduction in local invertebrate biodiversity. We thus predict that tropical coastal communities will be seriously endangered as the global sea level rises. Well-planned coastal development near mangrove forests will be essential to avert this crisis. © 2017 John Wiley & Sons Ltd.

  5. Hypoxia and cyanobacteria blooms - are they really natural features of the late Holocene history of the Baltic Sea?

    Directory of Open Access Journals (Sweden)

    L. Zillén

    2010-08-01

    Full Text Available During the last century (1900s industrialized forms of agriculture and human activities have caused eutrophication of Baltic Sea waters. As a consequence, the hypoxic zone in the Baltic Sea has increased, especially during the last 50 years, and has caused severe ecosystem disturbance. Climate forcing has been proposed to be responsible for the reported trends in hypoxia (< 2 mg/l O2 both during the last c. 100 years (since c. 1900 AD and the Medieval Period. By contrast, investigations of the degree of anthropogenic forcing on the ecosystem on long time-scales (millennial and greater have not been thoroughly addressed. This paper examines evidence for anthropogenic disturbance of the marine environment beyond the last century through the analysis of the human population growth, technological development and land-use changes in the drainage area. Natural environmental changes, i.e. changes in the morphology and depths of the Baltic basin and the sills, were probably the main driver for large-scale hypoxia during the early Holocene (8000–4000 cal yr BP. We show that hypoxia during the last two millennia has followed the general expansion and contraction trends in Europe and that human perturbation has been an important driver for hypoxia during that time. Hypoxia occurring during the Medieval Period coincides with a doubling of the population (from c. 4.6 to 9.5 million in the Baltic Sea watershed, a massive reclamation of land in both established and marginal cultivated areas and significant increases in soil nutrient release. The role of climate forcing on hypoxia in the Baltic Sea has yet to be demonstrated convincingly, although it could have helped to sustain hypoxia through enhanced salt water inflows or through changes in hydrological inputs. In addition, cyanobacteria blooms are not natural features of the Baltic Sea as previously deduced, but are a consequence of enhanced phosphorus release from the seabed that occurs during

  6. Late Quaternary sea-level history and the antiquity of mammoths (Mammuthus exilis and Mammuthus columbi), Channel Islands NationalPark, California, USA

    Science.gov (United States)

    Muhs, Daniel R.; Simmons, Kathleen R.; Groves, Lindsey T.; McGeehin, John P.; Schumann, R. Randall; Agenbroad, Larry D.

    2015-01-01

    Fossils of Columbian mammoths (Mammuthus columbi) and pygmy mammoths (Mammuthus exilis) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace with MIS 5.1, a time of relatively high sea level. Mammoths likely immigrated to the islands by swimming during the glacial periods MIS 6 (~ 150 ka) or MIS 8 (~ 250 ka), when sea level was low and the island–mainland distance was minimal, as during MIS 2. Earliest mammoth immigration to the islands likely occurred late enough in the Quaternary that uplift of the islands and the mainland decreased the swimming distance to a range that could be accomplished by mammoths. Results challenge the hypothesis that climate change, vegetation change, and decreased land area from sea-level rise were the causes of mammoth extinction at the Pleistocene/Holocene boundary on the Channel Islands. Pre-MIS 2 mammoth populations would have experienced similar or even more dramatic changes at the MIS 6/5.5 transition.

  7. Sea level trends in South East Asian Seas (SEAS)

    Science.gov (United States)

    Strassburg, M. W.; Hamlington, B. D.; Leben, R. R.; Manurung, P.; Lumban Gaol, J.; Nababan, B.; Vignudelli, S.; Kim, K.-Y.

    2014-10-01

    Southeast Asian Seas (SEAS) span the largest archipelago in the global ocean and provide a complex oceanic pathway connecting the Pacific and Indian Oceans. The SEAS regional sea level trends are some of the highest observed in the modern satellite altimeter record that now spans almost two decades. Initial comparisons of global sea level reconstructions find that 17 year sea level trends over the past 60 years exhibit good agreement in areas and at times of strong signal to noise associated decadal variability forced by low frequency variations in Pacific trade winds. The SEAS region exhibits sea level trends that vary dramatically over the studied time period. This historical variation suggests that the strong regional sea level trends observed during the modern satellite altimeter record will abate as trade winds fluctuate on decadal and longer time scales. Furthermore, after removing the contribution of the Pacific Decadal Oscillation (PDO) to sea level trends in the past twenty years, the rate of sea level rise is greatly reduced in the SEAS region. As a result of the influence of the PDO, the SEAS regional sea level trends during 2010s and 2020s are likely to be less than the global mean sea level (GMSL) trend if the observed oscillations in wind forcing and sea level persist. Nevertheless, long-term sea level trends in the SEAS will continue to be affected by GMSL rise occurring now and in the future.

  8. Late Quaternary Variability of Arctic Sea Ice: Insights From Biomarker Proxy Records and Model Simulations

    Science.gov (United States)

    Stein, R. H.; Fahl, K.; Gierz, P.; Niessen, F.; Lohmann, G.

    2017-12-01

    Over the last about four decades, coinciding with global warming and atmospheric CO2increase, the extent and thickness of Arctic sea ice has decreased dramatically, a decrease much more rapid than predicted by climate models. The driving forces of this change are still not fully understood. In this context, detailed paleoclimatic records going back beyond the timescale of direct observations, i.e., high-resolution Holocene records but also records representing more distant warm periods, may help to to distinguish and quantify more precisely the natural and anthropogenic greenhouse gas forcing of global climate change and related sea ice decrease. Here, we concentrate on sea ice biomarker records representing the penultimate glacial/last interglacial (MIS 6/MIS 5e) and the Holocene time intervals. Our proxy records are compared with climate model simulations using a coupled atmosphere-ocean general circulation model (AOGCM). Based on our data, polynya-type sea ice conditions probably occurred off the major ice sheets along the northern Barents and East Siberian continental margins during late MIS 6. Furthermore, we demonstrate that even during MIS 5e, i.e., a time interval when the high latitudes have been significantly warmer than today, sea ice existed in the central Arctic Ocean during summer, whereas sea ice was significantly reduced along the Barents Sea continental margin influenced by Atlantic Water inflow. Assuming a closed Bering Strait (no Pacific Water inflow) during early MIS 5, model simulations point to a significantly reduced sea ice cover in the central Arctic Ocean, a scenario that is however not supported by the proxy record and thus seems to be less realistic. Our Holocene biomarker proxy records from the Chukchi Sea indicate that main factors controlling the millennial Holocene variability in sea ice are probably changes in surface water and heat flow from the Pacific into the Arctic Ocean as well as the long-term decrease in summer insolation

  9. Sedimentary architecture of the Holocene mud deposit off the southern Shandong Peninsula in the Yellow Sea

    Science.gov (United States)

    Qiu, Jiandong; Liu, Jian; Xu, Hong; Zhou, Liangyong

    2018-01-01

    Newly acquired high-resolution seismic profiles reveal a nearshore and an offshore mud depocenter offthe southern Shandong Peninsula in the Yellow Sea. The nearshore depocenter is distributed in bands along the south coast of Shandong Peninsula. The offshore depocenter is part of the distal subaqueous deltaic lobe, which deposited around the southeastern tip of the Shandong Peninsula. Between the two depocenters is a linear depression. The mud deposits directly overlie the postglacial transgressive surface and can be divided into lower and upper units by the Holocene maximum flooding surface. The nearshore and offshore units display different seismic structures. The lower unit of the nearshore deposit exhibits basal onlap, whereas the upper unit is characterized by progradation. The lower and upper units of the offshore deposit display distinct acoustic features. The lower unit has low-angle aggradation with internal reflectors generally dipping seaward and truncated by the Holocene maximum flooding surface, whereas the upper unit is characterized by aggradation and progradation landward rather than seaward. Results of geochemistry analysis of QDZ03 sediments and mineral analysis of WHZK01 sediments suggest that the nearshore deposit and the lower unit of the offshore deposit are derived from the proximal coastal sediments of the Shandong Peninsula and the Huanghe (Yellow) River sediments. The upper unit of the offshore deposit is mainly Huanghe River-derived. The lower unit of the mud deposit represents a post-glacial transgressive system tract according to dates of core QDZ03, and the upper unit represents a highstand system tract from middle Holocene to the present. These results will be of great significance to further understanding of the transportation of the Huanghe River sediments into the Yellow Sea and the spatial distribution of the subaqueous delta.

  10. (Pre-) calibration of a Reduced Complexity Model of the Antarctic Contribution to Sea-level Changes

    Science.gov (United States)

    Ruckert, K. L.; Guan, Y.; Shaffer, G.; Forest, C. E.; Keller, K.

    2015-12-01

    (Pre-) calibration of a Reduced Complexity Model of the Antarctic Contribution to Sea-level ChangesKelsey L. Ruckert1*, Yawen Guan2, Chris E. Forest1,3,7, Gary Shaffer 4,5,6, and Klaus Keller1,7,81 Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania, USA 2 Department of Statistics, The Pennsylvania State University, University Park, Pennsylvania, USA 3 Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania, USA 4 GAIA_Antarctica, University of Magallanes, Punta Arenas, Chile 5 Center for Advanced Studies in Arid Zones, La Serena, Chile 6 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark 7 Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, USA 8 Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA * Corresponding author. E-mail klr324@psu.eduUnderstanding and projecting future sea-level changes poses nontrivial challenges. Sea-level changes are driven primarily by changes in the density of seawater as well as changes in the size of glaciers and ice sheets. Previous studies have demonstrated that a key source of uncertainties surrounding sea-level projections is the response of the Antarctic ice sheet to warming temperatures. Here we calibrate a previously published and relatively simple model of the Antarctic ice sheet over a hindcast period from the last interglacial period to the present. We apply and compare a range of (pre-) calibration methods, including a Bayesian approach that accounts for heteroskedasticity. We compare the model hindcasts and projections for different levels of model complexity and calibration methods. We compare the projections with the upper bounds from previous studies and find our projections have a narrower range in 2100. Furthermore we discuss the implications for the design of climate risk management strategies.

  11. Relative sea-level change in the central Cyclades (Greece) since the Early Bronze Age

    Science.gov (United States)

    Draganits, E.

    2012-04-01

    The Aegean is a focus of important cultural achievements in Europe since the Neolithic period. The resulting abundance of archaeological remains, many of them below sea-level represent an advantageous area for the study of local relative sea-level change. We have carried out detailed mapping of Despotiko Island (SW of Antiparos) and its surrounding. Despotiko is situated almost exactly in the center of the Cyclades (as defined nowadays), more so than Delos, and therefore is very well suited for sea-level studies of the Cyclades. This beneficial location, combined with a spacious and protected bay, additionally may explain its former importance as stepping-stone in the Aegean Sea. The island is uninhabited at present, but Early Bronze Age settlement sites and graveyards as well as a large Archaic sanctuary proof its former importance. The sanctuary is situated on a gently northeast dipping slope in the northeast part of Despotiko, in range of sight of the Órmos Despotiko. Since 1997 large parts of this important sanctuary have been excavated during several excavation campaigns. Tectonically, Despotiko, Antiparos and Paros, belong to the Attic-Cycladic Crystalline of the Central Hellenides, a stack of metamorphic tectonic nappes, mainly comprising variable types of gneiss, schist, marble and amphibolite, and tectonic slices of unmetamorphosed sediments on top, separated by low-angle normal faults from the metamorphic units below. Submerged archaeological structures at the sea bottom of the Órmos Despotiko, a Classical marble inscription from the sanctuary and partly submerged agriculture trenches at the east coast Despotiko, indicate that the relative sea-level in this area was some 3 m lower during the Early Bronze Age and still more than 1 m lower during Classical time. These values of relative sea-level rise indicate a subsidence component additional to the global sea-level rise in the investigated time period. Neglecting possible vertical tectonic movements and

  12. Holocene sedimentary processes in the Gemlik Gulf: a transtensional basin on the middle Strand of the North Anatolian Fault, Sea of Marmara

    Science.gov (United States)

    Özmaral, A.; Çagatay, M. N.; Imren, C.; Gasperini, L.; Henry, P.

    2012-04-01

    Gemlik Gulf is an oval-shaped transtensional basin with a maximum depth of 113 m, located on the middle strand of the North Anatolian Fault (NAF) in the eastern part of the Sea of Marmara (SOM). During the last glacial period until the Holocene marine transgression about 12 ka BP, the sea level was below the Çanakkale (Dardanelles) Strait's bedrock sill depth of -85 m, and the Gemlik Basin became a lake isolated lake from the rest of the Sea of Marmara "Lake" and the global ocean. The high resolution seismic profiles and the multi- beam bathymetric map of the basin show that the basin is characterized by NW-SE trending transtensional oblique faults, delta lobes of the Büyükdere (Kocadere) to the east and an erosional surface below an up to 15 m-thick Holocene mud drape. The Holocene mud drape was studied in up to 9.5 m-long gravity-piston and 0.84 m-long sediment/water interface cores located at -105 to -113 m in the basin's depocentre. The Holocene mud consists mainly of plastic gray green marine clayey mud that includes thick-red brown clay layers and a laminated organic-rich, dark olive green sapropel in the lower part, which was previously dated at 11.6-6.4 14Ckyr (uncalib) BP. Multi-proxy analyses of the Holocene mud drape in the sediment cores were carried out using Multisensor Core Logger, XRF Core Scanner equipped with digital X-Ray radiography, and laser particle size analyzer. Seismic-core correlation was made using seismic data of the chirp profiles at the core locations and the synthetic seismograms generated using the MSCL P-wave velocity and gamma density measurements. The long piston-gravity cores include five 20 to 100 mm-thick "red brown mud layers" in the top 2.5 m of the core. These layers have a sharp basal boundary and gradational upper boundary. The red brown layers consist of 55-75% clay-size material with an average grain size of 3-4 µm, and have relatively a high magnetic susceptibility. They are enriched in K, Fe, Ti and Zr that are

  13. Remote sensing data analysis for assessment of sea level change in Asia; Asia ni okeru kaisuijun hendo eikyo hyoka no tame no remote sensing gazo kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, Y; Tanaka, A [Geological Survey of Japan, Tsukuba (Japan); Kaku, M [Bishimetal Exploration Co. Ltd., Tokyo (Japan)

    1997-10-22

    Remote sensing images include information of coastal land division, sea level change such as sedimentary environment and vegetation, and distribution of artificial structures. Past sea level changes and their causes can be regionally obtained by analyzing these data and by integrating them with information obtained from geological survey. In this study, causes and history of past sea level changes, formation mechanism of coastal topography, and past sea level change survey in Thailand have been reviewed. This paper describes an extraction method of the sea level change information in coastal districts by analyzing several actual remote sensing images. For understanding the current sea level rise, it is required to clarify the causes quantitatively among three causes of sea level changes, i.e., volumetric change of total ocean water on the earth, relative sea level change due to the crustal deformation, and change of irregularity of sea surface with ocean current. It is also required to compile maps in Asian or global scales. 13 refs., 6 figs.

  14. Low post-glacial rebound rates in the Weddell Sea due to Late Holocene ice-sheet readvance.

    OpenAIRE

    Bradley, S.L.; Hindmarsh, R.C.A.; Whitehouse, P.L.; Bentley, M.J.; King, M.A.

    2015-01-01

    Many ice-sheet reconstructions assume monotonic Holocene retreat for the West Antarctic Ice Sheet, but an increasing number of glaciological observations infer that some portions of the ice sheet may be readvancing, following retreat behind the present-day margin. A readvance in the Weddell Sea region can reconcile two outstanding problems: (i) the present-day widespread occurrence of seemingly stable ice streams grounded on beds that deepen inland; and (ii) the inability of models of glacial...

  15. Aquatic ecosystem responses to Holocene climate change and biome development in boreal, central Asia

    Science.gov (United States)

    Mackay, Anson W.; Bezrukova, Elena V.; Leng, Melanie J.; Meaney, Miriam; Nunes, Ana; Piotrowska, Natalia; Self, Angela; Shchetnikov, Alexander; Shilland, Ewan; Tarasov, Pavel; Wang, Luo; White, Dustin

    2012-05-01

    were also significant, but considerably less important. The potential importance of climate and biome development (tundra, steppe, cold deciduous forest and taiga) on different trophic levels (i.e. chironomid and diatom communities) in lake ESM-1 was also assessed using RDA. Climate predictors had a more significant influence on Holocene chironomid assemblages, especially July insolation at 60 °N, estimates of regional precipitation and estimates of northern hemisphere temperature, while only the development of the taiga biome had a significant impact on these primary consumers. Diatom communities also had a small, but significant influence on Holocene chironomid populations, perhaps linked to variation in faunal feeding strategies. In contrast, climatic and biome predictors explained similar amounts of variation in the Holocene diatom assemblage (approximately 20% each), while chironomids themselves as predictors explained just under 7% of diatom variation. Lake acidity was inferred using a diatom inference model. Results suggest that after deglaciation, the lake did not undergo a process of gradual acidification, most likely due to the presence of continuous permafrost and low levels of precipitation, preventing base cations and dissolved organic carbon entering the lake (except for the period between 1.7 and 0.7 ka BP). We conclude that lakes in continental, boreal regions undergo different models of lake ontogeny than oceanic boreal regions. Unlike other regions discussed, climate is a more important driver of ecosystem change than catchment changes. We also demonstrate that the start of the period coincident with the onset of the Little Ice Age resulted in important thresholds crossed in catchment vegetation and aquatic communities.

  16. Beyond just sea-level rise: Considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change

    Science.gov (United States)

    Osland, Michael J.; Enwright, Nicholas M.; Day, Richard H.; Gabler, Christopher A.; Stagg, Camille L.; Grace, James B.

    2016-01-01

    Due to their position at the land-sea interface, coastal wetlands are vulnerable to many aspects of climate change. However, climate change vulnerability assessments for coastal wetlands generally focus solely on sea-level rise without considering the effects of other facets of climate change. Across the globe and in all ecosystems, macroclimatic drivers (e.g., temperature and rainfall regimes) greatly influence ecosystem structure and function. Macroclimatic drivers have been the focus of climate-change related threat evaluations for terrestrial ecosystems, but largely ignored for coastal wetlands. In some coastal wetlands, changing macroclimatic conditions are expected to result in foundation plant species replacement, which would affect the supply of certain ecosystem goods and services and could affect ecosystem resilience. As examples, we highlight several ecological transition zones where small changes in macroclimatic conditions would result in comparatively large changes in coastal wetland ecosystem structure and function. Our intent in this communication is not to minimize the importance of sea-level rise. Rather, our overarching aim is to illustrate the need to also consider macroclimatic drivers within vulnerability assessments for coastal wetlands.

  17. Adapting to Rising Sea Level: A Florida Perspective

    Science.gov (United States)

    Parkinson, Randall W.

    2009-07-01

    Global climate change and concomitant rising sea level will have a profound impact on Florida's coastal and marine systems. Sea-level rise will increase erosion of beaches, cause saltwater intrusion into water supplies, inundate coastal marshes and other important habitats, and make coastal property more vulnerable to erosion and flooding. Yet most coastal areas are currently managed under the premise that sea-level rise is not significant and the shorelines are static or can be fixed in place by engineering structures. The new reality of sea-level rise and extreme weather due to climate change requires a new style of planning and management to protect resources and reduce risk to humans. Scientists must: (1) assess existing coastal vulnerability to address short term management issues and (2) model future landscape change and develop sustainable plans to address long term planning and management issues. Furthermore, this information must be effectively transferred to planners, managers, and elected officials to ensure their decisions are based upon the best available information. While there is still some uncertainty regarding the details of rising sea level and climate change, development decisions are being made today which commit public and private investment in real estate and associated infrastructure. With a design life of 30 yrs to 75 yrs or more, many of these investments are on a collision course with rising sea level and the resulting impacts will be significant. In the near term, the utilization of engineering structures may be required, but these are not sustainable and must ultimately yield to "managed withdrawal" programs if higher sea-level elevations or rates of rise are forthcoming. As an initial step towards successful adaptation, coastal management and planning documents (i.e., comprehensive plans) must be revised to include reference to climate change and rising sea-level.

  18. Analysis of sea level data sequences in Colombian pacific ands its relationship to climate change

    International Nuclear Information System (INIS)

    Rangel, Ernesto Santiago; Montealegre; Jose Edgar

    2003-01-01

    By analyzing series of mean sea level (MSL), data for the towns of Tumaco (01 degrades N 78 degrades 44 minutes W, elevation: 0 meters) and Buenaventura (03 degrades 51 degrades N, 76 degrades 58 minutes W, elevation: 1 meter) the seasonal, intra-annual and inter-annual variability of the MSL are studied in the Colombian pacific, in connection with the el Nino-La Nina - southern oscillation (ENSO) cycle. The detection and the analysis of possible trends are examined in search of likely signal of global change in Colombia. This work concludes that the mean sea level (MSL) data for Tumaco and Buenaventura, are a good indicator, the first one, and a relatively acceptable indicator, the second, of the ENSO cycle, although of very low resolution during the La Nina episodes, in both cases. It was detected equally, a marked tendency for increasing of the mean sea level, approximately starting from the beginnings of the decade of the seventies, which could be related to the higher frequency of warm episodes. Although the longitude of the analyzed series doesn't allow arriving to conclusive results, the increasing tendency of the sea levels during the last twenty years could serve as an early warning in connection with possible manifestations of the global change in Colombia

  19. Understanding extreme sea levels for coastal impact and adaptation analysis

    Science.gov (United States)

    Wahl, T.; Haigh, I. D.; Nicholls, R. J.; Arns, A.; Hinkel, J.; Dangendorf, S.; Slangen, A.

    2016-12-01

    Coastal impact and adaptation assessments require detailed knowledge on extreme sea levels, because increasing damage due to extreme events, such as storm surges and tropical cyclones, is one of the major consequences of sea level rise and climate change. In fact, the IPCC has highlighted in its AR4 report that "societal impacts of sea level change primarily occur via the extreme levels rather than as a direct consequence of mean sea level changes". Over the last few decades, substantial research efforts have been directed towards improved understanding of past and future mean sea level; different scenarios were developed with process-based or semi-empirical models and used for coastal impact assessments at various spatial scales to guide coastal management and adaptation efforts. The uncertainties in future sea level rise are typically accounted for by analyzing the impacts associated with a range of scenarios leading to a vertical displacement of the distribution of extreme sea-levels. And indeed most regional and global studies find little or no evidence for changes in storminess with climate change, although there is still low confidence in the results. However, and much more importantly, there is still a limited understanding of present-day extreme sea-levels which is largely ignored in most impact and adaptation analyses. The two key uncertainties stem from: (1) numerical models that are used to generate long time series of extreme sea-levels. The bias of these models varies spatially and can reach values much larger than the expected sea level rise; but it can be accounted for in most regions making use of in-situ measurements; (2) Statistical models used for determining present-day extreme sea-level exceedance probabilities. There is no universally accepted approach to obtain such values for flood risk assessments and while substantial research has explored inter-model uncertainties for mean sea level, we explore here, for the first time, inter

  20. The roles of fire in Holocene ecosystem changes of West Africa

    Science.gov (United States)

    Dupont, L. M.; Schefuß, E.

    2018-01-01

    The climate changes associated with the Holocene wet phase in the Sahara, the African Humid Period, are subject to ongoing debate discussing interactions between climate and vegetation and possible feedbacks between vegetation, albedo, desertification, and dust. However, very little attention has been given to the role of fire in shaping the land cover, although it is known that fires are important in the formation and consolidation of the African savanna. To fill this gap, we investigated the interaction between precipitation changes, vegetation shifts, and fire occurrence in West Africa by combining stable isotope measurements on plant waxes with pollen and micro-charcoal counts of marine sediments retrieved offshore of Cape Blanc. Our study focuses on the roles of fire at the dry limit of savanna during the Holocene evolution of precipitation changes indicating that the impact of fire during a relative wet climate differs from that during aridification. During the humid early Holocene, increased savanna extension and diversification ran parallel to increased fire occurrence. In contrast, after aridification of northern Africa started at the end of the African Humid Period, a maximum in fire occurrence correlated with a deterioration of the vegetation promoting desertification.

  1. Sea level trends in Southeast Asian seas

    Science.gov (United States)

    Strassburg, M. W.; Hamlington, B. D.; Leben, R. R.; Manurung, P.; Lumban Gaol, J.; Nababan, B.; Vignudelli, S.; Kim, K.-Y.

    2015-05-01

    Southeast Asian seas span the largest archipelago in the global ocean and provide a complex oceanic pathway connecting the Pacific and Indian oceans. The Southeast Asian sea regional sea level trends are some of the highest observed in the modern satellite altimeter record that now spans almost 2 decades. Initial comparisons of global sea level reconstructions find that 17-year sea level trends over the past 60 years exhibit good agreement with decadal variability associated with the Pacific Decadal Oscillation and related fluctuations of trade winds in the region. The Southeast Asian sea region exhibits sea level trends that vary dramatically over the studied time period. This historical variation suggests that the strong regional sea level trends observed during the modern satellite altimeter record will abate as trade winds fluctuate on decadal and longer timescales. Furthermore, after removing the contribution of the Pacific Decadal Oscillation (PDO) to sea level trends in the past 20 years, the rate of sea level rise is greatly reduced in the Southeast Asian sea region. As a result of the influence of the PDO, the Southeast Asian sea regional sea level trends during the 2010s and 2020s are likely to be less than the global mean sea level (GMSL) trend if the observed oscillations in wind forcing and sea level persist. Nevertheless, long-term sea level trends in the Southeast Asian seas will continue to be affected by GMSL rise occurring now and in the future.

  2. Adapting to rates versus amounts of climate change: a case of adaptation to sea-level rise

    Science.gov (United States)

    Shayegh, Soheil; Moreno-Cruz, Juan; Caldeira, Ken

    2016-10-01

    Adaptation is the process of adjusting to climate change in order to moderate harm or exploit beneficial opportunities associated with it. Most adaptation strategies are designed to adjust to a new climate state. However, despite our best efforts to curtail greenhouse gas emissions, climate is likely to continue changing far into the future. Here, we show how considering rates of change affects the projected optimal adaptation strategy. We ground our discussion with an example of optimal investment in the face of continued sea-level rise, presenting a quantitative model that illustrates the interplay among physical and economic factors governing coastal development decisions such as rate of sea-level rise, land slope, discount rate, and depreciation rate. This model shows that the determination of optimal investment strategies depends on taking into account future rates of sea-level rise, as well as social and political constraints. This general approach also applies to the development of improved strategies to adapt to ongoing trends in temperature, precipitation, and other climate variables. Adaptation to some amount of change instead of adaptation to ongoing rates of change may produce inaccurate estimates of damages to the social systems and their ability to respond to external pressures.

  3. The Influence of the Terrestrial Reference Frame on Studies of Sea Level Change

    Science.gov (United States)

    Nerem, R. S.; Bar-Sever, Y. E.; Haines, B. J.; Desai, S.; Heflin, M. B.

    2015-12-01

    The terrestrial reference frame (TRF) provides the foundation for the accurate monitoring of sea level using both ground-based (tide gauges) and space-based (satellite altimetry) techniques. For the latter, tide gauges are also used to monitor drifts in the satellite instruments over time. The accuracy of the terrestrial reference frame (TRF) is thus a critical component for both types of sea level measurements. The TRF is central to the formation of geocentric sea-surface height (SSH) measurements from satellite altimeter data. The computed satellite orbits are linked to a particular TRF via the assumed locations of the ground-based tracking systems. The manner in which TRF errors are expressed in the orbit solution (and thus SSH) is not straightforward, and depends on the models of the forces underlying the satellite's motion. We discuss this relationship, and provide examples of the systematic TRF-induced errors in the altimeter derived sea-level record. The TRF is also crucial to the interpretation of tide-gauge measurements, as it enables the separation of vertical land motion from volumetric changes in the water level. TRF errors affect tide gauge measurements through GNSS estimates of the vertical land motion at each tide gauge. This talk will discuss the current accuracy of the TRF and how errors in the TRF impact both satellite altimeter and tide gauge sea level measurements. We will also discuss simulations of how the proposed Geodetic Reference Antenna in SPace (GRASP) satellite mission could reduce these errors and revolutionize how reference frames are computed in general.

  4. Regional Sea Level Scenarios for Coastal Risk Management: Managing the Uncertainty of Future Sea Level Change and Extreme Water Levels for Department of Defense Coastal Sites Worldwide

    Science.gov (United States)

    2016-04-01

    authors and do not necessarily reflect the view of the authors’ Agencies. MANAGING THE UNCERTAINTY OF FUTURE SEA LEVEL CHANGE AND EXTREME WATER LEVELS FOR...COASTAL RISK MANAGEMENT 2-20 contingent probabilities given their dependence on non-probabilistic emissions futures, have extended the ranges of...flood risk provides confidence in the associated projection as a true minimum value for risk management purposes. The contemporary rate observed by

  5. Keep up or drown: adjustment of western Pacific coral reefs to sea-level rise in the 21st century.

    Science.gov (United States)

    van Woesik, R; Golbuu, Y; Roff, G

    2015-07-01

    Since the Mid-Holocene, some 5000 years ago, coral reefs in the Pacific Ocean have been vertically constrained by sea level. Contemporary sea-level rise is releasing these constraints, providing accommodation space for vertical reef expansion. Here, we show that Porites microatolls, from reef-flat environments in Palau (western Pacific Ocean), are 'keeping up' with contemporary sea-level rise. Measurements of 570 reef-flat Porites microatolls at 10 locations around Palau revealed recent vertical skeletal extension (78±13 mm) over the last 6-8 years, which is consistent with the timing of the recent increase in sea level. We modelled whether microatoll growth rates will potentially 'keep up' with predicted sea-level rise in the near future, based upon average growth, and assuming a decline in growth for every 1°C increase in temperature. We then compared these estimated extension rates with rates of sea-level rise under four Representative Concentration Pathways (RCPs). Our model suggests that under low-mid RCP scenarios, reef-coral growth will keep up with sea-level rise, but if greenhouse gas concentrations exceed 670 ppm atmospheric CO2 levels and with +2.2°C sea-surface temperature by 2100 (RCP 6.0 W m(-2)), our predictions indicate that Porites microatolls will be unable to keep up with projected rates of sea-level rise in the twenty-first century.

  6. Response of the Apodi-Mossoró estuary-incised valley system (NE Brazil to sea-level fluctuations

    Directory of Open Access Journals (Sweden)

    Helenice Vital

    2010-01-01

    Full Text Available This study focuses on the Quaternary sea level changes in the Apodi-Mossoró Estuary and adjacent shelf, Northeastern Brazil, based on the analysis of high-resolution seismic profiles, integrated with echosounder, SRTM and satellite image data. We use these data to develop a relative stratigraphy. An incised-valley extending from the Apodi-Mossoró Estuary onto the shelf dominates the investigated area. In very shallow waters (down to 10 m depth the channel lies mainly in a NW-SE direction, changing to NE-SW in waters below10 m, in the form of a J-shaped valley. The southern flank of the shallow channel presents an abrupt morphology, probably determined by a residual scarp due to neotectonic reactivation of a pre-existing fault. This incised-valley can be correlated with a former river valley formed during the late Pleistocene fall in sea-level. The base-level change related to this drop in sea level can be regionally expressed on seismic lines as a laterally-continuous stratigraphic surface named Horizon I, interpreted as representing the sub-aerial exposure of the continental shelf. Many incised valleys were excavated on this exposed shelf, including that of the Apodi-Mossoró Estuary and its incised valley system. This incised valley has lain buried since the Holocene transgression. The Holocene sediments present sub-horizontal layers, or they have filled the incised valley with oblique features.Este estudo utiliza a integração de dados sísmicos de alta resolução, batimétricos, SRTM e imagens de satélite para desenvolvimento da estratigrafia relativa visando entender as variações do nível do mar durante o Quaternário no estuário do rio Apodi-Mossoró e plataforma adjacente, nordeste do Brasil. A principal feição identificada foi um canal submerso, na plataforma interna, parcialmente preenchido, provavelmente relacionado com o sistema de vales incisos formado durante o rebaixamento do nível do mar no Pleistoceno. O canal

  7. Potential for shoreline changes due to sea-level rise along the U.S. mid-Atlantic region

    Science.gov (United States)

    Gutierrez, Benjamin T.; Williams, S. Jeffress; Thieler, E. Robert

    2007-01-01

    Sea-level rise over the next century is expected to contribute significantly to physical changes along open-ocean shorelines. Predicting the form and magnitude of coastal changes is important for understanding the impacts to humans and the environment. Presently, the ability to predict coastal changes is limited by the scientific understanding of the many variables and processes involved in coastal change, and the lack of consensus regarding the validity of existing conceptual, analytical, or numerical models. In order to assess potential future coastal changes in the mid-Atlantic U.S. for the U.S. Climate Change Science Program (CCSP), a workshop was convened by the U.S. Geological Survey. Assessments of future coastal change were made by a committee of coastal scientists with extensive professional experience in the mid-Atlantic region. Thirteen scientists convened for a two-day meeting to exchange information and develop a consensus opinion on potential future coastal changes for the mid-Atlantic coast in response to sea-level rise. Using criteria defined in past work, the mid-Atlantic coast was divided into four geomorphic compartments: spits, headlands, wave-dominated barriers, and mixed-energy barriers. A range of potential coastal responses was identified for each compartment based on four sea-level rise scenarios. The four scenarios were based on the assumptions that: a) the long-term sea-level rise rate observed over the 20th century would persist over the 21st century, b) the 20th century rate would increase by 2 mm/yr, c) the 20th century rate would increase by 7 mm/yr, or d) sea-level would rise by 2 m over the next few hundred years. Potential responses to these sea-level rise scenarios depend on the landforms that occur within a region and include increased likelihood for erosion and shoreline retreat for all coastal types, increased likelihood for erosion, overwash and inlet breaching for barrier islands, as well as the possibility of a threshold

  8. The Red Sea during the Last Glacial Maximum: implications for sea level reconstructions

    Science.gov (United States)

    Gildor, H.; Biton, E.; Peltier, W. R.

    2006-12-01

    The Red Sea (RS) is a semi-enclosed basin connected to the Indian Ocean via a narrow and shallow strait, and surrounded by arid areas which exhibits high sensitivity to atmospheric changes and sea level reduction. We have used the MIT GCM to investigate the changes in the hydrography and circulation in the RS in response to reduced sea level, variability in the Indian monsoons, and changes in atmospheric temperature and humidity that occurred during the Last Glacial Maximum (LGM). The model results show high sensitivity to sea level reduction especially in the salinity field (increasing with the reduction in sea level) together with a mild atmospheric impact. Sea level reduction decreases the stratification, increases subsurface temperatures, and alters the circulation pattern at the Strait of Bab el Mandab, which experiences a transition from submaximal flow to maximal flow. The reduction in sea level at LGM alters the location of deep water formation which shifts to an open sea convective site in the northern part of the RS compared to present day situation in which deep water is formed from the Gulf of Suez outflow. Our main result based on both the GCM and on a simple hydraulic control model which takes into account mixing process at the Strait of Bab El Mandeb, is that sea level was reduced by only ~100 m in the Bab El Mandeb region during the LGM, i.e. the water depth at the Hanish sill (the shallowest part in the Strait Bab el Mandab) was around 34 m. This result agrees with the recent reconstruction of the LGM low stand of the sea in this region based upon the ICE-5G (VM2) model of Peltier (2004).

  9. Anthropogenic sea level rise and adaptation in the Yangtze estuary

    Science.gov (United States)

    Cheng, H.; Chen, J.; Chen, Z.; Ruan, R.; Xu, G.; Zeng, G.; Zhu, J.; Dai, Z.; Gu, S.; Zhang, X.; Wang, H.

    2016-02-01

    Sea level rise is a major projected threat of climate change. There are regional variations in sea level changes, depending on both naturally the tectonic subsidence, geomorphology, naturally changing river inputs and anthropogenic driven forces as artificial reservoir water impoundment within the watershed and urban land subsidence driven by ground water depletion in the river delta. Little is known on regional sea level fall in response to the channel erosion due to the sediment discharge decline by reservoir interception in the upstream watershed, and water level rise driven by anthropogenic measures as the land reclamation, deep waterway regulation and fresh water reservoir construction to the sea level change in estuaries. Changing coastal cities are situated in the delta regions expected to be threatened in various degrees. Shanghai belongs to those cities. Here we show that the anthropogenic driven sea level rise in the Yangtze estuary from the point of view of the continuous hydrodynamic system consisted of river catchment, estuary and coastal sea. Land subsidence is cited as 4 mm/a (2011-2030). Scour depth of the estuarine channel by upstream engineering as Three Gauge Dam is estimated at 2-10 cm (2011-2030). The rise of water level by deep waterway and land reclamation is estimated at 8-10 cm (2011-2030). The relative sea level rise will be speculated about 10 -16 cm (2011-2030), which these anthropogenic sea level changes will be imposed into the absolute sea level rise 2 mm/a and tectonic subsidence 1 mm/a measured in 1990s. The action guideline to the sea level rise strategy in the Shanghai city have been proposed to the Shanghai government as (1) recent actions (2012-2015) to upgrade the city water supply and drainage engineering and protective engineering; (2) interim actions (2016-2020) to improve sea level monitoring and early warning system, and then the special, city, regional planning considering sea level rise; (3) long term actions (2021

  10. Sea level rise : A literature survey

    NARCIS (Netherlands)

    Oude Essink, G.H.P.

    1992-01-01

    In order to assess the impact of sea level rise on Water Management, it is useful to understand the mechanisrns that determine the level of the sea. In this study, a literature survey is executed to analyze these mechanisms. Climate plays a centra! role in these mechanisms, Climate mainly changes

  11. Sensitivity of Estuaries to Coastal Morphological Change Induced by Sea Level Rise

    Science.gov (United States)

    Alizad, K.; Hagen, S. C.; Bilskie, M. V.; Mariotti, G.

    2017-12-01

    Coastal wetlands play a critical role by providing food and habitat for a variety of species and by dissipating wave and storm surge. These regions are also vulnerable to climate change and specifically rising sea levels. Projections show that coastal marshes across the Northern Gulf of Mexico are threatened by a higher risk of losing their productivity through increased inundation depth and time [Alizad et al., 2016a]. Individual estuaries will respond differently to stressors based on local conditions such as tidal range, creek geometry, and sediment sources, among others. In addition, morphological changes in estuaries are functions of both physical processes such as hydrodynamics and wind waves as well as biological mechanisms. To investigate the sensitivity of storm surge to bio-geomorphological changes associated with climate change within an estuary, the Hydro-MEM model [Alizad et al., 2016b] and first-order bathymetric changes were applied for a set of sea level rise (SLR) scenarios. Morphologic change in the form of marsh platform accretion and enhanced bay bathymetry through time was employed in an ADvanced CIRCulation (ADCIRC) shallow-water equation model. The model was used to run synthetic storm simulations for an intermediate-low (0.5 m), intermediate-high (1.2 m), and high (2.0 m) SLR scenarios in Grand Bay, MS (marine dominated) and Weeks Bay, AL (mixed) estuaries. Results including with and without morphologic changes applied will be discussed. Future steps for incorporating morphological effects including channel widening and wave erosion processes into the Hydro-MEM model is to couple morphologic and hydrodynamic models [Mariotti and Canestrelli, 2017] in the Hydro-MEM time step framework. ReferencesAlizad, K., S. C. Hagen, J. T. Morris, S. C. Medeiros, M. V. Bilskie, and J. F. Weishampel (2016a), Coastal wetland response to sea-level rise in a fluvial estuarine system, Earth's Future, 4(11), 483-497. Alizad, K., S. C. Hagen, J. T. Morris, P

  12. Evidence for change in depositional environment in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, P.S.; Rao, Ch.M.

    Sediments of late Pleistocene and Holocene periods, from a 12 m long core collected at a depth of 3627 m from the Arabian Sea, have been studied in order to understand the depositional environment. Sub-samples selected at 5 cm and occasionally at 10...

  13. Fire regimes and vegetation change in tropical northern Australia during the late-Holocene

    Science.gov (United States)

    Mackenzie, Lydia; Moss, Patrick; Ulm, Sean; Sloss, Craig; Heijnis, Henk; Jacobsen, Geraldine

    2016-04-01

    This study explores the impact of human occupation and abandonment on fire regimes and vegetation communities in the South Wellesley Islands, Gulf of Carpentaria, tropical northern Australia, using charcoal and pollen analysis from four sediment records. Pollen analysis from wetland sediments reveal vegetation succession from mangrove communities to hypersaline mudflats and open woodlands occurred during the late-Holocene. Aquatic species replaced salt tolerant species as the prograding shoreline and dune development formed the Marralda wetlands by 800 cal a BP on the south east coast of Bentinck Island. Wetlands developed on the north and west coast by 500 and 450 cal a BP, respectively. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Wetland initiation encouraged permanent human occupation of the South Wellesley archipelago, with ongoing archaeological research finding permanent occupation in the last 1500 years, followed by a significant increase in sites from 700 years ago, which peaks over the last 300 years. Macro-charcoal (>125μm) accumulation rates provide a record of fire intensity and frequency across the Island. Both local and regional fire events increase in the last 700 years as traditional owners occupied the Island, with local fires occurring every 104 and 74 years on average (N= 4 and 5 respectively). In the 1950's traditional Indigenous Kaiadilt fire management practices ceased, with the frequency and peak magnitude of fire events significantly increasing and vegetation communities becoming more open. The South Wellesley Islands were unoccupied until the 1980's and were not influenced by European occupation. This study of an Island ecosystem during the late-Holocene provides insight into the effect of human presence and fire regimes on vegetation composition and distribution in a fire resilient environment.

  14. Relative sea-level changes and crustal movements in Britain and Ireland since the Last Glacial Maximum

    Science.gov (United States)

    Shennan, Ian; Bradley, Sarah L.; Edwards, Robin

    2018-05-01

    The new sea-level database for Britain and Ireland contains >2100 data points from 86 regions and records relative sea-level (RSL) changes over the last 20 ka and across elevations ranging from ∼+40 to -55 m. It reveals radically different patterns of RSL as we move from regions near the centre of the Celtic ice sheet at the last glacial maximum to regions near and beyond the ice limits. Validated sea-level index points and limiting data show good agreement with the broad patterns of RSL change predicted by current glacial isostatic adjustment (GIA) models. The index points show no consistent pattern of synchronous coastal advance and retreat across different regions, ∼100-500 km scale, indicating that within-estuary processes, rather than decimetre- and centennial-scale oscillations in sea level, produce major controls on the temporal pattern of horizontal shifts in coastal sedimentary environments. Comparisons between the database and GIA model predictions for multiple regions provide potentially powerful constraints on various characteristics of global GIA models, including the magnitude of MWP1A, the final deglaciation of the Laurentide ice sheet and the continued melting of Antarctica after 7 ka BP.

  15. Is sea-level rising?

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.

    correction in the estimation of trends obtained for tide gauge records. The altimeter data permits to prepare spatial maps of sea-level rise trends. We present a map prepared for the Indian Ocean (Figure 4) north of 10oS , which shows a fairly uniform... drawn information from research papers published by the author and report of the IPCC AR5 WG1 Chapter 13: Sea Level Changes, in which the author has served as a ‘Lead Author’. Figure1 is prepared using data from the University of Colorado. Nerem, R...

  16. Radiocarbon dates from the holocene levels at Nelson Bay Cave, and an interim report on their associations

    International Nuclear Information System (INIS)

    Inskeep, R.R.; Vogel, J.C.

    1985-01-01

    Various changes in the cultural material derived from the later Holocene levels of Nelson Bay Cave can be pinpointed in temporal context by means of a large series of radiocarbon dates, such as Carbon 13 and Carbon 14 covering the past 6 000 years. As excavations and analysis of the recovered materials proceeded, radiocarbon dates were sought in order to provide a chronological frame work for what are taken to be significant features in the history of the site, and these are discussed in the article. Several pottery and assumed sheep remains were recorded. Six human burials were also recovered and this helps with the characterization of Holocene burial practices

  17. Examining the evidence for a recent acceleration in the rate of sea-level rise using combined instrumental and proxy data, North Carolina, USA

    Science.gov (United States)

    Kemp, A.; Horton, B. P.

    2007-12-01

    Whilst accelerated rates of relative sea-level (RSL) rise are potentially one of the most devastating impacts of future climate change, our understanding of decadal scale changes in sea-level is poor. This paper seeks to address this knowledge gap by combining tide gauge and high-precision geological reconstructions of relative sea-level of sufficient resolution and duration to detect any recent acceleration in the rate of sea-level rise. We offer a high resolution relative sea-level history for the last ~2000 years from the Albemarle - Pamlico Estuarine System in North Carolina. Contemporary foraminifera were collected from five back barrier marshes to create a regional scale modern training set. The use of multiple marshes from a region increases the ecological and environmental diversity included within the training set and reduces the probability of a no modern analogue outcome. To merge the five spatially distinct sites and to relate each to local tide levels we used the VDatum transformation tool. This method relates all samples to a common orthometric datum (NAVD88) and reduces error. We developed an accurate and precise transfer function to reconstruct former sea levels based upon the modern observable relationship between foraminifera and elevation with respect to the tidal frame. We applied the transfer function to salt-marsh core(s) from Sand Point (Roanoke Island), North Carolina to produce a late Holocene RSL record. An age-depth model was produced from composite chronologies of 210Pb, 14C and pollen chrono-horizons. We validated our approach by comparing geological based reconstructions and instrumental tide gauge records. Our records show that in the last ~2000 years sea level has risen at a background rate of ~1.1mm/yr. There is evidence for two recent accelerations in the rate of sea-level rise during the late 19th and 20th centuries to a current rate of ~4mm/yr.

  18. Sea level: measuring the bounding surfaces of the ocean

    Science.gov (United States)

    Tamisiea, Mark E.; Hughes, Chris W.; Williams, Simon D. P.; Bingley, Richard M.

    2014-01-01

    The practical need to understand sea level along the coasts, such as for safe navigation given the spatially variable tides, has resulted in tide gauge observations having the distinction of being some of the longest instrumental ocean records. Archives of these records, along with geological constraints, have allowed us to identify the century-scale rise in global sea level. Additional data sources, particularly satellite altimetry missions, have helped us to better identify the rates and causes of sea-level rise and the mechanisms leading to spatial variability in the observed rates. Analysis of all of the data reveals the need for long-term and stable observation systems to assess accurately the regional changes as well as to improve our ability to estimate future changes in sea level. While information from many scientific disciplines is needed to understand sea-level change, this review focuses on contributions from geodesy and the role of the ocean's bounding surfaces: the sea surface and the Earth's crust. PMID:25157196

  19. Changes in BOLD and ADC weighted imaging in acute hypoxia during sea-level and altitude adapted states

    DEFF Research Database (Denmark)

    Rostrup, Egill; Larsson, Henrik B.W.; Born, Alfred P.

    2005-01-01

    possible structural changes as measured by diffusion weighted imaging. Eleven healthy sea-level residents were studied after 5 weeks of adaptation to high altitude conditions at Chacaltaya, Bolivia (5260 m). The subjects were studied immediately after return to sea-level in hypoxic and normoxic conditions...... was slightly elevated in high altitude as compared to sea-level adaptation. It is concluded that hypoxia significantly diminishes the BOLD response, and the mechanisms underlying this finding are discussed. Furthermore, altitude adaptation may influence both the magnitude of the activation-related response......, and the examinations repeated 6 months later after re-adaptation to sea-level conditions. The BOLD response, measured at 1.5 T, was severely reduced during acute hypoxia both in the altitude and sea-level adapted states (50% reduction during an average S(a)O(2) of 75%). On average, the BOLD response magnitude was 23...

  20. Drivers of Change in a 7300-Year Holocene Diatom Record from the Hemi-Boreal Region of Ontario, Canada.

    Directory of Open Access Journals (Sweden)

    Kristen K Beck

    Full Text Available A Holocene lake sediment record spanning the past 7300 years from Wishart Lake in the Turkey Lakes Watershed in the Hemi-Boreal of central Ontario, Canada, was used to evaluate the potential drivers of long-term change in diatom assemblages at this site. An analysis of diatom assemblages found that benthic and epiphytic taxa dominated the mid-Holocene (7300-4000 cal yr BP, indicating shallow, oligotrophic, circum-neutral conditions, with macrophytes present. A significant shift in diatom assemblages towards more planktonic species (mainly Cyclotella sensu lato, but also several species of Aulacoseira, and Tabellaria flocculosa occurred ~4000 cal yr BP. This change likely reflects an increase in lake level, coincident with the onset of a more strongly positive moisture balance following the drier climates of the middle Holocene, established by numerous regional paleoclimate records. Pollen-inferred regional changes in vegetation around 4000 yrs BP, including an increase in Betula and other mesic taxa, may have also promoted changes in diatom assemblages through watershed processes mediated by the chemistry of runoff. A more recent significant change in limnological conditions is marked by further increases in Cyclotella sensu lato beginning in the late 19th century, synchronous with the Ambrosia pollen rise and increases in sediment bulk density, signaling regional and local land clearance at the time of Euro-Canadian settlement (1880 AD. In contrast to the mid-Holocene increase in planktonic diatoms, the modern increase in Cyclotella sensu lato likely indicates a response to land use and vegetation change, and erosion from the watershed, rather than a further increase in water level. The results from Wishart Lake illustrate the close connection between paleoclimate change, regional vegetation, watershed processes, and diatom assemblages and also provides insight into the controls on abundance of Cyclotella sensu lato, a diatom taxonomic group

  1. A new Arctic 25-year Altimetric Sea-level Record (1992-2016) and Initial look at Arctic Sea Level Budget Closure

    OpenAIRE

    Andersen O.B., Passaro M., Benveniste J., Piccioni G.

    2016-01-01

    A new initiative within the ESA Sea Level Climate Change initiative (SL-cci) framework to improve the Arctic sea level record has been initiated as a combined effort to reprocess and retrack past altimetry to create a 25-year combined sea level record for sea level research studies. One of the objectives is to retracked ERS-2 dataset for the high latitudes based on the ALES retracking algorithm through adapting the ALES retracker for retracking of specular surfaces (leads). Secondly a reproce...

  2. Holocene precipitation changes in the deep tropics recorded by Speleothems (Invited)

    Science.gov (United States)

    Wang, X.; Auler, A. S.; Edwards, R.; Kong, X.; Cheng, H.; Cruz, F. W.; Wang, Y.; Broecker, W. S.

    2010-12-01

    We have obtained a high-resolution oxygen isotope (δ18O) record of cave calcite from Paraiso Cave, eastern Amazon, which covers most of the Holocene. Its chronology was determined by U-Th ages from three column-shaped stalagmites. Their δ18O profiles replicate among their contemporaneous growth periods. Therefore, the samples were likely precipitated under equilibrium conditions and their oxygen isotopic variations are primarily caused by climate change. We find that the δ18O decreases steadily from ~11.0 to 5.0 thousand years ago, with a growth gap between ~8.4 to 6.3 thousand years ago, and then gradually increases until the present. The large amplitude of the δ18O change (up to 4 per mil) suggests that the variation in δ18O value is dominated by meteoric precipitation change at this equatorial site. In order to investigate the interactions between the Intertropical Convergence Zone (ITCZ), monsoons and El Niño-Southern Oscillation (ENSO) activity during the Holocene, we compare the Paraiso record to speleothem records from other locations in the deep tropics, namely, cave sites from Flores, Borneo and Peru. We find that all these speleothem records are consistent, with a progressive δ18O decrease (rainfall increase) during the early Holocene, probably in response to the southward retreat of the ITCZ from its northernmost location in the early Holocene. This is evident from the strong anti-correlation between the speleothem monsoonal records from China and southern Brazil. However, our record is distinct from the others during the last 4 thousand years, when it switches to a continuous δ18O increase (rainfall decrease) trend, while the others flatten out. We propose that, during the late Holocene, the strengthened South American Summer Monsoon may override the ENSO influence and cause the discrepancy in precipitation between eastern Amazon and other deep tropical cave sites.

  3. Development of new geoinformation methods for modelling and prediction of sea level change over different timescales - overview of the project

    Science.gov (United States)

    Niedzielski, T.; Włosińska, M.; Miziński, B.; Hewelt, M.; Migoń, P.; Kosek, W.; Priede, I. G.

    2012-04-01

    The poster aims to provide a broad scientific audience with a general overview of a project on sea level change modelling and prediction that has just commenced at the University of Wrocław, Poland. The initiative that the project fits, called the Homing Plus programme, is organised by the Foundation for Polish Science and financially supported by the European Union through the European Regional Development Fund and the Innovative Economy Programme. There are two key research objectives of the project that complement each other. First, emphasis is put on modern satellite altimetric gridded time series from the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) repository. Daily sea level anomaly maps, access to which in near-real time is courtesy of AVISO, are being steadily downloaded every day to our local server in Wroclaw, Poland. These data will be processed within a general framework of modelling and prediction of sea level change in short, medium and long term. Secondly, sea level change over geological time is scrutinised in order to cover very long time scales that go far beyond a history of altimetric and tide-gauge measurements. The aforementioned approaches comprise a few tasks that aim to solve the following detailed problems. Within the first one, our objective is to seek spatio-temporal dependencies in the gridded sea level anomaly time series. Subsequently, predictions that make use of such cross-correlations shall be derived, and near-real time service for automatic update with validation will be implemented. Concurrently, (i.e. apart from spatio-temporal dependencies and their use in the process of forecasting variable sea level topography), threshold models shall be utilised for predicting the El Niño/Southern Oscillation (ENSO) signal that is normally present in sea level anomaly time series of the equatorial Pacific. Within the second approach, however, the entirely different methods are proposed. Links between

  4. Measuring Sea Level Rise-Induced Shoreline Changes and Inundation in Real Time

    Science.gov (United States)

    Shilling, F.; Waetjen, D.; Grijalva, E.

    2016-12-01

    We describe a method to monitor shoreline inundation and changes in response to sea level rise (SLR) using a network of time-lapse cameras. We found for coastal tidal marshes that this method was sensitive to vertical changes in sea level of 20 cm has occurred in the San Francisco Bay and other US coastal areas and is likely to rise by another 30-45 cm by mid-century, which will flood and erode many coastal ecosystems, highways, and urban areas. This rapid degree of rise means that it is imperative to co-plan for natural and built systems. Many public facilities are adjacent to shoreline ecosystems, which both protect infrastructure from wave and tide energy and are home to regulated species and habitats. Accurate and timely information about the actual extent of SLR impacts to shorelines will be critical during built-system adaptation. Currently, satellite-sourced imagery cannot provide the spatial or temporal resolution necessary to investigate fine-scale shoreline changes, leaving a gap between predictive models and knowing how, where and when these changes are occurring. The method described is feasible for near-term (1 to 10 years) to long-term application and can be used for measuring fine-resolution shoreline changes (organize photographs that could be combined with related external data (e.g., gauged water levels) to create an information mashup. This information could be used to validate models predicting shoreline inundation and loss, inform SLR-adaptation planning, and to visualize SLR impacts to the public.

  5. Mid-Holocene to Present Climate Transition in Tropical South America

    Science.gov (United States)

    Turcq, B.; Cordeiro, R.; Sifeddine, A.; Braconnot, P.; Dias, P. S.; Costa, R.; Jorgetti, T.

    2008-12-01

    The classical illustration of Holocene climate changes in tropical South America is the huge rising of Titicaca lake level from 4400 to 4000 cal BP. Because the Amazon basin is the source of Andean rainfalls we have explored Amazonian data of climate changes during the Holocene to better understand the cause of this abrupt transition. Amazonian data confirm the existence of mid-Holocene dryness: (1) lacustrine level studies show a lower precipitation/evaporation budget than present, with the lowest lake levels between 8500 and 6800 cal BP; (2) although the dominant Holocene vegetation has always been the rainforest in the heart of Amazonia, this forest expanded towards the northwestern and southwestern regions from 6800 to 1550 cal BP, moreover, pioneer elements of the rainforest developed during the mid-Holocene and the best example is those of Cecropia, between 9000 and 5000 cal BP. (3) soil d13C indicates a forest expansion over savannas areas in Roraima (north), Mato Grosso and Rondonia (southwest), during the Holocene. (4) the mid-Holocene (8000- 4000 cal BP) is characterized by repeated occurrences of forest fires, marked by the presence of charcoals in soils and lacustrine sediments. However these different records are not characterized by abrupt transitions at the end of the Middle Holocene in Amazonia. In the Andean records there is a clear north-south shift in the timing of the transition. Analysis of coupled Ocean Atmosphere Model simulations suggest that convection in Amazon basin is directly controlled by insolation leading to an almost linear response of local climate to the global forcing. Differently, in the eastern and south-western regions where the rain is brought by the South American Monsoon, the climate transition appears more abrupt. It may be because the involved climate mechanisms are more complex and depend on Ocean/Atmosphere/Vegetation coupled process (ITCZ position, ZCAS formation, etc.). Tectonic movements or threshold links to

  6. Beyond just sea-level rise: considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change.

    Science.gov (United States)

    Osland, Michael J; Enwright, Nicholas M; Day, Richard H; Gabler, Christopher A; Stagg, Camille L; Grace, James B

    2016-01-01

    Due to their position at the land-sea interface, coastal wetlands are vulnerable to many aspects of climate change. However, climate change vulnerability assessments for coastal wetlands generally focus solely on sea-level rise without considering the effects of other facets of climate change. Across the globe and in all ecosystems, macroclimatic drivers (e.g., temperature and rainfall regimes) greatly influence ecosystem structure and function. Macroclimatic drivers have been the focus of climate change-related threat evaluations for terrestrial ecosystems, but largely ignored for coastal wetlands. In some coastal wetlands, changing macroclimatic conditions are expected to result in foundation plant species replacement, which would affect the supply of certain ecosystem goods and services and could affect ecosystem resilience. As examples, we highlight several ecological transition zones where small changes in macroclimatic conditions would result in comparatively large changes in coastal wetland ecosystem structure and function. Our intent in this communication is not to minimize the importance of sea-level rise. Rather, our overarching aim is to illustrate the need to also consider macroclimatic drivers within vulnerability assessments for coastal wetlands. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

  7. Holocene Demographic Changes and the Emergence of Complex Societies in Prehistoric Australia.

    Directory of Open Access Journals (Sweden)

    Alan N Williams

    Full Text Available A continental-scale model of Holocene Australian hunter-gatherer demography and mobility is generated using radiocarbon data and geospatial techniques. Results show a delayed expansion and settlement of much of Australia following the termination of the late Pleistocene until after 9,000 years ago (or 9ka. The onset of the Holocene climatic optimum (9-6ka coincides with rapid expansion, growth and establishment of regional populations across ~75% of Australia, including much of the arid zone. This diffusion from isolated Pleistocene refugia provides a mechanism for the synchronous spread of pan-continental archaeological and linguistic attributes at this time (e.g. Pama-Nyungan language, Panaramitee art style, backed artefacts. We argue longer patch residence times were possible at the end of the optimum, resulting in a shift to more sedentary lifestyles and establishment of low-level food production in some parts of the continent. The onset of El Niño - Southern Oscillation (ENSO; 4.5-2ka restricted low-level food production, and resulted in population fragmentation, abandonment of marginal areas, and reduction in ranging territory of ~26%. Importantly, climate amelioration brought about by more pervasive La Niña conditions (post-2ka, resulted in an intensification of the mobility strategies and technological innovations that were developed in the early- to mid-Holocene. These changes resulted in population expansion and utilization of the entire continent. We propose that it was under these demographically packed conditions that the complex social and religious societies observed at colonial contact were formed.

  8. Holocene Demographic Changes and the Emergence of Complex Societies in Prehistoric Australia

    Science.gov (United States)

    Williams, Alan N.; Ulm, Sean; Turney, Chris S. M.; Rohde, David; White, Gentry

    2015-01-01

    A continental-scale model of Holocene Australian hunter-gatherer demography and mobility is generated using radiocarbon data and geospatial techniques. Results show a delayed expansion and settlement of much of Australia following the termination of the late Pleistocene until after 9,000 years ago (or 9ka). The onset of the Holocene climatic optimum (9-6ka) coincides with rapid expansion, growth and establishment of regional populations across ~75% of Australia, including much of the arid zone. This diffusion from isolated Pleistocene refugia provides a mechanism for the synchronous spread of pan-continental archaeological and linguistic attributes at this time (e.g. Pama-Nyungan language, Panaramitee art style, backed artefacts). We argue longer patch residence times were possible at the end of the optimum, resulting in a shift to more sedentary lifestyles and establishment of low-level food production in some parts of the continent. The onset of El Niño - Southern Oscillation (ENSO; 4.5-2ka) restricted low-level food production, and resulted in population fragmentation, abandonment of marginal areas, and reduction in ranging territory of ~26%. Importantly, climate amelioration brought about by more pervasive La Niña conditions (post-2ka), resulted in an intensification of the mobility strategies and technological innovations that were developed in the early- to mid-Holocene. These changes resulted in population expansion and utilization of the entire continent. We propose that it was under these demographically packed conditions that the complex social and religious societies observed at colonial contact were formed. PMID:26083101

  9. Effect of glacial-interglacial sea-level changes on the displacement and stress field in the forearc and along the plate interface of subduction zones

    Directory of Open Access Journals (Sweden)

    T. Li

    2012-02-01

    Full Text Available Combined seismological, space-geodetic and numerical studies have shown that the seismicity at subduction zones may be modulated by tides and glacier fluctuations on timescales of 1–100 a, because these changes in loads on Earth's surface are able to alter the stress field in the upper plate and along the plate interface. Here we use a two-dimensional finite-element model of a subduction zone to investigate how glacial-interglacial sea-level changes affect the forearc region and the plate interface. The model results show that a sea-level fall by 125 m over 100 ka causes up to 0.7 m of vertical displacement, with the maximum uplift occurring between the trench and the coast. The uplift signal induced by the sea-level fall decreases to zero ~20 km landward of the coastline. A subsequent sea-level rise by 125 m over 20 ka causes subsidence, which is again most pronounced in the submarine part of the forearc. The sea-level changes cause horizontal displacements of up to 0.12 m, which are directed seaward during sea-level fall and landward during sea-level rise. With respect to the stress field, the sea-level changes lead to variations in the vertical stress and the shear stress of up to 1.23 MPa and 0.4 MPa, respectively. The shear stress variations are highest beneath the coast, i.e. in the area where the sea-level changes cause the strongest flexure. The resulting Coulomb stress changes on the plate interface are of the order of 0.2–0.5 MPa and indicate that earthquakes are promoted during sea-level fall and delayed during sea-level rise. Our findings imply that eustatic sea-level changes during glacial-interglacial periods may have induced displacements and stress changes that were large enough to affect the seismic cycle of subduction thrusts.

  10. Stratigraphic and microfossil evidence for hydroclimate changes over the middle to late Holocene in the northern Bahamas from an inland saline lake

    Science.gov (United States)

    van Hengstum, P. J.; Maale, G. E.; Donnelly, J. P.; Onac, B. P.; Sullivan, R.; Winkler, T. S.; Albury, N. A.

    2016-12-01

    No Man's Land is one of the largest inland lakes on the Little Bahama Bank in the northern Bahamas, so its paleoenvironmental history may provide insight into how the regional hydroclimate developed over the Holocene. In its modern state, the site is shallow (aquatic invertebrates (e.g., ostracodes, foraminifera, aquatic mollusks) indicate that the site was a terrestrial ecosystem. However, the site transitioned into a subaqueous freshwater environment at 6400 Cal yrs BP, and the site became a palustrine-lacustrine setting thereafter until 4200 Cal yrs BP. During this time, widespread palustrine-lacustrine carbonate deposition and the appearance of freshwater to low mesohaline microfossils indicates that the lake's salinity was likely oligohaline (charophytes, ostracodes: Candona annae, Cypridopsis vidua, foraminifera: Helenina davescottensis, mollusks: Planorbis, Hydrobia). A salinity increase at 4200 Cal yrs BP is inferred from the appearance of the ostracode Cyprideis americana that typically prefers salinities exceeding 10 psu, and deposition of laminated microbial mats. Thereafter, an organic- rich, algal sapropel unit accumulated that was devoid of any microfossils or mollusks. This unit suggests that the lake hosted a stratified water column, where surface waters supported phytoplankton primary productivity and corrosive or anoxic bottom water conditions either hampered microfossil growth or precluded their preservation. The transition to the modern environment ( 20 psu) at 2600 cal yrs BP is characterized by diversification of brackish ostracodes (Aurila floridana, Dolerocypria inopinata, and Hemicyprideis setipunctata), foraminifera (Elphidium spp., Ammonia beccarii, Triloculina oblonga) and mollusks (Anomalocardia, Cerithidea). Over the middle to late Holocene, it appears that the stratigraphic development and salinity changes in No Man's Land has been driven by groundwater-level rise in response to Holocene sea-level rise, the regional delivery of fresh

  11. Current state and future perspectives on coupled ice-sheet - sea-level modelling

    Science.gov (United States)

    de Boer, Bas; Stocchi, Paolo; Whitehouse, Pippa L.; van de Wal, Roderik S. W.

    2017-08-01

    The interaction between ice-sheet growth and retreat and sea-level change has been an established field of research for many years. However, recent advances in numerical modelling have shed new light on the precise interaction of marine ice sheets with the change in near-field sea level, and the related stability of the grounding line position. Studies using fully coupled ice-sheet - sea-level models have shown that accounting for gravitationally self-consistent sea-level change will act to slow down the retreat and advance of marine ice-sheet grounding lines. Moreover, by simultaneously solving the 'sea-level equation' and modelling ice-sheet flow, coupled models provide a global field of relative sea-level change that is consistent with dynamic changes in ice-sheet extent. In this paper we present an overview of recent advances, possible caveats, methodologies and challenges involved in coupled ice-sheet - sea-level modelling. We conclude by presenting a first-order comparison between a suite of relative sea-level data and output from a coupled ice-sheet - sea-level model.

  12. Estimating sea-level allowances for Atlantic Canada under conditions of uncertain sea-level rise

    Directory of Open Access Journals (Sweden)

    B. Greenan

    2015-03-01

    Full Text Available This paper documents the methodology of computing sea-level rise allowances for Atlantic Canada in the 21st century under conditions of uncertain sea-level rise. The sea-level rise allowances are defined as the amount by which an asset needs to be raised in order to maintain the same likelihood of future flooding events as that site has experienced in the recent past. The allowances are determined by combination of the statistics of present tides and storm surges (storm tides and the regional projections of sea-level rise and associated uncertainty. Tide-gauge data for nine sites from the Canadian Atlantic coast are used to derive the scale parameters of present sea-level extremes using the Gumbel distribution function. The allowances in the 21st century, with respect to the year 1990, were computed for the Intergovernmental Panel on Climate Change (IPCC A1FI emission scenario. For Atlantic Canada, the allowances are regionally variable and, for the period 1990–2050, range between –13 and 38 cm while, for the period 1990–2100, they range between 7 and 108 cm. The negative allowances in the northern Gulf of St. Lawrence region are caused by land uplift due to glacial isostatic adjustment (GIA.

  13. The Holocene sedimentary history of the Kangerlussuaq Fjord-valley fill, West Greenland

    DEFF Research Database (Denmark)

    Storms, Joep E.A.; de Winter, Ilja L.; Overeem, Irina

    2012-01-01

    valleys. Based on published and new land- and sea-based geophysical data, radiocarbon dates and geological observations we have characterized the infill and reconstructed the sedimentation history during the Holocene. Based on a revised sea level curve and data presented in this paper we defined three...... depocenters by a flood plain which transferred sediment from the GIS to the Keglen delta. Ongoing sea level fall due to glacio-isostastic uplift combined with a gradually cooler and dryer climate resulted in terrace formation along the Watson River flood plain. Around 4000 yr BP, the GIS margin reached its...... most landward location and began to advance to its present location. The final phase (Phase III; channels...

  14. A System of Systems Approach to Integrating Global Sea Level Change Application Programs

    Science.gov (United States)

    Bambachus, M. J.; Foster, R. S.; Powell, C.; Cole, M.

    2005-12-01

    The global sea level change application community has numerous disparate models used to make predications over various regional and temporal scales. These models have typically been focused on limited sets of data and optimized for specific areas or questions of interest. Increasingly, decision makers at the national, international, and local/regional levels require access to these application data models and want to be able to integrate large disparate data sets, with new ubiquitous sensor data, and use these data across models from multiple sources. These requirements will force the Global Sea Level Change application community to take a new system-of-systems approach to their programs. We present a new technical architecture approach to the global sea level change program that provides external access to the vast stores of global sea level change data, provides a collaboration forum for the discussion and visualization of data, and provides a simulation environment to evaluate decisions. This architectural approach will provide the tools to support multi-disciplinary decision making. A conceptual system of systems approach is needed to address questions around the multiple approaches to tracking and predicting Sea Level Change. A systems of systems approach would include (1) a forum of data providers, modelers, and users, (2) a service oriented architecture including interoperable web services with a backbone of Grid computing capability, and (3) discovery and access functionality to the information developed through this structure. Each of these three areas would be clearly designed to maximize communication, data use for decision making and flexibility and extensibility for evolution of technology and requirements. In contemplating a system-of-systems approach, it is important to highlight common understanding and coordination as foundational to success across the multiple systems. The workflow of science in different applications is often conceptually similar

  15. Beach- ridge internal architecture and use for Holocene sea-level reconstruction: A case study from the Miquelon-Langlade Isthmus (NW Atlantic)

    Science.gov (United States)

    Hein, C. J.; Billy, J.; Robin, N.; FitzGerald, D.; Certain, R.

    2017-12-01

    The internal architecture of beach-ridge systems can provide insight into processes ongoing during its period of formation, such as changing relative sea-level (RSL). The paraglacial beach-ridge plain at Miquelon-Langlade (south of Newfoundland - NW Atlantic) is an example of a well-preserved regressive barrier. Initiation of this plain correlates with a decrease in the rate of RSL rise (from +4.4 mm/yr to 1.3 mm/yr) at around 3000 years ago. The combination of stratigraphic (ground-penetrating radar and sediment cores), topographic (RTK-GPS) and chronologic (optically stimulated luminescence, OSL) data provide a detailed understanding of the constructional history of the plain. The internal architecture of individual beach ridges are characterized by sigmoidal configurations with seaward-dipping (2.3-4.7°) beds. Field mapping data reveal the processes associated with development of individual ridges in relation to sea level elevation. First, wave-built facies (sand-and-gravel) are deposited as beach berms, likely by fair-weather waves, with their elevations controlled by sea level and the swash height of constructive waves. This is followed by the accretion of aeolian sand deposits (foredunes) on the previous relict ridge, and then colonization by pioneer grasses. The well-defined contact between coarse-grained, wave-built facies and overlying aeolian deposits is used to demonstrate the dominant influence of RSL change in the development of the barrier system and, with chronology provided by OSL dating, produce a RSL curve for the 2500-year period of its formation. A net increase of 2.4 m in the surface elevation of wave-built facies is observed across the plain, corresponding to an overall increase in mean sea level through time. Three distinct periods can be distinguished: (1) an increase from 2.4 to 1 m below modern MSL between 2400 and 1500 years (rate: +1.3 mm/yr); (2) relatively stable or slowly rising RSL (<+0.2 mm/yr) from 1400 to 700 years; and (3) a

  16. Changes in North Atlantic deep-sea temperature during climatic fluctuations of the last 25,000 years based on ostracode Mg/Ca ratios

    Science.gov (United States)

    Dwyer, Gary S.; Cronin, Thomas M.; Baker, Paul A.; Rodriguez-Lazaro, Julio

    2000-01-01

    We reconstructed three time series of last glacial-to-present deep-sea temperature from deep and intermediate water sediment cores from the western North Atlantic using Mg/Ca ratios of benthic ostracode shells. Although the Mg/Ca data show considerable variability (“scatter”) that is common to single-shell chemical analyses, comparisons between cores, between core top shells and modern bottom water temperatures (BWT), and comparison to other paleo-BWT proxies, among other factors, suggest that multiple-shell average Mg/Ca ratios provide reliable estimates of BWT history at these sites. The BWT records show not only glacial-to-interglacial variations but also indicate BWT changes during the deglacial and within the Holocene interglacial stage. At the deeper sites (4500- and 3400-m water depth), BWT decreased during the last glacial maximum (LGM), the late Holocene, and possibly during the Younger Dryas. Maximum deep-sea warming occurred during the latest deglacial and early Holocene, when BWT exceeded modern values by as much as 2.5°C. This warming was apparently most intense around 3000 m, the depth of the modern-day core of North Atlantic deep water (NADW). The BWT variations at the deeper water sites are consistent with changes in thermohaline circulation: warmer BWT signifies enhanced NADW influence relative to Antarctic bottom water (AABW). Thus maximum NADW production and associated heat flux likely occurred during the early Holocene and decreased abruptly around 6500 years B.P., a finding that is largely consistent with paleonutrient studies in the deep North Atlantic. BWT changes in intermediate waters (1000-m water depth) of the subtropical gyre roughly parallel the deep BWT variations including dramatic mid-Holocene cooling of around 4°C. Joint consideration of the Mg/Ca-based BWT estimates and benthic oxygen isotopes suggests that the cooling was accompanied by a decrease in salinity at this site. Subsequently, intermediate waters warmed to modern

  17. Future extreme sea level seesaws in the tropical Pacific.

    Science.gov (United States)

    Widlansky, Matthew J; Timmermann, Axel; Cai, Wenju

    2015-09-01

    Global mean sea levels are projected to gradually rise in response to greenhouse warming. However, on shorter time scales, modes of natural climate variability in the Pacific, such as the El Niño-Southern Oscillation (ENSO), can affect regional sea level variability and extremes, with considerable impacts on coastal ecosystems and island nations. How these shorter-term sea level fluctuations will change in association with a projected increase in extreme El Niño and its atmospheric variability remains unknown. Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño-related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence. Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

  18. Sea level: measuring the bounding surfaces of the ocean.

    Science.gov (United States)

    Tamisiea, Mark E; Hughes, Chris W; Williams, Simon D P; Bingley, Richard M

    2014-09-28

    The practical need to understand sea level along the coasts, such as for safe navigation given the spatially variable tides, has resulted in tide gauge observations having the distinction of being some of the longest instrumental ocean records. Archives of these records, along with geological constraints, have allowed us to identify the century-scale rise in global sea level. Additional data sources, particularly satellite altimetry missions, have helped us to better identify the rates and causes of sea-level rise and the mechanisms leading to spatial variability in the observed rates. Analysis of all of the data reveals the need for long-term and stable observation systems to assess accurately the regional changes as well as to improve our ability to estimate future changes in sea level. While information from many scientific disciplines is needed to understand sea-level change, this review focuses on contributions from geodesy and the role of the ocean's bounding surfaces: the sea surface and the Earth's crust. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  19. Causes of early Holocene desertification in arid central Asia

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Liya [Lanzhou University, Key Laboratory of Western China' s Environmental System, Lanzhou, Gansu (China); University of Kiel, Institute of Geosciences, Kiel (Germany); Chen, Fahu [Lanzhou University, Key Laboratory of Western China' s Environmental System, Lanzhou, Gansu (China); Morrill, Carrie [University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO (United States); NOAA' s National Climatic Data Center, Paleoclimatology Branch, Boulder, CO (United States); Otto-Bliesner, Bette L.; Rosenbloom, Nan [National Center for Atmospheric Research, Climate and Global Dynamics Division, Boulder, CO (United States)

    2012-04-15

    Paleoclimate records of effective moisture (precipitation minus evaporation, or P-E) show a dry (low effective moisture) period in mid-latitude arid/semi-arid central Asia during the early Holocene (11,000-8,000 years ago) relative to the middle and late Holocene, in contrast to evidence for greater-than-present precipitation at the same time in the south and east Asian monsoonal areas. To investigate the spatial differences in climate response over mid-latitude central Asia and monsoonal Asia we conducted a series of simulations with the Community Climate System Model version 3 coupled climate model for the early, middle and late Holocene. The simulations test the climatic impact of all important forcings for the early Holocene, including changes in orbital parameters, the presence of the remnant Laurentide ice sheet and deglacial freshening of the North Atlantic. Model results clearly show the early Holocene patterns indicated by proxy records, including both the decreased effective moisture in arid central Asia, which occurs in the model primarily during the winter months, and the increase in summer monsoon precipitation in south and east Asia. The model results suggest that dry conditions in the early Holocene in central Asia are closely related to decreased water vapor advection due to reduced westerly wind speed and less evaporation upstream from the Mediterranean, Black, and Caspian Seas in boreal winter. As an extra forcing to the early Holocene climate system, the Laurentide ice sheet and meltwater fluxes have a substantial cooling effect over high latitudes, especially just over and downstream of the ice sheets, but contribute only to a small degree to the early Holocene aridity in central Asia. Instead, most of the effective moisture signal can be explained by orbital forcing decreasing the early Holocene latitudinal temperature gradient and wintertime surface temperature. We find little evidence for regional subsidence related to a stronger summer Asian

  20. Detecting sea-level hazards: Simple regression-based methods for calculating the acceleration of sea level

    Science.gov (United States)

    Doran, Kara S.; Howd, Peter A.; Sallenger,, Asbury H.

    2016-01-04

    This report documents the development of statistical tools used to quantify the hazard presented by the response of sea-level elevation to natural or anthropogenic changes in climate and ocean circulation. A hazard is a physical process (or processes) that, when combined with vulnerability (or susceptibility to the hazard), results in risk. This study presents the development and comparison of new and existing sea-level analysis methods, exploration of the strengths and weaknesses of the methods using synthetic time series, and when appropriate, synthesis of the application of the method to observed sea-level time series. These reports are intended to enhance material presented in peer-reviewed journal articles where it is not always possible to provide the level of detail that might be necessary to fully support or recreate published results.

  1. Sea-level rise: towards understanding local vulnerability

    Science.gov (United States)

    Rahmstorf, Stefan

    2012-06-01

    , experts are increasingly looking at its potential impacts on coasts to facilitate local adaptation planning. This is a more complex issue than one might think, because different stretches of coast can be affected in very different ways. First of all, the sea-level response to global warming will not be globally uniform, since factors like changes in ocean currents (Levermann et al 2005) and the changing gravitational pull of continental ice (Mitrovica et al 2001) affect the local rise. Secondly, superimposed on the climatic trend is natural variability in sea level, which regionally can be as large as the climatic signal on multi-decadal timescales. Over the past decades, sea level has dropped in sizable parts of the world ocean, although it has of course risen in global mean (IPCC 2007). Thirdly, local land uplift or subsidence affects the local sea-level change relative to the coast, both for natural reasons (post-glacial isostatic adjustment centred on regions that were covered by ice sheets during the last ice age) and artificial ones (e.g., extraction of water or oil as in the Gulf of Mexico). Finally, local vulnerability to sea-level rise depends on many factors. Two interesting new studies in this journal (Tebaldi et al 2012, Strauss et al 2012) make important steps towards understanding sea-level vulnerability along the coasts of the United States, with methods that could also be applied elsewhere. The first, by Strauss and colleagues, merges high-resolution topographic data and a newly available tidal model together with population and housing data in order to estimate what land area and population would be at risk given certain increments in sea level. The results are mapped and tabulated at county and city level. They reveal the 'hot spots' along the US coast where sea-level rise is of the highest concern because of large populations living near the high-tide line: New York City and Long Island; the New Jersey shore; the Norfolk, Virginia, area; near Charleston

  2. Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmosphere in the Okinawa Trough during the Holocene and their paleoclimatic implications

    Institute of Scientific and Technical Information of China (English)

    MENGXianwei; LIUYanguang; LlUZhenxia; DUDewen; HUANGQiyu; Y.Saito

    2003-01-01

    The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index U37k of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed.Consequently, three cooling events (E1-E3) were identified,each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.

  3. Holocene coral patch reef ecology and sedimentary architecture, Northern Belize, Central America

    Energy Technology Data Exchange (ETDEWEB)

    Mazzullo, S.J.; Anderson-Underwood, K.E.; Burke, C.D.; Bischoff, W.D. (Wichita State Univ., KS (United States))

    1992-12-01

    Coral patch reefs are major components of Holocene platform carbonate facies systems in tropical and subtropical areas. The biotic composition, growth and relationship to sea level history, and diagenetic attributes of a representative Holocene patch reef ([open quotes]Elmer Reef[close quotes]) in the Mexico Rocks complex in northern Belize are described and compared to those of Holocene patch reefs in southern Belize. Elmer Reef has accumulated in shallow (2.5 m) water over the last 420 yr, under static sea level conditions. Rate of vertical construction is 0.3-0.5 m/100 yr, comparable to that of patch reefs in southern Belize. A pronounced coral zonation exists across Elmer Reef, with Monastrea annularis dominating on its crest and Acropora cervicornis occurring on its windward and leeward flanks. The dominance of Montastrea on Elmer Reef is unlike that of patch reefs in southern Belize, in which this coral assumes only a subordinate role in reef growth relative to that of Acropora palmata. Elmer Reef locally is extensively biodegraded and marine, fibrous aragonite and some bladed high-magnesium calcite cements occur throughout the reef section, partially occluding corallites and interparticle pores in associated sands. Patch reefs in southern Belize have developed as catch-up and keep-up reefs in a transgressive setting. In contrast, the dominant mode of growth of Elmer Reef, and perhaps other patch reefs in Mexico Rocks, appears to be one of lateral rather than vertical accretion. This style of growth occurs in a static sea level setting where there is only limited accommodation space because of the shallowness of the water, and such reefs are referred to as [open quotes]expansion reefs[close quotes]. 39 refs., 8 figs., 2 tabs.

  4. Holocene Activity of the Enriquillo-Plantain Garden Fault in Lake Enriquillo Derived from Seismic Stratigraphy

    Science.gov (United States)

    Rios, J. K.; McHugh, C. M.; Hornbach, M. J.; Mann, P.; Wright, V. D.; Gurung, D.

    2013-12-01

    The Enriquillo-Plantain-Garden fault zone (EPGF) crosses Lake Enriquillo (LE) in the Dominican Republic and extends E-W across the southern peninsula of Haiti, south of the Baie de Port au Prince (BPP). Seismic stratigraphic studies of CHIRP high-resolution subbottom profiles calibrated to ages obtained from sediment cores and previous coral reef studies provide a Holocene record of relative sea level rise into the BPB and LE and a time frame for understanding tectonics of the EPGF. The BPP is 20 km wide, 20 km long, 150 m deep, and surrounded by coral reefs at water depths of 30 m. Three seismic units were identified: Unit 1: stepped terraces 5-10 m high. Laminated strata onlaps the terraces. This unit possibly represents Marine Isotope Stages 6 and 5, but has not been dated. Unit 2: laminated strata, thicker than 10 m and dated near its top at 22 ka BP. The microfossil assemblages reveal that during the latest Pleistocene sea level lowstand the BPP had a restricted connection with the global ocean. Few well-preserved marine microfossils are present and mostly are reworked. Geochemical analyses reveal that the laminated sediments were deposited during wet periods (>Si, Al wt %, Cu ppm) and dry periods (>Ca wt %). Unit 3: acoustically transparent, ~10 m thick, dated near its base and top at 14 ka BP and 2 ka BP, respectively. This unit represents the Holocene initiation of sea level rise and high stand containing well-preserved marine fossils. At ~9.5 ka BP planktonic foraminifers become abundant implying deepening of marine waters. Lake Enriquillo is 127 km east of the BPP. It is 15 km wide, 40 km long and 45 m deep. CHIRP subbottom profiles penetrated ~30 m below the lake floor. Four main acoustic units were identified: Unit 1: deformed basement with steeply dipping and folded beds. Based on land studies this unit is likely Plio-Pleistocene in age. Unit 2: laminated strata. Ages from coral reefs and deformed strata on land indicate this unit is likely pre-20 ka

  5. 3D characterization of Holocene peat in the Netherlands : Implications for coastal-deltaic subsidence

    NARCIS (Netherlands)

    Koster, K.

    2017-01-01

    Human-induced subsidence threatens many coastal-deltaic plains, due to the amplifying effects it has on sea-level rise and flood risk. In the coastal-deltaic plain of the Netherlands, subsidence is primarily caused by the compression and oxidation of Holocene peat. The understanding of subsidence in

  6. Late Holocene tectonic implications deduced from tidal notches in Leukas and Meganisi islands (Ionian Sea)

    International Nuclear Information System (INIS)

    Evelpidou, N.; Karkani, A.; Pirazzoli, P.

    2017-01-01

    In this paper the tectonic behavior of Leukas and Meganisi islands (Ionian Sea) is examined through underwater research carried out in both islands. A possible Late Holocene correlation between coseismic subsidences is attempted and evidenced by submerged tidal notches in both islands. These subsidence events probably occurred after the uplift that affected the northernmost part of Leukas around 4 to 5ka BP. In conclusion, although the whole area was affected by a similar tectonic strain, certain coseismic events were only recorded in one of the two islands and in some cases they affected only part of the study area.

  7. Late Holocene tectonic implications deduced from tidal notches in Leukas and Meganisi islands (Ionian Sea)

    Energy Technology Data Exchange (ETDEWEB)

    Evelpidou, N.; Karkani, A.; Pirazzoli, P.

    2017-11-01

    In this paper the tectonic behavior of Leukas and Meganisi islands (Ionian Sea) is examined through underwater research carried out in both islands. A possible Late Holocene correlation between coseismic subsidences is attempted and evidenced by submerged tidal notches in both islands. These subsidence events probably occurred after the uplift that affected the northernmost part of Leukas around 4 to 5ka BP. In conclusion, although the whole area was affected by a similar tectonic strain, certain coseismic events were only recorded in one of the two islands and in some cases they affected only part of the study area.

  8. Tropical Peat and Peatland Development in the Floodplains of the Greater Pamba Basin, South-Western India during the Holocene.

    Science.gov (United States)

    Kumaran, Navnith K P; Padmalal, Damodaran; Limaye, Ruta B; S, Vishnu Mohan; Jennerjahn, Tim; Gamre, Pradeep G

    2016-01-01

    Holocene sequences in the humid tropical region of Kerala, South-western (SW) India have preserved abundance of organic-rich sediments in the form of peat and its rapid development in a narrow time frame towards Middle Holocene has been found to be significant. The sub-coastal areas and flood plains of the Greater Pamba Basin have provided palaeorecords of peat indicating that the deposits are essentially formed within freshwater. The combination of factors like stabilized sea level and its subsequent fall since the Middle Holocene, topographic relief and climatic conditions led to rapid peat accumulation across the coastal lowlands. The high rainfall and massive floods coupled with a rising sea level must have inundated > 75% of the coastal plain land converting it into a veritable lagoon-lake system that eventually led to abrupt termination of the forest ecosystem and also converted the floodplains into peatland where accumulation of peat almost to 2.0-3.0 m thickness in coastal lowlands and river basins during the shorter interval in the Middle Holocene. Vast areas of the coastal plains of Kerala have been converted into carbon rich peatland during the Middle Holocene and transforming the entire coastal stretch and associated landforms as one of the relatively youngest peatlands in the extreme southern tip of India. Unlike the uninterrupted formation of peatlands of considerable extent during the Holocene in Southeast Asia, the south Peninsular Indian region has restricted and short intervals of peatlands in the floodplains and coastal lowlands. Such a scenario is attributed to the topographic relief of the terrain and the prevailing hydrological regimes and environmental conditions as a consequence of monsoon variability since Middle Holocene in SW India. Considering the tropical coastal lowlands and associated peatlands are excellent repositories of carbon, they are very important for regional carbon cycling and habitat diversity. The alarming rate of land

  9. Tropical Peat and Peatland Development in the Floodplains of the Greater Pamba Basin, South-Western India during the Holocene.

    Directory of Open Access Journals (Sweden)

    Navnith K P Kumaran

    Full Text Available Holocene sequences in the humid tropical region of Kerala, South-western (SW India have preserved abundance of organic-rich sediments in the form of peat and its rapid development in a narrow time frame towards Middle Holocene has been found to be significant. The sub-coastal areas and flood plains of the Greater Pamba Basin have provided palaeorecords of peat indicating that the deposits are essentially formed within freshwater. The combination of factors like stabilized sea level and its subsequent fall since the Middle Holocene, topographic relief and climatic conditions led to rapid peat accumulation across the coastal lowlands. The high rainfall and massive floods coupled with a rising sea level must have inundated > 75% of the coastal plain land converting it into a veritable lagoon-lake system that eventually led to abrupt termination of the forest ecosystem and also converted the floodplains into peatland where accumulation of peat almost to 2.0-3.0 m thickness in coastal lowlands and river basins during the shorter interval in the Middle Holocene. Vast areas of the coastal plains of Kerala have been converted into carbon rich peatland during the Middle Holocene and transforming the entire coastal stretch and associated landforms as one of the relatively youngest peatlands in the extreme southern tip of India. Unlike the uninterrupted formation of peatlands of considerable extent during the Holocene in Southeast Asia, the south Peninsular Indian region has restricted and short intervals of peatlands in the floodplains and coastal lowlands. Such a scenario is attributed to the topographic relief of the terrain and the prevailing hydrological regimes and environmental conditions as a consequence of monsoon variability since Middle Holocene in SW India. Considering the tropical coastal lowlands and associated peatlands are excellent repositories of carbon, they are very important for regional carbon cycling and habitat diversity. The

  10. Land Sea Level Difference Impacts on Socio-Hydrological System.

    Science.gov (United States)

    Sung, K.; Yu, D. J.; Oh, W. S.; Sangwan, N.

    2016-12-01

    Allowing moderate shocks can be a new solution that helps to build adaptive capacity in society is a rising issue. In Social-Ecological field, Carpenter et al. (2015) suggested that exposure to short-term variability leads to long term resilience by enlarging safe operating space (SOS). The SOS refers to the boundary of favorable state that ecosystem can maintain resilience without imposing certain conditions (Carpenter et al. 2015). Our work is motivated by defining SOS in socio-hydrological system(SHS) because it can be an alternative way for flood management beyond optimized or robust flood control. In this context, large flood events that make system to cross the SOS should be fully managed, but frequent small floods need to be allowed if the system is located in SOS. Especially, land sea level change is critical factor to change flood resilience since it is one of the most substantial disturbance that changes the entire boundary of SOS. In order to have broader perspective of vulnerability and resilience of the coastal region, it is crucial to understand the land sea level dynamics changed with human activities and natural variances.The risk of land sea level change has been researched , but most of these researches have focused on explain cause and effect of land sea level change, paying little attention to its dynamics interacts with human activities. Thus, an objective of this research is to study dynamics of human work, land sea level change and resilience to flood with SOS approach. Especially, we focus on the case in Ganges-Brahmaputra, Bangladesh where has high vulnerability to flood, and is faced with relatively rapid land sea level change problem. To acheive the goal, this study will develop a stylized model by extending the human - flood interaction model combined with relative sea level difference equation. The model describes the dynamics of flood protection system which is changed by SHS and land sea level chage. we will focus on the aggradation

  11. Anthropogenic forcing dominates sea level rise since 1850

    DEFF Research Database (Denmark)

    Jevrejeva, Svetlana; Grinsted, Aslak; Moore, John

    2009-01-01

    The rate of sea level rise and its causes are topics of active debate. Here we use a delayed response statistical model to attribute the past 1000 years of sea level variability to various natural (volcanic and solar radiative) and anthropogenic (greenhouse gases and aerosols) forcings. We show...... that until 1800 the main drivers of sea level change are volcanic and solar radiative forcings. For the past 200 years sea level rise is mostly associated with anthropogenic factors. Only 4 ± 1.5 cm (25% of total sea level rise) during the 20th century is attributed to natural forcings, the remaining 14 ± 1...

  12. SEA-LEVEL RISE. Sea-level rise due to polar ice-sheet mass loss during past warm periods.

    Science.gov (United States)

    Dutton, A; Carlson, A E; Long, A J; Milne, G A; Clark, P U; DeConto, R; Horton, B P; Rahmstorf, S; Raymo, M E

    2015-07-10

    Interdisciplinary studies of geologic archives have ushered in a new era of deciphering magnitudes, rates, and sources of sea-level rise from polar ice-sheet loss during past warm periods. Accounting for glacial isostatic processes helps to reconcile spatial variability in peak sea level during marine isotope stages 5e and 11, when the global mean reached 6 to 9 meters and 6 to 13 meters higher than present, respectively. Dynamic topography introduces large uncertainties on longer time scales, precluding robust sea-level estimates for intervals such as the Pliocene. Present climate is warming to a level associated with significant polar ice-sheet loss in the past. Here, we outline advances and challenges involved in constraining ice-sheet sensitivity to climate change with use of paleo-sea level records. Copyright © 2015, American Association for the Advancement of Science.

  13. 8000 years of coastal changes on a western Mediterranean island: A multiproxy approach from the Posada plain of Sardinia

    DEFF Research Database (Denmark)

    Melis, Rita T.; Di Rita, Federico; French, Charles

    2018-01-01

    -stratigraphy exhibited by a series of new cores taken from the coastal plain. This new study elucidates the main paleoecological changes, phases of shoreline migration and relative sea-level change during the last 8000 years. These results indicate the major role of sea-level stabilization and high sediment supply...... in driving major landscape changes, especially during the Neolithic period (6th–4th millennia BC), and the long-term settlement history of this coastal valley area. It is concluded that human occupation of the coastal plain, from prehistoric to historical times, was most likely constrained by the rapid......A multi-proxy palaeoenvironmental investigation was conducted to reconstruct the Holocene history of coastal landscape change in the lower Posada coastal plain of eastern Sardinia. In the Mediterranean region, coastal modifications during the Holocene have been driven by a complex interplay between...

  14. Reconstructing Common Era relative sea-level change on the Gulf Coast of Florida

    Science.gov (United States)

    Gerlach, Matthew J.; Engelhart, Simon E.; Kemp, Andrew C.; Moyer, Ryan P.; Smoak, Joseph M.; Bernhardt, Christopher E.; Cahill, Niamh

    2017-01-01

    indicate that no significant Common Era sea-level changes took place on the Gulf and southeastern Atlantic U.S. coasts until the onset of modern sea-level rise in the late 19th century.

  15. The Influence of Wind and Basin Eddies in Controlling Sea Level Variations in the Coastal Red Sea

    KAUST Repository

    Abualnaja, Yasser

    2015-04-01

    Sea level variations in the central Red Sea coastal zone span a range of roughly 1.2 m. Though relatively small, these water level changes can significantly impact the environment over the shallow reef tops prevalent in the central Red Sea, altering the water depth by a factor or two or more. Roughly half of the coastal sea level variance in central Red Sea is due to elevation changes in an \\'intermediate\\' frequency band, with periods between 2 days and 1 month. We examined the sea level signal in this band using the data from pressure sensors maintained for more than five years at a number of locations in Saudi Arabian coastal waters between 20.1 and 23.5 oN. We find that the intermediate-band sea level variations are strongly correlated with the local wind stress measured at a meteorological buoy. The maximum pressure-wind correlation occurs at wind direction closely aligned with the alongshore orientation and at a lag (wind leading) of 45 hr, which is consistent with the expected response of the coastal sea level to local wind forcing. However, less than half of the sea level variance in the intermediate band is related, through linear correlation, with local wind forcing. Our analysis indicates that the residual coastal sea level signal, not associated with wind forcing, is largely driven remotely by the passage of mesoscale eddies, revealed by satellite altimeter-derived sea level anomaly fields of the central Red Sea. These eddy-driven coastal sea level changes occur on time scales of 10-30 days. They span a range of 0.5 m, and thus constitute an import component of the sea level signal in the coastal Red Sea.

  16. The Influence of Wind and Basin Eddies in Controlling Sea Level Variations in the Coastal Red Sea

    KAUST Repository

    Abualnaja, Yasser; Churchill, James H.; Nellayaputhenpeedika, Mohammedali; Limeburner, Richard

    2015-01-01

    Sea level variations in the central Red Sea coastal zone span a range of roughly 1.2 m. Though relatively small, these water level changes can significantly impact the environment over the shallow reef tops prevalent in the central Red Sea, altering the water depth by a factor or two or more. Roughly half of the coastal sea level variance in central Red Sea is due to elevation changes in an 'intermediate' frequency band, with periods between 2 days and 1 month. We examined the sea level signal in this band using the data from pressure sensors maintained for more than five years at a number of locations in Saudi Arabian coastal waters between 20.1 and 23.5 oN. We find that the intermediate-band sea level variations are strongly correlated with the local wind stress measured at a meteorological buoy. The maximum pressure-wind correlation occurs at wind direction closely aligned with the alongshore orientation and at a lag (wind leading) of 45 hr, which is consistent with the expected response of the coastal sea level to local wind forcing. However, less than half of the sea level variance in the intermediate band is related, through linear correlation, with local wind forcing. Our analysis indicates that the residual coastal sea level signal, not associated with wind forcing, is largely driven remotely by the passage of mesoscale eddies, revealed by satellite altimeter-derived sea level anomaly fields of the central Red Sea. These eddy-driven coastal sea level changes occur on time scales of 10-30 days. They span a range of 0.5 m, and thus constitute an import component of the sea level signal in the coastal Red Sea.

  17. Non-eustatic controls on sea-level change in semi-enclosed basins

    Science.gov (United States)

    Major, Candace Olson

    Marginal basins with shallow connections to the world ocean can become isolated from marine influence when eustatic sea level drops below the dividing sill. During isolation the basins may have higher or lower base-levels than the open ocean. This decoupling from global sea level and seawater allows preservation of a distinct history that constrains water balance and erosion in the surrounding continental masses, providing records of continental climates not preserved in marine records. The Mediterranean and Black Seas both experienced isolation stages and significant draw down of base-level below the dividing sill depth. In the Late Miocene (Messinian) a combination of tectonic compression at the marine gateways and eustatic sea level drop isolated the Mediterranean. A negative water balance then caused a lowering of Mediterranean base-level by at least 1500 m, exposing the continental shelves and slopes, and allowing the emergence of bathymetric highs in the central basins. Subaerial exposure features on the summit and evaporite onlap at the base of the Eratosthenes seamount, a carbonate platform in the Levantine basin of the Mediterranean, show the extent of base-level lowering. The Black Sea has periodically become isolated during glacio-eustatic low stands of the Pleistocene. Submerged shoreline deposits and beveled strata during the last isolation exposed the continental shelves out to -105 m below modern sea level. Integration of seismic data, sediment cores, radiocarbon dating, and geochemical analyses indicates that the lowest water level occurred not during the glacial maximum but during the early deglaciation. A brief return toward glacial conditions in the Younger Dryas cold period resulted in increased freshwater input to the Black Sea and a rise in base-level above the outside eustatic level. Subsequent base-level fall to -105 m occurred with resumed warming climate. The first marine invasion, which is seen prominently in the 87Sr/86Sr composition of

  18. Sea Level Activities and Changes on the Islands of the Western ...

    African Journals Online (AJOL)

    1985- 1994), a sea-level study network was established in the Western Indian Ocean (WIO) to monitor sea-level variations. Most of these stations together with additional stations maintained by countries outside the region now form part of the ...

  19. Patagonian and southern South Atlantic view of Holocene climate

    Science.gov (United States)

    Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Denton, G. H.; Anderson, R. F.; Vandergoes, M. J.; Finkel, R. C.; Schwartz, R.; Travis, S. G.; Garcia, J. L.; Martini, M. A.; Nielsen, S. H. H.

    2016-06-01

    We present a comprehensive 10Be chronology for Holocene moraines in the Lago Argentino basin, on the east side of the South Patagonian Icefield. We focus on three different areas, where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change. The 10Be dated records are from the Lago Pearson, Herminita Península-Brazo Upsala, and Lago Frías areas, which span a distance of almost 100 km adjacent to the modern Icefield. New 10Be ages show that expanded glaciers and moraine building events occurred at least at 6120 ± 390 (n = 13), 4450 ± 220 (n = 7), 1450 or 1410 ± 110 (n = 18), 360 ± 30 (n = 5), and 240 ± 20 (n = 8) years ago. Furthermore, other less well-dated glacier expansions of the Upsala Glacier occurred between 1400 and ∼1000 and ∼2300 and ∼2000 years ago. The most extensive glaciers occurred over the interval from ∼6100 to ∼4500 years ago, and their margins over the last ∼600 years were well within and lower than those in the middle Holocene. The 10Be ages agree with 14C-limiting data for the glacier histories in this area. We then link southern South American, adjacent South Atlantic, and other Southern Hemisphere records to elucidate broader regional patterns of climate and their possible causes. In the early Holocene, a far southward position of the westerly winds fostered warmth, small Patagonian glaciers, and reduced sea ice coverage over the South Atlantic. Although we infer a pronounced southward displacement of the westerlies during the early Holocene, these conditions did not occur throughout the southern mid-high latitudes, an important exception being over the southwest Pacific sector. Subsequently, a northward locus and/or expansion of the winds over the Patagonia-South Atlantic sector promoted the largest glaciers between ∼6100 and ∼4500 years ago and greatest sea ice coverage. Over the last few millennia, the South Patagonian Icefield has experienced

  20. Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

    Science.gov (United States)

    Mallinson, D.; Burdette, K.; Mahan, S.; Brook, G.

    2008-01-01

    Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2??ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26??m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2??ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism. ?? 2007 University of Washington.

  1. Coastal vertebrate exposure to predicted habitat changes due to sea level rise

    Science.gov (United States)

    Hunter, Elizabeth A.; Nibbelink, Nathan P.; Alexander, Clark R.; Barrett, Kyle; Mengak, Lara F.; Guy, Rachel; Moore, Clinton; Cooper, Robert J.

    2015-01-01

    Sea level rise (SLR) may degrade habitat for coastal vertebrates in the Southeastern United States, but it is unclear which groups or species will be most exposed to habitat changes. We assessed 28 coastal Georgia vertebrate species for their exposure to potential habitat changes due to SLR using output from the Sea Level Affecting Marshes Model and information on the species’ fundamental niches. We assessed forecasted habitat change up to the year 2100 using three structural habitat metrics: total area, patch size, and habitat permanence. Almost all of the species (n = 24) experienced negative habitat changes due to SLR as measured by at least one of the metrics. Salt marsh and ocean beach habitats experienced the most change (out of 16 categorical land cover types) across the three metrics and species that used salt marsh extensively (rails and marsh sparrows) were ranked highest for exposure to habitat changes. Species that nested on ocean beaches (Diamondback Terrapins, shorebirds, and terns) were also ranked highly, but their use of other foraging habitats reduced their overall exposure. Future studies on potential effects of SLR on vertebrates in southeastern coastal ecosystems should focus on the relative importance of different habitat types to these species’ foraging and nesting requirements. Our straightforward prioritization approach is applicable to other coastal systems and can provide insight to managers on which species to focus resources, what components of their habitats need to be protected, and which locations in the study area will provide habitat refuges in the face of SLR.

  2. The land-ice contribution to 21st-century dynamic sea level rise

    Science.gov (United States)

    Howard, T.; Ridley, J.; Pardaens, A. K.; Hurkmans, R. T. W. L.; Payne, A. J.; Giesen, R. H.; Lowe, J. A.; Bamber, J. L.; Edwards, T. L.; Oerlemans, J.

    2014-06-01

    Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere-ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

  3. Climate related sea-level variations over the past two millennia.

    Science.gov (United States)

    Kemp, Andrew C; Horton, Benjamin P; Donnelly, Jeffrey P; Mann, Michael E; Vermeer, Martin; Rahmstorf, Stefan

    2011-07-05

    We present new sea-level reconstructions for the past 2100 y based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment. Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/y, representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semiempirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium.

  4. On the Application of an Enthalpy Method to the Evolution of Fluvial Deltas Under Sea-Level Changes

    Science.gov (United States)

    Anderson, W.; Lorenzo-Trueba, J.; Voller, V. R.

    2017-12-01

    Fluvial deltas are composites of two primary sedimentary environments: a depositional fluvial region and an offshore region. The fluvial region is defined by two geomorphic moving boundaries: an alluvial-bedrock transition (ABT), which separates the sediment prism from the non-erodible bedrock basement, and the shoreline (SH), where the delta meets the ocean. The trajectories of these boundaries in time and space define the evolution of the shape of the sedimentary prism, and are often used as stratigraphic indicators, particularly in seismic studies, of changes in relative sea level and the identification of stratigraphic sequences. In order to better understand the relative role of sea-level variations, tectonics, and sediment supply on the evolution of these boundaries, we develop a forward stratigraphic model that captures the dynamic behavior of the fluvial surface and treats the SH and ABT as moving boundaries (i.e., internal boundaries whose location must be determined as part of the solution to the overall morphological evolution problem). This forward model extends a numerical technique from heat transfer (i.e., enthalpy method), previously applied to the evolution of sedimentary basins, to account for sea-level changes. The mathematics of the approach are verified by comparing predictions from the numerical model with both existing and newly developed closed form analytical solutions. Model results support previous work, which suggests that the migration of the ABT can respond very differently to the sea-level signal. This response depends on factors such as sediment supply and delta length, which can vary greatly between basins. These results can have important implications for the reconstruction of past sea-level changes from the stratigraphic record of sedimentary basins.

  5. Perceptions of Climate Change, Sea Level Rise, and Possible Consequences Relate Mainly to Self-Valuation of Science Knowledge.

    Science.gov (United States)

    Burger, Joanna; Gochfeld, Michael; Pittfield, Taryn; Jeitner, Christian

    2016-05-01

    This study examines perceptions of climate change and sea level rise in New Jersey residents in 2012 and 2014. Different surveys have shown declines in interest and concern about climate change and sea level rise. Climate change and increasing temperatures have an anthropogenic cause, which relates to energy use, making it important to examine whether people believe that it is occurring. In late 2012 New Jersey experienced Super storm Sandy, one of the worst hurricanes in its history, followed by public discussion and media coverage of stronger more frequent storms due to climate change. Using structured interviews, we tested the null hypotheses that there were no differences in perceptions of 1260 interviewees as a function of year of the survey, age, gender, years of education, and self-evaluation of science knowledge (on a scale of 1 to 5). In 2012 460 of 639 (72%) rated "global warming occurring" as "certain" (#4) or "very certain" (#5) compared with 453 of 621 (73%) in 2014. For "due to human activities" the numbers of "certain" or "very certain" were 71% in 2012, and 67% in 2014 and for sea level rise the numbers were 64% and 70%. There were some inconsistent between-year differences with higher ratings in 2012 for 3 outcomes and higher ratings in 2014 for 5 outcomes. However, for 25 questions relative to climate change, sea level rise, and the personal and ecological effects of sea level rise, self-evaluation of science knowledge, independent of years of education, was the factor that entered 23 of the models, accounting for the most variability in ratings. People who believed they had a "high knowledge" (#4) or "very high knowledge" (#5) of science rated all issues as more important than did those people who rated their own scientific knowledge as average or below average.

  6. Holocene geologic and climatic history around the Gulf of Alaska

    Science.gov (United States)

    Mann, D.H.; Crowell, A.L.; Hamilton, T.D.; Finney, B.P.

    1998-01-01

    Though not as dramatic as during the last Ice Age, pronounced climatic changes occurred in the northeastern Pacific over the last 10,000 years. Summers warmer and drier than today's accompanied a Hypsithermal interval between 9 and 6 ka. Subsequent Neoglaciation was marked by glacier expansion after 5-6 ka and the assembly of modern-type plant communities by 3-4 ka. The Neoglacial interval contained alternating cold and warm intervals, each lasting several hundred years to one millennium, and including both the Medieval Warm Period (ca. AD 900-1350) and the Little Ice Age (ca. AD 1350-1900). Salmon abundance fluctuated during the Little Ice Age in response to local glaciation and probably also to changes in the intensity of the Aleutian Low. Although poorly understood at present, climate fluctuations at all time scales were intimately connected with oceanographic changes in the North Pacific Ocean. The Gulf of Alaska region is tectonically highly active, resulting in a history of frequent geological catastrophes during the Holocene. Twelve to 14 major volcanic eruptions occurred since 12 ka. At intervals of 20-100 years, large earthquakes have raised and lowered sea level instantaneously by meters and generated destructive tsunamis. Sea level has often varied markedly between sites only 50-100 km apart due to tectonism and the isostatic effects of glacier fluctuations.

  7. Holocene changes in climate and vegetation in the Ammassalik area, East Greenland, recorded in lake sediments and soil profiles

    DEFF Research Database (Denmark)

    Jakobsen, Bjarne Holm; Fredskild, Bent; Pedersen, Jørn Bjarke Torp

    2008-01-01

    , appears to have experienced the warmest Holocene summer conditions, ice-free seas and limited snow covers. The climate situation seems to have been to a considerable extent based on internal regional meteorological processes and largely without strong and regular cyclonic impacts from lower latitudes...

  8. Integrative study of the mean sea level and its components

    CERN Document Server

    Champollion, Nicolas; Paul, Frank; Benveniste, Jérôme

    2017-01-01

    This volume presents the most recent results of global mean sea level variations over the satellite altimetry era (starting in the early 1990s) and associated contributions, such as glaciers and ice sheets mass loss, ocean thermal expansion, and land water storage changes. Sea level is one of the best indicators of global climate changes as it integrates the response of several components of the climate system to external forcing factors (including anthropogenic forcing) and internal climate variability. Providing long, accurate records of the sea level at global and regional scales and of the various components causing sea level changes is of crucial importance to improve our understanding of climate processes at work and to validate the climate models used for future projections. The Climate Change Initiative project of the European Space Agency has provided a first attempt to produce consistent and continuous space-based records for several climate parameters observable from space, among them sea level. Th...

  9. XXI century projections of wind-wave conditions and sea-level rise in the Black sea

    Science.gov (United States)

    Polonsky, A.; Garmashov, A.; Fomin, V.; Valchev, N.; Trifonova, E.

    2012-04-01

    Projection of regional climate changes for XXI century is one of the priorities of EC environmental programme. Potential worsening of the waves' statistics, sea level rise and extreme surges are the principal negative consequences of the climate change for marine environment. That is why the main purpose of this presentation is to discuss the above issue for the Black sea region (with a strong focus to the south-west subregion because the maximum heights of waves exceeding 10 m occur just here) using output of several global coupled models (GCM) for XXI century, wave simulation, long-term observations of sea level and statistical techniques. First of all we tried to choose the best coupled model (s) simulated the Black sea climate change and variability using the control experiments for 20 century (203). The principal result is as follows. There is not one model which is simulating adequately even one atmospheric parameter for all seasons. Therefore we considered (for the climate projection) different outputs form various models. When it was possible we calculated also the ensemble mean projection for the selected model (s) and emission scenarios. To calculate the wave projection we used the output of SWAN model forced by the GCM wind projection for 2010 to 2100. To estimate the sea level rise in XXI century and future surges statistics we extrapolate the observed sea level rise tendencies, statistical relation between wave heights and sea level and wave scenarios. Results show that in general, the climate change in XXI century doesn't lead to the catastrophic change of the Black sea wind-wave statistics including the extreme waves in the S-W Black sea. The typical atmospheric pattern leading to the intense storm in the S-W Black sea is characterized by the persistent anticyclonic area to the North of the Black sea and cyclonic conditions in the Southern Black sea region. Such pressure pattern causes persistent and strong eastern or north-eastern wind which

  10. Short communication: Massive erosion in monsoonal central India linked to late Holocene land cover degradation

    Directory of Open Access Journals (Sweden)

    L. Giosan

    2017-12-01

    Full Text Available Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.

  11. Short communication: Massive erosion in monsoonal central India linked to late Holocene land cover degradation

    Science.gov (United States)

    Giosan, Liviu; Ponton, Camilo; Usman, Muhammed; Blusztajn, Jerzy; Fuller, Dorian Q.; Galy, Valier; Haghipour, Negar; Johnson, Joel E.; McIntyre, Cameron; Wacker, Lukas; Eglinton, Timothy I.

    2017-12-01

    Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.

  12. The sea-level budget along the Northwest Atlantic coast : GIA, mass changes, and large-scale ocean dynamics

    NARCIS (Netherlands)

    Frederikse, T.; Simon, K.M.; Katsman, C.A.; Riva, R.E.M.

    2017-01-01

    Sea-level rise and decadal variability along the northwestern coast of the North Atlantic Ocean are studied in a self-consistent framework that takes into account the effects of solid-earth deformation and geoid changes due to large-scale mass redistribution processes. Observations of sea and

  13. Assessment of the impact of sea-level rise due to climate change on coastal groundwater discharge.

    Science.gov (United States)

    Masciopinto, Costantino; Liso, Isabella Serena

    2016-11-01

    An assessment of sea intrusion into coastal aquifers as a consequence of local sea-level rise (LSLR) due to climate change was carried out at Murgia and Salento in southern Italy. The interpolation of sea-level measurements at three tide-gauge stations was performed during the period of 2000 to 2014. The best fit of measurements shows an increasing rate of LSLR ranging from 4.4mm/y to 8.8mm/y, which will result in a maximum LSLR of approximately 2m during the 22nd century. The local rate of sea-level rise matches recent 21st and 22nd century projections of mean global sea-level rise determined by other researchers, which include increased melting rates of the Greenland and Antarctic ice sheets, the effect of ocean thermal expansion, the melting of glaciers and ice caps, and changes in the quantity of stored land water. Subsequently, Ghyben-Herzberg's equation for the freshwater/saltwater interface was rewritten in order to determine the decrease in groundwater discharge due to the maximum LSLR. Groundwater flow simulations and ArcGIS elaborations of digital elevation models of the coast provided input data for the Ghyben-Herzberg calculation under the assumption of head-controlled systems. The progression of seawater intrusion due to LSLR suggests an impressive depletion of available groundwater discharge during the 22nd century, perhaps as much as 16.1% of current groundwater pumping for potable water in Salento. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmos- phere in the Okinawa Trough during the Holocene and their paleoclimatic implications

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G. Sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed. Consequently, three cooling events (E1-E3) were identified, each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4 kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.

  15. The relationship between Holocene cultural site distribution and marine terrace uplift on the coast fringing Coastal Range, Taiwan

    Science.gov (United States)

    Yang, Hsiaochin; Chen, Wenshan

    2013-04-01

    According to the collision of Philippine Sea plate and Eurasia plate, a series of left-lateral active faults with reverse sense exists in the Longitudinal Valley of east Taiwan. The Holocene marine terraces along the east coast of the Coastal Range in Taiwan are well known for their very rapid uplift and record tectonic history of this active collision boundary. The Holocene marine terrace sequence resulting from successive sea level change and tectonic activation is subdivided into several steps where the highest and oldest terrace, back to ca 13,000yr BP, reaches up to ca 80 m above sea level, and the lower terraces are mostly erosional ones, overlain by less than 1m thick coral beds in situ. The uplift of the coast is very high, ranging from 5 to 10 m/ka. According to the fabrics of potsherds and geochronological data, the prehistoric cultures in eastern Taiwan could be classified into three stages: Fushan (ca 5000-3500yr BP), Peinan/Chilin (ca3500-2000yr BP), Kweishan (ca2000-1000 yr BP) and Jinpu (ca 1000-400yr BP) cultural assemblages respectively. A great difference exists between the various cultural stage, not only the pottery making techniques, but also the distributions of archaeological sites. Combined with the dynamic geomorphic evolution of marine terraces and the distribution of prehistoric culture sites on the east coast of the Coastal Range, a coastal migration trend could be established.

  16. Climate And Sea Level: It's In Our Hands Now

    Science.gov (United States)

    Turrin, M.; Bell, R. E.; Ryan, W. B. F.

    2014-12-01

    Changes in sea level are measurable on both a local and a global scale providing an accessible way to connect climate to education, yet engaging teachers and students with the complex science that is behind the change in sea level can be a challenge. Deciding how much should be included and just how it should be introduced in any single classroom subject area can be an obstacle for a teacher. The Sea Level Rise Polar Explorer App developed through the PoLAR CCEP grant offers a guided tour through the many layers of science that impact sea level rise. This map-based data-rich app is framed around a series of questions that move the user through map layers with just the level of complexity they chose to explore. For a quick look teachers and students can review a 3 or 4 sentence introduction on how the given map links to sea level and then launch straight into the interactive touchable map. For a little more in depth look they can listen to (or read) a one-minute recorded background on the data displayed in the map prior to launching in. For those who want more in depth understanding they can click to a one page background piece on the topic with links to further visualizations, videos and data. Regardless of the level of complexity selected each map is composed of clickable data allowing the user to fully explore the science. The different options for diving in allow teachers to differentiate the learning for either the subject being taught or the user level of the student group. The map layers also include a range of complexities. Basic questions like "What is sea level?" talk about shorelines, past sea levels and elevations beneath the sea. Questions like "Why does sea level change?" includes slightly more complex issues like the role of ocean temperature, and how that differs from ocean heat content. And what is the role of the warming atmosphere in sea level change? Questions about "What about sea level in the past?" can bring challenges for students who have

  17. Causes and consequences of short-term sea-level changes in the Cretaceous green- and "hothouse": Topics and context of IGCP Project 609

    Science.gov (United States)

    Sames, Benjamin; Wagreich, Michael

    2015-04-01

    In contrast to the well-understood process of glacial eustasy, controlled mainly by waxing and waning of continental ice sheets, significant short-term, i.e. 10s kyr to a few myr (3rd to 4th order cycles) sea-level changes during the Cretaceous major greenhouse episode remain enigmatic. Such cyclic changes are often explained by the presence of ephemeral ice sheets even during the hottest greenhouse phases ("hothouse periods"), such as the mid-Cretaceous. Though Cretaceous global eustasy involves processes like brief glacial episodes (glacio-eustasy) for which evidence was given - at least for the Early Cretaceous and the late Late Cretaceous - other mechanisms have to be taken into consideration for the "hothouse periods" during which continental ice shields are highly improbable, like the storage and release of groundwater (termed "limno-eustasy" or "aquifer-eustasy"), the possible effect and magnitude of which might have been highly underestimated. Investigation of the timing, the causes, and the consequences of significant short-term (i.e. mainly kyr to 100s of kyr) sea-level changes during the last major greenhouse episode of Earth history, the Cretaceous, is the ultimate goal of the UNESCO IGCP (International Geoscience Programme) project number 609 "Climate-environmental deteriorations during greenhouse phases: Causes and consequences of short-term Cretaceous sea-level changes" (2013-2017; http://www.univie.ac.at/igcp609/). This also comprises the global versus regional correlation and extent of the sequences, their cyclicities, as well as the processes and triggering mechanisms for these, and marine to non-marine correlations. Recent refinements of the geological time scale have made major advances for the Cretaceous to yield a resolution comparable to that of younger Earth history. It is now for the first time possible to correlate and date short-term Cretaceous sea-level records with a resolution appropriate for their detailed analysis. Recognized

  18. Conference on Continental margin mass wasting and Pleistocene sea-level changes, August 13-15, 1980

    Science.gov (United States)

    Folger, David W.; Hathaway, J.C.

    1987-01-01

    A conference on Continental Margin Mass Wasting and Pleistocene Sea-Level Changes was held in Woods Hole, Mass., August 13-15, 1980. Forty-seven participants, representing many government, academic, and industrial organizations, discussed the current state of knowledge of the features of marine mass wasting and of the interrelations of factors influencing them. These factors include sediment source, composition, textures, sedimentation rates, climatic and sea-level changes, gas and gas hydrate (clathrate) contents of sediments, geotechnical characteristics, oceanographic and morphological factors, ground-water processes, and seismic events. The part played by these factors in the processes and features of mass movement and the engineering considerations imposed by the emplacement of manmade structures on the sea floor were considered vital to the evaluation of hazards involved in offshore exploration and development. The conference concluded with a call for bold programs to establish the probability of occurrence and the quantitative importance of these factors and to devise more reliable means of measurement, particularly in place, of the characteristics of the sediment and features involved.

  19. Evidence for Isostatic Emergence and Holocene Environmental Change Recorded in Chironomid Assemblages and Sediment Composition of Coastal Lake T1 in SW Greenland

    Science.gov (United States)

    Berman, K.; Axford, Y.; Lasher, G. E.

    2017-12-01

    Multi-proxy analysis of a coastal lake in southwest Greenland near Nuuk provides evidence for regional environmental changes, including the timing of isostatic rebound and the temperature history of the area. T1 (informal name) is a small lake 50 km south of Nuuk, at 17.5 m elevation and currently isolated from glacial meltwater drainage. The lake's sediment record begins approximately 9500 cal years BP, when the site was submerged beneath sea level due to glacial isostatic depression following the Last Glacial Maximum. The record captures the transition of the environment from a submerged, glacially-influenced marine site to a non-glacially fed (and initially meromictic) freshwater lake 8600 cal years BP. Magnetic susceptibility, a proxy for sediment minerogenic content, decreased rapidly from 9500 to 8600 years BP, before abruptly stabilizing and remaining relatively low and steady for the rest of the record. The transition to a lacustrine environment was characterized by a rapid and relatively simultaneous increase in primary productivity (inferred from biogenic silica concentrations) and shift towards terrestrial versus marine sources of organic matter (inferred from carbon:nitrogen ratios and nitrogen isotopes) between 8700 and 8400 years BP. Together, these proxies and the presence of marine shells below the transition provide robust evidence for the transition from a marine environment to a freshwater lake in response to regional postglacial isostatic rebound. Within the Holocene, measures of bulk sediment composition (e.g., biogenic silica, loss-on-ignition and magnetic susceptibility) are relatively stable. Chironomid (Insecta: Diptera: Chironomidae) assemblages, which in some environments are quantitative proxies for summer temperature changes, show species-level shifts within the Holocene that will be interpreted in this presentation alongside indicators of landscape change including carbon:nitrogen ratios, bulk sediment spectral reflectance and bulk

  20. Variability of East Asian summer monsoon precipitation during the Holocene and possible forcing mechanisms

    Science.gov (United States)

    Lu, Fuzhi; Ma, Chunmei; Zhu, Cheng; Lu, Huayu; Zhang, Xiaojian; Huang, Kangyou; Guo, Tianhong; Li, Kaifeng; Li, Lan; Li, Bing; Zhang, Wenqing

    2018-03-01

    Projecting how the East Asian summer monsoon (EASM) rainfall will change with global warming is essential for human sustainability. Reconstructing Holocene climate can provide critical insight into its forcing and future variability. However, quantitative reconstructions of Holocene summer precipitation are lacking for tropical and subtropical China, which is the core region of the EASM influence. Here we present high-resolution annual and summer rainfall reconstructions covering the whole Holocene based on the pollen record at Xinjie site from the lower Yangtze region. Summer rainfall was less seasonal and 30% higher than modern values at 10-6 cal kyr BP and gradually declined thereafter, which broadly followed the Northern Hemisphere summer insolation. Over the last two millennia, however, the summer rainfall has deviated from the downward trend of summer insolation. We argue that greenhouse gas forcing might have offset summer insolation forcing and contributed to the late Holocene rainfall anomaly, which is supported by the TraCE-21 ka transient simulation. Besides, tropical sea-surface temperatures could modulate summer rainfall by affecting evaporation of seawater. The rainfall pattern concurs with stalagmite and other proxy records from southern China but differs from mid-Holocene rainfall maximum recorded in arid/semiarid northern China. Summer rainfall in northern China was strongly suppressed by high-northern-latitude ice volume forcing during the early Holocene in spite of high summer insolation. In addition, the El Niño/Southern Oscillation might be responsible for droughts of northern China and floods of southern China during the late Holocene. Furthermore, quantitative rainfall reconstructions indicate that the Paleoclimate Modeling Intercomparison Project (PMIP) simulations underestimate the magnitude of Holocene precipitation changes. Our results highlight the spatial and temporal variability of the Holocene EASM precipitation and potential forcing

  1. The response of the southern Greenland ice sheet to the Holocene thermal maximum

    DEFF Research Database (Denmark)

    Larsen, Nicolaj Krog; Kjaer, Kurt H.; Lecavalier, Benoit

    2015-01-01

    contribution of 0.16 m sea-level equivalent from the entire Greenland ice sheet, with a centennial ice loss rate of as much as 100 Gt/yr for several millennia during the Holocene thermal maximum. Our results provide an estimate of the long-term rates of volume loss that can be expected in the future...

  2. Changes in Ocean Circulation with an Ice-Free Arctic: Reconstructing Early Holocene Arctic Ocean Circulation Using Geochemical Signals from Individual Neogloboquadrina pachyderma (sinistral) Shells

    Science.gov (United States)

    Livsey, C.; Spero, H. J.; Kozdon, R.

    2016-12-01

    The impacts of sea ice decrease and consequent hydrologic changes in the Arctic Ocean will be experienced globally as ocean and atmospheric temperatures continue to rise, though it is not evident to what extent. Understanding the structure of the Arctic water column during the early/mid Holocene sea ice minimum ( 6-10 kya), a post-glacial analogue of a seasonally ice-free Arctic, will help us to predict what the changes we can expect as the Earth warms over the next century. Neogloboquadrina pachyderma (sinistral; Nps) is a species of planktonic foraminifera that dominates assemblages in the polar oceans. This species grows its chambers (ontogenetic calcite) in the surface waters and subsequently descends through the water column to below the mixed layer where it quickly adds a thick crust of calcite (Kohfeld et al., 1996). Therefore, geochemical signals from both the surface waters and sub-mixed layer depths are captured within single Nps shells. We were able to target ion mass spectrometry (SIMS), therefore capturing signals from both the ontogenetic and crust calcite in single Nps shells. This data was combined with laser ablation- inductively coupled mass spectrometry (LA-ICPMS) Mg/Ca profiles of trace metals through the two layers of calcite of the same shells, to determine the thermal structure of the water column. Combining δ18O, temperature, and salinity gradients from locations across the Arctic basin allow us to reconstruct the hydrography of the early Holocene Arctic sea ice minimum. These results will be compared with modern Arctic water column characteristics in order to develop a conceptual model of Arctic Ocean oceanographic change due to global warming. Kohfeld, K.E., Fairbanks, R.G., Smith, S.L., Walsh, I.D., 1996. Neogloboquadrina pachyderma(sinistral coiling) as paleoceanographic tracers in polar oceans: Evidence from northeast water polynya plankton tows, sediment traps, and surface sediments. Paleoceanography 11, 679-699.

  3. Improved estimates of global sea level change from Ice Sheets, glaciers and land water storage using GRACE

    Science.gov (United States)

    Velicogna, I.; Hsu, C. W.; Ciraci, E.; Sutterley, T. C.

    2015-12-01

    We use observations of time variable gravity from GRACE to estimate mass changes for the Antarctic and Greenland Ice Sheets, the Glaciers and Ice Caps (GIC) and land water storage for the time period 2002-2015 and evaluate their total contribution to sea level. We calculate regional sea level changes from these present day mass fluxes using an improved scaling factor for the GRACE data that accounts for the spatial and temporal variability of the observed signal. We calculate a separate scaling factor for the annual and the long-term components of the GRACE signal. To estimate the contribution of the GIC, we use a least square mascon approach and we re-analyze recent inventories to optimize the distribution of mascons and recover the GRACE signal more accurately. We find that overall, Greenland controls 43% of the global trend in eustatic sea level rise, 16% for Antarctica and 29% for the GIC. The contribution from the GIC is dominated by the mass loss of the Canadian Arctic Archipelago, followed by Alaska, Patagonia and the High Mountains of Asia. We report a marked increase in mass loss for the Canadian Arctic Archipelago. In Greenland, following the 2012 high summer melt, years 2013 and 2014 have slowed down the increase in mass loss, but our results will be updated with summer 2015 observations at the meeting. In Antarctica, the mass loss is still on the rise with increased contributions from the Amundsen Sea sector and surprisingly from the Wilkes Land sector of East Antarctica, including Victoria Land. Conversely, the Queen Maud Land sector experienced a large snowfall in 2009-2013 and has now resumed to a zero mass gain since 2013. We compare sea level changes from these GRACE derived mass fluxes after including the atmospheric and ocean loading signal with sea level change from satellite radar altimetry (AVISO) corrected for steric signal of the ocean using Argo measurements and find an excellent agreement in amplitude, phase and trend in these estimates

  4. Improved sea level record over the satellite altimetry era (1993-2010) from the Climate Change Initiative project

    DEFF Research Database (Denmark)

    Ablain, M.; Cazenave, A.; Larnicol, G.

    2015-01-01

    .6 and 1-2 mm year(-1)). Similarly, interannual global mean sea level variations (currently uncertain to 2-3 mm) need to be monitored with better accuracy. In this paper, we present various data improvements achieved within the European Space Agency (ESA) Climate Change Initiative (ESA CCI) project on "Sea...

  5. Created mangrove wetlands store belowground carbon and surface elevation change enables them to adjust to sea-level rise

    Science.gov (United States)

    Krauss, Ken W.; Cormier, Nicole; Osland, Michael J.; Kirwan, Matthew L.; Stagg, Camille L.; Nestlerode, Janet A.; Russell, Marc J.; From, Andrew; Spivak, Amanda C.; Dantin, Darrin D.; Harvey, James E.; Almario, Alejandro E.

    2017-01-01

    Mangrove wetlands provide ecosystem services for millions of people, most prominently by providing storm protection, food and fodder. Mangrove wetlands are also valuable ecosystems for promoting carbon (C) sequestration and storage. However, loss of mangrove wetlands and these ecosystem services are a global concern, prompting the restoration and creation of mangrove wetlands as a potential solution. Here, we investigate soil surface elevation change, and its components, in created mangrove wetlands over a 25 year developmental gradient. All created mangrove wetlands were exceeding current relative sea-level rise rates (2.6 mm yr−1), with surface elevation change of 4.2–11.0 mm yr−1 compared with 1.5–7.2 mm yr−1 for nearby reference mangroves. While mangrove wetlands store C persistently in roots/soils, storage capacity is most valuable if maintained with future sea-level rise. Through empirical modeling, we discovered that properly designed creation projects may not only yield enhanced C storage, but also can facilitate wetland persistence perennially under current rates of sea-level rise and, for most sites, for over a century with projected medium accelerations in sea-level rise (IPCC RCP 6.0). Only the fastest projected accelerations in sea-level rise (IPCC RCP 8.5) led to widespread submergence and potential loss of stored C for created mangrove wetlands before 2100.

  6. Created mangrove wetlands store belowground carbon and surface elevation change enables them to adjust to sea-level rise.

    Science.gov (United States)

    Krauss, Ken W; Cormier, Nicole; Osland, Michael J; Kirwan, Matthew L; Stagg, Camille L; Nestlerode, Janet A; Russell, Marc J; From, Andrew S; Spivak, Amanda C; Dantin, Darrin D; Harvey, James E; Almario, Alejandro E

    2017-04-21

    Mangrove wetlands provide ecosystem services for millions of people, most prominently by providing storm protection, food and fodder. Mangrove wetlands are also valuable ecosystems for promoting carbon (C) sequestration and storage. However, loss of mangrove wetlands and these ecosystem services are a global concern, prompting the restoration and creation of mangrove wetlands as a potential solution. Here, we investigate soil surface elevation change, and its components, in created mangrove wetlands over a 25 year developmental gradient. All created mangrove wetlands were exceeding current relative sea-level rise rates (2.6 mm yr -1 ), with surface elevation change of 4.2-11.0 mm yr -1 compared with 1.5-7.2 mm yr -1 for nearby reference mangroves. While mangrove wetlands store C persistently in roots/soils, storage capacity is most valuable if maintained with future sea-level rise. Through empirical modeling, we discovered that properly designed creation projects may not only yield enhanced C storage, but also can facilitate wetland persistence perennially under current rates of sea-level rise and, for most sites, for over a century with projected medium accelerations in sea-level rise (IPCC RCP 6.0). Only the fastest projected accelerations in sea-level rise (IPCC RCP 8.5) led to widespread submergence and potential loss of stored C for created mangrove wetlands before 2100.

  7. Combining Geography, Math, and Science to Teach Climate Change and Sea Level Rise

    Science.gov (United States)

    Oldakowski, Ray; Johnson, Ashley

    2018-01-01

    This study examines the effectiveness of integrating geography into existing math and science curriculum to teach climate change and sea level rise. The desired outcome is to improve student performance in all three subjects. A sample of 120 fifth graders from three schools were taught the integrated curriculum over a period of two to three weeks.…

  8. Vulnerability of marginal seas to sea level rise

    Science.gov (United States)

    Gomis, Damia; Jordà, Gabriel

    2017-04-01

    , Mediterranean Sea level would follow global changes with departures lower than + 5 cm. In a second step we use the same methodology to obtain SLR projections at global scale in order to assess the vulnerability of other coastal areas. Namely, we define a vulnerability index based on relating the characteristics of present day variability with SLR projections under different scenarios. Results show that the averaged vulnerability index is 0.5 for scenario RCP8.5 (projected SLR is about a half of the maximum sea level recorded in the last decades). However, in the Mediterranean, the Caribbean and the Sea of Japan the vulnerability index is much higher (2.6, 2.4 and 2.1, respectively). From this point of view, therefore, these regions could be considered the most vulnerable regions in the world.

  9. Postglacial floodings of the Marmara Sea: molluscs and sediments tell the story

    Science.gov (United States)

    Büyükmeriç, Yeşim

    2016-08-01

    The early Holocene marine flooding of the Black Sea has been the subject of intense scientific debate since the "Noah's Flood" hypothesis was proposed in the late 1990s. The chronology of the flooding is not straightforward because the connection between the Black Sea and the Mediterranean Sea involves the intermediate Marmara Sea Basin via two sills (Dardanelles and Bosphorus). This study explores the chronology of late Pleistocene-Holocene flooding by examining sedimentary facies and molluscs from 24 gravity cores spanning shelf to slope settings in the southern Marmara Sea Basin. A late Pleistocene Ponto-Caspian (Neoeuxinian) mollusc association is found in 12 of the cores, comprising 14 mollusc species and dominated by brackish (oligohaline-lower mesohaline) endemic taxa (dreissenids, hydrobiids). The Neoeuxinian association is replaced by a Turritella- Corbula association at the onset of the Holocene. The latter is dominated by marine species, several of which are known to thrive under dysoxic conditions in muddy bottoms. This association is common in early Holocene intervals as well as sapropel intervals in younger Holocene strata. It is an indicator of low-salinity outflows from the Black Sea into the Marmara Sea that drive stratification. A marine Mediterranean association (87 species) represents both soft bottom and hard substrate faunas that lived in well-ventilated conditions and upper mesohaline-polyhaline salinities (ca. 25 psu). Shallower areas were occupied by hard substrate taxa and phytopdetritic communities, whereas deeper areas had soft bottom faunas. The middle shelf part of the northern Gemlik Gulf has intervals with irregular and discontinuous sedimentary structures admixed with worn Neoeuxinian and euryhaline Mediterranean faunas. These intervals represent reworking events (slumping) likely related to seismic activity rooted in the North Anatolian Fault system. The core data and faunas indicate an oscillating postglacial sea-level rise and

  10. Holocene River Dynamics, Climate Change and Floodwater Farming in the Watersheds of the Pamir and Tien Shan Mountains of Inner Asia

    Science.gov (United States)

    Macklin, M. G.; Panyushkina, I. P.; Toonen, W. H. J.

    2014-12-01

    The Ili, Syr Dayra and Amu Dayra rivers of Inner Asia are emerging as critical areas for the development of irrigation-based agriculture in the ancient world. Following research by Russian archaeologists in the 1970s it is evident that these watersheds had flourishing riverine civilizations comparable to those in Mesopotamia and the Indus Valley. But unlike these areas where the relationship between Holocene river dynamics, climate change and floodwater farming is increasingly underpinned by radiometric dating, the alluvial archaeology of Inner Asia is significantly under researched. To address this, a major multi-disciplinary research program was begun in 2011 centred on the Talgar catchment, a south-bank tributary of the Ili river, southeast Kazakhstan. Building on archaeological excavations and surveys conducted over the past 20 years, we have undertaken one of the most detailed investigations of Holocene people-river environment interactions in Inner Asia. River development has been reconstructed over the last 20,000 years and human settlement histories from the Eneolithic to the Medieval period documented. Periods of Holocene river aggradation and high water levels in Lake Balkhash and Aral Sea correspond with cooler and wetter neoglacial episodes while river entrenchment and floodplain soil development are associated with warmer and drier conditions. Floodwater farming in the Talgar river reached its acme in the late Iron Age (400-200 cal. BC) with more than 60 settlement sites and 550 burial mounds. This corresponds to a period of reduced flood flows, river stability and glacier retreat in the Tien Shan headwaters. A new hydroclimatic-based model for the spatial and temporal dynamics of floodwater farming in the Ili, Syr Dayra and Amu Dayra watersheds is proposed, which explains the large scale expansion (down-river) and contraction (up-river) of settlements since the first use of irrigation in the Neolithic through to the late Medieval period.

  11. A model for the Holocene extinction of the mammal megafauna in Ecuador

    Science.gov (United States)

    Ficcarelli, G.; Coltorti, M.; Moreno-Espinosa, M.; Pieruccini, P. L.; Rook, L.; Torre, D.

    2003-03-01

    This paper presents the results of multidisciplinary research in the Ecuadorian coastal regions, with particular emphasis on the Santa Elena Peninsula. The new evidence, together with previous data gathered on the Ecuadorian cordillera during the last 12 years, allows us to formulate a model that accounts for most of the mammal megafauna extinction at the Pleistocene/Holocene transition. After the illustration of geomorphological and paleontological evidences of the area of the Santa Elena Peninsula (and other sites), and of a summary of the paleoclimatic data, the main results and conclusions of this work are: (1) Late Pleistocene mammal assemblages survived in the Ecuadorian coast until the Early Holocene sea level rise; (2) Prior to the extinction of most of the megafauna elements (mastodons, ground sloths, equids, sabre-tooth felids), the mammal communities at Santa Elena Peninsula comprise elements with differing habitat requirements, attesting conditions of high biological pressure; (3) At the El Cautivo site (Santa Elena Peninsula), we have discovered Holocene sediments containing the first known occurrences in Ecuador of lithic artifacts that are associated with mammal megafauna remains; (4) During the last 10,000 years, the coastal region of Ecuador underwent significant changes in vegetation cover. At the Pleistocene/Holocene transition the climate changed from very arid conditions to humid conditions. Our data indicates that the megafauna definitively abandoned the Cordillera areas around 12,000 yr BP due to t he increasing aridity, and subsequently migrated to coastal areas where ecological conditions still were suitable, Santa Elena Peninsula and mainly Amazonian areas being typical. We conclude that the unusual high faunal concentrations and the change to dense vegetation cover (due to a rapid increase in precipitation in the lower Holocene) at 8000-6000 yr BP, caused the final collapse and extinction of most elements of the mammal megafauna

  12. Sea level rise along Malaysian coasts due to the climate change

    Science.gov (United States)

    Luu, Quang-Hung; Tkalich, Pavel; Tay, Tzewei

    2015-04-01

    Malaysia consists of two major parts, a mainland on the Peninsular Malaysia and the East Malaysia on the Borneo Island. Their surrounding waters connect the Andaman Sea located northeast of the Indian Ocean to the Celebes Sea in the western tropical Pacific Ocean through the southern East Sea of Vietnam/South China Sea. As a result, inter-annual sea level in the Malaysian waters is governed by various regional phenomena associated with the adjacent parts of the Indian and Pacific Oceans. We estimated sea level rise (SLR) rate in the domain using tide gauge records often being gappy. To reconstruct the missing data, two methods are used: (i) correlating sea level with climate indices El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD), and (ii) filling the gap using records of neighboring tide gauges. Latest vertical land movements have been acquired to derive geocentric SLR rates. Around the Peninsular Malaysia, geocentric SLR rates in waters of Malacca Strait and eastern Peninsular Malaysia during 1986-2011 are found to be 3.9±3.3 mm/year and 4.2 ± 2.5 mm/year, respectively; while in the East Malaysia waters the rate during 1988-2011 is 6.3 ± 4.0 mm/year. These rates are arguably higher than global tendency for the same periods. For the overlapping period 1993-2011, the rates are consistent with those obtained using satellite altimetry.

  13. Holocene environmental changes and climate development in Greenland

    International Nuclear Information System (INIS)

    Engels, Stefan; Helmens, Karin

    2010-12-01

    The primary aim of this report is to give an overview of the Holocene environmental and climatic changes in Greenland and to describe the development of the periglacial environment during the Holocene. Special emphasis is given to the influence of the ice sheet on its surroundings, both in terms of time (with respect to the response of the biosphere to deglaciation or ice sheet proximity) and in space (through the influence of the ice sheet on the regional climate, more specifically on temperature and aridity). Published records are reviewed, and regional trends are summarized. A range of different natural archives is available for such studies, including ice-core data, marine records, and continental sources of information, including peat profiles and lacustrine records. Because of the high number of lakes in all ice-free areas of Greenland, the lacustrine records offer the opportunity to get a spatial overview of past changes in environment and climate as well. This report focuses on (palaeo-) ecological studies, as it is intended to assemble basic information for future studies on adaptation of the biosphere to changes in climate. There is a bias towards pollen- and macro-remain-based reconstructions of past changes, as these dominate performed palaeoecological studies in Greenland; unfortunately, only a limited number of studies exist that include more modern proxies such as diatoms or chironomids (climate-indicators), but where available in the literature, these have been included. The report starts with an introduction where the current climatic and biological zonation of Greenland is discussed together with an overview of the geology of Greenland (on the full geological timescale) in order to put the following sections in perspective. Chapter 2 discusses the ice sheet history of Greenland from the Last Glacial Maximum (LGM) onward where special emphasis is given to the spatial variability of deglaciation at the onset of the Holocene. To enhance the

  14. Holocene environmental changes and climate development in Greenland

    Energy Technology Data Exchange (ETDEWEB)

    Engels, Stefan; Helmens, Karin (Dept. of Physical Geography and Quaternary Geology, Stockholm Univ., Stockholm (Sweden))

    2010-12-15

    The primary aim of this report is to give an overview of the Holocene environmental and climatic changes in Greenland and to describe the development of the periglacial environment during the Holocene. Special emphasis is given to the influence of the ice sheet on its surroundings, both in terms of time (with respect to the response of the biosphere to deglaciation or ice sheet proximity) and in space (through the influence of the ice sheet on the regional climate, more specifically on temperature and aridity). Published records are reviewed, and regional trends are summarized. A range of different natural archives is available for such studies, including ice-core data, marine records, and continental sources of information, including peat profiles and lacustrine records. Because of the high number of lakes in all ice-free areas of Greenland, the lacustrine records offer the opportunity to get a spatial overview of past changes in environment and climate as well. This report focuses on (palaeo-) ecological studies, as it is intended to assemble basic information for future studies on adaptation of the biosphere to changes in climate. There is a bias towards pollen- and macro-remain-based reconstructions of past changes, as these dominate performed palaeoecological studies in Greenland; unfortunately, only a limited number of studies exist that include more modern proxies such as diatoms or chironomids (climate-indicators), but where available in the literature, these have been included. The report starts with an introduction where the current climatic and biological zonation of Greenland is discussed together with an overview of the geology of Greenland (on the full geological timescale) in order to put the following sections in perspective. Chapter 2 discusses the ice sheet history of Greenland from the Last Glacial Maximum (LGM) onward where special emphasis is given to the spatial variability of deglaciation at the onset of the Holocene. To enhance the

  15. Rapid Ice-Sheet Changes and Mechanical Coupling to Solid-Earth/Sea-Level and Space Geodetic Observation

    Science.gov (United States)

    Adhikari, S.; Ivins, E. R.; Larour, E. Y.

    2015-12-01

    Perturbations in gravitational and rotational potentials caused by climate driven mass redistribution on the earth's surface, such as ice sheet melting and terrestrial water storage, affect the spatiotemporal variability in global and regional sea level. Here we present a numerically accurate, computationally efficient, high-resolution model for sea level. Unlike contemporary models that are based on spherical-harmonic formulation, the model can operate efficiently in a flexible embedded finite-element mesh system, thus capturing the physics operating at km-scale yet capable of simulating geophysical quantities that are inherently of global scale with minimal computational cost. One obvious application is to compute evolution of sea level fingerprints and associated geodetic and astronomical observables (e.g., geoid height, gravity anomaly, solid-earth deformation, polar motion, and geocentric motion) as a companion to a numerical 3-D thermo-mechanical ice sheet simulation, thus capturing global signatures of climate driven mass redistribution. We evaluate some important time-varying signatures of GRACE inferred ice sheet mass balance and continental hydrological budget; for example, we identify dominant sources of ongoing sea-level change at the selected tide gauge stations, and explain the relative contribution of different sources to the observed polar drift. We also report our progress on ice-sheet/solid-earth/sea-level model coupling efforts toward realistic simulation of Pine Island Glacier over the past several hundred years.

  16. A 500 kyr record of global sea-level oscillations in the Gulf of Lion, Mediterranean Sea: new insights into MIS 3 sea-level variability

    Directory of Open Access Journals (Sweden)

    J. Frigola

    2012-06-01

    Full Text Available Borehole PRGL1-4 drilled in the upper slope of the Gulf of Lion provides an exceptional record to investigate the impact of late Pleistocene orbitally-driven glacio-eustatic sea-level oscillations on the sedimentary outbuilding of a river fed continental margin. High-resolution grain-size and geochemical records supported by oxygen isotope chronostratigraphy allow reinterpreting the last 500 ka upper slope seismostratigraphy of the Gulf of Lion. Five main sequences, stacked during the sea-level lowering phases of the last five glacial-interglacial 100-kyr cycles, form the upper stratigraphic outbuilding of the continental margin. The high sensitivity of the grain-size record down the borehole to sea-level oscillations can be explained by the great width of the Gulf of Lion continental shelf. Sea level driven changes in accommodation space over the shelf cyclically modified the depositional mode of the entire margin. PRGL1-4 data also illustrate the imprint of sea-level oscillations at millennial time-scale, as shown for Marine Isotopic Stage 3, and provide unambiguous evidence of relative high sea-levels at the onset of each Dansgaard-Oeschger Greenland warm interstadial. The PRGL1-4 grain-size record represents the first evidence for a one-to-one coupling of millennial time-scale sea-level oscillations associated with each Dansgaard-Oeschger cycle.

  17. Benthic foraminifera response to Holocene environmental changes in the ria de Muros (NW Spain)

    Science.gov (United States)

    Diz, P.; Francés, G.; Pena, L. D.; Nombela, M. A.; Alejo, I.

    2003-04-01

    Benthic foraminifera assemblages from the outer sector of the ría de Muros have been analyzed in order to obtain a detailed reconstruction of Holocene environmental evolution. The studied core (EUGC-3B: 42' 45.10'N; 9' 02.23'W, at 38 m.b.s.l. and 410 cm length) consists of muddy sand from the core bottom (8200 cal yr BP) to 200 cm (2700 cal yr BP) and mainly mud from 200 cm to the core top. Measurements of geochemical properties carried out by a XRF core scanner revealed different signatures in the two aforementioned intervals and an enhancing terrigenous influence during the last 2000 yr. The prevalence of Bulimina spp., Nonion fabum, Ammonia beccarii and Cibicides ungerianus along the whole core indicates high organic carbon concentration and/or low oxygenation levels into the sediment. Nevertheless, the percentage of these species shows noticeable changes, indicating the existence of five periods with different environmental conditions. The basal assemblage (8200-7500 cal yr BP) is dominated by epifaunal taxa and it can be interpreted as a low sea level assemblage. An increase of fresh water influence during the Holocene Climate Optimum (7500-5000 cal yr BP) is revealed by maxima percentages of A. beccarii. The oceanic influence increased during the Subboreal period (5000-2750 cal yr BP) leading to an active water interchange between the ría and the open ocean and a higher marine productivity. The oceanic influence is recorded by the increase of typical marine species as Elphidium advenum, Bulimina spp., N. fabum, and Nonionella turgida. The appearance of Rectuvigerina phlegeri at 4000 cal yr BP denotes full marine conditions. Environmental conditions similar to the current ones were achieved during the Subatlantic period (2750-Rec). In a first step an assemblage dominated by Bulimina spp. N. fabum, and C. ungerianus permit us to interpret a relatively stable period with episodic pulses of fluvial influence. Afterwards the appearance and the rapid increase of

  18. Mid- to late-Holocene coastal environmental changes in southwest Florida, USA

    NARCIS (Netherlands)

    Soelen, E.E. van; Brooks, G.R.; Larson, R.A.; Sinninghe Damsté, J.S.; Reichart, G.-J.

    2012-01-01

    During the Holocene, Florida experienced major changes in precipitation and runoff. To better understand these processes, shallow marine sediment cores from Charlotte Harbor (southwest Florida) were studied, covering approximately the past 9000 years. Whole core XRF scanning was applied to

  19. Holocene environmental changes recorded in Dicksonfjorden and Woodfjorden, Svalbard: impacts of global climate changes in a glacial-marine system

    Science.gov (United States)

    Joo, Y. J.; Nam, S. I.; Son, Y. J.; Forwick, M.

    2017-12-01

    Fjords in the Svalbard archipelago are characterized by an extreme environmental gradient between 1) the glacial system affected by tidewater glaciers and seasonal sea ice inside the fjords and 2) the warm Atlantic Water intrusion by the West Spitsbergen Current from open ocean. As sediment is largely supplied from the terrestrial source area exposed along the steep slopes of the fjords, the changes in the surface processes affected by glaciers are likely preserved in the sediments in the inner fjords. On the other hand, variations in the influence of the warm Atlantic Water in the marine realm (e.g. marine productivity) can be archived in the sediment deposited in the vicinity of the entrance to the fjords. Since the last deglaciation of the Svalbard-Barents ice sheet ( 13000 yrs BP), the Svalbard fjords have faced dramatic climate changes including the early Holocene Climate Optimum (HCO) and subsequent cooling that eventually led to the current cold and dry climate. We investigate the Holocene environmental changes in both terrestrial and marine realms based on stable isotopic and inorganic geochemical analyses of sediments deposited in Dicksonfjorden and Woodfjorden in the western and northern Spitsbergen, respectively. The two fjords are expected to provide intriguing information regarding how terrestrial and marine realms of the Arctic fjords system responded to regional and global climate changes. Being a branch of the larger Isfjorden, Dicksonfjorden penetrates deeply to the land, whereas Woodfjorden is rather directly connected to the open ocean. Accordingly, the results suggest that the Dicksonfjorden sediment records mainly terrestrial signals with marked fluctuations in sediment composition that coincide with major climate changes (e.g. HCO). On the contrary, the two Woodfjorden cores collected from different parts of the fjord exhibit contrasting results, likely illustrating differing response of terrestrial and marine realms to the climate changes in

  20. Measuring progress of the global sea level observing system

    Science.gov (United States)

    Woodworth, Philip L.; Aarup, Thorkild; Merrifield, Mark; Mitchum, Gary T.; Le Provost, Christian

    Sea level is such a fundamental parameter in the sciences of oceanography geophysics, and climate change, that in the mid-1980s, the Intergovernmental Oceanographic Commission (IOC) established the Global Sea Level Observing System (GLOSS). GLOSS was to improve the quantity and quality of data provided to the Permanent Service for Mean Sea Level (PSMSL), and thereby, data for input to studies of long-term sea level change by the Intergovernmental Panel on Climate Change (IPCC). It would also provide the key data needed for international programs, such as the World Ocean Circulation Experiment (WOCE) and later, the Climate Variability and Predictability Programme (CLIVAR).GLOSS is now one of the main observation components of the Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM) of IOC and the World Meteorological Organization (WMO). Progress and deficiencies in GLOSS were presented in July to the 22nd IOC Assembly at UNESCO in Paris and are contained in the GLOSS Assessment Report (GAR) [IOC, 2003a].

  1. Evaluation of sea level rise in Bohai Bay and associated responses

    Directory of Open Access Journals (Sweden)

    Ke-Xiu LIU

    2017-03-01

    Full Text Available Tide gauge data from 1950 to 2015 are used to analyze sea level change, tidal change, return levels, and design tide levels under rising sea level scenarios in Bohai Bay. Results show the following: 1 Since 1950 sea levels in Bohai Bay show a significant rising trend of 3.3 mm per year. The speed has been particularly rapid in 1980–2015 at a rate of 4.7 mm per year. 2 Astronomical tides showed a clear long-term trend in 1950–2015. The amplitude and phase lag of the M2 tide constituent decreased at a rate of 0.21 cm per year and 0.11° per year, respectively and the phase lag of K1 decreased at a rate of 0.09° per year, whereas there was little change in its amplitude. The mean high and low tides increased at a rate of 0.08 and 0.52 cm per year, respectively, whereas the mean tidal range decreased at a rate of 0.44 cm per year. Results from numerical experiments show that local sea level rise plays an important role in the tidal dynamics change in Bohai Bay. 3 It is considered that the sea level return periods will decrease owing to the influence of sea level rise and land subsidence, therefore design tide level will change in relation to sea level rise. Therefore, the ability of seawalls to withstand water will diminish, and storm surge disasters will become more serious in the future.

  2. Holocene vegetation and climate change on the Haanja heights, South-East Estonia

    International Nuclear Information System (INIS)

    Saarse, Leili; Rajamaee, Raivo

    1997-01-01

    The development of forests on the Haanja Heights has been controlled by external factors, including climate, soils, hydrology, and human impact. The sediment sequence from Lake Kirikumaee, which covers about 12 000 years, records the vegetation history throughout the Late Glacial and Holocene. In the Alleroed, woodland tundra with sparse birch and willow was established. Grass-shrub tundra in the Younger Dryas was replaced by birch forest in the Pre-Boreal. During the Holocene two major shifts in vegetation dynamics occurred: the first about 8500 BP with a sharp decline in Betula-Pinus forest and development of broad-leaved forest, and the second about 3500 BP, with a decline in broad-leaved forest and regeneration of Pinus-Betula forest with a high share of Picea. The climate modelling, based on pollen record and lake-level changes, suggest cold, severe climate with low precipitation values in the early Pre-Boreal. Between 9500-8500 BP the climate was rather stable. The lake level first rose, then stabilized, and finally dropped. The sharp climate amelioration in the late Boreal together with the humidity increase resulted in a lake-level rise. The decreased precipitation and rather high summer temperatures, increased evapotranspiration, and reduced water balance are characteristic of the Sub-Boreal. Since 3500 BP, the climate deteriorated and mixed coniferous forest started to dominate. Several small climatic fluctuations, including the Little Ice Age cooling, have been traced by modelling. (author)

  3. Deglacial remobilization of permafrost carbon to sediments along the East Siberian Arctic Seas

    Science.gov (United States)

    Martens, J.; Wild, B.; Bröder, L.; Andersson, A.; Pearce, C.; O'Regan, M.; Jakobsson, M.; Tesi, T.; Muschitiello, F.; Sköld, M.; Semiletov, I. P.; Dudarev, O.; Gustafsson, O.

    2017-12-01

    Current climate change is expected to thaw large quantities of permafrost carbon (PF-C) and expose it to degradation which emits greenhouse gases (i.e. CO2 and CH4). Warming causes a gradual deepening of the seasonally thawed active layer surface of permafrost soils, but also the abrupt collapse of deeper Ice Complex Deposits (ICD), especially along Siberian coastlines. It was recently hypothesized that past warming already induced large-scale permafrost degradation after the last glacial, which ultimately amplified climate forcing. We here assess the mobilization of PF-C to East Siberian Arctic Sea sediments during these warming periods. We perform source apportionment using bulk carbon isotopes (ΔΔ14C, δ13C) together with terrestrial biomarkers (CuO-derived lignin phenols) as indicators for PF-C transfer. We apply these techniques to sediment cores (SWERUS-L2) from the Chukchi Sea (4-PC1) and the southern Lomonosov Ridge (31-PC1). We found that PF-C fluxes during the Bølling-Allerød warming (14.7 to 12.7 cal ka BP), the Younger Dryas cooling (12.7 to 11.7 cal ka BP) and the early Holocene warming (until 11 cal ka BP) were overall higher than mid and late Holocene fluxes. In the Chukchi Sea, PF-C burial was 2x higher during the deglaciation (7.2 g m-2 a-1) than in the mid and late Holocene (3.6 g m-2 a-1), and ICD were the dominant source of PF-C (79.1%). Smaller fractions originated from the active layer (9.1%) and marine sources (11.7%). We conclude that thermo-erosion of ICD released large amounts of PF-C to the Chukchi Sea, likely driven by climate warming and the deglacial sea level rise. This contrasts to earlier analyses of Laptev Sea sediments where active layer material from river transport dominated the carbon flux. Preliminary data on lignin phenol concentrations of Lomonosov Ridge sediments suggest that the postglacial remobilization of PF-C was one order of magnitude higher (10x) than during both the preceding glacial and the subsequent Holocene

  4. Holocene vegetation history from fossil rodent middens near Arequipa, Peru

    Science.gov (United States)

    Holmgren, C.A.; Betancourt, J.L.; Rylander, K.A.; Roque, J.; Tovar, O.; Zeballos, H.; Linares, E.; Quade, Jay

    2001-01-01

    Rodent (Abrocoma, Lagidium, Phyllotis) middens collected from 2350 to 2750 m elevation near Arequipa, Peru (16??S), provide an ???9600-yr vegetation history of the northern Atacama Desert, based on identification of >50 species of plant macrofossils. These midden floras show considerable stability throughout the Holocene, with slightly more mesophytic plant assemblages in the middle Holocene. Unlike the southwestern United States, rodent middens of mid-Holocene age are common. In the Arequipa area, the midden record does not reflect any effects of a mid-Holocene mega drought proposed from the extreme lowstand (100 m below modern levels, >6000 to 3500 yr B.P.) of Lake Titicaca, only 200 km east of Arequipa. This is perhaps not surprising, given other evidence for wetter summers on the Pacific slope of the Andes during the middle Holocene as well as the poor correlation of summer rainfall among modern weather stations in the central AndesAtacama Desert. The apparent difference in paleoclimatic reconstructions suggests that it is premature to relate changes observed during the Holocene to changes in El Nin??o Southern Oscillation modes. ?? 2001 University of Washington.

  5. Global sea level change and the response of solid earth; Kaisuijun hendo ni taisuru kotai chikyu no yakuwari

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Y. [Geological Survey of Japan, Tsukuba (Japan)

    1997-05-27

    A review was given on the theory that sea level change having occurred in the past 20,000 years has given a great impact on patterns of upheaval and subsidence of the islands of Japan. Nakada has summarized distribution of underwater remains in the western part of Kyushu and estimated values of sea surface altitude in 6000 years ago, and used this conceptional chart to propose a crust upheaval mechanism by using hydroisostasy. More specifically, this is a model that crust which has subsided due to rise in the sea level has created flows of mantle, causing upheaval of the crust in land areas. This viewpoint requires further accumulation of data and verification of the theory in areas other than the western part of Kyushu. It is important to consider the effect of sea level change also in studying processes of subsidence and sedimentation in sedimentary basins including Osaka Bay. The currently available theories use analysis solutions on stratified ground, but does not consider topographical profiles from land areas to sea areas. As this topographical effect is thought extremely important, it is necessary to develop a two-dimensional cross section analyzing method by using the finite element method. 6 refs., 3 figs.

  6. Separating decadal global water cycle variability from sea level rise.

    Science.gov (United States)

    Hamlington, B D; Reager, J T; Lo, M-H; Karnauskas, K B; Leben, R R

    2017-04-20

    Under a warming climate, amplification of the water cycle and changes in precipitation patterns over land are expected to occur, subsequently impacting the terrestrial water balance. On global scales, such changes in terrestrial water storage (TWS) will be reflected in the water contained in the ocean and can manifest as global sea level variations. Naturally occurring climate-driven TWS variability can temporarily obscure the long-term trend in sea level rise, in addition to modulating the impacts of sea level rise through natural periodic undulation in regional and global sea level. The internal variability of the global water cycle, therefore, confounds both the detection and attribution of sea level rise. Here, we use a suite of observations to quantify and map the contribution of TWS variability to sea level variability on decadal timescales. In particular, we find that decadal sea level variability centered in the Pacific Ocean is closely tied to low frequency variability of TWS in key areas across the globe. The unambiguous identification and clean separation of this component of variability is the missing step in uncovering the anthropogenic trend in sea level and understanding the potential for low-frequency modulation of future TWS impacts including flooding and drought.

  7. Sea-level and deep-sea-temperature variability over the past 5.3 million years.

    Science.gov (United States)

    Rohling, E J; Foster, G L; Grant, K M; Marino, G; Roberts, A P; Tamisiea, M E; Williams, F

    2014-04-24

    Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope (δ(18)O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature.

  8. A first look at the ACER-SST dataset: Mapping the spatio-temporal variability of sea-surface temperatures in the last Glacial and the Holocene

    Science.gov (United States)

    Rehfeld, Kira; Laepple, Thomas; Bassinot, Franck; Daniau, Anne-Laure; Desprat, Stéphanie; Kim, Jung-Hyun; Fernanda Sánchez-Goñi, Maria; Harrison, Sandy

    2016-04-01

    Climate in the last Glacial was characterized by abrupt and large-scale changes around cold Heinrich-Events and warm Dansgaard-Oeschger excursions in the Northern high latitudes. The global repercussions of these periods of rapid dynamics are, to date, unconstrained. Here, we present a first statistical analysis of the global multi-proxy ACER (Abrupt Climate Changes and Environmental Responses) sea surface temperature dataset, spanning the last 80 thousand years, to investigate the spatial footprints of glacial climate dynamics. In a first step we evaluate the spatial and temporal variability throughout the Glacial period, and contrast them with that during the Holocene. In a second step we investigate to which extent a temporal synchroneity of extreme events during the Glacial is detectable in the proxy records, and analyze the reversibility of Glacial dynamics.

  9. High-resolution reconstruction of extreme storm events over the North Sea during the Late Holocene: inferences from aeolian sand influx in coastal mires, Western Denmark.

    Science.gov (United States)

    Goslin, Jerome; Clemmensen, Lars B.

    2017-04-01

    Possessing long and accurate archives of storm events worldwide is the key for a better understanding of the atmospheric patterns driving these events and of the response of the coastal systems to storms. To be adequately addressed, the ongoing and potential future changes in wind regimes (including in particular the frequency and magnitude of storm events) have to be replaced in the context of long-time records of past storminess, i.e. longer than the century-scale records of instrumental weather data which do not allow the calculation of reliable return periods. During the last decade, several Holocene storminess chronologies have been based on storm-traces left by aeolian processes within coastal lakes, mires and peat bogs, (e.g. Björck and Clemmensen, 2004; De Jong et al., 2006; Clemmensen et al., 2009; Nielsen et al.; 2016; Orme et al., 2016). These data have shown to adequately complement the records which can be derived from the study of records related to wave-induced processes including e.g. washover deposits. Previous works along the west coast of Jutland, Denmark have revealed four main periods of dune building during the last 4200 yrs (Clemmensen et al., 2001; 2009). These were shown to be in phase with periods of climate deterioration (cold periods) recognized elsewhere in Europe and the North Atlantic region and suggest periods of increased aeolian activity. Yet, doubts remain on whether these periods where characterized by several big short-lived storm events or rather by an overall increase in wind energy. This study aims at constructing a high-resolution (centennial to multi-decadal) history of past storminess over the North Sea for the last millenaries. Plurimeter sequences of peat and gyttja have been retrieved from two coastal mires and were analyzed for their sand content. The quartz grains were systematically counted within centimetric slices (Aeolian Sand Influx method, Björck & Clemmensen, 2004), while the palaeo-environmental context and

  10. Global change and relative sea level rise at Venice: what impact in term of flooding

    Energy Technology Data Exchange (ETDEWEB)

    Carbognin, Laura; Tosi, Luigi [Institute of Marine Sciences, National Research Council, Venice (Italy); Teatini, Pietro [Institute of Marine Sciences, National Research Council, Venice (Italy); University of Padova, Department of Mathematical Methods and Models for Scientific Applications, Padua (Italy); Tomasin, Alberto [Institute of Marine Sciences, National Research Council, Venice (Italy); University Ca' Foscari in Venice, Venice (Italy)

    2010-11-15

    Relative sea level rise (RSLR) due to climate change and geodynamics represents the main threat for the survival of Venice, emerging today only 90 cm above the Northern Adriatic mean sea level (msl). The 25 cm RSLR occurred over the 20th century, consisting of about 12 cm of land subsidence and 13 cm of sea level rise, has increased the flood frequency by more than seven times with severe damages to the urban heritage. Reasonable forecasts of the RSLR expected to the century end must be investigated to assess the suitability of the Mo.S.E. project planned for the city safeguarding, i.e., the closure of the lagoon inlets by mobile barriers. Here we consider three RSLR scenarios as resulting from the past sea level rise recorded in the Northern Adriatic Sea, the IPCC mid-range A1B scenario, and the expected land subsidence. Available sea level measurements show that more than 5 decades are required to compute a meaningful eustatic trend, due to pseudo-cyclic 7-8 year long fluctuations. The period from 1890 to 2007 is characterized by an average rate of 0.12 {+-} 0.01 cm/year. We demonstrate that linear regression is the most suitable model to represent the eustatic process over these 117 year. Concerning subsidence, at present Venice is sinking due to natural causes at 0.05 cm/year. The RSLR is expected to range between 17 and 53 cm by 2100, and its repercussions in terms of flooding frequency are associated here to each scenario. In particular, the frequency of tides higher than 110 cm, i.e., the value above which the gates would close the lagoon to the sea, will increase from the nowadays 4 times per year to a range between 20 and 250. These projections provide a large spread of possible conditions concerning the survival of Venice, from a moderate nuisance to an intolerable aggression. Hence, complementary solutions to Mo.S.E. may well be investigated. (orig.)

  11. Late Frasnian sedimentation cycles in the Appalachian basin—possible evidence for high frequency eustatic sea-level changes

    Science.gov (United States)

    Filer, Jonathan K.

    2002-12-01

    During the late Frasnian, 11 fourth-order progradational/retrogradational marine sedimentation cycles were deposited in the Appalachian foreland basin. Mapping based primarily on subsurface data demonstrates the continuity of these cycles over a distance of 700 km. Cyclicity in distal facies occurs as alternations of organic-rich and organic-poor shales, two of the organic shales can be correlated with the transgressive "Kellwasser Beds" of Europe. In more proximal facies, recurring lobes of siltstone and sandstone were deposited. Based on lithologic indices, the temporal pattern shows significant variation in the strength of relative facies change during deposition. In particular, two times of particularly pronounced progradation correspond to previously recognized eustatic sea-level falls. The correlation of portions of Appalachian basin depositional cyclicity with global sea-level events suggests that the entire sequence of 11 cycles, with estimated average duration of around 100-150 ka, were the result of high-frequency eustatic sea-level changes. This in turn would be consistent with a brief period of late Frasnian glaciation, as others have previously suggested.

  12. Large floods and climatic change during the Holocene on the Ara River, Central Japan

    Science.gov (United States)

    Grossman, Michael J.

    2001-07-01

    A reconstruction of part of the Holocene large flood record for the Ara River in central Japan is presented. Maximum intermediate gravel-size dimensions of terrace and modern floodplain gravels were measured along an 18-km reach of the river and were used in tractive force equations to estimate minimum competent flood depths. Results suggest that the magnitudes of large floods on the Ara River have varied in a non-random fashion since the end of the last glacial period. Large floods with greater magnitudes occurred during the warming period of the post-glacial and the warmer early to middle Holocene (to ˜5500 years BP). A shift in the magnitudes of large floods occurred ˜5500-5000 years BP. From this time, during the cooler middle to late Holocene, large floods generally had lower magnitudes. In the modern period, large flood magnitudes are the largest in the data set. As typhoons are the main cause of large floods on the Ara River in the modern record, the variation in large flood magnitudes suggests that the incidence of typhoon visits to the central Japan changed as the climate changed during the Holocene. Further, significant dates in the large flood record on the Ara River correspond to significant dates in Europe and the USA.

  13. A decade of sea level rise slowed by climate-driven hydrology.

    Science.gov (United States)

    Reager, J T; Gardner, A S; Famiglietti, J S; Wiese, D N; Eicker, A; Lo, M-H

    2016-02-12

    Climate-driven changes in land water storage and their contributions to sea level rise have been absent from Intergovernmental Panel on Climate Change sea level budgets owing to observational challenges. Recent advances in satellite measurement of time-variable gravity combined with reconciled global glacier loss estimates enable a disaggregation of continental land mass changes and a quantification of this term. We found that between 2002 and 2014, climate variability resulted in an additional 3200 ± 900 gigatons of water being stored on land. This gain partially offset water losses from ice sheets, glaciers, and groundwater pumping, slowing the rate of sea level rise by 0.71 ± 0.20 millimeters per year. These findings highlight the importance of climate-driven changes in hydrology when assigning attribution to decadal changes in sea level. Copyright © 2016, American Association for the Advancement of Science.

  14. Responding to changes in sea level: engineering implications

    National Research Council Canada - National Science Library

    National Research Council Staff; Marine Board; Commission on Engineering and Technical Systems; Division on Engineering and Physical Sciences; National Research Council

    1987-01-01

    ... Mean Sea Level Marine Board Commission on Engineering and Technical Systems National Research Council National Academy Press Washington, D.C. 1987 Copyrightthe cannot be not from book, paper however, version for formatting, original authoritative the typesetting-specific the as from created publication files XML from other this and of recom...

  15. Climate and lake-level history of the northern Altiplano, Bolivia, as recorded in Holocene sediments of the Rio Desaguadero

    Energy Technology Data Exchange (ETDEWEB)

    Baucom, P.C.; Rigsby, C.A. [East Carolina Univ., Greenville, NC (United States). Dept. of Geology

    1999-05-01

    Strata exposed in terraces and modern cutbanks along the Rio Desaguadero contain a variety of lithofacies that were deposited in four distinct facies associations. These facies associations document a history of aggradation and downcutting that is linked to Holocene climate change on the Altiplano. Braided-stream, meandering-stream, deltaic and shoreline, and lacustrine sediments preserved in multi-level terraces in the northern Rio Desaguadero valley record two high-water intervals: one between 4,500 and 3,900 yr BP and another between 2,000 and 2,200 yr BP. These wet periods were interrupted by three periods of fluvial downcutting, centered at approximately 4,000 yr BP, 3,600 yr BP, and after 2,000 yr BP. Braided-river sediments preserved in a single terrace level in the southern Rio Desaguadero valley record a history of nearly continuous fluvial sedimentation from at least 7,000 yr BP until approximately 3,200 yr BP that was followed by a single episode (post-3,210 yr BP) of down-cutting and lateral migration. The deposition and subsequent fluvial downcutting of the northern strata was controlled by changes in effective moisture that can be correlated to Holocene water-level fluctuations of Lake Titicaca. The deposition and dissection of braided-stream sediments to the south are more likely controlled by a combination of base-level change and sediment input from the Rio Mauri.

  16. Upper Limit for Regional Sea Level Projections

    Science.gov (United States)

    Jevrejeva, Svetlana; Jackson, Luke; Riva, Riccardo; Grinsted, Aslak; Moore, John

    2016-04-01

    With more than 150 million people living within 1 m of high tide future sea level rise is one of the most damaging aspects of warming climate. The latest Intergovernmental Panel on Climate Change report (AR5 IPCC) noted that a 0.5 m rise in mean sea level will result in a dramatic increase the frequency of high water extremes - by an order of magnitude, or more in some regions. Thus the flood threat to the rapidly growing urban populations and associated infrastructure in coastal areas are major concerns for society. Hence, impact assessment, risk management, adaptation strategy and long-term decision making in coastal areas depend on projections of mean sea level and crucially its low probability, high impact, upper range. With probabilistic approach we produce regional sea level projections taking into account large uncertainties associated with Greenland and Antarctica ice sheets contribution. We calculate the upper limit (as 95%) for regional sea level projections by 2100 with RCP8.5 scenario, suggesting that for the most coastlines upper limit will exceed the global upper limit of 1.8 m.

  17. An abrupt centennial-scale drought event and mid-holocene climate change patterns in monsoon marginal zones of East Asia.

    Directory of Open Access Journals (Sweden)

    Yu Li

    Full Text Available The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to

  18. Lakeside cemeteries in the Sahara: 5000 years of holocene population and environmental change.

    Directory of Open Access Journals (Sweden)

    Paul C Sereno

    Full Text Available BACKGROUND: Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene ( approximately 8000 B.C.E. to the present. Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation. METHODOLOGY/PRINCIPAL FINDINGS: Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to approximately 7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return approximately 4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments. CONCLUSIONS/SIGNIFICANCE: The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following: The early Holocene occupants at Gobero (7700-6200 B.C.E. were largely sedentary hunter-fisher-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara.Principal components analysis of craniometric variables closely allies the early Holocene occupants at Gobero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and southern Sahara.Gobero was abandoned during a period of severe aridification possibly as long as one millennium (6200-5200 B.C.E.More gracile humans arrived in the mid-Holocene

  19. Determining Late Pleistocene to Early Holocene deglaciation of the Baltic Ice Lake through sedimentological core sample analysis of IODP Site M0064

    Science.gov (United States)

    Kelly, A. L.; Passchier, S.

    2016-12-01

    This study investigates the deglaciation history of the Scandinavian Ice Sheet (SIS) within the Baltic Sea's Hanö Bay from the Late Pleistocene to the Holocene using samples from International Ocean Discovery Program (IODP) Site M0064. The research aims to understand how the speed of deglaciation influences Baltic Ice Lake (BIL) drainage patterns and relative sea level changes on a high-resolution timescale. Glacial history of the SIS has been studied through glacial till analysis, surface exposure dating, and modeling, encompassing its most recent deglaciation 20-14ka BP, and suggests ice retreated from the project site 16.7ka BP. Between 17 and 14ka BP global sea level rose 4 meters per century, accompanied by a dramatic increase in atmospheric carbon. This period of rapid sea level rise and global warming is a valuable analog for understanding the Earth's current and projected climate. This project uses particle size analysis to better understand the late-glacial depositional environment in Hanö Bay, and ICP-OES geochemical analysis for evidence pertaining to changing sediment provenance and bottom water oxygenation in the BIL. Diamicton is present between 47 and 9 mbsf in Hole M0064D. At 8 mbsf, the sediment exhibits a prominent upward transition from well-laminated cm-scale grey to more thinly laminated reddish brown rhythmites. With calculated Al/Ti ratios, we find that there is not much provenance change in the sequence, however we see fluctuations in Mn/Al ratios, implying shifts in sediment color may be chemical, possibly indicating redox changes in the water column during sediment deposition. Although we find that particle size in the varve sequence does not change, this factor may be driving chemical fluctuations in the diamicton. These results increase the understanding of ice retreat, paleocirculation and relative sea level changes in the Baltic Sea at the onset of the last deglaciation.

  20. A multiple-proxy approach to understanding rapid Holocene climate change in Southeast Greenland

    Science.gov (United States)

    Davin, S. H.; Bradley, R. S.; Balascio, N. L.; de Wet, G.

    2012-12-01

    The susceptibility of the Arctic to climate change has made it an excellent workshop for paleoclimatological research. Although there have been previous studies concerning climate variability carried out in the Arctic, there remains a critical dearth of knowledge due the limited number of high-resolution Holocene climate-proxy records available from this region. This gap skews our understanding of observed and predicted climate change, and fuels uncertainty both in the realms of science and policy. This study takes a comprehensive approach to tracking Holocene climate variability in the vicinity of Tasiilaq, Southeast Greenland using a ~5.6 m sediment core from Lower Sermilik Lake. An age-depth model for the core has been established using 8 radiocarbon dates, the oldest of which was taken at 4 m down core and has been been dated to approximately 6.2 kyr BP. The bottom meter of the core below the final radiocarbon date contains a transition from cobbles and coarse sand to organic-rich laminations, indicating the termination of direct glacial influence and therefore likely marking the end of the last glacial period in this region. The remainder of the core is similarly organic-rich, with light-to-dark brown laminations ranging from 0.5 -1 cm in thickness and riddled with turbidites. Using this core in tandem with findings from an on-site assessment of the geomorphic history of the locale we attempt to assess and infer the rapid climatic shifts associated with the Holocene on a sub-centennial scale. Such changes include the termination of the last glacial period, the Mid-Holocene Climatic Optimum, the Neoglacial Period, the Medieval Climatic Optimum, and the Little Ice Age. A multiple proxy approach including magnetic susceptibility, bulk organic geochemistry, elemental profiles acquired by XRF scanning, grain-size, and spectral data will be used to characterize the sediment and infer paleoclimate conditions. Additionally, percent biogenic silica by weight has been

  1. Alkenone-based reconstructions reveal four-phase Holocene temperature evolution for High Arctic Svalbard

    Science.gov (United States)

    van der Bilt, Willem G. M.; D'Andrea, William J.; Bakke, Jostein; Balascio, Nicholas L.; Werner, Johannes P.; Gjerde, Marthe; Bradley, Raymond S.

    2018-03-01

    Situated at the crossroads of major oceanic and atmospheric circulation patterns, the Arctic is a key component of Earth's climate system. Compounded by sea-ice feedbacks, even modest shifts in the region's heat budget drive large climate responses. This is highlighted by the observed amplified response of the Arctic to global warming. Assessing the imprint and signature of underlying forcing mechanisms require paleoclimate records, allowing us to expand our knowledge beyond the short instrumental period and contextualize ongoing warming. However, such datasets are scarce and sparse in the Arctic, limiting our ability to address these issues. Here, we present two quantitative Holocene-length paleotemperature records from the High Arctic Svalbard archipelago, situated in the climatically sensitive Arctic North Atlantic. Temperature estimates are based on U37K unsaturation ratios from sediment cores of two lakes. Our data reveal a dynamic Holocene temperature evolution, with reconstructed summer lake water temperatures spanning a range of ∼6-8 °C, and characterized by four phases. The Early Holocene was marked by an early onset (∼10.5 ka cal. BP) of insolation-driven Hypsithermal conditions, likely compounded by strengthening oceanic heat transport. This warm interval was interrupted by cooling between ∼10.5-8.3 ka cal. BP that we attribute to cooling effects from the melting Northern Hemisphere ice sheets. Temperatures declined throughout the Middle Holocene, following a gradual trend that was accentuated by two cooling steps between ∼7.8-7 ka cal. BP and around ∼4.4-4.3 ka cal. BP. These transitions coincide with a strengthening influence of Arctic water and sea-ice in the adjacent Fram Strait. During the Late Holocene (past 4 ka), temperature change decoupled from the still-declining insolation, and fluctuated around comparatively cold mean conditions. By showing that Holocene Svalbard temperatures were governed by an alternation of forcings, this study

  2. Probabilistic reanalysis of twentieth-century sea-level rise.

    Science.gov (United States)

    Hay, Carling C; Morrow, Eric; Kopp, Robert E; Mitrovica, Jerry X

    2015-01-22

    Estimating and accounting for twentieth-century global mean sea level (GMSL) rise is critical to characterizing current and future human-induced sea-level change. Several previous analyses of tide gauge records--employing different methods to accommodate the spatial sparsity and temporal incompleteness of the data and to constrain the geometry of long-term sea-level change--have concluded that GMSL rose over the twentieth century at a mean rate of 1.6 to 1.9 millimetres per year. Efforts to account for this rate by summing estimates of individual contributions from glacier and ice-sheet mass loss, ocean thermal expansion, and changes in land water storage fall significantly short in the period before 1990. The failure to close the budget of GMSL during this period has led to suggestions that several contributions may have been systematically underestimated. However, the extent to which the limitations of tide gauge analyses have affected estimates of the GMSL rate of change is unclear. Here we revisit estimates of twentieth-century GMSL rise using probabilistic techniques and find a rate of GMSL rise from 1901 to 1990 of 1.2 ± 0.2 millimetres per year (90% confidence interval). Based on individual contributions tabulated in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, this estimate closes the twentieth-century sea-level budget. Our analysis, which combines tide gauge records with physics-based and model-derived geometries of the various contributing signals, also indicates that GMSL rose at a rate of 3.0 ± 0.7 millimetres per year between 1993 and 2010, consistent with prior estimates from tide gauge records.The increase in rate relative to the 1901-90 trend is accordingly larger than previously thought; this revision may affect some projections of future sea-level rise.

  3. Analysis of Sea Level Rise in Singapore Strait

    Science.gov (United States)

    Tkalich, Pavel; Luu, Quang-Hung

    2013-04-01

    Sea level in Singapore Strait is governed by various scale phenomena, from global to local. Global signals are dominated by the climate change and multi-decadal variability and associated sea level rise; at regional scale seasonal sea level variability is caused by ENSO-modulated monsoons; locally, astronomic tides are the strongest force. Tide gauge records in Singapore Strait are analyzed to derive local sea level trend, and attempts are made to attribute observed sea level variability to phenomena at various scales, from global to local. It is found that at annual scale, sea level anomalies in Singapore Strait are quasi-periodic, of the order of ±15 cm, the highest during northeast monsoon and the lowest during southwest monsoon. Interannual regional sea level falls are associated with El Niño events, while the rises are related to La Niña episodes; both variations are in the range of ±9 cm. At multi-decadal scale, sea level in Singapore Strait has been rising at the rate 1.2-1.9 mm/year for the period 1975-2009, 2.0±0.3 mm/year for 1984-2009, and 1.3-4.7 mm/year for 1993-2009. When compared with the respective global trends of 2.0±0.3, 2.4, and 2.8±0.8 mm/year, Singapore Strait sea level rise trend was weaker at the earlier period and stronger at the recent decade.

  4. A scaling approach to project regional sea level rise and its uncertainties

    Directory of Open Access Journals (Sweden)

    M. Perrette

    2013-01-01

    Full Text Available Climate change causes global mean sea level to rise due to thermal expansion of seawater and loss of land ice from mountain glaciers, ice caps and ice sheets. Locally, sea level can strongly deviate from the global mean rise due to changes in wind and ocean currents. In addition, gravitational adjustments redistribute seawater away from shrinking ice masses. However, the land ice contribution to sea level rise (SLR remains very challenging to model, and comprehensive regional sea level projections, which include appropriate gravitational adjustments, are still a nascent field (Katsman et al., 2011; Slangen et al., 2011. Here, we present an alternative approach to derive regional sea level changes for a range of emission and land ice melt scenarios, combining probabilistic forecasts of a simple climate model (MAGICC6 with the new CMIP5 general circulation models. The contribution from ice sheets varies considerably depending on the assumptions for the ice sheet projections, and thus represents sizeable uncertainties for future sea level rise. However, several consistent and robust patterns emerge from our analysis: at low latitudes, especially in the Indian Ocean and Western Pacific, sea level will likely rise more than the global mean (mostly by 10–20%. Around the northeastern Atlantic and the northeastern Pacific coasts, sea level will rise less than the global average or, in some rare cases, even fall. In the northwestern Atlantic, along the American coast, a strong dynamic sea level rise is counteracted by gravitational depression due to Greenland ice melt; whether sea level will be above- or below-average will depend on the relative contribution of these two factors. Our regional sea level projections and the diagnosed uncertainties provide an improved basis for coastal impact analysis and infrastructure planning for adaptation to climate change.

  5. Variation of Marine Geoid Due to Ocean Circulation and Sea Level Change

    Science.gov (United States)

    Chu, P. C.

    2017-12-01

    Sea level (S) change and ocean circulation largely affect the gravity field and in turns the marine geoid (N). Difference between the two, D = S - N, is the dynamic ocean topography (DOT), whose gradient represents the large-scale surface geostrophic circulations. Thus, temporal variability of marine geoid (δN) is caused by the sea level change (δS) and the DOT variation (δD), δN = δS - δD. Here, δS is identified from temporally varying satellite altimeter measures; δD is calculated from the change of DOT. For large-scale processes with conservation of potential vorticity, the geostrophic flows take minimum energy state. Based on that, a new elliptic equation is derived in this study to determine D. Here, H is the water depth; and (X, Y) are forcing functions calculated from the in-situ density. The well-posed elliptic equation is integrated numerically on 1o grids for the world oceans with the boundary values taken from the mean DOT (1993-2006) field at the NASA/JPL website: https://grace.jpl.nasa.gov/data/get-data/dynamic-ocean-typography/, the forcing function F calculated from the three-dimensional temperature and salinity of the NOAA National Centers for Environmental Information (NCEI) World Ocean Atlas 2013 version 2, and sea-floor topography (H) from the NOAA ETOPO5. The numerical solution compares reasonably well (relative root mean square difference of 0.09) with the NASA/JPL satellite observation of the difference between the time-averaged sea surface height and the geoid. In-situ ocean measurements of temperature, salinity, and velocity have also rapidly advanced such that the global ocean is now continuously monitored by near 4,000 free-drifting profiling floats (called Argo) from the surface to 2000 m depth with all data being relayed and made publicly available within hours after collection (http://www.argo.ucsd.edu/). This provides a huge database of temperature and salinity and in turns the forcing function F for the governing elliptic

  6. Greenhouse effect, sea level rise, and coastal drainage systems

    Energy Technology Data Exchange (ETDEWEB)

    Titus, J G; Kuo, C Y; Gibbs, M J; LaRoche, T B; Webb, M K; Waddell, J O

    1987-01-01

    Increasing concentrations of carbon dioxide and other gases are expected to warm the earth several degrees in the next century, which would raise sea level a few feet and alter precipitation patterns. Both of these changes would have major impacts on the operation of coastal drainage systems. However, because sea level rise and climate change resulting from the greenhouse effect are still uncertain, most planners and engineers are ignoring the potential implications. Case studies of the potential impact on watersheds in Charleston, South Carolina, and Fort Walton Beach, Florida, suggest that the cost of designing a new system to accommodate a rise in sea level will sometimes be small compared with the retrofit cost that may ultimately be necessary if new systems are not designed for a rise. Rather than ignore the greenhouse effect until its consequences are firmly established, engineers and planners should evaluate whether it would be worthwhile to insure that new systems are not vulnerable to the risks of climate change and sea level rise.

  7. Ancient Maritime Fish-Traps of Brittany (France): A Reappraisal of the Relationship Between Human and Coastal Environment During the Holocene

    Science.gov (United States)

    Langouët, Loïc; Daire, Marie-Yvane

    2009-12-01

    The present-day maritime landscape of Western France forms the geographical framework for a recent research project dedicated to the archaeological study of ancient fish-traps, combining regional-scale and site-scale investigations. Based on the compilation and exploitation of a large unpublished dataset including more than 550 sites, a preliminary synthetic study allows us to present some examples of synchronic and thematic approaches, and propose a morphological classification of the weirs. These encouraging first results open up new perspectives on fish-trap chronology closely linked to wider studies on Holocene sea-level changes.

  8. A Holocene progradation record from Okains Bay, Banks Peninsula, Canterbury, New Zealand

    International Nuclear Information System (INIS)

    Stephenson, W.; Shulmeister, J.

    1999-01-01

    Fifty-eight distinct ridges are preserved on the Holocene progradation plain in Okains Bay, Banks Peninsula, Canterbury. Of these, 48 represent beach berm and foredune complexes and the remaining 10 are transverse dune ridges. Periods of rapid coastal progradation are marked by multiple beach berm preservation, whereas intervening periods of lower sediment accumulation result in a stable coastline and transverse dune formation. Infilling of the bay began following sea-level stabilisation in the mid Holocene. The fill is dominantly fine sand, which is derived from sediment carried around Banks Peninsula in the Southland Current and washed into Okains Bay by wave action. Variations in the progradation rate are therefore proxy indicators of coastal erosion in the Canterbury Bight. We demonstrate that there is little progradational fill preserved between c. 6500 and 2000 yr BP. This implies significant changes in sediment delivery to the Southland Current within the last 2000 yr, which we attribute to increased coastal erosion in South Canterbury. We speculate that this increasing erosion resulted from increased wave energy regimes, which in turn may relate to increasing Southern Hemisphere seasonality following the precessional cycle. (author). 32 refs., 4 figs., 3 tabs

  9. Limits on the adaptability of coastal marshes to rising sea level

    Science.gov (United States)

    Kirwan, Matthew L.; Guntenspergen, Glenn R.; D'Alpaos, Andrea; Morris, James T.; Mudd, Simon M.; Temmerman, Stijn

    2010-01-01

    Assumptions of a static landscape inspire predictions that about half of the world's coastal wetlands will submerge during this century in response to sea-level acceleration. In contrast, we use simulations from five numerical models to quantify the conditions under which ecogeomorphic feedbacks allow coastal wetlands to adapt to projected changes in sea level. In contrast to previous sea-level assessments, we find that non-linear feedbacks among inundation, plant growth, organic matter accretion, and sediment deposition, allow marshes to survive conservative projections of sea-level rise where suspended sediment concentrations are greater than ~20 mg/L. Under scenarios of more rapid sea-level rise (e.g., those that include ice sheet melting), marshes will likely submerge near the end of the 21st century. Our results emphasize that in areas of rapid geomorphic change, predicting the response of ecosystems to climate change requires consideration of the ability of biological processes to modify their physical environment.

  10. Vertical ground motion and historical sea-level records in Dakar (Senegal)

    International Nuclear Information System (INIS)

    Le Cozannet, Gonéri; Raucoules, Daniel; Garcin, Manuel; Lavigne, Franck; Wöppelmann, Guy; Gravelle, Médéric; Da Sylva, Sylvestre; Meyssignac, Benoit

    2015-01-01

    With growing concerns regarding future impacts of sea-level in major coastal cities, the most accurate information is required regarding local sea-level changes with respect to the coast. Besides global and regional sea-level changes, local coastal vertical ground motions can substantially contribute to local changes in sea-level. In some cases, such ground motions can also limit the usefulness of tide-gauge records, which are a unique source of information to evaluate global sea-level changes before the altimetry era. Using satellite synthetic aperture radar interferometry, this study aims at characterizing vertical coastal ground motion in Dakar (Senegal), where a unique century-long record in Africa has been rediscovered. Given the limited number of available images, we use a stacking procedure to compute ground motion velocities in the line of sight over 1992–2010. Despite a complex geology and a rapid population growth and development, we show that the city as a whole is unaffected by differential ground motions larger than 1 mm year −1 . Only the northern part of the harbor displays subsidence patterns after 2000, probably as a consequence of land reclamation works. However, these ground motions do not affect the historical tide gauge. Our results highlight the value of the historical sea-level records of Dakar, which cover a 100 year time-span in a tropical oceanic region of Africa, where little data are available for past sea-level reconstructions. (letter)

  11. Microfaunal analysis of late Quaternary deposits of the northern Bering Sea.

    Science.gov (United States)

    McDougall, K.

    1982-01-01

    Holocene microfaunal associations and distribution patterns define three inner-shelf (1-20m) biofacies in Norton Sound, northern Bering Sea. The Holocene facies relations are the basis for interpreting early Holocene and late Pleistocene environmental conditions in the NE Bering Sea area. Norton Sound cores provide evidence of two marine transgressions and a varying river input.-from Author

  12. Mean sea level and change in the hydrological regime off Loviisa power plant around the year 2050

    International Nuclear Information System (INIS)

    Maelkki, P.; Voipio, A.

    1985-03-01

    On the request of Imatran Voima Oy, the Institute of Marine Research has made an estimate on the future sea level off Loviisa Power Plant. The estimate is based on observationsof mean sea level in the Gulf of Finland. The stations used are Helsinki (observations since 1904) and Hamina (observations since 1928). A litterature review was made in order to estimate impact of climate change on environmental conditions. The results presented are mainly based on various estimates of meterorological Global Circulation Models (GCM). Their usefulness in the connection is briefly discussed

  13. Arctic Sea Level Reconstruction

    DEFF Research Database (Denmark)

    Svendsen, Peter Limkilde

    Reconstruction of historical Arctic sea level is very difficult due to the limited coverage and quality of tide gauge and altimetry data in the area. This thesis addresses many of these issues, and discusses strategies to help achieve a stable and plausible reconstruction of Arctic sea level from...... 1950 to today.The primary record of historical sea level, on the order of several decades to a few centuries, is tide gauges. Tide gauge records from around the world are collected in the Permanent Service for Mean Sea Level (PSMSL) database, and includes data along the Arctic coasts. A reasonable...... amount of data is available along the Norwegian and Russian coasts since 1950, and most published research on Arctic sea level extends cautiously from these areas. Very little tide gauge data is available elsewhere in the Arctic, and records of a length of several decades,as generally recommended for sea...

  14. Sea level ~400 000 years ago (MIS 11: analogue for present and future sea-level?

    Directory of Open Access Journals (Sweden)

    D. Q. Bowen

    2010-01-01

    Full Text Available Comparison of the sea-level today with that of 400 000 years ago (MIS 11, when the Earth's orbital characteristics were similar may provide, under conditions of natural variability, indications of future sea-level during the present interglacial. Then, as now, orbital eccentricity was low and precession dampened. Evidence for MIS 11 sea-level occurs on uplifting coastlines where shorelines with geochronological ages have been preserved. The sea-level term and the uplift term may be separated with an "uplift correction" formula. This discovers the original sea-level at which the now uplifted shoreline was fashioned. Estimates are based on average uplift rates of the "last interglacial" sea-level (MIS 5.5 using a range of estimates for sea-level and age at that time at different locations. These, with varying secular tectonic regimes in different ocean basins, provide a band of estimates for the MIS 11 sea-level. They do not support the hypothesis of an MIS 11 sea-level at ~20 m, and instead show that it was closer to its present level.

  15. Current and sea-level signals in periplatform ooze (Neogene, Maldives, Indian Ocean)

    Science.gov (United States)

    Betzler, Christian; Lüdmann, Thomas; Hübscher, Christian; Fürstenau, Jörn

    2013-05-01

    Periplatform ooze is an admixture of pelagic carbonate and sediment derived from neritic carbonate platforms. Compositional variations of periplatform ooze allow the reconstruction of past sea-level changes. Periplatform ooze formed during sea-level highstands is finer grained and richer in aragonite through the elevated input of material from the flooded platform compared to periplatform ooze formed during the episodes of lowered sea level. In many cases, however, the sea floor around carbonate platforms is subjected to bottom currents which are expected to affect sediment composition, i.e. through winnowing of the fine fraction. The interaction of sea-level driven highstand shedding and current impact on the formation of periplatform ooze has hitherto not been analyzed. To test if a sea-level driven input signal in periplatform ooze is influenced or even distorted by changing current activity, an integrated study using seismic, hydroacoustic and sedimentological data has been performed on periplatform ooze deposited in the Inner Sea of the Maldives. The Miocene to Pleistocene succession of drift deposits is subdivided into nine units; limits of seismostratigraphic units correspond to changes or turnarounds in grain size trends in cores recovered at ODP Site 716 and NEOMA Site 1143. For the Pleistocene it can be shown how changes in grain size occur in concert with sea-level changes and changes of the monsoonal system, which is thought to be a major driver of bottom currents in the Maldives. A clear highstand shedding pattern only appears in the data at a time of relaxation of monsoonal strength during the last 315 ky. Results imply (1) that drift sediments provide a potential target for analyzing past changes in oceanic currents and (2) that the ooze composition bears a mixed signal of input and physical winnowing at the sea floor.

  16. Novel sedimentological fingerprints link shifting depositional processes to Holocene climate transitions in East Greenland

    Science.gov (United States)

    van der Bilt, Willem G. M.; Rea, Brice; Spagnolo, Matteo; Roerdink, Desiree L.; Jørgensen, Steffen L.; Bakke, Jostein

    2018-05-01

    The Arctic warms faster than any other region of our planet. Besides melting glaciers, thawing permafrost and decreasing sea-ice, this amplified response affects earth surface processes. This geomorphological expression of climate change may alter landscapes and increase the frequency and magnitude of geohazards like floods or mass-movements. Beyond the short span of sparse monitoring time series, geological archives provide a valuable long-term context for future risk assessment. Lake sediment sequences are particularly promising in this respect as continuous recorders of surface process change. Over the past decade, the emergence of new techniques that characterize depositional signatures in more detail has enhanced this potential. Here, we present a well-dated Holocene-length lake sediment sequence from Ammassalik Island on southeast Greenland. This area is particularly sensitive to regional shifts in the Arctic climate system due to its location near the sea-ice limit, the Greenland Ice Sheet and the convergence of polar and Atlantic waters. The expression of Holocene change is fingerprinted using physical (grain size, organic content, density), visual (3-D Computed Tomography) and geochemical (X-Ray Fluorescence, X-Ray Diffraction) evidence. We show that three sharp transitions characterize the Holocene evolution of Ymer Lake. Between 10 and 9.5 cal. ka BP, rapid local glacier loss from the lake catchment culminated in an outburst flood. Following a quiescent Holocene climatic optimum, Neoglacial cooling, lengthening lake ice cover and shifting wind patterns prompted in-lake avalanching of sediments from 4.2 cal. ka BP onwards. Finally, glaciers reformed in the catchment around 1.2 cal. ka BP. The timing of these shifts is consistent with the regional expression of deglaciation, Neoglacial cooling and Little Ice Age-type glacier growth, respectively. The novel multi-proxy approach applied in this study rigorously links depositional sediment signatures to

  17. Importance of flexure in response to sedimentation and erosion along the US Atlantic passive margin in reconciling sea level change and paleoshorelines

    Science.gov (United States)

    Moucha, R.; Ruetenik, G.; de Boer, B.

    2017-12-01

    Reconciling elevations of paleoshorelines along the US Atlantic passive margin with estimates of eustatic sea level have long posed to be a challenge. Discrepancies between shoreline elevation and sea level have been attributed to combinations of tectonics, glacial isostatic adjustment, mantle convection, gravitation and/or errors, for example, in the inference of eustatic sea level from the marine 18O record. Herein we present a numerical model of landscape evolution combined with sea level change and solid Earth deformations to demonstrate the importance of flexural effects in response to erosion and sedimentation along the US Atlantic passive margin. We quantify these effects using two different temporal models. One reconciles the Orangeburg scarp, a well-documented 3.5 million-year-old mid-Pliocene shoreline, with a 15 m mid-Pliocene sea level above present-day (Moucha and Ruetenik, 2017). The other model focuses on the evolution of the South Carolina and northern Georgia margin since MIS 11 ( 400 Ka) using a fully coupled ice sheet, sea level and solid Earth model (de Boer et al, 2014) while relating our results to a series of enigmatic sea level high stand markers. de Boer, B., Stocci, P., and van de Wal, R. (2014). A fully coupled 3-d ice-sheet-sea-level model: algorithm and applications. Geoscientific Model Development, 7:2141-2156. Moucha, R. and Ruetenik, G. A. (2017). Interplay between dynamic topography and flexure along the US Atlantic passive margin: Insights from landscape evolution modeling. Global and Planetary Change, 149: 72-78

  18. Spatial sea-level reconstruction in the Baltic Sea and in the Pacific Ocean from tide gauges observations

    Directory of Open Access Journals (Sweden)

    Marco Olivieri

    2016-07-01

    Full Text Available Exploiting the Delaunay interpolation, we present a newly implemented 2-D sea-level reconstruction from coastal sea-level observations to open seas, with the aim of characterizing the spatial variability of the rate of sea-level change. To test the strengths and weaknesses of this method and to determine its usefulness in sea-level interpolation, we consider the case studies of the Baltic Sea and of the Pacific Ocean. In the Baltic Sea, a small basin well sampled by tide gauges, our reconstructions are successfully compared with absolute sea-level observations from altimetry during 1993-2011. The regional variability of absolute sea level observed across the Pacific Ocean, however, cannot be reproduced. We interpret this result as the effect of the uneven and sparse tide gauge data set and of the composite vertical land movements in and around the region. Useful considerations arise that can serve as a basis for developing sophisticated approaches.

  19. Geomorphic expression of late Quaternary sea level changes along ...

    Indian Academy of Sciences (India)

    Department of Geology, Faculty of Science, M. S. University of Baroda, Vadodara 390 002, India. ∗ e-mail: ... referred to as miliolite limestone and shell lime- stone that form coastal ... the bed rocks and corresponding to the prevailing sea level.

  20. Antarctica and Global Environmental Change - Lessons from the Past Inform Climate Change Policy Today

    Science.gov (United States)

    Dunbar, R. B.; Scientific Team Of Odp Drilling Leg 318; Andrill Science Team

    2011-12-01

    of radiative forcing, is strong at all timescales. It also appears that we are committed to the attainment of pCO2 levels within the next several decades that in the past were associated with substantial reductions in Antarctic glacial ice volume, and hence significant amounts of global sea level rise. New and detailed studies of past warm intervals as well as the most recent deglaciation reveal the potential for century-scale (or even more rapid) melt events. A new ultra-high resolution record of East Antarctic climate change extending to the most recent deglaciation reveals unusually large climatic excursions in both the earliest Holocene and mid-Holocene. Taken together, the paleoclimate record derived from geological drilling in Antarctica should be taken by policymakers as substantial and credible new evidence of increased risk of dangerous climate change in the decades and century ahead.

  1. Age of the last glaciation of Vestfold Hills and significance for sea level change

    International Nuclear Information System (INIS)

    Gore, D.B.; Colhoun, E.A.

    1998-01-01

    The Vestfold Hills form the second largest deglaciated oasis area in East Antarctica. The last time that the oasis was submerged by the East Antarctic ice sheet as it extended onto the continental shelf has been termed the ''Vestfold Glaciation'' (Adamson and Pickard 1986). To date the Vestfold Glaciation has been assumed to correlate with the late Wisconsin Glaciation on the basis of Holocene radiocarbon dates obtained from marine deposits in the inlets and from derived sediments ice-proximal to the margin of the Sorsdal Glacier (Adamson and Pickard 1986; Fitsimons and Dormack 1993). Radiocarbon dating of shell fragments from Vestfold till deposits distributed throughout the southern and seaward parts of the oasis have given assays from 31.1 to .43.7k yr BP. If the assays represent true ages of the time of growth of the marine shells then it would appear that the Vestfold Glaciation ice expansion onto the continental shelf post-dates 31 k yr and the glaciation is equivalent to the late Wisconsin. Similarly, if the range of assays represents true ages then the fiords must have been occupied by the sea during late middle Wisconsin time, presumably when the continental margin was isostatically depressed below present level. There is, however, the possibility that the assays are minimal, and being derived into till from older marine deposits they could have true greater and mixed ages. This alternative is being explored

  2. Future sea level rise constrained by observations and long-term commitment

    Science.gov (United States)

    Mengel, Matthias; Levermann, Anders; Frieler, Katja; Robinson, Alexander; Marzeion, Ben; Winkelmann, Ricarda

    2016-01-01

    Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28–56 cm, 37–77 cm, and 57–131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The “constrained extrapolation” approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with process-based projections. PMID:26903648

  3. Future sea level rise constrained by observations and long-term commitment.

    Science.gov (United States)

    Mengel, Matthias; Levermann, Anders; Frieler, Katja; Robinson, Alexander; Marzeion, Ben; Winkelmann, Ricarda

    2016-03-08

    Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28-56 cm, 37-77 cm, and 57-131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The "constrained extrapolation" approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with process-based projections.

  4. Geochemical characteristics of Holocene laminated sapropel (unit II) and underlying lacustrine unit III in the Black Sea

    Science.gov (United States)

    Dean, Walter E.; Arthur, Michael A.

    2011-01-01

    eg 1 of the 1988 R/V Knorr expeditions to the Black Sea recovered 90 gravity and box cores. The longest recovery by gravity cores was about 3 meters, with an average of about 2.5 meters, recovering all of the Holocene and upper Pleistocene sections in the Black Sea. During the latest Pleistocene glaciation, sea level dropped below the 35-meters-deep Bosporus outlet sill of the Black Sea. Therefore throughout most of its history the Black Sea was a lake, and most of its sediments are lacustrine. The oldest sediments recovered (older than 8,000 calendar years) consist of massive to coarsely banded lacustrine calcareous clay designated as lithologic Unit III, generally containing less than 1 percent organic carbon (OC). The base of overlying Unit II marks the first incursion of Mediterranean seawater into the Black Sea, and the onset of bottom-water anoxia about 7,900 calendar years. Unit II contains as much as 15 percent OC in cores from the deepest part of the Black Sea (2,200 meters). The calcium carbonate (CaCO3) remains of the coccolith Emiliania huxleyi form the distinctive white laminae of overlying Unit I. The composition of Unit III and Unit II sediments are quite different, reflecting different terrigenous clastic sources and increased contributions from hydrogenous and biogenic components in anoxic Unit II sapropel. In Unit II, positive covariance between OC and three trace elements commonly concentrated in OC-rich sediments where sulfate reduction has occurred (molybdenum, nickel, and vanadium) and a nutrient (phosphorus) suggest a large marine source for these elements although nickel and vanadium also have a large terrigenous clastic source. The marine sources may be biogenic or hydrogenous. A large biogenic source is also suggested for copper and cobalt. Because abundant pyrite forms in the water column and sediments of the Black Sea, we expected to find a large hydrogenous iron component, but a strong covariance of iron with aluminum suggests that the

  5. Skill and reliability of climate model ensembles at the Last Glacial Maximum and mid-Holocene

    Directory of Open Access Journals (Sweden)

    J. C. Hargreaves

    2013-03-01

    Full Text Available Paleoclimate simulations provide us with an opportunity to critically confront and evaluate the performance of climate models in simulating the response of the climate system to changes in radiative forcing and other boundary conditions. Hargreaves et al. (2011 analysed the reliability of the Paleoclimate Modelling Intercomparison Project, PMIP2 model ensemble with respect to the MARGO sea surface temperature data synthesis (MARGO Project Members, 2009 for the Last Glacial Maximum (LGM, 21 ka BP. Here we extend that work to include a new comprehensive collection of land surface data (Bartlein et al., 2011, and introduce a novel analysis of the predictive skill of the models. We include output from the PMIP3 experiments, from the two models for which suitable data are currently available. We also perform the same analyses for the PMIP2 mid-Holocene (6 ka BP ensembles and available proxy data sets. Our results are predominantly positive for the LGM, suggesting that as well as the global mean change, the models can reproduce the observed pattern of change on the broadest scales, such as the overall land–sea contrast and polar amplification, although the more detailed sub-continental scale patterns of change remains elusive. In contrast, our results for the mid-Holocene are substantially negative, with the models failing to reproduce the observed changes with any degree of skill. One cause of this problem could be that the globally- and annually-averaged forcing anomaly is very weak at the mid-Holocene, and so the results are dominated by the more localised regional patterns in the parts of globe for which data are available. The root cause of the model-data mismatch at these scales is unclear. If the proxy calibration is itself reliable, then representativity error in the data-model comparison, and missing climate feedbacks in the models are other possible sources of error.

  6. Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi, Vietnam

    Science.gov (United States)

    Kuroda, Keisuke; Hayashi, Takeshi; Funabiki, Ayako; Do, An Thuan; Canh, Vu Duc; Nga, Tran Thi Viet; Takizawa, Satoshi

    2017-06-01

    Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25-40 m depth, 9.6-4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25-94 μg/L) than in the HUA (5.2-42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.

  7. Extreme storms, sea level rise, and coastal change: implications for infrastructure reliability in the Gulf of Mexico

    Science.gov (United States)

    Anarde, K.; Kameshwar, S.; Irza, N.; Lorenzo-Trueba, J.; Nittrouer, J. A.; Padgett, J.; Bedient, P. B.

    2016-12-01

    Predicting coastal infrastructure reliability during hurricane events is important for risk-based design and disaster planning, such as delineating viable emergency response routes. Previous research has focused on either infrastructure vulnerability to coastal flooding or the impact of changing sea level and landforms on surge dynamics. Here we investigate the combined impact of sea level, morphology, and coastal flooding on the reliability of highway bridges - the only access points between barrier islands and mainland communities - during future extreme storms. We forward model coastal flooding for static projections of geomorphic change using ADCIRC+SWAN. First-order parameters that are adjusted include sea level and elevation. These are varied for each storm simulation to evaluate relative impact on the reliability of bridges surrounding Freeport, TX. Simulated storms include both synthetic and historical events, which are classified by intensity using the storm's integrated kinetic energy, a metric for surge generation potential. Reliability is estimated through probability of failure - given wave and surge loads - and time inundated. Findings include that: 1) bridge reliability scales inversely with surge height, and 2) sea level rise reduces bridge reliability due to a monotonic increase in surge height. The impact of a shifting landscape on bridge reliability is more complex: barrier island rollback can increase or decrease inundation times for storms of different intensity due to changes in wind-setup and back-barrier bay interactions. Initial storm surge readily inundates the coastal landscape during large intensity storms, however the draining of inland bays following storm passage is significantly impeded by the barrier. From a coastal engineering standpoint, we determine that to protect critical infrastructure, efforts now implemented that nourish low-lying barriers may be enhanced by also armoring back-bay coastlines and elevating bridge approach

  8. Assessment of Hammocks (Petenes) Resilience to Sea Level Rise Due to Climate Change in Mexico

    Science.gov (United States)

    Posada Vanegas, Gregorio; de Jong, Bernardus H. J.

    2016-01-01

    There is a pressing need to assess resilience of coastal ecosystems against sea level rise. To develop appropriate response strategies against future climate disturbances, it is important to estimate the magnitude of disturbances that these ecosystems can absorb and to better understand their underlying processes. Hammocks (petenes) coastal ecosystems are highly vulnerable to sea level rise linked to climate change; their vulnerability is mainly due to its close relation with the sea through underground drainage in predominantly karstic soils. Hammocks are biologically important because of their high diversity and restricted distribution. This study proposes a strategy to assess resilience of this coastal ecosystem when high-precision data are scarce. Approaches and methods used to derive ecological resilience maps of hammocks are described and assessed. Resilience models were built by incorporating and weighting appropriate indicators of persistence to assess hammocks resilience against flooding due to climate change at “Los Petenes Biosphere Reserve”, in the Yucatán Peninsula, Mexico. According to the analysis, 25% of the study area is highly resilient (hot spots), whereas 51% has low resilience (cold spots). The most significant hot spot clusters of resilience were located in areas distant to the coastal zone, with indirect tidal influence, and consisted mostly of hammocks surrounded by basin mangrove and floodplain forest. This study revealed that multi-criteria analysis and the use of GIS for qualitative, semi-quantitative and statistical spatial analyses constitute a powerful tool to develop ecological resilience maps of coastal ecosystems that are highly vulnerable to sea level rise, even when high-precision data are not available. This method can be applied in other sites to help develop resilience analyses and decision-making processes for management and conservation of coastal areas worldwide. PMID:27611802

  9. Compilation of information on the climate and evaluation of the hydrochemical and isotopic composition during Late Pleistocene and Holocene

    International Nuclear Information System (INIS)

    Andersson, Cecilia

    1998-01-01

    This report summarises and evaluates some of the existing information on the Late Pleistocene and Holocene climates, i.e. the last 130 000 years. An estimation of the conditions at the Aespoe island (southeast Sweden) has also been made during this time span. The knowledge about Late Pleistocene (Eemian Interglacial and Weichselian glacial) is not yet fully understood. There are still a lot of assumptions concerning this period and more information is needed to be able to establish the climatic conditions. This is not the case for the Weichselian deglaciation and the present interglacial, Holocene, for which the environmental conditions are quite certain. It has been concluded, however, that the Eemian climatic development probably was similar to the Holocene but perhaps somewhat warmer and more humid. The Eemian Baltic Sea level was probably also higher than the present Baltic Sea level and there was a connection between it and the White Sea in the northeast. Aespoe was probably situated below sea level during the greater part of Eemian. Not much is known about the last glacial period, the Weichselian glaciation, until the final deglaciation. The ice sheet during Early Weichselian was probably mostly concentrated to the Scandinavian mountain area and in northern Scandinavia. At least two intervals with higher temperatures have been recorded, the Broerup and Odderade interstadials. The Middle Weichselian substage is characterised by fluctuations, melting and re-advances. Aespoe was probably not glaciated until the middle or latter part of Middle Weichselian. The maximum extension of the Weichselian ice sheet occurred in Late Weichselian, around 20 to 18 ka BP, which was succeeded by the final deglaciation. The retreat of the Weichselian ice sheet is described by for example end moraines and glacial varved clay. The Aespoe area was glaciated until 12 500 BP. Huge quantities of glacial meltwater was released into the Baltic basin as the ice receded. Due to different

  10. Compilation of information on the climate and evaluation of the hydrochemical and isotopic composition during Late Pleistocene and Holocene

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Cecilia [Intera KB (Sweden)

    1998-01-01

    This report summarises and evaluates some of the existing information on the Late Pleistocene and Holocene climates, i.e. the last 130 000 years. An estimation of the conditions at the Aespoe island (southeast Sweden) has also been made during this time span. The knowledge about Late Pleistocene (Eemian Interglacial and Weichselian glacial) is not yet fully understood. There are still a lot of assumptions concerning this period and more information is needed to be able to establish the climatic conditions. This is not the case for the Weichselian deglaciation and the present interglacial, Holocene, for which the environmental conditions are quite certain. It has been concluded, however, that the Eemian climatic development probably was similar to the Holocene but perhaps somewhat warmer and more humid. The Eemian Baltic Sea level was probably also higher than the present Baltic Sea level and there was a connection between it and the White Sea in the northeast. Aespoe was probably situated below sea level during the greater part of Eemian. Not much is known about the last glacial period, the Weichselian glaciation, until the final deglaciation. The ice sheet during Early Weichselian was probably mostly concentrated to the Scandinavian mountain area and in northern Scandinavia. At least two intervals with higher temperatures have been recorded, the Broerup and Odderade interstadials. The Middle Weichselian substage is characterised by fluctuations, melting and re-advances. Aespoe was probably not glaciated until the middle or latter part of Middle Weichselian. The maximum extension of the Weichselian ice sheet occurred in Late Weichselian, around 20 to 18 ka BP, which was succeeded by the final deglaciation. The retreat of the Weichselian ice sheet is described by for example end moraines and glacial varved clay. The Aespoe area was glaciated until 12 500 BP. Huge quantities of glacial meltwater was released into the Baltic basin as the ice receded. Due to different

  11. Precession and atmospheric CO2 modulated variability of sea ice in the central Okhotsk Sea since 130,000 years ago

    Science.gov (United States)

    Lo, Li; Belt, Simon T.; Lattaud, Julie; Friedrich, Tobias; Zeeden, Christian; Schouten, Stefan; Smik, Lukas; Timmermann, Axel; Cabedo-Sanz, Patricia; Huang, Jyh-Jaan; Zhou, Liping; Ou, Tsong-Hua; Chang, Yuan-Pin; Wang, Liang-Chi; Chou, Yu-Min; Shen, Chuan-Chou; Chen, Min-Te; Wei, Kuo-Yen; Song, Sheng-Rong; Fang, Tien-Hsi; Gorbarenko, Sergey A.; Wang, Wei-Lung; Lee, Teh-Quei; Elderfield, Henry; Hodell, David A.

    2018-04-01

    Recent reduction in high-latitude sea ice extent demonstrates that sea ice is highly sensitive to external and internal radiative forcings. In order to better understand sea ice system responses to external orbital forcing and internal oscillations on orbital timescales, here we reconstruct changes in sea ice extent and summer sea surface temperature (SSST) over the past 130,000 yrs in the central Okhotsk Sea. We applied novel organic geochemical proxies of sea ice (IP25), SSST (TEX86L) and open water marine productivity (a tri-unsaturated highly branched isoprenoid and biogenic opal) to marine sediment core MD01-2414 (53°11.77‧N, 149°34.80‧E, water depth 1123 m). To complement the proxy data, we also carried out transient Earth system model simulations and sensitivity tests to identify contributions of different climatic forcing factors. Our results show that the central Okhotsk Sea was ice-free during Marine Isotope Stage (MIS) 5e and the early-mid Holocene, but experienced variable sea ice cover during MIS 2-4, consistent with intervals of relatively high and low SSST, respectively. Our data also show that the sea ice extent was governed by precession-dominated insolation changes during intervals of atmospheric CO2 concentrations ranging from 190 to 260 ppm. However, the proxy record and the model simulation data show that the central Okhotsk Sea was near ice-free regardless of insolation forcing throughout the penultimate interglacial, and during the Holocene, when atmospheric CO2 was above ∼260 ppm. Past sea ice conditions in the central Okhotsk Sea were therefore strongly modulated by both orbital-driven insolation and CO2-induced radiative forcing during the past glacial/interglacial cycle.

  12. A new phase in the production of quality-controlled sea level data

    DEFF Research Database (Denmark)

    Quartly, Graham D.; Legeais, Jean François; Ablain, Michaël

    2017-01-01

    Sea level is an essential climate variable (ECV) that has a direct effect on many people through inundations of coastal areas, and it is also a clear indicator of climate changes due to external forcing factors and internal climate variability. Regional patterns of sea level change inform us...... and predict these phenomena, and thereby alleviate some of the environmental conditions associated with them. All such studies rely on the existence of long-term consistent high-accuracy datasets of sea level. The Climate Change Initiative (CCI) of the European Space Agency was established in 2010 to provide...... improved time series of some ECVs, including sea level, with the purpose of providing such data openly to all to enable the widest possible utilisation of such data. Now in its second phase, the Sea Level CCI project (SL-cci) merges data from nine different altimeter missions in a clear, consistent...

  13. Examining the interplay of climate and low amplitude sea-level change on the distribution and volume of massive dolomitization: Zebbag Formation, Cretaceous, Southern Tunisia

    DEFF Research Database (Denmark)

    Newport, Richard; Hollis, Cathy; Bodin, Stéphane

    2017-01-01

    During the Cretaceous, a humid global climate, calcitic seas, high relative sea-level and low amplitude changes in relative sea-level largely prevented large-scale dolomitization in many carbonate successions. However, the well-exposed shallow-water carbonate sediments of the Upper Albian–Lower T...

  14. Holocene Tree Line and Climate Change on the Queen Charlotte Islands, Canada

    Science.gov (United States)

    Pellatt, Marlow G.; Mathewes, Rolf W.

    1997-07-01

    Palynological study of two subalpine ponds on the Queen Charlotte Islands reveals changes in tree line and climate during the Holocene. The findings agree with previous reconstructions, from nearby Louise Pond on the Queen Charlotte Islands, that suggest a warmer-than-present climate and higher-than-present tree lines in the early Holocene (ca. 9600-6600 14C yr B.P.). Basal ages at SC1 Pond and Shangri-La Bog indicate that the basins did not hold permanent water before 7200 14C yr B.P., consistent with a warmer and drier early Holocene previously inferred from Louise Pond. Pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 ± 90 14C yr B.P., similar to the 5790 ± 130 14C yr B.P. age for cooling inferred from Louise Pond. Conditions similar to present were established at SC1 Pond by 3460 ± 100 14C yr B.P., confirming the previous estimate of 3400 14C yr B.P. at Louise Pond. This 3400 14C yr B.P. vegetation shift on the Queen Charlotte Islands corresponds with the beginning of the Tiedemann glacial advance in the south-coastal mountains of British Columbia (ca. 3300 14C yr B.P.), the Peyto and Robson glacial advances between 3300 and 2800 14C yr B.P. in the Rocky Mountains, and climatic cooling inferred from palynological studies throughout southern British Columbia, northern Washington, and southeast Alaska. These findings confirm that changes in regional climate influenced changes in vegetation in coastal British Columbia.

  15. LATE GLACIAL AND HOLOCENE ENVIRONMENTAL CHANGE INFERRED FROM THE PÁRAMO OF CAJANUMA IN THE PODOCARPUS NATIONAL PARK, SOUTHERN ECUADOR

    Directory of Open Access Journals (Sweden)

    ANDREA VILLOTA

    2014-12-01

    Full Text Available To reconstruct the environmental history including vegetation, fire and climate dynamics, from the Cajanuma valley area ( 3285 m elevation in the Podocarpus National Park, southern Ecuador , we address the following major research question: (1 How did the mountain vegetation developed during the late Glacial and Holocene? (2 Did fire played an important control on the vegetation change and was it natural or of anthropogenic origin?. Palaeoenvironmental changes were investigated using multiple proxies such as pollen, spores, charcoal analyses and radiocarbon dating. Pollen data indicated that during the late Glacial and transition to the early Holocene (ca. 16 000-10 500 cal yr BP herb páramo was the main vegetation type around the study area, while subpáramo and mountain rainforest were scarcely represented. The early and mid-Holocene (ca. 10 500 to 5600 cal yr BP is marked by high abundance of páramo during the early Holocene followed by a slight expansion of mountain forest during the mid-Holocene. During the mid- to late Holocene (ca. 5600-1200 cal yr BP there is a significant presence of páramo and subpáramo while Lower Mountain Forest decreased substantially, although, Upper Mountain Forest remained relatively stable during this period. The late Holocene, from ca. 1200 cal yr BP to present, was characterized by páramo; however, mountain forest and subpáramo presented significantly abundance compared to the previous periods. Fires became frequent since the late Holocene. The marked increased local and regional fire intensity during the wetter late Holocene strongly suggests that were of anthropogenic origin. During the late Glacial and early Holocene, the upper forest line was located at low elevations; but shifted slightly upslope to higher elevations during the mid-Holocene.

  16. Timing, cause and consequences of mid-Holocene climate transition in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Naik, Dinesh K.; Nigam, R.; Gaur, A.S.

    -50,000 years cal BP. Radiocarbon 51, 1111-1150. Roberts, N., Brayshaw, D., Kuzucuoglu, C., Perez, R., Sadori, L., 2011. The mid-Holocene climatic transition in the Mediterranean: Causes and consequences. The Holocene 21, 3-13. Ruddiman, W.F., Ellis, E...

  17. How a barrier island may react on a sea-level rise: The Holocene to Recent Rømø barrier island, Danish Wadden Sea

    DEFF Research Database (Denmark)

    Johannessen, Peter N.; Nielsen, Lars H.; Møller, Ingelise

    set up the water level increases considerably and the highest measured water level is 4.9 m above mean sea level. The barrier island is c. 14 km long and c. 4 km wide and is separated from the mainland by a c. 8 km wide lagoon. At the northern and southern parts of the island, tidal inlets occur...... of c. 15 m and a resolution of c. 20–30 cm (Nielsen et al., 2009), and dating of 70 core samples using optically stimulated luminescence (OSL). The area has experienced a relative sea-level rise of c. 15 m during the last c. 8000 years. The Recent tidal amplitude reaches c. 1.8 m. During strong wind...... with a width of 400–1000 m and depths of 7–30 m. Salt marsh areas, up to 2 km wide, are fringing the lagoonal coast of the island. Active eastward migrating aeolian dunes cover large parts of the island. The Rømø barrier island system is a very sand rich system as it receives coast parallel transported sand...

  18. Mechanisms of long-term mean sea level variability in the North Sea

    Science.gov (United States)

    Dangendorf, Sönke; Calafat, Francisco; Øie Nilsen, Jan Even; Richter, Kristin; Jensen, Jürgen

    2015-04-01

    We examine mean sea level (MSL) variations in the North Sea on timescales ranging from months to decades under the consideration of different forcing factors since the late 19th century. We use multiple linear regression models, which are validated for the second half of the 20th century against the output of a state-of-the-art tide+surge model (HAMSOM), to determine the barotropic response of the ocean to fluctuations in atmospheric forcing. We demonstrate that local atmospheric forcing mainly triggers MSL variability on timescales up to a few years, with the inverted barometric effect dominating the variability along the UK and Norwegian coastlines and wind (piling up the water along the coast) controlling the MSL variability in the south from Belgium up to Denmark. However, in addition to the large inter-annual sea level variability there is also a considerable fraction of decadal scale variability. We show that on decadal timescales MSL variability in the North Sea mainly reflects steric changes, which are mostly remotely forced. A spatial correlation analysis of altimetry observations and baroclinic ocean model outputs suggests evidence for a coherent signal extending from the Norwegian shelf down to the Canary Islands. This supports the theory of longshore wind forcing along the eastern boundary of the North Atlantic causing coastally trapped waves to propagate along the continental slope. With a combination of oceanographic and meteorological measurements we demonstrate that ~80% of the decadal sea level variability in the North Sea can be explained as response of the ocean to longshore wind forcing, including boundary wave propagation in the Northeast Atlantic. These findings have important implications for (i) detecting significant accelerations in North Sea MSL, (ii) the conceptual set up of regional ocean models in terms of resolution and boundary conditions, and (iii) the development of adequate and realistic regional climate change projections.

  19. Late Holocene spatio-temporal variability of the south Greenland Ice Sheet and adjacent mountain glaciers

    Science.gov (United States)

    Sinclair, G.; Carlson, A. E.; Rood, D. H.; Axford, Y.

    2017-12-01

    The late Holocene, with its spatially complex pattern of centennial-scale climate variation, is an ideal time period to test the response of the cryosphere to atmospheric and oceanic temperature changes. The south Greenland Ice Sheet (sGrIS), with its proximity to areas of North Atlantic Deep Water formation and a large spectrum of glaciological regimes over a relatively small area, provides an excellent location to examine the spatial heterogeneity of ice-sheet and glacier responses to climate change. Here, we will present 50 Be-10 surface exposure ages from eight moraines in six locations around the margin of the sGrIS. These moraines are located just outboard of historical moraines, and will therefore allow us to constrain the timing of the most extensive prehistoric late-Holocene advance and retreat of ice margins draining the sGrIS and independent valley glaciers. The dataset includes both marine- and land-terminating glaciers draining the sGrIS, the low-altitude Qassimiut lobe, the high-altitude alpine Julianhåb ice cap and isolated valley glaciers. This diverse dataset will allow us to determine to what extent late-Holocene centennial-scale behavior of the ice-sheet and glacier margins were synchronous, perhaps in response to an external climate forcing, or more stochastic, governed instead by local factors such as basal thermal regime, bedrock topography, or microclimates. This has implications for understanding the forcings and responses of cryospheric changes at timescales relevant to human society. In addition to providing context for paleoclimatic and glacial geologic investigations, this work will inform future sea-level projections by providing targets for validating high-resolution ice-sheet and glacier models.

  20. How sea level change mediates genetic divergence in coastal species across regions with varying tectonic and sediment processes.

    Science.gov (United States)

    Dolby, Greer A; Ellingson, Ryan A; Findley, Lloyd T; Jacobs, David K

    2018-02-01

    Plate tectonics and sediment processes control regional continental shelf topography. We examine the genetic consequences of how glacial-associated sea level change interacted with variable nearshore topography since the last glaciation. We reconstructed the size and distribution of areas suitable for tidal estuary formation from the last glacial maximum, ~20 thousand years ago, to present from San Francisco, California, USA (~38°N) to Reforma, Sinaloa, Mexico (~25°N). We assessed range-wide genetic structure and diversity of three codistributed tidal estuarine fishes (California Killifish, Shadow Goby, Longjaw Mudsucker) along ~4,600 km using mitochondrial control region and cytB sequence, and 16-20 microsatellite loci from a total of 524 individuals. Results show that glacial-associated sea level change limited estuarine habitat to few, widely separated refugia at glacial lowstand, and present-day genetic clades were sourced from specific refugia. Habitat increased during postglacial sea level rise and refugial populations admixed in newly formed habitats. Continental shelves with active tectonics and/or low sediment supply were steep and hosted fewer, smaller refugia with more genetically differentiated populations than on broader shelves. Approximate Bayesian computation favoured the refuge-recolonization scenarios from habitat models over isolation by distance and seaway alternatives, indicating isolation at lowstand is a major diversification mechanism among these estuarine (and perhaps other) coastal species. Because sea level change is a global phenomenon, we suggest this top-down physical control of extirpation-isolation-recolonization may be an important driver of genetic diversification in coastal taxa inhabiting other topographically complex coasts globally during the Mid- to Late Pleistocene and deeper timescales. © 2018 John Wiley & Sons Ltd.