WorldWideScience

Sample records for pre-pleistocene climate records

  1. Climate Record Books

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Climate Record Books contain daily, monthly, seasonal, and annual averages, extremes, or occurrences. Most data are sequential by period of record 1871-1910,...

  2. Pleistocene and pre-Pleistocene Begonia speciation in Africa.

    Science.gov (United States)

    Plana, Vanessa; Gascoigne, Angus; Forrest, Laura L; Harris, David; Pennington, R Toby

    2004-05-01

    This paper presents a historical biogeographic analysis of African Begonia based on combined internal transcribed spacer (ITS) and trnL intron sequences. Age range estimates for Begonia in Africa ranged from only 1.5 Ma for some terminal nodes to 27 Ma for basal nodes when the ages of Réunion (2 Ma) andMayotte (5.4 Ma) were used to date the split between Begonia salaziensis and Begonia comorensis. Assuming a more recent origin age for Begonia salaziensis (2 Ma) provided age estimates in other parts of the phylogeny which agreed with patterns observed in other African organisms. A large proportion of the Begonia diversity seen today in Africa is of pre-Pleistocene origin. Species of Pleistocene origin are concentrated in species-rich groups such as sections Loasibegonia, Scutobegonia, and Tetraphila, which have their centre of diversity in western Central Africa. Phylogenetically isolated taxa such as Begonia longipetiolata, Begonia iucunda, and Begonia thomeana date to the late Miocene, a period of extended aridification on the African continent that had severe effects on African rain forest species. A general pattern is identified where phylogenetically isolated species occur outside the main identified rain forest refuges. Endemic species on the island of São Tomé such as Begonia baccata, Begonia molleri, and Begonia subalpestris appear to be palaeoendemics. Of these species, the most recent age estimate is for B. baccata, which is dated at ca. 3 Ma. Therefore, São Tomé appears to have functioned as an important (if previously unrecognised) pre-Pleistocene refuge. On the mainland, areas such as the Massif of Chaillu in Gabon, southern Congo (Brazzaville), and far western areas of Congo (Kinshasa) have played similar roles to São Tomé.

  3. Atmospheric carbon dioxide and the climate record

    Energy Technology Data Exchange (ETDEWEB)

    Ellsaesser, H.W.

    1989-04-01

    This paper is an attempt to provide a summary review of conclusions from previous studies on this subject. Subject headings include: conceptualization of the greenhouse effect, the climatic effect of doubled CO/sub 2/, interpretation of the climatic record, diagnosis of apparent and possible model deficiencies, and the palaeoclimatic record.

  4. A Solar Irradiance Climate Data Record

    Science.gov (United States)

    Coddington, O.; Lean, J. L.; Pilewskie, P.; Snow, M.; Lindholm, D.

    2016-08-01

    We present a new climate data record for total solar irradiance and solar spectral irradiance between 1610 and the present day with associated wavelength and time-dependent uncertainties and quarterly updates. The data record, which is part of the National Oceanic and Atmospheric Administration’s (NOAA) Climate Data Record (CDR) program, provides a robust, sustainable, and scientifically defensible record of solar irradiance that is of sufficient length, consistency, and continuity for use in studies of climate variability and climate change on multiple time scales and for user groups spanning climate modeling, remote sensing, and natural resource and renewable energy industries. The data record, jointly developed by the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP) and the Naval Research Laboratory (NRL), is constructed from solar irradiance models that determine the changes with respect to quiet sun conditions when facular brightening and sunspot darkening features are present on the solar disk where the magnitude of the changes in irradiance are determined from the linear regression of a proxy magnesium (Mg) II index and sunspot area indices against the approximately decade-long solar irradiance measurements of the Solar Radiation and Climate Experiment (SORCE). To promote long-term data usage and sharing for a broad range of users, the source code, the dataset itself, and supporting documentation are archived at NOAA's National Centers for Environmental Information (NCEI). In the future, the dataset will also be available through the LASP Interactive Solar Irradiance Data Center (LISIRD) for user-specified time periods and spectral ranges of interest.

  5. Modern climate challenges and the geological record

    Science.gov (United States)

    Cronin, Thomas M.

    2010-01-01

    Today's changing climate poses challenges about the influence of human activity, such as greenhouse gas emissions and land use changes, the natural variability of Earth's climate, and complex feedback processes. Ice core and instrumental records show that over the last century, atmospheric carbon dioxide (CO2) concentrations have risen to 390 parts per million volume (ppmv), about 40% above pre-Industrial Age concentrations of 280 ppmv and nearly twice those of the last glacial maximum about 22,000 years ago. Similar historical increases are recorded in atmospheric methane (CH4) and nitrous oxide (N2O). There is general agreement that human activity is largely responsible for these trends. Substantial evidence also suggests that elevated greenhouse gas concentrations are responsible for much of the recent atmospheric and oceanic warming, rising sea level, declining Arctic sea-ice cover, retreating glaciers and small ice caps, decreased mass balance of the Greenland and parts of the Antarctic ice sheets, and decreasing ocean pH (ocean "acidification"). Elevated CO2 concentrations raise concern not only from observations of the climate system, but because feedbacks associated with reduced reflectivity from in land and sea ice, sea level, and land vegetation relatively slowly (centuries or longer) to elevated 2 levels. This means that additional human-induced climate change is expected even if the rate of CO2 emissions is reduced or concentrations immediately stabilized.

  6. The fluvial record of climate change.

    Science.gov (United States)

    Macklin, M G; Lewin, J; Woodward, J C

    2012-05-13

    Fluvial landforms and sediments can be used to reconstruct past hydrological conditions over different time scales once allowance has been made for tectonic, base-level and human complications. Field stratigraphic evidence is explored here at three time scales: the later Pleistocene, the Holocene, and the historical and instrumental period. New data from a range of field studies demonstrate that Croll-Milankovitch forcing, Dansgaard-Oeschger and Heinrich events, enhanced monsoon circulation, millennial- to centennial-scale climate variability within the Holocene (probably associated with solar forcing and deep ocean circulation) and flood-event variability in recent centuries can all be discerned in the fluvial record. Although very significant advances have been made in river system and climate change research in recent years, the potential of fluvial palaeohydrology has yet to be fully realized, to the detriment of climatology, public health, resource management and river engineering.

  7. Detecting Urban Warming Signals in Climate Records

    Institute of Scientific and Technical Information of China (English)

    HE Yuting; JIA Gensuo; HU Yonghong; ZHOU Zijiang

    2013-01-01

    Determining whether air temperatures recorded at meteorological stations have been contaminated by the urbanization process is still a controversial issue at the global scale.With support of historical remote sensing data,this study examined the impacts of urban expansion on the trends of air temperature at 69 meteorological stations in Beijing,Tianjin,and Hebei Province over the last three decades.There were significant positive relations between the two factors at all stations.Stronger warming was detected at the meteorological stations that experienced greater urbanization,i.e.,those with a higher urbanization rate.While the total urban area affects the absolute temperature values,the change of the urban area (urbanization rate) likely affects the temperature trend.Increases of approximately 10% in urban area around the meteorological stations likely contributed to the 0.13℃ rise in air temperature records in addition to regional climate warming.This study also provides a new approach to selecting reference stations based on remotely sensed urban fractions.Generally,the urbanization-induced warming contributed to approximately 44.1% of the overall warming trends in the plain region of study area during the past 30 years,and the regional climate warming was 0.30℃ (10 yr)-1 in the last three decades.

  8. Climatic Teleconnections Recorded By Tropical Mountain Glaciers

    Science.gov (United States)

    Thompson, L. G.; Permana, D.; Mosley-Thompson, E.; Davis, M. E.

    2014-12-01

    Information from ice cores from the world's highest mountains in the Tropics demonstrates both local climate variability and a high degree of teleconnectivity across the Pacific basin. Here we examine recently recovered ice core records from glaciers near Puncak Jaya in Papua, Indonesia, which lie on the highest peak between the Himalayas and the South American Andes. These glaciers are located on the western side of the Tropical Pacific warm pool, which is the "center of action" for interannual climate variability dominated by El Niño-Southern Oscillation (ENSO). ENSO either directly or indirectly affects most regions of Earth and their populations. In 2010, two ice cores measuring 32.13 m and 31.25 m were recovered to bedrock from the East Northwall Firn ice field. Both have been analyzed in high resolution (~3 cm sample length, 1156 and 1606 samples, respectively) for stable isotopes, dust, major ions and tritium concentrations. To better understand the controls on the oxygen isotopic (δ18 O) signal for this region, daily rainfall samples were collected between January 2013 and February 2014 at five weather stations over a distance of ~90 km ranging from 9 meters above sea level (masl) on the southern coast up to 3945 masl. The calculated isotopic lapse rate for this region is 0.24 ‰/100m. Papua, Indonesian ice core records are compared to ice core records from Dasuopu Glacier in the central Himalayas and from Quelccaya, Huascarán, Hualcán and Coropuna ice fields in the tropical Andes of Peru on the eastern side of the Pacific Ocean. The composite of the annual isotopic time series from these cores is significantly (R2 =0.53) related to tropical Pacific sea surface temperatures (SSTs), reflecting the strong linkage between tropical Pacific SSTs associated with ENSO and tropospheric temperatures in the low latitudes. New data on the already well-documented concomitant loss of ice on Quelccaya, Kilimanjaro in eastern Africa and the ice fields near Puncak

  9. NOAA Climate Data Records Access for Applications

    Science.gov (United States)

    Stachniewicz, J. S.; Cecil, D.; Hollingshead, A.; Newport, B. J.; Wunder, D.

    2015-12-01

    There are many potential uses of NOAA Climate Data Records (CDRs) for decision-making and catastrophic risk management assessment activities in the federal, state, and local government and private sectors, in addition to their traditional uses by the academic/scientific community. There is growing interest in using NOAA CDRs for such applications and straightforward access to the data is essential if these applications are to be successful. User engagement activities determine the types of data that users need, as well as the spatial and temporal subsets. This talk will present the access methods currently available and in development. Alternate representations and sources of some CDRs will also be discussed. Recent improvements include: 1. CDR information web page 2. Dataset types, sizes, growth, latency, grid/swath 3. Dataset discovery, data access, and sub-setting. 4. Knowing our users and their needs. 5. Known uses of some CDRs. 6. Migration to CLASS. 7. Other representations - GeoTIFF, Obs4MIPS 8. Cloud applications - Google, Microsoft

  10. Bacteria in ice may record climate change

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    @@ To many people, bacteria and climate change are like chalk and cheese: the srnallest creature versus one of the biggest phenomena on Earth. Not really.Scientists with the CAS Institute of Tibetan Plateau Research (ITP) and coworkers recently reported that small bugs deposited in ice and snow might tell how our climate has been changing.

  11. Untangling climatic and autogenic signals in peat records

    Science.gov (United States)

    Morris, Paul J.; Baird, Andrew J.; Young, Dylan M.; Swindles, Graeme T.

    2016-04-01

    Raised bogs contain potentially valuable information about Holocene climate change. However, autogenic processes may disconnect peatland hydrological behaviour from climate, and overwrite and degrade climatic signals in peat records. How can genuine climate signals be separated from autogenic changes? What level of detail of climatic information should we expect to be able to recover from peat-based reconstructions? We used an updated version of the DigiBog model to simulate peatland development and response to reconstructed Holocene rainfall and temperature reconstructions. The model represents key processes that are influential in peatland development and climate signal preservation, and includes a network of feedbacks between peat accumulation, decomposition, hydraulic structure and hydrological processes. It also incorporates the effects of temperature upon evapotranspiration, plant (litter) productivity and peat decomposition. Negative feedbacks in the model cause simulated water-table depths and peat humification records to exhibit homeostatic recovery from prescribed changes in rainfall, chiefly through changes in drainage. However, the simulated bogs show less resilience to changes in temperature, which cause lasting alterations to peatland structure and function and may therefore be more readily detectable in peat records. The network of feedbacks represented in DigiBog also provide both high- and low-pass filters for climatic information, meaning that the fidelity with which climate signals are preserved in simulated peatlands is determined by both the magnitude and the rate of climate change. Large-magnitude climatic events of an intermediate frequency (i.e., multi-decadal to centennial) are best preserved in the simulated bogs. We found that simulated humification records are further degraded by a phenomenon known as secondary decomposition. Decomposition signals are consistently offset from the climatic events that generate them, and decomposition

  12. An assessment of the solar irradiance record for climate studies

    Directory of Open Access Journals (Sweden)

    Kopp Greg

    2014-04-01

    Full Text Available Total solar irradiance, the spatially and spectrally integrated radiant output from the Sun at a mean Sun-Earth distance of 1 astronomical unit, provides nearly all the energy driving the Earth’s climate system. Variations in this energy, particularly over long time scales, contribute to changes in Earth’s climate and have been linked to historical glaciation and inter-glacial periods as well as having a small effect on more recent global warming. Accurate measurements of solar irradiances require measurements above the Earth’s atmosphere. The total solar irradiance spaceborne record began in 1978 and has been uninterrupted since, with over a dozen instruments contributing to the present solar climate data record. I assess the required and achieved accuracies of this record with a focus on its value for climate studies.

  13. Coral-based climate records from tropical South Atlantic

    DEFF Research Database (Denmark)

    Pereira, Natan S.; Sial, Alcides N.; Kikuchi, Ruy K.P.;

    2015-01-01

    Coral skeletons contain records of past environmental conditions due to their long life span and well calibrated geochemical signatures. C and O isotope records of corals are especially interesting, because they can highlight multidecadal variability of local climate conditions beyond the instrum...

  14. Climatic change and permafrost. Record from surficial deposits

    Science.gov (United States)

    Carter, L. David

    1990-01-01

    The physical and chemical characteristics of surficial deposits and the floral and faunal remains they contain provide information that is useful for interpreting both paleoclimatic and past permafrost conditions. Surficial deposits thus provide a record of climatic change and permafrost history. This record suggests that initiation of permafrost in lowland areas of the Southern Arctic Archipelago and continents of the northern hemisphere may have occurred about 2,400,000 years ago during the pronounced cooling that led to the first major glaciation of late Cenozoic time. Since then, climate has been relatively cold but cyclically variable, characterized by the growth and shrinkage of large, continental ice sheets. Permafrost has expanded and contracted in response to these climatic changes, and we can expect the present permafrost conditions to change in response to future climatic changes. To predict the response of permafrost and the landscape to future climatic change we should: (1) Define relations between climate and the modern landscape; (2) establish long-term records of past climatic change and landscape response; and (3) determine the paleoenvironments of past warm periods as possible analogs for future global warming.

  15. Developing Climate Data Records (CDRs) From NPOESS Data

    Science.gov (United States)

    Privette, J. L.; Bates, J. J.; Karl, T.; Markham, D.; Kearns, E. J.

    2008-12-01

    As part of its climate mandate, NOAA has a responsibility to provide the Nation with objective data and tools to help it characterize, understand, predict, mitigate and adapt to climate change and variability. To help fulfill that responsibility, NOAA has begun coordinating its Climate Data Record (CDR) activities with other agencies through the U.S. Climate Change Science Program (CCSP). The National Research Council (NRC, 2004) defines a CDR as "a time series of measurements of sufficient length, consistency, and continuity to determine climate variability and change." Since NPOESS represents a critical CDR data source, new efforts are underway to ensure NPOESS data can be used efficiently and economically to achieve climate goals -- particularly product reprocessing. NOAA's National Climatic Data Center (NCDC) initiated the Scientific Data Stewardship (SDS) Project to lead the Agency's CDR activities and to coordinate with the partner agencies. Given that early algorithm development is supported elsewhere, the SDS Project is focused on the generalization and application of mature algorithms to multiple satellites and sensors which together span climate-relevant time periods. It will also emphasize development and generation of Climate Information Records (CIRs), defined as time series, derived from CDRs and related long-term measurements, that provide specific information about environmental phenomena of particular importance to science and society (e.g., Tropical and Extra-Tropical Storm Intensity, Arctic Ozone Hole Area and Magnitude, Drought Severity). The SDS Project expects to execute its responsibilities in partnership with the larger scientific community through annual NOAA Announcements of Opportunity -- open to academic, commercial, non-profit and government proposers -- as well as through community reviews and working groups. This presentation will describe NOAA's climate product plans for NPOESS, initial SDS goals and objectives, and vision for the

  16. The ESA climate change initiative: Satellite data records for essential climate variables

    DEFF Research Database (Denmark)

    Hollmann, R.; Merchant, C.J.; Saunders, R.

    2013-01-01

    The European Space Agency (ESA) has launched the Climate Change Initiative (CCI) to provide satellite-based climate data records (CDRs) that meet the challenging requirements of the climate community. The aim is to realize the full potential of the long-term Earth observation (EO) archives...... that both ESA and third parties have established. This includes aspects of producing a CDR, which involve data acquisition, calibration, algorithm development, validation, maintenance, and provision of the data to the climate research community. The CCI is consistent with several international efforts...... targeting the generation of satellite derived climate data records. One focus of the CCI is to provide products for climate modelers who increasingly use satellite data to initialize, constrain, and validate models on a wide range of space and time scales....

  17. Ice Core Records of Recent Northwest Greenland Climate

    Science.gov (United States)

    Osterberg, E. C.; Wong, G. J.; Ferris, D.; Lutz, E.; Howley, J. A.; Kelly, M. A.; Axford, Y.; Hawley, R. L.

    2014-12-01

    Meteorological station data from NW Greenland indicate a 3oC temperature rise since 1990, with most of the warming occurring in fall and winter. According to remote sensing data, the NW Greenland ice sheet (GIS) and coastal ice caps are responding with ice mass loss and margin retreat, but the cryosphere's response to previous climate variability is poorly constrained in this region. We are developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate change and cryospheric response in NW Greenland to improve projections of future ice loss and sea level rise in a warming climate. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 21 m) from the coastal region of the GIS (2Barrel site; 76.9317o N, 63.1467o W, 1685 m el.) and the summit of North Ice Cap (76.938o N, 67.671o W, 1273 m el.) in 2011, 2012 and 2014. The 2Barrel ice core record has statistically significant relationships with regional spring and fall Baffin Bay sea ice extent, summertime temperature, and annual precipitation. Here we evaluate relationships between the 2014 North Ice Cap firn core glaciochemical record and climate variability from regional instrumental stations and reanalysis datasets. We compare the coastal North Ice Cap record to more inland records from 2Barrel, Camp Century and NEEM to evaluate spatial and elevational gradients in recent NW Greenland climate change.

  18. Satellite Climate Data Records: Development, Applications, and Societal Benefits

    Directory of Open Access Journals (Sweden)

    Wenze Yang

    2016-04-01

    Full Text Available This review paper discusses how to develop, produce, sustain, and serve satellite climate data records (CDRs in the context of transitioning research to operation (R2O. Requirements and critical procedures of producing various CDRs, including Fundamental CDRs (FCDRs, Thematic CDRs (TCDRs, Interim CDRs (ICDRs, and climate information records (CIRs are discussed in detail, including radiance/reflectance and the essential climate variables (ECVs of land, ocean, and atmosphere. Major international CDR initiatives, programs, and projects are summarized. Societal benefits of CDRs in various user sectors, including Agriculture, Forestry, Fisheries, Energy, Heath, Water, Transportation, and Tourism are also briefly discussed. The challenges and opportunities for CDR development, production and service are also addressed. It is essential to maintain credible CDR products by allowing free access to products and keeping the production process transparent by making source code and documentation available with the dataset.

  19. Developing NOAA's Climate Data Records From AVHRR and Other Data

    Science.gov (United States)

    Privette, J. L.; Bates, J. J.; Kearns, E. J.

    2010-12-01

    As part of the provisional NOAA Climate Service, NOAA is providing leadership in the development of authoritative, measurement-based information on climate change and variability. NOAA’s National Climatic Data Center (NCDC) recently initiated a satellite Climate Data Record Program (CDRP) to provide sustained and objective climate information derived from meteorological satellite data that NOAA has collected over the past 30+ years - particularly from its Polar Orbiting Environmental Satellites (POES) program. These are the longest sustained global measurement records in the world and represent billions of dollars of investment. NOAA is now applying advanced analysis methods -- which have improved remarkably over the last decade -- to the POES AVHRR and other instrument data. Data from other satellite programs, including NASA and international research programs and the Defense Meteorological Satellite Program (DMSP), are also being used. This process will unravel the underlying climate trend and variability information and return new value from the records. In parallel, NCDC will extend these records by applying the same methods to present-day and future satellite measurements, including the Joint Polar Satellite System (JPSS) and Jason-3. In this presentation, we will describe the AVHRR-related algorithm development activities that CDRP recently selected and funded through open competitions. We will particularly discuss some of the technical challenges related to adapting and using AVHRR algorithms with the VIIRS data that should become available with the launch of the NPOESS Preparatory Project (NPP) satellite in early 2012. We will also describe IT system development activities that will provide data processing and reprocessing, storage and management. We will also outline the maturing Program framework, including the strategies for coding and development standards, community reviews, independent program oversight, and research-to-operations algorithm

  20. Identifying climate change threats to the arctic archaeological record

    Science.gov (United States)

    Murray, Maribeth; Jensen, Anne; Friesen, Max

    2011-05-01

    Global Climate Change and the Polar Archaeological Record; Tromsø, Norway, 15-16 February 2011 ; A workshop was held at the Institute of Archaeology and Social Anthropology, University of Tromsø, in Norway, to catalyze growing concern among polar archaeologists about global climate change and attendant threats to the polar archaeological and paleoecological records. Arctic archaeological sites contain an irreplaceable record of the histories of the many societies that have lived in the region over past millennia. Associated paleoecological deposits provide powerful proxy evidence for paleoclimate and ecosystem structure and function and direct evidence of species diversity, distributions, and genetic variability. Archaeological records can span most of the Holocene (the past ∼12,000 years), depending upon location, and paleoecological records extend even further. Most are largely unstudied, and, although extremely vulnerable to destruction, they are poorly monitored and not well protected. Yet these records are key to understanding how the Arctic has functioned as a system, how humans were integrated into it, and how humans may have shaped it. Such records provide a wide range of data that are not obtainable from sources such as ice and ocean cores; these data are needed for understanding the past, assessing current and projecting future conditions, and adapting to ongoing change.

  1. Tropical Glaciers: Recorders and Indicators of Climate Change

    Science.gov (United States)

    Thompson, L. G.; Mosley-Thompson, E. S.; Buffen, A.; Urmann, D.; Davis, M. E.; Lin, P.

    2008-12-01

    Tropical climate is dominated on interannual time scales by monsoons and especially by ENSO, which is responsible for meteorological phenomena that directly or indirectly affect most regions on the planet and their populations. Common tropical teleconnections to the extra tropics include a stronger Aleutian low, stronger westerlies, variations in convective activity (flooding and drought), and modulation of tropical storm intensities. New ice core records from the Quelccaya and Coropuna ice caps provide 1700 years of continuous, annually-resolved records of climate and environmental variability expressed in the oxygen and hydrogen isotopic ratios, concentrations of mineral dust and various chemical species and net mass accumulation. These records provide an opportunity to examine the nature of tropical climate variability in greater detail, and to extract new information on ENSO and monsoon-linked climate phenomena. Quelccaya records display a prominent Little Ice Age isotopic depletion from 1520 to 1880 A.D. and a muted Medieval Warming between 1100 and 1300 AD. Drier conditions dominated from 300 to 500 AD, 1190 to 1470 AD and 1710 to 1910 with slightly wetter conditions from 500 to 1190 AD, and much wetter conditions from 1470 to 1710 A.D. and from 1910 A.D. to the present. The major cation and anion concentrations record other environmental changes over the past 1700 years. The longer tropical climate histories from Coropuna and Huascarán (Peru), Sajama (Bolivia), and Kilimanjaro (Tanzania) document abrupt climate disruptions such as the 4.2 ka drought and an extreme cold and wet period centered at 5.2 ka. The well documented ongoing ice loss on Quelccaya and Kilimanjaro paint a grim future for glacier histories from the tropics. The current melting of high-altitude, low-latitude ice fields is consistent with model predictions for a vertical amplification of temperature in the tropics. The ongoing glacier retreat in the Andes, Himalayas and Africa has

  2. Transition of SSMI Data to a Climate Data Record

    Science.gov (United States)

    Semunegus, H.; Bates, J. J.

    2007-12-01

    Since 1993, the National Oceanic and Atmospheric Administration's (NOAA) National Climatic Data Center (NCDC) has served as the active archive of passive microwave satellite measurements from the Defense Meteorological Satellite Program's (DMSP) Special Sensor Microwave Imager (SSMI) instrument. SSMI data measurements have been used extensively to generate climate data sets (including rain, snow, ice, cloud liquid water, and total precipitable water) in support of both national and international programs. A project by NCDC and NOAA's Center for Satellite Applications and Research (STAR) is working towards the goal of regenerating a high quality SSMI Climate Data Record as defined by NOAA's Scientific Data Stewardship (SDS) program. As part of this effort, the SSMI Temperature Data Record (TDR) and Sensor Data Record (SDR) datasets have been reprocessed as value-added network Common Data Form (netCDF) orbit files. Data quality control flags embedded in netCDF orbit files preserve the original data, while warning users of erroneous geolocation, radiance and temporal values at the pixel level. These orbit files will also extend the period of record of SSMI data publicly available at NOAA's Comprehensive Large-Array Stewardship System (CLASS) by several years (August 1993-February 1997). Making earlier SSMI data available to customers and improving the quality of the SSMI dataset are important steps in attaining higher levels of dataset maturity in terms of scientific value and data preservation.

  3. Biomarker records of Holocene climate variations in Asian interior

    Science.gov (United States)

    Song, M.; Liu, Z.; Liu, W.; Zhao, C.; Li, S.; He, Y.

    2012-12-01

    Understanding Holocene climate fluctuation may provide clues to projection of future climate change. Lake sediments in the arid central Asia (ACA), as an archive of past climate information, keep attracting considerable interest. We have retrieved several sediment cores from Lake Manas, an endorheic lake in Zunggar desert, Xinjiang Province, China. Biomarker proxies including alkenone Uk'37, %C37:4 and C37 concentration (C37 Conc), and physical proxies including density and magnetic susceptibility (MS) have been analyzed. We have found substantial climatic and environmental changes during the late Holocene. Density, MS and Uk'37 values are high during Medieval Warm Period (MWP) and C37 Conc is very low. During the Little Ice Age, density and MS decrease, Uk'37 values drop to near 0.1, C37 Conc is increased by 2 to 3 magnitude. Thus, warm and dry conditions dominated MWP while cold and wet conditions dominated LIA, a typical "Westerly" pattern which is opposite to the hydrological variation in Asian monsoonal regions. Biomarker records' correlation with solar irradiance (SI), the North Atlantic Oscillation (NAO), the 1000year ACA Moisture Index (ACAM), and the North Hemisphere Temperature (NHT) suggests SI as one of the forcing factor on temperature fluctuation and cold and wet LIA possibly resulting from westerly-jet shift, negative NAO oscillation and the lower evaporation induced by the decrease of temperature. Biomarker records for the whole Holocene will be also presented.

  4. Quality of Archived NDBC Data as Climate Records

    Science.gov (United States)

    2008-09-01

    The middle panel gives )(1 pfα . The bottom panel is )(1 pfr The phenomenon of climate change can be gleaned from 46042 records obtained at...spreading function at the peak of the spectrum )(1 pfr was least .8. This data culling produces heights and directions that appear reasonable and accurate...of storm activity is drifting slowly south at -.509°/yr. We suspect that the spreading function value )(1 pfr has declined .02/yr owing to underlying

  5. Progress and Processes for Generating NOAA's Climate Data Records

    Science.gov (United States)

    Johnston, S. S.; Glance, W. J.; Bates, J. J.; Kearns, E. J.

    2011-12-01

    NOAA established a satellite Climate Data Record Program (CDRP) at its National Climatic Data Center (NCDC) to provide a systematic reprocessing capability which will generate sustained and authoritative climate information from 30+ years of satellite data. CDRP implements a unique approach in archiving not only the data products themselves, but also the software, ancillary data, and enough documentation to allow any user with the processing power, to reproduce the data. Best practices, such as a common maturity matrix, software guidelines, and format standards, are employed to facilitate both the transition of research algorithms to operational software, and the long-term maintenance of the software. Throughout the implementation and execution of the program, CDRP seeks to adhere to production guidelines from Global Climate Observing System (GCOS) and World Meteorological Organization's (WMO's) Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM activity. Elements of the CDR Adaptive Processing System (CAPS) are described, along with the system's implementation approach, performance expectations, and plans for growth to accommodate increased CDR processing. In addition, a cost model has been implemented to capture the cost of CDR generation and maintenance, considering variables such as CDR complexity, source, and maturity at the beginning of the process.

  6. Break and trend analysis of EUMETSAT Climate Data Records

    Science.gov (United States)

    Doutriaux-Boucher, Marie; Zeder, Joel; Lattanzio, Alessio; Khlystova, Iryna; Graw, Kathrin

    2016-04-01

    EUMETSAT reprocessed imagery acquired by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat 8-9. The data covers the period from 2004 to 2012. Climate Data Records (CDRs) of atmospheric parameters such as Atmospheric Motion Vectors (AMV) as well as Clear and All Sky Radiances (CSR and ASR) have been generated. Such CDRs are mainly ingested by ECMWF to produce a reanalysis data. In addition, EUMETSAT produced a long CDR (1982-2004) of land surface albedo exploiting imagery acquired by the Meteosat Visible and Infrared Imager (MVIRI) on board Meteosat 2-7. Such CDR is key information in climate analysis and climate models. Extensive validation has been performed for the surface albedo record and a first validation of the winds and clear sky radiances have been done. All validation results demonstrated that the time series of all parameter appear homogeneous at first sight. Statistical science offers a variety of analyses methods that have been applied to further analyse the homogeneity of the CDRs. Many breakpoint analysis techniques depend on the comparison of two time series which incorporates the issue that both may have breakpoints. This paper will present a quantitative and statistical analysis of eventual breakpoints found in the MVIRI and SEVIRI CDRs that includes attribution of breakpoints to changes of instruments and other events in the data series compared. The value of different methods applied will be discussed with suggestions how to further develop this type of analysis for quality evaluation of CDRs.

  7. Coralline red algae as high-resolution climate recorders

    Science.gov (United States)

    Halfar, J.; Steneck, R. S.; Joachimski, M.; Kronz, A.; Wanamaker, A. D., Jr.

    2008-06-01

    Most high-resolution, proxy-based paleoclimate research hasconcentrated on tropical oceans, while mid- and high-latitudemarine regions have received less attention, despite their importancein the global climate system. At present, sclerochronologicalanalyses of bivalve mollusks supply the bulk of annual- to subannual-resolutionextratropical marine climate data, even though interpretationis complicated by a slowdown of growth with increasing shellage. Hence, in order to address the need for additional high-resolutionproxy climate data from extratropical regions, we conductedthe first year-long in situ field calibration of the corallinered alga Clathromorphum compactum in the Gulf of Maine, UnitedStates. Coralline red algae are widely distributed in coastalregions worldwide, and individual calcified plants can livecontinuously for several centuries in temperate and subarcticoceans. Stable oxygen isotopes extracted at subannual resolutionfrom growth increments of monitored specimens of C. compactumrelate well to in situ-measured sea-surface temperaturesduring the May to December calcification period, highlightingthe suitability of coralline red algae as an extratropical climatearchive. Furthermore, there is a strong correlation betweena 30 yr 18O record of C. compactum and an instrumental sea-surfacetemperature record (r = -0.58, p = 0.0008) and a proxyreconstruction derived from the bivalve Arctica islandica collectedin the central Gulf of Maine (r = 0.54, p = 0.002).

  8. Developing climate data records and essential climate variables from landsat data

    Science.gov (United States)

    Dwyer, John; Dinardo, Thomas P.; Muchoney, Douglas M.

    2011-01-01

    The series of Landsat missions has compiled the longest record of satellite observation of the Earth’s land surface, extending for more than 38 years for most areas of the globe. Landsat data are particularly important as long term climate data records because the scale of observation is sufficient to differentiate between natural and human drivers of land cover change. The USGS has established consistent radiometric calibration across the Landsat TM and ETM+ sensors, and have extended the calibration back to the earlier MSS sensors. The USGS is developing capabilities to create fundamental climate data records (FCDRs), thematic climate data records (TCDRs), and essential climate variables (ECVs) from the Landsat data archive. Two high priority TCDRs were identified: surface reflectance and land surface temperature because they have direct application or are required as input to the generation of ECVs. We will focus development on a few of the terrestrial ECVs that have a high potential for being derived from Landsat data, that include land cover, albedo, fire disturbance, surface water, snow and ice, and leaf area index (LAI). We are collaborating with scientists who have demonstrated successful algorithm development and application of these science products to develop a framework of processing capabilities to support research projects and land management applications, along with an independent strategy for product validation. Our goal is to scale the creation and validation of these products from specific sites in the conterminous U.S. and Alaska, for extension to continental and global scales.

  9. Evidence for climate change in the satellite cloud record

    Science.gov (United States)

    Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; Zelinka, Mark D.; O'Dell, Christopher W.; Klein, Stephen A.

    2016-08-01

    Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

  10. Uncertainty information in climate data records from Earth observation

    Science.gov (United States)

    Merchant, Christopher J.; Paul, Frank; Popp, Thomas; Ablain, Michael; Bontemps, Sophie; Defourny, Pierre; Hollmann, Rainer; Lavergne, Thomas; Laeng, Alexandra; de Leeuw, Gerrit; Mittaz, Jonathan; Poulsen, Caroline; Povey, Adam C.; Reuter, Max; Sathyendranath, Shubha; Sandven, Stein; Sofieva, Viktoria F.; Wagner, Wolfgang

    2017-07-01

    The question of how to derive and present uncertainty information in climate data records (CDRs) has received sustained attention within the European Space Agency Climate Change Initiative (CCI), a programme to generate CDRs addressing a range of essential climate variables (ECVs) from satellite data. Here, we review the nature, mathematics, practicalities, and communication of uncertainty information in CDRs from Earth observations. This review paper argues that CDRs derived from satellite-based Earth observation (EO) should include rigorous uncertainty information to support the application of the data in contexts such as policy, climate modelling, and numerical weather prediction reanalysis. Uncertainty, error, and quality are distinct concepts, and the case is made that CDR products should follow international metrological norms for presenting quantified uncertainty. As a baseline for good practice, total standard uncertainty should be quantified per datum in a CDR, meaning that uncertainty estimates should clearly discriminate more and less certain data. In this case, flags for data quality should not duplicate uncertainty information, but instead describe complementary information (such as the confidence in the uncertainty estimate provided or indicators of conditions violating the retrieval assumptions). The paper discusses the many sources of error in CDRs, noting that different errors may be correlated across a wide range of timescales and space scales. Error effects that contribute negligibly to the total uncertainty in a single-satellite measurement can be the dominant sources of uncertainty in a CDR on the large space scales and long timescales that are highly relevant for some climate applications. For this reason, identifying and characterizing the relevant sources of uncertainty for CDRs is particularly challenging. The characterization of uncertainty caused by a given error effect involves assessing the magnitude of the effect, the shape of the

  11. Herbivory, plant resistance, and climate in the tree ring record: interactions distort climatic reconstructions.

    Science.gov (United States)

    Trotter, R Talbot; Cobb, Neil S; Whitham, Thomas G

    2002-07-23

    To understand climate change, dendrochronologists have used tree ring analyses to reconstruct past climates, as well as ecological processes such as herbivore population dynamics. Such reconstructions, however, have been hindered by a lack of experiments that separate the influences of confounding impacts on tree rings, such as herbivores and the interactions of multiple factors. Our long-term experiments with scale insects on resistant and susceptible pines demonstrate three major points that are important to the application of this commonly used tool. (i) Herbivory reduced tree ring growth by 25-35%. (ii) The impact on ring growth distorted climate reconstruction, resulting in the overestimation of past moisture levels by more than 2-fold. Our data suggest that, if distortion because of herbivory has been a problem in previous reconstructions, estimates of the magnitude of recent climate changes are likely to be conservative. (iii) Our studies support a detectible plant resistance x herbivore x climate interaction in the tree ring record. Because resistance and susceptibility to herbivory are known to be genetically based in many systems, the potential exists to incorporate plant genetics into the field of dendrochronology, where it may be used to screen distortions from the tree ring record.

  12. Towards a satellite-based sea ice climate data record

    Science.gov (United States)

    Meier, W. N.; Fetterer, F.; Stroeve, J.; Cavalieri, D.; Parkinson, C.; Comiso, J.; Weaver, R.

    2005-12-01

    Sea ice plays an important role in the Earth's climate through its influence on the surface albedo, heat and moisture transfer between the ocean and the atmosphere, and the thermohaline circulation. Satellite data reveal that since 1979, summer Arctic sea ice has, overall, been declining at a rate of almost 8%/decade, with recent summers (beginning in 2002) being particularly low. The receding sea ice is having an effect on wildlife and indigenous peoples in the Arctic, and concern exists that these effects may become increasingly severe. Thus, a long-term, ongoing climate data record of sea ice is crucial for tracking the changes in sea ice and for assessing the significance of long-term trends. Since the advent of passive microwave satellite instruments in the early 1970s, sea ice has been one of the most consistently monitored climate parameters. There is now a 27+ year record of sea ice extent and concentration from multi-channel passive microwave radiometers that has undergone inter-sensor calibration and other quality controls to ensure consistency throughout the record. Several algorithms have been developed over the years to retrieve sea ice extent and concentration and two of the most commonly used algorithms, the NASA Team and Bootstrap, have been applied to the entire SMMR-SSM/I record to obtain a consistent time series. These algorithms were developed at NASA Goddard Space Flight Center and are archived at the National Snow and Ice Data Center. However, the complex surface properties of sea ice affect the microwave signature, and algorithms can yield ambiguous results; no single algorithm has been found to work uniformly well under all sea ice conditions. Thus there are ongoing efforts to further refine the algorithms and the time series. One approach is to develop data fusion methods to optimally combine sea ice fields from two or more algorithms. Another approach is to take advantage of the improved capabilities of JAXA's AMSR-E sensor on NASA's Aqua

  13. Climatic record of the Iberian peninsula from lake Moncortes' sediments

    Science.gov (United States)

    Cao, Min; Huguet, Carme; Rull, Valenti; Valero, Blas; Rosell-Mele, Antoni

    2014-05-01

    Climatic record of the Iberian peninsula from lake Moncortes' sediments Min Cao1, Carme Huguet1, Valenti Rull2, Blas L. Valero-Garces3, Antoni Rosell-Melé1,4 1Institut de Ciència i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Catalonia, Spain; 2Institut de Botanic de Barcelona (CSIC), Passeig del Migdia s/n, 08038, Barcelona, Spain, 3 Instituto Pirenaico de Ecologıa (CSIC), Avda. Montañana 1005, 50059 Zaragoza, Spain, 4Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Catalonia, Spain. The continuing buildup of industrial greenhouse gases in the atmosphere and concomitant increase in global temperatures has made much of the world's society aware that decades to centuries of environmental change lie ahead, and that these will have profound economic, political and societal impacts. The Iberian Peninsula lies in the boundary between tropical and subtropical climates and seems to amplify the climatic signals form the northern hemisphere through both atmospheric and water circulation feedbacks, making it an ideal site to monitor Northern hemisphere climate changes. This extreme sensitivity to climatic changes also makes the Iberian Peninsula extremely vulnerable to future climate changes. This is why understanding sensitivity to climate change and the consequences it will have on both climate and the hydrological cycle is key to implement preventive measures. The aim of our study is to come up with a high resolution quantitative reconstruction of climate variability (temperature, production and precipitation) in the Iberian Peninsula from lake sediments. We also want to establish the relation between those changes and the ones observed in both ice cores from Greenland and paleotemperature records from marine sediments of the continental Iberian margin. For these reasons we sampled a core in Moncortes (42.3N, 0.99E), a lake of karstic origin with an average depth of 25m and an area of 0

  14. Magnetic record associated with tree ring density: Possible climate proxy

    Directory of Open Access Journals (Sweden)

    Pruner Petr

    2007-03-01

    Full Text Available Abstract A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 – 1700 A.D. We measured low and high-field magnetic susceptibility, the natural remanent magnetization (NRM, saturation isothermal remanent magnetization (SIRM, and stability against thermal and alternating field (AF demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1% during the Medieval Warm Epoch (700–1300 A.D. than during the Little Ice Age (1300–1850 A.D. where it is

  15. Evaluating and Extending the Ocean Wind Climate Data Record

    Science.gov (United States)

    Ricciardulli, Lucrezia; Rodriguez, Ernesto; Stiles, Bryan W.; Bourassa, Mark A.; Long, David G.; Hoffman, Ross N.; Stoffelen, Ad; Verhoef, Anton; O'Neill, Larry W.; Farrar, J. Tomas; Vandemark, Douglas; Fore, Alexander G.; Hristova-Veleva, Svetla M.; Turk, F. Joseph; Gaston, Robert; Tyler, Douglas

    2017-01-01

    Satellite microwave sensors, both active scatterometers and passive radiometers, have been systematically measuring near-surface ocean winds for nearly 40 years, establishing an important legacy in studying and monitoring weather and climate variability. As an aid to such activities, the various wind datasets are being intercalibrated and merged into consistent climate data records (CDRs). The ocean wind CDRs (OW-CDRs) are evaluated by comparisons with ocean buoys and intercomparisons among the different satellite sensors and among the different data providers. Extending the OW-CDR into the future requires exploiting all available datasets, such as OSCAT-2 scheduled to launch in July 2016. Three planned methods of calibrating the OSCAT-2 σo measurements include 1) direct Ku-band σo intercalibration to QuikSCAT and RapidScat; 2) multisensor wind speed intercalibration; and 3) calibration to stable rainforest targets. Unfortunately, RapidScat failed in August 2016 and cannot be used to directly calibrate OSCAT-2. A particular future continuity concern is the absence of scheduled new or continuation radiometer missions capable of measuring wind speed. Specialized model assimilations provide 30-year long high temporal/spatial resolution wind vector grids that composite the satellite wind information from OW-CDRs of multiple satellites viewing the Earth at different local times. PMID:28824741

  16. Climatic and environmental records in Guliya Ice Cap

    Institute of Scientific and Technical Information of China (English)

    姚檀栋; 焦克勤; 田力德; 李忠勤; 李月芳; 刘景寿; 皇翠兰; 谢超; L.G.Thompson; E.M.Thompson

    1995-01-01

    The Guliya Ice Cap is the largest (with a total area of 376.1 m2 and an area cf 131 2 m2 at the flat top), highest (6 700 m a. s.l.) and coldest (with an ice temperature of -19℃ at 10 m depth) ice cap found in Central Asia so far. From 1990 to 1992, the oxygen isotope ratios, microparticle concentrations, anions, cations of a large number of samples from snow pits and ice cores were analysed to study the climatic and environmental characteristics of the Guliya Ice Cap. Being frozen to bedrock and with extremely low ice temperature, the ideal climatic and environmental informarion was recorded in Guliya Ice Cap. The distinct annual and seasonal cycle characteristics of the oxygen isotope ratio, microparticle concentration, anion and cation provide bases to date precisely the high-resolution time series in the ice cap. Oxygen isotope ratios decreased, microparticle concentrations and various chemical elements increased in the colder periods, while oxygen isotope values increased, microparticle concentrat

  17. NOAA Climate Data Record Normalized Difference Vegetation Index: 1981-2013

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — National Oceanic and Atmospheric Administration (NOAA) Climate Data Records (CDR) provide historical climate information using data from weather satellites. This...

  18. NOAA Climate Data Record Normalized Difference Vegetation Index: 1981-2013

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — National Oceanic and Atmospheric Administration (NOAA) Climate Data Records (CDR) provide historical climate information using data from weather satellites. This...

  19. The EUMETSAT sea ice concentration climate data record

    Science.gov (United States)

    Tonboe, Rasmus T.; Eastwood, Steinar; Lavergne, Thomas; Sørensen, Atle M.; Rathmann, Nicholas; Dybkjær, Gorm; Toudal Pedersen, Leif; Høyer, Jacob L.; Kern, Stefan

    2016-09-01

    An Arctic and Antarctic sea ice area and extent dataset has been generated by EUMETSAT's Ocean and Sea Ice Satellite Application Facility (OSISAF) using the record of microwave radiometer data from NASA's Nimbus 7 Scanning Multichannel Microwave radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager and Sounder (SSMIS) satellite sensors. The dataset covers the period from October 1978 to April 2015 and updates and further developments are planned for the next phase of the project. The methodology for computing the sea ice concentration uses (1) numerical weather prediction (NWP) data input to a radiative transfer model for reduction of the impact of weather conditions on the measured brightness temperatures; (2) dynamical algorithm tie points to mitigate trends in residual atmospheric, sea ice, and water emission characteristics and inter-sensor differences/biases; and (3) a hybrid sea ice concentration algorithm using the Bristol algorithm over ice and the Bootstrap algorithm in frequency mode over open water. A new sea ice concentration uncertainty algorithm has been developed to estimate the spatial and temporal variability in sea ice concentration retrieval accuracy. A comparison to US National Ice Center sea ice charts from the Arctic and the Antarctic shows that ice concentrations are higher in the ice charts than estimated from the radiometer data at intermediate sea ice concentrations between open water and 100 % ice. The sea ice concentration climate data record is available for download at www.osi-saf.org, including documentation.

  20. Growing up MODIS: Towards a mature aerosol climate data record

    Science.gov (United States)

    Levy, Robert C.

    2013-05-01

    Aerosols are major players within the Earth's climate system, affecting the radiation budget, clouds and the hydrological cycle. In high concentrations near the surface, aerosols (or particulate matter, PM) affect visibility, impact air quality, and can contribute to poor health. Among others, Yoram Kaufman recognized the importance of aerosols to climate, and helped to design new instrumentation and algorithms to retrieve and quantify global aerosol properties. One instrument, known as the Moderate Imaging Resolution Spectro-radiometer (MODIS), was deployed on the AM-1 satellite (later known as Terra), part of NASA's Earth Observing System (EOS). In 1998, armed with an M.S. and job experience in neither aerosols nor satellites, I was looking for a new job. I somehow found my way to the MODIS Aerosol team. It was only a year before Terra launch, and most major decisions about the MODIS aerosol retrieval algorithms had been finalized. Since then, we worked through launch, initial evaluation of the product with AERONET and field deployments, and continued efforts to understand the product and refine retrieval algorithms. I have had opportunities to participate in field experiments, write papers, and earn my PhD. The "second generation" algorithm for aerosol retrieval over land has been hugely successful. We have collected nearly a half-million collocations with AERONET and other dataseis, made new discoveries, and have contributed to research and operational projects globally. Due to the dedication of the entire team, the MODIS aerosol product now is one of the highlights of NASA's EOS program. It is used for climate research and air quality forecasting, as well for applications not even considered before the MODIS era. More recently, a focus is on stitching the MODIS aerosol product into the "climate data record" (CDR) for global aerosol, determining whether the product has sufficient length, consistency and continuity to determine climate variability and change

  1. VIIRS Climate Raw Data Record (C-RDR) from Suomi NPP, Version 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Suomi NPP Climate Raw Data Record (C-RDR) developed at the NOAA NCDC is an intermediate product processing level (NOAA Level 1b) between a Raw Data Record (RDR)...

  2. NOAA Climate Data Record (CDR) of Northern Hemisphere (NH) Snow Cover Extent (SCE), Version 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) is a record for the Northern Hemisphere (NH) Snow Cover Extent (SCE) spanning from October 4, 1966 to present, updated monthly...

  3. High-resolution record of Northern Hemisphere climate extending into the last interglacial period

    DEFF Research Database (Denmark)

    North Greenland Ice Core Project members; Andersen, Katrine K.; Azuma, N.

    2004-01-01

    Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from...... the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw...

  4. Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 years

    Science.gov (United States)

    Mills, K.; Ryves, D. B.; Anderson, N. J.; Bryant, C. L.; Tyler, J. J.

    2014-08-01

    Equatorial East Africa has a complex regional patchwork of climate regimes, sensitive to climate fluctuations over a variety of temporal and spatial scales during the late Holocene. Understanding how these changes are recorded in and interpreted from biological and geochemical proxies in lake sedimentary records remains a key challenge to answering fundamental questions regarding the nature, spatial extent and synchroneity of climatic changes seen in East African palaeo-records. Using a paired lake approach, where neighbouring lakes share the same geology, climate and landscape, it might be expected that the systems will respond similarly to external climate forcing. Sediment cores from two crater lakes in western Uganda spanning the last ~1000 years were examined to assess diatom community responses to late Holocene climate and environmental changes, and to test responses to multiple drivers using redundancy analysis (RDA). These archives provide annual to sub-decadal records of environmental change. Lakes Nyamogusingiri and Kyasanduka appear to operate as independent systems in their recording of a similar hydrological response signal via distinct diatom records. However, whilst their fossil diatom records demonstrate an individualistic, indirect response to external (e.g. climatic) drivers, the inferred lake levels show similar overall trends and reflect the broader patterns observed in Uganda and across East Africa. The lakes appear to be sensitive to large-scale climatic perturbations, with evidence of a dry Medieval Climate Anomaly (MCA; ca. AD 1000-1200). The diatom record from Lake Nyamogusingiri suggests a drying climate during the main phase of the Little Ice Age (LIA) (ca. AD 1600-1800), whereas the diatom response from the shallower Lake Kyasanduka is more complex (with groundwater likely playing a key role), and may be driven more by changes in silica and other nutrients, rather than by lake level. The sensitivity of these two Ugandan lakes to regional

  5. Coral-based climate records from tropical South Atlantic

    DEFF Research Database (Denmark)

    Pereira, Natan S.; Sial, Alcides N.; Kikuchi, Ruy K.P.

    2015-01-01

    astreoides from the Rocas Atoll (offshore Brazil), a new location for climate reconstruction. We present time series of isotopic variation from profiles along the corallite valley of one colony and the apex of the corallite fan of the other colony. Significant differences in the isotopic values between...... with a bloom of endolithic algae, may indicate physiological alteration of this colony. Our findings indicate that corals from the Rocas Atoll can be used for monitoring climate oscillations in the tropical South Atlantic Ocean....

  6. Challenges in assessing the contribution of climate change to observed record-breaking heat waves

    Science.gov (United States)

    Perlwitz, J.; Xu, T.; Quan, X.; Hoerling, M. P.; Dole, R. M.

    2013-12-01

    Record-setting heat waves have large impacts on public health and society due to increased mortality rate, wild fires, property damages and agricultural loss. There is increasing interest in understanding the causes of such extreme events including the role of climate change. We use the example of the link between atmospheric blocking frequency and summertime seasonal temperature extreme to address some challenges in determining the relative contributions of natural variability and climate change on the occurrence and magnitude of extreme climate-related events. We utilize the 62-year record of observational data from 1960 to 2011 and long integrations with the NCARs Community Climate System Model Version 4 (CCSM4). This climate model represents well atmospheric blocking frequency and related weather features over the European/Ural region. Both observations and long climate integrations suggest that seasonal temperature extremes over the Northern European/Ural region are strongly conditioned by blocking. We illustrate that one challenge in climate event attribution is related to the fact that very long records are necessary to sufficiently sample the frequency of occurrence of the principal driver of a record-setting climate event. We further illustrate that there is a strong regional dependence on how the link between blocking frequency and extreme temperature anomalies is modified due to climate change suggesting that event attribution results are often not transferable from one region to another.

  7. Glacial-interglacial climate changes recorded by debris flow fan deposits, Owens Valley, California

    Science.gov (United States)

    D'Arcy, Mitch; Roda-Boluda, Duna C.; Whittaker, Alexander C.

    2017-08-01

    It is hotly debated whether and how climate changes are recorded by terrestrial stratigraphy. Basin sediments produced by catchment-alluvial fan systems may record past climate over a variety of timescales, and could offer unique information about how climate controls sedimentation. Unfortunately, there are fundamental uncertainties about how climatic variables such as rainfall and temperature translate into sedimentological signals. Here, we examine 35 debris flow fan surfaces in Owens Valley, California, that record deposition throughout the past 125,000 years, during which climate has varied significantly. We show that the last full glacial-interglacial cycle is recorded with high fidelity by the grain size distributions of the debris flow deposits. These flows transported finer sediment during the cooler glacial climate, and became systematically coarser-grained as the climate warmed and dried. We explore the physical mechanisms that might explain this signal, and rule out changes in sediment supply through time. Instead, we propose that grain size records past changes in storm intensity, which is responsible for debris flow initiation in this area and is decoupled from average rainfall rates. This is supported by an exponential Clausius-Clapeyron-style scaling between grain size and temperature, and also reconciles with climate dynamics and the initiation of debris flows. The fact that these alluvial fans exhibit a strong, sustained sensitivity to orbital climate changes sheds new light on how eroding landscapes and their sedimentary products respond to climatic forcing. Finally, our findings highlight the importance of threshold-controlled events, such as storms and debris flows, in driving erosion and sedimentation at the Earth's surface in response to climate change.

  8. NOAA Climate Data Record (CDR) of AVHRR Polar Pathfinder (APP) Cryosphere

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) contains the AVHRR Polar Pathfinder (APP) product. APP is a fundamental CDR comprised of calibrated and navigated AVHRR channel...

  9. NOAA Climate Data Record (CDR) of Ocean Heat Fluxes, Version 1.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Ocean Surface Bundle (OSB) Climate Data Record (CDR) consist of three parts: sea surface temperature, near-surface atmospheric properties, and heat fluxes....

  10. NOAA Climate Data Record (CDR) of Upper Atmospheric Temperature 4 Layer Microwave, Version 3.3

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 4 Layer Upper Atmosphere Temperature (UAT) Climate Data Record (CDR) dataset is a monthly analysis of the tropospheric and stratospheric data using temperature...

  11. NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set provides a Climate Data Record (CDR) of sea ice concentration from passive microwave data. It provides a consistent, daily and monthly time series of...

  12. Unified Sea Ice Thickness Climate Data Record Collection Spanning 1947-2012

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Unified Sea Ice Thickness Climate Data Record is the result of a concerted effort to collect as many observations as possible of Arctic sea-ice draft, freeboard,...

  13. NOAA Climate Data Record (CDR) of Ocean Near Surface Atmospheric Properties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Ocean Surface Bundle (OSB) Climate Data Record (CDR) consist of three parts: sea surface temperature, near-surface atmospheric properties, and heat fluxes....

  14. NOAA Climate Data Record (CDR) of Monthly Outgoing Longwave Radiation (OLR), Version 2.2-1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This Climate Data Record (CDR) of monthly mean High Resolution Infrared Radiation Sounder (HIRS) Outgoing Longwave Radiation (OLR) flux at the top of the atmosphere...

  15. NOAA Climate Data Record (CDR) of Normalized Difference Vegetation Index (NDVI), Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains gridded daily Normalized Difference Vegetation Index (NDVI) derived from the NOAA Climate Data Record (CDR) of Advanced Very High Resolution...

  16. NOAA Climate Data Record (CDR) of AVHRR Polar Pathfinder Extended (APP-X) Cryosphere

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA Climate Data Record (CDR) of the extended AVHRR Polar Pathfinder (APP-x) cryosphere contains 19 geophysical variables over the Arctic and Antarctic for the...

  17. NOAA Climate Data Record (CDR) of Sea Surface Temperature -WHOI, Version 1.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Ocean Surface Bundle (OSB) Climate Data Record (CDR) consist of three parts: sea surface temperature, near-surface atmospheric properties, and heat fluxes....

  18. NOAA Climate Data Record (CDR) of Daily Outgoing Longwave Radiation (OLR), Version 1.2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This Climate Data Record (CDR) contains the daily mean Outgoing Longwave Radiation (OLR) time series in global 1 degree x 1 degree equal-angle gridded maps spanning...

  19. NOAA Climate Data Record (CDR) of Total Solar Irradiance (TSI), NRLTSI Version 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This Climate Data Record (CDR) contains total solar irradiance (TSI) as a function of time created with the Naval Research Laboratory model for spectral and total...

  20. NOAA Climate Data Record (CDR) of Solar Spectral Irradiance (SSI), NRLSSI Version 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This Climate Data Record (CDR) contains solar spectral irradiance (SSI) as a function of time and wavelength created with the Naval Research Laboratory model for...

  1. NOAA Climate Data Record (CDR) of Passive Microwave Sea Ice Concentration, Version 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Passive Microwave Sea Ice Concentration Climate Data Record (CDR) dataset is generated using daily gridded brightness temperatures from the Defense...

  2. Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 yr

    Directory of Open Access Journals (Sweden)

    K. Mills

    2013-09-01

    Full Text Available Equatorial East Africa has a complex, regional patchwork of climate regimes, with multiple interacting drivers. Recent studies have focussed on large lakes and reveal signals that are smoothed in both space and time, and, whilst useful at a continental scale, are of less relevance when understanding short-term, abrupt or immediate impacts of climate and environmental changes. Smaller-scale studies have highlighted spatial complexity and regional heterogeneity of tropical palaeoenvironments in terms of responses to climatic forcing (e.g. the Little Ice Age [LIA] and questions remain over the spatial extent and synchroneity of climatic changes seen in East African records. Sediment cores from paired crater lakes in western Uganda were examined to assess ecosystem response to long-term climate and environmental change as well as testing responses to multiple drivers using redundancy analysis. These archives provide annual to sub-decadal records of environmental change. The records from the two lakes demonstrate an individualistic response to external (e.g. climatic drivers, however, some of the broader patterns observed across East Africa suggest that the lakes are indeed sensitive to climatic perturbations such as a dry Mediaeval Climate Anomaly (MCA; 1000–1200 AD and a relatively drier climate during the main phase of the LIA (1500–1800 AD; though lake levels in western Uganda do fluctuate. The relationship of Ugandan lakes to regional climate drivers breaks down c. 1800 AD, when major changes in the ecosystems appear to be a response to sediment and nutrient influxes as a result of increasing cultural impacts within the lake catchments. The data highlight the complexity of individual lake response to climate forcing, indicating shifting drivers through time. This research also highlights the importance of using multi-lake studies within a landscape to allow for rigorous testing of climate reconstructions, forcing and ecosystem response.

  3. Climatic variations in the past 140 ka recorded in core RM, east Qinghai-Xizang Plateau

    Institute of Scientific and Technical Information of China (English)

    吴敬禄; 王苏民; 潘红玺; 夏威岚

    1997-01-01

    The sequences of climatic evolution are reconstructed by the analyses of δ13C and δ18O of carbonate from core RM in the Zoige Basin since 140 kaB. P. During the Last Glaciation there existed at least seven warm climatic fluctuations and five cold events correlated with the records of ice core and deep sea, and during the preceding last in-terglacial period there were two cold climatic variations coinciding with the record of ice core GRIP. These results depict climatic instability in east Qinghai-Xizang Plateau over the last interglacial period. In addition, the environmental proxies of the carbonate content and pigments indicate the similar results to the stable isotope record from core RM.

  4. Abundant climatic information in water stable isotope record from a maritime glacier on southeastern Tibetan Plateau

    Science.gov (United States)

    Zhao, Huabiao; Xu, Baiqing; Li, Zhen; Wang, Mo; Li, Jiule; Zhang, Xiaolong

    2016-04-01

    Climatic significance of ice core stable isotope record in the Himalayas and southern Tibetan Plateau (TP), where the climate is alternately influenced by Indian summer monsoon and mid-latitude westerlies, is still debated. A newly drilled Zuoqiupu ice core from a temperate maritime glacier on the southeastern TP covering 1942-2011 is investigated in terms of the relationships between δ18O and climate parameters. Distinct seasonal variation of δ18O is observed due to high precipitation amount in this area. Thus the monsoon (June to September) and non-monsoon (October to May) δ18O records are reconstructed, respectively. The temperature effect is identified in the annual δ18O record, which is predominantly contributed by temperature control on the non-monsoon precipitation δ18O record. Conversely, the negative correlation between annual δ18O record and precipitation amount over part of Northeast India is mostly contributed by the monsoon precipitation δ18O record. The variation of monsoon δ18O record is greatly impacted by the Indian summer monsoon strength, while that of non-monsoon δ18O record is potentially associated with the mid-latitude westerly activity. The relationship between Zuoqiupu δ18O record and Sea Surface Temperature (SST) is found to be inconsistent before and after the climate shift of 1976/1977. In summer monsoon season, the role of SST in the monsoon δ18O record is more important in eastern equatorial Pacific Ocean and tropical Indian Ocean before and after the shift, respectively. In non-monsoon season, however, the Atlantic Multidecadal Oscillation has a negative impact before but positive impact after the climate shift on the non-monsoon δ18O record.

  5. Forest fire and climate change in western North America: insights from sediment charcoal records.

    Science.gov (United States)

    Daniel G Gavin; Douglas J Hallett; Feng Sheng Hu; Kenneth P Lertzman; Susan J Prichard; Kendrick J Brown; Jason A Lynch; Patrick Bartlein; David L. Peterson

    2007-01-01

    Millennial-scale records of forest fire provide important baseline information for ecosystem management, especially in regions with too few recent fires to describe the historical range of variability. Charcoal records from lake sediments and soil profiles are well suited for reconstructing the incidence of past fire and its relationship to changing climate and...

  6. The GOME-type Total Ozone Essential Climate Variable (GTO-ECV data record from the ESA Climate Change Initiative

    Directory of Open Access Journals (Sweden)

    M. Coldewey-Egbers

    2015-05-01

    Full Text Available We present the new GOME-type Total Ozone Essential Climate Variable (GTO-ECV data record which has been created within the framework of the European Space Agency's Climate Change Initiative (ESA-CCI. Total ozone column observations – based on the GOME-type Direct Fitting version 3 algorithm – from GOME (Global Ozone Monitoring Experiment, SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY, and GOME-2 have been combined into one homogeneous time series, thereby taking advantage of the high inter-sensor consistency. The data record spans the 15-year period from March 1996 to June 2011 and it contains global monthly mean total ozone columns on a 1° × 1° grid. Geophysical ground-based validation using Brewer, Dobson, and UV-visible instruments has shown that the GTO-ECV level 3 data record is of the same high quality as the equivalent individual level 2 data products that constitute it. Both absolute agreement and long-term stability are excellent with respect to the ground-based data, for almost all latitudes apart from a few outliers which are mostly due to sampling differences between the level 2 and level 3 data. We conclude that the GTO-ECV data record is valuable for a variety of climate applications such as the long-term monitoring of the past evolution of the ozone layer, trend analysis and the evaluation of Chemistry–Climate Model simulations.

  7. Extracting a climate signal from 169 glacier records

    NARCIS (Netherlands)

    Oerlemans, J.

    2005-01-01

    I constructed a temperature history for different parts of the world from 169 glacier length records. Using a first-order theory of glacier dynamics, I related changes in glacier length to changes in temperature. The derived temperature histories are fully independent of proxy and instrumental data

  8. Multiproxy records of climate variability for Kamchatka for the past 400 years

    Directory of Open Access Journals (Sweden)

    O. Solomina

    2006-11-01

    Full Text Available Tree rings, ice cores and glacial geologic histories for the past several centuries offer an opportunity to characterize climate variability and to identify the key climate parameters forcing glacier expansions. A newly developed larch ring-width chronology is presented for Kamchatka that is sensitive to past summer temperature variability. This record provides the basis to compare with other proxy records of inferred temperature and precipitation change from ice core and glacier records, and to characterize climate for the region over the past 400 years. Individual low growth years in the larch record are associated with several known and proposed volcanic events that have been observed in other proxy records from the Northern Hemisphere. Comparison of the tree-rings with an ice core record of melt feature index for Kamchatka's Ushkovsky volcano confirms a 1–3 year dating accuracy for this ice core series over the late 18th to 20th centuries. Decadal variations of low summer temperatures (tree-ring record and high annual precipitation (ice core record are broadly consistent with intervals of positive mass balance measured and estimated at several glaciers, and with moraine building, provides a basis to interpret geologic glacier records.

  9. Climate forcing and Neanderthal extinction in Southern Iberia: insights from a multiproxy marine record

    Science.gov (United States)

    Jiménez-Espejo, Francisco J.; Martínez-Ruiz, Francisca; Finlayson, Clive; Paytan, Adina; Sakamoto, Tatsuhiko; Ortega-Huertas, Miguel; Finlayson, Geraldine; Iijima, Koichi; Gallego-Torres, David; Fa, Darren

    2007-04-01

    Paleoclimate records from the western Mediterranean have been used to further understand the role of climatic changes in the replacement of archaic human populations inhabiting South Iberia. Marine sediments from the Balearic basin (ODP Site 975) was analysed at high resolution to obtain both geochemical and mineralogical data. These data were compared with climate records from nearby areas. Baexcces was used to characterize marine productivity and then related to climatic variability. Since variations in productivity were the consequence of climatic oscillations, climate/productivity events have been established. Sedimentary regime, primary marine productivity and oxygen conditions at the time of population replacement were reconstructed by means of a multiproxy approach. Climatic/oceanographic variations correlate well with Homo spatial and occupational patterns in Southern Iberia. It was found that low ventilation (U/Th), high river supply (Mg/Al), low aridity (Zr/Al) and low values of Baexcess coefficient of variation, may be linked with Neanderthal hospitable conditions. We attempt to support recent findings which claim that Neanderthals populations continued to inhabit southern Iberia between 30 and ˜28 ky cal BP and that this persistence was due to the specific characteristics of South Iberian climatic refugia. Comparisons of our data with other marine and continental records appear to indicate that conditions in South Iberia were highly inhospitable at ˜24 ky cal BP. Thus, it is proposed that the final disappearance of Neanderthals in this region could be linked with these extreme conditions.

  10. Reconstructing terrestrial climate in the Pliocene Arctic: reading the record from ancient trees. (Invited)

    Science.gov (United States)

    Csank, A. Z.

    2013-12-01

    With an increasing number of studies highlighting Pliocene climate as an analogue for future warmth, the need for accurate proxy records for this period is crucial. In order to better investigate Pliocene climate as an analogue for future warmth a better understanding of the natural inter-annual variability during the Pliocene is needed. Dispersed throughout the Arctic are incredibly well-preserved fossil forest sites. Tree ring studies have vastly improved our knowledge of past climate variability and isotopic records developed from tree rings can enhance traditional ring width proxy records. Presented here are the results of work to develop annually resolved records of Pliocene climate from several Arctic fossil forest sites ranging in age from 3.8 to 2.8 million years old. Findings indicate that growing season temperatures were 10-14° C warmer than at present with an interannual range of variability of ~5° C and mean annual temperatures (MAT) 17-19° C warmer than present with interannual variability of ~2° C. The greater difference from modern in MAT could indicate that Pliocene winter temperatures were considerably warmer than summer temperatures. Late Pliocene temperatures are not significantly cooler than early Pliocene temperatures suggesting that that forest deposits in the Arctic capture a snapshot of interglacial conditions during the Pliocene. The >200 year long records produced from these fossil forest sites indicates that there is evidence for decadal scale climate variability in Pliocene climate suggesting that perhaps modes of climate variability like the Northern Annular Mode may have been present during the Pliocene. Studies of decadal variability in a past warmer world may be useful to inform how these modes of variability may behave in the future or to inform us on how these modes of variability may have been similar or different during the Pliocene. Ongoing work will provide information on seasonal climate during the Pliocene.

  11. Millennial- to century-scale variability in Gulf of Mexico Holocene climate records

    Science.gov (United States)

    Poore, R.Z.; Dowsett, H.J.; Verardo, S.; Quinn, T.M.

    2003-01-01

    Proxy records from two piston cores in the Gulf of Mexico (GOM) provide a detailed (50-100 year resolution) record of climate variability over the last 14,000 years. Long-term (millennial-scale) trends and changes are related to the transition from glacial to interglacial conditions and movement of the average position of the Intertropical Convergence Zone (ITCZ) related to orbital forcing. The ??18O of the surface-dwelling planktic foraminifer Globigerinoides ruber show negative excursions between 14 and 10.2 ka (radiocarbon years) that reflect influx of meltwater into the western GOM during melting of the Laurentide Ice Sheet. The relative abundance of the planktic foraminifer Globigerinoides sacculifer is related to transport of Caribbean water into the GOM. Maximum transport of Caribbean surface waters and moisture into the GOM associated with a northward migration of the average position of the ITCZ occurs between about 6.5 and 4.5 ka. In addition, abundance variations of G. sacculifer show century-scale variability throughout most of the Holocene. The GOM record is consistent with records from other areas, suggesting that century-scale variability is a pervasive feature of Holocene climate. The frequency of several cycles in the climate records is similar to cycles identified in proxy records of solar variability, indicating that at least some of the century-scale climate variability during the Holocene is due to external (solar) forcing.

  12. Lake ice records used to detect historical and future climatic changes

    Science.gov (United States)

    Robertson, Dale M.; Ragotzkie, R.A.; Magnuson, John J.

    1992-01-01

    Historical ice records, such as freeze and breakup dates and the total duration of ice cover, can be used as a quantitative indicator of climatic change if long homogeneous records exist and if the records can be calibrated in terms of climatic changes. Lake Mendota, Wisconsin, has the longest uninterrupted ice records available for any lake in North America dating back to 1855. These records extend back prior to any reliable air temperature data in the midwestern region of the U.S. and demonstrate significant warming of approximately 1.5 °C in fall and early winter temperatures and 2.5 °C in winter and spring temperatures during the past 135 years. These changes are not completely monotonie, but rather appear as two shorter periods of climatic change in the longer record. The first change was between 1875 and 1890, when fall, winter, and spring air temperatures increased by approximately 1.5 °C. The second change, earlier ice breakup dates since 1979, was caused by a significant increase in winter and early spring air temperatures of approximately 1.3 °C. This change may be indicative of shifts in regional climatic patterns associated with global warming, possibly associated with the ‘Greenhouse Effect’.

  13. Simulated European stalagmite record and its relation to a quasi-decadal climate mode

    Directory of Open Access Journals (Sweden)

    G. Lohmann

    2013-01-01

    Full Text Available A synthetic stalagmite δ18O record for the Bunker Cave (51° N, 7° E is constructed using a combined climate–stalagmite modelling approach where we combine an atmospheric circulation model equipped with water isotopes and a model simulating stalagmite calcite δ18O values. Mixing processes in the soil and karst above the cave represent a natural low-pass filter of the speleothem climate archive. Stalagmite δ18O values at Bunker Cave lag the regional surface climate by 3–4 yr. The power spectrum of the simulated speleothem calcite δ18O record has a pronounced peak at quasi-decadal time scale, which is associated with a large-scale climate variability pattern in the North Atlantic. Our modelling study suggests that stalagmite records from Bunker Cave are representative for large-scale teleconnections and can be used to obtain information about the North Atlantic and its decadal variability.

  14. Solar cycles or random processes? Evaluating solar variability in Holocene climate records.

    Science.gov (United States)

    Turner, T Edward; Swindles, Graeme T; Charman, Dan J; Langdon, Peter G; Morris, Paul J; Booth, Robert K; Parry, Lauren E; Nichols, Jonathan E

    2016-04-05

    Many studies have reported evidence for solar-forcing of Holocene climate change across a range of archives. These studies have compared proxy-climate data with records of solar variability (e.g. (14)C or (10)Be), or have used time series analysis to test for the presence of solar-type cycles. This has led to some climate sceptics misrepresenting this literature to argue strongly that solar variability drove the rapid global temperature increase of the twentieth century. As proxy records underpin our understanding of the long-term processes governing climate, they need to be evaluated thoroughly. The peatland archive has become a prominent line of evidence for solar forcing of climate. Here we examine high-resolution peatland proxy climate data to determine whether solar signals are present. We find a wide range of significant periodicities similar to those in records of solar variability: periods between 40-100 years, and 120-140 years are particularly common. However, periodicities similar to those in the data are commonly found in random-walk simulations. Our results demonstrate that solar-type signals can be the product of random variations alone, and that a more critical approach is required for their robust interpretation.

  15. Early Holocene climate oscillations recorded in three Greenland ice cores

    DEFF Research Database (Denmark)

    Rasmussen, Sune Olander; Vinther, Bo Møllesøe; Clausen, Henrik Brink;

    2007-01-01

    A new ice core chronology for the Greenland DYE-3, GRIP, and NGRIP ice cores has been constructed, making it possible to compare the d18O and accumulation signals recorded in the three cores on an almost annual scale throughout the Holocene. We here introduce the new time scale and investigate d18O...... and accumulation anomalies that are common to the three cores in the Early Holocene (7.9–11.7 ka before present). Three time periods with significant and synchronous anomalies in the d18O and accumulation signals stand out: the well-known 8.2 ka event, an event of shorter duration but of almost similar amplitude...... around 9.3 ka before present, and the Preboreal Oscillation during the first centuries of the Holocene. For each of these sections, we present a d18O anomaly curve and a common accumulation signal that represents regional changes in the accumulation rate over the Greenland ice cap....

  16. Comparing records to understand past rapid climate change: An INTIMATE database update

    Science.gov (United States)

    Kearney, Rebecca; Bronk Ramsey, Christopher; Staff, Richard A.; Albert, Paul G.

    2017-04-01

    Integrating multi-proxy records from ice, terrestrial and marine records enhances the understanding of the temporal and spatial variation of past rapid climatic changes globally. By handling these records on their own individual timescales and linking them through known chronological relationships (e.g. tephra, 10Be and 14C), regional comparisons can be made for these past climatic events. Furthermore, the use of time-transfer functions enables the chronological uncertainties between different archives to be quantified. The chronological database devised by the working group 1 (WG1) of INTIMATE, exclusively uses this methodology to provide a means to visualise and compare palaeoclimate records. Development of this database is ongoing, with numerous additional records being added to the database with a particular focus on European archives spanning the Late Glacial period. Here we present a new phase of data collection. Through selected cases study sites across Europe, we aim to illustrate the database as a novel tool in understanding spatial and temporal variations in rapid climatic change. Preliminary results allow questions such as time transgression and regional expressions of rapid climate change to be investigated. The development of this database will continue through additional input of raw climate proxy data, linking to other relevant databases (e.g. Fossil Pollen Database) and providing output data that can be analysed in the statistical programming language of R. A major goal of this work to is not only provide a detailed database, but allow researchers to integrate their own climate proxy data with that on the database.

  17. Validation of alternative marine calcareous skeletons as recorders of global climate changes (CALMARS): final report

    OpenAIRE

    Willenz, P.; Berry, L.; Dehairs, F.A.; Baeyens, W.F.J.; Gillikin, D. P.; E. Keppens; Ridder, F.; André, L.; Verheyden, S.; A. Lorrain; Dubois, Ph.; Ranner, H.; Blust, R.; Mubiana, V.K.

    2006-01-01

    Understanding environmental proxies stored in biogenic carbonates has become a major task and a multidisciplinary endeavour. The CALMARs project (CALcareous MARine Skeletons as recorders of global climate changes) involved reading these records stored in biogenic carbonates and aimed at validating the skeletons of sclerosponges, bivalves and echinoderms as environmental proxies. The first aim was to determine the growth rates of two hyper calcified sponges: Ceratoporella nicholsoni and Petrob...

  18. Records from Lake Qinghai: Holocene climate history of Northeastern Tibetan Plateau linking to global change

    Science.gov (United States)

    An, Z.; Colman, S.; Zhou, W.; Brown, E.; Li, X.; Jull, T.; Wang, S.; Liu, W.; Sun, Y.; Lu, X.; Song, Y.; Chang, H.; Cai, Y.; Xu, H.; Wang, X.; Liu, X.; Wu, F.; Han, Y.; Cheng, P.; Ai, L.; Wang, Z.; Qiang, X.; Shen, J.; Zhu, Y.; Wu, Z.; Liu, X.

    2008-12-01

    Lake Qinghai (99°36'-100°16'E, 36°32'-37°15'N ) of the north eastern margin of Tibet Plateau is the largest inland lake of China. It sits on the transitional zone of Asian monsoon- arid areas, receives influences of Asian monsoons and Westerlies, thus sensitive to global climate changes. Although previous studies had investigated Holocene climate change of Lake Qinghai area, it is rare to see precise Holocene climatic sequences of Lake Qinghai, nor in-depth discussions on controlling factors of Lake Qinghai climate changes. In Year 2005, with support from ICDP, Chinese Academy of Sciences (CAS), Chinese Ministry of Science and Technology (MOST) and National Science Foundation of China (NSFC), Drilling, Observation and Sampling of the Earths Continental Crust Corporation (DOSECC) and Institute of Earth Environment, Chinese Academy of Sciences (IEECAS) took a series of shallows cores from the southern basin of Lake Qinghai. West sub-basin sediments display Holocene lacustrine feature for the upper 5m, while the 5-18m are interbeded sediments of shallow lake, eolian-lacustrine and eolian loess. Chinese and US scientists with support from NSFC, MOST, CAS and NSF analysed 1F core from west sub-basin depocenter of the south basin with multiple physical, chemical, biological approaches. By comparing with modern process observation records, we obtained proxies that respectfully reflect precipitation, temperature and lake salinity changes, etc., reconstructed high resolution time sequences of magnetic susceptibility, colour scale, grain size, Corg, C/N, δ13Corg, carbonate, δ13C and δ18O of carbonate and ostracodes, elements, char-soot,Uk'37 and %C37:4 as well as pollen of the last 13Ka. They indicate the climatic change history of Lake Qinghai since past 13Ka, and agreeable evidences are found from adjacent tree ring and stalagmite records. Comparison of Lake Qinghai Holocene climate change sequence with those from high altitude ice core, stalagmites and ocean

  19. The orbital record in stratigraphy

    Science.gov (United States)

    Fischer, Alfred G.

    1992-01-01

    Orbital signals are being discovered in pre-Pleistocene sediments. Due to their hierarchical nature these cycle patterns are complex, and the imprecision of geochronology generally makes the assignment of stratigraphic cycles to specific orbital cycles uncertain, but in sequences such as the limnic Newark Group under study by Olsen and pelagic Cretaceous sequence worked on by our Italo-American group the relative frequencies yield a definitive match to the Milankovitch hierarchy. Due to the multiple ways in which climate impinges on depositional systems, the orbital signals are recorded in a multiplicity of parameters, and affect different sedimentary facies in different ways. In platform carbonates, for example, the chief effect is via sea-level variations (possibly tied to fluctuating ice volume), resulting in cycles of emergence and submergence. In limnic systems it finds its most dramatic expression in alternations of lake and playa conditions. Biogenic pelagic oozes such as chalks and the limestones derived from them display variations in the carbonate supplied by planktonic organisms such as coccolithophores and foraminifera, and also record variations in the aeration of bottom waters. Whereas early studies of stratigraphic cyclicity relied mainly on bedding variations visible in the field, present studies are supplementing these with instrumental scans of geochemical, paleontological, and geophysical parameters which yield quantitative curves amenable to time-series analysis; such analysis is, however, limited by problems of distorted time-scales. My own work has been largely concentrated on pelagic systems. In these, the sensitivity of pelagic organisms to climatic-oceanic changes, combined with the sensitivity of botton life to changes in oxygen availability (commonly much more restricted in the Past than now) has left cyclic patterns related to orbital forcing. These systems are further attractive because (1) they tend to offer depositional continuity

  20. Acquiring High to Ultra-High Resolution Geological Records of Past Climate Change by Scientific Drilling

    Directory of Open Access Journals (Sweden)

    Tomohisa Irino

    2009-09-01

    Full Text Available Scientific drilling on land and sea has played a key role in advancing our knowledge of climate change. It has helped to demonstrate the effects of orbital variations on climate, revealed evidence for extreme warm events in the past and for the timing of Antarctic ice growth, and provided insights into the hydrologic balance of lake systems around the world. Now, with attention increasingly focused on the likely manifestation of future climate change, the challenge to understand past climates at societally relevant, high-resolution timescales has become ever more critical. Sediments and other archives that preserve climate information ontimescales approaching those of instrumental records have much to offer to our understanding of how the climate system works (Fig. 1. These records, ideally with a sub-annual to centennial resolution, provide a unique opportunity to evaluate the global operation of the ocean-continent-atmosphere system on human timescales and to appraise the relative importance of each part of the system.

  1. Climate Change Detection in the UTLS with the GPS Radio Occultation Record

    Science.gov (United States)

    Steiner, A. K.; Kirchengast, G.; Lackner, B. C.; Hegerl, G. C.; Pirscher, B.; Foelsche, U.

    2009-12-01

    Radio Occultation (RO) based on signals from Global Positioning System (GPS) satellites provides a new climate record of high quality and vertical resolution in the upper troposphere and lower stratosphere (UTLS). RO data are considered a climate benchmark data type since they are based on timing with precise atomic clocks and tied to the international definition of the second. Long-term stability and the consistency of RO data stemming from different satellites (without need for inter-calibration) make RO well suited for climate change detection. RO data are available on a continuous basis from Sep 2001 to Sep 2008 from the CHAMP satellite and intermittent periods of observations from the GPS/Met proof-of-concept mission exist in the years 1995-1997, with sufficient data only for Oct 1995 and Feb 1997. We present a climate change detection study based on monthly mean zonal mean RO climatologies in the UTLS region within 9-25 km (300-30 hPa) where we use different detection methods. An optimal fingerprinting technique is applied to the whole record of RO accessible parameters refractivity, geopotential height, and temperature to detect a forced climate signal. Three representative global climate models of the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) are employed to estimate natural climate variability using pre-industrial control runs. The response pattern to the external forcings is presented by an ensemble mean of the models' A2 and B1 scenario runs. Optimal fingerprinting shows that a climate change signal can be detected in the RO refractivity and in the RO temperature record (90 % significance level). Furthermore, standard and multiple linear regression is applied to temperature time series for February (1997 and 2002-2008) and for October (1995 and 2001-2007), taking RO errors into account. In the tropics, we also investigate the influence of stratospheric quasi-biennial oscillation (QBO) and tropospheric El Nino

  2. Late Quaternary climate variability in the Sahel: inferences from marine dust records offshore Senegal

    Science.gov (United States)

    Stuut, J. W.; Meyer, I.; Fischer, H.; Mollenhauer, G.; Mulitza, S.; Pittauerova, D.; Zabel, M.; Schulz, M.

    2008-12-01

    Societies and ecosystems in northern Africa are strongly affected by the availability of water. As a consequence, long-term absence of rainfall has very dear effects on the ecosystems, as was dramatically shown in the 70'ies and 80'ies of the 20th century. Recent high-resolution reconstructions of Sahel palaeoclimate allow for new insights into these drastic climate variations and to disentangle the effects of the different components of the climate system on African climate change. In this study we extend the instrumental record of climate variability using marine sediment cores that were retrieved off the coast of Senegal, northwest Africa. The sediment records contain continuous high-resolution records of dust sedimentation ranging from about 4,000 to about 57,000 years. A 210Pb age model for the youngest sediments allows for a matching of the proxy rainfall record with instrumental precipitation data. Specifically, variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997) are used to reconstruct rainfall variability on land throughout the late Quaternary.

  3. Bottom-up effects of climate on fish populations: data from the Continuous Plankton Recorder

    DEFF Research Database (Denmark)

    Pitois, S.G.; Lynam, C.P.; Jansen, Teunis

    2012-01-01

    The Continuous Plankton Recorder (CPR) dataset on fish larvae has an extensive spatio-temporal coverage that allows the responses of fish populations to past changes in climate variability, including abrupt changes such as regime shifts, to be investigated. The newly available dataset offers...

  4. Evidence for general instability of past climate from a 250-KYR ice-core record

    DEFF Research Database (Denmark)

    Johnsen, Sigfus Johann; Clausen, Henrik Brink; Dahl-Jensen, Dorthe

    1993-01-01

     results1,2 from two ice cores drilled in central Greenland have revealed large, abrupt climate changes of at least regional extent during the late stages of the last glaciation, suggesting that climate in the North Atlantic region is able to reorganize itself rapidly, perhaps even within a few...... decades. Here we present a detailed stable-isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale. We find that climate instability was not confined to the last glaciation, but appears also to have been...... marked during the last interglacial (as explored more fully in a companion paper3) and during the previous Saale-Holstein glacial cycle. This is in contrast with the extreme stability of the Holocene, suggesting that recent climate stability may be the exception rather than the rule. The last...

  5. Ice cores record significant 1940s Antarctic warmth related to tropical climate variability.

    Science.gov (United States)

    Schneider, David P; Steig, Eric J

    2008-08-26

    Although the 20th Century warming of global climate is well known, climate change in the high-latitude Southern Hemisphere (SH), especially in the first half of the century, remains poorly documented. We present a composite of water stable isotope data from high-resolution ice cores from the West Antarctic Ice Sheet. This record, representative of West Antarctic surface temperature, shows extreme positive anomalies in the 1936-45 decade that are significant in the context of the background 20th Century warming trend. We interpret these anomalies--previously undocumented in the high-latitude SH--as indicative of strong teleconnections in part driven by the major 1939-42 El Niño. These anomalies are coherent with tropical sea-surface temperature, mean SH air temperature, and North Pacific sea-level pressure, underscoring the sensitivity of West Antarctica's climate, and potentially its ice sheet, to large-scale changes in the global climate.

  6. Late Holocene climate and environmental changes in Kamchatka inferred from the subfossil chironomid record

    Science.gov (United States)

    Nazarova, Larisa; de Hoog, Verena; Hoff, Ulrike; Dirksen, Oleg; Diekmann, Bernhard

    2013-05-01

    This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomid remains from a 332 cm long composite sediment core recovered from Dvuyurtochnoe Lake (Two-Yurts Lake, TYL) in central Kamchatka. The oldest recovered sediments date to about 4500 cal years BP. Chironomid head capsules from TYL reflect a rich and diverse fauna. An unknown morphotype of Tanytarsini, Tanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomid assemblage zones reflecting four different climatic periods in the Late Holocene. Between 4500 and 4000 cal years BP, the chironomid composition indicates a high lake level, well-oxygenated lake water conditions and close to modern temperatures (˜13 °C). From 4000 to 1000 cal years BP, two consecutive warm intervals were recorded, with the highest reconstructed temperature reaching 16.8 °C between 3700 and 2800 cal years BP. Cooling trend, started around 1100 cal years BP led to low temperatures during the last stage of the Holocene. Comparison with other regional studies has shown that termination of cooling at the beginning of late Holocene is relatively synchronous in central Kamchatka, South Kurile, Bering and Japanese Islands and take place around 3700 cal years BP. From ca 3700 cal years BP to the last millennium, a newly strengthened climate continentality accompanied by general warming trend with minor cool excursions led to apparent spatial heterogeneity of climatic patterns in the region. Some timing differences in climatic changes reconstructed from chironomid record of TYL sediments and late Holocene events reconstructed from other sites and other proxies might be linked to differences in local forcing mechanisms or caused by the different degree of dating precision, the different temporal resolution, and the different sensitive responses of climate proxies to the climate variations. Further high-resolution stratigraphic studies in this region are needed to understand

  7. Long-term measurements of solar spectral irradiance variability: toward the establishment of a climate record

    Science.gov (United States)

    Richard, Erik; Harder, Jerald; Pilewskie, Peter; Fontenla, Juan; Woods, Thomas; Brown, Steven; Lykke, Keith

    Knowledge of the top of the atmosphere (TOA) solar spectral irradiance (SSI) is crucial in interpreting the spectrally dependent radiative processes throughout Earth's climate system. Where this energy is deposited into the atmosphere and surface, how the climate responds to solar variability, and the mechanisms of climate response, are highly dependent on how the incident solar radiation is distributed with wavelength. In order to advance understanding of how natural and anthropogenic process affect Earth's climate system there is a strong scientific imperative to maintain accurate, long-term records of climate forcing and response. The contin-uation of SSI measurements provides a unique opportunity to characterize poorly understood wavelength dependent climate processes. Coupled chemistry-climate models require realistic assessments of the magnitudes and long-term trends in SSI for the interpretation and quantifi-cation of solar forcing in climate change scenarios. This places stringent requirements on the absolute calibration of the instrument (tied directly to international standards) and the ability to maintain that calibration on-orbit (long-term stability). The Spectral Irradiance Monitor (SIM) is a solar spectral radiometer that continuously monitors the SSI from 200 nm -2400 nm, a wavelength region encompassing 96% of the total solar irradiance. The SIM instrument is included as part of the Total and Spectral Solar Irradiance Sensor (TSIS) to continue the mea-surement of SSI, which began with the SOlar Radiation and Climate Experiment (SORCE), launched in 2003. SORCE SIM measurements have characterized SSI variability during the descending phase of Solar Cycle (SC) 23, but the determination of multi-solar cycle dependen-cies remains a key climatic uncertainty. Analysis of the measured spectral irradiance variability during the SORCE mission has resulted in a number of instrument design refinements central to maintaining, on-orbit, the long-term absolute

  8. The new climate data record of total and spectral solar irradiance: Current progress and future steps

    Science.gov (United States)

    Coddington, Odele; Lean, Judith; Rottman, Gary; Pilewskie, Peter; Snow, Martin; Lindholm, Doug

    2016-04-01

    We present a climate data record of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI), with associated time and wavelength dependent uncertainties, from 1610 to the present. The data record was developed jointly by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder and the Naval Research Laboratory (NRL) as part of the National Oceanographic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) Climate Data Record (CDR) Program, where the data record, source code, and supporting documentation are archived. TSI and SSI are constructed from models that determine the changes from quiet Sun conditions arising from bright faculae and dark sunspots on the solar disk using linear regression of proxies of solar magnetic activity with observations from the SOlar Radiation and Climate Experiment (SORCE) Total Irradiance Monitor (TIM), Spectral Irradiance Monitor (SIM), and SOlar Stellar Irradiance Comparison Experiment (SOLSTICE). We show that TSI can be separately modeled to within TIM's measurement accuracy from solar rotational to solar cycle time scales and we assume that SSI measurements are reliable on solar rotational time scales. We discuss the model formulation, uncertainty estimates, and operational implementation and present comparisons of the modeled TSI and SSI with the measurement record and with other solar irradiance models. We also discuss ongoing work to assess the sensitivity of the modeled irradiances to model assumptions, namely, the scaling of solar variability from rotational-to-cycle time scales and the representation of the sunspot darkening index.

  9. Climatic variations since the Little Ice Age recorded in the Guliya Ice Core

    Institute of Scientific and Technical Information of China (English)

    姚檀栋; 焦克勤; 田立德; 杨志红; 施维林; Lonnie G. Thompson

    1996-01-01

    The climatic variations since the Little Ice Age recorded in the Guliya Ice Core are discussed based on glacial δ18O and accumulation records in the Guliya Ice Core. Several obvious climate fluctuation events since 1570 can be observed according to the records. In the past 400 years, the 17th and 19th centuries are relatively cool periods with less precipitation, and the 18th and 20th centuries are relatively warm periods with high precipitation. The study has also revealed the close relationship between temperature and precipitation on the plateau. Warming corresponds to high precipitation and cooling corresponds to less precipitation, which is related with the influence of monsoon on this region.

  10. Late Holocene climate variability in the Sahel: inferences from a marine dust record offshore Senegal

    Science.gov (United States)

    Stuut, Jan-Berend; Mulitza, Stefan; Heslop, David; Pittauerova, Daniela; Fischer, Helmut; Zabel, Matthias; Collins, James; Kuhnert, Henning; Mollenhauer, Gesine; Meyer, Inka

    2010-05-01

    Societies and ecosystems in northern Africa are strongly affected by the availability of water. As a consequence, long-term absence of rainfall has very dear effects on the ecosystems, as was dramatically shown in the 70'ies and 80'ies of the 20 century. Recent high-resolution reconstructions of Sahel palaeoclimate allow for new insights into these drastic climate variations and to disentangle the effects of the different components of the climate system on African climate change. In this study we extend the instrumental record of climate variability using a marine sediment core that was retrieved off the coast of Senegal, northwest Africa. The 530-cm long record covers the last 4,000 years continuously. A Pb age model allows for a matching of the proxy record with instrumental data. Specifically, variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997) are used to reconstruct rainfall variability on land. In addition, chemical data are used to study the effect of human-induced dust production throughout the late Holocene. We show that dust deposition is closely related to monsoonal precipitation in West Africa until the 17th century AD, followed by a sharp increase in dust deposition at the beginning of the 18th century. We hypothesise that this increase in dust mobilisation is related to the advent of commercial agriculture in the Sahel region.

  11. Continuous 500,000-year climate record from vein calcite in Devils Hole, Nevada

    Science.gov (United States)

    Winograd, I.J.; Coplen, T.B.; Landwehr, J.M.; Riggs, A.C.; Ludwig, K. R.; Szabo, B. J.; Kolesar, Peter T.; Revesz, K.M.

    1992-01-01

    Oxygen-18 (??18O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine ??18O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

  12. Continuous 500,000-year climate record from vein calcite in devils hole, nevada.

    Science.gov (United States)

    Winograd, I J; Coplen, T B; Landwehr, J M; Riggs, A C; Ludwig, K R; Szabo, B J; Kolesar, P T; Revesz, K M

    1992-10-09

    Oxygen-18 (delta(18)O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine delta(18)O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

  13. Supporting Private Sector Decision-Making with NOAA's Interim Climate Data Records (ICDRs)

    Science.gov (United States)

    Privette, J. L.; Glance, W. J.; Cecil, D.; Bates, J. J.

    2012-12-01

    NOAA initiated its Climate Data Record Program (CDRP) in 2009 to operationally provide authoritative satellite Climate Data Records (CDRs) to the government and the private sector. The CDRs are based primarily on 35+ years of meteorological satellite and in situ data collected by NOAA and the Department of Defense. To date, the Program has transitioned 14 CDRs from research to initial operations. In the past year, the CDRP developed and implemented a framework to continuously extend historical CDRs using Interim Climate Data Records (ICDRs). ICDRs are "first batch" CDRs generated within several days of observation using official CDR algorithms and processes. ICDRs are required by decision support systems and other near-term applications which need current data that are fully consistent with homogeneous historical records. For example, an electrical power utility may need temperature and precipitation ICDRs to optimally identify, in both time and space, the "nearest" historical analog period to recent weather. The utility could then use the contemporaneous business data from that period to inform current decision-making. In addition to their homogeneity and consistency, ICDRs are more complete than operational weather products since ICDR processing can await upstream data delays that can negate data value for weather forecasting. However, the operational nature of ICDRs means their uncertainties typically can be improved through reprocessing once better sensor calibration and characterization data become available. Therefore, ICDRs may be considered valuable but temporary placeholders. However, the "trigger" for electing to update a given record involves many considerations, including cost, latency, downstream dependencies and scientific significance. This presentation provides an update on NOAA's CDR Program, focusing on the new CDRs transitioned to operations in 2012 and the ICDR framework -- including update decision criteria -- used to extend CDRs and meet the

  14. GCOS reference upper air network (GRUAN): Steps towards assuring future climate records

    Science.gov (United States)

    Thorne, P. W.; Vömel, H.; Bodeker, G.; Sommer, M.; Apituley, A.; Berger, F.; Bojinski, S.; Braathen, G.; Calpini, B.; Demoz, B.; Diamond, H. J.; Dykema, J.; Fassò, A.; Fujiwara, M.; Gardiner, T.; Hurst, D.; Leblanc, T.; Madonna, F.; Merlone, A.; Mikalsen, A.; Miller, C. D.; Reale, T.; Rannat, K.; Richter, C.; Seidel, D. J.; Shiotani, M.; Sisterson, D.; Tan, D. G. H.; Vose, R. S.; Voyles, J.; Wang, J.; Whiteman, D. N.; Williams, S.

    2013-09-01

    The observational climate record is a cornerstone of our scientific understanding of climate changes and their potential causes. Existing observing networks have been designed largely in support of operational weather forecasting and continue to be run in this mode. Coverage and timeliness are often higher priorities than absolute traceability and accuracy. Changes in instrumentation used in the observing system, as well as in operating procedures, are frequent, rarely adequately documented and their impacts poorly quantified. For monitoring changes in upper-air climate, which is achieved through in-situ soundings and more recently satellites and ground-based remote sensing, the net result has been trend uncertainties as large as, or larger than, the expected emergent signals of climate change. This is more than simply academic with the tropospheric temperature trends issue having been the subject of intense debate, two international assessment reports and several US congressional hearings. For more than a decade the international climate science community has been calling for the instigation of a network of reference quality measurements to reduce uncertainty in our climate monitoring capabilities. This paper provides a brief history of GRUAN developments to date and outlines future plans. Such reference networks can only be achieved and maintained with strong continuing input from the global metrological community.

  15. Solving the Global Climate Monitoring Problem in the Atmosphere: Towards SI-tied Climate Records with Integrated Uncertainty Propagation

    Science.gov (United States)

    Kirchengast, G.; Schwaerz, M.; Fritzer, J.; Schwarz, J.; Scherllin-Pirscher, B.; Steiner, A. K.

    2013-12-01

    Monitoring the atmosphere to gain accurate and long-term stable records of essential climate variables (ECVs) such as temperature and greenhouse gases is the backbone of contemporary atmospheric and climate science. Earth observation from space is the key to obtain such data globally in the atmosphere. Currently, however, not any existing satellite-based atmospheric ECV record can serve as authoritative benchmark over months to decades so that climate variability and change in the atmosphere are not yet reliably monitored. Radio occultation (RO) using Global Navigation Satellite System (GNSS) signals provides a unique opportunity to solve this problem in the free atmosphere (from ~1-2 km altitude upwards) for core ECVs: the thermodynamic variables temperature and pressure, and to some degree water vapor, which are key parameters for tracking climate change. On top of RO we have recently conceived next-generation methods, microwave and infrared-laser occultation and nadir-looking infrared-laser reflectometry. These can monitor a full set of thermo-dynamic ECVs (incl. wind) as well as the greenhouse gases such as carbon dioxide and methane as main drivers of climate change; for the latter we also target the boundary layer for tracking carbon sources and sinks. We briefly introduce to why the atmospheric climate monitoring challenge is unsolved so far and why just the above methods have the capabilities to break through. We then focus on RO, which already provided more than a decade of observations. RO accurately measures time delays from refraction of GNSS signals during atmospheric occultation events. This enables to tie RO-derived ECVs and their uncertainty to fundamental time standards, effectively the SI second, and to their unique long-term stability and narrow uncertainty. However, despite impressive advances since the pioneering RO mission GPS/Met in the mid-1990ties no rigorous trace from fundamental time to the ECVs (duly accounting also for relevant side

  16. Climate or land-use change? Complexities in the attribution of trends in river flow records

    Science.gov (United States)

    Harrigan, S.; Murphy, C.; Noone, S.; Wilby, R. L.; Hall, J.

    2012-12-01

    Uncertainty associated with projections of regional climate change and the challenge of developing adaptation responses are heightening interest in trend detection from observations. In many studies, attribution of detected trends in river flow has been based on the assessment of correlations with large scale modes of climate variability, with too little emphasis being placed on understanding non-climatic changes within the catchment. The River Boyne in Ireland has been cited as exhibiting a climate driven increase in river flows associated with a shift towards positive anomalies in the North Atlantic Oscillation Index (NAOI) from the mid to late 1970s. However, metadata suggests that the catchment was subjected to extensive arterial drainage during the period 1969-86. This was installed to improve land drainage and reduce the frequency/ extent of overland flooding, particularly through river straightening and channel deepening, complicating the attribution of change linked to climatic drivers. This study uses river flow records from the pre-drainage period along with meteorological data to calibrate conceptual rainfall runoff models in order to reconstruct continuous flow series spanning the pre- and post-drainage eras. Model parameter and structure uncertainties were explored via a suite of conceptually and structurally diverse models. Archival rainfall records dating from the late 1800s were used to further extend the flow series. Reconstructed flows are analyzed for both monotonic and step changes using a variety of statistical tests. Emphasis is placed on a moving windows approach to assess the evolution of trends throughout the reconstructed series. Our results show that the variability of trends (direction, magnitude and significance) is heavily dependent on the choice of record start and end dates. Rather than being associated with a change point in the NAOI, the mid 1970s step change is shown to coincide with the documented changes in arterial drainage

  17. Climatic changes on millennial time scales--Evidence from a high-resolution loess record

    Institute of Scientific and Technical Information of China (English)

    任剑璋; 丁仲礼; 刘东生; 孙继敏; 周晓权

    1996-01-01

    Studies on a high resolution loess section in Huining County reveal that the behavior of climate shows high instability during the last glaciation. Results reflect that climate in Loess Plateau oscillates on millennial time scales during the last glacial period. These can be teleconnected with the records of Dansgaard-Oeschger cycles and Heinrich events in high latitudes. Results also demonstrate that variations in the intensity of wind regime on the Loess Plateau have a close correlation with the changes of global ice sheets volume. All these suggest that two-level fordngs may drive climate changes in central Asia. The first level is the volume changes of ice sheets and the second level with short time scales is superimposed upon the first level on a nearly global scale.

  18. Peat record reflecting Holocene climatic change in the Zoige Plateau and AMS radiocarbon dating

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Through the use of reliable AMS dating of high resolution (15-30 years) peat and the establishment of monsoon climate proxies sequence, we have been able to recognize several cold, dry events in the Tibetan Plateau during the Holocene. The more obvious ones occurred around 12800, 11300, 10200, 9580, 8900, 6400, 4400, 3700, 2800 and 1500 cal. aBP. These events correlate well with both ice rafting events recorded in high latitude North Atlantic Ocean sediment cores and cooling events in the low latitude SST. Spectral analysis indicates high frequency climate variation on centennial-millennial time scale during the Holocene. This further reflects Holocene climate instability and the existence of centennial-millenium scale rhythm in mid latitude areas as well.

  19. Third Pole Glaciers and Ice Core Records of Past, Present and Future Climate

    Science.gov (United States)

    Thompson, L. G.; Yao, T.; Mosley-Thompson, E. S.; Davis, M. E.

    2011-12-01

    Ice core histories collected over the last two decades from across the Tibetan Plateau and the Himalaya demonstrate the climatic complexity and diversity of the Third Pole (TP) region. Proxy climate records spanning more than 500,000 years have been recovered from the Guliya ice cap in the far northwestern Kunlun Shan, which is dominated by westerly air flow over the Eurasian land mass. Shorter records (central TP, and also in the Himalaya to the south where a monsoonal climate regime dominates and the annual accumulation is high. The Himalayan ice fields are sensitive to fluctuations in the intensity of the South Asian Monsoon and are affected by the rising temperatures in the region. We examine the recent climatic changes to earlier distinctive epochs such as the Medieval Climate Anomaly (~950-1250 AD), the early Holocene "Hypsithermal" (~5 to 9 kyr BP) and the Eemian (~114 -130 kyr BP). The Eemian, the most recent period when Earth was significantly warmer than today, can serve in part as an analog for the coming greenhouse world. One thousand-year records of δ18O variations from four of these ice fields illustrate the effect of the recent warming across the TP. Mean values for much of the 20th Century (AD 1938 to 1987) are compared with those for the prior nine centuries (1000 to 1937 AD). The greatest recent enrichment occurs on the highest elevation site (Dasuopu in the Himalaya), presumably where the greatest warming is occurring. These trends are consistent with instrumental temperature records collected since the 1950s across the TP as well as with IPCC (2007) model predictions of a nearly two-fold vertical amplification of temperatures in the Tropics. A fifth ice field, Naimona'nyi (6100 masl), is not included in the study as recent melting from the top of the glacier has obliterated the upper 40 to 50 years of the record. Evidence confirming this will be presented along with recent mass balance measurements indicating that no net accumulation occurs on

  20. Annually resolved ice core records of tropical climate variability over the past ~1800 years.

    Science.gov (United States)

    Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

    2013-05-24

    Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

  1. Using image reconstruction methods to enhance gridded resolutionfor a newly calibrated passive microwave climate data record

    Science.gov (United States)

    Paget, A. C.; Brodzik, M. J.; Gotberg, J.; Hardman, M.; Long, D. G.

    2014-12-01

    Spanning over 35 years of Earth observations, satellite passive microwave sensors have generated a near-daily, multi-channel brightness temperature record of observations. Critical to describing and understanding Earth system hydrologic and cryospheric parameters, data products derived from the passive microwave record include precipitation, soil moisture, surface water, vegetation, snow water equivalent, sea ice concentration and sea ice motion. While swath data are valuable to oceanographers due to the temporal scales of ocean phenomena, gridded data are more valuable to researchers interested in derived parameters at fixed locations through time and are widely used in climate studies. We are applying recent developments in image reconstruction methods to produce a systematically reprocessed historical time series NASA MEaSUREs Earth System Data Record, at higher spatial resolutions than have previously been available, for the entire SMMR, SSM/I-SSMIS and AMSR-E record. We take advantage of recently released, recalibrated SSM/I-SSMIS swath format Fundamental Climate Data Records. Our presentation will compare and contrast the two candidate image reconstruction techniques we are evaluating: Backus-Gilbert (BG) interpolation and a radiometer version of Scatterometer Image Reconstruction (SIR). Both BG and SIR use regularization to trade off noise and resolution. We discuss our rationale for the respective algorithm parameters we have selected, compare results and computational costs, and include prototype SSM/I images at enhanced resolutions of up to 3 km. We include a sensitivity analysis for estimating sensor measurement response functions critical to both methods.

  2. Abrupt climate changes of the last deglaciation detected in a western Mediterranean forest record

    Directory of Open Access Journals (Sweden)

    W. J. Fletcher

    2009-01-01

    Full Text Available Evidence for abrupt changes in western Mediterranean climate between 20 and 6 cal ka BP is examined in marine core MD95-2043 (Alborán Sea, using pollen data for temperate Mediterranean forest development and pollen-based climate reconstructions using the modern analogue technique (MAT for annual precipitation (Pann and mean temperatures of the coldest and warmest months (MTCO and MTWA. Major climatic shifts with parallel temperature and precipitation changes occurred at the onsets of Heinrich Event 1 (equivalent to the Oldest Dryas, the Bölling-Allerød (BA, and the Younger Dryas (YD. Multi-centennial-scale oscillations in forest development related to regional precipitation (Pann variability occurred throughout the BA, YD, and early Holocene, with drier atmospheric conditions in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas, GI-1b (Intra-Allerød Cold Period and GS-1 (YD, and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting (events at 11.4, 10.1, 9.3, 8.2 and 7.4 cal ka BP. The forest record also indicates multi-centennial variability within the YD interval and multiple Preboreal climate oscillations. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to western-central Europe relates to the dynamics of the jet stream and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alborán Sea by ~200 years (surface water age ~600 years during the Lateglacial.

  3. High-resolution terrestrial record of orbital climate forcing in coal

    Energy Technology Data Exchange (ETDEWEB)

    Large, D.J.; Jones, T.F.; Somerfield, C.; Gorringe, M.C.; Spiro, B.; Macquaker, J.H.S.; Atkin, B.P. [University of Nottingham, Nottingham (United Kingdom). School of Chemical Environmental & Mining Engineering

    2003-04-01

    Pre-Quaternary terrestrial climate records in which time has been calibrated using astronomical cycles are, with the exception of lacustrine proxies, poorly represented in the geological record. This omission is a significant gap in our knowledge of ancient climate systems. Here the authors present new evidence of orbital periodicities in an 18.3-m-thick late Paleocene coal and conclude that coal has the potential to provide continuous time-calibrated terrestrial climate data. Spectral analysis of changes in the relative proportions of vitrinite to inertinite, two environmentally sensitive coal macerals, reveals several characteristic frequencies, some of which display evidence of amplitude modulation every five to six cycles. Combining this observation with depositional time limitations derived from present-day rates of carbon accumulation in mires, the characteristic frequencies as resulting from precession and obliquity and their influence on oxidation and decay are interpreted. Using the inferred precession component of the data to derive an internal time scale, it is estimated that the Wyodak coal was deposited over a period of similar to 414 k.y. with a long-term carbon sequestration rate of 29 g m{sup -2} yr{sup -1}. The identification of an internal astronomical time scale in coal is an important step toward realizing the potential for coal to extend our high-resolution knowledge of Earth's terrestrial climate back to the formation of the first peat deposits at 360 Ma.

  4. Reconstruction of climate in China during 17th-19th centuries using Chinese chronological records

    Science.gov (United States)

    Wang, Pao; Lin, Kuan-Hui; Liao, Yi-Chun; Lee, Shih-Yu; Liao, Hsiung-Ming; Pai, Pi-Ling; Fan, I.-Chun

    2017-04-01

    Chinese historical documents are an extremely useful source from which much climate information can be retrieved if treated carefully. This is especially relevant to the reconstruction of climate in East Asia in the last 2000 years as the Chinese has kept official chronicles since 500BC and China also represents a large portion of East Asia's land. In addition, there are also local records in many cities and counties. When available, such documentary sources are often superior to environmental proxy data, especially in the time resolution as they usually provide at least annual resolution and even as high as daily records in some cases. This research will report on our recent advances on using a new REACHS dataset that collects primarily documented meteorological records from thousands of imperial and local chronicles in the Chinese history for more than 2000 years. The meteorological records were digitized and coded in the relational database management system in which accurate time (from yearly to daily), space (from province to city/county) and event (from meteorological to phonological and social) information is carefully reserved for analysis. We then formed digital climate series and performed time series and spatial analysis on them to obtain their temporal and spatial characteristics. Our present research results on the annual and seasonal temperature reconstruction during 17th-19th indicates lower temperature in the 17th century. There were also strangely high occurrence frequency of summer snowfall records in the lower reaches of Yangtze River during the Maunder Minimum. Reconstructed precipitation series fluctuated with strong regional character in the Northeast, Central-east and Southeast China. Spectral analysis shows that precipitation series have significant periodicity of 3-5 and 8-12 years during the period, suggesting strong interannual variability and different regional signatures. Flood happened frequently but long lasting drought was more

  5. A pathway to generating Climate Data Records of sea-surface temperature from satellite measurements

    Science.gov (United States)

    Minnett, Peter J.; Corlett, Gary K.

    2012-11-01

    In addition to having known uncertainty characteristics, Climate Data Records (CDRs) of geophysical variables derived from satellite measurements must be of sufficient length to resolve signals that might reveal the signatures of climate change against a background of larger, unrelated variability. The length of the record requires using satellite measurements from many instruments over several decades, and the uncertainty requirement implies that a consistent approach be used to establish the errors in the satellite retrievals over the entire period. Retrieving sea-surface temperature (SST) from satellite is a relatively mature topic, and the uncertainties of satellite retrievals are determined by comparison with collocated independent measurements. To avoid the complicating effects of near-surface temperature gradients in the upper ocean, the best validating measurements are from ship-board radiometers that measure, at source, the surface emission that is measured in space, after modification by its propagation through the atmosphere. To attain sufficient accuracy, such ship-based radiometers must use internal blackbody calibration targets, but to determine the uncertainties in these radiometric measurements, i.e. to confirm that the internal calibration is effective, it is necessary to conduct verification of the field calibration using independent blackbodies with accurately known emissivity and at very accurately measured temperatures. This is a well-justifiable approach to providing the necessary underpinning of a Climate Data Record of SST.

  6. Atmospheric Climate Change Detection Based on the GPS Radio Occultation Record

    Science.gov (United States)

    Steiner, A. K.; Lackner, B. C.; Hegerl, G. C.; Pirscher, B.; Borsche, M.; Foelsche, U.; Kirchengast, G.

    2009-04-01

    Monitoring of global climate change requires high quality observations of the Earth's atmosphere. Radio occultation (RO) measurements based on signals from Global Positioning System (GPS) satellites provide a useful upper air record in this respect. RO data are considered a climate benchmark data type since they are based on timing with precise atomic clocks and tied to the international definition of the second. High quality and vertical resolution in the upper troposphere and lower stratosphere (UTLS), long-term stability, and consistency of RO data stemming from satellites in different orbits without need for inter-calibration make RO well suited for atmospheric observations and climate change detection. RO data are available on a continuous basis since fall of 2001 from the German research satellite CHAMP (CHAllenging Minisatellite Payload for geoscientific research), establishing the first RO climate record covering more than seven years. Intermittent periods of observations from the U.S. GPS/Met proof-of-concept mission exist in the years 1995-1997, with sufficient data only for October 1995 and February 1997. We present a climate change detection study based on monthly mean zonal mean RO climatologies in the UTLS region within 9-25 km (300-30 hPa) where we use different detection methods. An optimal fingerprinting technique is applied to the whole record of RO accessible parameters refractivity, geopotential height, and temperature to detect a forced climate signal. Three representative global climate models of the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) are employed to estimate natural climate variability by making use of pre-industrial control runs. The response pattern to the external forcings is presented by an ensemble mean of the models' A2 and B1 scenario runs. Optimal fingerprinting shows that a climate change signal can be detected at the 90% significance level in the RO refractivity record. Furthermore, simple

  7. A 16000-year pollen record of Qinghai Lake and its paleo-climate and paleoenvironment

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The paleoclimate and paleoenvironment of Qinghai Lake indicated by a 16000-year pollen record are as follows. It was very cold and dry before 15200 years. During the Late Glacial, the climate varied from colder and semiarid to cool and semi-humid and fluctuated frequently but with little amplitude. Three cold events in the periods of 13400-13000, 11600-12000, and 11000-10400 aBP respectively correspond to the Oldest Dryas, Older Dryas and Younger Dryas events, whereas the two warm periods between them, 12000-13000 and 11600-11000 aBP, respectively correspond to B?lling and Aller?d periods. The temperature increased abruptly after the Younger Dryas event, and then the climate gradually turned to be warm and wet from warm and semiarid. In the Holocene, the largest amplitude of cold event that occurred at ca. 8200 aBP is quite prominent.. The Holocene climatic optimum culminated at 6700 aBP. After 2100 aBP, the climate tended to be cold and dry, keeping on up to now. Palaeoclimatic evolution and events of Qinghai Lake based on pollen assemblage and concentrations can be well parallel with the global climatic events.

  8. Towards understanding North Pacific climate variabilty with instrumental and ice core records

    Science.gov (United States)

    Kelsey, Eric P.

    Reconstructing climate variability prior to the instrumental era is critical to advance our understanding of the Earth's climate system. Although many paleoclimate records from the North Atlantic basin have been studied, relatively few paleoclimate records have been recovered in the North Pacific leaving a gap in our knowledge concerning North Pacific climate variability. The Eclipse and Mount Logan Prospector-Russell ice cores are favorably located in the St. Elias Mountains, Yukon, Canada to document North Pacific climate variability over the late Holocene. Detailed analysis reveals a consistent relationship of surface air temperature (SAT) anomalies associated with extreme Arctic Oscillation (AO) and Pacific-North America (PNA) index values, and a consistent relationship of North Pacific sea level pressure (SLP) anomalies associated with extreme Mt. Logan annual [Na+] and Eclipse cold season accumulation values. Spatial SAT anomaly patterns are most consistent for AO and PNA index values ≥1.5 and ≤-1.5 during the period 1872-2010. The highest and lowest ˜10% of Eclipse warm and cold season stable isotopes are associated with distinct atmospheric circulation patterns. The most-fractionated isotope values occur with a weaker Aleutian Low, and the least-fractionated isotope values occur with an amplification of the Aleutian Low and northwestern North American ridge. The assumption of stationarity between ice core records and sea-level pressure was tested for the Eclipse cold season accumulation and Mt. Logan annual sodium concentration records for 1872-2001. A stationary relationship was found for ≥95% of years when Mt. Logan sodium concentrations were ≤1.32 microg/L, with positive SLP anomalies in the eastern North Pacific. This high frequency supports the use of low sodium values at Mt. Logan for a reconstruction of SLP prior to 1872. Negative SLP anomalies in the North Pacific occurred for extreme high sodium concentration years and positive SLP

  9. Climate instability during the last glaciation recorded in the Yuanbu loess section

    Institute of Scientific and Technical Information of China (English)

    Yimeng Chen

    2009-01-01

    Abrupt events within the Linxia Yuanbu loess section in the western Loess Plateau in China were investigated.The climatic proxy index of the content of mean grain-size and>4 μm grain-size fraction of the section was used as a climatic indicator,and a moving average method was applied in the statistical analysis to extract the abrupt events recorded in the section.It was found that the loess of the last glaciation recorded not only the abrupt events teleconnected with the high-latitude North Atlantic and Greenland regions but also as many as 15 abrupt events in addition to the Heinrich (H) and Younger Dryas (YD) events.This indicates that abrupt climate changes were typical of the climate changes occurring in the Loess Plateau during the last glaciation.The widely recognized mechanisms of the abrupt climate changes,including the heat transfer theory of the North Atlantic Ocean,the atmospheric circulation theory,and the theory of the interaction between low-latitude ocean and the atmosphere remains to be discussed.Perhaps this problem could be resolved by revealing the relation between the evolution of the features of the East Asian monsoon climate and the climate in the surrounding areas.Through a detailed study of the features of the Heinrich and YD events,criteria on which the abrupt events recorded in the loess could be distinguished were tentatively defined.The events were associated with a large grain size,high carbonate content,high lightness,low susceptibility,low redness and low yellowness.In addition,the variation amplitude of the adjacent peak and valley on the curve of the content of the mean grain-size and>40μm grain-size fraction was larger than 3.4μm and the content of >40μm grain-size fraction was larger than 2.0μm.Lastly,the length of the variation time was less than 500 years.If all these criteria were met,the event was viewed as an abrupt event.

  10. Northern and southern hemispheric climate records from the western tropical Pacific during MIS3

    Science.gov (United States)

    Saikku, R.; Stott, L.

    2008-12-01

    During MIS3 Mg/Ca-derived SSTs and planktonic δ18O changed by up to 0.6‰ and 2°C respectively in the western tropical Pacific (MD98-2181). This marine record located at 6.3°N correlates well with millennial-scale variations in the NGRIP ice core and Hulu Cave stalagmite records reflecting hydrographic changes in the western Pacific warm pool that are linked to Monsoon and Northern Hemisphere climate variability. Stronger summer monsoon and increased summer precipitation at Hulu Cave and warmer conditions in Greenland coincided with fresher and warmer conditions at MD98-2181. Due to the ideal core location, the benthic isotopic record from MD98-2181 is a record of upper Pacific Deep Water temperature and salinity variability. The benthic δ18O record documents large millennial-scale oscillations of between 0.3-0.5‰ that correlate closely with the Antarctic surface temperature history. This suggests deep water that reached the core site was changing temperature by up to ~1-1.5°C with the possibility that some of this variability reflects changes in salinity and minor glacial-eustatic changes. We interpret these changes of deepwater properties to reflect transient changes in the source water region where Upper Circumpolar Deep Water forms or as vertical migration of the water mass boundary between Upper and Lower Circumpolar Deep Water. The combined planktonic and benthic records from MD98-2181 thus provide a northern and southern hemispheric climate record and thus verify the anti-phased relationship associated with a bi-polar seesaw oceanographic behavior throughout MIS3.

  11. The Towuti Drilling Project: A new, long Pleistocene record of Indo-Pacific Climate

    Science.gov (United States)

    Russell, James M.; Vogel, Hendrik; Bijaksana, Satria; Melles, Martin

    2016-04-01

    Lake Towuti is the largest tectonic lake in Indonesia, and the longest known terrestrial sediment archive in Southeast Asia. Lake Towuti's location in central Indonesia provides an important opportunity to reconstruct long-term changes in terrestrial climate in the Western Pacific warm pool, heart of the El Niño-Southern Oscillation. Lake Towuti has extremely high rates of floral and faunal endemism and is surrounded by one of the most diverse tropical forests on Earth making it a hotspot of Southeast Asian biodiversity. The ultramafic rocks and soils surrounding Lake Towuti provide high concentrations of metals to the lake and its sediments that feed a diverse, exotic microbial community. From May - July, 2015, the Towuti Drilling Project, consisting of more than 30 scientists from eight countries, recovered over 1,000 meters of new sediment core from 3 different drill sites in Lake Towuti, including cores through the entire sediment column to bedrock. These new sediment cores will allow us to investigate the history of rainfall and temperature in central Indonesia, long-term changes in the composition of the region's rainforests and diverse aquatic ecosystems, and the micro-organisms living in Towuti's exotic, metal-rich sediments. The Indo-Pacific region plays a pivotal role in the Earth's climate system, regulating critical atmospheric circulation systems and the global concentration of atmospheric water vapor- the Earth's most important greenhouse gas. Changes in seasonal insolation, greenhouse gas concentrations, ice volume, and local sea level are each hypothesized to exert a dominant control on Indo-Pacific hydroclimate variations through the Pleistocene. Existing records from the region are short and exhibit fundamental differences and complexity in orbital-scale climate patterns that limit our understanding of the regional climate responses to climate boundary conditions. Our sediment cores, which span much of the past 1 million years, allow new tests of

  12. Holocene climatic and environmental change from pollen records of Mexican lakes Zempoala and Quila. Central Mexican highlands

    NARCIS (Netherlands)

    Almeida Lenero, L.; Hooghiemstra, H.; Cleef, A.M.; Geel, van B.

    2005-01-01

    Pollen records of a 520-cm long core from Lake Zempoala (2800 m altitude) and a 884-cm long composite core from Lake Quila (3010 m altitude), both located 65 km SW of Mexico City, show changes in vegetation and climate. The Zempoala record covers the last c. 6320 cal yr BP, while the Quila record sp

  13. a Marine Record of Holocene Climate Events in Tropical South America

    Science.gov (United States)

    Haug, G. H.; Günther, D.; Hughen, K. A.; Peterson, L. C.; Röhl, U.

    2002-12-01

    Metal concentration data (Ti, Fe) from the anoxic Cariaco Basin off the Venezuelan coast record with subdecadal to seasonal resolution variations in the hydrological cycle over tropical South America during the last 14 ka. Following a dry Younger Dryas, a period of increased precipitation and riverine discharge occurred during the Holocene `thermal maximum'. Since ~5.4 ka, a trend towards drier conditions is evident from the data, with high amplitude fluctuations and precipitation minima during the time interval 3.8 to 2.8 ka and during the `Little Ice Age'. O pronouced increase in precipitation coincides with the phase sometimes referred to as the `Medieval Warm Period'. These regional changes in precipitation are best explained by shifts in the mean latitude of the Atlantic Intertropical Convergence Zone (ITCZ), potentially driven by Pacific-based climate variability. The variations recorded in Cariaco Basin sediments coincide with events in societal evolution that have been suggested previously to be motivated by environmental change. Regionally, the Cariaco record supports the notion that the collapse of this civilization between 800 and 1000 AD coincided with an extended period of drier conditions, implying that the rapid growth of Mayan culture from 600 to 800 AD may have resulted in a population operating at the fringes of the environment's carrying capacity. The Cariaco Basin record also hints at tropical climate events similar in timing to high latitude changes in the North Atlantic often invoked as pivotal to societal developments in Europe.

  14. Postglacial climate-change record in biomarker lipid compositions of the Hani peat sequence, Northeastern China

    Science.gov (United States)

    Zhou, Weijian; Zheng, Yanhong; Meyers, Philip A.; Jull, A. J. Timothy; Xie, Shucheng

    2010-05-01

    The peat sequence at Hani in northeastern China accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system. The molecular compositions of n-alkanes, n-alkanols, and n-alkanoic acids extracted from the Hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat-forming vegetation. Long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n-alkane distributions throughout the Hani peat sequence. The paleoclimate integrity of these biomarker molecules appears to be well preserved. Most of the n-alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants. In contrast, n-alkanoic acid distributions are dominated by secondary components that record the importance of post-depositional microbial activity in this peat sequence, which evidently can be extensive in a percolation mire. Elevated n-alkane Paq values and C 23/C 29 ratios, which are both molecular proxies for water-loving plants, record an especially moist local climate in the Bølling-Allerød (14.5 to 12.9 ka), Younger Dryas (12.9 to 11.5 ka), and Pre-Boreal (11.5 to 10.5 ka) portions of the Hani peat sequence. Depressed Paq values and C 23/C 29 ratios and larger n-alkane average chain length values indicate that the Holocene Climatic Optimum (10.5 to 6 ka) was a period of warmer climate with lower effective precipitation, which contrasts with evidence of wetter climates in most of East Asia.

  15. Sedimentary record of recent climate impacts on an insular coastal lagoon in the Gulf of California

    Science.gov (United States)

    Cuellar-Martinez, Tomasa; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan-Albert; Alonso-Rodríguez, Rosalba

    2017-03-01

    Sedimentary records are useful to evaluate environmental changes, either from natural or anthropogenic causes, such as global and climate change. The recent changes in accumulation rates and geochemical characteristics (grain size distribution, elemental composition, organic carbon and carbonate concentrations) recorded in a sediment core from San Jose Island Lagoon (SJIL, Gulf of California) were evaluated to determine its relationship with anthropogenic impacts and climatic variability. The 210Pb-derived chronology was corroborated with 239+240Pu and 137Cs stratigraphic markers. The mass accumulation rate increased up to ∼3 times during the past ∼100 years (0.16 ± 0.03 to 0.51 ± 0.06 g cm-2 yr-1). The contents of terrigenous and marine (salinity) indicator elements, as well as fine-grained sediments, also increased considerably, although no anthropization evidences were observed; indeed, the enrichment factor of trace elements indicated that the ecosystem is still a pristine environment. By using multivariate statistical techniques, we inferred that the larger input of fine-grained terrigenous sediments could be related to the enhancement of soil erosion from the catchment, under the influence of higher rainfall rates, especially during the last 20 years. In addition, the higher concentrations of salinity indicator elements most likely resulted from higher evaporation rates in the lagoon, caused by higher minimum atmospheric temperatures. We concluded that recent climate variability has become the main driver for sedimentary geochemical changes in San Jose Island Lagoon. These observations confirmed the usefulness of 210Pb-dated geochemical sediment records to study the impacts of recent climate variability where long-term environmental data is scarce or non-existent.

  16. Sea Surface Temperature Climate Data Record for the North Sea and Baltic Sea

    DEFF Research Database (Denmark)

    Høyer, Jacob L.; Karagali, Ioanna

    2016-01-01

    A 30-yr climate data record (CDR) of sea surface temperature (SST) has been produced with daily gap-free analysis fields for the North Sea and the Baltic Sea region from 1982 to 2012 by combining the Pathfinder AVHRR satellite data record with the Along-Track Scanning Radiometer (ATSR) Reprocessing...... observations on average. Validation against independent in situ observations shows a very stable performance of the data record, with a mean difference of -0.06 °C compared to moored buoys and a 0.46 °C standard deviation of the differences. The mean annual biases of the SST CDR are small for all years......, with a negligible temporal trend when compared against drifting and moored buoys. Analysis of the SST CDR reveals that the monthly anomalies for the North Sea, the Danish straits, and the central Baltic Sea regions show a high degree of correlation for interannual and decadal time scales, whereas the monthly...

  17. Wetlands as a Record of Climate Change and Hydrological Response in Arid Rift Settings

    Science.gov (United States)

    Ashley, G. M.

    2004-12-01

    Of all the terrestrial depositional settings, rift basins typically provide the greatest accommodation space, and consequently have some of the longest records of continental sedimentation. Lake deposits were the only rift component studied for records of long-term climatic change and for testing hypotheses of orbital forcing. Recently, the continuing quest for the paleontological and cultural records of human origins entombed in the sedimentary rocks of the East African Rift System raised questions concerning hydrologic and biologic response to climatic change. Additional issues are the impact of climate on paleolandscapes and the environmental stresses that might have affected human evolution. Other important indicators of rift hydrology, such as springs and wetlands are now emerging as viable records of climate change. Rift valley basins are shallow, hydrologically closed systems that are responsive to shifts in climate, and specifically sensitive to changes in the hydrologic budget (P-ET). Long term wet-dry cycles in the low latitudes are thought to be astronomically controlled, i.e. Milankovitch precession cycles (19-23 ka). In the tropics, precipitation (P) varies with changes in solar insolation which fluctuates Lake levels are known to fluctuate in response to change in hydrologic budget and wetlands appear to respond similarly. Springs and groundwater-fed wetlands are common, however the sources and sustainability of water or what geologic factors lead to the formation and longevity of wetlands is not well established. It appears that rainfall is trapped on topographic highs (rift fault blocks and volcanoes). This meteoric water infiltrates quickly through porous volcanic rocks and is stored in aquifers and released slowly. As a component of the rift hydrologic system, wetlands appear to be reliable indicators of rainfall fluctuations on both Milankovitch and sub-Milankovitch time scales. Wetland sediments are commoner in the geologic record during times

  18. Climate change research in Massachusetts, U.S.A.: searching for phenology in the historical record.

    Science.gov (United States)

    Primack, R.; Miller-Rushing, A.

    2009-04-01

    The United States does not have as many large, well-researched sets of phenological records as can be found in Europe. Such phenological research is important both scientifically to investigate the effects of climate change and, just as importantly, for convincing the public that climate change is really happening and is already affecting our environment. Scientists in the United States are currently uncovering a wealth of data from a variety of unconventional sources on the effects of climate on the phenology of a wide range of organisms, with many studies being published on birds and plants. For the past six years, we have been investigating the impact of climate change in Massachusetts, a region with a particularly strong tradition of science and natural history. We are able to use combinations of herbarium specimens, photographs, diaries of individual naturalists, records from research stations, and current observations of our own to document the effects of climate change. Each of these data sources has certain limitations, but the overall message is the same: a warming climate is causing plants to flower earlier and certain migratory birds to arrive earlier. Such data has to be interpreted carefully due to issues of changing population sizes and changing sampling methods and intensity. The single most valuable source of data for our research has been the observations of flowering times of hundreds of plant species from 1852 to 1858 in Concord, Massachusetts, made by Henry David Thoreau. Thoreau is the most famous environmental philosopher in the United States, and most students read his book Walden. Later botanists also recorded flowering times and the abundance of plant species in Concord, and we recorded flowering times and species abundances in Concord starting in 2004. The project has shown that spring flowering species are the most responsive to temperatures, and that these plant species are now flowering seven days earlier than they were in the 1850s

  19. Climate response to the Samalas volcanic eruption in 1257 revealed by proxy records

    Science.gov (United States)

    Guillet, Sébastien; Corona, Christophe; Stoffel, Markus; Khodri, Myriam; Lavigne, Franck; Ortega, Pablo; Eckert, Nicolas; Sielenou, Pascal Dkengne; Daux, Valérie; Churakova (Sidorova), Olga V.; Davi, Nicole; Edouard, Jean-Louis; Zhang, Yong; Luckman, Brian H.; Myglan, Vladimir S.; Guiot, Joël; Beniston, Martin; Masson-Delmotte, Valérie; Oppenheimer, Clive

    2017-01-01

    The eruption of Samalas in Indonesia in 1257 ranks among the largest sulfur-rich eruptions of the Common Era with sulfur deposition in ice cores reaching twice the volume of the Tambora eruption in 1815. Sedimentological analyses of deposits confirm the exceptional size of the event, which had both an eruption magnitude and a volcanic explosivity index of 7. During the Samalas eruption, more than 40 km3 of dense magma was expelled and the eruption column is estimated to have reached altitudes of 43 km. However, the climatic response to the Samalas event is debated since climate model simulations generally predict a stronger and more prolonged surface air cooling of Northern Hemisphere summers than inferred from tree-ring-based temperature reconstructions. Here, we draw on historical archives, ice-core data and tree-ring records to reconstruct the spatial and temporal climate response to the Samalas eruption. We find that 1258 and 1259 experienced some of the coldest Northern Hemisphere summers of the past millennium. However, cooling across the Northern Hemisphere was spatially heterogeneous. Western Europe, Siberia and Japan experienced strong cooling, coinciding with warmer-than-average conditions over Alaska and northern Canada. We suggest that in North America, volcanic radiative forcing was modulated by a positive phase of the El Niño-Southern Oscillation. Contemporary records attest to severe famines in England and Japan, but these began prior to the eruption. We conclude that the Samalas eruption aggravated existing crises, but did not trigger the famines.

  20. 500-year climate cycles stacking of recent centennial warming documented in an East Asian pollen record

    Science.gov (United States)

    Xu, Deke; Lu, Houyuan; Chu, Guoqiang; Wu, Naiqin; Shen, Caiming; Wang, Can; Mao, Limi

    2014-01-01

    Here we presented a high-resolution 5350-year pollen record from a maar annually laminated lake in East Asia (EA). Pollen record reflected the dynamics of vertical vegetation zones and temperature change. Spectral analysis on pollen percentages/concentrations of Pinus and Quercus, and a temperature proxy, revealed ~500-year quasi-periodic cold-warm fluctuations during the past 5350 years. This ~500-year cyclic climate change occurred in EA during the mid-late Holocene and even the last 150 years dominated by anthropogenic forcing. It was almost in phase with a ~500-year periodic change in solar activity and Greenland temperature change, suggesting that ~500-year small variations in solar output played a prominent role in the mid-late Holocene climate dynamics in EA, linked to high latitude climate system. Its last warm phase might terminate in the next several decades to enter another ~250-year cool phase, and thus this future centennial cyclic temperature minimum could partially slow down man-made global warming. PMID:24402348

  1. Plant Functional Variability in Response to Late-Quaternary Climate Change Recorded in Ancient Packrat Middens

    Science.gov (United States)

    Holmgren, C. A.; Potts, D. L.

    2006-12-01

    Responses of plant functional traits to environmental variability are of enduring interest because they constrain organism performance and ecosystem function. However, most inferences regarding plant functional trait response to climatic variability have been limited to the modern period. To better understand plant functional response to long-term climate variability and how adjustments in leaf morphology may contribute to patterns of species establishment, persistence, or extirpation, we measured specific leaf area (SLA) from macrofossils preserved in ancient packrat middens collected along the Arizona/New Mexico border, USA. Our record spanned more than 32,000 years and included six woodland and Chihuahuan Desert species: Berberis cf. haematocarpa, Juniperus cf. coahuilensis, Juniperus osteosperma, Larrea tridentata, Prosopis glandulosa and Parthenium incanum. We predicted that regional climatic warming and drying since the late Pleistocene would result in intraspecific decreases in SLA. As predicted, SLA was positively correlated with midden age for three of the six species (L. tridentata, J. osteosperma, B. cf. haematocarpa). SLA was also negatively correlated with December (L. tridentata, J. cf. coahuilensis) or June (B. cf. haematocarpa, J. osteosperma) insolation. A unique record of vegetation community dynamics, plant macrofossils preserved in packrat middens also represent a rich and largely untapped source of information on long-term trends in species functional response to environmental change.

  2. An age-calibrated record of upper Campanian – Maastrichtian climate change in the Boreal Realm

    DEFF Research Database (Denmark)

    Thibault, Nicolas Rudolph; Schovsbo, Niels; Harlou, Rikke;

    nannofossil chalk is in agreement with planktic biotic events of the latest Cretaceous and matches well with climatic trends of intermediate- and deep-waters from other oceanic basins recorded through benthic foraminiferal d18O (Barrera and Savin, 1999). However, most planktic foraminiferal d18O data do......The latest Cretaceous climate of the Boreal Realm was recorded through high-resolution bulk carbon- and oxygen-stable isotopes and a nannofossil temperature index (NTI) on the Stevns-1 core (Denmark) which recovered 456 m of upper Campanian to basal Danian chalk with ~100% recovery and an excellent...... temperatures (SSTs) in the Boreal Realm. Three warming events punctuate the overall cooling trend of the latest Cretaceous: (1) the late Campanian climatic optimum (73.9–71.6 Ma) is characterized by maximum SSTs of 20°C, (2) the mid-Maastrichtian warming (69.7–68 Ma) is characterized by stable SSTs around 17°C...

  3. Top of Atmosphere Radiation MVIRI/SEVIRI Data Record within the Climate Monitoring SAF

    Science.gov (United States)

    Urbain, Manon; Clerbaux, Nicolas; Ipe, Alessandro; Tornow, Florian; Hollmann, Rainer; Baudrez, Edward; Velazquez Blazquez, Almudena; Moreels, Johan; Trentmann, Jörg

    2017-04-01

    The CM SAF Top of Atmosphere (TOA) Radiation MVIRI/SEVIRI Data Record provides a homogeneous satellite-based climatology of the TOA Reflected Solar (TRS) and Emitted Thermal (TET) radiation in all-sky conditions. The continuous monitoring of these two components of the Earth Radiation Budget is of prime importance to study climate variability and change. The Meteosat Visible and InfraRed Imager (MVIRI - from 1983 until 2004) and the Spinning Enhanced Visible and Infrared Imager (SEVIRI - from 2004 onward) on board the Meteosat First and Second Generation satellites are combined to generate a long Thematic Climate Data Record (TCDR). Combining MVIRI and SEVIRI allows an unprecedented temporal (30 minutes / 15 minutes) and spatial (2.5 km / 3 km) resolution compared to the Clouds and the Earth's Radiant Energy System (CERES) products. This is a step forward as it helps to increase the knowledge of the diurnal cycle and the small-scale spatial variations of radiation. The MVIRI/SEVIRI Data Record covers a 32 years time period from 1 February 1983 to 30 April 2015. The TOA radiation products are provided as daily mean, monthly mean and monthly averages of the hourly integrated values (diurnal cycle). To ensure consistency with other CM SAF products, the data is provided on a regular grid at a spatial resolution of 0.05 degrees (i.e. about 5.5 km) and covers the region between +/- 70° longitude and +/- 70° latitude. Validation of the MVIRI/SEVIRI Data Record has been performed by intercomparison with several references such as the CERES products (EBAF, SYN1deg-Day and SYN1deg-M3Hour), the HIRS OLR Climate Data Record (Daily and Monthly), the reconstructed ERBS WFOV-CERES (or DEEP-C) dataset and the ISCCP FD products. CERES is considered as the best reference from March 2000 onward. The quality of the early part of the Data Record is verified against the other references. In general, the stability of all the TOA radiation products is estimated to be better than 4 W.m-2

  4. Coralline alga reveals first marine record of subarctic North Pacific climate change

    Science.gov (United States)

    Halfar, J.; Steneck, R.; Schone, B.; Moore, G.W.K.; Joachimski, M.; Kronz, A.; Fietzke, J.; Estes, James

    2007-01-01

    While recent changes in subarctic North Pacific climate had dramatic effects on ecosystems and fishery yields, past climate dynamics and teleconnection patterns are poorly understood due to the absence of century-long high-resolution marine records. We present the first 117-year long annually resolved marine climate history from the western Bering Sea/Aleutian Island region using information contained in the calcitic skeleton of the long-lived crustose coralline red alga Clathromorphum nereostratum, a previously unused climate archive. The skeletal ??18O-time series indicates significant warming and/or freshening of surface waters after the middle of the 20th century. Furthermore, the time series is spatiotemporally correlated with Pacific Decadal Oscillation (PDO) and tropical El Nio??-Southern Oscillation (ENSO) indices. Even though the western Bering Sea/Aleutian Island region is believed to be outside the area of significant marine response to ENSO, we propose that an ENSO signal is transmitted via the Alaskan Stream from the Eastern North Pacific, a region of known ENSO teleconnections. Copyright 2007 by the American Geophysical Union.

  5. Stable Isotopic Variations in Columnar Cacti: are Responses to Climate Recorded in Spines?

    Science.gov (United States)

    English, N. B.; Dettman, D. L.; Williams, D. G.

    2004-12-01

    The behavior of the North American monsoon (NAM), particularly with respect to times of continental drought and its relationship to the Pacific-North American (PNA) teleconnection pattern and the El Nino/Southern Oscillation (ENSO) is of great interest to paleoclimatologists and water managers. Long-term instrumental precipitation and tree ring records in the southwestern United States and northwestern Mexico at low elevations are sparse and this has hindered research on NAM variability at interannual timescales. Saguaro cacti (Carnegiea gigantea) and other columnar cacti in North and South America are long-lived and have the potential to record climate variability on land with high temporal and spatial resolution. The vertical sequence of spines on the saguaro's exterior represents a high resolution (4 to 6 per year), and long (over 150 years) record of environmental change. We present results from an experiment where we tracked the oxygen isotopic values in the source waters, stem tissue waters and spine tissue for three treatments over the course of three months. These data are then compared to a previously developed mechanistic model of isotopic variation that reflects the physiological responses of Saguaro to climate variation over seasonal to century long time-scales. We also present the rationale for a new method to determine the growth rate of columnar cacti using the radiocarbon bomb spike. Our measurements reveal that oxygen and hydrogen isotopic variation among the sequentially produced and persistent spines covering the saguaro body record fluctuations in saguaro water balance. The model successfully predicts isotopic variation in spines and constrains controlling variables, yielding a powerful and high-resolution stable isotope index of water stress in the low desert. The development and refinement of an isotopic model for saguaro will serve as the basis for models applied to other species of columnar cacti in North and South America. The role of the

  6. Floodplain ecohydrology: Discerning climatic v. anthropogenic controls from tree-ring δ18O, dendrochronology, and instrumental climate records

    Science.gov (United States)

    Singer, M. B.; Piégay, H.; Stella, J. C.; Wilson, R.

    2012-12-01

    Vegetation of lowland riparian zones in temperate climates is largely determined by floodplain water availability during the growth season. Floodplain water reservoirs are replenished seasonally by lateral hyporheic water from streamflow, which primarily contributes to phreatic zone water and by infiltration of precipitation, which typically controls seasonal vadose zone soil moisture. Water availability to species rooted to particular depths in the floodplain is subject to interannual variability in climate (e.g., precipitation magnitude, timing, and phase). Co-occurring tree species in the riparian zone may express differential adaptation to water availability and shifting water sources, especially if they are rooted at contrasting depths. We have developed an ecohydrologic approach to assess how climatic variability impacts water availability at different depths in the floodplain and corresponding tree growth in the Rhône River basin, France. We combine dendrochronology, tree ring isotopes (δ18O), and instrumental climate records to discern relationships between tree growth and water sources for two contrasting, co-occurring riparian species—the shallowly rooting Fraxinus excelsior and the obligate phreatophyte, Populus nigra (poplar). We developed growth time series via basal area increment (BAI) and extracted alpha-cellulose from tree rings to assess relative responses to water stress via δ18O contained in each annual ring, and we analyzed these data alongside streamflow, precipitation, and groundwater data. Our initial work on a tributary of the Rhône showed that F. excelsior generally indicates water availability in the vadose zone, while P. nigra provides a window into the phreatic zone. However, the rooting depths and water sources for these species overlap on particularly low topographic surfaces, where phreatic water is abundant for both. In contrast to prior assumptions, we found that P. nigra exhibits more growth sensitivity to drought stress

  7. Climate variation since the Last Interglaciation recorded in the Guliya ice core

    Institute of Scientific and Technical Information of China (English)

    姚檀栋; L.G.Thompson; 施雅风; 秦大河; 焦克勤; 杨志红; 田立德; E.M.Thompson

    1997-01-01

    The climatic and environmental variations since the Last Interglaciation are reconstructed based on the study of the upper 268 m of the 309-m-long Guliya ice core. Five stages can be distinguished since the Last Interglaciation from the δ18O record in the Guliya ice core: Stage 1 (Deglaciation), Stage 2 (the Last Glacial Maximum), Stage 3 (interstadial), Stage 4 (interstadial in the early glacial maximum) and Stage 5 (the Last Interglaciation). Stage 5 can be divided further into 5 substages; a, b, c, d, e. The δ18O record in the Guliya ice core indicates clearly the close correlation between the temperature variation on the Tibetan Plateau and the solar activities. The study indicates that the solar activity is a main forcing to the climatic variation on the Tibetan Plateau. Through a comparison of the ice core record in Guliya with that in the Greenland and the Antarctic, it can be found that the variation of large temperature variation events in different parts of the world is generally the same, b

  8. Synchrotron X-ray microscopy of marine calcifiers: how plankton record past climate change

    Science.gov (United States)

    Redfern, S. A. T.; Branson, O.; Read, E.

    2017-06-01

    We have used STXM and PEEM to reveal the underpinning chemistry and nanoscale structure behind palaeo-climate geochemical signatures, such as trace Mg in shells- proposed proxies for palaeo-ocean temperature. This has allowed us to test the chemical assumptions and mechanisms underpinning the use of such empirical proxies. We have determined the control on driving chemical variations in biogenic carbonates using STXM at the absorption edge of Mg, B, and Na in the shells of modern plankton. The power of these observations lies in their ability to link changes in chemistry, microstructure, and growth process in biogenic carbonate to environmental influences. We have seen that such changes occur at length scales of tens of nanometres and demonstrated that STXM provides an invaluable route to understanding chemical environment and key heterogeneity at the appropriate length scale. This new understanding provides new routes for future measurements of past climate variation in the sea floor fossil record.

  9. Direct North-South synchronization of abrupt climate change record in ice cores using beryllium 10

    Directory of Open Access Journals (Sweden)

    G. M. Raisbeck

    2007-05-01

    Full Text Available A new, decadally resolved record of the 10Be peak at 41 kyr from the EPICA Dome C ice core (Antarctica is used to match it with the same peak in the GRIP ice core (Greenland. This permits a direct synchronisation of the climatic variations around 41 kyr BP, independent of uncertainties related to the ice age-gas age difference in ice cores. Dansgaard-Oeschger event 10 is in the period of best synchronisation and is found to be coeval with an Antarctic temperature maximum. Simulations using a thermal bipolar seesaw model agree reasonably well with the observed relative climate chronology in these two cores. They also reproduce three Antarctic warming events between A1 and A2.

  10. Direct north-south synchronization of abrupt climate change record in ice cores using Beryllium 10

    Directory of Open Access Journals (Sweden)

    G. M. Raisbeck

    2007-09-01

    Full Text Available A new, decadally resolved record of the 10Be peak at 41 kyr from the EPICA Dome C ice core (Antarctica is used to match it with the same peak in the GRIP ice core (Greenland. This permits a direct synchronisation of the climatic variations around this time period, independent of uncertainties related to the ice age-gas age difference in ice cores. Dansgaard-Oeschger event 10 is in the period of best synchronisation and is found to be coeval with an Antarctic temperature maximum. Simulations using a thermal bipolar seesaw model agree reasonably well with the observed relative climate chronology in these two cores. They also reproduce three Antarctic warming events observed between A1 and A2.

  11. NOAA Climate Data Record (CDR) of Advanced Microwave Sounding Unit (AMSU)-A Brightness Temperature, Version 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Climate Data Record (CDR) for Advanced Microwave Sounding Unit-A (AMSU-A) brightness temperature in "window channels". The data cover a time period from...

  12. NOAA Climate Data Record (CDR) of Cloud Properties from AVHRR Pathfinder Atmospheres - Extended (PATMOS-x), Version 5.3

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) of cloud products was produced by the University of Wisconsin using the AVHRR Pathfinder Atmospheres - Extended (PATMOS-X)...

  13. NOAA Climate Data Record (CDR) of SSM/I and SSMIS Microwave Brightness Temperatures, CSU Version 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) from Colorado State University (CSU) contains brightness temperatures that have been improved and quality-controlled over the...

  14. NOAA Climate Data Record (CDR) of Zonal Mean Ozone Binary Database of Profiles (BDBP), version 1.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) of Zonal Mean Ozone Binary Database of Profiles (BDBP) dataset is a vertically resolved, global, gap-free and zonal mean dataset...

  15. NOAA Climate Data Record (CDR) of MSU and AMSU-A Mean Layer Temperatures, UAH Version 5.4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This Climate Data Record (CDR) includes lower tropospheric, mid-tropospheric, and lower stratospheric temperatures over land and ocean derived from microwave...

  16. NOAA Climate Data Record (CDR) of SSM/I and SSMIS Microwave Brightness Temperatures, RSS Version 7

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This Version 7 NOAA Fundamental Climate Data Record (CDR) from Remote Sensing Systems (RSS) contains brightness temperatures that have been inter-calibrated and...

  17. NOAA Climate Data Record (CDR) of Intersatellite Calibrated Clear-Sky HIRS Channel 12 Brightness Temperature, Version 2.6

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) of Inter-Satellite Calibrated Clear-Sky High Resolution Infrared Radiation Sounder (HIRS) Channel 12 brightness temperatures...

  18. Gridded sunshine duration climate data record for Germany based on combined satellite and in situ observations

    Science.gov (United States)

    Walawender, Jakub; Kothe, Steffen; Trentmann, Jörg; Pfeifroth, Uwe; Cremer, Roswitha

    2017-04-01

    The purpose of this study is to create a 1 km2 gridded daily sunshine duration data record for Germany covering the period from 1983 to 2015 (33 years) based on satellite estimates of direct normalised surface solar radiation and in situ sunshine duration observations using a geostatistical approach. The CM SAF SARAH direct normalized irradiance (DNI) satellite climate data record and in situ observations of sunshine duration from 121 weather stations operated by DWD are used as input datasets. The selected period of 33 years is associated with the availability of satellite data. The number of ground stations is limited to 121 as there are only time series with less than 10% of missing observations over the selected period included to keep the long-term consistency of the output sunshine duration data record. In the first step, DNI data record is used to derive sunshine hours by applying WMO threshold of 120 W/m2 (SDU = DNI ≥ 120 W/m2) and weighting of sunny slots to correct the sunshine length between two instantaneous image data due to cloud movement. In the second step, linear regression between SDU and in situ sunshine duration is calculated to adjust the satellite product to the ground observations and the output regression coefficients are applied to create a regression grid. In the last step regression residuals are interpolated with ordinary kriging and added to the regression grid. A comprehensive accuracy assessment of the gridded sunshine duration data record is performed by calculating prediction errors (cross-validation routine). "R" is used for data processing. A short analysis of the spatial distribution and temporal variability of sunshine duration over Germany based on the created dataset will be presented. The gridded sunshine duration data are useful for applications in various climate-related studies, agriculture and solar energy potential calculations.

  19. Maturity Matrices for Quality of Model- and Observation-Based Climate Data Records

    Science.gov (United States)

    Höck, Heinke; Kaiser-Weiss, Andrea; Kaspar, Frank; Stockhause, Martina; Toussaint, Frank; Lautenschlager, Michael

    2015-04-01

    In the field of Software Engineering the Capability Maturity Model is used to evaluate and improve software development processes. The application of a Maturity Matrix is a method to assess the degree of software maturity. This method was adapted to the maturity of Earth System data in scientific archives. The application of such an approach to Climate Data Records was first proposed in the context of satellite-based climate products and applied by NOAA and NASA. The European FP7 project CORE-CLIMAX suggested and tested extensions of the approach in order to allow the applicability to additional climate datasets, e.g. based on in-situ observations as well as model-based reanalysis. Within that project the concept was applied to products of satellite- and in-situ based datasets. Examples are national ground-based data from Germany as an example for typical products of a national meteorological service, the EUMETSAT Satellite Application Facility Network, the ESA Climate Change Initiative, European Reanalysis activities (ERA-CLIM) and international in situ-based climatologies such as GPCC, ECA&D, BSRN, HadSST. Climate models and their related output have some additional characteristics that need specific consideration in such an approach. Here we use examples from the World Data Centre for Climate (WDCC) to discuss the applicability. The WDCC focuses on climate data products, specifically those resulting from climate simulations. Based on these already existing Maturity Matrix models, WDCC developed a generic Quality Assessment System for Earth System data. A self-assessment is performed using a maturity matrix evaluating the data quality for five maturity levels with respect to the criteria data and metadata consistency, completeness, accessibility and accuracy. The classical goals of a quality assessment system in a data processing workflow are: (1) to encourage data creators to improve quality to reach the next quality level, (2) enable data consumers to decide

  20. Quantification of structural uncertainty in climate data records from GPS radio occultation

    Directory of Open Access Journals (Sweden)

    A. K. Steiner

    2013-02-01

    Full Text Available Global Positioning System (GPS radio occultation (RO has provided continuous observations of the Earth's atmosphere since 2001 with global coverage, all-weather capability, and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS. Precise time measurements enable long-term stability but careful processing is needed. Here we provide climate-oriented atmospheric scientists with multicenter-based results on the long-term stability of RO climatological fields for trend studies. We quantify the structural uncertainty of atmospheric trends estimated from the RO record, which arises from current processing schemes of six international RO processing centers, DMI Copenhagen, EUM Darmstadt, GFZ Potsdam, JPL Pasadena, UCAR Boulder, and WEGC Graz. Monthly-mean zonal-mean fields of bending angle, refractivity, dry pressure, dry geopotential height, and dry temperature from the CHAMP mission are compared for September 2001 to September 2008. We find that structural uncertainty is lowest in the tropics and mid-latitudes (50° S to 50° N from 8 km to 25 km for all inspected RO variables. In this region, the structural uncertainty in trends over 7 yr is <0.03% for bending angle, refractivity, and pressure, <3 m for geopotential height of pressure levels, and <0.06 K for temperature; low enough for detecting a climate change signal within about a decade. Larger structural uncertainty above about 25 km and at high latitudes is attributable to differences in the processing schemes, which undergo continuous improvements. Though current use of RO for reliable climate trend assessment is bound to 50° S to 50° N, our results show that quality, consistency, and reproducibility are favorable in the UTLS for the establishment of a climate benchmark record.

  1. Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

    Science.gov (United States)

    Zhang, Wenxiang; Ming, Qingzhong; Shi, Zhengtao; Chen, Guangjie; Niu, Jie; Lei, Guoliang; Chang, Fengqin; Zhang, Hucai

    2014-01-01

    Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

  2. Quantification of structural uncertainty in climate data records from GPS radio occultation

    Directory of Open Access Journals (Sweden)

    A. K. Steiner

    2012-10-01

    Full Text Available Global Positioning System (GPS radio occultation (RO provides continuous observations of the Earth's atmosphere since 2001 with global coverage, all-weather capability, and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS. Precise time measurements enable long-term stability but careful processing is needed. Here we provide climate-oriented atmospheric scientists with multicenter-based results on the long-term stability of RO climatological fields for trend studies. We quantify the structural uncertainty of atmospheric trends estimated from the RO record, which arises from current processing schemes of six international RO processing centers, DMI Copenhagen, EUM Darmstadt, GFZ Potsdam, JPL Pasadena, UCAR Boulder, and WEGC Graz. Monthly-mean zonal-mean fields of bending angle, refractivity, dry pressure, dry geopotential height, and dry temperature from the CHAMP mission are compared for September 2001 to September 2008. We find that structural uncertainty is lowest in the tropics and mid-latitudes (50° S to 50° N from 8 km to 25 km for all inspected RO variables. In this region, the structural uncertainty in trends over 7 yr is <0.03% f or bending angle, refractivity, and pressure, <3 m for geopotential height of pressure levels, and <0.06 K for temperature; low enough for detecting a climate change signal within about a decade. Larger structural uncertainty above about 25 km and at high latitudes is attributable to differences in the processing schemes, which undergo continuous improvements. Though current use of RO for reliable climate trend assessment is bound to 50° S to 50° N, our results show that quality, consistency, and reproducibility are favorable in the UTLS for the establishment of a climate benchmark record.

  3. Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

    Directory of Open Access Journals (Sweden)

    Wenxiang Zhang

    Full Text Available Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC, total nitrogen (TN, δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS and CaCO3 content, as well as accelerator mass spectrometry (AMS 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

  4. Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records

    NARCIS (Netherlands)

    S.G.A. Flantua; H. Hooghiemstra; M. Vuille; H. Behling; J.F. Carson; W.D. Gosling; I. Hoyos; M.P. Ledru; E. Montoya; F. Mayle; A. Maldonado; V. Rull; M.S. Tonello; B.S. Whitney; C. González-Arango

    2016-01-01

    An improved understanding of present-day climate variability and change relies on high-quality data sets from the past 2 millennia. Global efforts to model regional climate modes are in the process of being validated against, and integrated with, records of past vegetation change. For South America,

  5. Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa

    NARCIS (Netherlands)

    Berke, M.A.; Johnson, T.C.; Werne, J.P.; Grice, K.; Schouten, S.; Sinninghe Damsté, J.S.

    2012-01-01

    New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a similar to 14,000 year record of climate variability from Lake Victoria, East Africa, the world's second largest

  6. Recording of climate and diagenesis through fossil pigments and sedimentary DNA at Laguna Potrok Aike, Argentina

    Science.gov (United States)

    Vuillemin, A.; Ariztegui, D.; Leavitt, P. R.; Bunting, L.; Pasado Science Team

    2015-11-01

    Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. Although marine sedimentary microbial assemblages are often defined by their surrounding geochemical conditions, the influence of environmental features upon microbial development and post-depositional survival remains largely unknown in the lacustrine realm. Due to long-term microbial activity, the composition of environmental DNA can be expected to evolve with sediment depth and over time and therefore should reflect both ancient and extant microbial populations, but this hypothesis has rarely been tested using a multiproxy approach. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two well defined climatic intervals whose sediments harboured active microbial populations and measurable ATP were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. Bacterial and archaeal 16S rRNA gene sequences recovered from the Holocene record revealed a microbial community adapted to subsaline conditions actively producing methane during organic matter degradation. These characteristics were associated with sediments resulting from endorheic lake conditions with high evaporative stress and concomitant high algal productivity. Moreover, archaeal clone libraries established throughout the Holocene record indicate an age-related stratification of these populations, consistent with a gradual use of organic substrates after deposition. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. These patterns

  7. Combining the AIRS, CrIS and IASI Radiance Records for Climate Level Retrievals

    Science.gov (United States)

    Strow, L. L.

    2016-12-01

    The AIRS record is now 14+ years long, and with the addition of CrIS should provide a 30+ year long hyperspectral radiance record that can be supplemented with another two times in the diurnal cycle with IASI starting in 2007. The stability of these sensors can be established by comparisons to CO2 variability and to tropical sea surface temperature trends. At present the observed stabilities are much better than climate requirements of 0.01/year. SNO observations indicate radiometric agreement among these sensors of 0.1 - 0.3K before any empirical adjustments. A 1-year set of SNO overlaps have statistical uncertainties of less than 0.01K between these three sensors. Moreover, we show that IASI can be used as a transfer standard between AIRS and CrIS (or between CrIS-1 and CrIS-2) should there be a gap in overlap of sensors in the PM orbit. We have done these SNO comparisons by converting AIRS and IASI spectral to the CrIS instrument lineshape (ILS). Achieving climate quality retrievals, trends, and anomalies of temperature and humidity is non-trivial and requires error characterization (not validation) that to date has not been done with single-footprint hyperspectral sensor retrievals. We suggest that the infrared hyperspectral community utilize a common ILS radiance product as a first-step in achieving climate-quality retrievals in order to remove uncertainties in differential instrument sensitivies and in different forward radiative transfer models. We propose a very different approach for Level 3 (climate) products where anomalies and trends (one of the main products of interest to the climate community) are derived directly from Level 3 radiance products, giving far superior error traceability and retrieval regularization in the vertical. Tempertature and humidity trends and anomalies for 14-years of AIRS will be presented and compared to those provided by ERA-Interim, AIRS Level3 data, and microwave sensors. A significant advantage of this approach, which

  8. Abrupt climate changes of the last deglaciation detected in a Western Mediterranean forest record

    Directory of Open Access Journals (Sweden)

    W. J. Fletcher

    2010-04-01

    Full Text Available Abrupt changes in Western Mediterranean climate during the last deglaciation (20 to 6 cal ka BP are detected in marine core MD95-2043 (Alboran Sea through the investigation of high-resolution pollen data and pollen-based climate reconstructions by the modern analogue technique (MAT for annual precipitation (Pann and mean temperatures of the coldest and warmest months (MTCO and MTWA. Changes in temperate Mediterranean forest development and composition and MAT reconstructions indicate major climatic shifts with parallel temperature and precipitation changes at the onsets of Heinrich stadial 1 (equivalent to the Oldest Dryas, the Bölling-Allerød (BA, and the Younger Dryas (YD. Multi-centennial-scale oscillations in forest development occurred throughout the BA, YD, and early Holocene. Shifts in vegetation composition and (Pann reconstructions indicate that forest declines occurred during dry, and generally cool, episodes centred at 14.0, 13.3, 12.9, 11.8, 10.7, 10.1, 9.2, 8.3 and 7.4 cal ka BP. The forest record also suggests multiple, low-amplitude Preboreal (PB climate oscillations, and a marked increase in moisture availability for forest development at the end of the PB at 10.6 cal ka BP. Dry atmospheric conditions in the Western Mediterranean occurred in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas, GI-1b (Intra-Allerød Cold Period and GS-1 (YD, and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to Western-central Europe relates to the dynamics of the westerlies and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alboran

  9. A Southern Ocean terrestrial record of global climate change for the past 130 ka

    Science.gov (United States)

    Vandergoes, M.; Newnham, R.; Hendy, C.; Lowell, T.; Preusser, F.; Almond, P.; Fitzsimons, S.

    2003-04-01

    The coastal plain of South Westland, New Zealand, is characterised by a complex pattern of Late Quaternary moraines and outwash surfaces formed form the advance and retreat of successive piedmont glaciers originating from the adjacent Southern Alps ice centre. Associated with the glacial landforms are numerous bogs and lakes, whose accumulated sedimentary sequences serve as rich natural archives for subsequent climate change. At one such site, Okarito Pakihi, 15 cores have been taken to depths of up to 10 m, without reaching bottom. The generalised stratigraphy from the top consists of a 2-4 m peat layer extending back to 12.0 14C ka, overlying 2-3 m of massive blue-grey silt, often with a zone of greater organic content in its midst. Towards the top of this unit is a layer of glass shards from the Kawakawa Tephra (22.5 14C ka), whilst optically stimulated luminescence (OSL) dating indicates the age of this unit ranges from 28 ka near the top to 75 ka near the base. At its base, the blue-grey silt changes abruptly to a 3-4 m thick brown organic-rich silt which in turn changes abruptly to massive blue-grey silt grading into a finely laminated silt. Preliminary OSL results suggest an age of >130 ka for the laminated silts. This chronostratigraphy thus indicates a continuous sedimentary record extending from near present back to at least the penultimate glaciation, whilst the palynology of this record shows a sequence of vegetation and climate change that corresponds broadly to the marine isotope (MI) record for this interval. The upper organic unit (Holocene) is dominated by lowland temperate (podocarp) rainforest pollen which is near absent in the underlying blue-grey silts, deposited during MI Stages 2-4, when long periods of sub-alpine shrubland were punctuated by short intervals of grassland expansion. There appears to be good correspondence between these palynologically determined grassland intervals and other records of glacier movement during the last

  10. Climatic conditions for the last Neanderthals: Herpetofaunal record of Gorham’s Cave, Gibraltar.

    Science.gov (United States)

    Blain, Hugues-Alexandre; Gleed-Owen, Chris P; López-García, Juan Manuel; Carrión, José Sebastian; Jennings, Richard; Finlayson, Geraldine; Finlayson, Clive; Giles-Pacheco, Francisco

    2013-04-01

    Gorham’s Cave is located in the British territory of Gibraltar in the southernmost end of the Iberian Peninsula. Recent excavations, which began in 1997, have exposed an 18 m archaeological sequence that covered the last evidence of Neanderthal occupation and the first evidence of modern human occupation in the cave. By applying the Mutual Climatic Range method on the amphibian and reptile assemblages, we propose here new quantitative data on the terrestrial climatic conditions throughout the latest Pleistocene sequence of Gorham’s Cave. In comparison with current climatic data, all mean annual temperatures were about 1.6-1.8 degrees C lower in this region. Winters were colder and summers were similar to today. Mean annual precipitation was slightly lower, but according to the Aridity Index of Gaussen there were only four dry months during the latest Pleistocene as opposed to five dry months today during the summer. The climate was Mediterranean and semi-arid (according to the Aridity Index of Dantin-Revenga) or semi-humid (according to the Aridity Index of Martonne). The atmospheric temperature range was higher during the latest Pleistocene, mainly due to lower winter temperatures. Such data support recent bioclimatic models, which indicate that high rainfall levels may have been a significant factor in the late survival of Neanderthal populations in southern Iberia. The Solutrean levels of Gorham’s Cave and climate records from cores in the Alboran Sea indicate increasing aridity from Marine Isotope Stage (MIS) 3-2. Because Neanderthals seem to have been associated with woodland habitats, we propose that lessening rainfall may have caused the degradation of large areas of forest and may have made late surviving Neanderthal populations more vulnerable outside southern refuges like the Rock of Gibraltar.

  11. Late Holocene interdecadal climate variability in the Sahel: inferences from a marine dust record offshore Senegal

    Science.gov (United States)

    Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.

    2009-04-01

    Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid Sahel belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of Sahel climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4

  12. Prediction of Arctic plant phenological sensitivity to climate change from historical records.

    Science.gov (United States)

    Panchen, Zoe A; Gorelick, Root

    2017-03-01

    The pace of climate change in the Arctic is dramatic, with temperatures rising at a rate double the global average. The timing of flowering and fruiting (phenology) is often temperature dependent and tends to advance as the climate warms. Herbarium specimens, photographs, and field observations can provide historical phenology records and have been used, on a localised scale, to predict species' phenological sensitivity to climate change. Conducting similar localised studies in the Canadian Arctic, however, poses a challenge where the collection of herbarium specimens, photographs, and field observations have been temporally and spatially sporadic. We used flowering and seed dispersal times of 23 Arctic species from herbarium specimens, photographs, and field observations collected from across the 2.1 million km(2) area of Nunavut, Canada, to determine (1) which monthly temperatures influence flowering and seed dispersal times; (2) species' phenological sensitivity to temperature; and (3) whether flowering or seed dispersal times have advanced over the past 120 years. We tested this at different spatial scales and compared the sensitivity in different regions of Nunavut. Broadly speaking, this research serves as a proof of concept to assess whether phenology-climate change studies using historic data can be conducted at large spatial scales. Flowering times and seed dispersal time were most strongly correlated with June and July temperatures, respectively. Seed dispersal times have advanced at double the rate of flowering times over the past 120 years, reflecting greater late-summer temperature rises in Nunavut. There is great diversity in the flowering time sensitivity to temperature of Arctic plant species, suggesting climate change implications for Arctic ecological communities, including altered community composition, competition, and pollinator interactions. Intraspecific temperature sensitivity and warming trends varied markedly across Nunavut and could

  13. Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

    Science.gov (United States)

    van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

    2016-04-01

    The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. Glaciers rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of glacier activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent glacier activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold

  14. A 30+ Year AVHRR LAI and FAPAR Climate Data Record: Algorithm Description and Validation

    Directory of Open Access Journals (Sweden)

    Martin Claverie

    2016-03-01

    Full Text Available In- land surface models, which are used to evaluate the role of vegetation in the context of global climate change and variability, LAI and FAPAR play a key role, specifically with respect to the carbon and water cycles. The AVHRR-based LAI/FAPAR dataset offers daily temporal resolution, an improvement over previous products. This climate data record is based on a carefully calibrated and corrected land surface reflectance dataset to provide a high-quality, consistent time-series suitable for climate studies. It spans from mid-1981 to the present. Further, this operational dataset is available in near real-time allowing use for monitoring purposes. The algorithm relies on artificial neural networks calibrated using the MODIS LAI/FAPAR dataset. Evaluation based on cross-comparison with MODIS products and in situ data show the dataset is consistent and reliable with overall uncertainties of 1.03 and 0.15 for LAI and FAPAR, respectively. However, a clear saturation effect is observed in the broadleaf forest biomes with high LAI (>4.5 and FAPAR (>0.8 values.

  15. Carbonaceous aerosol tracers in ice-cores record multi-decadal climate oscillations.

    Science.gov (United States)

    Seki, Osamu; Kawamura, Kimitaka; Bendle, James A P; Izawa, Yusuke; Suzuki, Ikuko; Shiraiwa, Takayuki; Fujii, Yoshiyuki

    2015-09-28

    Carbonaceous aerosols influence the climate via direct and indirect effects on radiative balance. However, the factors controlling the emissions, transport and role of carbonaceous aerosols in the climate system are highly uncertain. Here we investigate organic tracers in ice cores from Greenland and Kamchatka and find that, throughout the period covered by the records (1550 to 2000 CE), the concentrations and composition of biomass burning-, soil bacterial- and plant wax- tracers correspond to Arctic and regional temperatures as well as the warm season Arctic Oscillation (AO) over multi-decadal time-scales. Specifically, order of magnitude decreases (increases) in abundances of ice-core organic tracers, likely representing significant decreases (increases) in the atmospheric loading of carbonaceous aerosols, occur during colder (warmer) phases in the high latitudinal Northern Hemisphere. This raises questions about causality and possible carbonaceous aerosol feedback mechanisms. Our work opens new avenues for ice core research. Translating concentrations of organic tracers (μg/kg-ice or TOC) from ice-cores, into estimates of the atmospheric loading of carbonaceous aerosols (μg/m(3)) combined with new model constraints on the strength and sign of climate forcing by carbonaceous aerosols should be a priority for future research.

  16. Climatic changes on orbital and sub-orbital time scale recorded by the Guliya ice core in Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    姚檀栋; 徐柏青; 蒲健辰

    2001-01-01

    Based on ice core records in the Tibetan Plateau and Greenland, the features and possible causes of climatic changes on orbital and sub-orbital time scale were discussed. Orbital time scale climatic change recorded in ice core from the Tibetan Plateau is typically ahead of that from polar regions, which indicates that climatic change in the Tibetan Plateau might be earlier than polar regions. The solar radiation change is a major factor that dominates the climatic change on orbital time scale. However, climatic events on sub-orbital time scale occurred later in the Tibetan Plateau than in the Arctic Region, indicating a different mechanism. For example, the Younger Dryas and Heinrich events took place earlier in Greenland ice core record than in Guliya ice core record. It is reasonable to propose the hypothesis that these climatic events were affected possibly by the Laurentide Ice Sheet. Therefore, ice sheet is critically important to climatic change on sub-orbital time scale in some ice ages.

  17. Climatic Signals Recorded in Shells in Xingcuo Lake,Eastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This paper presents the results of determining trace elements and δ13 C, δ18 O in Gy-raulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. Bycoupling these indexes and instrumental meteorological data on its basin to determine the relationsamong them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments.The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that traceelements, and stable isotope in shells just recorded the climatic signals of the warm seasons insteadof that of the whole year; that Mg/Ca ratio and δ18O proxy had certain correlation with air tempera-ture in warm seasons, when the δ18 O proxy was more sensitive; with the average ratio of them being0.28 × 10-3/℃ and the variation rate dδ18 O/dT being 1.64 × 10-3/℃; that the Sr/Ca ratio andδ13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.

  18. Potential of treeline bristlecone pine as a late Holocene climate record

    Science.gov (United States)

    Salzer, M. W.; Hughes, M. K.; Bunn, A. G.; Kipfmueller, K. F.

    2010-12-01

    Due to their length, annual resolution, and sensitivity to climate, bristlecone pine tree-ring records are highly valuable paleoclimate archives. In previous work we have shown that ring widths from three upper-treeline sites in the Great Basin, USA showed ring growth in the second half of the 20th century that was greater than any in the last three and a half millennia and that is well correlated to temperature (Salzer et al. 2009). The changing pattern of growth characteristics with elevation does not support a dominant role for carbon dioxide mediated increased water-use efficiency at these tree-line sites. We have expanded our analyses to create long multimillennial time series of both raw ring-width and standardized ring-width index. These annually-resolved time series extend nearly 5000 years into the past. Our approach allows for both the creation of estimates of uncertainty to assess the reliability of the chronologies through time, and for the retention of decadal- through multicentury-scale variability that is unavailable in most tree-ring records. We discuss these results in the context of western US climate during the second half of the Holocene with particular emphasis on the last 2000 years. Reference: Salzer, M.W., Hughes, M.K., Bunn, A. and Kipfmueller, K. F. Recent unprecedented tree-ring growth in bristlecone pine at the highest elevations and possible causes. Proceedings of the National Academy of Science. doi: 10.1073/pnas.0903029106 (2009).

  19. Little Ice Age Glaciation in Alaska: A record of recent global climatic change

    Energy Technology Data Exchange (ETDEWEB)

    Calkin, P.E.; Wiles, G.C.

    1992-03-01

    General global cooling and temperature fluctuation accompanied by expansion of mountain glaciers characterized the Little Ice Age of about A.D. 1200 through A.D. 1900. The effects of such temperature changes appear first and are strongest at high latitudes. Therefore the Little Ice Age record of glacial fluctuation in Alaska may provide a good proxy for these events and a test for models of future climatic change. Holocene expansions began here as early as 7000 B.P. and locally show a periodicity of 350 years after about 4500 years B.P. The Little Ice Age followed a late Holocene interval of minor ice advance and a subsequent period of ice margin recession lasting one to seven centuries. The timing of expansions since about A.D. 1200 have often varied between glaciers, but these are the most pervasive glacial events of the Holocene in Alaska and frequently represent ice marginal maxima for this interval. At least two major expansions are, apparent in forefields of both land-terminating and fjord-calving glaciers, but the former display the most reliable and detailed climatic record. Major maxima occurred by the 16th century and into the mid-18th century. Culmination of advances occurred throughout Alaska during the 19th century followed within a few decades by general glacial retreat. Concurrently, equilibrium line altitudes have been raised 100-400 m, representing a rise of 2-3 deg C in mean summer temperature.

  20. Multi-proxy records of Eocene vegetation and climatic dynamics from North America

    Science.gov (United States)

    Sheldon, N. D.; Smith, S. Y.; Stromberg, C. A.; Hyland, E.; Miller, L. A.

    2010-12-01

    The Eocene is characterized by a “thermal maximum” in the early part, and a shift to “icehouse” conditions by the end of the epoch. Consequently, this is an interesting time to look at vegetation dynamics and understanding plant responses to environmental change, especially as refinement of global climate models is needed if we are to understand future climate change impacts. Paleobotanical evidence, such as phytoliths (plant silica bodies), and paleoenvironmental indicators, such as paleosols, offer an opportunity to study vegetation composition and dynamics in the absence of macrofossils on a variety of spatial and temporal scales. To examine the interaction between paleoclimatic/paleoenvironmental changes and paleovegetation changes, we will compare and contrast two well-dated, high-resolution, multi-proxy records from North America. The margins of the Green River Basin system during the Early Eocene Climatic Optimum (53-50 Ma) are an extremely important location for understanding ecological composition and potential climatic drivers of North American floral diversification, because this area is widely considered the point of origin for many modern grass clades. We examined paleosols preserved in the fluvial, basin-margin Wasatch Formation preserved near South Pass, Wyoming. Field identification of the paleosols indicated a suite that includes Entisols, Inceptisols, and Alfisols. To reconstruct paleovegetation, pedogenic carbonates were analyzed isotopically, and samples were collected and extracted for phytoliths . By combining these paleobotanical proxies with quantitative climatic proxies on whole rock geochemistry, we will present an integrated vegetation-climate history of the EECO at the margins of the Green River Basin. Second, we will present high-resolution record of vegetation patterns based on phytoliths from a section of the Renova Formation, Timberhills region, Montana dated to 39.2 ± 3 Ma. The section is composed of Alfisols, Entisols

  1. Severe Drought Events as Revealed in the Climate Records of China and Their Temperature Situations over the Last 1000 Years

    Institute of Scientific and Technical Information of China (English)

    ZHANG De'er

    2005-01-01

    The total 15 severe droughts are discovered with the aid of the "Retrieval System of Chinese Historical Climate Records" for the last 1000 years. The droughts are extensive to envelope more than 4 provinces and persistent to cover 3 yr or more, and their severity is equivalent to or in excess of that in the 1930s in China.According to the documentary records and restorations it can be inferred that most droughts are more severe than those in the last 50 years. The 15 droughts may either occur warm or in a cold climate background,with 11 of the 15 cases in the cold phase. This indicates the difference in climate correspondence between China and northern America, showing the severity of the events in China to be in a cold instead of a warm climate situation. That is likely to relate to the monsoon climate in eastern Asia.

  2. A compilation of Western European terrestrial records 60-8 ka BP: towards an understanding of latitudinal climatic gradients

    NARCIS (Netherlands)

    Moreno, A.; Svensson, A.; Brooks, S.J.; Connors, S.; Engels, S.; Fletcher, W.; Genty, D.; Heiri, O.; Labuhn, I.; Perşoiu, A.; Peyron, O.; Sadori, L.; Valero-Garcés, B.; Wulf, S.; Zanchetta, G; Data contributors, [Unknown

    2014-01-01

    Terrestrial records of past climatic conditions, such as lake sediments and speleothems, provide data of great importance for understanding environmental changes. However, unlike marine and ice core records, terrestrial palaeodata are often not available in databases or in a format that is easily ac

  3. PATMOS-x Cloud Climate Record Trend Sensitivity to Reanalysis Products

    Directory of Open Access Journals (Sweden)

    Michael J. Foster

    2016-05-01

    Full Text Available Continuous satellite-derived cloud records now extend over three decades, and are increasingly used for climate applications. Certain applications, such as trend detection, require a clear understanding of uncertainty as it relates to establishing statistical significance. The use of reanalysis products as sources of ancillary data could be construed as one such source of uncertainty, as there has been discussion regarding the suitability of reanalysis products for trend detection. Here we use three reanalysis products: Climate Forecast System Reanalysis (CFSR, Modern Era Retrospective Analysis for Research and Applications (MERRA and European Center for Medium range Weather Forecasting (ECMWF ERA-Interim (ERA-I as sources of ancillary data for the Pathfinder Atmospheres Extended/Advanced Very High Resolution Radiometer (PATMOS-x/AVHRR Satellite Cloud Climate Data Record (CDR, and perform inter-comparisons to determine how sensitive the climatology is to choice of ancillary data source. We find differences among reanalysis fields required for PATMOS-x processing, which translate to small but not insignificant differences in retrievals of cloud fraction, cloud top height and cloud optical depth. The retrieval variability due to choice of reanalysis product is on the order of one third the size of the retrieval uncertainty, making it a potentially significant factor in trend detection. Cloud fraction trends were impacted the most by choice of reanalysis while cloud optical depth trends were impacted the least. Metrics used to determine the skill of the reanalysis products for use as ancillary data found no clear best choice for use in PATMOS-x. We conclude use of reanalysis products as ancillary data in the PATMOS-x/AVHRR Cloud CDR do not preclude its use for trend detection, but for that application uncertainty in reanalysis fields should be better represented in the PATMOS-x retrieval uncertainty.

  4. Toward understanding nonstationarity in climate and hydrology through tree ring proxy records

    Science.gov (United States)

    Razavi, Saman; Elshorbagy, Amin; Wheater, Howard; Sauchyn, David

    2015-03-01

    Natural proxy records of hydroclimatic behavior, such as tree ring chronologies, are a rich source of information of past climate-driven nonstationarities in hydrologic variables. In this study, we investigate tree ring chronologies that demonstrate significant correlations with streamflows, with the objective of identifying the spatiotemporal patterns and extents of nonstationarities in climate and hydrology, which are essentially representations of past "climate changes." First and second-order nonstationarities are of particular interest in this study. As a prerequisite, we develop a methodology to assess the consistency and credibility of a regional network of tree ring chronologies as proxies for hydrologic regime. This methodology involves a cluster analysis of available tree ring data to understand and evaluate their dependence structure, and a regional temporal-consistency plot to assess the consistency of different chronologies over time. The major headwater tributaries of the Saskatchewan River basin (SaskRB), the main source of surface water in the Canadian Prairie Provinces, are used as the case study. Results indicate that stationarity might never have existed in the hydrology of the region, as the statistical properties of annual paleo-hydrologic proxy records across the basin, i.e., the mean and autocorrelation structure, have consistently undergone significant changes (nonstationarities) at different points in the history of the region. The spatial pattern of the changes in the mean statistic has been variable with time, indicating a time-varying cross-correlation structure across the tributaries of the SaskRB. Conversely, the changes in the autocorrelation structure across the basin have been in harmony over time. The results demonstrate that the 89 year period of observational record in this region is a poor representation of the long-term properties of the hydrologic regime, and shorter periods, e.g., 30 year periods, are by no means

  5. A multi-proxy record of Lateglacial climatic and environmental changes from Lake Mondsee (Upper Austria)

    Science.gov (United States)

    Lauterbach, S.; Brauer, A.; Dulski, P.; Schettler, G.; Milecka, K.; Hüls, M.; Andersen, N.; Namiotko, T.; Danielopol, D. L.; von Grafenstein, U.

    2009-04-01

    Within the frame of the ESF EuroCLIMATE project DecLakes (Decadal Holocene and Lateglacial variability of the oxygen isotopic composition in precipitation over Europe reconstructed from deep-lake sediments), the sediment record of pre-alpine Lake Mondsee (Upper Austria) has been investigated with a special focus on the Lateglacial. The use of a multi-proxy approach, including microfacies analysis, high-resolution -XRF element scanning, stable isotope analyses on valves of benthic ostracods, carbon geochemistry and analysis of pollen and ostracods enables the identification of major climatic fluctuations during this period. Furthermore, the parallel sampling strategy allows direct comparison of sensitivity of different proxies to climatic and environmental changes. The basal clastic-detrital facies of the profile is dominated by proglacial varves. The gradual onset of biochemical calcite precipitation is paralleled by a rapid shift in oxygen isotope ratios of benthic ostracod valves which marks the abrupt warming at the onset of the Lateglacial Interstadial. However, the allochthonous sediment input from the catchment shows no rapid shift but a gradual decrease. During the Allerød biozone sedimentation is dominated by homogeneous endogenic calcite with a very low detrital component. At the onset of the Younger Dryas cold period a marked decrease in oxygen isotope ratios within ca. 100 years occurs, followed by a reduction in the amount of endogenic calcite and the increase of detrital flux with a lag of about 100 years. The clear vegetational shift towards higher proportions of herbs and Juniperus and the frequency increase of detrital event layers lag the ^18O signal by about 250 years. In contrast, the rapid Holocene warming within 20-30 years is well reflected by the parallel ^18O rise and the establishment of a vegetation adapted to a warmer climate with the onset of massive calcite precipitation and the cessation of detrital input lagging by only few decades

  6. Solar Forcing of climate fluctuations in East Africa recorded in southeastern Mediterranean sediments

    Science.gov (United States)

    Hamann, Y.; Dulski, P.; Hajdas, I.; Ehrmann, W. U.; Schmiedl, G. H.; Haug, G. H.

    2010-12-01

    The proportions of terrigenous components in Mediterranean sediments derived from the atmosphere and rivers strongly depend on climate conditions in the source areas. The rainfall regimes of the northern and central part of the African continent are controlled by an interplay between global climate patterns and the regional hydrological balance. High-resolution XRF element records of a marine sediment core of the southeastern Levantine Sea (Mediterranean Sea; GeoTü SL112, 32° 44.52 N, 34° 39.02 E, water depth: 892 m) indicate distinctive changes in the sediment supply to the southeastern Mediterranean by the Nile River as well as the influx of aeolian dust from the Saharan desert. We observe minima in the concentration of the element iron (Fe), which we interpret as minima in dust input, during the well-known solar minima Oort, Wolf, Spoerer, Maunder, and Dalton. Wavelet analyses reveals a close correspondence in the periodicity in Fe input with the typical frequencies of solar cycles of about 90 and 210 years during the last 1400 years. Furthermore, the Fe record from the Levantine Sea sediments shows a remarkable similarity with the lake level record of Lake Naivasha in the eastern branch of the East African Rift and the pre-colonial drought history of Lake Malawi in the southern part of the African Rift Valley. Enhanced Saharan dust flux as indicated by high Fe content in the Levantine Sea core coincides with well-known droughts in equatorial east Africa as indicated by Lake Naivasha lowstands.

  7. A 250,000-year climatic record from great basin vein calcite: implications for milankovitch theory.

    Science.gov (United States)

    Winograd, I J; Coplen, T B; Szabo, B J; Riggs, A C

    1988-12-02

    A continuous record of oxygen-18 (delta(18)O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole-an open fault zone at Ash Meadows, Nevada-between 50 and 310 ka (thousand years ago). The configuration of the delta(18)O versus time curve closely resembles the marine and Antarctic ice core (Vostok) delta(18)O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 +/- 3 ka, at least 17,000 years earlier than indicated by the marine delta(18)O record and 7,000 years earlier than indicated by the less well dated Antarctic delta(18)O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine delta(18)O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

  8. A 250,000-year climatic record from great basin vein calcite: Implications for Milankovitch theory

    Science.gov (United States)

    Winograd, I.J.; Szabo, B. J.; Coplen, T.B.; Riggs, A.C.

    1988-01-01

    A continuous record of oxygen-18 (??18O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole - an open fault zone at Ash Meadows, Nevada - between 50 and 310 ka (thousand years ago). The configuration of the ??18O versus time curve closely resembles the marine and Antarctic ice core (Vostok) ??18O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 ?? 3 ka, at least 17,000 years earlier than indicated by the marine ??18O record and 7,000 years earlier than indicated by the less well dated Antarctic ??18O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine ??18O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

  9. Reconstruction of climate dynamics in an Arctic fjord environment: evidence from a multi-proxy high resolution marine record.

    Science.gov (United States)

    MacLachlan, S. E.; Howe, J.

    2012-12-01

    The cryosphere is a crucial component of the Earth's climate system, and comprises sea ice, snow, glaciers, ice cap, ice shelves, river and lake ice, ice sheets and frozen ground. The cryosphere has shown ice growth and decay on many timescales associated both with 100,000 year ice age cycles and with shorter-term (Ice Age. Crucially the cyosphere acts as a barometer for climate change because it provides a visible means of assessing the impacts of recent climate warming. Coastal Arctic regions are particularly sensitive to climate change, and records of glacier fluctuations can be used to infer past climate. The western Svalbard margin is a climatically sensitive region presently influenced by the warm and saline Atlantic water of the West Spitsbergen Current. This current is the northernmost extension of the Norwegian Atlantic Current that transports significant quantities of heat northward, maintaining the seas west of the Svalbard shelf increasingly ice free. For the Svalbard area there are currently a number of low-resolution (centennial to multi-decadal) marine records that span the Holocene. Despite their low resolution, several studies have highlighted abrupt environmental shifts and fluctuating glacial conditions during the Holocene. A few low-resolution lake records and other sporadic terrestrial datasets also exist providing a limited insight into the terrestrial environmental changes over the last two millennia. We have generated the first sub-decadal resolution late Holocene climatic record, in order to determine the nature and timing of environmental changes across transient climate events at an unprecedented temporal scale for this region. XRF analyses provides the high-resolution data series, which has been integrated with sedimentological data to better define the environmental processes; thus providing the basis for the reconstruction of climate change in this glaciated fjordic environment.

  10. Recording of climate and diagenesis through sedimentary DNA and fossil pigments at Laguna Potrok Aike, Argentina

    Science.gov (United States)

    Vuillemin, Aurèle; Ariztegui, Daniel; Leavitt, Peter R.; Bunting, Lynda; The Pasado Science Team

    2016-04-01

    Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. In theory, benthic microbial community composition should depend on environmental features and geochemical conditions of surrounding sediments, as well as ontogeny of the subsurface environment as sediment degraded. In principle, DNA in sediments should be composed of ancient and extant microbial elements persisting at different degrees of preservation, although to date few studies have quantified the relative influence of each factor in regulating final composition of total sedimentary DNA assemblage. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two climatic intervals (Mid-Holocene, 5 ka BP; Last Glacial Maximum, 25 ka BP) whose sediments harbored active microbial populations were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. The genetic assemblage recovered from the Holocene record revealed a microbial community displaying metabolic complementarities that allowed prolonged degradation of organic matter to methane. The series of Archaea identified throughout the Holocene record indicated an age-related stratification of these populations brought on by environmental selection during early diagenesis. These characteristics were associated with sediments resulting from endorheic lake conditions and stable pelagic regime, high evaporative stress and concomitant high algal productivity. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. Comparison of sedimentary DNA composition

  11. Oxygen isotope records of Holocene climate variability in the Pacific Northwest

    Science.gov (United States)

    Steinman, Byron A.; Pompeani, David P.; Abbott, Mark B.; Ortiz, Joseph D.; Stansell, Nathan D.; Finkenbinder, Matthew S.; Mihindukulasooriya, Lorita N.; Hillman, Aubrey L.

    2016-06-01

    Oxygen isotope (δ18O) measurements of authigenic carbonate from Cleland Lake (southeastern British Columbia), Paradise Lake (central British Columbia), and Lime Lake (eastern Washington) provide a ∼9000 year Holocene record of precipitation-evaporation balance variations in the Pacific Northwest. Both Cleland Lake and Paradise Lake are small, surficially closed-basin systems with no active inflows or outflows. Lime Lake is surficially open with a seasonally active overflow. Water isotope values from Cleland and Paradise plot along the local evaporation line, indicating that precipitation-evaporation balance is a strong influence on lake hydrology. In contrast, Lime Lake water isotope values plot on the local meteoric water line, signifying minimal influence by evaporation. To infer past hydrologic balance variations at a high temporal resolution, we sampled the Cleland, Paradise, and Lime Lake sediment cores at 1-60 mm intervals (∼3-33 years per sample on average) and measured the isotopic composition of fine-grained (ocean-atmosphere changes in the Pacific basin. Results from mid-Holocene (6000 yr BP) climate model simulations conducted as part of the Paleoclimate Modeling Intercomparison Project Phase 3 (PMIP3) indicate that in much of western North America, the cold season (October-March) was wetter and the warm season (April-September) was considerably drier relative to the late Holocene, leading to an overall drier climate in western North America with enhanced hydroclimatic seasonality. This is consistent with inferences from the Cleland and Paradise δ18O records, which lake modeling experiments indicate are strongly influenced by cold season precipitation-evaporation balance. This also explains apparent inconsistencies between the lake δ18O records and other proxies of hydroclimatic change from the greater Pacific Northwest region that are less sensitive to cold season climate and thus indicate relatively drier conditions during the mid-Holocene. The

  12. Long-Term Sun Climate Connections, Revealed by the Analyses of Historical and Other Proxy Records

    Science.gov (United States)

    Pang, K. D.; Yau, K.

    2004-12-01

    The Sun, once considered constant, actually goes through 11-year, decadal, centennial, and even longer cycles. Our analysis of historical sunspot and aurora records, carbon-14 and beryllium-10 abundances from long-lived trees and deep polar ice cores, respectively, shows that it has gone through nine long cycles in the past 1800 years. Although these changes amounted to China). Total solar irradiances, reconstructed from historical sunspot records, were 0.25% lower then. This correlates nicely with an estimated 0.5-degree drop in Northern Hemisphere summer surface temperatures during the Little Ice Age [Lean, GRL 22, 3195, 1995]. We have also analyzed Chinese historical weather records for comparison. Reports of unseasonable cold are classified by the degree of severity: (1) Late (April-June) or early (July-September) killing frosts; (2) Bitter cold/heavy snowfall; and (3) Heavy sustained snowfall, bitter cold with frozen wells, rivers and icebound seas. The latter cases were often widespread and multi-year. All categories occurred most frequently during the coldest part of the Little Ice Age. The Category 3 episodes were in 1652-54, 1656, 1664, 1670-72, 1676-77, 1683, 1688-91, 1716, and 1718-19. For example the Yangtze River and its lakes froze up to 3-4 times in 1650-1700. The coldest period thus coincides with the Maunder Minimum, and is consistent with general circulation model hindcast winter conditions for China [Shindell, Science, 294, 2149, 2001]. There was only one Category 3 episode between the Maunder and Dalton Minima--in 1761 (due to a large volcanic eruption); and two in the Dalton Minimum (1795-1825)--in 1796 and 1814-17. The Sun has gradually brightened since the Dalton Minimum. But the climate of China remained cold through the 19th century, as in the rest of the world, probably due to increased volcanic aerosol loading of the atmosphere [Sato, JGR 98, 22987, 1993]. The climate of China seems to have been warm during the Late 14th-Century Maximum

  13. A Fundamental Climate Data Record of Intercalibrated Brightness Temperature Data from SSM/I and SSMIS

    Science.gov (United States)

    Sapiano, M. R. P.; Berg, W. K.; McKague, D.; Kummerow, C. D.

    2012-04-01

    The first Special Sensor Microwave/Imager (SSM/I) was launched in June 1987 on the Defense Meteorological Satellite Program's (DMSP) F08 spacecraft and started what is now a nearly continuous 24-year record of passive microwave imager data that can be used to monitor the climate system. This includes such fields as precipitation (over both land and ocean), the extent of sea ice and snow, sea ice concentration, total precipitable water, cloud liquid water, and surface wind speed over oceans. A total of nine window channel radiometers have been launched to date in the DMSP series including the SSM/I instrument on board F08, F10, F11, F13, F14, and F15 followed by the Special Sensor Microwave Imager/Sounder (SSMIS) on board F16, F17, and F18, which is expected to operate for at least the next decade. As a result, this data record provides the best available source of long-term global observations of several hydrological variables for climate applications. Although the DMSP sensors provide a long-term record, because the sensors were developed for operational use there are a number of issues that must be addressed to produce a dataset suitable for use in climate applications. There are a several quality control and calibration issues including, but not limited to, quality control of the original antenna temperatures, geolocation, cross-track bias corrections, solar and lunar intrusion issues and emissive antennas. The goal of producing an FCDR of brightness temperature data involves not only addressing many of these instrument issues, but also developing a well-documented, transparent approach that allows for subsequent improvements as well as a framework for incorporating future sensors. Once the data have been quality controlled and various calibration corrections have been applied, the goal is to adjust the calibration of the various sensors so that they are physically consistent. Such intercalibration does not correct for changes due to local observing time, which

  14. Solar forcing of climate during the last millennium recorded in lake sediments from northern Sweden

    DEFF Research Database (Denmark)

    Kokfelt, Ulla; Muscheler, Raimund

    2013-01-01

    We report on a sediment record from a small lake within the subarctic wetland complex Stordalen in northernmost Sweden covering the last 1000 years. Variations in the content of minerogenic material are found to follow reconstructed variations in the activity of the Sun between the 13th and 18th ...... and in particular solar minima, causing dry conditions with resulting decreased runoff....... century. Periods of low solar activity are associated with minima in minerogenic material and vice versa. A comparison between the sunspot cycle and a long instrumental series of summer precipitation further reveals a link between the 11-year solar cycle and summer precipitation variability since around...... 1960. Solar minima are in this period associated with minima in summer precipitation, whereas the amount of summer precipitation increases during periods with higher solar activity. Our results suggest that the climate responds to both the 11-year solar cycle and to long-term changes in solar activity...

  15. Combining Satellite and in Situ Data with Models to Support Climate Data Records in Ocean Biology

    Science.gov (United States)

    Gregg, Watson

    2011-01-01

    The satellite ocean color data record spans multiple decades and, like most long-term satellite observations of the Earth, comes from many sensors. Unfortunately, global and regional chlorophyll estimates from the overlapping missions show substantial biases, limiting their use in combination to construct consistent data records. SeaWiFS and MODIS-Aqua differed by 13% globally in overlapping time segments, 2003-2007. For perspective, the maximum change in annual means over the entire Sea WiFS mission era was about 3%, and this included an El NinoLa Nina transition. These discrepancies lead to different estimates of trends depending upon whether one uses SeaWiFS alone for the 1998-2007 (no significant change), or whether MODIS is substituted for the 2003-2007 period (18% decline, P less than 0.05). Understanding the effects of climate change on the global oceans is difficult if different satellite data sets cannot be brought into conformity. The differences arise from two causes: 1) different sensors see chlorophyll differently, and 2) different sensors see different chlorophyll. In the first case, differences in sensor band locations, bandwidths, sensitivity, and time of observation lead to different estimates of chlorophyll even from the same location and day. In the second, differences in orbit and sensitivities to aerosols lead to sampling differences. A new approach to ocean color using in situ data from the public archives forces different satellite data to agree to within interannual variability. The global difference between Sea WiFS and MODIS is 0.6% for 2003-2007 using this approach. It also produces a trend using the combination of SeaWiFS and MODIS that agrees with SeaWiFS alone for 1998-2007. This is a major step to reducing errors produced by the first cause, sensor-related discrepancies. For differences that arise from sampling, data assimilation is applied. The underlying geographically complete fields derived from a free-running model is unaffected

  16. East African climate fluctuations over the last 1400 years recorded in southeastern Mediterranean sediments

    Science.gov (United States)

    Hamann, Y.; Dulski, P.; Ehrmann, W.; Schmiedl, G.; Haug, G.

    2008-12-01

    The southeastern Mediterranean Sea sedimentary history of the late Holocene was influenced by distinctive changes in Nile River sediment discharge and Saharan dust influx. We present high-resolution XRF element data of a marine sediment core of the southeastern Levantine Sea (GeoTü SL112, 32° 44.52´ N, 34° 39.02´ E, water depth: 892 m) spanning the last 1400 years. We suggest a strong relationship between humidity changes in east Africa and the corresponding sedimentological response in the Levantine Sea. The Fe record of our Levantine Sea sediment record shows a remarkable similarity with the lake level record of Lake Naivasha (Kenya) (Verschuren et al., Nature, 2000) and the pre-colonial drought history of Lake Malawi (east Africa). Several intervals of enhanced Saharan dust flux as indicated by high Fe values in the Levantine Sea core coincide with well-known droughts in equatorial east Africa and Lake Naivasha lowstands. Frequency analysis suggests that solar variability has been a major influence in these climate fluctuations. The Fe record of our core, which we interpret as Saharan dust influx to the southeast Levantine Sea, is dominated by cyclicities of approximately 90 and 200 years, known as the Gleissberg and Suess cycles. The most pronounced periods of decreased dust accumulation in the southeast Levantine Sea occurred at about 1.1 kyr BP, 0.7 kyr BP, 0.55 kyr BP, 0.3 kyr BP and 0.1 kyr BP, coincident with the solar minima of Oort, Wolf, Spoerer, Maunder and Dalton.

  17. Impact of Holocene climate variability on lacustrine records and human settlements in South Greenland

    Directory of Open Access Journals (Sweden)

    T. Guillemot

    2015-11-01

    Full Text Available Due to its sensitivity to climate changes, south Greenland is a particularly suitable area to study past global climate changes and their influence on locale Human settlements. A paleohydrological investigation was therefore carried out on two river-fed lakes: Lake Qallimiut and Little Kangerluluup, both located close to the Labrador Sea in the historic farming center of Greenland. Two sediment cores (QAL-2011 and LKG-2011, spanning the last four millennia, were retrieved and showed similar thin laminae, described by high magnetic susceptibility and density, high titanium and TOC / TN atomic ratio, and coarse grain size. They are also characterized either by inverse grading followed by normal grading or by normal grading only and a prevalence of red amorphous particles and lignocellulosic fragments, typical of flood deposits. Flood events showed similar trend in both records: they mainly occurred during cooler and wetter periods characterized by weaker Greenlandic paleo-temperatures, substantial glacier advances, and a high precipitation on the Greenlandic Ice Sheet and North Atlantic ice-rafting events. They can therefore be interpreted as a result of ice and snow-melting episodes. They occurred especially during rapid climate changes (RCC such as the Middle to Late Holocene transition around 2250 BC, the Sub-boreal/Sub-atlantic transition around 700 BC and the Little Ice Age (LIA between AD 1300 and AD 1900, separated by cycles of 1500 years and driven by solar forcing. These global RCC revealed by QAL-2011 and LKG-2011 flood events may have influenced Human settlements in south Greenland, especially the paleo-Eskimo cultures and the Norse settlement, and have been mainly responsible for their demise.

  18. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Science.gov (United States)

    Lattanzio, A.; Fell, F.; Bennartz, R.; Trigo, I. F.; Schulz, J.

    2015-10-01

    Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA) Climate Data Record (CDR) currently comprising up to 24 years (1982-2006) of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS) stability requirements for desert reference sites. The limitation in quality due to non-removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. The first step consists of the application of a robust and reliable cloud mask, taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers, some clouds can still remain undetected. A second step relies on a post-processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high-quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR release.

  19. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Directory of Open Access Journals (Sweden)

    A. Lattanzio

    2015-10-01

    Full Text Available Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA Climate Data Record (CDR currently comprising up to 24 years (1982–2006 of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS stability requirements for desert reference sites. The limitation in quality due to non-removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. The first step consists of the application of a robust and reliable cloud mask, taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers, some clouds can still remain undetected. A second step relies on a post-processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high-quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR release.

  20. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Directory of Open Access Journals (Sweden)

    A. Lattanzio

    2015-07-01

    Full Text Available Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA Climate Data Record (CDR currently comprising up to 24 years (1982–2006 of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained and Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS stability requirements for desert reference sites. The limitation in quality due to non removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. A first step consists on the application of a robust and reliable cloud mask taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers some clouds can still remain undetected. A second step relies on a post processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR Release.

  1. Verification of a new NOAA/NSIDC passive microwave sea-ice concentration climate record

    Directory of Open Access Journals (Sweden)

    Walter N. Meier

    2014-12-01

    Full Text Available A new satellite-based passive microwave sea-ice concentration product developed for the National Oceanic and Atmospheric Administration (NOAA Climate Data Record (CDR programme is evaluated via comparison with other passive microwave-derived estimates. The new product leverages two well-established concentration algorithms, known as the NASA Team and Bootstrap, both developed at and produced by the National Aeronautics and Space Administration (NASA Goddard Space Flight Center (GSFC. The sea-ice estimates compare well with similar GSFC products while also fulfilling all NOAA CDR initial operation capability (IOC requirements, including (1 self-describing file format, (2 ISO 19115-2 compliant collection-level metadata, (3 Climate and Forecast (CF compliant file-level metadata, (4 grid-cell level metadata (data quality fields, (5 fully automated and reproducible processing and (6 open online access to full documentation with version control, including source code and an algorithm theoretical basic document. The primary limitations of the GSFC products are lack of metadata and use of untracked manual corrections to the output fields. Smaller differences occur from minor variations in processing methods by the National Snow and Ice Data Center (for the CDR fields and NASA (for the GSFC fields. The CDR concentrations do have some differences from the constituent GSFC concentrations, but trends and variability are not substantially different.

  2. Verification of a New NOAA/NSIDC Passive Microwave Sea-Ice Concentration Climate Record

    Science.gov (United States)

    Meier, Walter N.; Peng, Ge; Scott, Donna J.; Savoie, Matt H.

    2014-01-01

    A new satellite-based passive microwave sea-ice concentration product developed for the National Oceanic and Atmospheric Administration (NOAA)Climate Data Record (CDR) programme is evaluated via comparison with other passive microwave-derived estimates. The new product leverages two well-established concentration algorithms, known as the NASA Team and Bootstrap, both developed at and produced by the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC). The sea ice estimates compare well with similar GSFC products while also fulfilling all NOAA CDR initial operation capability (IOC) requirements, including (1) self describing file format, (2) ISO 19115-2 compliant collection-level metadata,(3) Climate and Forecast (CF) compliant file-level metadata, (4) grid-cell level metadata (data quality fields), (5) fully automated and reproducible processing and (6) open online access to full documentation with version control, including source code and an algorithm theoretical basic document. The primary limitations of the GSFC products are lack of metadata and use of untracked manual corrections to the output fields. Smaller differences occur from minor variations in processing methods by the National Snow and Ice Data Center (for the CDR fields) and NASA (for the GSFC fields). The CDR concentrations do have some differences from the constituent GSFC concentrations, but trends and variability are not substantially different.

  3. Chironomid oxygen isotope record of mid- to late Holocene climate evolution from southern Spitsbergen

    Science.gov (United States)

    Arppe, Laura; Kurki, Eija; Wooller, Matthew; Luoto, Tomi; Zajączkowski, Marek; Ojala, Antti

    2017-04-01

    The oxygen isotope composition of head capsule chitin of chironomid larvae picked from a sediment core covering the past 5500 years from lake Svartvatnet in southern Spitsbergen was used to reconstruct the isotopic composition of oxygen in lake water (δ18Olw) and local precipitation. Consistent with the gradual cooling of climate over the Neoglacial period, the δ18Olw record displays a gentle decreasing trend over the study period. The Svartvatnet δ18Olwrecord shows a maximum at ca. 1900-1800 cal BP, consistent with the timing of the Roman Warm Period, and three negative excursions increasing in intensity towards the present-day at 3400-3200, 1250-1100 and 350-50 cal BP, which are tentatively linked to multidecadal periods of low solar activity amplified by oceanic and atmospheric feedbacks. The time period of the Little Ice Age shows a two-step decrease in δ18Olwvalues, with a remarkable, 8-9‰ drop at 350-50 cal BP construed to predominantly represent significantly decreased winter temperatures during a period of increased seasonal differences and extended sea ice cover inducing changes in moisture source regions. Similarity of the trends between the δ18Olwrecord and a July-T reconstruction based on chironomid assemblages (Luoto et al., in review) from the same core suggests that air temperature exerts a significant control over the δ18Olwvalues, but the record is most likely influenced by changes in sea ice extent and possibly the seasonal distribution of precipitation. Reference: Luoto TP, Ojala A, Brooks S et al. Synchronized proxy-based temperature reconstructions reveal mid-to late Holocene climate oscillations in High Arctic Svalbard. Journal of Quaternary Science, submitted.

  4. North Pacific Climate Variability in Ice Core Accumulation Records From Eclipse Icefield, Yukon, Canada

    Science.gov (United States)

    Yalcin, K.; Wake, C. P.; Kreutz, K. J.

    2005-12-01

    Three annually dated ice cores from Eclipse Icefield, Yukon, Canada provide records of net accumulation spanning the last 100 to 500 years. The ice cores were dated by annual layer counting verified by reference horizons provided by radioactive fallout and volcanic eruptions. Annual layers become progressively thinner with depth in the Eclipse ice cores, requiring reconstruction of original annual layer thicknesses by correcting for ice creep. An empirical approach was used that is based on the observed layer thicknesses from annual layer counting of the Eclipse ice cores. Accumulation records are highly reproducible with 73% of the signal shared between the three cores. The accumulation time-series shows considerable decadal scale variability that can be related to climate regimes that characterize the North Pacific. For example, periods of high accumulation are noted from 1470-1500, 1540-1560, and 1925-1975. Periods of low accumulation are observed between 1500-1540, 1680-1780, and 1875-1925. The strongest multi-year drop in accumulation is seen between 1979 and 1984, although there are isolated years with lower accumulation. This drop in accumulation is possibly related to the 1977 regime shift in the Pacific Decadal Oscillation. However, PDO regime shifts are not always reflected in the accumulation time series, implying a non-linear response or modulation by other modes of climate variability such as ENSO. Its is noteworthy that the Eclipse accumulation time series is out of phase with the accumulation time series from nearby Mount Logan on all time scales for reasons to be investigated.

  5. Evaluation of annual resolution coral geochemical records as climate proxies in the Great Barrier Reef of Australia

    Science.gov (United States)

    Deng, Wenfeng; Wei, Gangjian; McCulloch, Malcolm; Xie, Luhua; Liu, Ying; Zeng, Ti

    2014-12-01

    Sampling of annually banded massive coral skeletons at annual (or higher) resolutions is increasingly being used to obtain replicate long-term time series of changing seawater conditions. However, few of these studies have compared and calibrated the lower annual resolution records based on coral geochemical tracers with the corresponding instrumental climate records, although some studies have inferred the climatic significance of annual coral series derived from averages of monthly or sub-annual records. Here, we present annual resolution analysis of coral records of elemental and stable isotopic composition that are approximately 70 years long. These records were preserved in two coexisting colonies of Porites sp. from Arlington Reef, on the Great Barrier Reef in Australia, and are used to evaluate the climatic significance of annually resolved coral geochemical proxies. The geochemical records of coral sample "10AR2," with its faster and relatively constant annual growth rate, appear to have been independent of skeletal growth rate and other vital effects. The annual resolution of Sr/Ca and Δδ18O time series was shown to be a good proxy for annual sea surface temperature (SST; r = -0.67, n = 73, p < 0.0000001) and rainfall records ( r = -0.34, n = 67, p < 0.01). However, a slower growing coral sample, "10AR1" showed significantly lower correlations ( r = -0.20, n = 71, p = 0.05 for Sr/Ca and SST; r = -0.19, n = 67, p = 0.06 for Δδ18O and rainfall), indicating its greater susceptibility to biological/metabolic effects. Our results suggest that while annually resolved coral records are potentially a valuable tool for determining, in particular, long timescale climate variability such as Pacific Decadal Oscillation, Interdecadal Pacific Oscillation, and other climatic factors, the selection of the coral sample is important, and replication is essential.

  6. Human and climate impacts on Holocene fire activity recorded in polar and mountain ice cores

    Science.gov (United States)

    Kehrwald, Natalie; Zennaro, Piero; Kirchgeorg, Torben; Li, Quanlian; Wang, Ninglian; Power, Mitchell; Zangrando, Roberta; Gabrielli, Paolo; Thompson, Lonnie; Gambaro, Andrea; Barbante, Carlo

    2014-05-01

    Fire is one of the major influences of biogeochemical change on local to hemispheric scales through emitting greenhouse gases, altering atmospheric chemistry, and changing primary productivity. Levoglucosan (1,6-anhydro-β-D-glucopyranose) is a specific molecular that can only be produced by cellulose burning at temperatures > 300°C, comprises a major component of smoke plumes, and can be transported across > 1000 km distances. Levoglucosan is deposited on and archived in glaciers over glacial interglacial cycles resulting in pyrochemical evidence for exploring interactions between fire, climate and human activity. Ice core records provide records of past biomass burning from regions of the world with limited paleofire data including polar and low-latitude, high-altitude regions. Here, we present Holocene fire activity records from the NEEM, Greenland (77° 27'N; 51° 3'W; 2454 masl), EPICA Dome C, Antarctica (75° 06'S; 123° 21'E; 3233 masl), Kilimanjaro, Tanzania (3° 05'S, 21.2° E, 5893 masl) and the Muztagh, China (87.17° E; 36.35° N; 5780 masl ice cores. The NEEM ice core reflects boreal fire activity from both North American and Eurasian sources. Temperature is the dominant control of NEEM levoglucosan flux over decadal to millennial time scales, while droughts influence fire activity over sub-decadal timescales. Our results demonstrate the prominence of Siberian fire sources during intense multiannual droughts. Unlike the NEEM core, which incorporates the largest land masses in the world as potential fire sources, EPICA Dome C is located far from any possible fire source. However, EPICA Dome C levoglucosan concentrations are consistently above detection limits and demonstrate a substantial 1000-fold increase in fire activity beginning approximately 800 years ago. This significant and sustained increase coincides with Maori arrival and dispersal in New Zealand augmented by later European arrival in Australia. The EPICA Dome C levoglucosan profile is

  7. Climate, productivity, and intermediate water nutrients: new records from bamboo coral Ba/Ca

    Science.gov (United States)

    Lavigne, M.; Hill, T. M.; Spero, H. J.; Guilderson, T. P.

    2010-12-01

    A geochemical nutrient proxy from deep-sea corals would provide decadal to centennial scale records of intermediate-water nutrient dynamics. Such records could be used to determine how intermediate water masses (300-2000m) are affected by decadal scale climate change (e.g. Pacific Decadal Oscillation) via carbon cycling, export production, and intermediate water-mass circulation/ventilation. Because seawater barium (BaSW ) has a nutrient-like distribution in the water-column (similar to silicate), Ba/Ca records have been used to trace upwelled nutrient supply in shallow water surface corals isolated from terrestrial barium sources. Here we show the first calibration of a nutrient proxy from skeletal barium preserved in the calcitic internodes of bamboo corals. Our calibration was calculated from a depth transect (500-2000m) of Isidella and Keratoisis corals spanning a silicate and (BaSW ) gradient on the California Margin (Ba/Ca coral (µmol/mol) = 0.117 BaSW (nmol/kg ) + 0.835; R2 = 0.88; n = 29). The strong linear correlation between Ba/Ca coral and BaSW suggests that coral Ba/Ca is a reliable recorder of seawater barium (and, therefore, silicate). We find a distribution coefficient (DBa) for bamboo coral Ba/Ca of 1.3±0.1, similar to that of other corals (surface and deep-sea dwelling) and inorganic calcium carbonate precipitation experiments (DBa = 1.2-1.5). This implies that, as true for other carbonates, Ba incorporation is primarily driven by ionic substitution and holds promise as a globally applicable nutrient proxy in bamboo corals. High-resolution Ba/Ca timeseries records sampled via LA-ICP-MS in two co-located California Margin corals (Pioneer Seamount; 830m; 37°22’27”N) co-vary with ~decadal-scale variations in silicate and nitrate measured at 500m depth (CalCOFI line 80 sta. 60; 34°8’60”N). This suggests that high-resolution records of bamboo coral Ba/Ca can be used to reconstruct broad changes in intermediate water nutrients driven by

  8. A compilation of Western European terrestrial records 60-8 ka BP: towards an understanding of latitudinal climatic gradients

    Science.gov (United States)

    Moreno, Ana; Svensson, Anders; Brooks, Stephen J.; Connor, Simon; Engels, Stefan; Fletcher, William; Genty, Dominique; Heiri, Oliver; Labuhn, Inga; Perşoiu, Aurel; Peyron, Odile; Sadori, Laura; Valero-Garcés, Blas; Wulf, Sabine; Zanchetta, Giovanni

    2014-12-01

    Terrestrial records of past climatic conditions, such as lake sediments and speleothems, provide data of great importance for understanding environmental changes. However, unlike marine and ice core records, terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non-specialist. As a consequence, many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations, comparisons, or modelling exercises. Here we present a compilation of Western European terrestrial palaeo-records covering, entirely or partially, the 60-8-ka INTIMATE time period. The compilation contains 56 natural archives, including lake records, speleothems, ice cores, and terrestrial proxies in marine records. The compilation is limited to include records of high temporal resolution and/or records that provide climate proxies or quantitative reconstructions of environmental parameters, such as temperature or precipitation, and that are of relevance and interest to a broader community. We briefly review the different types of terrestrial archives, their respective proxies, their interpretation and their application for palaeoclimatic reconstructions. We also discuss the importance of independent chronologies and the issue of record synchronization. The aim of this exercise is to provide the wider palaeo-community with a consistent compilation of high-quality terrestrial records, to facilitate model-data comparisons, and to identify key areas of interest for future investigations. We use the compilation to investigate Western European latitudinal climate gradients during the deglacial period and, despite of poorly constrained chronologies for the older records, we summarize the main results obtained from NW and SW European terrestrial records before the LGM.

  9. Holocene climate change in the Central Tibetan Plateau inferred by lacustrine sediment geochemical records

    Institute of Scientific and Technical Information of China (English)

    WU; YanHong

    2007-01-01

    [1]Morrill C,Overpeck J T,Cole J E.A synthesis of abrupt changes in the Asian summer monsoon since the last deglaciation.Holocene,2003,13:465-476[2]Herzschuh U.Palaeo-moisture evolution at the margins of the Asian monsoon during the last 50 ka.Quat Sci Rev,2006,25:163-178[3]Thompson L G,Yao T,Davis M E,et al.Tropical climate instability:the last Glacial cycle from a Qinghai Tibetan ice core.Science,1997,276:1821-1825[4]Fang J.Lake evolution during the past 30000 years in China,and its implication for the environmental change.Quat Res,1991,36:1-24[5]Gasse F,Arnold M,Fontes J C,et al.A 13000-year climate record from wetstern Tibet.Nature,1991,353:742-745[6]Lister G S,Kelts K,Chen K,et al.Lake Qinghai,China:closed-basin lake levels and oxygen isotope record for ostracode since the last Pleistocene.Paleogeogr Paleoclimatol Paleoecol,1991,54:141-162[7]Van Campo E,Gasse F.Pollen-and diatom-inferred climatic and hydrological changes in Sumxi Co Basin (western Tibet) since 13000 yr B.P.Quat Res,1993,39:300-313[8]Fontes J Ch,Melieres F,Gibert E,et al.Stable isotope and radiocarbon balances of two Tibetan lakes (Sumxi Co,Longmu Co) from 13000 yr BP.Quat Sci Rev,1993,12:875-887[9]Gu Z Y,Liu J Q,Yuan B Y,et al.The changes in monsoon influence in the Qinghai-Tibetan Plateau during the past 12000 years-geo-chemical evidence from L.Silling Co sediments.Chin Sci Bull (in Chinese),1993,38(1):61-64[10]Sun X J,Du N Q,Chen Y S,et al.Analysis on pollen of lake sediment in Silling Co,Tibet.Acta Bota Sin (in Chinese),1993,35(12):943-950[11]Li Y F,Zhang Q S,Li B Y,et al.Ostracod fauna and environmental changes during the past 17000 years in Western Tibet.Acta Geogr Sin (in Chinese),1994,49(1):46-53[12]Avouac J P,Dobremez J F,Bourjot L.Paleoclimatic interpretation of a topgraphic profile across middle Holocene regressive shorelines of Longmu Co (Western Tibet).Paleogeogr Paleoclimatol Paleoecol,1996,120:93-104[13]Shen C M,Tang L Y.Pollen evidence for monsoon variation in Tibetan Plateau

  10. Rapid Climatic Change during Past 60 ka Recorded in NE Indian Ocean and Its Correspondence from South China Land

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    According to the marine records from the Bay of Bengal, northeastern Indian Ocean, and the continental records from the South China, the authors make a detailed discussion in this paper about the correlation between them and their implication of rapid climatic change. The marine records show its good response to the high latitudes both for cold events and for warm ones while the continental records mainly mirror those cold Heinrich events corresponding to the North Atlantic but bear strongly a local color in reflecting warm events. The authors assume that the heat transmission style may cause the unbalanced coupling relationship.

  11. Environmental response to the cold climate event 8200 years ago as recorded at Hoejby Soe, Denmark

    Energy Technology Data Exchange (ETDEWEB)

    Rasmussen, Peter (Geological Survey of Denmark and Greenland, Copenhagen (Denmark)); Ulfeldt Hede, M.; Noe-Nygaard, N. (Univ. of Copenhagen, Dept. of Geography and Geology, Copenhagen (Denmark)); Clarke, A.L. (APEM Manchester Lab., Stockport (United Kingdom)); Vinebrooke, R.D. (Univ. of Alberta, Dept. of Biological Science - Freshwater Biodiversity Lab., Edmonton (Canada))

    2008-07-15

    The need for accurate predictions of future environmental change under conditions of global warming has led to a great interest in the most pronounced climate change known from the Holocene: an abrupt cooling event around 8200 years before present (present = A.D. 1950), also known as the '8.2 ka cooling event' (ka = kilo-annum = 1000 years). This event has been recorded as a negative delta18OMICRON excursion in the central Greenland ice cores (lasting 160 years with the lowest temperature at 8150) and in a variety of other palaeoclimatic archives including lake sediments, ocean cores, speleothems, tree rings, and glacier oscillations from most of the Northern Hemisphere. In Greenland the maximum cooling was estimated to be 6 +- 2 deg. C while in southern Fennoscandia and the Baltic countries pollenbased quantitative temperature reconstructions indicate a maximum annual mean temperature decrease of around 1.5 deg. C. Today there is a general consensus that the primary cause of the cooling event was the final collapse of the Laurentide ice sheet near Hudson Bay and the associated sudden drainage of the proglacial Lake Agassiz into the North Atlantic Ocean around 8400 B.P. . This freshwater outflow, estimated to amount to c. 164,000 km3 of water, reduced the strength of the North Atlantic thermohaline circulation and thereby the heat transported to the North Atlantic region, resulting in an atmospheric cooling. The climatic consequences of this meltwater flood are assumed to be a good geological analogue for future climate-change scenarios, as a freshening of the North Atlantic is projected by almost all global-warming models and is also currently being registered in the region. In an ongoing project, the influence of the 8.2 ka cooling event on a Danish terrestrial and lake ecosystem is being investigated using a variety of biological and geochemical proxy data from a sediment core extracted from Hojby So, north-west Sjaelland. Here we present data on

  12. Mt. Logan Ice Core Record of North Pacific Holocene Climate Variability

    Science.gov (United States)

    Osterberg, E. C.; Mayewski, P. A.; Fisher, D. A.; Kreutz, K. J.; Handley, M. J.; Sneed, S. B.

    2006-12-01

    A >12,000 year-long, continuous, high-resolution (sub-annual to multi-decadal) ice core record from the summit plateau (5300 m asl) of Mt. Logan, Yukon, Canada, reveals large, abrupt fluctuations in North Pacific climate throughout the Holocene with a 1-2 ky periodicity. Co-registered major ion, trace element and stable isotope time series reveal a strong inverse relationship between precipitation δ18O and atmospheric seasalt and dust concentrations over multi-decadal to millennial periods (rMt. Logan represent changes in moisture source region between dominantly cold North Pacific waters (more zonal circulation; enriched stable isotope values) and warmer subtropical waters (more meridional circulation; depleted stable isotope values). Consequently, Holocene millennial-scale stable isotope fluctuations in the Mt. Logan core have a larger amplitude (6-9‰ for δ18O) than those found in Greenland and Canadian Arctic ice core records (e.g. 2-3‰ for GISP2 δ18O). Over the instrumental period (1948-1998), higher Mt. Logan dust concentrations are strongly associated with enhanced springtime cyclonic activity over East Asian desert source regions (rMt. Logan seasalt aerosol concentrations are related to the wintertime strength of the Aleutian Low pressure center (r<-0.45, p<0.001). We use these calibrated proxy relationships to propose a conceptual model of North Pacific atmospheric circulation during the Holocene.

  13. Obliquity-paced climate change recorded in Antarctic debris-covered glaciers.

    Science.gov (United States)

    Mackay, Sean L; Marchant, David R

    2017-02-10

    The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change.

  14. Early Eocene hyperthermals record orbitally controlled changes in high latitude climates

    Science.gov (United States)

    Galeotti, S.; DeConto, R. M.; Lanci, L.; Pagani, M.; Rohl, U.; Westerhold, T.; Zachos, J. C.

    2012-04-01

    The Late Paleocene to Early Eocene records a succession of short-term (104 yr) negative carbon isotope excursions (CIEs) in marine carbonates and organic carbon. Available data indicate that at least three of these episodes, including the Paleocene Eocene Thermal Maximum (PETM) at ca. 55.5, the Eocene Thermal Maximum (ETM)2 at ca. 53.5 Ma and the ETM3 at ca. 52 Ma, were associated with rapid warming, and widespread marine carbonate dissolution forced by shoaling of the carbonate lysocline and lowering of the carbonate saturation state. Large temperature raises associated with decreased δ13C values in both terrestrial and oceanic records and concomitant acidification of oceanic waters implies that hyperthermals were caused by the addition of massive amounts of 13C-depleted greenhouse gases (CH4 and/or CO-2) into the atmosphere and subsequent sequestration by oceanic waters. Cyclostratigraphic analyses of marine sequences provided evidence that CIEs and associated carbonate dissolution episodes were linked to orbital changes in insolation. Here we show grounds that Early Eocene hyperthermals are part of a continuum of δ13C anomaly and carbonate dissolution episodes and are triggered by long-term orbitally-controlled changes in local climates at high latitudes.

  15. Obliquity-paced climate change recorded in Antarctic debris-covered glaciers

    Science.gov (United States)

    Mackay, Sean L.; Marchant, David R.

    2017-01-01

    The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change. PMID:28186094

  16. Obliquity-paced climate change recorded in Antarctic debris-covered glaciers

    Science.gov (United States)

    Mackay, Sean L.; Marchant, David R.

    2017-02-01

    The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ~220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change.

  17. Teaching climate change: A 16-year record of introducing undergraduates to the fundamentals of the climate system and its complexities

    Science.gov (United States)

    Winckler, G.; Pfirman, S. L.; Hays, J. D.; Schlosser, P.; Ting, M.

    2011-12-01

    Responding to climate change challenges in the near and far future, will require a wide range of knowledge, skills and a sense of the complexities involved. Since 1995, Columbia University and Barnard College have offered an undergraduate class that strives to provide students with some of these skills. The 'Climate System' course is a component of the three-part 'Earth Environmental Systems' series and provides the fundamentals needed for understanding the Earth's climate system and its variability. Being designed both for science majors and non-science majors, the emphasis of the course is on basic physical explanations, rather than mathematical derivations of the laws that govern the climate system. The course includes lectures, labs and discussion. Laboratory exercises primarily explore the climate system using global datasets, augmented by hands-on activities. Course materials are available for public use at http://eesc.columbia.edu/courses/ees/climate/camel_modules/ and http://ncseonline.org/climate/cms.cfm?id=3783. In this presentation we discuss the experiences, challenges and future demands of conveying the science of the Earth's Climate System and the risks facing the planet to a wide spectrum of undergraduate students, many of them without a background in the sciences. Using evaluation data we reflect how the course, the students, and the faculty have evolved over the past 16 years as the earth warmed, pressures for adaptation planning and mitigation measures increased, and public discourse became increasingly polarized.

  18. 18 Ka BP records of climatic changes, Bay of Bengal: Isotopic and sedimentological evidences

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.; Suneethi, J.

    arid climate between 18 and 15 14C Ka BP, a variable climate between 15 and 13 Ka BP, and again an arid climate at 12.5 Ka BP. The negative d18O, reduced C/I and higher smectite document a humid phase culminating at 12 Ka BP. Arid climate phases...

  19. Annually resolved lake and shallow marine sediment records of global climate change of the past 16,000 years

    Science.gov (United States)

    Haug, G. H.; Brauer, A.; Yancheva, G.; Dulski, P.; Negendank, J. F.; Peterson, L. C.; Sigman, D. M.

    2007-12-01

    In the sediments of lake Huguang Maar in coastal southeast China, the titanium content and redox-sensitive magnetic properties record the strength of winter monsoon winds at subdecadal to annual resolution over the last 16 thousand years. The record indicates a stronger winter monsoon prior to the Bølling-Allerød warming, during the Younger Dryas, and during the middle and late Holocene, when cave stalagmite oxygen isotope data indicate a weaker summer monsoon. The anti-correlation between winter and summer monsoon strength is best explained by migrations in the ITCZ that occurred simultaneously in central America and Africa. Drought associated with southward ITCZ migration may have played a role in the termination of several Chinese dynasties. A remarkable similarity of ITCZ migration in east Asia and the Americas from 700 to 900 AD raises the possibility that the coincident declines of the important Tang Dynasty in China and the Classic Maya in Central America were catalyzed by the same ITCZ migrations. The mechanisms behind these decadal-scale ITCZ-monsoon swings can be further exoplored at major climate transitions such as the onset of Younger Dryas cooling at ~12.7 ka, one of the most abrupt climate changes observed in ice core, lake and marine records in the North Atlantic realm and much of the Northern Hemisphere. Annually laminated lake sediments ideally record the dynamics of abrupt climate changes since seasonal deposition immediately responds to climate and varve counts accurately estimate the time of change. We report new sub-annual geochemical and varve microfacies data from a lake in Western Germany, which provides one of the best-dated records currently available for this climate transition, which we compare to the Cariaco Basin and Lake Huguang Maar records. The Lake Meerfelder Maar record indicates an abrupt increase in storminess, occurring from one year to the next at 12,678 ka BP, coincident with other observed climate changes in the region

  20. Radiolaria and pollen records from 0 to 50 ka at ODP Site 1233: Continental and marine climate records from the Southeast Pacific

    Science.gov (United States)

    Pisias, N.G.; Heusser, L.; Heusser, C.; Hostetler, S.W.; Mix, A.C.; Weber, M.

    2006-01-01

    Site 1233 drilled during Leg 202 of the Ocean Drilling Program provides a detailed record of marine and continental climate change in the Southeast Pacific and South American continent. Splits from over 500 samples taken at 20 cm intervals for quantitative analysis of radiolarian and pollen populations yield a temporal resolution of 200-400 years. In each sample, 39 pollen taxa and 40 radiolarian species and genera were evaluated. Age control is provided by 25 AMS 14C dates [Lamy, F., Kaiser, J., Ninnemann, U., Hebbeln, D., Arz, H.W., Stoner, J., 2004. Science 304, 1959-1962]. Multivariate statistical analyses of these data allow us to conclude the following: (1) During the past 50 ka, the region of the central Chile coast is not directly influenced by polar water from the Antarctic region. (2) Changes in ocean conditions off central Chile during this time interval primarily reflect north-south shifts in the position of the South Pacific transition zone. (3) Changes in Chilean vegetation reflect comparable latitudinal shifts in precipitation and the position of the southern westerlies. (4) The first canonical variate of radiolarian and pollen records extracted from Site 1233 are remarkably similar to each other as well as to temperature records from the Antarctic, which suggests that marine and continental climate variability in the region is tightly coupled at periods longer than 3000 years. (5) The phase coupling of these climate records, which lead variations of continental erosion based on iron abundance at the same site, are consistent with a hypothesis that erosion is linked to relatively long (i.e, few thousand years) response times of the Patagonian ice sheet, and thus is not a direct indicator of regional climate. ?? 2005 Elsevier Ltd. All rights reserved.

  1. High-resolution conodont oxygen isotope record of Ordovician climate change

    Science.gov (United States)

    Chen, J.; Chen, Z.; Algeo, T. J.

    2013-12-01

    The Ordovician Period was characterized by several major events, including a prolonged 'super greenhouse' during the Early Ordovician, the 'Great Ordovician Biodiversification Event (GOBE)' of the Middle and early Late Ordovician, and the Hirnantian ice age and mass extinction of the latest Ordovician (Webby et al., 2004, The Great Ordovician Biodiversification Event, Columbia University Press). The cause of the rapid diversification of marine invertebrates during the GOBE is not clear, however, and several scenarios have been proposed including widespread development of shallow cratonic seas, strong magmatic and tectonic activity, and climate moderation. In order to investigate relationships between climate change and marine ecosystem evolution during the Ordovician, we measured the oxygen isotopic composition of single coniform conodonts using a Cameca secondary ion mass spectrometer. Our δ18O profile shows a shift at the Early/Middle Ordovician transition that is indicative of a rapid 6 to 8 °C cooling. This cooling event marks the termination of the Early Ordovician 'super greenhouse' and may have established cooler tropical seawater temperatures that were more favorable for invertebrate animals, setting the stage for the GOBE. Additional cooling episodes occurred during the early Sandbian, early Katian, and Hirnantian, the last culminating in a short-lived (extinction. Our results differ from those of Trotter et al. (2008, 'Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry,' Science 321:550-554). Instead of a slow, protracted cooling through the Early and Middle Ordovician, our high-resolution record shows that cooling occurred in several discrete steps, with the largest step being at the Early/Middle Ordovician transition.

  2. Modeling the climatic implications of the Guliya δ18O record during the past 130 ka

    Directory of Open Access Journals (Sweden)

    X. Zhou

    2012-05-01

    Full Text Available Using an intermediate-complexity UVic Earth System Climate Model (UVic Model, the geographical and seasonal implications and an indicative sense of the historical climate found in the δ18O record of the Guliya ice core (hereinafter, the Guliya δ18O are investigated under time-dependent orbital forcing with an acceleration factor of 100 over the past 130 ka. The results reveal that the simulated late-summer (August–September Guliya surface air temperature (SAT reproduces the 23-ka precession and 43-ka obliquity cycles in the Guliya δ18O. Furthermore, the Guliya δ18O is significantly correlated with the SAT over the Northern Hemisphere (NH, which suggests the Guliya δ18O is an indicator of the late-summer SAT in the NH. Corresponding to the warm and cold phases of the precession cycle in the Guliya temperature, there are two anomalous patterns in the SAT and sea surface temperature (SST fields. The first anomalous pattern shows an increase in the SAT (SST toward the Arctic, possibly associated with the joint effect of the precession and obliquity cycles, and the second anomalous pattern shows an increase in the SAT (SST toward the equator, possibly due to the influence of the precession cycle. Additionally, the summer (winter Guliya and NH temperatures are higher (lower in the warm phases of Guliya late-summer SAT than in the cold phases. Furthermore, the Guliya SAT is closely related to the North Atlantic SST, in which the Guliya precipitation may act as a "bridge" linking the Guliya SAT and the North Atlantic SST.

  3. A long-term and reproducible passive microwave sea ice concentration data record for climate studies and monitoring

    Directory of Open Access Journals (Sweden)

    G. Peng

    2013-05-01

    Full Text Available A long-term, consistent, and reproducible satellite-based passive microwave sea ice concentration climate data record (CDR is available for climate studies, monitoring, and model validation with an initial operation capability (IOC. The daily and monthly sea ice concentration data are on the National Snow and Ice Data Center (NSIDC polar stereographic grid with nominal 25 × 25 km grid cells in both the Southern and Northern Hemisphere Polar Regions from 9 July 1987 to 31 December 2007 with an update through 2011 underway. The data files are available in the NetCDF data format at http://nsidc.org/data/g02202.html and archived by the National Oceanic and Atmospheric Administration (NOAA's National Climatic Data Center (NCDC under the satellite climate data record program (http://www.ncdc.noaa.gov/cdr/operationalcdrs.html. The description and basic characteristics of the NOAA/NSIDC passive microwave sea ice concentration CDR are presented here. The CDR provides similar spatial and temporal variability as the heritage products to the user communities with the additional documentation, traceability, and reproducibility that meet current standards and guidelines for climate data records. The dataset along with detailed data processing steps and error source information can be found at: doi:10.7265/N5B56GN3.

  4. A Long-Term and Reproducible Passive Microwave Sea Ice Concentration Data Record for Climate Studies and Monitoring

    Science.gov (United States)

    Peng, G.; Meier, W. N.; Scott, D. J.; Savoie, M. H.

    2013-01-01

    A long-term, consistent, and reproducible satellite-based passive microwave sea ice concentration climate data record (CDR) is available for climate studies, monitoring, and model validation with an initial operation capability (IOC). The daily and monthly sea ice concentration data are on the National Snow and Ice Data Center (NSIDC) polar stereographic grid with nominal 25 km × 25 km grid cells in both the Southern and Northern Hemisphere polar regions from 9 July 1987 to 31 December 2007. The data files are available in the NetCDF data format at http://nsidc.org/data/g02202.html and archived by the National Climatic Data Center (NCDC) of the National Oceanic and Atmospheric Administration (NOAA) under the satellite climate data record program (http://www.ncdc.noaa.gov/cdr/operationalcdrs.html). The description and basic characteristics of the NOAA/NSIDC passive microwave sea ice concentration CDR are presented here. The CDR provides similar spatial and temporal variability as the heritage products to the user communities with the additional documentation, traceability, and reproducibility that meet current standards and guidelines for climate data records. The data set, along with detailed data processing steps and error source information, can be found at http://dx.doi.org/10.7265/N5B56GN3.

  5. From MODIS to VIIRS: Steps toward continuing the dark-target aerosol climate data record

    Science.gov (United States)

    Levy, R. C.; Mattoo, S.; Liu, H.; Munchak, L. A.; Laszlo, I.; Cronk, H.

    2012-12-01

    By this fall-2012 AGU meeting, the Moderate Resolution Imaging Spectrometer (MODIS) has been flying on NASA's Terra and Aqua satellites for 13 years and 10.5 years, respectively. During this time, the MODIS Aerosol Science Team has fine-tuned the aerosol retrieval algorithms and data processing protocols, resulting in a highly robust, stable and usable aerosol product. The aerosol optical depth (AOD) product has been validated extensively, and the MODIS-retrieved environmental data record (EDR) is becoming a strong foundation for creating an aerosol climate data record (CDR). With last year's launch of the Visible and Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP, the VIIRS-derived aerosol product has been designed to continue that provided by MODIS. VIIRS and MODIS have similar orbital mechanics and provide similar spectral resolution with similar spatial resolution. At the same time, the VIIRS and MODIS aerosol algorithms have similar physical assumptions. In fact, the initial validation exercises suggest that, in general, the VIIRS aerosol product is performing well, and that the expected error for the VIIRS-derived AOD is similar to that reported by MODIS. Although VIIRS should be able to derive an aerosol product similar in quality to MODIS, can the VIIRS aerosol record be "stitched" together with the MODIS record? To answer this question, instead of qualifying how similar they are, we need to quantify how their differences can and do impact the resulting aerosol products. There are instrumental differences, such as orbit altitude (805km versus 705km), spatial resolution (375m/750m versus 250m/500m/1000m), spectral differences, and sampling differences). There are pre-processing differences (cloud masking, gas correction assumptions, pixel selection protocols). There are retrieval algorithm differences, and of course final processing and quality control differences. Although we expect that most of differences have little or no impact, some may be

  6. Preboreal climate oscillations in Europe : Wiggle-match dating and synthesis of Dutch high-resolution multi-proxy records

    NARCIS (Netherlands)

    Bos, Johanna A. A.; van Geel, Bas; van der Plicht, Johannes; Bohncke, Sjoerd J. P.

    2007-01-01

    In order to compare environmental and inferred climatic change during the Preboreal in The Netherlands, five terrestrial records were analysed. Detailed multi-proxy analyses including microfossils (e.g., pollen, spores, algae, and fungal spores), macroremains (e.g., seeds, fruits, wood, mosses, etc.

  7. NOAA Climate Data Record (CDR) of AVHRR Daily and Monthly Aerosol Optical Thickness over Global Oceans, Version 2.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) of Aerosol Optical Thickness (AOT) is derived from data taken over global oceans from the PATMOS-x AVHRR level-2b channel 1 (0.63...

  8. Amplified plant turnover in response to climate change forecast by Late Quaternary records

    DEFF Research Database (Denmark)

    Nogues, David Bravo; Veloz, S.; Holt, Benjamin George

    2016-01-01

    Conservation decisions are informed by twenty-first-century climate impact projections that typically predict high extinction risk. Conversely, the palaeorecord shows strong sensitivity of species abundances and distributions to past climate changes, but few clear instances of extinctions attribu...

  9. A singular spectrum analysis on Holocene climatic oscillation from lake sedimentary record in Minqin Basin,China

    Institute of Scientific and Technical Information of China (English)

    JIN Liya; CHEN Fahu; DING Xiaojun; ZHU Yah

    2007-01-01

    The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57'-104°57'E, 37°48'-39°17'N) in northwestern China, which has a 10 000-year-long paleo-climatic proxy record, was used to analyze the Holocene climate changes in the local region. The proxy record was established in the Sanjiaocheng (SJC), Triangle Town in Chinese, Section (103°20'25"E, 39°00'38"N),which is located at the northwestern boundary of the present Asian summer monsoon in China, and is sensitive to global environmental and climate changes. Applying singular spectrum analysis (SSA) to the TOC series, principal climatic oscillations and periodical changes were studied. The results reveal 3 major patterns of climate change regulated by reconstructed components (RCs). The first pattern is natural long-term trend of climatic change in the local area (Minqin Basin), indicating a relatively wetter stage in early Holocene (starting at 9.5 kaBP), and a relatively dryer stage with a strong lake desiccation and a declined vegetation cover in mid-Holocene (during 7-6 kaBP). From 4.0 kaBP to the present, there has been a gradually decreasing trend in the third reconstructed component (RC3) showing that the local climate changed again into a dryer stage. The second pattern shows millennial-centennial scale oscillations containing cycles of 1 600 and 800 years that have been present throughout almost the entire Holocene period of the last 10 000 years. The third pattern is a millennial-centennial scale variation with a relatively smaller amplitude and unclear cycles showing a nonlinear interaction within the earth's climate systems.

  10. Linking hydrological modeling and paleolimnological records for a better understanding of climate-hydrosphere interactions on the Tibetan Plateau

    Science.gov (United States)

    Biskop, Sophie; Fink, Manfred; Fürstenberg, Sascha; Haberzettl, Torsten; Kasper, Thomas; Frenzel, Peter

    2016-04-01

    On the Tibetan Plateau (TP), where lake monitoring data are sparse, lacustrine systems, especially terminal lakes, act as sensitive indicators of climate variability, storing climatic and environmental information within their sediments. Thus, lake sediments are important archives for the reconstruction of hydrological changes and related climate conditions on decadal to millennial time scales. From a large number of lacustrine records on the TP, high lake levels were reconstructed for the Early Holocene, which are assumed to be related to a period climatically wetter than today. This study is the first attempt to integrate such paleoclimatic evidences from Tibetan lakes into hydrological modeling attempts to establish a quantitative reconstruction of climate variations. For the large lake Tangra Yumco (southern-central Tibetan Plateau) a high lake level indicated by an erosional terrace of 181 to 183 m above the recent lake level was dated to 8.5 ka. To maintain this high stand allowing forming a distinct lake level terrace, certain climatic conditions are needed. Considering the paleo-lake extension of Tangra Yumco and nearby lake Xuru Co, the hydrological model developed and evaluated for present-day conditions was run through several scenarios of precipitation and temperature changes. The High Asia Reanalysis (HAR) atmospheric data set for the period 2001-2010 (10 km, daily resolution) served as meteorological driver for the process-oriented conceptual hydrological model built within the Jena Adaptable Modeling System. Based on inverse modeling, this study estimates the amount of precipitation and temperature to maintain a state close to equilibrium during the lake level high-stand at 8.5 ka. This study highlights the benefits of water balance simulations by combining paleolake records and synthetic climates derived from atmospheric model data, in order to deepen the understanding of the response of hydrological systems to climate variability.

  11. Sequential planning of flood protection infrastructure under limited historic flood record and climate change uncertainty

    Science.gov (United States)

    Dittes, Beatrice; Špačková, Olga; Straub, Daniel

    2017-04-01

    Flood protection is often designed to safeguard people and property following regulations and standards, which specify a target design flood protection level, such as the 100-year flood level prescribed in Germany (DWA, 2011). In practice, the magnitude of such an event is only known within a range of uncertainty, which is caused by limited historic records and uncertain climate change impacts, among other factors (Hall & Solomatine, 2008). As more observations and improved climate projections become available in the future, the design flood estimate changes and the capacity of the flood protection may be deemed insufficient at a future point in time. This problem can be mitigated by the implementation of flexible flood protection systems (that can easily be adjusted in the future) and/or by adding an additional reserve to the flood protection, i.e. by applying a safety factor to the design. But how high should such a safety factor be? And how much should the decision maker be willing to pay to make the system flexible, i.e. what is the Value of Flexibility (Špačková & Straub, 2017)? We propose a decision model that identifies cost-optimal decisions on flood protection capacity in the face of uncertainty (Dittes et al. 2017). It considers sequential adjustments of the protection system during its lifetime, taking into account its flexibility. The proposed framework is based on pre-posterior Bayesian decision analysis, using Decision Trees and Markov Decision Processes, and is fully quantitative. It can include a wide range of uncertainty components such as uncertainty associated with limited historic record or uncertain climate or socio-economic change. It is shown that since flexible systems are less costly to adjust when flood estimates are changing, they justify initially lower safety factors. Investigation on the Value of Flexibility (VoF) demonstrates that VoF depends on the type and degree of uncertainty, on the learning effect (i.e. kind and quality of

  12. What climate information is recorded in stable isotope ratios of wood lignin methoxyl groups?

    Science.gov (United States)

    Greule, Markus; Keppler, Frank

    2010-05-01

    The stable isotope composition of the bioelements C, O, H and N in plant organic matter is known to be a very powerful for various environmental impacts. Particularly tree rings are suitable for this analysis because they exhibit a "climate archive" with a yearly or even biannual resolution. One of the most determined wood compounds is cellulose which amongst others is used to reconstruct the temperature due to measurement of stable hydrogen and oxygen isotopes. Therefore cellulose is converted into cellulose nitrate to eliminate the exchangeable hydroxyl hydrogen or equilibration methods are used. However, a general problem associated with the determination of the stable hydrogen values of marker compounds for the study of climate and environmental conditions is the isolation of the pure compound for analysis by isotope ratio mass spectrometry. Exploitation of components of wood as markers, in particular, has been restricted by the very labour intensive and time consuming preparation of samples (e.g. cellulose nitrate). An alternative way to record climate information from tree rings was recently proposed by Keppler et al. (2007) who measured the stable hydrogen values of methoxyl groups in wood. Lignin methoxyl groups are considered to be stable, i.e. the hydrogen atoms of the methoxyl moiety do not exchange with those of plant water during ongoing metabolic reactions in the plant. Thus the initial deuterium content of the methoxyl groups of lignin in woody tissue at formation is retained throughout the lifetime of the tree and in preserved tissue. The methoxyl content of lignin in wood is usually determined by the Zeisel method (Zeisel, 1885) - the reaction between methyl ethers and hydroiodic acid to form methyl iodide. Exploiting this reaction for the measurement of stable hydrogen values of lignin methoxyl groups ensures that during the entire analytical procedure the isotope signal is preserved since no isotopic exchange occurs between the methyl groups and

  13. Detrital cave sediments record Late Quaternary hydrologic and climatic variability in northwestern Florida, USA

    Science.gov (United States)

    Winkler, Tyler S.; van Hengstum, Peter J.; Horgan, Meghan C.; Donnelly, Jeffrey P.; Reibenspies, Joseph H.

    2016-04-01

    Detrital sediment in Florida's (USA) submerged cave systems may preserve records of regional climate and hydrologic variability. However, the basic sedimentology, mineralogy, stratigraphic variability, and emplacement history of the successions in Florida's submerged caves remains poorly understood. Here we present stratigraphic, mineralogical, and elemental data on sediment cores from two phreatic cave systems in northwestern Florida (USA), on the Dougherty Karst Plain: Hole in the Wall Cave (HITW) and Twin Cave. Water flowing through these caves is subsurface flow in the Apalachicola River drainage basin, and the caves are located just downstream from Jackson Blue (1st magnitude spring, > 2.8 m3 s- 1 discharge). Sedimentation in these caves is dominated by three primary sedimentary styles: (i) ferromanganese deposits dominate the basal recovered stratigraphy, which pass upsection into (ii) poorly sorted carbonate sediment, and finally into (iii) fine-grained organic matter (gyttja) deposits. Resolving the emplacement history of the lower stratigraphic units was hampered by a lack of suitable material for radiocarbon dating, but the upper organic-rich deposits have a punctuated depositional history beginning in the earliest Holocene. For example, gyttja primarily accumulated in HITW and Twin Caves from ~ 5500 to 3500 cal yr. BP, which coincides with regional evidence for water-table rise of the Upper Floridian Aquifer associated with relative sea-level rise in the Gulf of Mexico, and evidence for invigorated drainage through the Apalachicola River drainage basin. Gyttja sediments were also deposited in one of the caves during the Bølling/Allerød climate oscillation. Biologically, these results indicate that some Floridian aquatic cave (stygobitic) ecosystems presently receive minimal organic matter supply in comparison to prehistoric intervals. The pre-Holocene poorly sorted carbonate sediment contains abundant invertebrate fossils, and likely documents a period

  14. Post-glacial regional climate variability along the East Antarctic coastal margin-Evidence from shallow marine and coastal terrestrial records

    NARCIS (Netherlands)

    Verleyen, E.; Hodgson, D.A.; Sabbe, K.; Cremer, H.; Emslie, S.D.; Gibson, J.; Hall, B.; Imura, S.; Kudoh, S.; Marshall, G.J.; McMinn, A.; Melles, M.; Newman, L.; Roberts, D.; Roberts, S.J.; Singh, S.M.; Sterken, M.; Tavernier, I.; Verkulich, S.; Vyver, E.V. de; Nieuwenhuyze, W. van; Wagner, B.; Vyverman, W.

    2011-01-01

    We review the post-glacial climate variability along the East Antarctic coastline using terrestrial and shallow marine geological records and compare these reconstructions with data from elsewhere. Nearly all East Antarctic records show a near-synchronous Early Holocene climate optimum (11.5-9 ka BP

  15. Mid-Holocene Climate Variations Recorded by Palaeolake in Marginal Area of East Asian Monsoon: A Multi-proxy Study

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Traditionally, the mid-Holocene in most parts of China was thought to be warmer with higher precipitation,resulting from a strong Asian summer monsoon. However, some recent researches have proposed a mid-Holocene drought interval of millennial-scale in East Asian monsoon margin areas. Thus whether mid-Holocene was dry or humid remains an open issue. Here, Zhuyeze palaeolake, the terminal lake of the Shiyang River Drainage lying in Asian monsoon marginal areas, was selected for reconstructing the details of climate variations during the Holocene, especially mid-Holocene,on the basis ora sedimentological analysis. Qingtu Lake (QTL) section of 6.92m depth was taken from Zhuyeze palaeolake. Multi-proxy analysis of QTL section, including grain size, carbonate, TOC, C/N and δ13C of organic matter, was used to document regional climatic changes during 9-3 cal ka B.P. The record shows a major environmental change at 9.0-7.8 cal ka B.P., attributed to a climate trend towards warmth and humidity. This event was followed by a typical regional drought event which occurred during 7.8-7.5 cal ka B.P. And a warm and humid climate prevailed from 7.5 to 5.0 cal ka B.P., attributed to the warm/humid Holocene Optimum in this region. After that, the climate gradually became drier.Moreover, comparison of the climate record from this paper with the summer insolation at 30°N indicates that the climate pattern reflecting the Asian monsoon changes was caused by insolation change.

  16. Dating of dipterocarp tree rings: establishing a record of carbon cycling and climatic change in the tropics

    CSIR Research Space (South Africa)

    Robertson, I

    2004-10-01

    Full Text Available (2004) 19(7) 657–664 Copyright � 2004 John Wiley & Sons, Ltd. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jqs.885 The dating of dipterocarp tree rings: establishing a record of carbon cycling and climatic change... demonstrates that palaeoenvironmental information can be obtained from trees growing in aseasonal environ- ments, where climatic conditions prevent the formation of well-defined annual rings. Copyright � 2004 John Wiley & Sons, Ltd. KEYWORDS: dipterocarp...

  17. Climatic and environmental changes over the last millennium recorded in the Malan ice core from the northern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    WANG Ninglian; YAO Tandong; PU Jianchen; ZHANG Yongliang; SUN Weizhen

    2006-01-01

    In this paper, climatic and environmental changes were reconstructed since 1129A.D.based on the Malan ice core from Hol Xil, the northern Tibetan Plateau. The record of δ18O in the Malan ice core indicated that the warm-season air temperature variations displayed a general increase trend, the 20th-century warming was within the range of natural climate variability, and the warmest century was the 17th century while the warmest decade was the 1610s, over the entire study period. The "Medieval Warm Epoch" and "Little Ice Age" were also reflected by the ice core record.The dust ratio in the Malan ice core is a good proxy for dust event frequency. The 870-year record of the dust ratio showed that dust events occurred much frequently in the 19th century. Comparing the variations of δ18O and the dust ratio, it is found that there was a strong negative correlation between them on the time scales of 101 - 102 years. By analyses of all the climatic records of ice cores and tree rings from the northern Tibetan Plateau, it was revealed that dust events were more frequent in the cold and dry periods than in the warm and wet periods.

  18. An ice core record of near-synchronous global climate changes at the Bølling transition

    Science.gov (United States)

    Rosen, Julia L.; Brook, Edward J.; Severinghaus, Jeffrey P.; Blunier, Thomas; Mitchell, Logan E.; Lee, James E.; Edwards, Jon S.; Gkinis, Vasileios

    2014-06-01

    The abrupt warming that initiated the Bølling-Allerød interstadial was the penultimate warming in a series of climate variations known as Dansgaard-Oeschger events. Despite the clear expression of this transition in numerous palaeoclimate records, the relative timing of climate shifts in different regions of the world and their causes are subject to debate. Here we explore the phasing of global climate change at the onset of the Bølling-Allerød using air preserved in bubbles in the North Greenland Eemian ice core. Specifically, we measured methane concentrations, which act as a proxy for low-latitude climate, and the 15N/14N ratio of N2, which reflects Greenland surface temperature, over the same interval of time. We use an atmospheric box model and a firn air model to account for potential uncertainties in the data, and find that changes in Greenland temperature and atmospheric methane emissions at the Bølling onset occurred essentially synchronously, with temperature leading by 4.5 years. We cannot exclude the possibility that tropical climate could lag changing methane concentrations by up to several decades, if the initial methane rise came from boreal sources alone. However, because even boreal methane-producing regions lie far from Greenland, we conclude that the mechanism that drove abrupt change at this time must be capable of rapidly transmitting climate changes across the globe.

  19. Late Holocene Lacustrine Records of Climate and Vegetation Change From Southernmost South America

    Science.gov (United States)

    Moy, C. M.; Dunbar, R. B.; Francois, J.; Moreno, P. I.; Villa Martínez, R.

    2006-12-01

    The westerly wind field is one of the most prominent atmospheric circulation features in the Southern Hemisphere and has a major impact on the climate of southern South America as well as Southern Ocean hydrography. Southernmost South America is well-located to investigate past changes in the westerly winds because regional precipitation variability is controlled by the location and intensity of the wind field and it is the only landmass to extend within the core of the westerlies. Here we present late Holocene lacustrine records of climate change related to the westerlies from southern Patagonia, Chile. We focus on Lago Guanaco, a small hydrologically closed-basin lake in Southern Patagonia, and use stable isotope and pollen data from this site and three additional lakes in order to reconstruct changes in moisture balance related to the westerlies. Lago Guanaco (51°S, 72°W) is located close to the Nothofagus forest-Patagonian Steppe transition in the eastern region of Parque Nacional Torres del Paine. The location and composition of this important biological discontinuity is highly sensitive to the W-E precipitation gradient throughout Patagonia. The 4.75 m sediment core we obtained from the center of the lake has high concentrations of organic mater in addition to ostracodes and bivalves, which are relatively rare in Chilean Patagonia. Eleven AMS radiocarbon dates on organic and carbonate fractions indicate that the record spans the last ~14,400 cal yr BP and modern dates from core tops suggest little influence by old carbon sources. Changes in moisture balance and forest density/proximity are reflected in downcore variations in δ18Obivalve and δ18Oostracode, the Nothofagus/Poaceae paleovegetation index, and the C/N ratio of bulk decalcified organic matter. Combined, these variables document changes in the isotopic composition of the lake water, which largely reflect the isotopic composition of precipitation and the influence of evaporation, as well as shifts

  20. A comparison of the climates of the Medieval Climate Anomaly, Little Ice Age, and Current Warm Period reconstructed using coral records from the northern South China Sea

    Science.gov (United States)

    Deng, Wenfeng; Liu, Xi; Chen, Xuefei; Wei, Gangjian; Zeng, Ti; Xie, Luhua; Zhao, Jian-xin

    2017-01-01

    For the global oceans, the characteristics of high-resolution climate changes during the last millennium remain uncertain because of the limited availability of proxy data. This study reconstructs climate conditions using annually resolved coral records from the South China Sea (SCS) to provide new insights into climate change over the last millennium. The results indicate that the climate of the Medieval Climate Anomaly (MCA, AD 900-1300) was similar to that of the Current Warm Period (CWP, AD 1850-present), which contradicts previous studies. The similar warmth levels for the MCA and CWP have also been recorded in the Makassar Strait of Indonesia, which suggests that the MCA was not warmer than the CWP in the western Pacific and that this may not have been a globally uniform change. Hydrological conditions were drier/saltier during the MCA and similar to those of the CWP. The drier/saltier MCA and CWP in the western Pacific may be associated with the reduced precipitation caused by variations in the Pacific Walker Circulation. As for the Little Ice Age (LIA, AD 1550-1850), the results from this study, together with previous data from the Makassar Strait, indicate a cold and wet period compared with the CWP and the MCA in the western Pacific. The cold LIA period agrees with the timing of the Maunder sunspot minimum and is therefore associated with low solar activity. The fresher/wetter LIA in the western Pacific may have been caused by the synchronized retreat of both the East Asian Summer Monsoon and the Australian Monsoon.

  1. Peeking Under the Ice… Literally: Records of Arctic Climate Change from Radiocarbon Dating Moss Emerging from Beneath Retreating Glaciers

    Science.gov (United States)

    Briner, J. P.; Schweinsberg, A.; Miller, G. H.; Lifton, N. A.; Beel, C. R.; Bennike, O.

    2014-12-01

    Dramatic changes are taking place throughout the Arctic. Many glaciers have already melted away completely, and most others are well on their way as rising snowline elevations promise continued glacier retreat. Emerging from beneath retreating glacier margins is a landscape rich in information about past climate and glacier changes. Within newly exposed bedrock is an inventory of cosmogenic nuclides that archive past ice cover timing and duration. Lake basins re-appearing due to retreating ice preserve sediment archives that tell of cooling climate and advancing ice. And ancient surfaces vegetated with tundra communities that have long been entombed beneath frozen-bedded ice caps are now being revealed for the first time in millennia. This presentation will focus on the climate and glacier record derived from radiocarbon dating of in situ moss recently exhumed from retreating local ice cap margins on western Greenland. Dozens of radiocarbon ages from moss group into several distinct modes, which are interpreted as discrete times of persistent summer cooling and resultant glacier expansion. The data reveal a pattern of glacier expansion beginning ~5000 years ago, followed by periods of glacier growth around 3500 and 1500 years ago. Because these times of glacier expansion are recorded at many sites in western Greenland and elsewhere in the Arctic, they are interpreted as times of step-wise summer cooling events during the Holocene. These non-linear climate changes may be a result of feedbacks that amplify linear insolation forcing of Holocene climate. In addition to these insights into the Arctic climate system, the antiquity of many radiocarbon ages of ice-killed moss indicate that many arctic surfaces are being re-exposed for the first time in millennia due to retreating ice, emphasizing the unprecedented nature of current summer warming.

  2. A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic: refining the pattern of climate modes by means of cluster analysis

    Directory of Open Access Journals (Sweden)

    U. Frank

    2013-07-01

    Full Text Available Rock magnetic, biochemical and inorganic records of the sediment cores PG1351 and Lz1024 from Lake El'gygytgyn, Chukotka peninsula, Far East Russian Arctic, were subject to a hierarchical agglomerative cluster analysis in order to refine and extend the pattern of climate modes as defined by Melles et al. (2007. Cluster analysis of the data obtained from both cores yielded similar results, differentiating clearly between the four climate modes warm, peak warm, cold and dry, and cold and moist. In addition, two transitional phases were identified, representing the early stages of a cold phase and slightly colder conditions during a warm phase. The statistical approach can thus be used to resolve gradual changes in the sedimentary units as an indicator of available oxygen in the hypolimnion in greater detail. Based upon cluster analyses on core Lz1024, the published succession of climate modes in core PG1351, covering the last 250 ka, was modified and extended back to 350 ka. Comparison to the marine oxygen isotope (δ18O stack LR04 (Lisiecki and Raymo, 2005 and the summer insolation at 67.5° N, with the extended Lake El'gygytgyn parameter records of magnetic susceptibility (κLF, total organic carbon content (TOC and the chemical index of alteration (CIA; Minyuk et al., 2007, revealed that all stages back to marine isotope stage (MIS 10 and most of the substages are clearly reflected in the pattern derived from the cluster analysis.

  3. FUSION OF ACTIVE AND PASSIVE MICROWAVE OBSERVATIONS TO CREATE AN ESSENTIAL CLIMATE VARIABLE DATA RECORD ON SOIL MOISTURE

    Directory of Open Access Journals (Sweden)

    W. Wagner

    2012-07-01

    Full Text Available Soil moisture was recently included in the list of Essential Climate Variables (ECVs that are deemed essential for IPCC (Intergovernmental Panel on Climate Change and UNFCCC (United Nations Framework Convention on Climate Change needs and considered feasible for global observation. ECVs data records should be as long, complete and consistent as possible, and in the case of soil moisture this means that the data record shall be based on multiple data sources, including but not limited to active (scatterometer and passive (radiometer microwave observations acquired preferably in the low-frequency microwave range. Among the list of sensors that can be used for this task are the C-band scatterometers on board of the ERS and METOP satellites and the multi-frequency radiometers SMMR, SSM/I, TMI, AMSR-E, and Windsat. Together, these sensors already cover a time period of more than 30 years and the question is how can observations acquired by these sensors be merged to create one consistent data record? This paper discusses on a high-level possible approaches for fusing the individual satellite data. It is argued that the best possible approach for the fusion of the different satellite data sets is to merge Level 2 soil moisture data derived from the individual satellite data records. This approach has already been demonstrated within the WACMOS project (http://wacmos.itc.nl/ funded by European Space Agency (ESA and will be further improved within the Climate Change Initiative (CCI programme of ESA (http://www.esa-cci.org/.

  4. Spatiotemporal climatic, hydrological, and environmental variations based on records of annually laminated lake sediments from northern Poland

    Science.gov (United States)

    Tylmann, W.; Blanke, L.; Kinder, M.; Loewe, T.; Mayr, C.; Ohlendorf, C.; Zolitschka, B.

    2009-12-01

    In northern Poland there is the unique opportunity to compare varved lake sediment records with distinct climatic trends along a 700 km long W-E transect. Annually laminated Holocene sediment sequences from Lake Lubinskie, Lake Suminko, Lake Lazduny, and Lake Szurpily were cored for high-resolution multiproxy climate and environmental reconstruction in the framework of the Polish-German project “Northern Polish Lake Research” (NORPOLAR). First results from a 139 cm long gravity core of Lake Lazduny (53°51.4’N, 21°57.3’E) document deposition of an organic (mean organic matter: 13.9%; mean biogenic opal: 9.8%) and highly carbonaceous gyttja (mean calcite content: 61.6%). The finely laminated sediment consists of biochemical varves. Pale spring/summer layers composed of autochthonous carbonates alternate with dark fall/winter layers made of organic and minerogenic detritus. The established chronology for the last 1500 calendar-years is based on thin section analysis supported by independent radiometric dating (C-14, Pb-210). Sedimentological, geochemical and stable isotope analyses were carried out with a decadal temporal resolution. Additionally, non-destructive and high-resolution XRF scanning data reveal a rhythmic variation in the Ca content that reflects seasonal calcite deposition. Redox-sensitive elements like Fe, Mn and S are interpreted to be the response to mean winter temperatures: colder winter temperatures → extended lake ice cover → intensification of meromixis → increased Fe/Mn ratio. In turn, these parameters can be linked to NAO (North Atlantic Oscillation) variability, because a negative NAO is related to colder and drier conditions in northeastern Europe. Climate variability is also mirrored by the δ13C record of the endogenic calcite fraction. In mid-latitude lakes calcite precipitation is dominated by productivity-controlled consumption of the dissolved inorganic carbon (DIC) pool. Thus the δ13C record potentially provides a

  5. Plant-wax D/H ratios in the southern European Alps record multiple aspects of climate variability

    Science.gov (United States)

    Wirth, Stefanie B.; Sessions, Alex L.

    2016-09-01

    We present a Younger Dryas-Holocene record of the hydrogen isotopic composition of sedimentary plant waxes (δDwax) from the southern European Alps (Lake Ghirla, N-Italy) to investigate its sensitivity to climatic forcing variations in this mid-latitude region (45°N). A modern altitudinal transect of δD values of river water and leaf waxes in the Lake Ghirla catchment is used to test present-day climate sensitivity of δDwax. While we find that altitudinal effects on δDwax are minor at our study site, temperature, precipitation amount, and evapotranspiration all appear to influence δDwax to varying extents. In the lake-sediment record, δDwax values vary between -134 and -180‰ over the past 13 kyr. The long-term Holocene pattern of δDwax parallels the trend of decreasing temperature and is thus likely forced by the decline of northern hemisphere summer insolation. Shorter-term fluctuations, in contrast, may reflect both temperature and moisture-source changes. During the cool Younger Dryas and Little Ice Age (LIA) periods we observe unexpectedly high δDwax values relative to those before and after. We suggest that a change towards a more D-enriched moisture source is required during these intervals. In fact, a shift from northern N-Atlantic to southern N-Atlantic/western Mediterranean Sea sources would be consistent with a southward migration of the Westerlies with climate cooling. Prominent δDwax fluctuations in the early and middle Holocene are negative and potentially associated with temperature declines. In the late Holocene (changes on δDwax variation. In addition to isotopic fractionations of the hydrological cycle, changes in vegetation composition, in the length of the growing season, and in snowfall amount provide additional potential sources of variability, although we cannot yet quantitatively assess these in the paleo-record. We conclude that while our δDwax record from the Alps does contain climatic information, it is a complicated record

  6. Evolution of vegetation and climate since the last glacial maximum recorded at Dahu peat site, South China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Sporopollen analysis on a 346 cm peat record at Dahu, Jiangxi, chronologically constrained by 16 AMS 14C datings, provides an opportunity to reconstruct the vegetation evolution stages responding to cli-mate change in South China since the last glacial maximum. The result shows that during 18330-15630 cal a B.P., broad-leaved forest dominated the area, corresponding to mild, cool and fairly humid climate. At the interval of 15630-11600 cal a B.P., several evergreen broad-leaved species appeared within the broad-leaved forest, indicating moderate and humid condition. During early Holocene, broad-leaved evergreen forest community was constructed as Castanopsis/Lithorcarpus principally developed, suggesting a warm and humid scenario until 6000 cal a B. P. Since 6000 cal a B. P., abrupt forest deterioration happened with an contemporary increase of fern and herb communities, repre-senting a turnover to relatively cool and dry condition and as well, possible impact from human activi-ties. Meanwhile, several relatively cool and dry events can be identified in the sporopollen record, they can be correlated to the North Atlantic Heinrich event, YD and Holocene millennial-scale oscillations, implying that the low latitude climate was coupled with high latitude influences. Moreover, the varia-tions of temperature and humidity since LGM at Dahu were much smaller when compared with the re-cords in north monsoonal China.

  7. Evolution of vegetation and climate since the last glacial maximum recorded at Dahu peat site,South China

    Institute of Scientific and Technical Information of China (English)

    XIAO JiaYi; L(U) HaiBo; ZHOU WeiJian; ZHAO ZhiJun; HAO RuiHui

    2007-01-01

    Sporopollen analysis on a 346 cm peat record at Dahu, Jiangxi, chronologically constrained by 16 AMS 14C datings, provides an opportunity to reconstruct the vegetation evolution stages responding to climate change in South China since the last glacial maximum. The result shows that during 18330-15630 cal a B.P., broad-leaved forest dominated the area, corresponding to mild, cool and fairly humid climate. At the interval of 15630-11600 cal a B.P., several evergreen broad-leaved species appeared within the broad-leaved forest, indicating moderate and humid condition. During early Holocene,broad-leaved evergreen forest community was constructed as Castanopsis/Lithorcarpus principally developed, suggesting a warm and humid scenario until 6000 cal a B. P. Since 6000 cal a B. P., abrupt forest deterioration happened with an contemporary increase of fern and herb communities, representing a turnover to relatively cool and dry condition and as well, possible impact from human activities. Meanwhile, several relatively cool and dry events can be identified in the sporopollen record, they can be correlated to the North Atlantic Heinrich event, YD and Holocene millennial-scale oscillations,implying that the low latitude climate was coupled with high latitude influences. Moreover, the variations of temperature and humidity since LGM at Dahu were much smaller when compared with the records in north monsoonal China.

  8. Holocene climate change in the Central Tibetan Plateau inferred by lacustrine sediment geochemical records

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Multi-proxies of lacustrine sediments, such as total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), hydrogen index (HI), oxygen index (OI) and stable carbon isotopic composition of organic matter (δ13Corg), were analyzed using a 7.3 m core from Zigê Tangco. The source of the organic matter in the sediment was mainly from autochthonous phytoplankton, therefore the significances of proxies can be interpreted as that high TOC, TOC/TS, HI and δ13Corg values, low TC, TIC values corresponded to warm and wet climatic condition, and vice versa. The process of climatic development in the Zigê Tangco region was hence recovered. During the early and Mid-Holocene, the climate was warm and wet and intensive cold events occurred during the periods of 8600 to 8400 cal a BP and 7400 to 7000 cal a BP. In the second half of Holocene, the climate became cold and dry gradually. The palaeoclimatic process during Holocene in Zigê Tangco region matched well with that in Co Ngoin region which is ca 40 km to the south-east. Therefore this palaeoclimatic process represents the Holocene climatic feature in the Central Tibetan Plateau which has the same pattern in the Northern Tibetan Plateau, but the time and duration of some climatic events might be different. We can conclude that in Holocene solar insolation controlled the climatic pattern on the central Tibetan Plateau.

  9. Late Quaternary climatic events and sea-level changes recorded by turbidite activity, Dakar Canyon, NW Africa

    Science.gov (United States)

    Pierau, Roberto; Hanebuth, Till J. J.; Krastel, Sebastian; Henrich, Rüdiger

    2010-03-01

    The relationship of sea-level changes and short-term climatic changes with turbidite deposition is poorly documented, although the mechanisms of gravity-driven sediment transport in submarine canyons during sea-level changes have been reported from many regions. This study focuses on the activity of the Dakar Canyon off southern Senegal in response to major glacial/interglacial sea-level shifts and variability in the NW-African continental climate. The sedimentary record from the canyon allows us to determine the timing of turbidite events and, on the basis of XRF-scanning element data, we have identified the climate signal at a sub-millennial time scale from the surrounding hemipelagic sediments. Over the late Quaternary the highest frequency in turbidite activity in the Dakar Canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea-level rise. However, episodic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly, with evidence for higher dust supply over NW Africa which has fed turbidity currents. Increased aridity and enhanced wind strength in the southern Saharan-Sahelian zone may have provided a source for this dust.

  10. Holocene Abrupt Climate Shifts and Mid-Holocene Drought Intervals Recorded in Barkol Lake of Northern Xinjiang of China

    Institute of Scientific and Technical Information of China (English)

    XUE Jibin; ZHONG Wei; ZHAO Yinjuan; PENG Xiaoying

    2008-01-01

    Study results in this paper have indicated that the Holocene climate in Xinjiang, Northwestern China hasbeen alternating between wet and dry conditions, and was punctuated with a series of abrupt climate shifts. A sedimentcore taken from Barkol Lake in the northern Xinjiang of Northwest China was analyzed at 1 cm interval for grain-sizedistribution. Abrupt climate shifts revealed by the grain-size proxy occurred at ca 1.4, 3.0, 4.3, 5.6, 8.0 cal kyr B.P.,which were well correlated to both the abrupt shifts recorded in the North Atlantic Ocean (NAO) and the Holocene seasurface temperature (SST) cooling events in the Arabian Ocean. The correlation indicated that the climatic changes inthe extreme arid Northwest China were associated with the NAO, probably via the North Atlantic Oscillation-affectedwesterly winds. The strength and position of westerly winds probably modulated the Siberian-Mongolian high-pressure system (winter monsoon), and played an important role in climate change of Northwest China. Moreover, anevident drought interval during the middle Holocene was also revealed by grain-size proxy.

  11. Peat record of climate change for the last 3000 years in Yangmu, Mishan region of Sanjiang Plain

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Five pollen zones are identified in Yangmu peatland of Mishan region located at 45°34'N,132°23'E through sporo-pollen analysis. The changing process of paleovegetation and paleoclimate was obtained. Warm-inclined broad-leaved forest predominated in the environment of warm climate with a little dry 3400 yr BP. Deciduous broad-leaved and coniferous mixed forests predominated, in which Pinus, Picea and Abies were main species, together with wet meadow in the environment of cool and humid climate during 3400-1940 yr BP. Deciduous broad-leaved and coniferous mixed forests predominated in the dry and warm climate environment 1940-1090 yr BP. Broad-leaved forest was predominant, and the climate was warm and humid 1090-545 yr BP. Marsh meadow predominated when the climate changed to cool and dry 545 yr BP. The composition of the upper part of the 143-125 cm of the peat profile presented the cold period in the early Christian era through mutual identification between the records of historical material such as spores and pollens,susceptibility, organic matter and archaeological studies. The composition of the parts of 125-85 cm and 85-38 cm presented the warm climate in the Northern and Southern Dynasty and Sui and Tang dynasties. Since 3400 yr BP because of the frequent human activities in Mishan region, the amount of cultural relics in the Sui and Tang dynasties increased, which indicated that the ancients took much more woods from the forests in the warm climate environment.

  12. Climate changes in East China since the Late-glacial inferred from high-resolution mountain peat humification records

    Institute of Scientific and Technical Information of China (English)

    MA ChunMei; ZHU Cheng; ZHENG ChaoGui; YIN Qian; ZHAO ZhiPing

    2009-01-01

    High-resolution peat humification records were obtained from Dajiuhu of the Shennongjia Mountains and Qianmutian of the Tianmu Mountains to study climate changes in East China. The analyses of pollen, organic matters, TOC, and Rb/Sr indicate a high degree of peat humification and thus strong decomposition of organic matter when climate was dry. Conversely, when climate was humid, the de gree of humification is low because peat was preserved in a waterlogged condition. Peat humification from Dajiuhu occurred not only during the Younger Dryas (about 11.4-12.6 cal ka BP), the Bol ling-Allerφd Warm Period (12.6-15.2 cal ka BP), and the Oldest Dryas (about 15.2-16.0 cal ka BP), but also during the early Holocene (about 11.4-9.4 cal ka BP), the 8.2 cal ka BP cold event, and the Holo cene Optimum (about 7.0-4.2 cal ka BP). Both peat humification records since nearly 5 ka BP are consistent, showing that mountain peaUand has synchronous responses to the East Asia mon soon-induced precipitation. The LOI data confirm the above observation. The monsoon precipitation since nearly 5 ka BP recorded in these two peat profiles can be divided into three phases. During 4.9 3.5 ka BP, precipitation amount was high but fluctuated greatly. During 3.5-0.9 ka BP, precipitation amount was low. During 0.9-0 ka BP, degree of humification reduced gradually, indicating the increase of monsoon precipitation. Contrast to other high-resolution records from East China monsoon region shows that the monsoon precipitation records of the two peat profiles since nearly 16 ka BP are con trolled by a common forcing mechanism of summer solar radicalization in the Northern Hemisphere.

  13. Temporal trends in West Antarctic surface mass balance: do large scale modes of climate contribute to observed records?

    Science.gov (United States)

    Carpenter, M.; Rupper, S.; Williams, J.; Burgener, L. K.; Koenig, L.; Forster, R. R.; Koutnik, M. R.; Skinner, R.; Miege, C.; Brucker, L.

    2013-12-01

    Western Antarctica has been warming significantly at a rate of 0.17× 0.06 degrees C per decade from 1957 to 2006, with the strongest warming in the winter and spring months. Annual accumulation rates in the central WAIS have been decreasing over the same time period, in spite of rising temperatures. This is somewhat unexpected, as saturation vapor pressure increases with increasing temperature. One possible explanation of this observation could be related to synoptic-scale modes of climate, principally the Southern Annular Mode (SAM) and the El Nino Southern Oscillation (ENSO). These modes of climate are known to modify the track and strength of storms seasonally, but the true extent of the influence of these modes on accumulation in central WAIS is not well known. This is due, in part, to sparse instrumental weather data which makes it difficult to understand the spatial and temporal variability of the central WAIS Surface Mass Balance (SMB). Firn cores provide an excellent temporal SMB record that can fill this data gap, but are spatially limited. The spatial limitation of individual cores can be remedied by creating a network of firn cores over a region, which overcomes small scale variability and provides a regional representation of SMB over the temporal length of the firn core records. The 2011 Satellite Era Accumulation Traverse (SEAT) adds nine new firn cores (20 m deep, spanning 2010-1981) to existing cores within the same region of the central WAIS to improve the spatial network of regional SMB measurements. SMB is reconstructed from the firn cores, and are compared to simulated accumulation from five climate models and reanalyses datasets. The combination of firn cores and simulated records are used to investigate wether SAM and ENSO significantly influence SMB in the central WAIS. The new suite of cores show a statistically significant negative trend in accumulation during the past three decades, which is consistent with results from the previous cores

  14. A 25 ky BP record of Himalayan aridity using muscovite and clays as proxy climate indicators

    Digital Repository Service at National Institute of Oceanography (India)

    Gujar, A; Chauhan, O.S.

    Based upon the temporal variations in the grain size parameters, characteristic clay minerals, their ratios and detrital muscovite content in a isotopically dated turbidity free core from hemipelagic environment. (2713 m water depth), the climatic...

  15. Orbit-related long-term climate cycles revealed in a 12-Myr continental record from Lake Baikal.

    Science.gov (United States)

    Kashiwaya, K; Ochiai, S; Sakai, H; Kawai, T

    2001-03-01

    Quaternary records of climate change from terrestrial sources, such as lake sediments and aeolian sediments, in general agree well with marine records. But continuous records that cover more than the past one million years were essentially unavailable until recently, when the high-sedimentation-rate site of Lake Baikal was exploited. Because of its location in the middle latitudes, Lake Baikal is highly sensitive to insolation changes and the entire lake remained uncovered by ice sheets throughout the Pleistocene epoch, making it a valuable archive for past climate. Here we examine long sediment cores from Lake Baikal that cover the past 12 million years. Our record reveals a gradual cooling of the Asian continental interior, with some fluctuations. Spectral analyses reveal periods of about 400 kyr, 600 kyr and 1,000 kyr, which may correspond to Milankovitch periods (reflecting orbital cycles). Our results indicate that changes in insolation were closely related to long-term environmental variations in the deep continental interior, over the past 12 million years.

  16. Climate variability in SE Europe since 1450 AD based on a varved sediment record from Etoliko Lagoon (Western Greece)

    Science.gov (United States)

    Koutsodendris, Andreas; Brauer, Achim; Reed, Jane M.; Plessen, Birgit; Friedrich, Oliver; Hennrich, Barbara; Zacharias, Ierotheos; Pross, Jörg

    2017-03-01

    To achieve deeper understanding of climate variability during the last millennium in SE Europe, we report new sedimentological and paleoecological data from Etoliko Lagoon, Western Greece. The record represents the southernmost annually laminated (i.e., varved) archive from the Balkan Peninsula spanning the Little Ice Age, allowing insights into critical time intervals of climate instability such as during the Maunder and Dalton solar minima. After developing a continuous, ca. 500-year-long varve chronology, high-resolution μ-XRF counts, stable-isotope data measured on ostracod shells, palynological (including pollen and dinoflagellate cysts), and diatom data are used to decipher the season-specific climate and ecosystem evolution at Etoliko Lagoon since 1450 AD. Our results show that the Etoliko varve record became more sensitive to climate change from 1740 AD onwards. We attribute this shift to the enhancement of primary productivity within the lagoon, which is documented by an up to threefold increase in varve thickness. This marked change in the lagoon's ecosystem was caused by: (i) increased terrestrial input of nutrients, (ii) a closer connection to the sea and human eutrophication particularly from 1850 AD onwards, and (iii) increasing summer temperatures. Integration of our data with those of previously published paleolake sediment records, tree-ring-based precipitation reconstructions, simulations of atmospheric circulation and instrumental precipitation data suggests that wet conditions in winter prevailed during 1740-1790 AD, whereas dry winters marked the periods 1790-1830 AD (Dalton Minimum) and 1830-1930 AD, the latter being sporadically interrupted by wet winters. This variability in precipitation can be explained by shifts in the large-scale atmospheric circulation patterns over the European continent that affected the Balkan Peninsula (e.g., North Atlantic Oscillation). The transition between dry and wet phases at Etoliko points to longitudinal

  17. Long-term memory: a natural mechanism for the clustering of extreme events and anomalous residual times in climate records.

    Science.gov (United States)

    Bunde, Armin; Eichner, Jan F; Kantelhardt, Jan W; Havlin, Shlomo

    2005-02-04

    We study the statistics of the return intervals between extreme events above a certain threshold in long-term persistent records. We find that the long-term memory leads (i) to a stretched exponential distribution of the return intervals, (ii) to a pronounced clustering of extreme events, and (iii) to an anomalous behavior of the mean residual time to the next event that depends on the history and increases with the elapsed time in a counterintuitive way. We present an analytical scaling approach and demonstrate that all these features can be seen in long climate records. The phenomena should also occur in heartbeat records, Internet traffic, and stock market volatility and have to be taken into account for an efficient risk evaluation.

  18. Vegetation and climatic changes during the Middle Miocene in the Wushan Basin, northeastern Tibetan Plateau: Evidence from a high-resolution palynological record

    Science.gov (United States)

    Hui, Zhengchuang; Li, Jijun; Song, Chunhui; Chang, Jing; Zhang, Jun; Liu, Jia; Liu, Shanpin; Peng, Tingjiang

    2017-10-01

    There remains no detailed record of the Middle Miocene vegetation and climatic changes which occurred in central Asia and their possible driving mechanisms. This is because there is still a lack of high resolution records. Here, we present a sporopollen record from the Wushan Basin on the northeastern Tibetan Plateau, central Asia, spanning the period ∼16.1-13.6 Ma. The sporopollen record shows that a dense mixed forest growing in rather warm and humid climatic conditions was affected by a general drying trend during the period ∼16.1-15 Ma. It demonstrates that although the climate was generally warm and humid during the Middle Miocene Climate Optimum (MMCO), it was also a time of climatic instability. The dense forest gave way to an open forest in response to a less humid climate between ∼15 and 14.4 Ma. Dense mixed forest made a return with an increasingly humid climate during ∼14.4-13.8 Ma. This vegetation and climatic succession could be associated with global cooling, or more particularly, a higher temperature rebound set against the background of a long-term cooling trend. A more open forest appearing in response to drier and colder climatic conditions dominated the study area during the ∼13.8-13.6 Ma period. This could be compared to the rapid global cooling event Mi-3b. This significant global cooling event exerted a major impact on terrestrial vegetation, climate and biota. Our high resolution sporopollen record demonstrates that global climate changes could have been the first order driving force for the Middle Miocene vegetation and climate changes seen in the Wushan Basin in central continental Asia, with the tectonic uplift of the Tibetan Plateau probably playing a subordinate role.

  19. Past climate variability between 97 and 7 ka reconstructed from a multi proxy speleothem record from Western Cuba

    Science.gov (United States)

    Winterhalder, Sophie; Scholz, Denis; Mangini, Augusto; Spötl, Christoph; Jochum, Klaus Peter; Pajón, Jesús M.

    2016-04-01

    The tropical hydrological cycle plays a key role in regulating global climate, mainly through the export of heat and moisture to higher latitudes, and is highly sensitive to climate change, for instance due to changes in the position of the Intertropical Convergence Zone (ITCZ). Previous work on Caribbean stalagmites suggests a strong connection of precipitation variability to North Atlantic (NA) sea surface temperatures on multidecadal to millenial timescales (Fensterer et al., 2012; Fensterer et al., 2013; Winter et al., 2011). Cold phases in the NA potentially lead to a southward shift of the ITCZ and thus drier conditions in Cuba. On orbital timescales, Cuban stalagmites suggest a relation of speleothem δ18O values with the δ18O value of Caribbean surface waters (Fensterer et al., 2013). Here we present an expansion of the Cuban speleothem record covering the whole last glacial period from the end of MIS5c (97 ka BP) until 7 ka with hiatuses between 93-80 ka, 37-35 ka and 13-10 ka. Stalagmite Cuba medio (CM) has been precisely dated with 60 230Th/U-ages, mainly performed by the MC-ICPMS technique. The δ18O and δ13C records are completed by a continuous, high resolution LA-ICPMS trace element profile. These data allow for the first time to establish a multi-proxy climate reconstruction for the North Western Caribbean at decadal to centennial resolution for this period. The long-term variability of the δ18O values probably reflects rainfall amount in Cuba. The response to some Dansgaard/Oeschger and Heinrich stadials confirms the previously observed correlation between Caribbean and NA climate variability. However, this connection is not clearly imprinted throughout the record. Furthermore, trace elements, such as Mg, do not proof without ambiguity drier conditions in Cuba during NA cold events, such as the Heinrich stadials. This suggests that climate variability in Cuba was more complex during the last 100ka, and that the NA was not the only driving factor

  20. The anatomy of Last Glacial Maximum climate variations in south Westland, New Zealand, derived from pollen records

    Science.gov (United States)

    Vandergoes, Marcus J.; Newnham, Rewi M.; Denton, George H.; Blaauw, Maarten; Barrell, David J. A.

    2013-08-01

    We present pollen records from three sites in south Westland, New Zealand, that document past vegetation and inferred climate change between approximately 30,000 and 15,000 cal. yr BP. Detailed radiocarbon dating of the enclosing sediments at one of those sites, Galway tarn, provides a more robust chronology for the structure and timing of climate-induced vegetation change than has previously been possible in this region. The Kawakawa/Oruanui tephra, a key isochronous marker, affords a precise stratigraphic link across all three pollen records, while other tie points are provided by key pollen-stratigraphic changes which appear to be synchronous across all three sites. Collectively, the records show three episodes in which grassland, interpreted as indicating mostly cold subalpine to alpine conditions, was prevalent in lowland south Westland, separated by phases dominated by subalpine shrubs and montane-lowland trees, indicating milder interstadial conditions. Dating, expressed as a Bayesian-estimated single 'best' age followed in parentheses by younger/older bounds of the 95% confidence modelled age range, indicates that a cold stadial episode, whose onset was marked by replacement of woodland by grassland, occurred between 28,730 (29,390-28,500) and 25,470 (26,090-25,270) cal. yr BP (years before AD, 1950), prior to the deposition of the Kawakawa/Oruanui tephra. Milder interstadial conditions prevailed between 25,470 (26,090-25,270) and 24,400 (24,840-24,120) cal. yr BP and between 22,630 (22,930-22,340) and 21,980 (22,210-21,580) cal. yr BP, separated by a return to cold stadial conditions between 24,400 and 22,630 cal. yr BP. A final episode of grass-dominated vegetation, indicating cold stadial conditions, occurred from 21,980 (22,210-21,580) to 18,490 (18,670-17,950) cal. yr BP. The decline in grass pollen, indicating progressive climate amelioration, was well advanced by 17,370 (17,730-17,110) cal. yr BP, indicating that the onset of the termination in south

  1. The Pleistocene vermicular red earth in South China signaling the global climatic change: The molecular fossil record

    Institute of Scientific and Technical Information of China (English)

    XIE; Shucheng; (谢树成); YI; Yi; (易; 轶); LIU; Yuyan; (刘育燕); GU; Yansheng; (顾延生); MA; Zhenxing; (马振兴); LIN; Wenjiao; (林文姣); WANG; Xianyan; (王先彦); LIU; Gang; (刘; 刚); LIANG; Bin; (梁; 斌); ZHU; Zongmin; (朱宗敏)

    2003-01-01

    The trace molecular fossils identified in the Pleistocene vermicular red earth by using the gas chromatography-mass spectrometry (GC/MS) analysis include n-alkanes, n-alkanoic acids, n-alkanols and n-alkan-2-ones. The variations of the n-alkane parameters appear to bear significant climate information, in striking contrast to the oxygen-bearing molecules (n-alkanoic acids and n-alkanols) believed to be more easily reworked by post-depositional processes. Of importance in paleoclimate reconstruction are the ratios of C27/C31 n-alkane indicative of the replacement of woody plants by grassy vegetation, and C15-21/C22-33 n-alkane representative of the relative abundance between microorganisms and higher plants. The profile trends of the two n-alkane ratios are comparable to the marine oxygen isotope record among stages 4-20. These molecular fossil records implicate that the Pleistocene vermicular red earth widespread in South China was formed in coupling to the global climatic change and could be an important climate carrier.

  2. Vegetation evolution and millennial-scale climatic fluctuations since Last Glacial Maximum in pollen record from northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    LUO Yunli; SUN Xiangjun

    2005-01-01

    In order to study vegetation evolution and environmental change since the Last Glacial Maximum (LGM), a total of 180 pollen samples with an average time resolution of 150 years were analyzed on the top parts(0-31 m, 0-27 kaBP)of deep sea sediments from ODP Site 1144 (20°3.18(N, 1170°25.14(E), northeastern SCS. The character- istic features of pollen diagram include that pine dominates in the interglacial, and herb pollen dominates with a good deal of tropical-subtropical pollen in the last glacial, and from 18 kaBP the tropical-subtropical pollen influx rose abruptly, while the herbaceous pollen influx and percentage dropped quickly, indicating that climate turned warmer and more humid, and more tropical-subtropical vegetation grew on the mainland and the emerging continental shelf, while the grassland on the shelf diminished. A detailed comparison shows an earlier change of pollen assemblages at the glacial- interglacial transition between MIS6 and 5 (Termination II) than the ice volume change indicated by the oxygen isotope record, implying that mid-low latitude climate warming preceded ice sheet retreat. Millennial-scale climatic fluctuations of vegetation change in pollen record are also discussed.

  3. The Preboreal-like Asian monsoon climate in the early last interglacial period recorded from the Dark Cave, Southwest China

    Science.gov (United States)

    Jiang, Xiuyang; He, Yaoqi; Wang, Xiaoyan; Sun, Xiaoshuang; Hong, Hui; Liu, Juan; Yu, Tsai-Luen; Li, Zhizhong; Shen, Chuan-Chou

    2017-08-01

    Transitions of glacial-interglacial cycles are critical periods for Quaternary climate shifts. Here, we present new, decadal resolution Asian summer monsoon (ASM) record from three stalagmites obtained from the Dark Cave in southwestern China over 130-114 thousand years ago (ka, before CE 1950). Chronology was anchored by 28 230Th dates with typical uncertainties of ±0.3-1.0 kyr, allowing an assessment of timing and transition of climate changes during the onset and end of the last interglacial. An agreement between this new and previous stalagmite δ18O records supports that summer insolation predominates orbital-scale ASM evolution. A 2-3 kyr-long gradually increasing ASM period, analogous to the classical Preboreal episode in the early Holocene, follows the termination of a weak monsoon interval at 129.0 ± 0.8 ka. This finding suggests a strong influence of high-latitude ice-sheet dynamics on Asian monsoonal conditions during the early interglacial period. An abrupt end of the marine isotope stage 5e at 118.8 ± 0.6 ka was probably caused by the internal climate system threshold effects.

  4. A terrestrial record of Last Interglacial climate preserved by voluminous debris avalanche inundation in Taranaki, New Zealand

    Science.gov (United States)

    Newnham, Rewi; Alloway, Brent

    2004-03-01

    At Airedale Reef, western North Island, New Zealand, a ca. 4 m thick volcanogenic debris avalanche deposit has facilitated the preservation of an enveloping sequence of peats with interbedded andesitic tephras spanning marine isotope (MIS) 5. The sequence closely overlies a wave-cut terrace correlated to MIS 5e and, in turn, is overlain by andic beds with tephra interbeds including the Rotoehu and Kawakawa tephras deposited during early MIS 3 and mid-MIS 2, respectively. Pollen analysis of the organic sequence shows a coherent pattern of fluctuating climate for the Last Interglacial-Last Glacial transition that corresponds with marine isotope stratigraphy and supports the contention that orbital variations were a primary factor in late Quaternary southern mid-latitude climate change. A five-stage subdivision of MIS 5 is clearly recognised, with marine isotope substage (MISS) 5b drier than MISS 5d, and the cooling transition from 5a to MIS 4 also may have been comparatively dry and characterised by natural fire, perhaps associated with volcanism. Several other examples of volcanic impact on vegetation and the landscape are evident. The Airedale Reef sequence exhibits strong similarities with fragmentary MIS 5 pollen records preserved elsewhere in New Zealand and enables the proxy record of southern mid-latitude climatic variability during the Last Interglacial-Glacial cycle to be extended. Copyright

  5. Strong asymmetry of hemispheric climates during MIS-13 inferred from correlating China loess and Antarctica ice records

    Directory of Open Access Journals (Sweden)

    Z. T. Guo

    2008-10-01

    Full Text Available The loess-soil sequence in northern China is among the best long-term terrestrial climate records in the Northern Hemisphere that documented the history of the Asian summer and winter monsoon circulations, dust emission and aridity of inland deserts. In the Southern Hemisphere, the Antarctica ice cores provided a 800-thousand year (ka history of the atmospheric methane (CH4 and carbon dioxide (CO2 concentrations, eolian dust and Antarctica temperature. We correlate the two records to address the hemispheric climate link in the past 800 ka and the potential roles of Asian dust and monsoon on the atmospheric CO2 and CH4 levels. The results show a broad coupling between the Asian and Antarctic climates at the glacial-interglacial scale and support a potential role of Asian dust and monsoon in modulating the atmospheric concentration of greenhouse gases. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS 13 exhibits the strongest anomalous link compared with the other interglacials. It is characterized by the greatest interglacial global ice volume, carbon isotope (δ13C maxima in the world oceans, cooler Antarctic temperature, more extended sea ice in the Southern Ocean, lower CO2 and CH4 concentrations, but by unusually strengthened Asian, Indian and African monsoons, weakest Asian winter monsoon, lowest Asian dust and iron fluxes. Particularly warm conditions were also reported for the elevated Tibetan Plateau and northern high-latitude regions. These lines of evidence consistently suggest an increased ice volume in the Southern Hemisphere, a substantially reduced ice volume in the Northern Hemisphere during MIS-13, and hence, an enhanced hemispheric asymmetry of polar ice-conditions. This event has deeply affected the continental, marine and atmospheric conditions at the global scale. Similar anomalies of lesser extents also

  6. Late Pleistocene-early Holocene karst features, Laguna Madre, south Texas: A record of climate change

    Energy Technology Data Exchange (ETDEWEB)

    Prouty, J.S. [Texas A& M Univ., Corpus Christi, TX (United States)

    1996-09-01

    A Pleistocene coquina bordering Laguna Madre, south Texas, contains well-developed late Pleistocene-early Holocene karst features (solution pipes and caliche crusts) unknown elsewhere from coastal Texas. The coquina accumulated in a localized zone of converging longshore Gulf currents along a Gulf beach. The crusts yield {sup 14}C dates of 16,660 to 7630 B.P., with dates of individual crust horizons becoming younger upwards. The karst features provide evidence of regional late Pleistocene-early Holocene climate changes. Following the latest Wisconsinan lowstand 18,000 B.P. the regional climate was more humid and promoted karst weathering. Partial dissolution and reprecipitation of the coquina formed initial caliche crust horizons; the crust later thickened through accretion of additional carbonate laminae. With the commencement of the Holocene approximately 11,000 B.P. the regional climate became more arid. This inhibited karstification of the coquina, and caliche crust formation finally ceased about 7000 B.P.

  7. Late glacial climate estimates for southern Nevada: The ostracode fossil record

    Energy Technology Data Exchange (ETDEWEB)

    Forester, R.M. [Geological Survey, Denver, CO (United States); Smith, A.J. [Kent State Univ., OH (United States)

    1995-10-01

    Climate change plays an important role in determining as possible long term hydrological performance of the potential high level nuclear waste repository within Yucca Mountain, Nevada. Present-day global circulation results in this region having an arid to semi-arid climate characterized by hot and relatively dry summers. Global circulation during the late glacial (about 14 to 20 ka) was very different from the present-day. Preliminary study of late-glacial fossil ostracodes from {open_quotes}marsh deposits{close_quotes} in the upper Las Vegas Valley suggests mean annual precipitation may have been four times higher, while mean annual temperature may have been about 10{degrees}C cooler than today. A major difference between present-day and late-glacial climate was likely the existence of cooler, cloudier, and wetter summers in the past.

  8. Long memory effect of past climate change in Vostok ice core records

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Yuuki, E-mail: yyama@ed.yama.tus.ac.jp [Department of Mechanical Engineering, Tokyo University of Science, Yamaguchi (Japan); Kitahara, Naoki [Department of Electronics and Computer Science, Tokyo University of Science, Yamaguchi (Japan); Kano, Makoto [Department of Mechanical Engineering, Tokyo University of Science, Yamaguchi (Japan)

    2012-03-20

    Time series analysis of Vostok ice core data has been done for understanding of palaeoclimate change from a stochastic perspective. The Vostok ice core is one of the proxy data for palaeoclimate in which local temperature and precipitation rate, moisture source conditions, wind strength and aerosol fluxes of marine, volcanic, terrestrial, cosmogenic and anthropogenic origin are indirectly stored. Palaeoclimate data has a periodic feature and a stochastic feature. For the proxy data, spectrum analysis and detrended fluctuation analysis (DFA) were conducted to characterize periodicity and scaling property (long memory effect) in the climate change. The result of spectrum analysis indicates there exist periodicities corresponding to the Milankovitch cycle in past climate change occurred. DFA clarified time variability of scaling exponents (Hurst exponent) is associated with abrupt warming in past climate.

  9. A stable, unbiased, long-term satellite based data record of sea surface temperature from ESA's Climate Change Initiative

    Science.gov (United States)

    Rayner, Nick; Good, Simon; Merchant, Chris

    2013-04-01

    The study of climate change demands long-term, stable observational records of climate variables such as sea surface temperature (SST). ESA's Climate Change Initiative was set up to unlock the potential of satellite data records for this purpose. As part of this initiative, 13 projects were established to develop the data records for different essential climate variables - aerosol, cloud, fire, greenhouse gases, glaciers, ice sheets, land cover, ocean colour, ozone, sea ice, sea level, soil moisture and SST. In this presentation we describe the development work that has taken place in the SST project and present new prototype data products that are available now for users to trial. The SST project began in 2010 and has now produced two prototype products. The first is a long-term product (covering mid-1991 - 2010 currently, but with a view to update this in the future), which prioritises length of data record and stability over other considerations. It is based on data from the Along-Track Scanning Radiometer (ATSR) and Advanced Very-High Resolution Radiometer (AVHRR) series of satellite instruments. The product aims to combine the favourable stability and bias characteristics of ATSR data with the geographical coverage achieved with the AVHRR series. Following an algorithm selection process, an optimal estimation approach to retrieving SST from the satellite measurements from both sensors was adopted. The retrievals do not depend on in situ data and so this data record represents an independent assessment of SST change. In situ data are, however, being used to validate the resulting data. The second data product demonstrates the coverage that can be achieved using the modern satellite observing system including, for example, geostationary satellite data. Six months worth of data have been processed for this demonstration product. The prototype SST products will be released in April to users to trial in their work. The long term product will be available as

  10. The ice-core record - Climate sensitivity and future greenhouse warming

    Science.gov (United States)

    Lorius, C.; Raynaud, D.; Jouzel, J.; Hansen, J.; Le Treut, H.

    1990-01-01

    The prediction of future greenhouse-gas-warming depends critically on the sensitivity of earth's climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial-interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the role of greenhouse gases in explaining past global climate change, and the validity of models predicting the effect of increasing concentrations of such gases in the atmosphere.

  11. Vesetation and climate changes during the last 8660 cal. a BP in central Mongolia, based on a high-resolution pollen record from Lake Ugii Nuur

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; MA YuZhen; FENG ZhaoDong; MENG HongWei; SANG YanLi; ZHAI XinWei

    2009-01-01

    Based on modern pollen studies and reliable chronology of nine AMS 14C dates, a detailed history of vegetation and climate changes during the past 8660 cal. a BP was reconstructed by a high-resolution pollen record from Ugii Nuur in central Mongolia. Poaceae-steppe dominated the study area and the climate was mild and semi-humid before 7800 cal. a BP with a noticeable cool and humid interval at 8350-8250 cal. a BP. Xerophytic plant increased and the climate became warm and dry gradually since 7800 cal. a BP. From 6860 to 3170 cal. a BP, semi-desert steppe expanded, suggesting a prolonged warm and dry climate. Between 3170 and 2340 cal. a BP, regional forest steppe expanded whereas semi-desert steppe retreated, indicating the climate became cool and wet gradually and the humidity reached the maximum at the end of this stage. From 2340 to 1600 cal. a BP, a general cool and wet climate prevailed. And the climatic instability increased after 1600 cal. a BP. Review of regional pub-lished palaeoclimaUc records implies that the mid-Holocene dry climate might have prevailed in vast areas from central Mongolia to arid areas of northwest China. Pollen-based climate reconstruction for UG04 core was well correlated with the result of climate model on Central Asia by Bush. In addition, several abrupt climatic events (cool and wet) were found and some could be broadly compared with the cool events in Atlantic.

  12. Pollen records of Holocene vegetation and climate changes in the Longzhong Basin of the Chinese Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Pollen records with an average time resolution of 20200 years from Holocene loess sections at Dingxi,Qin'an,and other localities of Gansu Province reveal a detailed history of vegetation and climate changes in the western Loess Plateau.For most time of the Holocene,the landscape was dominated by grasslands or forest steppes.However,during the middle Holocene(7.5-5.8 ka BP),relatively dense forests developed,and the endemic vegetation flourished,suggesting a much warmer and more humid climate condition than the present.Superimposed upon this general pattern are several dry intervals marked by the episodic expansion of grasslands or forest steppe.Xeric vegetation expanded after 3.8 ka BP,indicating a trend towards dry conditions.

  13. NOAA Climate Data Record (CDR) of Reflectance and Brightness Temperatures from AVHRR Pathfinder Atmospheres - Extended (PATMOS-x), Version 5.3

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) of AVHRR reflectance and brightness temperatures was produced by the University of Wisconsin using the AVHRR Pathfinder...

  14. NOAA Climate Data Record of Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit (AMSU-A) Mean Layer Temperature, Version 3.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset contains three channel-based, monthly gridded atmospheric layer temperature Climate Data Records generated by merging nine MSU NOAA polar orbiting...

  15. NOAA Climate Data Record (CDR) of Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN-CDR), Version 1 Revision 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — PERSIANN Precipitation Climate Data Record (PERSIANN-CDR) is a daily quasi-global precipitation product for the period of 1982 to 2011. The data covers from 60...

  16. Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)

    Science.gov (United States)

    Starnberger, Reinhard; Drescher-Schneider, Ruth; Reitner, Jürgen M.; Rodnight, Helena; Reimer, Paula J.; Spötl, Christoph

    2013-05-01

    Drill cores from the inner-alpine valley terrace of Unterangerberg, located in the Eastern Alps of Austria, offer first insights into a Pleistocene sedimentary record that was not accessible so far. The succession comprises diamict, gravel, sand, lignite and thick, fine grained sediments. Additionally, cataclastic deposits originating from two paleo-landslide events are present. Multi-proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period (Würmian) at Unterangerberg at ˜120-110 ka. This first time period, correlated to the MIS 5d, was characterised by strong fluvial aggradation under cold climatic conditions, with only sparse vegetation cover. Furthermore, two large and quasi-synchronous landslide events occurred during this time interval. No record of the first Early Würmian interstadial (MIS 5c) is preserved. During the second Early Würmian interstadial (MIS 5a), the local vegetation was characterised by a boreal forest dominated by Picea, with few thermophilous elements. The subsequent collapse of the vegetation is recorded by sediments dated to ˜70-60 ka (i.e. MIS 4), with very low pollen concentrations and the potential presence of permafrost. Climatic conditions improved again between ˜55 and 45 ka (MIS 3) and cold-adapted trees re-appeared during interstadials, forming an open forest vegetation. MIS 3 stadials were shorter and less severe than the MIS 4 at Unterangerberg, and vegetation during these cold phases was mainly composed of shrubs, herbs and grasses, similar to what is known from today's alpine timberline. The Unterangerberg record ended at ˜45 ka and/or was truncated by ice during the Last Glacial Maximum.

  17. Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria).

    Science.gov (United States)

    Starnberger, Reinhard; Drescher-Schneider, Ruth; Reitner, Jürgen M; Rodnight, Helena; Reimer, Paula J; Spötl, Christoph

    2013-05-15

    Drill cores from the inner-alpine valley terrace of Unterangerberg, located in the Eastern Alps of Austria, offer first insights into a Pleistocene sedimentary record that was not accessible so far. The succession comprises diamict, gravel, sand, lignite and thick, fine grained sediments. Additionally, cataclastic deposits originating from two paleo-landslide events are present. Multi-proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period (Würmian) at Unterangerberg at ∼120-110 ka. This first time period, correlated to the MIS 5d, was characterised by strong fluvial aggradation under cold climatic conditions, with only sparse vegetation cover. Furthermore, two large and quasi-synchronous landslide events occurred during this time interval. No record of the first Early Würmian interstadial (MIS 5c) is preserved. During the second Early Würmian interstadial (MIS 5a), the local vegetation was characterised by a boreal forest dominated by Picea, with few thermophilous elements. The subsequent collapse of the vegetation is recorded by sediments dated to ∼70-60 ka (i.e. MIS 4), with very low pollen concentrations and the potential presence of permafrost. Climatic conditions improved again between ∼55 and 45 ka (MIS 3) and cold-adapted trees re-appeared during interstadials, forming an open forest vegetation. MIS 3 stadials were shorter and less severe than the MIS 4 at Unterangerberg, and vegetation during these cold phases was mainly composed of shrubs, herbs and grasses, similar to what is known from today's alpine timberline. The Unterangerberg record ended at ∼45 ka and/or was truncated by ice during the Last Glacial Maximum.

  18. Climate and vegetation history from a 14,000-year peatland record, Kenai Peninsula, Alaska

    Science.gov (United States)

    Jones, Miriam C.; Peteet, Dorothy M.; Kurdyla, Dorothy; Guilderson, Thomas

    2009-09-01

    Analysis of pollen, spores, macrofossils, and lithology of an AMS 14C-dated core from a subarctic fen on the Kenai Peninsula, Alaska reveals changes in vegetation and climate beginning 14,200 cal yr BP. Betula expansion and contraction of herb tundra vegetation characterize the Younger Dryas on the Kenai, suggesting increased winter snowfall concurrent with cool, sunny summers. Remarkable Polypodiaceae (fern) abundance between 11,500 and 8500 cal yr BP implies a significant change in climate. Enhanced peat preservation and the occurrence of wet meadow species suggest high moisture from 11,500 to 10,700 cal yr BP, in contrast to drier conditions in southeastern Alaska; this pattern may indicate an intensification and repositioning of the Aleutian Low (AL). Drier conditions on the Kenai Peninsula from 10,700 to 8500 cal yr BP may signify a weaker AL, but elevated fern abundance may have been sustained by high seasonality with substantial snowfall and enhanced glacial melt. Decreased insolation-induced seasonality resulted in climatic cooling after 8500 cal yr BP, with increased humidity from 8000 to 5000 cal yr BP. A dry interval punctuated by volcanic activity occurred between 5000 and 3500 cal yr BP, followed by cool, moist climate, coincident with Neoglaciation. Tsuga mertensiana expanded after ~ 1500 cal yr BP in response to the shift to cooler conditions.

  19. Extending the soil moisture record of the climate reference network with machine learning

    Science.gov (United States)

    Soil moisture estimation is crucial for agricultural decision-support and a key component of hydrological and climatic research. Unfortunately, quality-controlled soil moisture time series data are uncommon before the most recent decade. However, time series data for precipitation are accessible at ...

  20. A Holocene record of climate-driven shifts in coastal carbon sequestration

    Science.gov (United States)

    Mitra, Siddhartha; Zimmerman, A.R.; Hunsinger, G.B.; Willard, D.; Dunn, J.C.

    2009-01-01

    A sediment core collected in the mesohaline portion of Chesapeake Bay was found to contain periods of increased delivery of refractory black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs). The BC was most likely produced by biomass combustion during four centennialscale dry periods as indicated by the Palmer Drought Severity Index (PDSI), beginning in the late Medieval Warm Period of 1100 CE. In contrast, wetter periods were associated with increased non-BC organic matter influx into the bay, likely due to greater runoff and associated nutrient delivery. In addition, an overall increase in both BC and non-BC organic matter deposition during the past millennium may reflect a shift in climate regime. The finding that carbon sequestration in the coastal zone responds to climate fluctuations at both centennial and millennial scales through fire occurrence and nutrient delivery has implications for past and future climate predictions. Drought-induced fires may lead, on longer timescales, to greater carbon sequestration and, therefore, represent a negative climate feedback. Copyright 2009 by the American Geophysical Union.

  1. A record of the variability of climate transitions between the last four glacial cycles from high-precision speleothem chronology

    Science.gov (United States)

    Polyak, V. J.; Asmerom, Y.; Lachniet, M. S.; Lapointe, Z. C.

    2011-12-01

    Speleothem growth in Fort Stanton Cave, central New Mexico in southwestern North America (SWNA), occurred predominantly during glacial periods for the last four glacial cycles, with some, but little growth spilling over into the glacial termination events. Given that lacustrine records show that glacial periods are pluvial periods in SWNA, Fort Stanton Cave speleothem growth seems to be a faithful indicator of periods of greater effective moisture for SWNA. Likewise, Asmerom et al. (2010) provided the first stable isotope record from a Fort Stanton stalagmite (FS-2) and reported an oxygen isotope record between 11.4 and 56 ka that closely mimicked the Greenland ice core oxygen records over much of the last glacial period. The δ18O variation in FS-2 reflected changes in the amount of winter precipitation, which in turn reflected the position of the Polar Jet Stream in response to changes in Northern Hemisphere temperature gradient. In contrast, variations in δ13C primarily reflect changes in the amount and type of vegetation which is linked to changes in local aridity. The stalagmites from this cave have high uranium, high δ234U and low detritus thorium and are thus ideally suited for dating using the uranium-series technique. Here we present a record of climate variability for the previous four ice ages. Based on growth of multiple stalagmites, we define the period from ~60 to 14.5 ka as speleothem-based pluvial 1 (SWNA-P1). Speleothems FS-5, FS-6, TR-2, TR-3 and HH-1 grew during glacial cycles 2-4, which we define as pluvials 2, 3, & 4 (SWNA-P2, P3, and P4) where preliminary results suggest that SWNA-P2 lasted from 170 to 130 ka, SWNA-P3 from 265 to 242 ka, and SWNA-P4 from 352 to 336 ka. Growth hiatuses and the carbon isotope records indicate the timing of pluvial terminations. Overall, SWNA-P3 is more similar to SWNA-P1, showing events that may have been more complex, with both exhibiting stadial- and interstadial-like climatic signals, while SWNA-P2 and P4

  2. Tectonic, human and climate signal over the last 4000 years in the Lake Amik record (southern Turkey)

    Science.gov (United States)

    El Ouahabi, Meriam; Hubert-Ferrari, Aurélia; Vander Auwera, Jacqueline; Lepoint, Gilles; Karabacak, Volkan; Schmidt, Sabine; Fagel, Nathalie

    2017-04-01

    This study investigates the upper sediments infilling the central part of the Amik Basin in Southern Turkey. The Amik Basin is located in a tectonically active area: it is crossed by the Dead Sea Fault, a major neotectonic structure in the Middle East extending from the Red Sea in the South to the East Anatolian Fault Zone in the North. Continuous human occupation is attested since 6000-7000 BC in the Amik Basin. The study focuses on the sedimentary record of the Lake Amik occupying the central part of the Basin. Our objective is to constrain major paleo-environmental changes over the last 4000 years. The lake has been drained and progressively dried up since the mid-50s. The absence of water column during the summer season allows to collect lacustrine samples along a 5 meter depth trench with a sampling resolution of 1 to 2 cm. Diverse complementary methods were applied to characterize the sedimentary record: i.e. magnetic susceptibility, grain size, organic and inorganic matter by loss-of-ignition, mineralogy by X-ray diffraction and core scanner X-ray fluorescence (XRF) geochemistry. The age of the record is constrained combining radionuclide and radiocarbon datings. Structural disturbances observed in the lacustrine sediments record are linked with major historical earthquakes from the 6th to the 9th century AD due to the Hasipasa Fault rupture. In addition to the tectonic influence, the sedimentary record clearly shows two periods indicating strong soil erosion in the lake catchment: (1) the most recent erosion phase occurs over the Roman period to Present; (2) the oldest one would have occurred during the Late Bronze period. Such changes are most probably related to change in land use. In term of climate influences, the mineralogical and geochemical results allow to evidence variations in chemical weathering conditions in the watershed and lake water level fluctuations, respectively. The clay mineral assemblages attest for significant pedogenesis

  3. Strong asymmetry of hemispheric climates during MIS-13 inferred from correlating China loess and Antarctica ice records

    Directory of Open Access Journals (Sweden)

    Z. T. Guo

    2009-02-01

    Full Text Available We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800 ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (δ18O and carbon isotope (δ13C values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO2 and CH4 concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemisphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO2 changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale. The correlations also suggest that the marine δ18O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of

  4. 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

  5. Pangaean climate during the Early Jurassic: GCM simulations and the sedimentary record of paleoclimate

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, M.A. [Columbia Univ., Palisades, NY (United States); Rind, D.; Ruedy, R. [Goddard Institute for Space Studies, New York, NY (United States)

    1992-05-01

    Results from new simulations of the Early Jurassic climate show that increased ocean heat transport may have been the primary force generating warmer climates during the past 180 m.y. The simulations, conducted using the general circulation model (GCM) at the Goddard Institute for Space Studies, include realistic representations of paleocontinental distribution, topography, epeiric seas, and vegetation, in order to facilitate comparisons between model results and paleoclimate data. three major features of the simulated Early Jurassic climate include the following. (1) A global warming, compared to the present, of 5 {degrees}C to 10 {degrees}C, with temperature increases at high latitudes five times this global average. Average summer temperatures exceed 35 {degrees}C in low-latitude regions of western Pangaea where eolian sandstones testify to the presence of vast deserts. (2) Simulated precipitation and evaporation patterns agree closely with the moisture distribution interpreted from evaporites, and coal deposits. High rainfall rates are associated primarily with monsoons that originate over the warm Tethys Ocean. Unlike the {open_quotes}megamonsoons{close_quotes} proposed in previous studies, these systems are found to be associated with localized pressure cells whose positions are controlled by topography and coastal geography. (3) Decreases in planetary albedo, occurring because of reductions in sea ice, snow cover, and low clouds, and increases in atmospheric water vapor are the positive climate feedbacks that amplify the global warming. Similar to other Mesozoic climate simulations, our model finds that large seasonal temperature fluctuations occurred over mid- and high-latitude continental interiors, refuting paleoclimate evidence that suggests more equable conditions. 101 refs., 9 figs., 3 tabs.

  6. Partitioning energy flux using climate record and remote sensing data across the Yukon River Basin, Alaska

    Science.gov (United States)

    Huang, S.; Dahal, D.; Singh, R. K.; Young, C. J.; Tieszen, L. L.; Liu, S.

    2011-12-01

    The Yukon River Basin (YRB) in Alaska is located in high latitudes and underlain by intermittent permafrost, but it is experiencing rapid warming and creating feedback to the climate system. Fire, ecological succession, and climate are interactively affecting YRB ecosystem functions (e.g., primary production, microbial activities, and greenhouse gas emissions) where solar energy transfer processes are critical. Energy flux at some specific locations was investigated; however, variations over landscape level are not well understood. To fully understand the ecosystem dynamics associated with disturbance and climate change, it is important to divide the landscape net radiation (Rn) into three components: latent energy required for evapotranspiration (LE), soil heat flux conducted into the ground (G), and sensible heat flux convected to the air (H). MODerate Resolution Imaging Spectroradiometer (MODIS) products (NDVI, surface temperature, albedo, and emissivity) and hourly weather measurements from 2002-2004 were collected. We developed an energy balance partitioning model that considers the impacts of terrain, vegetation, and climate. A spatial analysis tool was also developed for satellite-based energy balance computation based on the algorithm of "Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC)." We computed time series intra- and inter-annual products of LE, G, and H. We have been validating the products using flux tower measurements. Landscape-level products of Rn, LE, G, and H allow us to analyze the spatio-temporal variation of energy flux in the land-atmosphere system. Initial results show that i) landscape heterogeneity in terms of vegetation, elevation, and climate has great effect on the pattern of solar energy partitioning, ii) fire disturbance significantly affects energy flux partitioning. Key words: energy flux, evapotranspiration, flux tower, METRIC, MODIS

  7. A 20 year independent record of sea surface temperature for climate from Along-Track Scanning Radiometers

    Science.gov (United States)

    Merchant, Christopher J.; Embury, Owen; Rayner, Nick A.; Berry, David I.; Corlett, Gary K.; Lean, Katie; Veal, Karen L.; Kent, Elizabeth C.; Llewellyn-Jones, David T.; Remedios, John J.; Saunders, Roger

    2012-12-01

    A new record of sea surface temperature (SST) for climate applications is described. This record provides independent corroboration of global variations estimated from SST measurements made in situ. Infrared imagery from Along-Track Scanning Radiometers (ATSRs) is used to create a 20 year time series of SST at 0.1° latitude-longitude resolution, in the ATSR Reprocessing for Climate (ARC) project. A very high degree of independence of in situ measurements is achieved via physics-based techniques. Skin SST and SST estimated for 20 cm depth are provided, with grid cell uncertainty estimates. Comparison with in situ data sets establishes that ARC SSTs generally have bias of order 0.1 K or smaller. The precision of the ARC SSTs is 0.14 K during 2003 to 2009, from three-way error analysis. Over the period 1994 to 2010, ARC SSTs are stable, with better than 95% confidence, to within 0.005 K yr-1(demonstrated for tropical regions). The data set appears useful for cleanly quantifying interannual variability in SST and major SST anomalies. The ARC SST global anomaly time series is compared to the in situ-based Hadley Centre SST data set version 3 (HadSST3). Within known uncertainties in bias adjustments applied to in situ measurements, the independent ARC record and HadSST3 present the same variations in global marine temperature since 1996. Since the in situ observing system evolved significantly in its mix of measurement platforms and techniques over this period, ARC SSTs provide an important corroboration that HadSST3 accurately represents recent variability and change in this essential climate variable.

  8. Climate Change: A New Metric to Measure Changes in the Frequency of Extreme Temperatures using Record Data

    Science.gov (United States)

    Munasinghe, L.; Jun, T.; Rind, D. H.

    2012-01-01

    Consensus on global warming is the result of multiple and varying lines of evidence, and one key ramification is the increase in frequency of extreme climate events including record high temperatures. Here we develop a metric- called "record equivalent draws" (RED)-based on record high (low) temperature observations, and show that changes in RED approximate changes in the likelihood of extreme high (low) temperatures. Since we also show that this metric is independent of the specifics of the underlying temperature distributions, RED estimates can be aggregated across different climates to provide a genuinely global assessment of climate change. Using data on monthly average temperatures across the global landmass we find that the frequency of extreme high temperatures increased 10-fold between the first three decades of the last century (1900-1929) and the most recent decade (1999-2008). A more disaggregated analysis shows that the increase in frequency of extreme high temperatures is greater in the tropics than in higher latitudes, a pattern that is not indicated by changes in mean temperature. Our RED estimates also suggest concurrent increases in the frequency of both extreme high and extreme low temperatures during 2002-2008, a period when we observe a plateauing of global mean temperature. Using daily extreme temperature observations, we find that the frequency of extreme high temperatures is greater in the daily minimum temperature time-series compared to the daily maximum temperature time-series. There is no such observable difference in the frequency of extreme low temperatures between the daily minimum and daily maximum.

  9. Holocene paleoclimate records from a large California estuarine system and its watershed region: linking watershed climate and bay conditions

    Science.gov (United States)

    Malamud-Roam, Frances P.; Lynn Ingram, B.; Hughes, Malcolm; Florsheim, Joan L.

    2006-07-01

    The San Francisco Bay-Delta system includes a watershed that covers a large area of California and provides water to two-thirds of the State's population. Climate over the estuary and its watershed in the dry summer months is controlled by the subtropical high which dominates and deflects storms from California. The subtropical high weakens and migrates south as the Aleutian Low strengthens, bringing wet winter storms to the region. Paleoclimatic records from the Bay and its greater watershed, spanning the Holocene, are reviewed here in order to better understand natural variations of precipitation and runoff and the linkages between those variations and the salinity and ecosystems of the estuary. To better understand regional-scale climate patterns, paleoclimate records from coastal California and the Great Basin are also considered. Large fluctuations in climate have occurred during the period of interest, and there is generally good agreement between the paleoclimate records from different regions. Early Holocene climate throughout California was marked by rising temperatures and reduced moisture as seen in fire records from the watershed. This warmth and aridity peaked about 5000-7000 years ago and was followed by a cooling trend, with variable moisture conditions. The Estuary formed relatively rapidly in response to a high rate of sea level rise that dominated the Holocene until about 6000 years ago, and the subsequent reduced rate of inundation allowed vast tidal marshes to form along the edges of the estuary, which have since been recording changes in environmental conditions. The impacts of changing regional climate patterns are experienced in the San Francisco Bay-Delta system, as altered fresh water flows result in altered estuary salinity. For example, approximately 3800 cal yr B.P., records from throughout the state indicate a cool, moist period, and Bay salinity was reduced; this period was followed by a general drying trend throughout California over

  10. Holocene Climatic and Hydrologic Variability as Recorded in the Benthic Foraminifera Ammonia Beccarii From Tampa Bay, Florida

    Science.gov (United States)

    Hoover, K. J.; Hastings, D. W.; Flower, B. P.; Cronin, T. M.; Brooks, G. R.

    2008-12-01

    The objective of this study is to reconstruct the climate history of Tampa Bay, Florida over the Holocene epoch using the benthic foraminifera Ammonia beccarii from five sediment cores. Here we present a reconstruction based on oxygen isotopic ratios and Mg/Ca data that provides critical information on the history of climate changes in southwest Florida. Oxygen isotopes and Mg/Ca data from samples of A. beccarii taken from a series of five sediment cores provide records of temperature and salinity changes in Tampa Bay over the last 10,000 years. Sample age was constrained using a total of 21 AMS radiocarbon dates, 11 measured on A. beccarii and 10 measured on other material in the sediment (shell, bulk organic sediment, mollusk, organic sediment, and plant). The temperature reconstruction we present provides evidence of significant variability in the climate of Tampa Bay throughout the Holocene epoch, as indicated by a relative temperature range of 6° C. The highest reconstructed temperatures within this record are found from 1000-700 yr BP, which correlates with the commonly accepted timing of the Medieval Warm Period. The lowest temperatures reflected in this record occur from 500-150 yr BP, correlating with the timing of the Little Ice Age. This record also shows that relative temperatures have increased by approximately 3-4° C from 500 yr BP to present. The signal for δ18Osw was determined from δ18Ocalcite and relative temperatures reconstructed from Mg/Ca; changes in both δ18Osw and temperature are relative since the temperature calibration is not species specific. The results would be improved if a Mg/Ca temperature calibration for the species A. beccarii was developed and used. Values of δ18Osw fall within a range of 2.0 permil VPDB over the last 10,000 years, indicating significant changes to the hydrology of Tampa Bay. These results support evidence from the Gulf of Mexico for substantial hydrologic variability on the sub-centennial-scale. These

  11. A high-resolution, absolute-dated deglacial speleothem record of Indian Ocean climate from Socotra Island, Yemen

    Science.gov (United States)

    Shakun, Jeremy D.; Burns, Stephen J.; Fleitmann, Dominik; Kramers, Jan; Matter, Albert; Al-Subary, Abdulkarim

    2007-07-01

    Stalagmite M1-5 from Socotra Island, Yemen in the northwest Indian Ocean provides a robust, high-resolution paleoclimate record from ˜ 27.4-11.1 ka based on 717 stable isotope and 28 230Th measurements. Variations in M1-5 oxygen isotope ratios ( δ18O) are interpreted to be primarily driven by an amount effect related to changes in the mean position and/or intensity of convection of the intertropical convergence zone, the island's only source of precipitation. The M1-5 δ18O time series is strongly correlated to the Greenland ice cores, similar to an older Socotra speleothem deposited from 53-40 ka [S.J. Burns, D. Fleitmann, A. Matter, J. Kramers, A. Al-Subbary, Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13, Science 301 (2003) 1365-1367], indicating that a North Atlantic-Indian Ocean cold-dry/warm-wet teleconnection persisted through the end of the last glacial period. Peak aridification occurred at ˜ 23 ka and a gradual increase in moisture thereafter was interrupted by an abrupt drying event at ˜ 16.4 ka, perhaps related to Heinrich event 1. Indian Ocean rainfall increased dramatically during the Bølling period and then decreased continuously and gradually through the Allerød and Younger Dryas. The Holocene began abruptly with increased precipitation at 11.4 ka and was followed by a major but short-lived drying during the Preboreal Oscillation at ˜ 11.2 ka. M1-5 is highly correlated to the Dongge Cave record from 15.5-11 ka, suggesting much of the Indian Ocean monsoon region responded similarly to the major climate changes of the last deglaciation. The transitions into the Younger Dryas and to a lesser extent the Bølling are remarkably gradual in M1-5, as they are in all other Asian speleothem records, occurring over several centuries. These gradual transitions are in striking contrast to high-resolution records from around the North Atlantic basin where the transitions are extremely abrupt and generally occur in

  12. Hypoxic cyclicity in sediments of Soledad Basin, Baja Mexico: A record of high-frequency climate fluctuations?

    Science.gov (United States)

    Westman, A. E.; Brooks, G. R.; Lea, C.

    2007-05-01

    The sedimentary record in Soledad Basin, 45 km west of Baja, Mexico, shows high-frequency oscillations in hypoxia, which can be linked to fluctuations in climate. Soledad Basin, a semi-enclosed basin with a sill depth of 290m, has been shown to exhibit variable levels of hypoxia throughout the geologic past. Located at the intersection of the California Current and California Undercurrent, Soledad Basin is highly responsive to changes in current strength and upwelling, the combination of which creates fluctuations in hypoxia. During climatic cool periods, the California Current is weakened decreasing upwelling and biologic productivity along the Baja Borderland. This causes increased hypoxia in Soledad Basin. The California Undercurrent is also weakened during these cooler periods and brings less nutrients and oxygen to the basin further increasing hypoxia. Since Soledad Basin sediments are undisturbed and have accumulated rapidly, this is a prime location to study high frequency variations in hypoxia in the sedimentary record. The objective of this study was to examine how and to what extent hypoxic events have been recorded in the sedimentary record of Soledad Basin, and gain insight into what controls these events. Surface sediment samples and a single 1.1m gravity core were collected aboard the S.S.V. Robert C. Seamans on a SEA Semester cruise in October 2005. The core was taken at a depth of 490 m near the deepest point of the basin. The core contained laminated sediments consisting of >95% mud. Using 210Pb analysis, a sedimentation rate of 15 cm over the past 100 years was determined, which is consistent with previous research. Trace metal analyses were performed at the cm-scale on selected intervals between 0.34-0.44m and 0.78-0.92m. These intervals correspond to dark organic-rich (>15% organic content) laminations alternating with lighter layers containing less organic material (<15% organic content). All sediments were found to be enriched in Molybdenum

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

    Directory of Open Access Journals (Sweden)

    N. Combourieu-Nebout

    2013-04-01

    Full Text Available To understand the effects of future climate change on the ecology of the central Mediterranean we can look to the impacts of long-term, millennial to centennial-scale climatic variability on vegetation in the basin. Pollen data from the Adriatic Marine core MD 90-917 allows us to reconstruct vegetation and regional climate changes over the south central Mediterranean during the Holocene. 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 test precipitation changes in the Holocene. Vegetation reconstruction shows vegetation responses to the late-Glacial Preboreal oscillation, most likely driven by changes in seasonal precipitation. Pollen-inferred temperature declines during the early-mid Holocene, but increases during the mid-late Holocene, similar to southern-western Mediterranean climatic patterns during the Holocene. Several short 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 between 8000 and 7000 cal yr BP similar to the general pattern across southern Europe. Two important shifts in vegetation occur at 7700 and between 7500 and 7000 yr. These vegetation shifts are linked to changes in seasonal precipitation and are correlated to increased river inputs respectively from the north (7700 event and from the central Adriatic borderlands (7500–7000 event. These results reinforce the strengths of multi-proxy analysis and provide a deeper understanding of the role of precipitation and particularly the seasonality of precipitation in mediating vegetation change in the central Mediterranean during the Holocene.

  14. Comparison of St. Elias Ice Core Accumulation Records and Their Relationships to Climate Indices

    Science.gov (United States)

    Yalcin, K.; Osterberg, E.; Mayewski, P.; Wake, C.; Kreutz, K.; Holdsworth, G.

    2006-12-01

    Recently recovered ice cores from the St Elias Mountains (Yukon) spanning an elevation range of three (Eclipse Icefield) to more than five kilometers (Mount Logan) offer a unique three-dimensional view of paleoclimate and environmental change in the North Pacific region. The record of net accumulation as deduced from the reconstruction of observed annual layer thicknesses in these cores offers a direct view of moisture flux at various altitudes in the St. Elias. However, a potentially large uncertainty in the representativeness of ice core accumulation records exists due to spatial variability in snow accumulation rates. The availability of multiple cores allows us to address this issue. Accumulation records from Eclipse (three cores) are highly reproducible with 78% of the signal shared between the three cores. The proportion of shared signal between accumulation records from the Logan plateau (Prospector-Russell Col and Northwest Col) is lower (52%). In this work we will compare the Eclipse and Logan accumulation records to each other to understand the spatial variability in net accumulation over time at different altitudes. The possible influence of dating errors on these results will be explored using leads and lags of 1-2 years. We also compare our accumulation records to indices of atmospheric circulation (e.g., strength of the Aleutian Low, the Pacific Decadal Oscillation, the El-Nino Southern Oscillation, Arctic Oscillation) to quantify relationships between snow accumulation and large-scale atmospheric circulation features on time-scales of variability ranging from years to centuries.

  15. Middle Miocene pedological record of monsoonal climate from NW Himalaya (Jammu & Kashmir State), India

    Science.gov (United States)

    Ganjoo, R. K.; Shaker, Som

    2007-03-01

    The Lower Siwalik Subgroup represented by the Dodenal (Kamlial Formation) and Ramnagar Members (Chinji Formation) is well exposed at Ramnagar, District Udhampur, Jammu & Kashmir State. The Ramnagar Member consists of an alternating sequence of silt and mudstone formed under crevasse-splay and flood-plain environments of deposition. Argillisol and gleysol soils are developed on the Ramnagar Member deposits. Argillisols formed under well-drained conditions at high levels, whereas gleysols formed under poorly drained conditions at low levels of the palaeo-landscape. Geochemical and micromorphological studies of the Ramnagar Member palaeosols suggest formation under wet and humid climatic conditions. Early uplift of the Tibetan Plateau/Himalaya resulted in a contemporaneous change in precipitation and monsoonal climate conditions within the Indian region beginning in Middle Miocene.

  16. A Geochemical and Sedimentary Record of High Southern Latitude Holocene Climate Evolution from Lago Fagnano, Tierra del Fuego

    Energy Technology Data Exchange (ETDEWEB)

    Moy, C M; Dunbar, R B; Guilderson, T P; Waldmann, N; Mucciarone, D A; Recasens, C; Austin, J A; Anselmetti, F S

    2010-11-19

    Situated at the southern margin of the hemispheric westerly wind belt and immediately north of the Antarctic Polar Frontal zone, Tierra del Fuego is well-positioned to monitor coupled changes in the ocean-atmosphere system of the high southern latitudes. Here we describe a Holocene paleoclimate record from sediment cores obtained from Lago Fagnano, a large lake in southern Tierra del Fuego at 55{sup o}S, to investigate past changes in climate related to these two important features of the global climate system. We use an AMS radiocarbon chronology for the last 8,000 years based on pollen concentrates, thereby avoiding contamination from bedrock-derived lignite. Our chronology is consistent with a tephrochronologic age date for deposits from the middle Holocene Volcan Hudson eruption. Combining bulk organic isotopic ({delta}{sup 13}C and {delta}{sup 15}N) and elemental (C and N) parameters with physical sediment properties allow us to better understand sediment provenance and transport mechanisms and to interpret Holocene climate and tectonic change during the last 8,000 years. Co-variability and long-term trends in C/N ratio, carbon accumulation rate, and magnetic susceptibility reflect an overall Holocene increase in the delivery of terrestrial organic and lithogenic material to the deep eastern basin. We attribute this variability to westerly wind-derived precipitation. Increased wind strength and precipitation in the late Holocene drives the Nothofagus forest eastward and enhances run-off and terrigenous inputs to the lake. Superimposed on the long-term trend are a series of abrupt 9 negative departures in C/N ratio, which constrain the presence of seismically-driven mass flow events in the record. We identify an increase in bulk {delta}{sup 13}C between 7,000 and 5,000 cal yr BP that we attribute to enhanced aquatic productivity driven by warmer summer temperatures. The Lago Fagnano {delta}{sup 13}C record shows similarities with Holocene records of sea surface

  17. A geochemical and sedimentary record of high southern latitude Holocene climate evolution from Lago Fagnano, Tierra del Fuego

    Science.gov (United States)

    Moy, Christopher M.; Dunbar, Robert B.; Guilderson, Thomas P.; Waldmann, Nicolas; Mucciarone, David A.; Recasens, Cristina; Ariztegui, Daniel; Austin, James A.; Anselmetti, Flavio S.

    2011-02-01

    Situated at the southern margin of the hemispheric westerly wind belt and immediately north of the Antarctic Polar Frontal zone, Tierra del Fuego is well-positioned to monitor coupled changes in the ocean-atmosphere system of the high southern latitudes. Here we describe a Holocene paleoclimate record from sediment cores obtained from Lago Fagnano, a large lake in southern Tierra del Fuego at 55°S, to investigate past changes in climate related to these two important features of the global climate system. We use an AMS radiocarbon chronology for the last 8000 yr based on pollen concentrates, thereby avoiding contamination from bedrock-derived lignite. Our chronology is consistent with a tephrochronologic age date for deposits from the middle Holocene Volcán Hudson eruption. Combining bulk organic isotopic (δ13C and δ15N) and elemental (C and N) parameters with physical sediment properties allows us to better understand sediment provenance and transport mechanisms and to interpret Holocene climate and tectonic change during the last 8000 yr. Co-variability and long-term trends in C/N ratio, carbon accumulation rate, and magnetic susceptibility reflect an overall Holocene increase in the delivery of terrestrial organic and lithogenic material to the deep eastern basin. We attribute this variability to westerly wind-derived precipitation. Increased wind strength and precipitation in the late Holocene drives the Nothofagus forest eastward and enhances run-off and terrigenous inputs to the lake. Superimposed on the long-term trend are a series of abrupt 9 negative departures in C/N ratio, which constrain the presence of seismically-driven mass flow events in the record. We identify an increase in bulk δ13C between 7000 and 5000 cal yr BP that we attribute to enhanced aquatic productivity driven by warmer summer temperatures. The Lago Fagnano δ13C record shows similarities with Holocene records of sea surface temperature from the mid-latitude Chilean continental

  18. Sub-seasonally resolved coral records of northern Red Sea - eastern Mediterranean climate during the Holocene and the last interglacial

    Science.gov (United States)

    Felis, T.; Rimbu, N.; Al-Rousan, S.; Kuhnert, H.; Lohmann, G.; Kölling, M.; Pätzold, J.

    2012-04-01

    The northern Red Sea represents a unique location where ocean currents transport warm tropical waters northward, enabling coral reef growth at unusually high latitudes of up to 29 °N. Moreover, one of the world's northernmost complexes of uplifted Pleistocene reef terraces can be found here at Aqaba (Jordan). We present sub-seasonally resolved reconstructions of surface ocean conditions in the northern Red Sea derived from annually banded Porites corals. The Sr/Ca and δ18O variations in the aragonitic skeletons of our modern and fossil coral colonies provide proxy records of temperature, salinity and hydrologic balance at the sea surface during the last centuries and during time windows (40 to 100 years length) of the Holocene and the last interglacial period. Previous work has shown that seasonality and interannual to decadal climate variability in the northern Red Sea as documented in our coral records is strongly coupled to climate variations in the eastern Mediterranean, Middle East and Europe, reflecting the prominent role of atmospheric teleconnections of the Arctic Oscillation (AO)/North Atlantic Oscillation (NAO) in controlling regional climate on these timescales. New coral Sr/Ca data, in combination with δ18O, reveal an abrupt regime shift toward fresher surface ocean conditions in northern Red Sea surface waters at the end of the Little Ice Age. Possible mechanisms include a re-organization of the Northern Hemisphere atmospheric circulation. Sr/Ca records from a large number of fossil corals indicate a trend of decreasing temperature seasonality over the last 6000 years toward present-day. Such a trend is expected in the higher latitudes of the Northern Hemisphere from insolation changes on orbital timescales. Coral δ18O and Sr/Ca records suggest an increased seasonality in the hydrologic balance during time intervals around 4400, 4600 and 6000 years ago, which could result from both enhanced winter evaporation or increased summer precipitation

  19. Abrupt climate-triggered lake ecosystem changes recorded in late glacial lake sediments in northern Poland

    Science.gov (United States)

    Slowinski, M. M.; Zawiska, I.; Ott, F.; Noryskiewicz, A. M.; Apolinarska, K.; Lutynska, M.; Michczynska, D. J.; Brauer, A.; Wulf, S.; Skubala, P.; Blaszkiewicz, M.

    2013-12-01

    The aim of this study was to better understand how local lake ecosystems responded to abrupt climate changes through applying multi-proxy sediment analyses. Therefore, we carried out a detailed and high-resolution case study on the late glacial sediment from the Trzechowskie palaeolake located in the eastern part of the Pomeranian Lakeland, northern Poland. We reconstructed climate induced environmental changes in the paleolake and its catchment using biotic proxies (macrofossils, pollen, cladocera, diatoms, oribatidae mite) and classical geochemical proxies (δ18O, δ13C, loss-on-ignition, CaCO3 content) in combination with high-resolution μ-XRF element core scanning. The core chronology has been established by means of biostratigraphy, AMS 14C-dating on plant macro remains, varve counting in laminated intervals and tephrochronology. The latter was possible by the discovery of the late Allerød Laacher See Tephra for the first time at such eastern location. Biogenic accumulation in the lake started rather late during the lateglacial interstadial at 13903×170 cal yrs BP. The rapid and pronounced cooling at the beginning of the Younger Dryas had a major impact on the lake and its catchment as clearly reflected by both, biotic and geochemical proxies. The depositional environment of the lake abruptly changed from a varved to massive gytjia. The pronounced warming at the demise of Younger Dryas cooling is well-reflected in all environmental indicators but with conspicuous leads and lags reflecting complex responses of lake ecosystems to climate warming. The research was supported by the National Science Centre Poland - NN306085037. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association.

  20. Tropical Pacific climate variability over the last 6000 years as recorded in Bainbridge Crater Lake, Galápagos

    Science.gov (United States)

    Thompson, Diane M.; Conroy, Jessica L.; Collins, Aaron; Hlohowskyj, Stephan R.; Overpeck, Jonathan T.; Riedinger-Whitmore, Melanie; Cole, Julia E.; Bush, Mark B.; Whitney, H.; Corley, Timothy L.; Kannan, Miriam Steinitz

    2017-08-01

    Finely laminated sediments within Bainbridge Crater Lake, Galápagos, provide a record of El Niño-Southern Oscillation (ENSO) events over the Holocene. Despite the importance of this sediment record, hypotheses for how climate variability is preserved in the lake sediments have not been tested. Here we present results of long-term monitoring of the local climate and limnology and a revised interpretation of the sediment record. Brown-green, organic-rich, siliciclastic laminae reflect warm, wet conditions typical of El Niño events, whereas carbonate and gypsum precipitate during cool, dry La Niña events and persistent dry periods, respectively. Applying this new interpretation, we find that ENSO events of both phases were generally less frequent during the mid-Holocene ( 6100-4000 calendar years B.P.) relative to the last 1500 calendar years. Abundant carbonate laminations between 3500 and 3000 calendar years B.P. imply that conditions in the Galápagos region were cool and dry during this period when the tropical Pacific E-W sea surface temperature (SST) gradient likely strengthened. The frequency of El Niño and La Niña events then intensified dramatically around 1750-2000 calendar years B.P., consistent with a weaker SST gradient and an increased frequency of ENSO events in other regional records. This strong interannual variability persisted until 700 calendar years B.P., when ENSO-related variability at the lake decreased as the SST gradient strengthened. Persistent, dry conditions then dominated between 300 and 50 calendar years B.P. (A.D. 1650-1900, ± 100 years), whereas wetter conditions and frequent El Niño events dominated in the most recent century.

  1. The climatic signal recorded in Sc\\varisoara Ice Cave (Apuseni Mountains, Romania) during the last millennium

    Science.gov (United States)

    Bǎdǎlutǎ, Carmen-Andreea; Persoiu, Aurel

    2016-04-01

    The climatic signal recorded by proxy indicators in ice caves can provide valuable information on environmental changes during the Holocene. One of the best-known sites for climate and environmental reconstructions in Romania is Sc\\varisoara Ice Cave (Apuseni Mountains), which hosts the largest and oldest cave ice accumulation in the world. In this paper we present the variations of mid-autumn through mid-winter air temperature for the last 1000 years, as recorded by the isotopic composition of oxygen and hydrogen in the underground ice body in Sc\\varisoara Ice Cave. We have extracted a 10 m long, 10 cm diameter, ice core and measured the stable isotopes of oxygen and hydrogen along the length of the core. Six radiocarbon dates provide the chronological control of the profile. The data set shows differences in δ¹⁸O (δ2H show similar variations and is not discussed) between the Medieval Warm Period (MWP) and Little Ice Age (LIA), with lower values between 1857-1805 and 1771-1592, and the minimum recorded in 1848 (δ¹⁸O =-12.5‰). This period was cold, with dry winters. In opposition, in the MWP, we have observed an increase in δ¹⁸O values, whit the maximum recorded in 1003 (δ¹⁸O =-7.7‰). At its height, the MWP extended from 1003 to 1131. D-excess values for the same period show both rapid changes in the source of precipitation, between Atlantic and Mediterranean ones, as well as a predominance of the positive NAO phase during the MWP and a somewhat erratic ANO behavior during the subsequent LIA. Acknowledgements. The research leading to these results has received funding from EEA Financial Mecanism 2009 - 2014 under the project contract no 18SEE.

  2. Late Glacial-Holocene climatic transition record at the Argentinian Andean piedmont between 33–34° S

    Directory of Open Access Journals (Sweden)

    A. E. Mehl

    2013-10-01

    Full Text Available The Arroyo La Estacada (~33°28' S, 69°02' W, eastern Andean piedmont of Argentina, cuts through an extensive piedmont aggradational unit composed of a dominant late Pleistocene–early Holocene (LP–EH alluvial sequence including several paleosols. The arroyo sedimentary record exhibits a paleosol developed affecting the topmost part of likely Lateglacial aeolian deposits aggraded into a floodplain environment by the end of the late Pleistocene. The paleosol shows variable grade of development in the outcrops along the arroyo probably in relation to fluvial valley paleotopography. Organic matter humification, carbonate accumulation and redox processes were the dominant processes associated with paleosol formation. By the early Holocene, when the formation of the paleosol ended, alluvial aggradation renewed and a higher frequency of flooding events could have affected the arroyo's floodplain environment. A period of relative landscape stability in the Arroyo La Estacada basin is inferred from the paleosol developed by the LP–EH transition in response to a climatic amelioration in the Andes cordillera piedmont after the Late Glacial arid conditions. The renewal of early Holocene alluvial aggradation was probably influenced by the South American Monsoon and resulted in a change in the sedimentary dynamics of the arroyo. The analyzed Late Glacial-Holocene alluvial record of the Andean piedmont constitutes a suitable record of the LP–EH climatic transition at the extra Andean region of Argentina. It is in agreement with regional paleoclimatic evidence along the southern tip of the South American continent, where other sedimentary sequences record similar late Quaternary paleoenvironmental changes over both fluvial and interfluvial areas.

  3. Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

    Science.gov (United States)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

    2012-12-01

    The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87

  4. Late Glacial and Early Holocene Climatic Changes Based on a Multiproxy Lacustrine Sediment Record from Northeast Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Kokorowski, H D; Anderson, P M; Sletten, R S; Lozhkin, A V; Brown, T A

    2008-05-20

    Palynological (species assemblage, pollen accumulation rate), geochemical (carbon to nitrogen ratios, organic carbon and biogenic silica content), and sedimentological (particle size, magnetic susceptibility) data combined with improved chronology and greater sampling resolution from a new core from Elikchan 4 Lake provide a stronger basis for defining paleoenvironmental changes than was previously possible. Persistence of herb-dominated tundra, slow expansion of Betula and Alnus shrubs, and low percentages of organic carbon and biogenic silica suggest that the Late-Glacial transition (ca. 16,000-11,000 cal. yr BP) was a period of gradual rather than abrupt vegetation and climatic change. Consistency of all Late-Glacial data indicates no Younger Dryas climatic oscillation. A dramatic peak in pollen accumulation rates (ca. 11,000-9800 cal. yr BP) suggests a possible summer temperature optimum, but finer grain-sizes, low magnetic susceptibility, and greater organic carbon and biogenic silica, while showing significant warming at ca. 11,000 cal. yr BP, offer no evidence of a Holocene thermal maximum. When compared to trends in other paleo-records, the new Elikchan data underscore the apparent spatial complexity of climatic responses in Northeast Siberia to global forcings between ca. 16,000-9000 cal. yr BP.

  5. Holocene dinoflagellate cyst record of climate and marine primary productivity change in the Santa Barbara Basin, southern California.

    Science.gov (United States)

    Pospelova, Vera; Mertens, Kenneth N.; Hendy, Ingrid, L.; Pedersen, Thomas F.

    2015-04-01

    High-resolution sedimentary records of dinoflagellate cysts and other marine palynomorphs from the Santa Barbara Basin (Ocean Drilling Program Hole 893A) demonstrate large variability of primary productivity during the Holocene, as the California Current System responded to climate change. Throughout the sequence, dinoflagellate cyst assemblages are characterized by the dominance of cysts produced by heterotrophic dinoflagellates, and particularly by Brigantedinium, accompanied by other upwelling-related taxa such as Echinidinium and cysts of Protoperidinium americanum. During the early Holocene (~12-7 ka), the species richness is relatively low (16 taxa) and genius Brigantedinium reaches the highest relative abundance, thus indicating nutrient-rich and highly productive waters. The middle Holocene (~7-3.5 ka) is characterized by relatively constant cyst concentrations, and dinoflagellate cyst assemblages are indicative of a slight decrease in sea-surface temperature. A noticeable increase and greater range of fluctuations in the cyst concentrations during the late Holocene (~3.5-1 ka) indicate enhanced marine primary productivity and increased climatic variability, most likely related to the intensification of El Niño-like conditions. Keywords: dinoflagellate cysts, Holocene, North Pacific, climate, primary productivity.

  6. Extracting Past Climate and Local Sea Level Change from the Geologic Record of Coastal Sediment Transport in The Bahamas

    Science.gov (United States)

    Dyer, B.; D'Andrea, W. J.; Sandstrom, R. M.; Rovere, A.; Lorscheid, T.; Casella, E.; Raymo, M. E.

    2016-12-01

    Detailed reconstructions of past interglacial Earth climate provide a baseline to differentiate natural variability from human caused change and can reveal feedbacks that may become fundamental in predicting future climate change. In the last interglacial period (marine isotope stage 5e; MIS 5e - 128 to 116 kyr BP), global mean sea level was up to 6-9 meters higher than today, and greenhouse gases were similar to pre-industrial levels. If these observations are valid, they suggest that current sea level may be primed for sudden and drastic change. However, the exact elevation of global sea level during MIS 5e, and the rates of change during that interglacial are complicated by incomplete chronologies in the geologic record and uncertainties in local isostatic or tectonic adjustment of these records since deposition. The Bahamian archipelago consists of several isolated, shallow carbonate platforms that are tectonically stable and may record a relatively straightforward history of past interglacial sea level. The rocky islands on the eastern margins of the platforms are composed of carbonate sediments arranged in coast-parallel and V-shaped coast-perpendicular ridges as high as 20-30 meters above modern sea level. There is a lack of scientific consensus as to whether these sediments were deposited by the ocean during an interval of higher sea level (MIS 5e or 11), or if the ridges are aeolian carbonate dunes. We scan hand samples from these deposits and develop image segmentation code to isolate individual grains. With this dataset, we quantify the relative arrangement of grain sizes and shapes to objectively identify evidence of aeolian depositional features such as the inverse grading of ripple sets. Additionally, the modern average wind direction in the Bahamas aligns with the observed orientation of V-shaped ridges across the archipelago within 10 degrees. Remarkably, there are very few active dunes in the Bahamas today, which raises an important discussion on

  7. Improved sea level record over the satellite altimetry era (1993–2010 from the Climate Change Initiative Project

    Directory of Open Access Journals (Sweden)

    M. Ablain

    2014-08-01

    Full Text Available Sea level is one of the 50 Essential Climate Variables (ECVs listed by the Global Climate Observing System (GCOS in climate change monitoring. In the last two decades, sea level has been routinely measured from space using satellite altimetry techniques. In order to address a number of important scientific questions such as: "Is sea level rise accelerating?", "Can we close the sea level budget?", "What are the causes of the regional and interannual variability?", "Can we already detect the anthropogenic forcing signature and separate it from the internal/natural climate variability?", and "What are the coastal impacts of sea level rise?", the accuracy of altimetry-based sea level records at global and regional scales needs to be significantly improved. For example, the global mean and regional sea level trend uncertainty should become better than 0.3 and 0.5 mm year−1, respectively (currently of 0.6 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 respective data improvements achieved within the European Space Agency (ESA Climate Change Initiative (ESA CCI project on "Sea Level" during its first phase (2010–2013, using multi-mission satellite altimetry data over the 1993–2010 time span. In a first step, using a new processing system with dedicated algorithms and adapted data processing strategies, an improved set of sea level products has been produced. The main improvements include: reduction of orbit errors and wet/dry atmospheric correction errors, reduction of instrumental drifts and bias, inter-calibration biases, intercalibration between missions and combination of the different sea level data sets, and an improvement of the reference mean sea surface. We also present preliminary independent validations of the SL_cci products, based on tide gauges comparison and sea level budget closure approach

  8. Rapid climatic shifts and its influence on ancient civilisations: Evidence from marine records

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    in the densely populated South Asian region. Studies on the variability of the SW monsoon for the last 19,000 years before present (BP) by using marine sediment records reveal that the SW monsoon started its intensification from 12,000 years BP after a weak phase...

  9. Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions

    Science.gov (United States)

    Steinthorsdottir, Margret; Wohlfarth, Barbara; Kylander, Malin E.; Blaauw, Maarten; Reimer, Paula J.

    2013-05-01

    A new stomatal proxy-based record of CO2 concentrations ([CO2]), based on Betula nana (dwarf birch) leaves from the Hässeldala Port sedimentary sequence in south-eastern Sweden, is presented. The record is of high chronological resolution and spans most of Greenland Interstadial 1 (GI-1a to 1c, Allerød pollen zone), Greenland Stadial 1 (GS-1, Younger Dryas pollen zone) and the very beginning of the Holocene (Preboreal pollen zone). The record clearly demonstrates that i) [CO2] were significantly higher than usually reported for the Last Termination and ii) the overall pattern of CO2 evolution through the studied time period is fairly dynamic, with significant abrupt fluctuations in [CO2] when the climate moved from interstadial to stadial state and vice versa. A new loss-on-ignition chemical record (used here as a proxy for temperature) lends independent support to the Hässeldala Port [CO2] record. The large-amplitude fluctuations around the climate change transitions may indicate unstable climates and that “tipping-point” situations were involved in Last Termination climate evolution. The scenario presented here is in contrast to [CO2] records reconstructed from air bubbles trapped in ice, which indicate lower concentrations and a gradual, linear increase of [CO2] through time. The prevalent explanation for the main climate forcer during the Last Termination being ocean circulation patterns needs to re-examined, and a larger role for atmospheric [CO2] considered.

  10. Non-climatic signal in ice core records: lessons from Antarctic mega-dunes

    Directory of Open Access Journals (Sweden)

    A. Ekaykin

    2015-12-01

    Full Text Available We present the results of glaciological investigations in the mega-dune area located 30 km to the east from Vostok Station (central East Antarctica implemented during the 58th, 59th and 60th Russian Antarctic Expedition (January 2013–January 2015. Snow accumulation rate and isotope content (δD, δ18O and δ17O were measured along the 2 km profile across the mega-dune ridge accompanied by precise GPS altitude measurements and GPR survey. It is shown that the spatial variability of snow accumulation and isotope content covaries with the surface slope. The accumulation rate regularly changes by one order of magnitude within the distance −1. The full cycle of the dune drift is thus about 410 years. Since the spatial anomalies of snow accumulation and isotopic composition are supposed to drift with the dune, an ice core drilled in the mega-dune area would exhibit the non-climatic 410 year cycle of these two parameters. We simulated a vertical profile of snow isotopic composition with such a non-climatic variability, using the data on the dune size and velocity. This artificial profile is then compared with the real vertical profile of snow isotopic composition obtained from a core drilled in the mega-dune area. We note that the two profiles are very similar. The obtained results are discussed in terms of interpretation of data obtained from ice cores drilled beyond the mega-dune areas.

  11. Simulated Global Climatic Influences on the Record Wet UK Winter of2013-14

    Science.gov (United States)

    Maidens, A. V.; Knight, J.; Andrews, M.; Fereday, D.

    2014-12-01

    The winter of 2013-14 was an extreme one both in Europe and North America. In the UK, for instance, it was by far the wettest winter records dating back to 1910 and was also the wettest winter in the England and Wales precipitation record dating back to 1766. Furthermore, it was exceptionally stormy, with the highst numbers of stations recording gusts of over 60 knots since 1969. In the US, in contrast, winter 2013-14 was one of the coldest on record in parts of the Midwest with several states recording conditions in the coldest 10% since records began in 1895. The immediate cause of these highly anomalous conditions was the regional atmospheric circulation, with intense and persistent negative mean sea level pressure (mslp) anomalies over the North East Atlantic. The pattern of these anomalies resembles the positive phase of the North Atlantic Oscillation (NAO - with negative mslp over the mid- to high- latitude North Atlantic and positive mslp over the Sub-Tropics), with the addition of greater-than-usual troughing over Western Europe.Here, we will investigate the potential global atmospheric drivers of these highly anomalous conditions. Two putative mechanisms will be examined: firstly, the strong westerly phase of the quasi-biennial oscillation (QBO) that occurred in winter 2013-14, and secondly, an up-stream influence from the tropical West Pacific via the anomalous circulation patterns that caused the intensely cold winter conditions observed over North America. To test these hypotheses we utilise sets of seasonal-length reforecasts of the 14 winters in the period 1996-2009, with 3 members each year initialised on 1st November from ERAI reanalyses. In these experiments, we perform a linear relaxation of atmospheric winds and temperatures in (i) different parts of the stratosphere, (ii) over the Aleutian region, and (iii) over the tropical West Pacific, towards conditions observed in December-February 2013-14. In addition, we perform a control set without

  12. Mid-late Holocene climate and vegetation in northeastern part of the Altai Mountains recorded in Lake Teletskoye

    Science.gov (United States)

    Rudaya, Natalia; Nazarova, Larisa; Novenko, Elena; Babich, Valery; Kalugin, Ivan; Daryin, Andrei

    2015-04-01

    We report the first high-resolution (with intervals ca. 20-50 years) late-Holocene (4200 yr BP) pollen record from Lake Teletskoye, Altai Mountains, obtained from the underwater Ridge of Sofia Lepneva in 2006 (core Tel 2006). The study presents (i) the results of palynological analysis of Tel 2006; (ii) the results of spectral analysis of natural cycles based on the periodical fluctuation of taiga-biome curve; and (iii) quantitative reconstructions of the late-Holocene regional vegetation, woody coverage and climate in northern part of the Altai Mountains in order to define place of Northeast Altai on the map of the late-Holocene Central Asian environmental history. Late Holocene vegetation of the northeastern part of Altai recorded in Tel 2006 core is characterized by spread of dark-coniferous forest with structure similar to modern. Dominant trees, Siberian pine (Pinus sibirica) and Siberian fir (Abies sibirica), are the most ecological sensitive taxa between Siberian conifers (Shumilova, 1962), that as a whole suggests mild and humid climatic conditions during last 4200 years. However, changes of pollen taxa percentages and results of numerical analysis reveal pronounced fluctuation of climate and vegetation. Relatively cool and dry stage occurred prior to ca. 3500 cal yr BP. Open vegetation was widespread in the region with maximum deforestation and minimal July temperatures between 3800-3500 cal yr BP. Steppe-like communities with Artemisia, Chenopodiaceae and Cyperaceae could grow on the open sites around Lake Teletskoye. Reconstructed woody coverage is very low and varies between 29-35%. After ca. 3500 cal yr BP the area of dark-coniferous mountain taiga has significantly enlarged with maximums of woody coverages and taiga biome scores between ca. 2470-1040 cal yr BP. In the period of ~3500-2500 cal yr BP the averages July temperatures increased more than 1 0C. Climate became warmer and wetter. During last millennium (after 1040 cal yr BP) average July

  13. Accelerator Mass Spectrometry at Arizona: Geochronology of the Climatic Record and Connections with the Ocean

    Directory of Open Access Journals (Sweden)

    J.T. Jull

    2002-01-01

    Full Text Available There are many diverse uses of accelerator mass spectrometry (AMS. 14C studies at our laboratory include much research related to paleoclimate, with 14C as a tracer of past changes in environmental conditions as observed in corals, marine sediments, and many terrestrial records. Terrestrial records can also show the influence of oceanic oscillations, whether they are short term, such as ENSO (El Niño/Southern Oscillation, or on the millennial time scale. In tracer applications, we have developed the use of 129I as well as 14C as tracers for nuclear pollution studies around radioactive waste dump sites, in collaboration with IAEA. We discuss some applications carried out in Tucson, AZ, for several of these fields and hope to give some idea of the breadth of these studies.

  14. Accelerator mass spectrometry at Arizona: geochronology of the climate record and connections with the ocean.

    Science.gov (United States)

    Jull, A J T; Burr, G S; Beck, J W; Donahue, D J; Biddulph, D; Hatheway, A L; Lange, T E; McHargue, L R

    2003-01-01

    There are many diverse uses of accelerator mass spectrometry (AMS). Carbon-14 studies at our laboratory include much research related to paleoclimate, both with 14C as a tracer of past changes in environmental conditions as observed in corals, marine sediments and many terrestrial records. Terrestrial records such as forest fires can also show the influence of oceanic oscillations, whether they are short-term such as ENSO, or on the millennial time scale. In tracer applications, we have developed the use of 129I as well as 14C as tracers for nuclear pollution studies around radioactive waste dump sites, in collaboration with IAEA. We discuss some applications carried out in Tucson for several of these fields and hope to give some idea of the breadth of these studies.

  15. A Satellite-Based Surface Radiation Climatology Derived by Combining Climate Data Records and Near-Real-Time Data

    Directory of Open Access Journals (Sweden)

    Bodo Ahrens

    2013-09-01

    Full Text Available This study presents a method for adjusting long-term climate data records (CDRs for the integrated use with near-real-time data using the example of surface incoming solar irradiance (SIS. Recently, a 23-year long (1983–2005 continuous SIS CDR has been generated based on the visible channel (0.45–1 μm of the MVIRI radiometers onboard the geostationary Meteosat First Generation Platform. The CDR is available from the EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF. Here, it is assessed whether a homogeneous extension of the SIS CDR to the present is possible with operationally generated surface radiation data provided by CM SAF using the SEVIRI and GERB instruments onboard the Meteosat Second Generation satellites. Three extended CM SAF SIS CDR versions consisting of MVIRI-derived SIS (1983–2005 and three different SIS products derived from the SEVIRI and GERB instruments onboard the MSG satellites (2006 onwards were tested. A procedure to detect shift inhomogeneities in the extended data record (1983–present was applied that combines the Standard Normal Homogeneity Test (SNHT and a penalized maximal T-test with visual inspection. Shift detection was done by comparing the SIS time series with the ground stations mean, in accordance with statistical significance. Several stations of the Baseline Surface Radiation Network (BSRN and about 50 stations of the Global Energy Balance Archive (GEBA over Europe were used as the ground-based reference. The analysis indicates several breaks in the data record between 1987 and 1994 probably due to artefacts in the raw data and instrument failures. After 2005 the MVIRI radiometer was replaced by the narrow-band SEVIRI and the broadband GERB radiometers and a new retrieval algorithm was applied. This induces significant challenges for the homogenisation across the satellite generations. Homogenisation is performed by applying a mean-shift correction depending on the shift size of

  16. High resolution climate records from modern and last interglacial period derived from giant clam shells (Tridacnidae) from Sulawesi, Indonesia.

    Science.gov (United States)

    Arias Ruiz, Camilo; Elliot, Mary; Bezos, Antoine; Padoja, Kevin; Husson, Laurent; Michel, Elisabeth; La, Carole

    2017-04-01

    We studied Tridacnidae giant clams as environmental archives to reconstruct climate evolution in a region characterized by major ocean-atmosphere exchange on seasonal and inter-annual timescales: the Sulawesi archipelago. Using environmental proxies (18O and trace elements) we present reconstructions of inter-annual climate change derived from modern and past interglacial period (MIS 5). For fossil archive, U-Th ages were obtained from fossil coral samples from the same paleo-reef of Tridacna samples, because these bivalves exhibit an open system behavior in U-Th series. Comparison of a 18O profile derived from a 6 year old modern T. squamosa (2006-2012) and a predicted 18O profile derived from local temperature and salinity records confirms the isotopic equilibrium in shell deposition. The strong sea surface temperature (SST) anomaly of 2010 related to a strong La Niña was also recorded in the shell 18O signal. The modern 18O record presents a mean seasonal range of 0.5 ± 0.1 ‰. Additional trace element analyses show that Mg/Ca and Sr/Ca are also temperature dependent in this species and appear less affected by changes in salinity/rainfall. Finally, Ba/Ca ratio appears to reflect both primary production related to coastal up-welling during the dry season, and continental run-off during the wet season. Trace element profiles also exhibit strong anomalies reflecting changes in local hydrography related to the 2010 La Niña. The ages of the Tridacna fossils derived from U-Th dating are around last interglacial MIS-5 period. 18O records derived from a fossil Tridacna gigas specimen provide a time-window of 14 years. The record shows a reduced mean seasonal range of 18O of around 0.4±0.2 ‰. Absence of Ba/Ca peaks during the wet season suggest a weakened monsoon rainfall activity, but the presence during the dry season suggests a persistent seasonal up-welling at this time. Our study illustrates the usefulness of Tridacnidae fossils in

  17. A High Resolution Record of Recent Climate Change From Isla Isabela in the Gulf of California

    Science.gov (United States)

    Englebrecht, A.; Ingram, L.; Byrne, R.; Kienel, U.; Boehnel, H.; Haug, G.

    2007-05-01

    Here we report on the stable isotopic composition (oxygen and carbon) and pollen content of seasonally laminated lake sediments from Isla Isabela (21°52' N, 105°54' W) to reconstruct the history of recent climate change in northwestern Mexico. Isabela crater lake is located approximately 30km offshore the state of Nayarit, and is in the precipitation region of the Mexican Monsoon (also called North American Monsoon). Work on an initial short core indicates coherent periodicities in δ13C and δ18O of bulk inorganic carbonate throughout the past two centuries. Most notably, strong excursions in δ13C and observable sedimentological changes occur at depths in the core corresponding to the years 1973-74, 1950s, 1860s, 1810s, and 1780s A.D.-recognized periods of historical drought in Mexico. Further downcore work reveals additional periods of reduced water availability that may correspond to variations in the Mexican Monsoon.

  18. Non-climatic signal in ice core records: lessons from Antarctic megadunes

    Science.gov (United States)

    Ekaykin, Alexey; Eberlein, Lutz; Lipenkov, Vladimir; Popov, Sergey; Scheinert, Mirko; Schröder, Ludwig; Turkeev, Alexey

    2016-06-01

    We present the results of glaciological investigations in the megadune area located 30 km to the east of Vostok Station (central East Antarctica) implemented during the 58th, 59th and 60th Russian Antarctic Expedition (January 2013-2015). Snow accumulation rate and isotope content (δD, δ18O and δ17O) were measured along the 2 km profile across the megadune ridge accompanied by precise GPS altitude measurements and ground penetrating radar (GPR) survey. It is shown that the spatial variability of snow accumulation and isotope content covaries with the surface slope. The accumulation rate regularly changes by 1 order of magnitude within the distance negative correlation with the snow accumulation. Analysing dxs / δD and 17O-excess / δD slopes (where dxs = δD - 8 ṡ δ18O and 17O-excess = ln(δ17O / 1000 + 1) -0.528 ṡ ln (δ18O / 1000 + 1)), we conclude that the spatial variability of the snow isotopic composition in the megadune area could be explained by post-depositional snow modifications. Using the GPR data, we estimated the apparent dune drift velocity (4.6 ± 1.1 m yr-1). The full cycle of the dune drift is thus about 410 years. Since the spatial anomalies of snow accumulation and isotopic composition are supposed to drift with the dune, a core drilled in the megadune area would exhibit the non-climatic 410-year cycle of these two parameters. We simulated a vertical profile of snow isotopic composition with such a non-climatic variability, using the data on the dune size and velocity. This artificial profile is then compared with the real vertical profile of snow isotopic composition obtained from a core drilled in the megadune area. We note that the two profiles are very similar. The obtained results are discussed in terms of interpretation of data obtained from ice cores drilled beyond the megadune areas.

  19. Planktonic Foraminifera as Sensitive Recorders of Climate Variability in the Eastern Mediterranean During the Last ~90 ka

    Science.gov (United States)

    Almogi-Labin, A.; Bar-Matthews, M.; Ayalon, A.; Paterne, M.

    2014-12-01

    Planktonic foraminifera (PF) are widely used in Quaternary paleoceanography as carriers of oxygen stable isotope signal. This signal is one of the main tools for establishing chronostratigraphy and determining the nature of global and local glacial and interglacial cycles. In this study, the focus is on the PF assemblages which are sensitive recorders of climate and water column properties including the degree of water column stratification and trophic levels. In order to reconstruct the climate variability of the last ~90 ka, core MDVAL9501 (980 m water depth), taken by R/V Marion Dufresnae, SE of Cyprus, was studied. A δ18O-Globigerinoides ruber stratigraphy was established and correlated with well-dated (U/Th) speleothem records of Soreq Cave and radiocarbon dates. The sedimentary record in this core covers the last ~90ka. Variations in PF assemblage composition indicate that conditions shifted between two main climatic scenarios. During the last glacial cooler, more aerated, less stratified and more mesotrophic water column persisted with distinct seasonality. This is evident from the occurrence of two deep water dwellers Globorotalia inflata being abundant from 75 to 50 ka BP and G. scitula from 55 to 15 ka BP (with respective SST of 15-16 ºC and 11-13 ºC) and accompanied continuously by the cold water species Neogloboqudrina pachyderma and Globigerina bulloides. Among the "warm" water species G. ruber is nearly the only "survivor" during the glacial period comprising 25-50% of the assemblage with lower values corresponding to minima in D-O events. During Holocene, water column was warmer, more stratified, mostly oligotrophic with reduced seasonality. The dominating species were G. ruber and other "warm" water species comprising >75% of the assemblage and occurring in low numbers. An exception are sapropel S1 (early Holocene) and S3 (MIS 5.1) periods, when lower δ18O and highest TOC values prevail with significantly increased numerical abundance of PF

  20. Correlation between high-resolution climate records from a Nanjing stalagmite and GRIP ice core during the last glaciation

    Institute of Scientific and Technical Information of China (English)

    WANG; Yongjin

    2001-01-01

    [1]Dansgaard, W., Clausen, H. B., Gundestrup, N. et al., A new Greenland deep ice core, Science, 1982, 218: 1273.[2]Dansgaard, W., Johnsen, S. J., Clausen, H. B. et al., Evidence for general instability of past climate from a 250-Kyr ice-core record, Nature, 1993, 364: 218.[3]Bond, G. C., Broecker, W. S., Johnsen, S. J. et al., Correlation between climate records from North Atlantic sediments and Greenland ice, Nature, 1993, 365: 143.[4]Bond, G. C., Lotti, R., Iceberg discharges into the North Atlantic on millennial time scales during the last glaciation, Science, 1995, 267: 1005.[5]Kotilainen, A. T., Shackleton, N. J., Rapid climate variability in the North Pacific Ocean during the past 950 000 years, Nature, 1995, 267: 323.[6]Lowell, T. V., Heusser, C. J., Sandensrn, B. G. et al., Interhemispheric correlation of late Pleistocene glacial events, Science, 1995, 269: 1541.[7]Porter, S. C., An, Z. S., Correlation between climate events in the North Atlantic and China during the last glaciation, Nature, 1995, 375: 305.[8]Guo, Z. T., Liu, T. S., Wu, N. Q. et al., Heinrich-rhythem pulses of climate recorded in loess of the last two glaciations, Quaternary Science (in Chinese), 1996, (1): 21.[9]Lu, H. Y., Guo, Z. T., Wu, N. Q., Paleomonsoon evolution and Heinrich events: evidences from the Loess Plateau and the South China Sea, Quaternary Science (in Chinese), 1996, (1): 11.[10]Zhang, M. L., Yuan, D. X., Lin, Y. S., Isotopic ages and its paleoclimate significance of a stalagmite from Xiangshui Cave in Guangyang County, Guangxi Province, Carsologica Sinica (in Chinese), 1998, 17(4): 311.[11]Edwards, R. L., Chen, J. H., Wasserburg, G. J., 238U-234U-230Th-232Th systematic and precise measurement of time over the past 500 000 years, Earth and Planetary Science Letter, 1986/1987, 81: 175.[12]McCrea, J. M., The isotopic Chemistry of carbonates and a paleotemperature-scale, Journal of Chemical Physics, 1950, 18: 849.[13

  1. Spatial-temporal analysis on climate variation in early Qing dynasty (17th -18th century) using China's chronological records

    Science.gov (United States)

    Lin, Kuan-Hui Elaine; Wang, Pao-Kuan; Fan, I.-Chun; Liao, Yi-Chun; Liao, Hsiung-Ming; Pai, Pi-Ling

    2016-04-01

    Global climate change in the form of extreme, variation, and short- or mid-term fluctuation is now widely conceived to challenge the survival of the human beings and the societies. Meanwhile, improving present and future climate modeling needs a comprehensive understanding of the past climate patterns. Although historical climate modeling has gained substantive progress in recent years based on the new findings from dynamical meteorology, phenology, or paleobiology, less known are the mid- to short-term variations or lower-frequency variabilities at different temporal scale and their regional expressions. Enabling accurate historical climate modeling would heavily rely on the robustness of the dataset that could carry specific time, location, and meteorological information in the continuous temporal and spatial chains. This study thus presents an important methodological innovation to reconstruct historical climate modeling at multiple temporal and spatial scales through building a historical climate dataset, based on the Chinese chronicles compiled in a Zhang (2004) edited Compendium of Chinese Meteorological Records of the Last 3,000 Years since Zhou Dynasty (1100BC). The dataset reserves the most delicate meteorological data with accurate time, location, meteorological event, duration, and other phonological, social and economic impact information, and is carefully digitalized, coded, and geo-referenced on the Geographical Information System based maps according to Tan's (1982) historical atlas in China. The research project, beginning in January 2015, is a collaborative work among scholars across meteorology, geography, and historical linguistics disciplines. The present research findings derived from the early 100+ years of the Qing dynasty include the following. First, the analysis is based on the sampling size, denoted as cities/counties, n=1398 across the Mainland China in the observation period. Second, the frequencies of precipitation, cold

  2. An Analysis of Historical Records of Solar Variability, Volcanic Eruptions, and Climate Change in the Last Millennium

    Science.gov (United States)

    Pang, K. D.

    2003-12-01

    Studying past climate changes can help us better understand present natural variations and predict future trends. However, various reconstructions of the climate of the last 1000 years have given only broad similarities [Briffa, JGR 106, 2929, 2001]. The variances are partly due to uncertainties in the past radiative and aerosol forcing, and gaps in regional coverage. Another outstanding question is whether we are in a time similar to the Medieval Warm Period. From the frequencies of sunspot and aurora sightings, abundance of carbon-14 in the rings of long-lived trees, and beryllium-10 in the annual layers of polar ice cores, we have reconstructed the recent history of a variable Sun. In the past 1800 years the Sun has gone through nine cycles of changes in brightness. While these long-term changes account for less than 1% of the total irradiance, there is clear evidence that they affect the climate [Pang and Yau, Eos, 83, No. 43, 481, 2002]. We have analyzed Chinese historical weather records to fill the data void in this region. Reports of unseasonable cold are classified by the degree of severity: (1) Late (April-June) or early (July-Sept) killing frosts; (2) Bitter cold/heavy snowfall; and (3) heavy sustained snowfall, bitter cold with frozen wells, lakes, rivers, and icebound seas. The latter cases were often widespread and multi-year. All categories occurred most frequently during the coldest part of the Little Ice Age, with the coldest episodes in 1652-54, 1656, 1664, 1670-72, 1676-77, 1683, 1688-91, 1716 and 1718-19. They thus coincide with Maunder Minimum (1645-1715), when very few sunspots were seen-about one in ten years from China or Europe-indicative of a weakened Sun. There was only one Category 3 episode between the Maunder and Dalton Minima-in 1761, and two in the Dalton Minimum (1795-1825)-in 1796 and 1814-7. Analysis of proxy data has shown that the 1810's were among the coldest years in Europe [Briffa and Jones, in ``The Year Without a Summer

  3. Can a climate record be extracted from giant sequoia tree rings?

    OpenAIRE

    Hughes, M. K.; Richards, B J; Swetnam, T. W.; Baisan, C.H.

    1990-01-01

    Extreme low growth events in giant sequoia ring-width index series coincide with severe droughts in the San Joaquin drainage, on whose eastern flank the sequoia groves stand. Comparison with a network of 102 largely moisture-sensitive tree-ring chronologies from western North America suggests that this relationship has been stable for at least 380 years. The twentieth century is not unusual in the frequency of these events. We expect the growth record will soon be replicated for over 2000 yea...

  4. Middle Pleistocene climate variations south off Greenland: the Marine Isotope Stage 9 to 15 record of IODP Site U1305

    Science.gov (United States)

    Voelker, Antje; Ventura, Cristina; de Vernal, Anne; Teboulle, Oury; Henry, Maryse; de Abreu, Lucia; Hillaire-Marcel, Claude

    2016-04-01

    As a region where deep-water convection occurs, the Labrador Sea is a key area to study the impact of climate change on the North Atlantic's subpolar gyre and subsequently the thermohaline circulation itself. IODP Site U1305 (57.5°N, 48.5°W) was retrieved from the Eirik ridge at a water depth of 3460 m. At this Site activity of the Western Boundary Undercurrent (WBUC) led to higher sedimentation rates during interglacial periods (Hillaire-Marcel et al., 2011 in Mar. Geol.) making it ideal to study interglacial climate variability. With its position south of the polar front, it is mostly influenced by the warmer, saline Irminger Current waters and reflects conditions in the "inner" Labrador Sea. In order to evaluate the inner Labrador Sea's response to climate change during the mid-Brunhes interval from Marine Isotope Stage (MIS) 9 to 15a (315-570 ka) we generated centennial-scale proxy records reflecting surface (dinocyst assemblage derived), subsurface (N. pachyderma isotope and abundance data) and deep water (benthic isotope data) conditions. In addition, the abundance of lithic fragments >150μm indicates ice-rafting episodes. In the inner Labrador Sea, ice-rafting events coincided with lower sea-surface salinities (SSS) and are restricted to the glacial periods of MIS 14, 12 and 10 as well as the stadial periods during the MIS 11 to MIS 10 transition. Climate variability during the three interglacial periods varied significantly. MIS 9e recorded the influence of Irminiger Current waters with a reduced number of N. pachyderma and SSS close to 35. The high abundance of the pelagic diatom species Coscinodiscus during the late deglaciation and the onset of the interglacial period confirms the presence of Atlantic waters in the vicinity of Site U1305. Climate during MIS 11c can be dived into three phases. During the deglaciation of MIS 12 and the onset of the MIS 11c (420-430 ka) surface water conditions were very variable with frequent incursions of polar (cold

  5. Glacial to Holocene climate changes in the SE Pacific. The Raraku Lake sedimentary record (Easter Island, 27°S)

    Science.gov (United States)

    Sáez, Alberto; Valero-Garcés, Blas L.; Giralt, Santiago; Moreno, Ana; Bao, Roberto; Pueyo, Juan J.; Hernández, Armand; Casas, David

    2009-12-01

    Easter Island (SE Pacific, 27°S) provides a unique opportunity to reconstruct past climate changes in the South Pacific region based on terrestrial archives. Although the general climate evolution of the south Pacific since the Last Glacial Maximum (LGM) is coherent with terrestrial records in southern South America and Polynesia, the details of the dynamics of the shifting Westerlies, the South Pacific Convergence Zone and the South Pacific Anticyclone during the glacial-interglacial transition and the Holocene, and the large scale controls on precipitation in tropical and extratropical regions remain elusive. Here we present a high-resolution reconstruction of lake dynamics, watershed processes and paleohydrology for the last 34 000 cal yrs BP based on a sedimentological and geochemical multiproxy study of 8 cores from the Raraku Lake sediments constrained by 22 AMS radiocarbon dates. This multicore strategy has reconstructed the sedimentary architecture of the lake infilling and provided a stratigraphic framework to integrate and correlate previous core and vegetation studies conducted in the lake. High lake levels and clastic input dominated sedimentation in Raraku Lake between 34 and 28 cal kyr BP. Sedimentological and geochemical evidences support previously reported pollen data showing a relatively open forest and a cold and relatively humid climate during the Glacial period. Between 28 and 17.3 cal kyr BP, including the LGM period, colder conditions contributed to a reduction of the tree coverage in the island. The coherent climate patterns in subtropical and mid latitudes of Chile and Eastern Island for the LGM (more humid conditions) suggest stronger influence of the Antarctic circumpolar current and an enhancement of the Westerlies. The end of Glacial Period occurred at 17.3 cal kyr BP and was characterized by a sharp decrease in lake level conducive to the development of major flood events and erosion of littoral sediments. Deglaciation (Termination

  6. Eastern Andean environmental and climate synthesis for the last 2000 years BP from terrestrial pollen and charcoal records of Patagonia

    Science.gov (United States)

    Sottile, G. D.; Echeverria, M. E.; Mancini, M. V.; Bianchi, M. M.; Marcos, M. A.; Bamonte, F. P.

    2015-06-01

    The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation system that dominates the dynamics of Southern Hemisphere mid-latitude climate. Little is known about climatic changes in the Southern South America in comparison to the Northern Hemisphere due to the low density of proxy records, and adequate chronology and sampling resolution to address environmental changes of the last 2000 years. Since 2009, new pollen and charcoal records from bog and lakes in northern and southern Patagonia at the east side of the Andes have been published with an adequate calibration of pollen assemblages related to modern vegetation and ecological behaviour. In this work we improve the chronological control of some eastern Andean previously published sequences and integrate pollen and charcoal dataset available east of the Andes to interpret possible environmental and SWW variability at centennial time scales. Through the analysis of modern and past hydric balance dynamics we compare these scenarios with other western Andean SWW sensitive proxy records for the last 2000 years. Due to the distinct precipitation regimes that exist between Northern (40-45° S) and Southern Patagonia (48-52° S) pollen sites locations, shifts on latitudinal and strength of the SWW results in large changes on hydric availability on forest and steppe communities. Therefore, we can interpret fossil pollen dataset as changes on paleohydric balance at every single site by the construction of paleohydric indices and comparison to charcoal records during the last 2000 cal yrs BP. Our composite pollen-based Northern and Southern Patagonia indices can be interpreted as changes in latitudinal variation and intensity of the SWW respectively. Dataset integration suggest poleward SWW between 2000 and 750 cal yrs BP and northward-weaker SWW during the Little Ice Age (750-200 cal yrs BP). These SWW variations are synchronous to Patagonian fire activity major shifts. We found an in phase

  7. Late Pliocene climate change 3.4-2.3 Ma: paleoceanographic record from the Yabuta Formation, Sea of Japan

    Science.gov (United States)

    Cronin, T. M.; Kitamura, A.; Ikeya, Noriyuki; Watanabe, M. E.; Kamiya, T.

    1994-01-01

    Late Pliocene paleoceanographic changes in the Sea of Japan between 3.4 and2.3 Ma were investigated through study of molluscs, diatoms, and ostracodes from the Yabuta Formation in Toyama Prefecture. The period 3.4-2.7 Ma was characterized by relatively high sea level and cool water benthic faunas. A progressive paleoceanographic shift towards colder oceanic conditions and lower sea level occurred beginning near 2.7 Ma, intenifying about 2.5 Ma, when important changes in ostracode and molluscan faunas occurred. Between 2.7 and 2.3 Ma, eight glacial events can be inferred based on drops in sea level of 50-60 m and increasing proportions of cold, shallow water ostracode species whose modern ecology and zoogeography indicate colder winter water temperatures (3-4??C). The glacial events between 2.5 and 2.3 Ma were the most intense. Preliminary interpretation of the faunal and oceanographic events of the Yabuta Formation suggests that they correspond to Northern Hemispheric cooling also known from North Atlantic deep-sea oxygen isotope, IRD, and planktic foraminiferal records, North Pacific diatom and radiolarian record, and the Chinese loess sequences. The eight glacial events may record a 41,000-yr obliquity cycle which characterized other late Pliocene climate proxy records. Inferred sea level drops near 2.5-2.3 Ma of about 50-60 m provide direct evidence from an ocean margin setting that supports deep sea oxygen isotopic evidence indicating major changes in global ice volume changes. ?? 1994.

  8. Late-glacial and Holocene record of vegetation and climate from Cynthia Bay, Lake St Clair, Tasmania

    Science.gov (United States)

    Hopf, F. V. L.; Colhoun, E. A.; Barton, C. E.

    2000-10-01

    A Late-glacial-Holocene pollen record was obtained from a 3.96 m sediment core taken from Lake St Clair, central Tasmania. Modern vegetation and pollen analyses formed the basis for interpretation of the vegetation and climate history. Following deglaciation and before ca. 18450 yr BP Podocarpus lawrencei coniferous heath and Astelia-Plantago wet alpine herbfield became established at Lake St Clair. A distinct Poaceae-Plantago peak occurs between 18450 and 11210 yr BP and a mean annual temperature depression from ca. 6.2°C to 3°C below present is inferred for this period. The marked reduction in Podocarpus and strong increase of Poaceae suggests reduced precipitation levels during the period of widespread deglaciation (ca. 18.5-11 kyr BP). The local Late Pleistocene-Holocene non-forest to forest biostratigraphical boundary is dated at 11.2 kyr BP. It is characterised by expansion of the subalpine taxa Athrotaxis/Diselma with Nothofagus gunnii, and by the establishment of Nothofagus cunninghamii with Eucalyptus spp. A Phyllocladus bulge prior to the expansion of Nothofagus cunninghamii, reported at other Tasmanian sites, is not present at Lake St Clair. Nothofagus cunninghamii cool temperate rainforest peaked at 7800 yr BP, probably under wetter climatic conditions than present. The maximum development of rainforest in the early-middle Holocene may indicate that the temperature was slightly warmer than present, but the evidence is not definitive. The expansion of Eucalyptus spp. and Poaceae after 6000 yr BP may be partly a disclimax effect as a result of Aboriginal burning, but appears also to reflect reduced precipitation. The changes in vegetation and inferred climate can be explained by major changes in synoptic patterns of southern Australia and the adjacent southwest Pacific.

  9. HadISDH land surface multi-variable humidity and temperature record for climate monitoring

    Directory of Open Access Journals (Sweden)

    K. M. Willett

    2014-06-01

    Full Text Available HadISDH.2.0.0 is the first gridded, multi-variable humidity and temperature climate-data product that is homogenised and annually updated. It provides physically consistent estimates for specific humidity, vapour pressure, relative humidity, dew point temperature, wet bulb temperature, dew point depression and temperature. It is a monthly-mean gridded (5° by 5° product with uncertainty estimates that account for spatio-temporal sampling, climatology calculation, homogenisation and irreducible random measurement effects. It provides a unique tool for the monitoring of a variety of humidity-related variables which have different impacts and implications for society. HadISDH.2.0.0 is shown to be in good agreement both with other estimates where they are available, and with theoretical understanding. The dataset is available from 1973 to the present. The theme common to all variables is of a warming world with more water vapour present in the atmosphere. The largest increases in water vapour are found over the tropics and Mediterranean. Over the tropics and high northern latitudes the surface air over land is becoming more saturated. However, despite increasing water vapour over the mid-latitudes and Mediterranean, the surface air over land is becoming less saturated. These observed features may be due to atmospheric circulation changes, land–sea warming disparities and reduced water availability or changed land surface properties.

  10. A New High-resolution Late Glacial-Holocene Climatic Record from Eastern Nanling Mountains in South China

    Institute of Scientific and Technical Information of China (English)

    XUE Jibin; ZHONG Wei; ZHENG Yanming; MA Qiaohong; CAI Ying; OUYANG Jun

    2009-01-01

    A 350-cm-long sediment core sequence from Dahu Swamp situated in the eastern Nanling Mountains was selected for high-resolution paleoclimatic reconstruction since the Late Glacial period. The multi-proxy records of this paper reveal several evidently dry and cold events that may coincide with the Oldest Dryas, the Older Dryas, the Younger Dryas in the late deglacial period. Two relatively wetter and warmer phases occurred in ca. 15,000-14,400 cal yr B.P. And 13,500-12,800 cal yr B.P. Respectively may correspond to the Boiling and Allerod warming events. The Younger Dryas event(ca. 12,800-11,500 cal yr B.P.) revealed by multi-proxies was characterized by relatively colder and drier climate. A warmer and wetter climate, occurred in ca. 10,000-6000 cal yr B.P., was consistent with the Holo-cene Optimum, which coincided with the maximum Northern Hemisphere insolation. The "8.2kyr cool event" and even the "8.8kyr cool event" were indicated as well from our sediment core. A dry mid-Holocene period (ca. 6000-3000 cal yr B.P.) indicated by multi-proxies does not follow the traditional concept of the wet mid-Holoeene conditions observed in other regions in China.

  11. The dating of dipterocarp tree rings: establishing a record of carbon cycling and climatic change in the tropics

    Science.gov (United States)

    Robertson, I.; Froyd, C. A.; Walsh, R. P. D.; Newbery, D. M.; Woodborne, S.; Ong, R. C.

    2004-10-01

    In a first step to obtain a proxy record of past climatic events (including the El Niño-Southern Oscillation) in the normally aseasonal tropical environment of Sabah, a radial segment from a recently fallen dipterocarp (Shorea superba) was radiocarbon dated and subjected to carbon isotope analysis. The high-precision radiocarbon results fell into the ambiguous modern plateau where several calibrated dates can exist for each sample. Dating was achieved by wiggle matching using a Bayesian approach to calibration. Using the defined growth characteristics of Shorea superba, probability density distributions were calculated and improbable dates rejected. It was found that the tree most likely started growing around AD 1660-1685. A total of 173 apparent growth increments were measured and, therefore, it could be determined that the tree formed one ring approximately every two years. Stable carbon isotope values were obtained from resin-extracted wholewood from each ring. Carbon cycling is evident in the juvenile effect, resulting from the assimilation of respired carbon dioxide and lower light levels below the canopy, and in the anthropogenic effect caused by increased industrial activity in the late-nineteenth and twentieth centuries. This study demonstrates that palaeoenvironmental information can be obtained from trees growing in aseasonal environments, where climatic conditions prevent the formation of well-defined annual rings. Copyright

  12. The climatic record of the earliest spring in Romania, regarding the south-east part of the country – spring 2016

    Directory of Open Access Journals (Sweden)

    I. OCTAVIA BOGDAN

    2016-11-01

    Full Text Available The climatic record of the earliest spring in Romania, regarding the south-east part of the country – Spring 2016. In the past 30 years it has been an increasing frequency of early SPRING ARRIVAL. Therefore, vegetation development started in early February. In March, the warm weather continued almost throughout the month, and the hoarfrosts from March became hereby destructive. Frequently, the vegetation in April was in very advanced stages. Even though the temperatures rose in April, cooling in April and late spring hoarfrosts have occurred and caused considerable damage. In this study we analyze the climatic macroprocesses that led to the apparition of an absolute climate record for the earliest spring arrival in 2016. The work is useful to anyone interested in climate change in Romania.

  13. A Test of Climate, Sun, and Culture Relationships from an 1810-Year Chinese Cave Record

    Science.gov (United States)

    Zhang, Pingzhong; Cheng, Hai; Edwards, R. Lawrence; Chen, Fahu; Wang, Yongjin; Yang, Xunlin; Liu, Jian; Tan, Ming; Wang, Xianfeng; Liu, Jinghua; An, Chunlei; Dai, Zhibo; Zhou, Jing; Zhang, Dezhong; Jia, Jihong; Jin, Liya; Johnson, Kathleen R.

    2008-11-01

    A record from Wanxiang Cave, China, characterizes Asian Monsoon (AM) history over the past 1810 years. The summer monsoon correlates with solar variability, Northern Hemisphere and Chinese temperature, Alpine glacial retreat, and Chinese cultural changes. It was generally strong during Europe’s Medieval Warm Period and weak during Europe’s Little Ice Age, as well as during the final decades of the Tang, Yuan, and Ming Dynasties, all times that were characterized by popular unrest. It was strong during the first several decades of the Northern Song Dynasty, a period of increased rice cultivation and dramatic population increase. The sign of the correlation between the AM and temperature switches around 1960, suggesting that anthropogenic forcing superseded natural forcing as the major driver of AM changes in the late 20th century.

  14. Two Extreme Climate Events of the Last 1000 Years Recorded in Himalayan and Andean Ice Cores: Impacts on Humans

    Science.gov (United States)

    Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.; Kenny, D. V.; Lin, P.

    2013-12-01

    In the last few decades numerous studies have linked pandemic influenza, cholera, malaria, and viral pneumonia, as well as droughts, famines and global crises, to the El Niño-Southern Oscillation (ENSO). Two annually resolved ice core records, one from Dasuopu Glacier in the Himalaya and one from the Quelccaya Ice Cap in the tropical Peruvian Andes provide an opportunity to investigate these relationships on opposite sides of the Pacific Basin for the last 1000 years. The Dasuopu record provides an annual history from 1440 to 1997 CE and a decadally resolved record from 1000 to 1440 CE while the Quelccaya ice core provides annual resolution over the last 1000 years. Major ENSO events are often recorded in the oxygen isotope, insoluble dust, and chemical records from these cores. Here we investigate outbreaks of diseases, famines and global crises during two of the largest events recorded in the chemistry of these cores, particularly large peaks in the concentrations of chloride (Cl-) and fluoride (Fl-). One event is centered on 1789 to 1800 CE and the second begins abruptly in 1345 and tapers off after 1360 CE. These Cl- and F- peaks represent major droughts and reflect the abundance of continental atmospheric dust, derived in part from dried lake beds in drought stricken regions upwind of the core sites. For Dasuopu the likely sources are in India while for Quelccaya the sources would be the Andean Altiplano. Both regions are subject to drought conditions during the El Niño phase of the ENSO cycle. These two events persist longer (10 to 15 years) than today's typical ENSO events in the Pacific Ocean Basin. The 1789 to 1800 CE event was associated with a very strong El Niño event and was coincidental with the Boji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive droughts are documented in Central and South America. Likewise, the 1345 to 1360 CE event, although poorly documented

  15. Climate variability in south-eastern Australia over the last 1500 years inferred from the high-resolution diatom records of two crater lakes

    Science.gov (United States)

    Barr, Cameron; Tibby, John; Gell, Peter; Tyler, Jonathan; Zawadzki, Atun; Jacobsen, Geraldine E.

    2014-07-01

    Climates of the last two millennia have been the focus of numerous studies due to the availability of high-resolution palaeoclimate records and the occurrence of divergent periods of climate, commonly referred to as the ‘Medieval Climatic Anomaly' and ‘The Little Ice Age'. The majority of these studies are centred in the Northern Hemisphere and, in comparison, the Southern Hemisphere is relatively under-studied. In Australia, there are few high-resolution, palaeoclimate studies spanning a millennium or more and, consequently, knowledge of long-term natural climate variability is limited for much of the continent. South-eastern Australia, which recently experienced a severe, decade-long drought, is one such region. Results are presented of investigations from two crater lakes in the south-east of mainland Australia. Fluctuations in lake-water conductivity, a proxy for effective moisture, are reconstructed at sub-decadal resolution over the past 1500 years using a statistically robust, diatom-conductivity transfer function. These data are interpreted in conjunction with diatom autecology. The records display coherent patterns of change at centennial scale, signifying that both lakes responded to regional-scale climate forcing, though the nature of that response varied between sites due to differing lake morphometry. Both sites provide evidence for a multi-decadal drought, commencing ca 650 AD, and a period of variable climate between ca 850 and 1400 AD. From ca 1400-1880 AD, coincident with the timing of the ‘Little Ice Age', climates of the region are characterised by high effective moisture and a marked reduction in inter-decadal variability. The records provide context for climates of the historical period and reveal the potential for more extreme droughts and more variable climate than that experienced since European settlement of the region ca 170 years ago.

  16. Holocene climate variability in Texas, USA: An integration of existing paleoclimate data and modeling with a new, high-resolution speleothem record

    Science.gov (United States)

    Wong, Corinne I.; Banner, Jay L.; Musgrove, Marylynn

    2015-01-01

    Delineating the climate processes governing precipitation variability in drought-prone Texas is critical for predicting and mitigating climate change effects, and requires the reconstruction of past climate beyond the instrumental record. We synthesize existing paleoclimate proxy data and climate simulations to provide an overview of climate variability in Texas during the Holocene. Conditions became progressively warmer and drier transitioning from the early to mid Holocene, culminating between 7 and 3 ka (thousand years ago), and were more variable during the late Holocene. The timing and relative magnitude of Holocene climate variability, however, is poorly constrained owing to considerable variability among the different records. To help address this, we present a new speleothem (NBJ) reconstruction from a central Texas cave that comprises the highest resolution proxy record to date, spanning the mid to late Holocene. NBJ trace-element concentrations indicate variable moisture conditions with no clear temporal trend. There is a decoupling between NBJ growth rate, trace-element concentrations, and δ18O values, which indicate that (i) the often direct relation between speleothem growth rate and moisture availability is likely complicated by changes in the overlying ecosystem that affect subsurface CO2 production, and (ii) speleothem δ18O variations likely reflect changes in moisture source (i.e., proportion of Pacific-vs. Gulf of Mexico-derived moisture) that appear not to be linked to moisture amount.

  17. Roosevelt Island Climate Evolution Project (RICE): A 65 Kyr ice core record of black carbon aerosol deposition to the Ross Ice Shelf, West Antarctica.

    Science.gov (United States)

    Edwards, Ross; Bertler, Nancy; Tuohy, Andrea; Neff, Peter; Proemse, Bernedette; Feiteng, Wang; Goodwin, Ian; Hogan, Chad

    2015-04-01

    Emitted by fires, black carbon aerosols (rBC) perturb the atmosphere's physical and chemical properties and are climatically active. Sedimentary charcoal and other paleo-fire records suggest that rBC emissions have varied significantly in the past due to human activity and climate variability. However, few paleo rBC records exist to constrain reconstructions of the past rBC atmospheric distribution and its climate interaction. As part of the international Roosevelt Island Climate Evolution (RICE) project, we have developed an Antarctic rBC ice core record spanning the past ~65 Kyr. The RICE deep ice core was drilled from the Roosevelt Island ice dome in West Antarctica from 2011 to 2013. The high depth resolution (~ 1 cm) record was developed using a single particle intracavity laser-induced incandescence soot photometer (SP2) coupled to an ice core melter system. The rBC record displays sub-annual variability consistent with both austral dry-season and summer biomass burning. The record exhibits significant decadal to millennial-scale variability consistent with known changes in climate. Glacial rBC concentrations were much lower than Holocene concentrations with the exception of several periods of abrupt increases in rBC. The transition from glacial to interglacial rBC concentrations occurred over a much longer time relative to other ice core climate proxies such as water isotopes and suggests . The protracted increase in rBC during the transition may reflected Southern hemisphere ecosystem / fire regime changes in response to hydroclimate and human activity.

  18. Climate and lake-level history of the northern altiplano, Bolivia, as recorded in holocene sediments of the Rio Desaguadero

    Science.gov (United States)

    Baucom, P.C.; Rigsby, C.A.

    1999-01-01

    Strata exposed in terraces and modern cutbanks along the Rio Desaguadero contain a variety of lithofacies that were deposited in four distinct facie??s associations. These facie??s 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 4500 and 3900 yr BP and another between 2000 and 2200 yr BP. These wet periods were interrupted by three periods of fluvial downcutting, centered at approximately 4000 yr BP, 3600 yr BP, and after 2000 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 7000 yr BP until approximately 3200 yr BP that was followed by a single episode (post-3210 yr BP) of downcutting 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. Copyright ??1999, SEPM (Society for Sedimentar)- Geology).

  19. 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.

  20. A high-resolution late Pleistocene record of pollen vegetation and climate change from Jingning, NW China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    With the support of 18 AMS-14C data, a high-resolution pollen record from the Suancigou section at Jingning, Gansu Province was established. Our results showed that the vegetation experienced a series of changes characterized by the alternative growth and decline of forest and steppe components during the period from 44.2 to 11 ka B.P. in the Jingning area. Over the period of 44-29 ka B.P. (MIS3), coniferous forests were flourishing, indicating a humid climate with the temperature being lower than that of the present. Since 23 ka B.P., the vegetation was dominated by steppe-desert steppe under a cold and dry condition, and entered the Last Glacial Maximum dominated by desert steppe. Several periods of the marked decrease in the arborous pollen content in Suancigou well corresponded to the North Atlantic Heinrich events, especially to Heinrich event 3, further supporting that the Heinrich events were well reflected by the pollen record in the Loess Plateau as well.

  1. A 30+ Year AVHRR Land Surface Reflectance Climate Data Record and Its Application to Wheat Yield Monitoring

    Directory of Open Access Journals (Sweden)

    Belen Franch

    2017-03-01

    Full Text Available The Advanced Very High Resolution Radiometer (AVHRR sensor provides a unique global remote sensing dataset that ranges from the 1980s to the present. Over the years, several efforts have been made on the calibration of the different instruments to establish a consistent land surface reflectance time-series and to augment the AVHRR data record with data from other sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS. In this paper, we present a summary of all the corrections applied to the AVHRR surface reflectance and NDVI Version 4 Product, developed in the framework of the National Oceanic and Atmospheric Administration (NOAA Climate Data Record (CDR program. These corrections result from assessment of the geolocation, improvement of cloud masking, and calibration monitoring. Additionally, we evaluate the performance of the surface reflectance over the AERONET sites by a cross-comparison with MODIS, which is an already validated product, and evaluation of a downstream leaf area index (LAI product. We demonstrate the utility of this long time-series by estimating the winter wheat yield over the USA. The methods developed by Becker-Reshef et al. (2010 and Franch et al. (2015 are applied to both the MODIS and AVHRR data. Comparison of the results from both sensors during the MODIS-era shows the consistency of the dataset with similar errors of 10%. When applying the methods to AVHRR historical data from the 1980s, the results have errors equivalent to those derived from MODIS.

  2. A 125-year record of climate and chemistry variability at the Pine Island Glacier ice divide, Antarctica

    Science.gov (United States)

    Schwanck, Franciele; Simões, Jefferson C.; Handley, Michael; Mayewski, Paul A.; Auger, Jeffrey D.; Bernardo, Ronaldo T.; Aquino, Francisco E.

    2017-07-01

    The Mount Johns (MJ) ice core (79°55' S; 94°23' W) was drilled near the Pine Island Glacier ice divide on the West Antarctic Ice Sheet during the 2008-2009 austral summer, to a depth of 92.26 m. The upper 45 m of the record covers approximately 125 years (1883-2008), showing marked seasonal variability. Trace element concentrations in 2137 samples were determined using inductively coupled plasma mass spectrometry. In this study, we reconstruct mineral dust and sea salt aerosol transport and investigate the influence of climate variables on the elemental concentrations at the MJ site. The ice core record reflects changes in emissions as well as atmospheric circulation and transport processes. Our trajectory analysis shows distinct seasonality, with strong westerly transport in the winter months and secondary northeasterly transport in the summer. During summer months, the trajectories present slow-moving (short) transport and are more locally influenced than in other seasons. Finally, our reanalysis correlations with trace element suggest that marine-derived trace element concentrations are strongly influenced by sea ice concentration and sea surface temperature anomalies. The results show that seasonal elemental concentration maxima in sea salt elements correlate well with the sea ice concentration winter maxima in the west Amundsen and Ross seas. Lastly, we observed an increased concentration of marine aerosols when sea surface temperature decreased.

  3. Evidence and analysis of 2012 Greenland records from spaceborne observations, a regional climate model and reanalysis data

    Directory of Open Access Journals (Sweden)

    M. Tedesco

    2012-11-01

    Full Text Available A combined analysis of remote sensing observations, regional climate model (RCM outputs and reanalysis data over the Greenland ice sheet provides evidence that multiple records were set during summer 2012. Melt extent was the largest in the satellite era (extending up to ~ 97% of the ice sheet and melting lasted up to ~ two months longer than the 1979–2011 mean. Model results indicate that near surface temperature was ~ 3 standard deviations (σ above the 1958–2011 mean, while surface mass balance was ~ 3σ below the mean and runoff was 3.9σ above the mean over the same period. Albedo, exposure of bare ice and surface mass balance also set new records, as did the total mass balance with summer and annual mass changes of, respectively, −627 Gt and −574 Gt, 2σ below the 2003–2012 mean.

    We identify persistent anticyclonic conditions over Greenland associated with anomalies in the North Atlantic Oscillation (NAO, changes in surface conditions (e.g. albedo and pre-conditioning of surface properties from recent extreme melting as major driving mechanisms for the 2012 records. Because of self-amplifying positive feedbacks, less positive if not increasingly negative SMB will likely occur should large-scale atmospheric circulation and induced surface characteristics observed over the past decade persist. Since the general circulation models of the Coupled Model Intercomparison Project Phase 5 (CMIP5 do not simulate the abnormal anticyclonic circulation resulting from extremely negative NAO conditions as observed over recent years, contribution to sea level rise projected under different warming scenarios will be underestimated should the trend in NAO summer values continue.

  4. Impact of Site Conditions Changes on the Tree Ring Records Suitability as Climate Proxies in the Brazilian Amazon

    Directory of Open Access Journals (Sweden)

    Oliver Dünisch

    Full Text Available ABSTRACT The increment zones width in the xylem of Swietenia macrophylla King was investigated by dendrochronological methods in an undisturbed and a strongly disturbed tropical site near Aripuanã, Mato Grosso, Brazil (10°09’ S, 59°26’W. The study aimed to assess the impact of forest disturbance on the relationship between precipitation and the cambial growth of this species. Tree-ring width chronologies were developed for both sites from cross-dated increment curves. Simple correlations were computed between monthly precipitation records and the annual increment of Swietenia for the period between 1870 and 2000. Logging activities and altered land use caused a significant decrease of the water supply of the Swietenia trees grown in the disturbed area compared to trees grown in the undisturbed area. Consequently, the precipitation of almost the total growing season had a significant influence on the tree ring width of Swietenia grown in the disturbed area, while in the undisturbed forest area the significant correlation between monthly precipitation and the tree ring width of Swietenia was restricted to the beginning of the growing season (November to January. However, the reconstruction of monthly precipitation data from the tree ring width records was more precise using the chronology developed from tree ring width records of undisturbed trees compared to the chronology developed from tree ring widths from the disturbed area. It was concluded that the use of the tree ring widths of Swietenia as climate proxies is restricted to certain months of the year and requires tree ring width chronologies developed from trees grown in undisturbed or only slightly disturbed forest areas without severe anthropogenic changes in microclimate.

  5. Records of natural fire and climate history during the last three glacial-interglacial cycles around the South China Sea

    Institute of Scientific and Technical Information of China (English)

    LUO; Yunli

    2001-01-01

    [1]Komarek, E. V. Sr., The meteorological basis for fire ecology, in Proc. Tall Timbers Fire Ecol. Conf., 1966, 35-44.[2]Gilbert, L. M., Fire as a factor in the development of vegetation types, Aust. Fores., 1962, 26: 67-70.[3]Johnston, V. R., The ecology of fire, Audubon, 1970, 72: 76-119.[4]Chen Yinshuo, Forest fire in early Holocene forest changes at Lake Barrine, Australia, Acta Botanica Sinica (in Chinese),1990, 32(1): 69-75.[5]Michael, I. B., Fire in the earth sciences, Episodes, 1997, 20(4): 223-226.[6]Herring, J. R., Charcoal flux into sediments of the north Pacific Ocean: The Cenozoic record of burning, in The carbon cycle and atmospheric CO2: Natural variations from Archean to present, Geophysical Monograph, 1985, 32:237-251.[7]Kershaw, A. P., Climatic change and aboriginal burniing in northeast Australia during the last two glacial/interglacial cy cles. Nature, 1985, 322: 47-49.[8]Hermann, B., Late Quaternary vegetation, climates and fire history from the tropical mountain region of Morrode Itapeva,SE Brazil, Palaeogeography, Palaeoclimatology, Palaeoecology, 1997, 129: 407-422.[9]Earle, C. J., Brubaker, L. B., Anderson, P. M., Charcoal in northcentral Alaskan lake sediments: Relationships to fire and late-Quaternary vegetation history, Review of Palaeobotany and Palynology, 1996, 92: 83-95.[10]Xuan Wang, Sander van der Karrs., Peter, K. et al., A record of fire, vegetation and climate through the last three glacial cycles from Lombok Ridge core G6-4, eastern Indian Ocean, Indonesia, Palaeogeography, Palaeoclimatology, Pa laeoecology, 1999, 147: 241-256.[11]Sander van der Kaars, Xuan Wang, Peter, K. et al., A late Quaternary palaeoecological record from the Banda Sea, Indo nesia: Patterns of vegetation, climate and biomass burning in Indonesia and northern Australia, Palaeogeography, Palaeoclimatology, Palaeoecology, 2000, 155: 135-154.[12]Isabel, F., Volker, M., A review of charcoal analysis as a tool for

  6. Understanding Abrupt, Natural Climate Variability Post-Industrial Revolution from the Subtropical Eastern Pacific: A Novel High Resolution Alkenone-derived Sea Surface Temperature Record

    Science.gov (United States)

    Kelly, C. S.; O'Mara, N. A.; Herbert, T.; Abella-Gutiérrez, J. L.; Herguera, J. C.

    2015-12-01

    Despite the ocean's importance in global biogeochemical feedbacks and heat storage, there is still a paucity of decadally-resolved sea surface temperature (SST) records to complement lacustrine and dendrological records of recent paleoclimate. Natural climate variability on multidecadal timescales is dominated by internal ocean circulation dynamics and feedbacks, and it is therefore imperative to employ marine proxies to reconstruct high resolution climate change. The timescales of this ocean-induced natural climate variability can be broken down into a few characteristic climate modes. Pressing questions about these modes include their stationarity in frequency and amplitude over time, in addition to the hypothesis that anthropogenic climate change has altered their behavior in comparison to natural variability. To pursue these questions, we must discern and analyze suitable climate archives in regions where modes of interest dominate modern climate variability. The region of Baja California, Mexico exhibits exceptional teleconnection to the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Local, dramatic effects of ENSO and PDO on the marine biology and economy underline the importance of regional paleoclimate records from the Baja peninsula. Here, we present a high-resolution alkenone-derived SST reconstruction from the Industrial Revolution through the year 2000 by analysis of laminated box and Kasten sediment cores at Site PCM 00-78 (25.18°N, 112.66°W) in the subtropical eastern Pacific at a depth of 540 meters. Our SST record corresponds with NOAA extended reconstructed sea surface temperature, providing a robust basis for organic geochemical marine climatic reconstructions on timescales usually accessible only through speleothems, coral density bands, tree rings, and the like. Accordingly, based on this comparison to the historical data we expect our SST record may provide a more robust record of inter and multidecadal

  7. Variability in the annual cycle of Northern Hemisphere snow extent, using a newly completed climate data record

    Science.gov (United States)

    Henderson, G. R.; Leathers, D. J.; Robinson, D. A.

    2012-12-01

    Variability in the annual cycle of Northern Hemisphere snow cover extent (SCE) may have important impacts on the global climate system through a number of potential feedback mechanisms. Motivated by recent snow literature heralding reports ranging from earlier spring melt, to an overall seasonal decrease in SCE, both spatial and temporal variability in extent are explored using a newly completed SCE climate data record (CDR). From a hydrologic standpoint, such shifts have huge implications to the overall climatology of any region with snow present in its seasonal cycle. The SCE CDR utilized in this study is the result of a reanalysis of NOAA satellite-derived maps of NH continental SCE and begins in 1966. The earlier 33 years of data are drawn from coarse-scale weekly NOAA maps, whilst recent years are based on a downgraded version of the IMS 24 km NOAA product, currently produced by the National Ice Center. The Rutgers Global Snow Lab undertook reanalysis and merging of the different resolution datasets as part of the NASA MEaSUREs project. Principal component (PC) analysis was performed on the annual cycle of NH, and individual continental snow extent totals. Close to 75% of variance was explained by the first three PCs, in the case of NH and Eurasia snow extents. Snow composite analysis based on positive PC scores time series years displays greater snow extent, in excess of 4 × 106 km2 in the case of the NH alone. Preliminary assessment of associations with large-scale atmospheric patterns (e.g. surface air temperature, mid-tropospheric geopotential height), yielded patterns indicative of know teleconnection patterns such as the AO and NAO indices. Results from additional PC analysis performed spatially on the SCE CDR will be discussed.

  8. A method for merging nadir-sounding climate records, with an application to the global-mean stratospheric temperature data sets from SSU and AMSU

    Directory of Open Access Journals (Sweden)

    C. McLandress

    2015-04-01

    Full Text Available A method is proposed for merging different nadir-sounding climate data records using measurements from high resolution limb sounders to provide a transfer function between the different nadir measurements. The nadir-sounding records need not be overlapping so long as the limb-sounding record bridges between them. The method is applied to global mean stratospheric temperatures from the NOAA Climate Data Records based on the Stratospheric Sounding Unit (SSU and the Advanced Microwave Sounding Unit-A (AMSU, extending the SSU record forward in time to yield a continuous data set from 1979 to present. SSU and AMSU are bridged using temperature measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS, which is of high enough vertical resolution to accurately represent the weighting functions of both SSU and AMSU. For this application, a purely statistical approach is not viable since the different nadir channels are not sufficiently linearly independent, statistically speaking. The extended SSU global-mean data set is in good agreement with temperatures from the Microwave Limb Sounder (MLS on the Aura satellite, with both exhibiting a cooling trend of ~ 0.6 ± 0.3 K decade−1 in the upper stratosphere from 2004–2012. The extended SSU data set also compares well with chemistry-climate model simulations over its entire record, including the contrast between the weak cooling seen over 1995–2004 compared with the large cooling seen in the period 1986–1995 of strong ozone depletion.

  9. A late Holocene metal record of Andean climate and anthropogenic activity in lake sediments near Quelccaya Ice Cap, Peru

    Science.gov (United States)

    Beal, S. A.; Kelly, M. A.; Jackson, B. P.; Stroup, J. S.; Osterberg, E. C.

    2011-12-01

    The tropical hypothesis maintains that major changes in global climate are motivated by phenomena based at tropical latitudes. Evidence for this hypothesis lies in: modern-day observations of El Niño Southern Oscillation (ENSO); East African lake sediment records of Intertropical Convergence Zone (ITCZ) position that precede high-latitude changes; and the potential for ITCZ shifts to cause major CO2 degassing from the Southern Ocean. In order to improve the understanding of these phenomena we present an ~1800 year record of atmospheric metal deposition in a lake sediment core near Quelccaya Ice Cap, Peru (13.9 °S). In June, 2010 we collected a 1.45 meter-long core from Yanacocha - a small, closed-basin tarn that has been isolated from glacial input since ~11,200 BP. The chronology for the core is based on 4 of 6 AMS 14C dates on aquatic macrofossils and one sharp Zr/Ti anomaly at 36 cm, likely derived from the 350 BP eruption of Huaynaputina. We completely digested organic-rich core samples at 1 cm resolution using HNO3, HCl, and HF in a closed-vessel microwave system, and then analyzed the digestates for 67 metals by inductively coupled plasma mass spectrometry. Here we show fluxes of lithogenic metals (Fe, Nb, Ti, and Zr) that reflect changes in wind strength and aridity, fluxes of lithogenic metal isotopes (REEs and Pb) that reflect wind direction, and enrichment factors (EFs) of metals (Ag, As, Cd, Cu, Hg, and Pb) that reflect anthropogenic activity. Five episodic peaks in lithogenic metal fluxes, centered around 1800, 1300, 900, 600, and 100 yrs BP, are thought to result from either drier or windier conditions, potentially caused by a northern ITCZ position or a more persistent El Niño state. The provenance of atmospheric deposition, evidenced by REE ratios (light REEs / heavy REEs), suggest that high lithogenic fluxes are associated with a change in wind direction, possibly caused by a change in the ENSO state, which will be explored with forthcoming Pb

  10. Validation of a Climate-Data Record of the "Clear-Sky" Surface Temperature of the Greenland Ice Sheet

    Science.gov (United States)

    Hall, Dorothy K.; Box, Jason E.; Koenig, Lora S.; DiGirolamo, Nicolo E.; Comiso, Josefino C.; Shuman, Christopher A.

    2011-01-01

    Surface temperatures on the Greenland Ice Sheet have been studied on the ground, using automatic weather station (AWS) data from the Greenland-Climate Network (GC-Net), and from analysis of satellite sensor data. Using Advanced Very High Frequency Radiometer (AVHRR) weekly surface temperature maps, warming of the surface of the Greenland Ice Sheet has been documented since 1981. We extended and refined this record using higher-resolution Moderate-Resolution Imaging Spectroradiometer (MODIS) data from March 2000 to the present. We developed a daily and monthly climate-data record (CDR) of the "clear-sky" surface temperature of the Greenland Ice Sheet using an ice-surface temperature (1ST) algorithm developed for use with MODIS data. Validation of this CDR is ongoing. MODIS Terra swath data are projected onto a polar stereographic grid at 6.25-km resolution to develop binary, gridded daily and mean-monthly 1ST maps. Each monthly map also has a color-coded image map that is available to download. Also included with the monthly maps is an accompanying map showing number of days in the month that were used to calculate the mean-monthly 1ST. This is important because no 1ST decision is made by the algorithm for cells that are considered cloudy by the internal cloud mask, so a sufficient number of days must be available to produce a mean 1ST for each grid cell. Validation of the CDR consists of several facets: 1) comparisons between ISTs and in-situ measurements; 2) comparisons between ISTs and AWS data; and 3) comparisons of ISTs with surface temperatures derived from other satellite instruments such as the Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper Plus (ETM+). Previous work shows that Terra MODIS ISTs are about 3 C lower than in-situ temperatures measured at Summit Camp, during the winter of 2008-09 under clear skies. In this work we begin to compare surface temperatures derived from AWS data with ISTs from the MODIS CDR.

  11. On the astronomical origin of the Hallstatt oscillation found in radiocarbon and climate records throughout the Holocene

    Science.gov (United States)

    Scafetta, Nicola; Milani, Franco; Bianchini, Antonio; Ortolani, Sergio

    2017-04-01

    evolves from more circular shapes (e≈0.590) to a more elliptical ones (e≈0.598), that is while the orbital system is slowly exploding or bursting outward. Since at this timescale the PMC eccentricity variation is relatively small (e=0.594±0.004), the physical origin of the astronomical 2318 yr cycle is better identified and distinguished from faster orbital oscillations by the times it takes the PMC to make pericycles and epicycles around the Sun and the times it takes to move from minimum to maximum distance from the Sun within those arcs. These particular proxies reveal a macroscopic 2318 yr period oscillation, together with other three stable outer planet orbital resonances with periods of 159, 171 and 185 yr. This 2318 yr oscillation is found to be spectrally coherent with the Δ14C Holocene record with a statistical confidence above 95%, as determined by spectral analysis and cross wavelet and wavelet coherence analysis. At the Hallstatt time scale, maxima of the radionucleotide production occurred when, within each pericycle-apocycle orbital arc, the time required by the PMC to move from the minimum to the maximum distance from the Sun varies from about 8 to 16 years while the time required by the same to move from the maximum to the minimum distance from the Sun varies from about 7 to 14 years, and viceversa. Thus, we found that a fast expansion of the Sun-PMC orbit followed by a slow contraction appears to prevent cosmic rays to enter within the system inner region while a slow expansion followed by a fast contraction favors it. Similarly, the same dynamics could modulate the amount of interplanetary/cosmic dust falling on Earth. Indeed, many other stable orbital resonance frequencies (e.g. at periods of 20 yr, 45 yr, 60 yr, 85 yr, 159-171-185 yr, etc.) are found in radionucleotide, solar, aurora and climate records, as determined in the scientific literature. Thus, the result supports a planetary theory of solar and/or climate variation that has recently

  12. Interactions between climate and vegetation during the Lateglacial period as recorded by lake and mire sediment archives in Northern Italy and Southern Switzerland

    NARCIS (Netherlands)

    Vescovi, E.; Ravazzi, C.; Arpenti, E.; Finsinger, W.; Pini, R.; Valsecchi, V.; Wick, L.; Ammann, B.; Tinner, W.

    2007-01-01

    We reconstruct the vegetational history of the southern side of the Alps at 18,000–10,000 cal yr BP using previous and new AMS-dated stratigraphic records of pollen, stomata, and macrofossils. To address potential effects of climatic change on vegetation, we compare our results with independent pale

  13. Characterization and dating of coastal deposits of NW Portugal (Minho-Neiva area): A record of climate, eustasy and crustal uplift during the Quaternary

    DEFF Research Database (Denmark)

    Carvalhido, Ricardo P.; Pereira, Diamantino I.; Cunha, Pedro P.;

    2014-01-01

    ) and probably reflecting cold/mid-cold and wet/dry climate conditions; c) this sub-unit is topped by soliflucted lobes and sandy-silty/silty deposits recording cold and dry climate dated 20-13 ka (MIS2), and d) a top subunit dated to 16-18th century, recording Little Ice Age events, consisting of fluvial...... sediments coeval with temperate climate evolving to aeolian dunes from the Maunder Minimum (cold windy dry conditions). (C) 2014 Elsevier Ltd and INQUA. All rights reserved.......) the lower sub-unit, corresponding to ferruginous stream deposits and aeolian dunes dated ca. 67-61 ka (MIS4), probably related with sub-humid to arid mid-cold conditions; b) on the slopes, the lower sub-unit is overlapped by sandy-silty colluvium and sandy alluvial deposits dated ca. 56-28 ka (MIS3...

  14. Wet and cold climate conditions recorded by coral geochemical proxies during the beginning of the first millennium CE in the northern South China Sea

    Science.gov (United States)

    Xiao, Hangfang; Deng, Wenfeng; Chen, Xuefei; Wei, Gangjian; Zeng, Ti; Zhao, Jian-xin

    2017-03-01

    The past two millennia include some distinct climate intervals, such as the Medieval Warm Period (MWP) and the Little Ice Age (LIA), which were caused by natural forcing factors, as well as the Current Warm Period (CWP) that has been linked to anthropogenic factors. Therefore, this period has been of great interest to climate change researchers. However, most studies are based on terrestrial proxy records, historical documentary data, and simulation results, and the ocean and the tropical record are very limited. The Eastern Han, Three Kingdoms, and Western Jin periods (25-316 CE) cover the beginning first millennium CE in China, and were characterized by a cold climate and frequent wars and regime changes. This study used paired Sr/Ca and δ18O series recovered from a fossil coral to reconstruct the sea surface water conditions during the late Eastern Han to Western Jin periods (167-309 CE) at Wenchang, eastern Hainan Island in the northern South China Sea (SCS), to investigate climate change at this time. The long-term sea surface temperature (SST) during the study interval was 25.1 °C, which is about 1.5 °C lower than that of the CWP (26.6 °C). Compared with the average value of 0.40‰ during the CWP, the long-term average seawater δ18O (-0.06‰) was more negative. These results indicate that the climate conditions during the study period were cold and wet and comparable with those of the LIA. This colder climate may have been associated with the weaker summer solar irradiance. The wet conditions were caused by the reduced northward shift of the intertropical convergence zone/monsoon rainbelt associated with the retreat of the East Asian summer monsoon. Interannual and interdecadal climate variability may also have contributed to the variations in SST and seawater δ18O recorded over the study period.

  15. 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

    Sea level is one of the 50 Essential Climate Variables (ECVs) listed by the Global Climate Observing System (GCOS) in climate change monitoring. In the past two decades, sea level has been routinely measured from space using satellite altimetry techniques. In order to address a number of importan...... present preliminary independent validations of the SL_cci products, based on tide gauges comparison and a sea level budget closure approach, as well as comparisons with ocean reanalyses and climate model outputs....

  16. High resolution stalagmite climate record from the Yucatán Peninsula spanning the Maya terminal classic period

    Science.gov (United States)

    Medina-Elizalde, Martín; Burns, Stephen J.; Lea, David W.; Asmerom, Yemane; von Gunten, Lucien; Polyak, Victor; Vuille, Mathias; Karmalkar, Ambarish

    2010-09-01

    The decline of the Classic Maya civilization was complex and geographically variable, and occurred over a ~ 150-year interval, known as the Terminal Classic Period (TCP, C.E. 800-950). Paleoclimate studies based on lake sediments from the Yucatán Peninsula lowlands suggested that drought prevailed during the TCP and was likely an important factor in the disintegration of the Classic Maya civilization. The lacustrine evidence for decades of severe drought in the Yucatán Peninsula, however, does not readily explain the long 150-year socio-political decline of the Classic Maya civilization. Here we present a new, absolute-dated, high-resolution stalagmite δ18O record from the northwest Yucatán Peninsula that provides a much more detailed picture of climate variability during the last 1500 years. Direct calibration between stalagmite δ18O and rainfall amount offers the first quantitative estimation of rainfall variability during the Terminal Classic Period. Our results show that eight severe droughts, lasting from 3 to 18 years, occurred during major depopulation events of Classic Maya city-states. During these droughts, rainfall was reduced by 52% to 36%. The number and short duration of the dry intervals help explain why the TCP collapse of the Mayan civilization occurred over 150 years.

  17. An Evaluation of Antarctica as a Calibration Target for Passive Microwave Satellite Missions with Climate Data Record Applications

    Science.gov (United States)

    Kim, E. J.

    2011-12-01

    surface salinity, both important climate variables. Science studies involving these variables can now take advantage of new satellite L-band observations. The first mission with regular global passive microwave observations at L-band is the European Space Agency's Soil Moisture and Ocean Salinity (SMOS), launched November, 2009. A second mission, NASA's Aquarius, was launched June, 2011. A third mission, NASA's Soil Moisture Active Passive (SMAP) is scheduled to launch in 2014. Together, these three missions may provide a decade-long data record-provided that they are intercalibrated. The intercalibration is best performed at the radiance (brightness temperature) level, and Antarctica is proving to be a key calibration target. However, Antarctica has thus far not been fully characterized as a potential target. This paper will present evaluations of Antarctica as a microwave calibration target for the above satellite missions. Preliminary analyses have identified likely target areas, such as the vicinity of Dome-C and larger areas within East Antarctica. Physical sources of temporal and spatial variability of polar firn are key to assessing calibration uncertainty. These sources include spatial variability of accumulation rate, compaction, surface characteristics (dunes, micro-topography), wind patterns, and vertical profiles of density and temperature. Using primarily SMOS data, variability is being empirically characterized and attempts are being made to attribute observed variability to physical sources. One expected outcome of these studies is the potential discovery of techniques for remotely sensing--over all of Antarctica-parameters such as surface temperature.

  18. Structure of phytoplankton (Continuous Plankton Recorder and SeaWiFS and impact of climate in the Northwest Atlantic Shelves

    Directory of Open Access Journals (Sweden)

    S. C. Leterme

    2007-01-01

    Full Text Available All marine organisms are affected to some extent by the movement and thermal properties of oceanic currents. However phytoplankton, because of its small size is most directly coupled to the physical environment. The intense hydrodynamic activity observed in the Northwest Atlantic Shelves Province makes this region especially intriguing from the point of view of physical-biological interactions. In the present work, remote sensed data of Sea Surface Height (SSH anomalies, Sea-surface chlorophyll a concentrations (SeaWiFS, and Sea Surface Temperature (SST are used to complement the Continuous Plankton Recorder (CPR survey that continuously sampled a route between Norfolk (Virginia, USA; 39° N, 71° W and Argentia (Newfoundland; 47° N, 54° W over the period 1995–1998. Over this period, we examined physical structures (i.e. SST and SSH and climatic forcing associated with space-time phytoplankton structure. Along this route, the phytoplankton structures were mainly impacted by the changes in surface flow along the Scotian Shelf rather than significantly influenced by the mesoscale features of the Gulf Stream. These changes in water mass circulation caused a drop in temperature and salinity along the Scotian Shelf that induced changes in phytoplankton and zooplankton abundance.

  19. Structure of phytoplankton (Continuous Plankton Recorder and SeaWiFS and impact of climate in the Northwest Atlantic Shelves

    Directory of Open Access Journals (Sweden)

    S. C. Leterme

    2006-10-01

    Full Text Available All marine organisms are affected to some extent by the movement and thermal properties of oceanic currents. However phytoplankton, because of its small size is most directly coupled to the physical environment. The intense hydrodynamic activity observed in the Northwest Atlantic Shelves Province makes this region especially intriguing from the point of view of physical-biological interactions. In the present work, remote sensed data of Sea Surface Height (SSH anomalies, Sea-surface chlorophyll a concentrations (SeaWiFS, and Sea Surface Temperature (SST are used to complement the Continuous Plankton Recorder (CPR survey that continuously sampled a route between Norfolk (Virginia, USA; 39° N, 71° W and Argentia (Newfoundland; 47° N, 54° W over the period 1995–1998. Over this period, we examined physical structures (i.e. SST and SSH and climatic forcing associated with space-time phytoplankton structure. Along this route, the phytoplankton structures were mainly impacted by the changes in surface flow along the Scotian Shelf rather than significantly influenced by the mesoscale features of the Gulf Stream. These changes in water mass circulation caused a drop in temperature and salinity along the Scotian Shelf that induced changes in phytoplankton and zooplankton abundance.

  20. Holocene fire, vegetation, and climate dynamics inferred from charcoal and pollen record in the eastern Tibetan Plateau

    Science.gov (United States)

    Zhao, Wenwei; Zhao, Yan; Qin, Feng

    2017-10-01

    Understanding fire history and its driving mechanisms can provide valuable insights into present fire regime (intensity, severity and frequency), the interplay between vegetation and fire, and trigger of fire activities. Here we reconstruct the Holocene fire history in the Zoige Basin on the eastern Tibetan Plateau, on the basis of sedimentary micro-charcoal record over the last 10.0 ka (1 ka = 1000 cal yr BP) and discuss the influences of vegetation and climate on fire dynamics. Our results show that regional fire was active at 10.0-3.3 ka and a significant decrease in fire activity characterized the period after 3.3 ka. The high regional fire frequency at 10.0-3.3 ka is consistent with the forested landscape suggested by high affinity scores of cool mixed forest biome (mainly consisted of spruce), implying that fire dynamics during this period was generally controlled by the variations of arboreal biomass and summer temperature. During 6.3-4.6 ka the prevailing Asian summer monsoon provided increased moisture to this region and thus suppressed fire activities to an extent, despite the availability of abundant biomass. Declined tree biomass after 3.3 ka probably accounted for the decreased fire activities. In addition, two successive fire events at ca. 3.5-3.3 ka were likely responsible for the subsequent abrupt decline of forest components in the landscape.

  1. 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

    Sea level is one of the 50 Essential Climate Variables (ECVs) listed by the Global Climate Observing System (GCOS) in climate change monitoring. In the past two decades, sea level has been routinely measured from space using satellite altimetry techniques. In order to address a number of importan...

  2. Re-assessing the role of plant community change and climate in the PETM n-alkane record

    Science.gov (United States)

    Bush, R. T.; Baczynski, A. A.; McInerney, F. A.; Chen, D.

    2012-12-01

    The terrestrial leaf wax n-alkane record of the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming, shows large excursions in both carbon isotope (δ13C) values and n-alkane average chain length (ACL). At the onset of the PETM, ACL values increase from ~28.5 to ~30.1 while the negative carbon isotope excursion (CIE) is 4-6‰ in magnitude and larger than δ13C records from other materials. It has been hypothesized previously that both the ACL excursion and the large magnitude of the CIE were caused by a concurrent turnover in the local flora from a mixed conifer/angiosperm community before the PETM to a different suite of angiosperm species during the PETM. Here, we present the results of a meta-analysis of data (>2000 data from 89 sources, both published and unpublished) on n-alkane amounts and chain length distributions in modern plants from around the world. We applied the data in two sets of comparisons: 1) within and among plant groups such as herbs and graminoids, and 2) between plants and climate, using reported collection locations for outdoor plants and climate values generated via GIS extraction of WorldClim modeled data. We show that angiosperms, as group, produce more n-alkanes than do gymnosperms by 1-2 orders of magnitude, and this means that the gymnosperm contribution to a mixed soil n-alkane pool would be negligible, even in an ecosystem where gymnosperms dominated (i.e. the pre/post-PETM ecosystems). The modern plant data also demonstrate that turnover of the plant community during the PETM, even among only the angiosperm species, is likely not the source of the observed ACL excursion. First, we constructed "representative" groups of PETM and pre/post-PETM communities using living relative species at the Chicago Botanic Garden and find no significant difference in chain length distributions between the two groups. Second and moreover, the modern plant data reveal that n-alkane chain length distributions are tremendously variable

  3. Coral-based climate records from tropical South Atlantic: 2009/2010 ENSO event in C and O isotopes from Porites corals (Rocas Atoll, Brazil).

    Science.gov (United States)

    Pereira, Natan S; Sial, Alcídes N; Kikuchi, Ruy K P; Ferreira, Valderez P; Ullmann, Clemens V; Frei, Robert; Cunha, Adriana M C

    2015-01-01

    Coral skeletons contain records of past environmental conditions due to their long life span and well calibrated geochemical signatures. C and O isotope records of corals are especially interesting, because they can highlight multidecadal variability of local climate conditions beyond the instrumental record, with high fidelity and sub-annual resolution. Although, in order to get an optimal geochemical signal in coral skeleton, sampling strategies must be followed. Here we report one of the first coral-based isotopic record from the Equatorial South Atlantic from two colonies of Porites astreoides from the Rocas Atoll (offshore Brazil), a new location for climate reconstruction. We present time series of isotopic variation from profiles along the corallite valley of one colony and the apex of the corallite fan of the other colony. Significant differences in the isotopic values between the two colonies are observed, yet both record the 2009/2010 El Niño event - a period of widespread coral bleaching - as anomalously negative δ18O values (up to -1 permil). δ13C is found to be measurably affected by the El Niño event in one colony, by more positive values (+0.39 ‰), and together with a bloom of endolithic algae, may indicate physiological alteration of this colony. Our findings indicate that corals from the Rocas Atoll can be used for monitoring climate oscillations in the tropical South Atlantic Ocean.

  4. Coral-based climate records from tropical South Atlantic: 2009/2010 ENSO event in C and O isotopes from Porites corals (Rocas Atoll, Brazil

    Directory of Open Access Journals (Sweden)

    Natan S. Pereira

    2015-12-01

    Full Text Available ABSTRACT Coral skeletons contain records of past environmental conditions due to their long life span and well calibrated geochemical signatures. C and O isotope records of corals are especially interesting, because they can highlight multidecadal variability of local climate conditions beyond the instrumental record, with high fidelity and sub-annual resolution. Although, in order to get an optimal geochemical signal in coral skeleton, sampling strategies must be followed. Here we report one of the first coral-based isotopic record from the Equatorial South Atlantic from two colonies of Porites astreoides from the Rocas Atoll (offshore Brazil, a new location for climate reconstruction. We present time series of isotopic variation from profiles along the corallite valley of one colony and the apex of the corallite fan of the other colony. Significant differences in the isotopic values between the two colonies are observed, yet both record the 2009/2010 El Niño event - a period of widespread coral bleaching - as anomalously negative δ18O values (up to −1 permil. δ13C is found to be measurably affected by the El Niño event in one colony, by more positive values (+0.39 ‰, and together with a bloom of endolithic algae, may indicate physiological alteration of this colony. Our findings indicate that corals from the Rocas Atoll can be used for monitoring climate oscillations in the tropical South Atlantic Ocean.

  5. Impact of climate variability on terrestrial environment in Western Europe between 45 and 9 kyr cal. BP: vegetation dynamics recorded by the Bergsee Lake (Black Forest, Germany).

    Science.gov (United States)

    Duprat-Oualid, Fanny; Begeot, Carole; Rius, Damien; Millet, Laurent; Magny, Michel

    2016-04-01

    Between 9 and 45 kyr cal. BP, two great transitions lead the global climate system to evolve from the Last-Glacial period (115-14.7 kyr cal. BP), to two successive warmer periods, the Late-Glacial Interstadial (14.7-11.7 kyr cal. BP) and the Holocene (11.7-0 kyr cal. BP). δ18O variations recorded in Greenland ice cores (GRIP & NGRIP) revealed high frequency climate variability within the Last Glacial. These reference isotopic records highlighted a succession of centennial-to-millennial warm/cold events, the so-called Greenland Interstadials (GI) and Greenland Stadials (GS). The number continental records about the period 14.7-0 kyr cal. BP is substantial. This allowed to understand the vegetation dynamics in response to climate changes this period at the North-Atlantic scale. However, sequences covering the glacial period (beyond 20 kyr cal.BP) remain rare, because of hiatuses mostly due to local glaciers. Therefore, sedimentary continuous records of vegetation dynamics are still needed to better understand climate changes during the Last Glacial in Western Europe (Heiri et al. 2014). Here we present a new high-resolution pollen record from Lake Bergsee (47°34'20''N, 7°56'11''E, 382 m a.s.l). This lake is located south of Black Forest and north of the Alps, beyond the zone of glaciers maximal extension. Therefore it could have recorded the whole last climatic cycle, i.e. 120-0 kyr cal. BP. In 2013, a 29 m long core was extracted from the Bergsee. According to the depth-age model based on 14C AMS dating and the Laacher See Tephra (LST), the record spans continuously at least the last 45 kyrs. The first series of pollen analysis, focused on the 45-9 kyr cal. BP time window, allows us to reconstruct a precise, faithful and continuous vegetation history at the centennial scale. This high temporal resolution enabled to assess the response of vegetation to secular climate events (e.g. GI-4 = 200 yrs). First, our results show that vegetation responded to climate

  6. Climatically driven variations in glacier extent as documented by the laminated proglacial sediment record from Lago del Desierto (Southern Patagonia, Argentina)

    Science.gov (United States)

    Enters, D.; Kastner, S.; Ohlendorf, C.; Haberzettl, T.; Kuhn, G.; Lücke, A.; Mayr, C.; Reyss, J.; Wastegard, S.

    2009-12-01

    The climate of southernmost South America is strongly affected by shifts in polar and mid-latitude pressure fields which are expressed in variations of the Southern Hemispheric Westerlies and the Antarctic Oscillation. Next to marine records and Antarctic ice cores this continental area is important to reveal hemispheric and global climate trends. As instrumental climate records from this region are generally short and scarce, environmental archives are the only source of providing long-term records of climate variations. In the northern hemisphere, proglacial lakes have shown to be excellent sources of palaeoenvironmental and palaeoclimatic information. In this study, we evaluate the potential of the laminated proglacial sediment sequence from Lago del Desierto (49°02’S, 72°51’W) as a palaeoclimate archive. Lago del Desierto is situated in the climatically sensitive area of Southern Patagonia close to the South Patagonian Ice Field. Two parallel gravity cores (max. length 283 cm) were analysed using a multi-proxy approach. Radiometric dating (14C, 210Pb and 137Cs) and tephrochronology document that the recovered sediments cover the last 2000 years. After exclusion of numerous event layers, the sedimentological, mineralogical, and geochemical datasets reveal a long-term trend of runoff variations and sediment accessibility controlled by changes in temperature and precipitation. An abrupt lithological change visible in sediments mineralogy and geochemistry occurred around AD 850 and is interpreted as a rearrangement in sediment availability and transfer rates related to the beginning exposure of formerly glaciated areas. Thereafter, the Medieval Climate Anomaly (MCA) period, the Little Ice Age (LIA) cooling and the subsequent 20th century warming can be traced in the sediment record corresponding to the overall trend observed for southern South America. The increased minerogenic input and a higher frequency of event layers mirror the onset of warmer climate

  7. The Chew Bahir Drilling Project (HSPDP). Deciphering climate information from the Chew Bahir sediment cores: Towards a continuous half-million year climate record near the Omo - Turkana key palaeonanthropological Site

    Science.gov (United States)

    Foerster, Verena E.; Asrat, Asfawossen; Chapot, Melissa S.; Cohen, Andrew S.; Dean, Jonathan R.; Deino, Alan; Günter, Christina; Junginger, Annett; Lamb, Henry F.; Leng, Melanie J.; Roberts, Helen M.; Schaebitz, Frank; Trauth, Martin H.

    2017-04-01

    As a contribution towards an enhanced understanding of human-climate interactions, the Hominin Sites and Paleolakes Drilling Project (HSPDP) has successfully completed coring five dominantly lacustrine archives of climate change during the last 3.5 Ma in East Africa. All five sites in Ethiopia and Kenya are adjacent to key paleoanthropological research areas encompassing diverse milestones in human evolution, dispersal episodes, and technological innovation. The 280 m-long Chew Bahir sediment records, recovered from a tectonically-bound basin in the southern Ethiopian rift in late 2014, cover the past 550 ka of environmental history, a time period that includes the transition to the Middle Stone Age, and the origin and dispersal of modern Homo sapiens. Deciphering climate information from lake sediments is challenging, due to the complex relationship between climate parameters and sediment composition. We will present the first results in our efforts to develop a reliable climate-proxy tool box for Chew Bahir by deconvolving the relationship between sedimentological and geochemical sediment composition and strongly climate-controlled processes in the basin, such as incongruent weathering, transportation and authigenic mineral alteration. Combining our first results from the long cores with those from a pilot study of short cores taken in 2009/10 along a NW-SE transect of the basin, we have developed a hypothesis linking climate forcing and paleoenvironmental signal-formation processes in the basin. X-ray diffraction analysis of the first sample sets from the long Chew Bahir record reveals similar processes that have been recognized for the uppermost 20 m during the pilot-study of the project: the diagenetic illitization of smectites during episodes of higher alkalinity and salinity in the closed-basin lake induced by a drier climate. The precise time resolution, largely continuous record and (eventually) a detailed understanding of site specific proxy formation

  8. CERES Top-of-Atmosphere Earth Radiation Budget Climate Data Record: Accounting for in-Orbit Changes in Instrument Calibration

    Directory of Open Access Journals (Sweden)

    Norman G. Loeb

    2016-02-01

    Full Text Available The Clouds and the Earth’s Radiant Energy System (CERES project provides observations of Earth’s radiation budget using measurements from CERES instruments onboard the Terra, Aqua and Suomi National Polar-orbiting Partnership (S-NPP satellites. As the objective is to create a long-term climate data record, it is necessary to periodically reprocess the data in order to incorporate the latest calibration changes and algorithm improvements. Here, we focus on the improvements and validation of CERES Terra and Aqua radiances in Edition 4, which are used to generate higher-level climate data products. Onboard sources indicate that the total (TOT channel response to longwave (LW radiation has increased relative to the start of the missions by 0.4% to 1%. In the shortwave (SW, the sensor response change ranges from −0.4% to 0.6%. To account for in-orbit changes in SW spectral response function (SRF, direct nadir radiance comparisons between instrument pairs on the same satellite are made and an improved wavelength dependent degradation model is used to adjust the SRF of the instrument operating in a rotating azimuth plane scan mode. After applying SRF corrections independently to CERES Terra and Aqua, monthly variations amongst these instruments are highly correlated and the standard deviation in the difference of monthly anomalies is 0.2 Wm−2 for ocean and 0.3 Wm−2 for land/desert. Additionally, trends in CERES Terra and Aqua monthly anomalies are consistent to 0.21 Wm−2 per decade for ocean and 0.31 Wm−2 per decade for land/desert. In the LW, adjustments to the TOT channel SRF are made to ensure that removal of the contribution from the SW portion of the TOT channel with SW channel radiance measurements during daytime is consistent throughout the mission. Accordingly, anomalies in day–night LW difference in Edition 4 are more consistent compared to Edition 3, particularly for the Aqua land/desert case.

  9. A stratigraphic framework for naming and robust correlation of abrupt climatic changes during the last glacial period based on three synchronized Greenland ice core records

    Science.gov (United States)

    Rasmussen, Sune O.

    2014-05-01

    Due to their outstanding resolution and well-constrained chronologies, Greenland ice core records have long been used as a master record of past climatic changes during the last interglacial-glacial cycle in the North Atlantic region. As part of the INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. This is based on a combination of isotope ratios (δ18O, reflecting mainly local temperature) and calcium concentrations (reflecting mainly atmospheric dust loading). In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. This is a key step aimed at promoting unambiguous comparison and correlation between different proxy records, as well as a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is under review for publication in Quaternary Science Reviews. Author team: S

  10. New insights on the anatomy of abrupt climate changes based on high-resolution ice core records from NorthGRIP (Greenland)

    Science.gov (United States)

    Capron, E.; Rasmussen, S.; Popp, T. J.; Vaughn, B. H.; Gkinis, V.; Erhardt, T.; Fischer, H.; Blunier, T.; Landais, A.; Pedro, J. B.; Steffensen, J. P.; Svensson, A.; Vinther, B.

    2016-12-01

    The millennial-scale succession of Greenland Stadials (GS) and Greenland Interstadials (GI) illustrates the Greenland expression of the well-known sequence of Dansgaard-Oeschger (DO) events, within which we observe additional climate variations of decadal to centennial-scale duration. Various paradigms, mostly based on interactions between the cryosphere and the ocean, have been proposed to explain the existence and evolution of DO events. Annual to decadal scale records of environmental and climatic regional changes over the rapid transitions are needed to assess whether climate model outputs based on a particular mechanism are consistent with the observed spatial pattern and temporal phasing. Here we present new multiannual resolution stable water isotope measurements (ice δ18O and δD) and annually resolved ion chemistry records from the NorthGRIP ice core. Because these tracers imprint the signatures of different parts of the Northern Hemisphere climate system, we can map the anatomy - the spatial and temporal signature of climate and environmental changes - associated with abrupt transitions (from GS to GI and vice-versa) occurring during Marine Isotopic Stage (MIS) 4. We determine via a statistical approach the timing and duration of the transitions, along with the amplitude of the local and regional changes associated with each Greenland warming and cooling phase. We quantify similarities and differences in the sequences of events through a comparison with results obtained for MIS 3 abrupt transitions and results from the NEEM ice core for selected transitions. The anatomy of abrupt climate changes appears to be different from one event to the next, suggesting that the mechanisms at play are not identical for all of them. We discuss the possible influence of (1) the Heinrich Stadials (i.e. GS during which a Heinrich Event occurred) and of (2) the long term evolution of the climate system on the different decadal to centennial-scale sequences of events

  11. Interannual and orbital-scale climate variability in the early Miocene: Compound-specific D/H records from the Foulden Maar Diatomite, New Zealand

    Science.gov (United States)

    D'Andrea, W. J.; Fox, B.; Lee, D.

    2013-12-01

    The El Niño-Southern Oscillation (ENSO) cycle is the most important interannual climate variation on Earth and has far reaching impacts on global climate. However, the behavior of ENSO over orbital timescales and under different global climate states is poorly understood and controversial. It has been proposed that ENSO behaved much differently in the past, perhaps even transitioning toward a permanent El Niño-like state. Our understanding of the ENSO response to orbital variations and the background climate state is incomplete and there are fundamental flaws in our knowledge of this important player in Earth's climate system. Here we present a 100,000-yr long compound-specific hydrogen isotope (D/H) record along with varve thickness data that document southern New Zealand (46°S, 170°E) climate in the early Miocene; the results suggest modulation of ENSO by Earth's orbital changes at precession (~22,000 year) and semiprecession (~11,000 year) timescales. Our data come from analyses of the Foulden Maar Diatomite, an annually laminated sediment sequence from an early Miocene freshwater lake in Otago, New Zealand. The diatomite contains approximately 100,000 dark-light couplets interpreted as biogenic varves, and has exquisite preservation of leaves, flowers, insects, diatom frustules and n-alkanoic acids derived from leaf waxes and algae. D/H records from n-alkanoic acids reveal large variations corresponding to precession (~22,000 yrs) and semi-precession (~11,000 yrs) timescales that reflect large paleohydrological changes. Varve thickness records reveal spectral power that exceeds the 99% confidence limit in the 3 to 7-yr band, and indicate that ENSO was an important driver of interannual climate variability in southern New Zealand during the early Miocene. We propose that the semiprecession-paced hydrologic changes represented by our compound-specific D/H record document the modulation of ENSO by variations in Earth's orbital configuration; specifically, that

  12. Links between climate and the transmission times of biomarker signals to aquatic sediments: Implications for interpretation of the sedimentary record (Invited)

    Science.gov (United States)

    Eglinton, T. I.

    2010-12-01

    The abundances and stable isotopic signatures of biomarker compounds preserved in aquatic sediments are increasingly being used to infer a diverse array of paleoenvironmental and paleoclimatic information. With continuing analytical advances and development of streamlined methodological approaches, there is growing emphasis on biomarker-based reconstructions of past climate at high temporal resolution, and as part of multi-proxy investigations. Crucial to the accurate interpretation of such records is a robust understanding of the provenance of the molecular signals. There is also often an implicit assumption that the delivery of these signals from their biological source to the sedimentary archive is virtually instantaneous. However, there is growing evidence from biomarker-specific radiocarbon measurements that transport may take several hundred to several thousand years. In the case of markers of vascular plant vegetation, storage in soils and at other locations within terrestrial drainage basins may induce significant temporal lags, while in the marine environment episodes of sediment resuspension and redistribution prior to burial have also been inferred to create significant temporal offsets in algal biomarker sedimentary records. The magnitude of such temporal lags may also vary as a function of climate, potentially yielding complex age relationships between proxy records through time. This presentation will present several case studies using molecular-level 14C measurements in order to explore the interplay between biomarker signal transmission times and past climate variability. The implications for interpretation of biomarker records and the additional information that may be embedded within temporal relationships between sedimentary components will be discussed.

  13. Phenological Records

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Phenology is the scientific study of periodic biological phenomena, such as flowering, breeding, and migration, in relation to climatic conditions. The few records...

  14. The Holocene Sedimentary Record of Climate Change from Gualas Glacier, Golfo Elefantes, Northern Patagonia (46.5°S)

    Science.gov (United States)

    Fernandez-Vasquez, R. A.; Anderson, J. B.; Bertrand, S.; Wellner, J. S.

    2010-12-01

    Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield (NPI), one of the largest temperate ice bodies on Earth. NPI is nourished by moisture from the Pacific Ocean, which is transported by the southern hemisphere Westerlies and results in year-round precipitation. This system also creates a strong West to East gradient due to the rain shadow effect of the Andes (Warren, 1993). Most glaciers of the NPI, including Gualas Glacier, are currently receding from their historical maximum position, which was reached during the northern hemisphere Little Ice Age (LIA) (Harrison and Winchester, 2000). However, virtually nothing is known about the Holocene behavior of NPI outlet glaciers prior to the LIA, although it is generally assumed that they followed the pattern of Neoglacial advances described for the Southern Patagonian Icefield (SPI) by Mercer (1965, 1968, 1976). The lack of data in this sensitive area of the Patagonian Andes, the only continental cordillera in the Southern Hemisphere that intersects the entire Westerly Wind Belt, limits our understanding of climate processes that relate mid-latitude circulation patterns with low and high latitudes as well as the inter-hemispheric coupling of climate changes. We present the results of a marine geological survey at Golfo Elefantes, the depositional basin of Gualas Glacier. The dataset includes swath bathymetry, single channel seismic data and sediment cores analyses. The studied sedimentary record spans, with some hiatuses, at least the last 10.5 Ka. No evidences of ice proximal or till deposits were found in the area, and seismic records show no evidence of basin-wide erosional hiatuses. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes, which have been suggested to represent Neoglacial advances of Gualas Glacier, were instead formed during the waning stages of the local LGM (Late Pleistocene) after ~12.6 ka according to paleogeographical reconstructions

  15. A Climate-Data Record (CDR) of the "Clear-Sky" Surface Temperature of the Greenland Ice Sheet

    Science.gov (United States)

    Hall, Dorothy K.; Comiso, Josefino C.; DiGirolamo, Nocolo E.; Shuman, Christopher A.

    2011-01-01

    We have developed a climate-data record (CDR) of "clear-sky" ice-surface temperature (IST) of the Greenland Ice Sheet using Moderate-Resolution Imaging Spectroradiometer (MODIS) data. The CDR provides daily and monthly-mean IST from March 2000 through December 2010 on a polar stereographic projection at a resolution of 6.25 km. The CDR is amenable to extension into the future using Visible/Infrared Imager Radiometer Suite (VIIRS) data. Regional "clear-sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57 +/- 0.02 to 0.72 +/- 0.1 c per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near O C during the melt season, and is thus vulnerable to rapid melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue affecting potentially billions of people worldwide. The IST CDR will provide a convenient data set for modelers and for climatologists to track changes of the surface temperature of the ice sheet as a whole and of the individual drainage basins on the ice sheet. The daily and monthly maps will provide information on surface melt as well as "clear-sky" temperature. The CDR will be further validated by comparing results with automatic-weather station data and with satellite-derived surface-temperature products.

  16. A Climate-Data Record (CDR) of the "Clear Sky" Surface Temperature of the Greenland Ice Sheet

    Science.gov (United States)

    Hall, Dorothy K.; Comiso, J. C.; DiGirolamo, N. E.; Shuman, C. A.

    2011-01-01

    To quantify the ice-surface temperature (IST) we are developing a climate-data record (CDR) of monthly IST of the Greenland ice sheet, from 1982 to the present using Advanced Very High Resolution Radiometer (AVHRR) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data at 5-km resolution. "Clear-sky" surface temperature increases have been measured from the early 1980s to the early 2000s in the Arctic using AVHRR data, showing increases ranging from 0.57-0.02 (Wang and Key, 2005) to 0.72 0.10 deg C per decade (Comiso, 2006). Arctic warming has implications for ice-sheet mass balance because much of the periphery of the ice sheet is near 0 deg C in the melt season and is thus vulnerable to more extensive melting (Hanna et al., 2008). The algorithm used for this work has a long history of measuring IST in the Arctic with AVHRR (Key and Haefliger, 1992). The data are currently available from 1981 to 2004 in the AVHRR Polar Pathfinder (APP) dataset (Fowler et al., 2000). J. Key1NOAA modified the AVHRR algorithm for use with MODIS (Hall et al., 2004). The MODIS algorithm is now being processed over Greenland. Issues being addressed in the production of the CDR are: time-series bias caused by cloud cover, and cross-calibration between AVHRR and MODIS instruments. Because of uncertainties, time series of satellite ISTs do not necessarily correspond with actual surface temperatures. The CDR will be validated by comparing results with in-situ (see Koenig and Hall, in press) and automatic-weather station data (e.g., Shuman et al., 2001).

  17. Development of a Climate-Data Record (CDR) of the Surface Temperature of the Greenland Ice Sheet

    Science.gov (United States)

    Hall, Dorthy K.; Comiso, Josefino C.; Shuman, Christopher A.; DiGirolamo, Nicolo E.; Stock, Larry V.

    2010-01-01

    Regional "clear sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57+/-0.02 deg C to 72+/-0.10 deg C per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near 0 deg C during the melt season, and is thus vulnerable to rapid melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue affecting potentially billions of people worldwide. To quantify the ice-surface temperature (IST) of the Greenland Ice Sheet, and to provide an IST dataset of Greenland for modelers that provides uncertainties, we are developing a climate-data record (CDR) of daily "clear-sky" IST of the Greenland Ice Sheet, from 1982 to the present using AVHRR (1982 - present) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data (2000 - present) at a resolution of approximately 5 km. Known issues being addressed in the production of the CDR are: time-series bias caused by cloud cover (surface temperatures can be different under clouds vs. clear areas) and cross-calibration in the overlap period between AVHRR instruments, and between AVHRR and MODIS instruments. Because of uncertainties, mainly due to clouds, time-series of satellite IST do not necessarily correspond with actual surface temperatures. The CDR will be validated by comparing results with automatic-weather station data and with satellite-derived surface-temperature products and biases will be calculated.

  18. Climatic warming in China during 1901-2015 based on an extended dataset of instrumental temperature records

    Science.gov (United States)

    Cao, Lijuan; Yan, Zhongwei; Zhao, Ping; Zhu, Yani; Yu, Yu; Tang, Guoli; Jones, Phil

    2017-05-01

    Monthly mean instrumental surface air temperature (SAT) observations back to the nineteenth century in China are synthesized from different sources via specific quality-control, interpolation, and homogenization. Compared with the first homogenized long-term SAT dataset for China by Cao et al (2013), which contained 18 stations mainly located in the middle and eastern part of China, the present dataset includes homogenized monthly SAT series at 32 stations, with an extended coverage especially towards western China. Missing values are interpolated by using observations at nearby stations, including those from neighboring countries. Cross validation shows that the mean bias error (MBE) is generally small and falls between 0.45 °C and -0.35 °C. Multiple homogenization methods and available metadata are applied to assess the consistency of the time series and to adjust inhomogeneity biases. The homogenized annual mean SAT series shows a range of trends between 1.1 °C and 4.0 °C/century in northeastern China, between 0.4 °C and 1.9 °C/century in southeastern China, and between 1.4 °C and 3.7 °C/century in western China to the west of 105 E (from the initial years of the stations to 2015). The unadjusted data include unusually warm records during the 1940s and hence tend to underestimate the warming trends at a number of stations. The mean SAT series for China based on the climate anomaly method shows a warming trend of 1.56 °C/century during 1901-2015, larger than those based on other currently available datasets.

  19. An Evaluation of Antarctica as a Calibration Target for Passive Microwave Satellite Missions with Climate Data Record Applications

    Science.gov (United States)

    Kim, Edward

    2011-01-01

    Passive microwave remote sensing at L-band (1.4 GHz) is sensitive to soil moisture and sea surface salinity, both important climate variables. Science studies involving these variables can now take advantage of new satellite L-band observations. The first mission with regular global passive microwave observations at L-band is the European Space Agency's Soil Moisture and Ocean Salinity (SMOS), launched November, 2009. A second mission, NASA's Aquarius, was launched June, 201 I. A third mission, NASA's Soil Moisture Active Passive (SMAP) is scheduled to launch in 2014. Together, these three missions may provide a decade-long data record-provided that they are intercalibrated. The intercalibration is best performed at the radiance (brightness temperature) level, and Antarctica is proving to be a key calibration target. However, Antarctica has thus far not been fully characterized as a potential target. This paper will present evaluations of Antarctica as a microwave calibration target for the above satellite missions. Preliminary analyses have identified likely target areas, such as the vicinity of Dome-C and larger areas within East Antarctica. Physical sources of temporal and spatial variability of polar firn are key to assessing calibration uncertainty. These sources include spatial variability of accumulation rate, compaction, surface characteristics (dunes, micro-topography), wind patterns, and vertical profiles of density and temperature. Using primarily SMOS data, variability is being empirically characterized and attempts are being made to attribute observed variability to physical sources. One expected outcome of these studies is the potential discovery of techniques for remotely sensing--over all of Antarctica-parameters such as surface temperature.

  20. Long-term Records of Pacific Salmon Abundance From Sediment Core Analysis: Relationships to Past Climatic Change, and Implications for the Future

    Science.gov (United States)

    Finney, B.

    2002-12-01

    The response of Pacific salmon to future climatic change is uncertain, but will have large impacts on the economy, culture and ecology of the North Pacific Rim. Relationships between sockeye salmon populations and climatic change can be determined by analyzing sediment cores from lakes where sockeye return to spawn. Sockeye salmon return to their natal lake system to spawn and subsequently die following 2 - 3 years of feeding in the North Pacific Ocean. Sockeye salmon abundance can be reconstructed from stable nitrogen isotope analysis of lake sediment cores as returning sockeye transport significant quantities of N, relatively enriched in N-15, from the ocean to freshwater systems. Temporal changes in the input of salmon-derived N, and hence salmon abundance, can be quantified through downcore analysis of N isotopes. Reconstructions of sockeye salmon abundance from lakes in several regions of Alaska show similar temporal patterns, with variability occurring on decadal to millennial timescales. Over the past 2000 years, shifts in sockeye salmon abundance far exceed the historical decadal-scale variability. A decline occurred from about 100 BC - 800 AD, but salmon were consistently more abundant 1200 - 1900 AD. Declines since 1900 AD coincide with the period of extensive commercial fishing. Correspondence between these records and paleoclimatic data suggest that changes in salmon abundance are related to large scale climatic changes over the North Pacific. For example, the increase in salmon abundance c.a. 1200 AD corresponds to a period of glacial advance in southern Alaska, and a shift to drier conditions in western North America. Although the regionally coherent patterns in reconstructed salmon abundance are consistent with the hypothesis that climate is an important driver, the relationships do not always follow patterns observed in the 20th century. A main feature of recorded climate variability in this region is the alternation between multi-decade periods of

  1. The Y. D. and climate abrupt events in the early and middle Holocene: Stalagmite oxygen isotope record from Maolan, Guizhou, China

    Institute of Scientific and Technical Information of China (English)

    QIN Jiaming; YUAN Daoxian; CHENG Hai; LIN Yushi; ZHANG Meiliang; WANG Fuxing; R. L. Edwards; WANG Hua; RAN Jingcheng

    2005-01-01

    The isotope records which range from 3.9 kaBP to 15.7 kaBP with an average resolution of 90 a have been obtained from 45 cm to 193.6 cm of the upper part of D4 stalagmite from Dongguo Cave in Libo, Guizhou, by using system TIMS U-series dating and carbon and oxygen stable isotope analyses.The study indicates that the last cold event, the YD (Younger Dryas) event, of the last glacial period was apparently shown in D4 record, which started from 12.80 kaBP and ended in 11.58 kaBP, with a great range of drop in temperature. The end of the last glacial period was consistent with the termination I in oceanic isotope records and was with time limit of 11.3 kaBP. The three most distinct cold events in the early and middle Holocene occurred respectively in 10.91 kaBP, 8.27 kaBP and 4.75 kaBP, with a range of drop in temperature reaching 2-5℃. The climate abrupt events in thousand and hundred years scale recorded in stalagmite δ18O can be compared to those in GISP2 ice cores from Greenland in their happening time and the range of their lasting time. The cold events in 8.27 kaBP and 4.75 kaBP can also be compared to CC3 stalagmite records in Ireland, which indicate that climate changes of short range in China monsoon areas, western Europe and polar regions, have the same driving factor. This has a global significance. In addition, the trend of record curves in some time- stages is apparently different, which reflects probably the difference between environment in monsoon climate areas and in polar regions.

  2. Community benthic paleoecology from high-resolution climate records: Mollusca and foraminifera in post-glacial environments of the California margin

    Science.gov (United States)

    Myhre, Sarah E.; Kroeker, Kristy J.; Hill, Tessa M.; Roopnarine, Peter; Kennett, James P.

    2017-01-01

    Paleoecological reconstructions of past climate are often based on a single taxonomic group with a consistent presence. Less is known about the relationship between multi-taxon community-wide change and climate variability. Here we reconstruct paleoecological change in a Late Quaternary (16.1-3.4 ka) sediment core from the California margin (418 m below sea level) of Santa Barbara Basin (SBB), USA, using Mollusca (Animalia) and Foraminifera (Rhizaria) microfossils. Building upon previous investigations, we use multivariate ordination and cluster analyses to interpret community-scale changes in these distinctly different taxonomic groups across discrete climate episodes. The strongest differences between seafloor biological communities occurred between glacial (prior to Termination IA, 14.7 ka) and interglacial climate episodes. Holocene communities were well partitioned, indicating that sub-millennial oceanographic variability was recorded by these microfossils. We document strong evidence of chemosynthetic trophic webs and sulfidic environments (from gastropod Alia permodesta and bivalve Lucinoma aequizonata), which characterized restricted intervals previously interpreted as well oxygenated (such as the Pre-Bølling Warming). Mollusc records indicate first-order trophic energetic shifts between detrital and chemosynthetically-fixed carbon. Molluscs associated with widely different physiological preferences occur here within single, decadal intervals of sediment, and as such mollusc assemblages may reflect significant inter-decadal oceanographic variability. Foraminifera assemblages provide exceptional records of the sequential, chronological progression of the deglacial climatic and oceanographic events, whereas mollusc assemblages reflect non-chronological similarities in reoccurring communities. Foraminifera taxa that drive community similarity here are also independently recognized as marker species for seafloor hypoxia regimes, which provides support for the

  3. Speleothem records of glacial/interglacial climate from Iran forewarn of future Water Availability in the interior of the Middle East

    Science.gov (United States)

    Mehterian, Sevag; Pourmand, Ali; Sharifi, Arash; Lahijani, Hamid A. K.; Naderi, Majid; Swart, Peter K.

    2017-05-01

    This study presents the first absolute-dated record of climate variability constructed by oxygen isotopes (δ18Oc) from stalagmites in the interior of West Asia (Middle East) that encompass the Last Interglacial and early glacial periods (73,000-127,000 Before Present, BP) and early Holocene (6500-7500 BP). Variations in δ18Oc of two stalagmites from Qal'e Kord (QK) cave in central NW Iran show significant agreement and follow the solar insolation curve at 30°N closely, indicating the fidelity of these records as climate signals. The stalagmites capture millennial-scale Dansgaard/Oeschger stadial and interstadial events (19-25) observed in the North Greenland Ice Core Project (NGRIP). These observations point to the presence of a strong atmospheric teleconnection between the north Atlantic climate and the Middle East region. Variations in δ18Oc from QK cave also agree with the main features of Marine Isotope Stage 5 (MIS5), climate reconstructions from Soreq Cave, Israel, and Sanbao Cave in East Asia. This suggests propagation of a pan-Eurasian climate signal via interplay between changes in solar insolation, strength and position of the mid-latitude Westerly Jet, and strength of the Asian Monsoon. More negative δ18Oc from QK stalagmites are representative of wetter conditions when JJA insolation is at maximum, supporting a hypothesis that winter precipitation should increase in the Mediterranean storm tracks over the interior of West Asia when seasonality is at maximum. This record of water availability from central NW Iran across past glacial cycles suggests precipitation increased with higher solar insolation, an orbital configuration that will not return for another 10,000 years.

  4. Record of Volcanism Since 7000 B.C. from the GISP2 Greenland Ice Core and Implications for the Volcano-Climate System.

    Science.gov (United States)

    Zielinski, G A; Mayewski, P A; Meeker, L D; Whitlow, S; Twickler, M S; Morrison, M; Meese, D A; Gow, A J; Alley, R B

    1994-05-13

    Sulfate concentrations from continuous biyearly sampling of the GISP2 Greenland ice core provide a record of potential climate-forcing volcanism since 7000 B.C. Although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions, only about 30 percent of the events from 1 to 7000 B.C. were matched to such events. Several historic eruptions may have been greater sulfur producers than previously thought. There are three times as many events from 5000 to 7000 B.C. as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions. This increased volcanism in the early Holocene may have contributed to climatic cooling.

  5. Records of natural fire and climate history during the last three glacial-interglacial cycles around the South China Sea Charcoal record from the ODP 1144

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The history of natural fire and its relationship to climate during the last three gla cial-interglacial cycles in the Southern coast areas of China and the northern continental shelf of the South China Sea (SCS) are discussed based on the statistic study of charcoal particles and associated pollen data from ODP 1144 Site (20° 3′N, 117° 25′E, 2037 m in water depth). Accord ing to the results of the charcoal and pollen study, the sediments from the upper 225 m are divided into 8 zones (C1-8), which might be correlated with the Marine Isotope Stage 1-8 (MIS1-8)respectively. Our study indicates that during the last glacial period (MIS2, 4), the influx of charcoal particle was much higher than that from the interglacial period, suggesting strong occurrence of natural fire and dry climate. During MIS 6 and MIS 8 (C6, C8), although the influx of fine charcoal particles was quite high, the influx of the coarse and medium charcoal particle were much low,which might be due to the smaller source area of fire probably resulting from the limited exposure of the continental shelf before MIS5. During the interglacial period (MIS1, 5, 7), the influxes of charcoal particles were much lower, implying dropping of intensity of the natural fire and then a humid climate. Another reason is that the continental shelf was submerged into the sea during the interglacial periods, and the source areas of fire were reduced then. Although the influx of the fine charcoal particles was much lower during MIS3, the influx of the coarse and medium charcoal par ticles were almost equal to those of MIS4 (C4), which suggests that the intensity of the natural fire remained quite high and the climate was considerably dry during that period.

  6. A Sub-Decadal Continental Margin Record of Little Ice Age-to-Modern Climate-Induced Changes in Sediment Delivery and Transport in the Gulf of Alaska

    Science.gov (United States)

    Jaeger, J. M.; Viene, W.; Finney, B.; Stoner, J.; Evans, H.

    2003-12-01

    The Gulf of Alaska (GOA) margin is one of the few locations on Earth where orogenic processes, glacial climate, and continental margin sedimentation can be studied and quantitatively modeled in unison. Climatic changes control glacial dynamics, erosion, and sediment/meltwater fluxes to the ocean, and GOA margin strata appear to preserve a strong record of terrestrial climate (i.e., temperature and precipitation) as well as paleoceanographic signals on seasonal to tectonic time scales. In collaboration with the GOA-NEP GLOBEC program, gravity cores were collected at key sampling sites under the influence of the climatically sensitive Alaska Coastal Current (ACC). Chronologies for the past 400-y were established using Pb-210/Cs-137, coupled with paleo-and-environmental magnetism analyzed from u-channel samples at one-cm intervals. The sedimentary paleomagnetic record is correlated to the Sitka geomagnetic observatory record for the last century and extended using the Jackson et al. 400-yr global field model. Carbon and nitrogen stable isotopes, C/N ratios and opal concentrations were analyzed to determine OM source and paleoproductivity. Proximal to large sediment sources, high (>1 cm/y) sediment accumulation rates vary over decadal times scales and appear to be directly tied to the amount of coastal precipitation and the corresponding strength of the ACC. Distal shelf cores have sedimentation rates that vary over longer time scales and are 2-3 x higher during glacial melting from LIA maxima. High-resolution grain size analyses and core logging of bulk density and environmental magnetic parameters including magnetic susceptibility vary at LIA, pentadecadal, and decadal time scales and are strongly correlated with variability in regional precipitation as seen in the nearby Mt. Logan ice core record. Preliminary results suggest that the amount of freshwater discharge and corresponding strength of the ACC was substantially higher during the LIA.

  7. North Atlantic climatic changes reflected in the Late Quaternary foraminiferal abundance record of the Andaman Sea, north-eastern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sijinkumar, A.V.; Nath, B.N.; Clemens, S.

    Plateau and the tropical Indian Ocean. Marzin et al. (2013) shows that the events of high salinity are associated with weak Indianmonsoon circulation during cold events in the North Atlan- tic and Arctic. Themechanism involves increased freshwater flux... isotope records. Our intention is to study the response of planktonic and benthic fo- raminifera of Andaman Sea to rapid climatic events of the North Atlan- tic. We employed the abundance variations of Globigerina rubescens, Neogloboquadrina dutertrei...

  8. Vegetation and climate in Southern Hemisphere mid-latitudes since 210 ka: new insights from marine and terrestrial pollen records from New Zealand

    Science.gov (United States)

    Ryan, M. T.; Dunbar, G. B.; Vandergoes, M. J.; Neil, H. L.; Hannah, M. J.; Newnham, R. M.; Bostock, H.; Alloway, B. V.

    2012-08-01

    Paleo-vegetation records developed from marine sedimentary sequences offer considerable potential for examining changes in terrestrial climate beyond the range of 14C dating because they can be independently dated by δ18O stratigraphy. Here we present the first pollen record of vegetation from a marine core site in the Tasman Sea, TAN0513-14 (42°18'S, 169°53'E), ˜110 km west of New Zealand's South Island. An independent chronology provided by correlating the Globigerina bulloides δ18O record at TAN0513-14 to a global isotope stack shows that the record extends back to 210 ka. Glacial to interglacial changes in palynomorph content are characterised by shrub and podocarp-broadleaf forest taxa respectively and are correlated with similar changes in the ca 150 kyr-long terrestrial pollen record from Okarito Pakihi (bog), 110 km to the south southeast. Both records are placed on the same timescale by matching variations in Dacrydium cupressinum and Fuscospora between sites, with a unique tie point provided by the ca 25.4 ka Kawakawa Tephra. Our Southern Hemisphere mid-latitude vegetation records show forest extent is greatest during periods of low ice volume, high mean annual sea surface temperature (MASST) and anti-phased with local insolation intensity. However, there are several features not attributable to changes in mean annual temperature. First, a fundamental change in forest composition occurred at Termination II (TII), with a loss of southern beech (Nothofagus) from the study area. Second, the amplitude of MASST change through MIS 5 is not reflected in corresponding changes in forest extent, suggesting other feature(s) of regional climate (seasonality, frostiness, ice cover) exert important controls over vegetation patterns at these latitudes.

  9. Holocene climate change evidence from high-resolution loess/paleosol records and the linkage to fire-climate change-human activities in the Horqin dunefield in northern China

    Science.gov (United States)

    Mu, Yan; Qin, Xiaoguang; Zhang, Lei; Xu, Bing

    2016-05-01

    The combination of high-resolution sedimentary paleoclimate proxies of total organic carbon and magnetic susceptibility of a loess/paleosol section with black carbon (BC) records provides us with information about climate change and the linkage of fire-climate change-vegetation-human activities in the Horqin dunefield over the past 11,600 cal yr BP. We found that during 11,600-8000 cal yr BP (the early Holocene), the area was dominated by a dry climate. The vegetation coverage was low, which limited the extent of fire. The Holocene optimum can be placed between 8000 and 3200 cal yr BP, and during this period, anthropogenic fire was a key component of total fire occurrence as the intensity of human activity increased. The development of agricultural activities and the growing population during this period increased the use of fire for cooking food and burning for cultivation and land fertilization purposes. During 2800-2600 cal yr BP, a warm/moister climate prevailed and was associated with a high degree of pedogenesis and vegetation cover density, evident at 2700 cal yr BP. Fires may have contributed to human survival by enabling the cooking of food in the warm and wet climate. In the period since 2000 cal yr BP, fires linked to agriculture may have led to increased biomass burning associated with agricultural activity.

  10. Mixing it Up: A Record of Holocene Climate Change in Non-Annually Laminated Sediment of Seneca Lake, NY

    Science.gov (United States)

    Rogers, C. E.; Curtin, T. M.

    2005-12-01

    The mid to late Holocene climate record was examined in two cores that represent distal sedimentation in Seneca Lake, one of 11 Finger Lakes in western New York. Laminated sediments, ~5 m thick, were collected from the middle of the lake at 131-137 m water depths. These sites were selected because they preserve a continuous record of changes in the hydrologic balance and sedimentary processes. Variations in grain size and fabric at 50-100-cm intervals were observed and represent time periods of hundreds to thousands of years. The combination of magnetic susceptibility, loss-on-ignition, grain size analysis by laser diffraction, and grain fabric analysis using thin sections allow us to reconstruct the evolution of the lake since deglaciation and to compare and contrast paleoclimate indicator data. Variations in the type of sedimentary fabrics preserved are coincident with variations in geochemical and sedimentological indicators of environmental conditions that may have occurred in response to fluctuations in the hydrologic balance and circulation and/or overturn. Laterally continuous, thin, black laminae rich in organic matter and possibly minute grains of iron sulfides accumulated during the mid Holocene Hypsithermal (~9-7 ka). Presence of black laminae may signify a steady supply of organic matter and an absence of oxygen, at least below the sediment-water interface if not in the lower part of the water column. Coincident with finely laminated sediment are the coarsest mean grain sizes. Three 2-6 cm thick sand beds occur in one core, suggesting that an influx of water and sediment occurred during intense storms. A combination of warmer surface water and influx of freshwater from storms during the Hypsithermal may have influenced the turnover history of the lake by stabilizing the water column. Absence of overturn would result in depletion of nutrients in surface waters, a decrease in primary productivity, and a decrease in oxygen at the bottom of the lake as a

  11. Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

    National Research Council Canada - National Science Library

    Capron, E; Landais, A; Chappellaz, J; Schilt, A; Buiron, D; Dahl-Jensen, D; Johnsen, S. J; Jouzel, J; Lemieux-Dudon, B; Loulergue, L; Leuenberger, M; Masson-Delmotte, V; Meyer, H; Oerter, H; Stenni, B

    2010-01-01

    Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3...

  12. NOAA Climate Data Record (CDR) of Leaf Area Index (LAI) and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains gridded daily Leaf Area Index (LAI) and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) derived from the NOAA Climate Data...

  13. Climate Driven Changes in the Formation Pathways of Atmospheric Sulfate: A Comparison from Bipolar Ice Core Records

    Science.gov (United States)

    Geng, L.; Alexander, B.

    2013-12-01

    Atmospheric sulfate aerosol affects radiative forcing of the atmosphere and thus climate. The formation pathways of sulfate, through gas-phase or aqueous phase oxidation of SO2, have implications for climate forcing because only sulfate produced in the gas-phase can nucleate new aerosol particles. Thus, constraining the formation pathways of sulfate in different climates is important to assess its climate impact. O-17 excess of sulfate (Δ17O(SO42-)) can be used to distinguish the formation pathways of atmospheric sulfate. Δ17O(SO42-) measured from an Antarctic (Vostok) ice core covering a full climate cycle suggested that gas-phase oxidation was more important in the last glacial period than that in the interglacial periods before and after, though its cause was not fully understood. We present new results of Δ17O(SO42-) measured from a Greenland (GISP2) ice core covering the last glacial period. Compared to the Vostok results, the GISP2 results display a similar Δ17O(SO42-) - temperature/climate relationship, but with much smaller Δ17O(SO42-) values in preindustrial Holocene (PIH). This difference seen in PIH is likely because aqueous-phase oxidation of SO2 by H2O2 is more important in the Northern Hemisphere than in the Southern Hemisphere, due to differences in cloud pH and oxidant abundances. Results from a new chemistry-climate model (ICECAP) suggest that the enhanced gas-phase oxidation in the glacial period in both hemispheres is due to 1) increased tropospheric OH production in mid- to high latitudes caused by enhanced UV-B radiation originating from reduced stratospheric ozone abundance and higher surface albedos over land and sea ice, and 2) reduced cloud fraction in the glacial climate. Implications for the global sulfur budget will be discussed.

  14. A high-resolution stalagmite O-C isotope record from Nan-jing and its rapid response to climatic events

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Here we discussed rapid response of the cave temperature and vegetation to the four Dansgaard-Oeschger cold and warm cycles during 50-40 kaBP based on results of oxygen and carbon stable isotopic compositions from a stalagmite in Tangshan, Nanjing. It is found that the amount of C3 vegetation relative to C4-type declines during the D-O warm events, indicating the decrease of the effective meteoric precipitation. Compared with O-isotope records of the Greenland ice core, the stalagmite record displays a very similar pattern to Greenland ice core record over the decade-century time scale, suggesting that the changes of the East Asian monsoon climate are in accordance with the high-latitude polar climate in the short-term time scale. The age of the ice-rafted H5 event in the stalagmite record, however, preceded that of Greenland ice cores by 2 ka. This out of phase between the remote areas cannot be yet proven because the two time scales were determined from different dating methods.``

  15. Estimating the regional climate signal in a late Pleistocene and early Holocene lake-sediment δ18O record from Vermont, USA.

    Science.gov (United States)

    Mandl, Maximilian Benedict; Shuman, Bryan Nolan; Marsicek, Jeremiah; Grigg, Laurie

    2016-07-01

    We present a new oxygen isotope (δ18O) record from carbonate-rich lake sediments from central Vermont. The record from Twin Ponds spans from 13.5 cal ka BP (1950 AD) to present, but contains a 6 ka long hiatus starting shortly after 7.5 cal ka BP. We compare the record for ca. 13.5-7.5 cal ka BP with published δ18O data from the region after using a Bayesian approach to produce many possible chronologies for each site. Principal component analysis then identified chronologically-robust, multi-site oxygen isotope signals, including negative values during the Younger Dryas, but no significant deviations from the early Holocene mean of the regional records. However, differences among sites indicate significant trends that likely relate to interacting changes in the regional gradients of seasonal temperatures and precipitation as well as moisture sources, moisture pathways, and aridity that were controlled by large-scale climatic controls such as insolation, the progressive decline of the Laurentide Ice Sheet, and changes in oceanic circulation. Centennial shifts punctuate these trends at ca. 9.3 and 8.2 cal ka BP, and reveal that the local character of these short-lived features requires a detailed understanding of lake hydrology and regional isotopic gradients to yield reliable information for regional climate reconstructions.

  16. Accumulation reconstruction and water isotope analysis for 1736-1997 of an ice core from the Ushkovsky volcano, Kamchatka, and their relationships to North Pacific climate records

    Science.gov (United States)

    Sato, T.; Shiraiwa, T.; Greve, R.; Seddik, H.; Edelmann, E.; Zwinger, T.

    2014-02-01

    An ice core was retrieved in June 1998 from the Gorshkov crater glacier at the top of the Ushkovsky volcano, in central Kamchatka. This ice core is one of only two recovered from Kamchatka so far, thus filling a gap in the regional instrumental climate network. Hydrogen isotope (δD) analyses and past accumulation reconstructions were conducted for the top 140.7 m of the core, spanning 1736-1997. Two accumulation reconstruction methods were developed and applied with the Salamatin and the Elmer/Ice firn-ice dynamics models, revealing a slightly increasing or nearly stable trend, respectively. Wavelet analysis shows that the ice core records have significant decadal and multi-decadal variabilities at different times. Around 1880 the multi-decadal variability of δD became lost and its average value increased by 6‰. The multi-decadal variability of reconstructed accumulation rates changed at around 1850. Reconstructed accumulation variations agree with ages of moraines in Kamchatka. Ice core signals were significantly correlated with North Pacific sea surface temperature (SST) and surface temperature (2 m temperature). δD correlates with the North Pacific Gyre Oscillation (NPGO) index after the climate regime shift in 1976/1977, but not before that. Therefore, our findings imply that the ice core record contains various information on the local, regional and large-scale climate variability in the North Pacific region. Understanding all detailed mechanisms behind the time-dependent connections between these climate patterns is challenging and requires further efforts towards multi-proxy analysis and climate modelling.

  17. Phytolith records of the climate change since the past 15000 years in the middle reach of the Yangtze River in China

    Institute of Scientific and Technical Information of China (English)

    Yansheng GU; Hanlin WANG; Xianyu HUANG; Hongxia PENG; Junhua HUANG

    2012-01-01

    Based on 14C dating and core sediments survey,phytolith records are employed to reconstruct paleovegetation and paleoclimate in the Jianghan Plain in the middle reach of the Yangtze River.Phytoliths identified are assigned into 21well-described morphotypes and divided into four groups (Poaceae,fern,coniferous and broad-leaved).The phytolith assemblages together with warmth index (Iw) are divided into 18 ecological zones,which reflect a complete vegetation history related to climate change in the middle reach of the Yangtze River during the past 15000 years.On the basis of the correlation ofphytolith records with the paleoclimatic indicators from stalagmite,peatland,North Atlantic deep-sea sediments,Loess Plateau of Central China,and Arabic Sea sediments,eight climatic phases are identified included Last Glacial Maximum (LGM) (20-14.8 cal kaBP),Last Deglaciation (LDG) (14.8-11.9cal kaBP),low-temperature phase in the Early Holocene (11.9-8 cal kaBP),Holocene Optimum (8-4.9cal kaBP),Holocene Katathermal (4.9-1.1cal kaBP),Medieval Warmth Period (MWP) (1.1-0.7 cal kaBP),Little Ice Age (LIA) (0.7-0.15 cal kaBP),and Modem Warming (0.15 cal kaBP-present).Climatic events such as Bolling-Allerod warm intervals,Older Dryas,Inter-Allerod Cold Period,and Younger Dryas,and eight Holocene Bond events (B1-8) have been identified since the LDG.Our results demonstrate that the evolution of the climate in the research area has a strong link with the Indian Summer Monsoon (SW Monsoon),Asian Summer Monsoon (SE Monsoon),and Holocene events in North Atlantic simultaneously,which might indicate that solar variability affects the Earth surface climate system at the centennial and millennial scales.

  18. Phytolith records of the climate change since the past 15000 years in the middle reach of the Yangtze River in China

    Science.gov (United States)

    Gu, Yansheng; Wang, Hanlin; Huang, Xianyu; Peng, Hongxia; Huang, Junhua

    2012-03-01

    Based on 14C dating and core sediments survey, phytolith records are employed to reconstruct paleovegetation and paleoclimate in the Jianghan Plain in the middle reach of the Yangtze River. Phytoliths identified are assigned into 21 well-described morphotypes and divided into four groups (Poaceae, fern, coniferous and broad-leaved). The phytolith assemblages together with warmth index ( I w) are divided into 18 ecological zones, which reflect a complete vegetation history related to climate change in the middle reach of the Yangtze River during the past 15000 years. On the basis of the correlation of phytolith records with the paleoclimatic indicators from stalagmite, peatland, North Atlantic deep-sea sediments, Loess Plateau of Central China, and Arabic Sea sediments, eight climatic phases are identified included Last Glacial Maximum (LGM) (20-14.8 cal kaBP), Last Deglaciation (LDG) (14.8-11.9 cal kaBP), low-temperature phase in the Early Holocene (11.9-8 cal kaBP), Holocene Optimum (8-4.9 cal kaBP), Holocene Katathermal (4.9-1.1 cal kaBP), Medieval Warmth Period (MWP) (1.1-0.7 cal kaBP), Little Ice Age (LIA) (0.7-0.15 cal kaBP), and Modern Warming (0.15 cal kaBP — present). Climatic events such as Bolling-Allerod warm intervals, Older Dryas, Inter-Allerod Cold Period, and Younger Dryas, and eight Holocene Bond events (B1-8) have been identified since the LDG. Our results demonstrate that the evolution of the climate in the research area has a strong link with the Indian Summer Monsoon (SW Monsoon), Asian Summer Monsoon (SE Monsoon), and Holocene events in North Atlantic simultaneously, which might indicate that solar variability affects the Earth surface climate system at the centennial and millennial scales.

  19. Climatic variability during the penultimate interglacial (MIS 7) and glacial (MIS 6) periods recorded in a speleothem from Kanaan cave, Lebanon (Central Levant)

    Science.gov (United States)

    Nehme, Carole; Verheyden, Sophie; Breitenbach, Sebastian F. M.; Gillikin, David P.; Verheyden, Anouk; Cheng, Hai; Edwards, Laurence; Hellstrom, John; Noble, Stephen R.; Farrant, Andrew R.; Sahy, Diana; Goovaerts, Thomas; Salem, Ghada; Claeys, Philippe

    2017-04-01

    Little is known about terrestrial climate dynamics of the Levant during the penultimate interglacial-glacial period. A well-dated stalagmite ( 194 to 154 ka) from Kanaan cave, located near the Mediterranean in Lebanon, is examined for its petrography, growth history, and stable isotope geochemistry to answer the climate instability pattern of the glacial MIS 6 and possible wet phases. A highly resolved continental climate record from the northern Levant has been recovered from this precisely U-Th-dated speleothem, spanning the late penultimate interglacial (equivalent of the MIS 7) to the mid-penultimate glacial period ( MIS 6). The stalagmite grew slowly and discontinuously with an unstable isotopic pattern from 194 and at least up to 178 ka. Subsequently, the stalagmite ceased growing from 169.5 to 163.1 ka (interpolated ages) with a hiatus of ca. 6.24 ka according to the model age. However, low δ 18O and δ 13C values indicate generally cold, but overall more humid climate compared to the last glacial (MIS 3). Higher growth rates during the mid-penultimate glacial period ( 163-154 ka) are most probably linked to increased water recharge in the vadose zone. A short More distinct layering in the upper section compared to the basal part of the stalagmite suggests stronger seasonality from 163 ka to 154 ka. Negative oxygen and carbon isotope excursions were found at ˜155.5 ka, ˜156 ka, between ˜159.6 and ˜160.1 ka and at ˜162.6 ka. The inferred Kanaan cave humid intervals during the mid-penultimate period follow variations of pollen records in the Eastern and Western Mediterranean basins and correlate well with the synthetic Greenland records and East Asian Summer Monsoon Interstadials, indicating short warm/wet periods similar to the D-O events during MIS 4-3 in the Eastern Mediterranean region.

  20. High-Resolution Late Holocene Climatic Records From Kucukcekmece Lagoon and Uludag Glacial, Yeniçaga, Bafa Lakes in Western Turkey: Some Preliminary Results

    Science.gov (United States)

    Akcer On, S.; Cagatay, M.; Sakinc, M.

    2010-12-01

    This study focuses on climatic and environmental sedimentary records of the last 4000 years in Kucukcekmece Lagoon (Istanbul), Uludag glacial (Bursa) , Yenicaga (Bolu) and Bafa (Mugla) Lakes in western Turkey. The water bodies are located on a N-S transect in western Turkey, and as such the’r records are important for assesment of Late Holocene eastern Mediterranean climatic changes. A total of 12 cores varying between 0.6 and 4.8 m are analyzed at 5mm resolution using Multi Sensor Core Logger (MSCL) having magnetic susceptibilty, P-Wave, density and resistivity sensors, XRF(X-Ray Fluoresance) core scanner multi element analysis at a 0.2 mm resolution. The cores are then sampled at 20, 50 and 100 mm intervals for different analyses. The samples are analyzed for total inorganic (TIC) and organic carbon (TOC). The ostracoda and benthic foraminifera shells in the sand size fraction of the sediment samples are identified under binocular microscope and suitable species are picked and analyzed for the stable oxygen and carbon isotope analysis. The cores are dated using AMS 14C analysis. The data from these lakes and lagoon are interpreted for environmental and climatic changes and compared with historical and other regional and global climate signals. The results indicate dry periods during 3300 -2500 ka BP and 867-1790 AD and1070-1690 AD with some brief intervening humid periods. Abrupt environmental change starting around1950 due to mainly human activities has also been clearly detected. These changes in the sedimentds are well correlated with the historical records.

  1. A ~600 kyr duration Early Pleistocene record from the West Turkana (Kenya) HSPDP drill site: elemental XRF variability to reconstruct climate change in Turkana Boy's backyard

    Science.gov (United States)

    Stockhecke, M.; Beck, C. C.; Brown, E. T.; Cohen, A.; Deino, A. L.; Feibel, C. S.; Sier, M.

    2015-12-01

    Outcrops in the Kenyan and Ethiopian rift valleys document repeated occurrences of freshwater lakes and wooded landscapes over the past 4 million years at locations that are currently seasonally-dry savanna. Studies of the rich fossil records, in combination with outcropping lacustrine sequences, led to major breakthroughs in our knowledge of driving factors in human evolution. However, study of continuous drill core from ancient lake basins provides a basis for to unravel East African climate dynamics in an unseen fashion. The Hominin Sites and Paleolakes Drilling Project (HSPDP), and the related Olorgesailie Drilling Project, recovered ~2 km of drill core since 2012. A major project goal is characterization of East African paleoclimate in order to evaluate its impact on hominin evolution. XRF core scanning data provide a means of evaluating records of past environmental conditions continuously and at high resolution. However, the HSPDP records contain complex lithologies reflecting repeated episodes of inundation and desiccation of the lake basins. Nevertheless, careful data evaluation based on detailed lithostratigraphy, which includes smear-slide microscopic analyses and X-radiographic images, allows disentanglement of complex signals and robust identification of continuous sequences for any cyclostratigraphic and statistical analysis. At the HSPDP Turkana Basin site a 175.6 m-long core the covers the Early Pleistocene time window during which hominids first expanded out of Africa and marine records document reorganization of tropical climate and the development of the strong Walker circulation. This drill site carries particular interest as it is located in only 2.5 km from the location of one of the most complete hominin skeletons ever recovered (Turkana Boy). Here we present a methodological approach to address the highly variable lithostratigraphy of the East African records to establish comprehensive and environmentally meaningful paleoclimate timeseries

  2. An absolutely dated high-resolution stalagmite record from Lianhua Cave in central China: Climate forcing and comparison with Wanxiang Cave and Dongge Cave records over the past 2000 years

    Science.gov (United States)

    Li, Hong-Chun; Yin, Jian-Jun; Shen, Chuan-Chou; Mii, Horng-Sheng; Li, Ting-Yong

    2015-04-01

    A 33-cm long aragonite stalagmite (LHD-1) from Lianhua Cave has been dated by MC-ICPMS 230Th/U method on 41 horizons. Very high U contents (1~6ppm) and low Th contents yield excellent 230Th/U dates which provide reliable chronology of the stalagmite on sub-decadal time scale over the past 3350 years. A total of 1716 samples have been measured for δ18O and δ13C, spanning annual resolution over the past 1820 years. The stalagmite δ18O is not only influenced by the 'amount effect', but also affected by the moisture source. Enhanced the tropical monsoon trough under strong EASM brings higher spring quarter rainfall with isotopically light monsoonal moisture in the cave site, resulting in lighter stalagmite δ18O. On decadal or longer time scales, increased solar activity produces warmer condition and stronger summer monsoon which lead to wet climates. On interannual-to-decadal scales, the Walker Circulation under El Niño conditions during cold periods will shift toward the central Pacific and result in weakening of EASM. Under such a circumstance, dry climates will be prevailed in the study area. Based on the δ18O and δ13C records, we have deciphered climatic and vegetation changes of the study area in decadal scales. The highly precise dated LHD-1 record has been compared with previous published Wanxiang Cave and Dongge Cave records. Although some similarities can be found, there are major discrepancies among the three well-dated records, especially during AD 500-700 and AD 1300-1600. In additional, the major weak monsoon periods defined in the Wanxiang Cave record during late Tang Dynasty, late Yuan Dynasty and late Ming Dynasty are not supported by the LHD-1 record. The heaviest δ18O peaks (more than five continuous heavy values) over the past 2000 years appeared around AD 1990-2003, 1657-1662, 1220-1228, 663-669, 363-370, and 1082-1090 (in the order of heavy to light). None of these periods occurred Chinese dynasty collapse.

  3. A 50,000 year insect record from Rancho La Brea, Southern California: Insights into past climate and fossil deposition

    Science.gov (United States)

    Holden, Anna R.; Southon, John R.; Will, Kipling; Kirby, Matthew E.; Aalbu, Rolf L.; Markey, Molly J.

    2017-07-01

    Rigorously studied and dated Late Quaternary paleoenvironmental reconstructions from Ranch La Brea (RLB) and the Los Angeles Basin are scarce. Here, we use data from AMS radiocarbon dated insect fragments to infer local climates over the past 50,000 years. Our results indicate: 1) Quaternary insect remains can be located with great accuracy in radiocarbon time, and 2) well-dated and documented climate indicator beetle species are sensitive proxies for environmental change in the Los Angeles Basin. A total of 182 extant RLB ground and darkling beetle species (Coleoptera: Carabidae, Tenebrionidae) were radiocarbon dated. The resulting radiocarbon dates form a semi-continuous range from ∼50 to 28, 16-7.5, and 4 kcal yrs BP to the present. Associated insect climate ranges indicate past conditions consistent with, or very similar to, the current Los Angeles Basin Mediterranean climate. Importantly, these insect data suggest higher temperatures and aridity than inferred previously from other RLB proxies. Furthermore, wider-than-assumed dating spreads for some deposits emphasize the lack of biostratigraphy for RLB, and challenge inferences based on limited sets of radiocarbon dates and assumptions about stratigraphic integrity. Our results demonstrate the necessity to independently radiocarbon date each taxon. The insect paleoclimate interpretations were compared to regional pollen data, primarily from various southern Californian sites including Lake Elsinore and Santa Barbara Basin. These comparisons reveal an important difference in climate interpretations for the last Glacial: the RLB insect data suggest climate similar to the current one, while the regional pollen data have been interpreted as indicating a climate wetter than present.

  4. High-resolution climate records from two stalagmites in Qixin Cave, southern Guizhou, and Heinrich events during the last glacial period

    Institute of Scientific and Technical Information of China (English)

    ZhangMeiliang; ChengHai; YuanDaoxian; LinYushi; QinJiaming; WangHuat; FengYumei; TuLingling; ZhangHuiling

    2004-01-01

    The time sequence of high-resolution paleoclimatic changes since the last glacial period--60,500 yr B.P.--has been reconstructed with high-precision TIMS-U series dates and analyses of the oxygen isotopes from Q4 and Q6 stalagmites of the Qixin Cave in southern Guizhou. Comparative analyses of δ18O curves from the GISP2' ice core and the two stalagmites shows that the depositional records of the Dansgaard-Oeschger cycle events 1-18 and Heinrich's events H1-H5 from the records of the two stalagmites reflect rapid climate changes over a short time scale since the last glacial stage, and indicates the precise boundary lines at which the cold events occurred. The study results have shown that the records of the cold and warm events from the two stalagmites since 60,500 yr B.P. are the reflection of the paleo-monsoon circulation. Changes are clearly affected by the climate oscillation of the North Atlantic Ocean, and indicate that they have a strong teleconnection with the paleoclimate changes that occurred in the North Polar region. The records of δ18O from the Q4 and Q6 stalagmites indicate that the δ18O values from 60,590 yr B.P. to 11,290 yr B.P. changed from a more negative (or lighter)drift to a heavier or positive drift trend in the last glacial period. The data reflect the weakening of the Asian summer monsoon and the climate which generally became drier and cooler.

  5. Asian aridification linked to the first step of the Eocene-Oligocene climate Transition (EOT in obliquity-dominated terrestrial records (Xining Basin, China

    Directory of Open Access Journals (Sweden)

    G. Q. Xiao

    2010-07-01

    Full Text Available Asian terrestrial records of the Eocene-Oligocene Transition (EOT are rare and, when available, often poorly constrained in time, even though they are crucial in understanding the atmospheric impact of this major step in Cenozoic climate deterioration. Here, we present a detailed cyclostratigraphic study of the continuous continental EOT succession deposited between ~35 to 33 Ma in the Xining Basin at the northeastern edge of Tibetan Plateau. Lithology supplemented with high-resolution magnetic susceptibility (MS, median grain size (MGS and color reflectance (a* records reveal a prominent ~3.4 m thick basic cyclicity of alternating playa gypsum and dry mudflat red mudstones of latest Eocene age. The magnetostratigraphic age model indicates that this cyclicity was most likely forced by the 41-kyr obliquity cycle driving oscillations of drier and wetter conditions in Asian interior climate from at least 1 million year before the EOT. In addition, our results suggest a duration of ~0.9 Myr for magnetochron C13r that is in accordance with radiometric dates from continental successions in Wyoming, USA, albeit somewhat shorter than in current time scales. Detailed comparison of the EOT interval in the Tashan section with marine records suggest that the most pronounced lithofacies change in the Xining Basin corresponds to the first of two widely recognized steps in oxygen isotopes across the EOT. This first step precedes the major and second step (i.e. the base of Oi-1 and has recently been reported to be mainly related to atmospheric cooling rather than ice volume growth. Coincidence with lithofacies changes in our Chinese record would suggest that the atmospheric impact of the first step was of global significance, while the major ice volume increase of the second step did not significantly affect Asian interior climate.

  6. Stomatal proxy record of CO2 concentrations during the Last Termination demonstrates dynamic climate behaviour and an important role for CO2.

    Science.gov (United States)

    Steinthorsdottir, Margret; Wohlfarth, Barbara; Kylander, Malin E.; Blaauw, Maarten; Reimer, Paula J.

    2013-04-01

    We present a new stomatal proxy-based record of CO2 concentrations spanning Greenland Interstadial 1 (Allerød pollen zone, GI-1a to 1c), Greenland Stadial 1 (Younger Dryas pollen zone, GS-1) and the first part of the Holocene (Preboreal pollen zone). The calibrated atmospheric CO2 concentrations are based on Betula nana (dwarf birch) leaves from a fossil lake sedimentary sequence in south-eastern Sweden. The stomatal proxy method relies on the inverse relationship between stomatal density on plant leaves and atmospheric CO2 concentrations to reconstruct variations in past CO2 concentrations. The record presented here demonstrates that the overall pattern of CO2 evolution during this period was dynamic, with significant abrupt fluctuations in CO2 concentration when the climate moved from interstadial to stadial state and vice versa. The cooling at the GI-1/GS-1 transition was preceded by an abrupt warming, and the warming at the GS-1/Holocene transition was preceded by an abrupt cooling. This scenario is in contrast to CO2 records reconstructed from air bubbles trapped in ice, which indicate a gradual increase in concentrations, but largely in alignment with previously published stomatal proxy-based CO2 records. A new loss-on-ignition chemical record (used here as a proxy for temperature), from the same locality, lends independent support to the CO2 record.

  7. Assessment of a modern pollen-climate calibration set for Arctic tundra and northern taiga biomes from Yakutia (eastern Siberia) and its applicability to a Holocene record

    Science.gov (United States)

    Klemm, Juliane; Herzschuh, Ulrike

    2013-04-01

    The Arctic is expected to respond stronger and earlier to future global warming than other regions world-wide. This region is of particular importance because, on the one hand, even humble climate oscillations can be amplified through complex terrestrial ecosystem reactions. On the other hand, Arctic changes may feedback globally via atmospheric and oceanic circulations or variation of greenhouse gas concentrations. Past variations need to be documented with high confidence to gain important insights in constraints and magnitude of predicted Arctic changes. Documentation beyond instrumental records uses long-term proxy information obtained by analyses of sedimentary archives such as pollen records of lacustrine sediment cores. Reliable climate reconstruction from the warming-sensitive Arctic region are hitherto lacking because a) modern pollen spectra were rarely collected from sedimentary origin, and b) because the obtained reconstructions were not rigorously evaluated. This investigation aims to establish, evaluate, and apply a modern pollen-climate data set from the transition zone between arctic tundra and light taiga in Arctic Siberia. Our study area is located in the Northern Siberian Lowlands of Yakutia. Lacustrine samples (n=96) were collected along four north-to-south transects, which cover the major vegetation types and span a broad temperature and precipitation gradient (TJuly: 7.5-18.8°C; Pann: 114-315mm). Redundancy analyses indicated the relationship between modern pollen signal and their corresponding vegetation types and climate. Performance of transfer functions for TJuly and Pann were validated and tested on spatial-autocorrelation effects. They were applied to the one lake pollen record, which covers the last 12,000 years and was retrieved in the Siberian Arctic. The validation of the calibration set resulted in root mean square errors of prediction of 1.67°C for TJuly and 40mm for Pann, which equal 14.8% (TJuly) and 19.9% (Pann) of the

  8. A 1700-year Record of Tropical Sea Surface Temperatures and High-altitude Andean Climate Derived from the Quelccaya Ice Cap, Peru (Invited)

    Science.gov (United States)

    Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.; Lin, P.

    2010-12-01

    Stable isotopic, aerosol, and physical stratigraphy provided by new ice-core records from the Quelccaya ice cap (5670 masl) in Peru provide annual time series of tropical climatic and environmental variations extending back to 315 AD. These records present an opportunity to extract new information about links between rising temperatures on Andean tropical glaciers and sea surface temperatures (SSTs) in El Niño-Southern Oscillation (ENSO) indicator regions and in the Intertropical Convergence Zone (ITCZ) in the eastern Pacific and western Atlantic Oceans. ENSO is a dominant force for tropical climate variability on interannual time scales. It is linked with the position of the ITCZ and the associated teleconnections affect the strength and direction of air masses and storm tracks, variations in convective activity that control flooding and drought, and modulation of tropical storm intensities. The Quelccaya ice core record may be considered as the “Rosetta Stone” for high resolution climate records extracted from tropical glaciers, relating stable isotopic variations with tropical SSTs and freezing level heights. The ice core histories from Quelccaya also provide the longer term context needed to assess the significance of the magnitude and rate of its current ice loss. The cores provide a detailed description of climate conditions in the tropical Andes during the "Little Ice Age" and "Medieval Climate Anomaly” periods. They show that the recent acceleration of ice retreat in this Andean region is not driven solely by precipitation changes and that over decadal and longer time scales stable isotopic ratios are not significantly correlated with precipitation. The well-documented accelerating ice loss on Quelccaya in the Andes, as well as that on Naimona’nyi in the Himalayas, on Kilimanjaro in eastern Africa, and on ice fields near Puncak Jaya, Papua, Indonesia point to an overarching, larger scale driver. The ongoing melting of these ice fields is consistent

  9. Influence of climatic teleconnections on the temporal isotopic variability as recorded in a firn core from the coastal Dronning Maud Land, East Antarctica

    Indian Academy of Sciences (India)

    Sushant S Naik; Meloth Thamban; A Rajakumar; Witty D’Souza; C M Laluraj; Arun Chaturvedi

    2010-02-01

    Ice and firn core studies provide one of the most valuable tools for understanding the past climate change. In order to evaluate the temporal isotopic variability recorded in ice and its relevance to environmental changes, stable isotopes of oxygen and hydrogen were studied in a firn core from coastal Dronning Maud Land, East Antarctica. The annual 18O profile of the core shows a close relation to the El Niño Southern Oscillation (ENSO) variability. The ENSO indices show significant correlation with the surface air temperatures and 18O values of this region during the austral summer season and support an additional influence related to the Southern Annular Mode (SAM). The correlation between the combined ENSO-SAM index and the summer 18O record seems to have been caused through an atmospheric mechanism. Snow accumulation in this region illustrates a decreasing trend with opposite relationships with 18O data and surface air temperature prior and subsequent to the year 1997. A reorganization of the local water cycle is further indicated by the deuterium excess data showing a shift around 1997, consistent with a change in evaporation conditions. The present study thus illustrates the utility of ice-core studies in the reconstruction of past climate change and suggests possible influence of climatic teleconnections on the snow accumulation rates and isotopic profiles of snow in the coastal regions of east Antarctica.

  10. Tree-ring δ18O in African mahogany (Entandrophragma utile) records regional precipitation and can be used for climate reconstructions

    Science.gov (United States)

    van der Sleen, Peter; Groenendijk, Peter; Zuidema, Pieter A.

    2015-04-01

    The availability of instrumental climate data in West and Central Africa is very restricted, both in space and time. This limits the understanding of the regional climate system and the monitoring of climate change and causes a need for proxies that allow the reconstruction of paleoclimatic variability. Here we show that oxygen isotope values (δ18O) in tree rings of Entandrophragma utile from North-western Cameroon correlate to precipitation on a regional to sub-continental scale (1930-2009). All found correlations were negative, following the proposed recording of the 'amount effect' by trees in the tropics. The capacity of E. utile to record the variability of regional precipitation is also confirmed by the significant correlation of tree-ring δ18O with river discharge data (1944-1983), outgoing longwave radiation (a proxy for cloud cover; 1974-2011) and sea surface salinity in the Gulf of Guinea (1950-2011). Furthermore, the high values in the δ18O chronology from 1970 onwards coincide with the Sahel drought period. Given that E. utile presents clear annual growth rings, has a wide-spread distribution in tropical Africa and is long lived (> 250 years), we argue that the analysis of oxygen isotopes in growth rings of this species is a promising tool for the study of paleoclimatic variability during the last centuries in West and Central Africa.

  11. High-frequency climatic oscillations recorded in a Holocene coral reef at Leizhou Peninsula, South China Sea

    Institute of Scientific and Technical Information of China (English)

    余克服; 刘东生; 沈承德; 赵建新; 陈特固; 钟晋梁; 赵焕庭; 宋朝景

    2002-01-01

    A detailed study of the Goniopora reef profile at Dengloujiao, Xuwen County, Leizhou Peninsula, the northern coast of the South China Sea suggests that a series of high-frequency, large-amplitude and abrupt cold events occurred during the Holocene Hypsithermal, an unusual phenomenon termed "Leizhou Events" in this paper. This period (corresponding to 14C age of 6.2-6.7 kaBP or calendar age of 6.7-7.2 kaBP), when the climatic conditions were ideal for coral reefs to develop, can be divided into at least nine stages. Each stage (or called a "climate optimum"), lasting about 20 to 50 a, was terminated by an abrupt cold nap and (or) a sea-level lowering event in winter, leading to widespread emergence and death of the Goniopora corals, and growth discontinuities on the coral surface. Such a cyclic process resulted in the creation of a >4m thick Goniopora reef flat. During this period, the crust subsided periodically but the sea level was rising.The reef profile provides valuable archives for the study of decadal-scale mid-Holocene climatic oscillations in the tropical area of South China. Our results provide new evidence for high-frequency climate instability in the Holocene Hypsithermal, and challenge the traditional understanding of Holocene climate.

  12. Millennial-scale climate change since the last glaciation recorded by grain sizes of loess deposits on the northeastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    Lü Lianqing; FANG Xiaomin; LU Huayu; HAN Yongxiang; YANG Shengli; LI Jijun; AN Zhisheng

    2004-01-01

    Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution loess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 104 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at ~36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43-36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.

  13. Miocene climate as recorded on slope carbonates : examples from Malta (Central Mediterranean) and Northeastern Australia (Marion Plateau, ODP LEG 194)

    Science.gov (United States)

    John, Cédric Michaël

    2003-08-01

    This study investigated the slope carbonates of two Miocene carbonate systems: the Maltese Islands (in the Central Mediterranean) and the Marion Plateau (Northeastern Australia, drilled during ODP Leg 194). The aim of the study was to trace the impact of the Miocene cooling steps (events Mi1-Mi6) in these carbonate systems, especially the Mi3 event, which took place around 13.6 Ma and deeply impacted the marine oxygen isotope record. This event also profoundly impacted oceanographic and climatic patterns, eventually leading to the establishment of the modern ice-house world. In particular, East Antarctica became ice covered at that period. The rational behind the present study was to investigate the impact that this event had on shallow water systems in order to complement the deep-sea record and hence acquire a more global perspective on Miocene climate change. The Maltese Islands were investigated for trends in bulk-rock carbon and oxygen isotopes, as well as bulk-rock mineralogy, clay minerals analysis and organic geochemisty. Results showed that the mid Miocene cooling event deeply impacted sedimentation at that location by changing sedimentation from carbonate to clay-rich sediments. Moreover, it was discovered that each phase of Antarctic glaciation, not just the major mid Miocene event, resulted in higher terrigenous input on Malta. Mass accumulation rates revealed that this was linked to increased runoff during periods when Antarctica was glaciated, and thus that the carbonate sediments were “diluted” by clay-rich sediments. The model subsequently developed to explain this implies feedback from Antarctic glaciations creating cold, dense air masses that push the ITCZ Northward, thus increasing precipitation on the North African subcontinent. Increased precipitation (or stronger African monsoon) accelerated continental weathering and runoff, thus bringing more terrigenous sediment to the paleo-location of the slope sediments of Malta. Spectral analysis of

  14. The recent record of climate on the range of the George River Caribou Herd, Northern Québec and Labrador, Canada

    Directory of Open Access Journals (Sweden)

    J.D. Jacobs

    1996-01-01

    Full Text Available Records from permanent meteorological stations in and around the range of the George River Caribou Herd have been analyzed for the 1950-1991 period in order to identify climatic factors potentially influencing the numbers, condition, and distribution of caribou. Winter conditions identified include a significant temperature decrease over the period and some years of extreme snowfall. Spatial variations in snow cover may be responsible for shifts in winter range. Indications are that summer climate has not varied significantly, but spring and summer conditions may not have been particularly favourable for plant productivity in the summer range of females and calves. Climatological observations more representative of the summer range are needed for a better understanding of ecological relationships there.

  15. Integrating the EMPD with an Alpine altitudinal training set to reconstruct climate variables in Holocene pollen records from high-altitude peat bogs

    Science.gov (United States)

    Furlanetto, Giulia; Badino, Federica; Brunetti, Michele; Champvillair, Elena; De Amicis, Mattia; Maggi, Valter; Pini, Roberta; Ravazzi, Cesare; Vallé, Francesca

    2016-04-01

    Temperatures and precipitation are the main environmental factors influencing vegetation and pollen production. Knowing the modern climate optima and tolerances of those plants represented in fossil assemblages and assuming that the relationships between plants and climate in the past are not dissimilar from the modern ones, fossil pollen records offer many descriptors to reconstruct past climate variables. The aim of our work is to investigate the potential of high-altitude pollen records from an Alpine peat bog (TBValter, close to the Ruitor Glacier, Western Italian Alps) for quantitative paleoclimate estimates. The idea behind is that high-altitude ecosystems are more sensitive to climate changes, especially to changes in July temperatures that severely affect the timberline ecotone. Meantime, we met with difficulties when considering the factors involved in pollen dispersal over a complex altitudinal mountain pattern, such as the Alps. We used the EMPD-European Modern Pollen Database (Davis et al., 2013) as modern training set to be compared with our high-altitude fossil site. The EMPD dataset is valuable in that it provides a large geographic coverage of main ecological and climate gradients (at sub-continental scale) but lacks in sampling of altitudinal gradients and high-altitude sites in the Alps. We therefore designed an independent altitudinal training set for the alpine valley hosting our fossil site. 27 sampling plots were selected along a 1700m-elevational transect. In a first step, each plot was provided with (i) 3 moss polsters collected following the guidelines provided by Cañellas-Boltà et al. (2009) and analyzed separately to account for differences in pollen deposition at small scale, (ii) morphometrical parameters obtained through a high-resolution DEM, and (iii) temperature and precipitation were estimated by means of weighted linear regression of the meteorological variable versus elevation, locally evaluated for each site (Brunetti et al

  16. 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...

  17. A biomass burning record from the Lingtai Loess Section during the last 370 ka and implication for climate and environment

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bin; SHEN Chengde; SUN Yanmin; YANG Ying; YI Weixi

    2006-01-01

    The history of natural fire and its relationship with climate and vegetation are revealed from the content of elemental carbon and associated pollen data and paleoclimatic substitutive indicators for the loess of Lingtai Section in the last 370 ka BP. The study indicates that intense episodes of vegetation fires occurred during the interim especially when the climate was changing from wet to drought. The average content of elemental carbon in the interglaciers is higher than that in the glaciers, which coincides with the biomass change locally (or globally). The content of elemental carbon increases in the stage around 130 ka BP, indicating that the vegetation and climate pattern have changed, which may contribute to the variation of CO2. As a whole, the content of elemental carbon increasing with the time reflects the increasing aridity trend to some degree. In addition, the occurrence of the maximum peak and the highest average content of elemental carbon in the Holocene reflects the occurrence of a rapid climate event in 5900 a BP and more frequent fires caused by anthropic activities.

  18. Fluvial sequences of the Maas: a 10 Ma record of neotectonics and climate change at various time-scales.

    NARCIS (Netherlands)

    Berg, van den M.W.

    1996-01-01

    Around 10 million years ago, the interplay of tectonics, climate and sea level changed markedly in the southern North Sea Basin. One of the results was the start of rapid progradation of the Rhine/Meuse delta. The sediments of this basin-filling complex have been preserved in a number of depocentres

  19. The evolution of Holocene coastal dunefields, Jutland, Denmark: A record of climate change over the past 5000 years

    DEFF Research Database (Denmark)

    Clemmensen, L. B.; Murray, A.; Heinemeier, Jan;

    2009-01-01

    in southwestern Sweden suggest that these periods of dunefield activity were initiated during wet/cool summers. Most likely these climatic situations were associated with a more frequent passage of cyclones across Denmark in the summer seasons (increased storminess) causing aeolian sand movement and dune...

  20. Southern high-latitude terrestrial climate change during the Palaeocene-Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)

    Science.gov (United States)

    Contreras, L.; Pross, J.; Bijl, P. K.; O'Hara, R. B.; Raine, J. I.; Sluijs, A.; Brinkhuis, H.

    2014-07-01

    Reconstructing the early Palaeogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Palaeogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Palaeocene to the early Eocene (60.7-54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Palaeocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Palaeocene (excluding the middle/late Palaeocene transition); (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians that transiently prevailed across the middle/late Palaeocene transition interval (~ 59.5 to ~ 59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Palaeocene-Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e. palms and cycads) across the middle/late Palaeocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the

  1. Southern high-latitude terrestrial climate change during the Paleocene-Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)

    Science.gov (United States)

    Contreras, L.; Pross, J.; Bijl, P. K.; O'Hara, R. B.; Raine, J. I.; Sluijs, A.; Brinkhuis, H.

    2014-01-01

    Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7-54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Paleocene-Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads) across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP

  2. Southern high-latitude terrestrial climate change during the Paleocene–Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau

    Directory of Open Access Journals (Sweden)

    L. Contreras

    2014-01-01

    Full Text Available Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7–54.2 Ma based on a sporomorph record from Ocean Drilling Program (ODP Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii cool-temperate forests dominated by southern beech (Nothofagus and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma; and (iii paratropical forests rich in ferns that were established during and in the wake of the Paleocene–Eocene Thermal Maximum (PETM. The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph

  3. Reconstruction of Pleistocene Paleo-Hydrology and Climate Variations in Western Asia as Recorded in Speleothems from West-Central Iran

    Science.gov (United States)

    Mehterian, S.; Pourmand, A.; Sharifi, A.; Lahijani, H. A. K.; Naderi, M.; Swart, P. K.

    2014-12-01

    Extending from the eastern Mediterranean Sea to the northwest Indian Ocean and modern Iran, West Asia represents one of the most climatically dynamic regions in the northern hemisphere. The regional climate of West Asia is governed by interactions between the mid-latitude Westerlies, the Siberian Anticyclone and the Indian Ocean Summer Monsoon. In recent years, sparse records of Pleistocene climate variability have emerged from cave deposits (speleothems) in East Asia, the Arabian Peninsula and eastern Mediterranean. However, there remains a large gap in our understanding of abrupt and long-term climate variability in this region. We present for the first time δ18O data from speleothem and water samples that were collected from two cave systems in west-central Iran at similar latitudes, 60km apart: Qaleh Kord Cave (QKC, 35°47'50"N, 48°51'25"E) and Kataleh Khor Cave (KKC, 35°50'09"N, 48°09'41"E). U-Th geochronometry in two stalagmites from QKC yielded ages that range from 73,000 to 118,000 years B.P. Likewise, two stalagmites dated from KKC yielded ages 214,000-260,000 years B.P. and 300,000-500,000 years B.P. The analysis of additional speleothems from these caves should help to establish a continuous half million year multi-proxy record of δ18O variations, trace metal composition (Mg/Ca, Sr/Ca), and radiogenic Sr isotopes in these cave systems. High-resolution δ18O analyses of QKC stalagmites show patterns of variation that can be attributed to Marine Isotope Stage (MIS) 5a and 5b. Since both these caves sit at relatively high elevations (QKC: 2,160 masl, KKC: 1,695 masl) far from major seas (1,100km from Mediterranean Sea, 1,500km from North Indian Ocean), this record potentially reflects the synoptic interactions between the Westerlies and the Siberian Anticyclone during this time interval, as opposed to direct variations caused by sea level fluctuations. Measurements of drip water composition and modern environmental parameters (temperature, relative

  4. Climate-driven changes in water level: a decadal scale multiproxy study recording the 8.2-ka event and ecosystem responses in Lake Sarup (Denmark)

    DEFF Research Database (Denmark)

    Hansen, Rikke Bjerring; Olsen, Jesper; Jeppesen, Erik

    2013-01-01

    A two-stage change in lake level during the 8.2-ka event was identified in Lake Sarup, Denmark (55A degrees N), using a multiproxy approach on precise radiocarbon wiggle-matched annually laminated sediments deposited 8740-8060 cal. yr BP. Changes in delta C-13 and delta O-18 indicated closed lake...... hydrology driven by precipitation. The isotopic, sedimentary and plant macrofossil records suggested that the lake level started to decrease around 8400 cal. yr BP, the decrease accelerating during 8350-8260 before an abrupt increase during 8260-8210. This pattern shows that the climate anomaly started...

  5. The Abrupt Climatic Changes During the Last Deglaciation: Direct Land-sea Correlation From a Marine Pollen Record off Southeastern United States

    Science.gov (United States)

    Desprat, S.; McManus, J. F.; Peteet, D.

    2007-12-01

    We present a new direct land-sea correlation covering the last deglaciation in order a) to provide a better documentation of the regional vegetation changes in southeastern North America and b) more particularly to assess the connection of the continental climatic changes to North Atlantic circulation rapid variability. It was achieved using coupled analyses of pollen and marine climatic proxies from core KNR140-GGC39 (Blake Outer Ridge) at very high time-resolution. Mg/Ca ratio, planktonic δ18O, mean "sortable silt" grain size (mean S¯S¯) were analyzed in order to get records of SST, salinity and bottom current strength at the core site (Evans et al., submitted to Paleoceanography). The abrupt climatic changes which characterize the last deglaciation, in particular the major cold oscillations Heinrich event 1 (H1) and Younger Dryas (YD), have been widely documented in the North Atlantic and adjacent continents. However, in the tropical and subtropical North Atlantic and southeastern United States, the climatic signature of these events appears quite different and somehow unclear. Our direct land-sea correlation shows three configurations: 1- H1 period: cold climatic conditions in southeastern US (high percentages of boreal and herbaceous taxa) but only extremely cold at around 17 ka, accumulation of salty water in the subtropics (high δ18OSW- IVC) and weak bottom current intensity at the site (low mean S¯S¯) 2- Bolling Alleröd interval: abrupt warming in southeastern US (decrease of boreal taxa in favour of Quercus) at the beginning, synchronous to northern export of the salty water previously accumulated and to an increase of the bottom current strength at the site 3- YD period: mild and wet conditions in southeastern US (expansion of Tsuga and Quercus), decrease of the bottom current strength at the site and accumulation of salty water in the subtropical regions but less than during H1.

  6. Missing rings in Pinus halepensis – the missing link to relate the tree-ring record to extreme climatic events

    Directory of Open Access Journals (Sweden)

    Klemen eNovak

    2016-05-01

    Full Text Available Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE. These conditions are associated with decreased growth of trees and their increased vulnerability to pests and diseases. The anatomy of tree rings is responsive to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, cambial cell division may occur throughout almost the entire year. Alternatively, cell division may stop during relatively cool and dry winters, only to resume in the same year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR, which can link tree-ring anatomy to the occurrence of extreme events. A dendrochronological network of Pinus halepensis, a widespread tree species in the Mediterranean basin, was used to determine the relationship of MR to ECE. The network consisted of 113 sites throughout its distribution range. Binomial logistic regression analysis of 2595 MR series determined that MR increased in frequency with increased cambial age. Spatial analysis indicated that the geographic areas of southeastern Spain and northern Algeria contained the greatest frequency of MR. Further regression analysis indicated that the relationship of MR to total monthly precipitation and mean temperature was non-linear. In this first determination of climatic influences on MR, the formation of MR was most strongly associated with the combination of monthly mean temperature above 10°C from previous October till current February and total precipitation below 50 mm from previous September till current May. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a

  7. Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

    DEFF Research Database (Denmark)

    Capron, E.; Landais, A.; Chappellaz, J.

    2010-01-01

    Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized...... a succession of abrupt events associated with long Greenland InterStadial phases (GIS) enabling us to highlight a sub-millennial scale climatic variability depicted by (i) short-lived and abrupt warming events preceding some GIS (precursor-type events) and (ii) abrupt warming events at the end of some GIS...... (rebound-type events). The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence...

  8. Climatic records in a firn core from an Alpine temperate glacier on Mt. Yulong, southeastern part of the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    He Yuanqing; Yao Tandong; Cheng Guodong; Yang Meixue

    2001-01-01

    @@ Mt. Yulong is the southernmost glacier-covered area in Eurasia, including China. There are 19 sub-tropical temperate glaciers on the mountain, controlled by the southwestern monsoon climate. In the summer of 1999,a firn core, 10.10 m long, extending down to glacier ice,was recovered in the accumulation area of the largest glacier, Baishui No. 1. Periodic variations of climatic signals above 7.8 m depth were apparent, and net accumulation off our years was identified by the annual oscillations of isotopic and ionic composition. The boundaries of annual accumulation were confirmed by higher values of electrical conductivity and pH, and by dirty refreezing ice layers at the levels of summer surfaces.

  9. Climate in continental interior Asia during the longest interglacial of the past 500 000 years: the new MIS 11 records from Lake Baikal, SE Siberia

    Directory of Open Access Journals (Sweden)

    A. A. Prokopenko

    2010-01-01

    Full Text Available A synthesis of paleoclimate responses from Lake Baikal during the MIS 11 interglacial is presented based on proxy records from two drill sites 245 km apart. BDP-99 is located in vicinity of the delta of the major Baikal tributary, whereas the BDP-96 site represents hemipelagic setting distant from riverine influence. The comparison of thicknesses of interglacial intervals in these contrasting depositional settings confirms the extended ca. 33-kyr duration of the MIS 11 interglacial. The new BDP-99 diatom biostratigraphic record matches that of the BDP-96-2 holostratotype and thus allows establishing establishes robust correlation between the records on the same orbitally-tuned timescale.

    The first detailed MIS 11 palynological record from the BDP-99 drill core indicates the dominance of boreal conifer (taiga forest vegetation in the Baikal region throughout the MIS 11 interglacial, since at least 424 ka till ca. 396 ka. The interval ca. 420–405 ka stands out as a "conifer optimum" with abundant Abies sibirica, indicative of climate significantly warmer and less continental than today. The closest Baikal analog to this type of vegetation in the history of the current Holocene interglacial is at ca. 9–7 ka. The warm conifer phase lasted for ca. 15 kyr during MIS 11 interrupted by two millennial-scale cooling episodes at ca. 411–410 and 405–404 ka. Reconstructed annual precipitation of 450–550 mm/yr during the MIS 11 interglacial is by ca. 100 mm higher than during the Holocene; regional climate was less continental with warmer mean temperatures both in summer and in winter.

    At both drill sites, the two-peak structure of the MIS 11 diatom abundance profiles reflects the orbital signature of precession in the interglacial paleoclimate record of continental Eurasia. MIS 11 interglacial was characterized by the sustained high level of primary production and accumulation of autochthonous organic matter at both study

  10. The record of Miocene climatic events in AND-2A drill core (Antarctica): Insights from provenance analyses of basement clasts

    Science.gov (United States)

    Sandroni, Sonia; Talarico, Franco M.

    2011-01-01

    This paper includes the results of a detailed quantitative provenance investigation on gravel-size clasts occurring within the late Early to Late Miocene sedimentary glacimarine section recovered for the first time by the AND-2A core in the SW sector of the Ross Sea (southern McMurdo Sound, Antarctica). This period of time is of crucial interest, as it includes two of the major Cenozoic events in the global climatic evolution: the mid-Miocene climatic optimum and the middle Miocene climate transition. Petrographical and mineral chemistry data on basement clasts allow to individuate two different diagnostic clast assemblages, which clearly suggest two specific sectors of southern Victoria Land as the most likely sources: the Mulock-Skelton glacier and the Koettlitz-Blue glacier regions. Distribution patterns reveal high fluctuations of the detritus source areas throughout the investigated core interval, variations which can be interpreted as the direct result of an evolving McMurdo Sound paleogeography during the late Early to Late Miocene. Consistently with sedimentological studies, gravel-fraction clast distribution patterns clearly testify that the Antarctic ice sheet experienced a dramatic contraction at ca. 17.35 ± 0.14 Ma (likely correlated to the onset of the climatic optimum), and in a gravel-fraction clasts show that the variations of paleoenvironmental drivers characterising this period were able to exert deep transformation of the Antarctic ice sheet and reveal the methodology to be a powerful tool for the reconstruction of paleo-glacial-flow direction and paleogeographic scenarios.

  11. Land-Sea relationships of climate-related records: example of the Holocene in the eastern Canadian Arctic and Greenland

    Science.gov (United States)

    de Vernal, Anne; Fréchette, Bianca; Hillaire-Marcel, Claude

    2017-04-01

    Anne de Vernal, Bianca Fréchette, Claude Hillaire-Marcel Important progresses have been made to reconstruct climate and ocean changes through time. However, there is often a hiatus between the land-based climate reconstructions and paleoceanographical data. The reconstructed parameters are not the same (e.g. surface air temperature vs. sea-surface temperature). Moreover, the spatial (local to regional) and temporal dimensions (seasonal, annual to multi-decadal) of proxy-data are often inconsistent, thus preventing direct correlation of time series and often leading to uncertainties in multi-site, multi-proxy compilations. Here, we address the issue of land-sea relationships in the eastern Canadian Arctic-Baffin Bay-Labrador Sea-western Greenland based on the examination of different climate-related information from marine cores (dinocysts) collected nearshore vs. offshore, ice cores (isotopes), fjord and lake data (pollen). The combined information tends to indicate that "climate" changes are not easily neither adequately captured by temperature and temperature shifts. However, the seasonal contrast of temperatures seems to be a key parameter. Whereas it is often attenuated offshore, it is generally easy to reconstruct nearshore, where water stratification is usually stronger. The confrontation of data also shows a relationship between ice core data and sea-ice cover and/or sea-surface salinity, suggesting that air-sea exchanges in basins surrounding ice sheets play a significant role with respect to their isotopic composition. On the whole, combined onshore-offshore data consistently suggest a two-step shift towards optimal summer and winter conditions the circum Baffin Bay and northern Labrador Sea at 7.5 and 6 ka BP. These delayed optimal conditions seem to result from ice-meltwater discharges maintaining low salinity conditions in marine surface waters and thus a strong seasonality.

  12. Interannual to decadal scale North Pacific climate dynamics during the last millennium from Eclipse Icefield (St. Elias Mountains) ice core stable isotope records

    Science.gov (United States)

    Kreutz, K. J.; Wake, C.; Yalcin, K.; Vogan, N.; Introne, D.; Fisher, D.; Osterberg, E.

    2006-12-01

    A 345 meter ice core recovered from the St. Elias Mountains, Yukon Territory, Canada during 2002 has been continuously analyzed for stable hydrogen isotopes (deltaD), and is used to interpret changes in the North Pacfic hydrologic cycle and climate variability over the past 1000 years. Given the high annual snow accumulation rate at the site (1.5 meters/year), the record is high resolution (subannual) and annually dated to 1450 AD, and dated with ice flow models prior to 1450 AD. Five-year averaged isotope data over the past millennium display a classic Little Ice Age (LIA)/Medieval Climate Anomaly (MCA) pattern; that is, lower isotope ratios during the LIA, and higher isotope ratios during the MCA. Using the simple isotope/temperature relationship typically applied to ice core data, the Eclipse record may indicate lower regional temperatures and enhanced temperature variability during the period 1250 to 1700 AD. However, isotope data from an ice core recovered near the summit of Mt. Logan is clearly related to different hydrologic regimes. Regardless of the scaling used on the Eclipse isotope data, a distinct drop in isotope ratio occurs just prior to 1200AD, and may correspond with changes observed in tropical coral records. We suggest that fundamental changes in teleconnection and/or ENSO/PDO dynamics between the high and low latitudes in the Pacific may be responsible for the 13th century event. Based on the 1000-year record at 5-year resolution, as well as annual isotope data for the past 550 years, the 20th century is not anomalous with respect to previous time periods.

  13. Interactions between climate and vegetation during the Lateglacial period as recorded by lake and mire sediment archives in Northern Italy and Southern Switzerland

    Science.gov (United States)

    Vescovi, Elisa; Ravazzi, Cesare; Arpenti, Enrico; Finsinger, Walter; Pini, Roberta; Valsecchi, Verushka; Wick, Lucia; Ammann, Brigitta; Tinner, Willy

    2007-06-01

    We reconstruct the vegetational history of the southern side of the Alps at 18,000-10,000 cal yr BP using previous and new AMS-dated stratigraphic records of pollen, stomata, and macrofossils. To address potential effects of climatic change on vegetation, we compare our results with independent paleoclimatic series (e.g. isotope and chironomid records from the Alps and the Alpine forelands). The period before 16,000 cal yr BP is documented only at the lowland sites. The previous studies used for comparison with our new Palughetto record, however, shows that Alpine deglaciation must have started before 18,000-17,500 cal yr BP south of the Alps and that deglaciated sites were colonized by open woods and shrublands ( Juniperus, tree Betula, Larix, Pinus cembra) at ca 17,500 cal yr BP. The vegetational history of a new site (Palughetto, 1040 m a.s.l.) is consistent with that of previous investigations in the study region. Our results show three conspicuous vegetational shifts delimited by statistically significant pollen zones, at ca 14,800-14,400, 13,300-12,800 and 11,600-11,200 cal yr BP. At sites situated above 1000 m a.s.l. (e.g. Palughetto, Pian di Gembro) forests expanded in alpine environments at ca 14,500 cal yr BP (onset of Bølling period, GI-1 in the Greenland ice record). At the same time, rather closed treeline communities of the lowlands were replaced by dense stands of Pinus sylvestris and Betula. These early forests and shrublands consisted of Larix, P. cembra, Juniperus, P. sylvestris, Pinus mugo, and Betula, and had become established at ca 16,000 cal yr BP, probably in response to a temperature increase. If combined with other records from the Southern Alps, our data suggest that treeline ascended by ca 800-1000 m in a few centuries at most, probably as a consequence of climatic warming at the beginning of the Bølling period. At 13,100-12,800 cal yr BP the onset of a long-lasting decline of P. sylvestris was accompanied by the expansion of Quercus

  14. Holocene vegetation and climate changes from a peat pollen record of the forest - steppe ecotone, Southwest of Patagonia (Argentina)

    Science.gov (United States)

    Mancini, María Virginia

    2009-07-01

    Pollen analysis from a peat-bog sequence located at 50° 24' S, 72° 42' W in the Subantarctic forest - Patagonian steppe ecotone gives information about vegetation and climate changes in Southwestern Patagonia since the glacier retreat. After 11 000 cal yr BP a change from grass steppe to open Nothofagus forest indicates that climatic conditions became rapidly warmer. Development of a closed Nothofagus forest between 5800 and 3200 cal yr BP is interpreted as precipitation increase. During the late Holocene colder climate conditions prevail in response to Neoglacial events. After ca 3000 cal yr BP Nothofagus forest became opener, and after 800 cal yr BP grass steppe expanded. Changes in the forest-steppe ecotone composition as well as the ecotone longitudinal shifts suggest changes in temperature and precipitation. Present-day mean annual precipitation between 300 and 400 mm is associated with grass steppe, and 500-600 mm with a greater forest representation. During the last century, low presence of forest in the area may be related to European settlement and repeated flooding caused by periodic advances of Perito Moreno glacier.

  15. Lake sediment records on climate change and human activities since the Holocene in Erhai catchment, Yunnan Province, China

    Institute of Scientific and Technical Information of China (English)

    SHEN Ji; YANG Liyuan; YANG Xiangdong; R. Matsumoto; TONG Guobang; ZHU Yuxin; ZHANG Zhenke; WANG Sumin

    2005-01-01

    According to high-resolution analyses on multi-proxy of sediment core from the Erhai Lake, Yunnan Province, the sequence of climatic and environmental change since the Holocene has been reconstructed based on accurate dating. The results show that climate had transited from cold-wet to warm-wet during ca. 12950-8399 aBP in this area, and the transition happened in ca. 10329 aBP. Due to the enhancing southwest Asian monsoon and increasing precipitation, the lake-level of the Erhai Lake began to rise after ca. 10329 a BP. Climate in the catchment was warm and wet during the mid-Holocene, and the warmest stage appeared in ca.8399-6371 a BP. The lake-level descended in the mid-Holocene because of the decrease of effective moisture in the basin. Human activities appeared in ca. 6371 a BP, and the initial manner mainly focused on deforestation. Up to ca. 2139 a BP, due to the amount of immigration into this area, the cultivation was developed widely, which was followed by mining (coal mine).

  16. Missing Rings in Pinus halepensis – The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events

    Science.gov (United States)

    Novak, Klemen; de Luis, Martin; Saz, Miguel A.; Longares, Luis A.; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille B. K.; Papadopoulos, Andreas; Smith, Kevin T.

    2016-01-01

    Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees

  17. Missing Rings in Pinus halepensis - The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events.

    Science.gov (United States)

    Novak, Klemen; de Luis, Martin; Saz, Miguel A; Longares, Luis A; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille B K; Papadopoulos, Andreas; Smith, Kevin T

    2016-01-01

    Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees

  18. Abrupt climate change of East Asian Monsoon at 130 kaBP inferred from a high resolution stalagmite δ18O record

    Institute of Scientific and Technical Information of China (English)

    JIANG Xiuyang; WANG Yongjin; KONG Xinggong; WU Jiangying; SHAO Xiaohua; XIA Zhifeng; CHENG Hai

    2005-01-01

    230Th ages and oxygen isotope data of a stalagmite from Shanbao Cave in Hubei Province characterize the East Asian Monsoon precipitation from 133 to127 ka. The decadal-scale high-resolution δ18O record reveals a detailed transitional process from the Penultimate Glaciation to the Last Interglaciation. As established with 230Th dates, the age of the Termination II is determined to be 129.5±1.0 kaBP, which supports the Northern Hemisphere insolation as the triggers for the ice-age cycles. In our δ18O record, the glacial/ interglacial fluctuation reaches about 4‰, almost the same level as in other Asian Monsoon cave stalagmite δ18O records. The transition of the glacial/interglacial period in our record can be recognized as four stepwise stages, among which, a rapid rise of monsoon precipitation follows the stage of "Termination II pause". The rapid rise is synchronous with the abrupt change of global methane concentration, which reflects that an increase in both Asian Monsoon precipitation and tropical wetland plays an important role in the global climate changes.

  19. Accumulation reconstruction and water isotope analysis for 1735–1997 of an ice core from the Ushkovsky volcano, Kamchatka, and their relationships to North Pacific climate records

    Directory of Open Access Journals (Sweden)

    T. Sato

    2013-04-01

    Full Text Available To investigate past climate change in the Northwest Pacific region, an ice core was retrieved in June 1998 from the Gorshkov crater glacier at the top of the Ushkovsky volcano, in central Kamchatka. Hydrogen isotope (δD analysis and past accumulation reconstructions were conducted to a depth of 140.7 m, dated to 1735. Two accumulation reconstruction methods were applied with the Salamatin and the Elmer/Ice ice flow models. Reconstructed accumulation rates and δD were significantly correlated with North Pacific surface temperature. This, and a significant correlation of δD with the North Pacific Gyre Oscillation (NPGO index implies that NPGO data is contained in this record. Wavelet analysis shows that the ice core records have significant multi-decadal power spectra up to the late 19th century. The multi-decadal periods of reconstructed accumulation rates change at around 1850 in the same way as do Northeast Pacific ice core and tree ring records. The loss of multi-decadal scale power spectra of δD and the 6‰ increase in its average value occurred around 1880. Thus the core record confirms that the periodicity of precipitation for the entire North Pacific changed between the end of the Little Ice Age through the present due to changes in conditions in the North Pacific Ocean.

  20. Differential proxy responses to late Allerød and early Younger Dryas climatic change recorded in varved sediments of the Trzechowskie palaeolake in Northern Poland

    Science.gov (United States)

    Słowiński, Michał; Zawiska, Izabela; Ott, Florian; Noryśkiewicz, Agnieszka M.; Plessen, Birgit; Apolinarska, Karina; Rzodkiewicz, Monika; Michczyńska, Danuta J.; Wulf, Sabine; Skubała, Piotr; Kordowski, Jarosław; Błaszkiewicz, Mirosław; Brauer, Achim

    2017-02-01

    High-resolution biological proxies (pollen, macrofossils, Cladocera and diatoms), geochemical data (μ-XRF element scans, TOC, C/N ratios, δ18Ocarb and δ13Corg values) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were applied to reconstruct lake system responses to rapid climatic and environmental changes of the Trzechowskie palaeolake (TRZ; Northern Poland) during the late Allerød - Younger Dryas (YD) transition. Palaeoecological and geochemical data at 5-15 years temporal resolution allowed tracing the dynamics of short-term shifts of the ecosystem triggered by abrupt climate change. The robust age control together with the high-resolution sampling allowed the detection of leads and lags between different proxies to the climate shift at the Allerød-Younger Dryas transition. Our results indicate (1) a water level decrease and an increase in wind activities during the late Allerød and the Allerød-YD transition, which caused intensified erosion in the catchment, (2) a two-decades delayed vegetation response in comparison to the lake depositional system. Comparison with the Lake Meerfelder Maar record revealed slightly different vegetation responses of the Trzechowskie palaeolake at the YD onset.

  1. Long-term, High Resolution Records of Rock Cracking, Weather and Climate from Mid-Latitude, Desert and Humid-Temperate Sites

    Science.gov (United States)

    Eppes, M. C.; Magi, B. I.

    2014-12-01

    The mechanical breakdown of rock by physical weathering represents a significant rate limiting step for erosion, sediment supply, chemical weathering, and atmospheric- and landscape- evolution across the globe. Yet, the primary drivers of physical weathering are poorly quantified. Recent work highlights the importance of solar-induced thermal stress as a key driver in physical weathering, particularly in mid-latitudes, but to date the role of climate in thermal stress cracking has not been extensively explored. Here we examine two long-term acoustic emission (AE) records of rock cracking in both a humid-temperate (North Carolina - 1 year of data ) and a semi-arid (New Mexico - 3 years of data) location. We use AE energy as a proxy for rock cracking. We compare on-site average ambient daily temperature for days in which cracking occurs to the average temperatures for those dates derived from climate records from the nearest weather stations. The range of temperatures for days on which cracking occurs is similar for both stations (-10 C to +30 C). The majority of cracking in both locations occurs on warm days (> 15 C). In the semi-arid climate, 73% of cracking occurs on hot days (> 20 C) while only 0.1% occurs on very cold days (-8 C to -3 C). In the humid-temperate climate, 21% of cracking occurs on hot days, while 17% occurs on cold days. When days during which cracking occurs are compared to climate averages, 81% (NC) and 51% (NM) of all cracking occurs on days with absolute temperature anomalies >1, regardless of the temperature. The proportion of cracking that occurs on anomalously hot or cold days rises to 92% and 77% when the data is normalized to account for uneven sampling of the days with extreme temperatures. We examine these results in the context of prior analyses of this dataset which indicates that the majority of cracking, even that occurring in freezing temperatures, is caused by thermal-stress processes. Here we attribute a majority of observed

  2. Holocene climate and anthropogenic impacts on two austrian alpine lakes: instrumental record based inference models and multi-proxy approach studies

    Science.gov (United States)

    Schmidt, R.; Kamenik, C.; Hetzel, M.; Kaiblinger, C.; Koinig, K. A.; Thompson, R.

    2003-04-01

    Sediment cores from two lakes (Oberer and Unterer Landschitzsee) within the same drainage area and located slightly above and below the present day timberline, on the southern slopes of the central Austrian Alps, have been investigated using a multi-proxy approach. Transfer functions were constructed for diatoms (special emphasis being given to Fragilaria) and chrysophyte stomatocysts. The functions have been used to infer mean July water temperatures and the date of spring mixing, as based on a training set of thermistor recordings made in 45 lakes over a two year period. Other climate-driven environmental parameters which were reconstructed by transfer function studies are alkalinity and pH. In addition basic geochemical measurements, mineral magnetism, and pollen analyses were carried out on the sediment sequences. The period subsequent to the Younger Dryas (about 12000 cal. BP) is characterized by high alkalinity and low water temperatures, which in the earliest sediment records, were probably affected by glacial meltwater. Low water temperatures continued until 8000 cal. BP., due to a series of cold and wet climate oscillations. A marked temperature increase of about 3^o C followed between 8000 and 7400 cal. BP., paralleled by an increase in alkalinity and pH. Subsequently to about 6000 cal. BP. there followed a long-term trend of increasing humidity climaxing, at about 3000 cal. BP, in a series of oscillations between colder (and probably wetter) periods and warmer phases. A decline in pH mirrors this long-term trend in increasing humidity. Lowered pH appears to have been affected by temperature decline and/or melt-water impact during the more extreme events. Alpine land-use at Unterer Landschitzsee started about 3500 cal. BP and intensified during the Keltic/Roman and Medieval periods; these phases of enhanced anthropogenic impact are found to be closely related to climatic ameliorations. Changes in geochemistry (e.g., C/N and Fe/Mn ratios) relate to a

  3. A loess-paleosol record of climate and glacial history over the past two glacial-interglacial cycles (~ 150 ka), southern Jackson Hole, Wyoming

    Science.gov (United States)

    Pierce, Kenneth L.; Muhs, Daniel R.; Fosberg, Maynard A.; Mahan, Shannon A.; Rosenbaum, Joseph G.; Licciardi, Joseph M.; Pavich, Milan J.

    Loess accumulated on a Bull Lake outwash terrace of Marine Oxygen Isotope Stage 6 (MIS 6) age in southern Jackson Hole, Wyoming. The 9 m section displays eight intervals of loess deposition (Loess 1 to Loess 8, oldest), each followed by soil development. Our age-depth model is constrained by thermoluminescence, meteoric 10Be accumulation in soils, and cosmogenic 10Be surface exposure ages. We use particle size, geochemical, mineral-magnetic, and clay mineralogical data to interpret loess sources and pedogenesis. Deposition of MIS 6 loess was followed by a tripartite soil/thin loess complex (Soils 8, 7, and 6) apparently reflecting the large climatic oscillations of MIS 5. Soil 8 (MIS 5e) shows the strongest development. Loess 5 accumulated during a glacial interval (~ 76-69 ka; MIS 4) followed by soil development under conditions wetter and probably colder than present. Deposition of thick Loess 3 (~ 43-51 ka, MIS 3) was followed by soil development comparable with that observed in Soil 1. Loess 1 (MIS 2) accumulated during the Pinedale glaciation and was followed by development of Soil 1 under a semiarid climate. This record of alternating loess deposition and soil development is compatible with the history of Yellowstone vegetation and the glacial flour record from the Sierra Nevada.

  4. Reconstructing climate processes driving variability in precipitation sources from mid to late Holocene speleothem δ18O records from the Southwest US

    Science.gov (United States)

    Wong, C. I.; Nusbaumer, J. M.; Banner, J.

    2015-12-01

    Independent co-variation of speleothem δ18O values and other moisture-sensitive speleothem proxies (e.g., growth rate, trace element concentrations) in recently published Holocene stalagmite records from Texas and New Mexico suggest a decoupling between precipitation amounts and precipitation sources over the southwest US. There is, however, limited understanding of the relation between precipitation sources and precipitation amounts and the climate processes governing variability in the region's precipitation sources. To address this, we use source water tags to track precipitation derived from Pacific and Atlantic Oceans during a simulation of modern (1975-2013) climate. We find distinct patterns in the spatial distribution of the fraction of Pacific-derived winter precipitation are associated with unique atmospheric states. High pressure ridging reflected by 500 hPa geopotential heights result in weaker zonal winds and stronger northerly winds over the western US. Under these conditions, Pacific-derived moisture propagates further to the east, and Atlantic-derived moisture is suppressed over southern US. Conversely, 500 hPa geopotential heights that are latitudinally streamline result in strong zonal winds across the entire US. Under these conditions, the fraction of West Pacific-derived precipitation is limited to higher latitudes, and the fraction of far East Pacific- and Atlantic-derived precipitation is enhanced across the Southwest and Southern US, respectively. Further analysis of this data set will assess the teleconnections that link the distinct atmospheric conditions over the US with the state of the ocean and atmosphere over the Pacific and Atlantic Oceans. The results will be applied to reconstructing variability in the climate dynamics governing moisture transport to the southwest US during the mid to late Holocene as reflected by speleothem δ18O records in the region.

  5. Northern Mediterranean climate since the Middle Pleistocene: a 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)

    Science.gov (United States)

    Lacey, Jack H.; Leng, Melanie J.; Francke, Alexander; Sloane, Hilary J.; Milodowski, Antoni; Vogel, Hendrik; Baumgarten, Henrike; Zanchetta, Giovanni; Wagner, Bernd

    2016-03-01

    Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, millennial timescales. We also measured isotope ratios from authigenic siderite (δ18Os and δ13Cs) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ18O of lake water (δ18Olw) over the last 637 ka. Interglacials have higher δ18Olw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid.

  6. 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

    Holocene climatic, vegetational and environmental changes on the Ammassalik Island in SE Greenland (65.5 N and 37.5 W) have been studied in lake sediments and soil profiles. Based on the stratigraphy of sediments, geobiochemical characteristics, pollen and other biological proxies, a history....... Generally decreasing insolation, a still colder landscape and near coastal sea, potentially further cooled by the negative albedo feedback from snow and ice, generally increase a gradient driven circulation of heat and moisture northwards in the western part of the North Atlantic. Counteracting...

  7. Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high-resolution record unravels the dual influence of ENSO and ITCZ

    Science.gov (United States)

    Muñoz, Paula; Gorin, Georges; Parra, Norberto; Velásquez, Cesar; Lemus, Diego; Monsalve-M., Carlos; Jojoa, Marcela

    2017-01-01

    The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and abiotic (microfluorescence-X or μXRF) components of this high mountain ecosystem. The pollen record provides a proxy for temperature and humidity with a resolution of 20-35 yr, and μXRF of Ti and Fe is a proxy for rainfall with a sub-annual (ca. 6-month) resolution. Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5 °C lower than today) and wet Younger Dryas to a warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 °C below to 3.5° above present-day temperature. Warm periods (11,410-10,700, 9700-6900, 4000-2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. Spectral analysis of μXRF data show rainfall cyclicity at millennial scale throughout the Holocene, and at centennial down to ENSO scale in more specific time intervals. The highest rainfall intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret ENSO and ITCZ as the main climate change-driving mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was Pacific-driven (ENSO-dominated) during the YD and early Holocene, whereas it was Atlantic

  8. Variability in terrigenous sediment supply offshore of the Rio de la Plata (Uruguay recording the continental climatic history over the past 1200 years

    Directory of Open Access Journals (Sweden)

    L. Perez

    2015-04-01

    Full Text Available The continental shelf adjacent to the Río de la Plata (RdlP exhibits extremely complex hydrographic and ecological characteristics which are of great socio-economic importance. Since the long-term environmental variations related to the atmospheric (wind fields, hydrologic (freshwater plume, and oceanographic (currents and fronts regimes are little known, the aim of this study is to reconstruct the changes in the terrigenous input into the inner continental shelf during the Late Holocene period (associated with the RdlP sediment discharge and to unravel the climatic forcing mechanisms behind them. To achieve this, we retrieved a 10 m long sediment core from the RdlP mud depocenter at a depth of 57 m (GeoB 13813-4. The radiocarbon age control indicated an extremely high sedimentation rate of 0.8 cm per year, encompassing the past 1200 years (750–2000 AD. We used element ratios (Ti / Ca, Fe / Ca, Ti / Al, Fe / K as regional proxies for the fluvial input signal, and the variations in relative abundance of salinity-indicative diatom groups (freshwater vs. marine-brackish to assess the variability in terrigenous water and sediment discharge. Ti / Ca, Fe / Ca, Ti / Al, Fe / K and the freshwater diatom group showed the lowest values between 850 and 1300 AD, while the highest values occurred between 1300 and 1850 AD. The variations in the sedimentary record can be attributed to such regional and global climatic episodes as the Medieval Climatic Anomaly (MCA and the Little Ice Age (LIA, both of which had a significant impact on rainfall and wind patterns over the region. During the MCA, a northward migration of the Intertropical Confluence Zone (ITCZ could explain the lowest element ratios (indicative of a lower terrigenous input and a marine-dominated diatom record, both indicative of a reduced RdlP freshwater plume. In contrast during the LIA, the southward migration of the ITCZ accompanied by El Niño-like state conditions may have led to an

  9. High-amplitude, centennial-scale climate oscillations during the last glacial in the western Third Pole as recorded in the Guliya ice cap

    Science.gov (United States)

    Thompson, L. G.; Yao, T.; Mosley-Thompson, E.; Wu, G.; Davis, M. E.; Tian, L.; Lin, P. N.

    2015-12-01

    The Guliya ice cap, located in the Kunlun Mountains in the western Third Pole (TP) region near the northern limit of the southwest monsoon influence, may be the only non-polar ice field that provides detailed histories of climate and environment over the last glacial cycle. A continuous climate record from an ice core drilled in 1992 contains Eemian ice, and basal temperatures measured that year confirmed that the record was not being removed from the bottom. The δ18O record throughout Marine Isotope Stage 2 (MIS2) displays the occurrence of high-amplitude (~20‰) episodes of ~200-year periodicity, and the aerosol records suggest snow cover, regional vegetation and fire frequency that vary in synchrony. These oscillations might reflect the movement of the northernmost penetration of the monsoon precipitation through the Late Glacial Stage, which is restricted by the topographic barrier posed by the Kunlun range, and might also reflect solar-driven nonlinearities in the climate system such as sudden shifts in the jet stream. Recent model simulations suggest that glacial cooling over China was significantly amplified by stationary waves, and the Guliya MIS2 oscillations could reflect cyclical variability in these waves. These results are supported by clumped isotope thermometry of carbonates from the Chinese Loess Plateau, which indicate a 6 to 7oC decrease in Last Glacial Maximum summer temperatures. These studies will lead to a better understanding of the mechanisms driving such high-frequency, high-amplitude oscillations. A review of the 2015 Sino-American cooperative ice core drilling program on Guliya is presented. This program will serve as a flagship for the TP Environment Program, an international, multidisciplinary collaboration among professionals and students in 14 countries designed to investigate environmental changes across the TP. The rapidly warming TP contains ~46,000 glaciers that collectively hold one of Earth's largest stores of fresh water that

  10. Variability in terrigenous sediment supply offshore of the Rio de la Plata (Uruguay) recording the continental climatic history over the past 1200 years

    Science.gov (United States)

    Perez, L.; García-Rodríguez, F.; Hanebuth, T. J. J.

    2015-04-01

    The continental shelf adjacent to the Río de la Plata (RdlP) exhibits extremely complex hydrographic and ecological characteristics which are of great socio-economic importance. Since the long-term environmental variations related to the atmospheric (wind fields), hydrologic (freshwater plume), and oceanographic (currents and fronts) regimes are little known, the aim of this study is to reconstruct the changes in the terrigenous input into the inner continental shelf during the Late Holocene period (associated with the RdlP sediment discharge) and to unravel the climatic forcing mechanisms behind them. To achieve this, we retrieved a 10 m long sediment core from the RdlP mud depocenter at a depth of 57 m (GeoB 13813-4). The radiocarbon age control indicated an extremely high sedimentation rate of 0.8 cm per year, encompassing the past 1200 years (750-2000 AD). We used element ratios (Ti / Ca, Fe / Ca, Ti / Al, Fe / K) as regional proxies for the fluvial input signal, and the variations in relative abundance of salinity-indicative diatom groups (freshwater vs. marine-brackish) to assess the variability in terrigenous water and sediment discharge. Ti / Ca, Fe / Ca, Ti / Al, Fe / K and the freshwater diatom group showed the lowest values between 850 and 1300 AD, while the highest values occurred between 1300 and 1850 AD. The variations in the sedimentary record can be attributed to such regional and global climatic episodes as the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA), both of which had a significant impact on rainfall and wind patterns over the region. During the MCA, a northward migration of the Intertropical Confluence Zone (ITCZ) could explain the lowest element ratios (indicative of a lower terrigenous input) and a marine-dominated diatom record, both indicative of a reduced RdlP freshwater plume. In contrast during the LIA, the southward migration of the ITCZ accompanied by El Niño-like state conditions may have led to an expansion of

  11. Pollen-recorded climate changes between 13.0 and 7.0 14C ka BP in southern Ningxia, China

    Institute of Scientific and Technical Information of China (English)

    SUN AiZhi; MA YuZhen; FENG ZhaoDong; LI Fei; WU HuiNing

    2007-01-01

    A pollen record from Haiyuan section in the southern part of Ningxia revealed a detailed history of vegetation variation and associated climate changes during the period from ~13.0 to ~7.0 14C ka BP. A steppe landscape under a moderately dry (and probably cool) condition (~12.7-~12.1 14C ka BP) was replaced by a coniferous forest dominating the landscape under a generally wet climate from ~12.1 to ~11.0 14C ka BP. This generally wet period, corresponding to the European B(o)lling/All(e)rod period, can be divided into three stages: a cool and wet stage between ~12.1 and ~11.4 14C ka BP, a mild and relatively dry stage between ~11.4 and ~11.2 14C ka BP, and a mild and wet stage between ~11.2 and ~11.0 14C ka BP. The coniferous forest-dominated landscape was then deteriorated into steppe landscape (~11.0-~10.6 14C ka BP) and further into a desert steppe landscape from ~10.6 to ~9.8 14C ka BP, being correspondent to the European Younger Dryas period. After a brief episode of a cool and wet climate (~9.8-~9.6 14C ka BP), a relatively mild and dry condition prevailed during the early Holocene (~9.6-~7.6 14C ka BP) and then a warm and humid climate started the mid-Holocene (~7.6-~7.2 14C ka BP).

  12. A 16 ka climate record deduced from δ13C and C/N ratio in Qinghai Lake sediments, northeastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-patterned climatic change since 16 ka BP.Results show that Qinghai Lake underwent six environmental stages. From 16.2 to 14.3 ka BP and from 4.0 to 2.1 ka BP, the organic δ13C value was controlled by the concentration of atmospheric CO2. Relative higher organic δ13C values occurred between 14.3 to 10.4 ka BP indicative of water hardness decrease resulted from melting ice water, corresponding to two intervals of C/N peak values to the Bo1ing and Allerod warm periods in Europe respectively. From 10.4 ka BP, Qinghai Lake entered the Holocene and the climate was warm and a little dry. The Megathermal appeared at about 6.7 ka BP when the vegetation around the lake transformed into a forest. Between 6.3 ka BP and 4.0 ka BP, the temperature decreased and δ13C value was controlled by the expansion of C3 plants and the retreat of C4 plants in river catchment.Since 4.0 ka BP, the climate gradually became cold and dry. From 2.1 ka BP, the cold-dry climate and human activity resulted in an abrupt increase in C/N with deceased δ13C value; meanwhile, many coarse grains appeared in sediments.

  13. Record of environmental and climatic changes in middle Pleistocene sediments from Łuków (eastern Poland on the basis of plant macroremains analysis

    Directory of Open Access Journals (Sweden)

    Stachowicz-Rybka Renata

    2015-06-01

    Full Text Available Lacustrine sediments at the Łuków site bear a record of the Ferdynandovian interglacial, correlated with Marine Isotope Stage (MIS 13-15, including two warm periods of interglacial rank (climatostratigraphic units Ferdynandovian 1 and 2 separated by cooling/glaciation (Ferdynandovian 1/2. On the basis of plant macroremains analysis, the type of local vegetation in the lake and its surroundings as well as changes in climate, trophic conditions and water level were reconstructed in detail. Ferdynandovian 1 was a time of development of tall sedge swamps. The presence of Najas marina and N. minor also suggests high levels of eutrophication, particularly in the younger part of the climatic optimum. The occurrence of Zannichellia palustris indicates habitats of variable water level and high salt content. In the terminocratic phase of Ferdynandovian 1, the communities showed the reoccurrence of Betula nana, B. humilis and Larix sp., the disappearance of thermophilous trees, and the intensification of succession processes linked to climate cooling. In the cool Ferdynandovian 1/2, Betula nana and Cenococcum geophilum increased their frequencies, most likely due to enhanced supply of mineral matter to the basin. During Ferdynandovian 2, the next climate warming of interglacial rank, communities of aquatic vegetation with the highest share of thermophilous taxa included the extinct Aldrowanda borysthenica, Brasenia borysthenica, and Scirpus atroviroides, as well as Cyperus glomeratus, a species not presently found in the flora of Poland. Another cooling in the Sanian 2 (Elsterian 2 glaciation is indicated by the development of peat communities, with numerous Carex sp., Menyanthes trifoliata, Eriophorum vaginatum, and Andromeda polifolia, accompanied by the extinct Carex paucifloroides, Caulinia macrosperma, and Potamogeton praemaackianus.

  14. Hydroclimatic shifts recorded in peat archive from Rąbień mire (Central Poland) - better understanding of past climate changes using multidisciplinary approach

    Science.gov (United States)

    Słowiński, Michał; Marcisz, Katarzyna; Płóciennik, Mateusz; Obremska, Milena; Pawłowski, Dominik; Okupny, Daniel; Słowińska, Sandra; Borówka, Ryszard; Kittel, Piotr; Forysiak, Jacek; Michczyńska, Danuta J.; Lamentowicz, Mariusz

    2016-04-01

    Hydrological changes are main drivers of the processes occurring in the peatland ecosystem, e.g. organic matter accumulation and decomposition. Hydroclimatic changes in mires are caused by various non-climatic factors, such as hydroseral succession or land use changes. Central Europe, namely Poland, is characterized by a transitional climate with influence o both continental and Atlantic air masses, which makes a this region a very sensitive to climate change. Here we explore a potential of multidisciplinary approach in reconstruction of past climate change and particularly hydroclimatic conditions which control in Sphagnum peatland ecosystem. We reconstructed 3300 years (between 3,500 BC and 200 BC) history of development of Rąbień mire using several biotic proxies (pollen, plant macrofossils, testate amoebae, Cladocera, Chironomidae) and geochemistry. Study site - Rąbień mire (area 42 ha) is located in central Poland and it is protected nature reserve. The origin of the mire depression is connected with the development of the thermokarst basin isolated by dunes. Rąbień mire is limnogenic, i.e. formed by the process of terrestrialisation of a water body and thickness of biogenic deposits is 6.2 m (440 cm of lacustrine sediment and 180 cm of peat). Our results demonstrate the high potential of Rąbień peat record for reconstructing the palaeohydrological dynamics. The studied time interval is characterized by two pronounced dry periods: ~2,500 to ~1,700 cal. BC and ~800 to ~600 cal. BC, and two periods of significant increases in water table: ~1,100 to ~800 cal. BC and ~600 to ~250 cal. BC. The timing of the wet shift at 600 cal. BC corresponds to wet periods in different sites from Central and Eastern Europe. Our investigation reveals a complex pattern of proxies, what might be linked to the past atmospheric circulation patterns. Extreme hydroclimatic conditions most possibly had a direct impact on the functioning of peatland ecosystems. What has been

  15. 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 la...

  16. Reconstruction of Antarctic climate change using ice core proxy records from the coastal Dronning Maud Land, East Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Thamban, M.; Laluraj, C.M.; Naik, S.S.; Chaturvedi, A.

    , possibly through atmospheric scavenging. The nitrate (NO sub (3) –) profile exhibit significant temporal shifts than that of the sulphate (SO sub (4) sup (2)–), with a major shift around 1750 AD. The changes in NO sub (3) – record are synchronous...

  17. Orbital forcing of climate over South Africa: A 200,000-year rainfall record from the Pretoria saltpan

    CSIR Research Space (South Africa)

    Patridge, TC

    1997-01-01

    Full Text Available Late Pleistocene variations in rainfall in subtropical Southern Africa are estimated from sediments preserved in the Pretoria saltpan, a 200,000 year-old closed-basin crater lake on the interior plateau of South Africa. This record is one of the few...

  18. Orbital forcing and climate response : astronomically-tuned age models and stable isotope records for the Oligocene-Miocene

    NARCIS (Netherlands)

    Beddow-Twigg, H.M.

    2016-01-01

    The primary aim of this thesis is to reconstruct the evolution of the cryosphere, global ocean temperatures and the carbon cycle during the Oligocene-Miocene interval; using high-resolution foraminiferal stable isotope records with accurate chronological control provided by astronomically tuned age

  19. Spatial and temporal oxygen isotope variability in northern Greenland - implications for a new climate record over the past millennium

    Science.gov (United States)

    Weißbach, S.; Wegner, A.; Opel, T.; Oerter, H.; Vinther, B. M.; Kipfstuhl, S.

    2016-02-01

    We present for the first time all 12 δ18O records obtained from ice cores drilled in the framework of the North Greenland Traverse (NGT) between 1993 and 1995 in northern Greenland. The cores cover an area of 680 km × 317 km, 10 % of the Greenland ice sheet. Depending on core length (100-175 m) and accumulation rate (90-200 kg m-2 a-1) the single records reflect an isotope-temperature history over the last 500-1100 years. Lowest δ18O mean values occur north of the summit and east of the main divide as a consequence of Greenland's topography. In general, ice cores drilled on the main ice divide show different results than those drilled east of the main ice divide that might be influenced by secondary regional moisture sources. A stack of all NGT records and the NGRIP record is presented with improved signal-to-noise ratio. Compared to single records, this stack represents the mean δ18O signal for