WorldWideScience

Sample records for antarctic climate signature

  1. The Signature of Southern Hemisphere Atmospheric Circulation Patterns in Antarctic Precipitation

    Science.gov (United States)

    Marshall, Gareth J.; Thompson, David W. J.; van den Broeke, Michiel R.

    2017-11-01

    We provide the first comprehensive analysis of the relationships between large-scale patterns of Southern Hemisphere climate variability and the detailed structure of Antarctic precipitation. We examine linkages between the high spatial resolution precipitation from a regional atmospheric model and four patterns of large-scale Southern Hemisphere climate variability: the southern baroclinic annular mode, the southern annular mode, and the two Pacific-South American teleconnection patterns. Variations in all four patterns influence the spatial configuration of precipitation over Antarctica, consistent with their signatures in high-latitude meridional moisture fluxes. They impact not only the mean but also the incidence of extreme precipitation events. Current coupled-climate models are able to reproduce all four patterns of atmospheric variability but struggle to correctly replicate their regional impacts on Antarctic climate. Thus, linking these patterns directly to Antarctic precipitation variability may allow a better estimate of future changes in precipitation than using model output alone.

  2. Genetic signature of Last Glacial Maximum regional refugia in a circum-Antarctic sea spider

    Science.gov (United States)

    Soler-Membrives, Anna; Linse, Katrin; Miller, Karen J.; Arango, Claudia P.

    2017-10-01

    The evolutionary history of Antarctic organisms is becoming increasingly important to understand and manage population trajectories under rapid environmental change. The Antarctic sea spider Nymphon australe, with an apparently large population size compared with other sea spider species, is an ideal target to look for molecular signatures of past climatic events. We analysed mitochondrial DNA of specimens collected from the Antarctic continent and two Antarctic islands (AI) to infer past population processes and understand current genetic structure. Demographic history analyses suggest populations survived in refugia during the Last Glacial Maximum. The high genetic diversity found in the Antarctic Peninsula and East Antarctic (EA) seems related to multiple demographic contraction-expansion events associated with deep-sea refugia, while the low genetic diversity in the Weddell Sea points to a more recent expansion from a shelf refugium. We suggest the genetic structure of N. australe from AI reflects recent colonization from the continent. At a local level, EA populations reveal generally low genetic differentiation, geographically and bathymetrically, suggesting limited restrictions to dispersal. Results highlight regional differences in demographic histories and how these relate to the variation in intensity of glaciation-deglaciation events around Antarctica, critical for the study of local evolutionary processes. These are valuable data for understanding the remarkable success of Antarctic pycnogonids, and how environmental changes have shaped the evolution and diversification of Southern Ocean benthic biodiversity.

  3. Antarctic snow and global climate

    International Nuclear Information System (INIS)

    Granberg, H.B.

    2001-01-01

    Global circulation models (GCM) indicate that global warming will be most pronounced at polar regions and high latitudes, causing concern about the stability of the Antarctic ice cap. A project entitled the Seasonal Snow in Antarctica examined the properties of the near surface snow to determine the current conditions that influence snow cover development. The goal was to assess the response of the snow cover in Queen Maud Land (QML) to an increased atmospheric carbon dioxide content. The Antarctic snow cover in QML was examined as part of the FINNARP expeditions in 1999 and 2000 which examined the processes that influence the snow cover. Its energy and mass balance were also assessed by examining the near surface snow strata in shallow (1-2 m) pits and by taking measurements of environmental variables. This made it possible to determine if the glacier is in danger of melting at this northerly location in the Antarctic. The study also made it possible to determine which variables need to change and by how much, for significant melting to occur. It was shown that the Antarctic anticyclone creates particular conditions that protect the snow cover from melting. The anticyclone brings dry air from the stratosphere during most of the year and is exempt from the water vapour feedback. It was concluded that even a doubling of atmospheric carbon dioxide will not produce major snow melt runoff. 8 refs

  4. Antarctic climate change and the environment

    Science.gov (United States)

    2009-11-01

    This volume provides a comprehensive, up-to-date account of how the physical and biological : environment of the Antarctic continent and Southern Ocean has changed from Deep Time until : the present day. It also considers how the Antarctic environmen...

  5. Arctic and Antarctic Oscillation signatures in tropical coral proxies over the South China Sea

    Directory of Open Access Journals (Sweden)

    D.-Y. Gong

    2009-05-01

    Full Text Available Arctic Oscillation (AO and Antarctic Oscillation (AAO are the leading modes of atmospheric circulation in mid-high latitudes. Previous studies have revealed that the climatic influences of the two modes are dominant in extra-tropical regions. This study finds that AO and AAO signals are also well recorded in coral proxies in the tropical South China Sea. There are significant interannual signals of AO and AAO in the strontium (Sr content, which represents the sea surface temperature (SST. Among all the seasons, the most significant correlation occurs during winter in both hemispheres: the strongest AO-Sr and AAO-Sr coral correlations occur in January and August, respectively. This study also determined that the Sr content lags behind AO and AAO by 1–3 months. Large-scale anomalies in sea level pressure and horizontal wind at 850 hPa level support the strength of AO/AAO-coral teleconnections. In addition, a comparison with oxygen isotope records from two coral sites in neighboring oceans yields significant AO and AAO signatures with similar time lags. These results help to better understand monsoon climates and their teleconnection to high-latitude climate changes.

  6. Impact of climate change on Antarctic krill

    NARCIS (Netherlands)

    Florentino De Souza Silva, A.P.; Atkinson, A.; Kawaguchi, S.; Bravo Rebolledo, E.; Franeker, van J.A.

    2012-01-01

    Antarctic krill Euphausia superba (hereafter ‘krill’) occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has increased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of

  7. Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes

    OpenAIRE

    Kraus,Stefan; Kurbatov,Andrei; Yates,Martin

    2013-01-01

    In the northern Antarctic Peninsula area, at least 12 Late Plelstocene-Holocene volcanic centers could be potential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoes using major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. The volcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguish between volcanic centers located on ...

  8. Recent Rapid Regional Climate Warming on the Antarctic Peninsula

    Science.gov (United States)

    Vaughan, D. G.; Marshall, G. J.; Connolley, W. M.; Parkinson, C.; Mulvaney, R.; Hodgson, D. A.; King, J. C.; Pudsey, C. J.; Turner, J.

    2002-12-01

    The Intergovernmental Panel on Climate Change (IPCC) confirmed that global warming was 0.6 ñ 0.2 degrees C during the 20th Century and cited increases in greenhouse gases as a likely contributor. But this average conceals the complexity of observed climate change, which is seasonally biased, decadally variable and geographically patchy. In particular, over the last 50 years three high-latitude areas have undergone recent rapid regional (RRR) warming ? substantially more rapid than the global mean. We discuss the spatial and temporal significance of RRR warming in one area, the Antarctic Peninsula. New analyses of station records show no ubiquitous polar amplification of global warming but significant RRR warming on the Antarctic Peninsula. We investigate the likelihood that this could be amplification of a global warming, and use climate-proxy data to indicate that this RRR warming on the Antarctic Peninsula is unprecedented over the last two millennia and unlikely to be a natural mode of variability. We can show a strong connection between RRR warming and reduced sea-ice duration in an area on the west of the Antarctic Peninsula, but here we cannot yet distinguish cause and effect. Thus for the present we cannot determine which process causes the RRR warming, and until the mechanism initiating and sustaining it is understood, and is convincingly reproduced in climate models, we lack a sound basis for predicting climate change in this region over the coming century.

  9. Maritime antarctic lakes as sentinels of climate change

    OpenAIRE

    Camacho, A.; Rochera, C.; Villaescusa, J. A.; Velázquez, D.; Toro, M.; Rico, E.; Fernández-Valiente, E.; Justel, Ana; Bañón García, Manuel; Quesada, Antonio

    2012-01-01

    Remote lakes, such as lakes from the Maritime Antarctica, can be used as sentinels of climate change, because they are mostly free of direct anthropogenic pressures, and they experience climate change as a main stressor capable of modifying the ecosystem structure and function. In this paper, the content of a lecture that has been presented at the First Conference of Lake Sustainability, which has been centred in our studies on lakes from Byers Peninsula (Maritime Antarctic...

  10. Climate change and trophic response of the Antarctic bottom fauna.

    Directory of Open Access Journals (Sweden)

    Richard B Aronson

    Full Text Available BACKGROUND: As Earth warms, temperate and subpolar marine species will increasingly shift their geographic ranges poleward. The endemic shelf fauna of Antarctica is especially vulnerable to climate-mediated biological invasions because cold temperatures currently exclude the durophagous (shell-breaking predators that structure shallow-benthic communities elsewhere. METHODOLOGY/PRINCIPAL FINDINGS: We used the Eocene fossil record from Seymour Island, Antarctic Peninsula, to project specifically how global warming will reorganize the nearshore benthos of Antarctica. A long-term cooling trend, which began with a sharp temperature drop approximately 41 Ma (million years ago, eliminated durophagous predators-teleosts (modern bony fish, decapod crustaceans (crabs and lobsters and almost all neoselachian elasmobranchs (modern sharks and rays-from Antarctic nearshore waters after the Eocene. Even prior to those extinctions, durophagous predators became less active as coastal sea temperatures declined from 41 Ma to the end of the Eocene, approximately 33.5 Ma. In response, dense populations of suspension-feeding ophiuroids and crinoids abruptly appeared. Dense aggregations of brachiopods transcended the cooling event with no apparent change in predation pressure, nor were there changes in the frequency of shell-drilling predation on venerid bivalves. CONCLUSIONS/SIGNIFICANCE: Rapid warming in the Southern Ocean is now removing the physiological barriers to shell-breaking predators, and crabs are returning to the Antarctic Peninsula. Over the coming decades to centuries, we predict a rapid reversal of the Eocene trends. Increasing predation will reduce or eliminate extant dense populations of suspension-feeding echinoderms from nearshore habitats along the Peninsula while brachiopods will continue to form large populations, and the intensity of shell-drilling predation on infaunal bivalves will not change appreciably. In time the ecological effects of

  11. Climate change and trophic response of the Antarctic bottom fauna.

    Science.gov (United States)

    Aronson, Richard B; Moody, Ryan M; Ivany, Linda C; Blake, Daniel B; Werner, John E; Glass, Alexander

    2009-01-01

    As Earth warms, temperate and subpolar marine species will increasingly shift their geographic ranges poleward. The endemic shelf fauna of Antarctica is especially vulnerable to climate-mediated biological invasions because cold temperatures currently exclude the durophagous (shell-breaking) predators that structure shallow-benthic communities elsewhere. We used the Eocene fossil record from Seymour Island, Antarctic Peninsula, to project specifically how global warming will reorganize the nearshore benthos of Antarctica. A long-term cooling trend, which began with a sharp temperature drop approximately 41 Ma (million years ago), eliminated durophagous predators-teleosts (modern bony fish), decapod crustaceans (crabs and lobsters) and almost all neoselachian elasmobranchs (modern sharks and rays)-from Antarctic nearshore waters after the Eocene. Even prior to those extinctions, durophagous predators became less active as coastal sea temperatures declined from 41 Ma to the end of the Eocene, approximately 33.5 Ma. In response, dense populations of suspension-feeding ophiuroids and crinoids abruptly appeared. Dense aggregations of brachiopods transcended the cooling event with no apparent change in predation pressure, nor were there changes in the frequency of shell-drilling predation on venerid bivalves. Rapid warming in the Southern Ocean is now removing the physiological barriers to shell-breaking predators, and crabs are returning to the Antarctic Peninsula. Over the coming decades to centuries, we predict a rapid reversal of the Eocene trends. Increasing predation will reduce or eliminate extant dense populations of suspension-feeding echinoderms from nearshore habitats along the Peninsula while brachiopods will continue to form large populations, and the intensity of shell-drilling predation on infaunal bivalves will not change appreciably. In time the ecological effects of global warming could spread to other portions of the Antarctic coast. The differential

  12. Climate change drives expansion of Antarctic ice-free habitat.

    Science.gov (United States)

    Lee, Jasmine R; Raymond, Ben; Bracegirdle, Thomas J; Chadès, Iadine; Fuller, Richard A; Shaw, Justine D; Terauds, Aleks

    2017-07-06

    Antarctic terrestrial biodiversity occurs almost exclusively in ice-free areas that cover less than 1% of the continent. Climate change will alter the extent and configuration of ice-free areas, yet the distribution and severity of these effects remain unclear. Here we quantify the impact of twenty-first century climate change on ice-free areas under two Intergovernmental Panel on Climate Change (IPCC) climate forcing scenarios using temperature-index melt modelling. Under the strongest forcing scenario, ice-free areas could expand by over 17,000 km 2 by the end of the century, close to a 25% increase. Most of this expansion will occur in the Antarctic Peninsula, where a threefold increase in ice-free area could drastically change the availability and connectivity of biodiversity habitat. Isolated ice-free areas will coalesce, and while the effects on biodiversity are uncertain, we hypothesize that they could eventually lead to increasing regional-scale biotic homogenization, the extinction of less-competitive species and the spread of invasive species.

  13. Climate change drives expansion of Antarctic ice-free habitat

    Science.gov (United States)

    Lee, Jasmine R.; Raymond, Ben; Bracegirdle, Thomas J.; Chadès, Iadine; Fuller, Richard A.; Shaw, Justine D.; Terauds, Aleks

    2017-07-01

    Antarctic terrestrial biodiversity occurs almost exclusively in ice-free areas that cover less than 1% of the continent. Climate change will alter the extent and configuration of ice-free areas, yet the distribution and severity of these effects remain unclear. Here we quantify the impact of twenty-first century climate change on ice-free areas under two Intergovernmental Panel on Climate Change (IPCC) climate forcing scenarios using temperature-index melt modelling. Under the strongest forcing scenario, ice-free areas could expand by over 17,000 km2 by the end of the century, close to a 25% increase. Most of this expansion will occur in the Antarctic Peninsula, where a threefold increase in ice-free area could drastically change the availability and connectivity of biodiversity habitat. Isolated ice-free areas will coalesce, and while the effects on biodiversity are uncertain, we hypothesize that they could eventually lead to increasing regional-scale biotic homogenization, the extinction of less-competitive species and the spread of invasive species.

  14. Impact of Antarctic mixed-phase clouds on climate.

    Science.gov (United States)

    Lawson, R Paul; Gettelman, Andrew

    2014-12-23

    Precious little is known about the composition of low-level clouds over the Antarctic Plateau and their effect on climate. In situ measurements at the South Pole using a unique tethered balloon system and ground-based lidar reveal a much higher than anticipated incidence of low-level, mixed-phase clouds (i.e., consisting of supercooled liquid water drops and ice crystals). The high incidence of mixed-phase clouds is currently poorly represented in global climate models (GCMs). As a result, the effects that mixed-phase clouds have on climate predictions are highly uncertain. We modify the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) GCM to align with the new observations and evaluate the radiative effects on a continental scale. The net cloud radiative effects (CREs) over Antarctica are increased by +7.4 Wm(-2), and although this is a significant change, a much larger effect occurs when the modified model physics are extended beyond the Antarctic continent. The simulations show significant net CRE over the Southern Ocean storm tracks, where recent measurements also indicate substantial regions of supercooled liquid. These sensitivity tests confirm that Southern Ocean CREs are strongly sensitive to mixed-phase clouds colder than -20 °C.

  15. Antarctic Holocene climate change: A benthic foraminiferal stable isotope record from Palmer Deep

    OpenAIRE

    Shevenell, A. E.; Kennett, J. P.

    2002-01-01

    The first moderate- to high-resolution Holocene marine stable isotope record from the nearshore Antarctic continental shelf (Ocean Drilling Program (ODP) Hole 1098B) suggests sensitivity of the western Antarctic Peninsula hydrography to westerly wind strength and El Nino-Southern Oscillation (ENSO)-like climate variability. Despite proximity to corrosive Antarctic water masses, sufficient CaCO3 in Palmer Deep sediments exists to provide a high-quality stable isotopic record (especially in the...

  16. Climate-dependent evolution of Antarctic ectotherms: An integrative analysis

    Science.gov (United States)

    Pörtner, Hans O.

    2006-04-01

    The paper explores the climate-dependent evolution of marine Antarctic fauna and tries to identify key mechanisms involved as well as the driving forces that have caused the physiological and life history characteristics observed today. In an integrative approach it uses the recent concept of oxygen and capacity limited thermal tolerance to identify potential links between molecular, cellular, whole-organism, and ecological characteristics of marine animal life in the Antarctic. As a generalized pattern, minimization of baseline energy costs, for the sake of maximized growth in the cold, appears as one over-arching principle shaping the evolution and functioning of Antarctic marine ectotherms. This conclusion is supported by recent comparisons with (sub-) Arctic ectotherms, where elevated levels of energy turnover result at unstable, including cold temperatures, and are related to wide windows of thermal tolerance and associated metabolic features. At biochemical levels, metabolic regulation at low temperatures in general, is supported by the cold compensation of enzyme kinetic parameters like substrate affinities and turnover numbers, through minute structural modifications of the enzyme molecule. These involve a shift in protein folding, sometimes supported by the replacement of individual amino acids. The hypothesis is developed that efficient metabolic regulation at low rates in Antarctic marine stenotherms occurs through high mitochondrial densities at low capacities and possibly enhanced levels of Arrhenius activation energies or activation enthalpies. This contrasts the more costly patterns of metabolic regulation at elevated rates in cold-adapted eurytherms. Energy savings in Antarctic ectotherms, largely exemplified in fish, typically involve low-cost, diffusive oxygen distribution due to high density of lipid membranes, loss of haemoglobin, myoglobin and the heat shock response, reduced anaerobic capacity, large myocytes with low ion exchange activities

  17. Climate Change Impacts in the sub-Antarctic Islands Technical Report N.2 of ONERC

    International Nuclear Information System (INIS)

    2009-01-01

    Difficult to apprehend as a whole, the polar regions constitute the Arctic to the North, an ocean surrounded by emerged lands, and the Antarctic to the South, a continent bordered by the Austral Ocean where a belt of sub Antarctic islands lies. Climate change impacts on sub Antarctic islands are varied, direct and indirect: glacier retreat, more favourable conditions for introduced species, marine biodiversity modification, etc. This report discusses the French, British, Australian, South African and New Zealand sub Antarctic islands, the climatic evolutions and the resulting impacts, focused especially on biodiversity. The Observatoire National sur les Effets du Rechauffement Climatique and the International Polar Foundation have been joined in this endeavour by the French polar institute Paul-Emile Victor, the administration of the French Southern and Antarctic Lands (TAAF in French) and the International Union for the Conservation of Nature. (authors)

  18. Food choice of Antarctic soil arthropods clarified by stable isotope signatures

    NARCIS (Netherlands)

    Bokhorst, S.F.; Ronfort, C.; Huiskes, A.H.L.; Convey, P.; Aerts, R.A.M.

    2007-01-01

    Antarctic soil ecosystems are amongst the most simplified on Earth and include only few soil arthropod species, generally believed to be opportunistic omnivorous feeders. Using stable isotopic analyses, we investigated the food choice of two common and widely distributed Antarctic soil arthropod

  19. Climate Prediction Center(CPC)Monthly Antarctic Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Antarctic Oscillation (AAO) is a leading teleconnection pattern in the Southern Hemisphere circulation. It is calculated as the first Empirical Orthogonal...

  20. Climate Prediction Center (CPC) Daily Antarctic Oscillation Index

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Antarctic Oscillation (AAO) is a leading teleconnection pattern in the Southern Hemisphere circulation. It is calculated as the first Empirical Orthogonal...

  1. Prospects for surviving climate change in Antarctic aquatic species

    Directory of Open Access Journals (Sweden)

    Peck Lloyd S

    2005-06-01

    Full Text Available Abstract Maritime Antarctic freshwater habitats are amongst the fastest changing environments on Earth. Temperatures have risen around 1°C and ice cover has dramatically decreased in 15 years. Few animal species inhabit these sites, but the fairy shrimp Branchinecta gaini typifies those that do. This species survives up to 25°C daily temperature fluctuations in summer and passes winter as eggs at temperatures down to -25°C. Its annual temperature envelope is, therefore around 50°C. This is typical of Antarctic terrestrial species, which exhibit great physiological flexibility in coping with temperature fluctuations. The rapidly changing conditions in the Maritime Antarctic are enhancing fitness in these species by increasing the time available for feeding, growth and reproduction, as well as increasing productivity in lakes. The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-Antarctic sites. In contrast the marine Antarctic environment has very stable temperatures. However, seasonality is intense with very short summers and long winter periods of low to no algal productivity. Marine animals grow slowly, have long generation times, low metabolic rates and low levels of activity. They also die at temperatures between +5°C and +10°C. Failure of oxygen supply mechanisms and loss of aerobic scope defines upper temperature limits. As temperature rises, their ability to perform work declines rapidly before lethal limits are reached, such that 50% of populations of clams and limpets cannot perform essential activities at 2–3°C, and all scallops are incapable of swimming at 2°C. Currently there is little evidence of temperature change in Antarctic marine sites. Models predict average global sea temperatures will rise by around 2°C by 2100. Such a rise would take many Antarctic marine animals beyond their survival limits. Animals have 3 mechanisms for

  2. Antarctic climate variability on regional and continental scales over the last 2000 years

    Science.gov (United States)

    Stenni, Barbara; Curran, Mark A. J.; Abram, Nerilie J.; Orsi, Anais; Goursaud, Sentia; Masson-Delmotte, Valerie; Neukom, Raphael; Goosse, Hugues; Divine, Dmitry; van Ommen, Tas; Steig, Eric J.; Dixon, Daniel A.; Thomas, Elizabeth R.; Bertler, Nancy A. N.; Isaksson, Elisabeth; Ekaykin, Alexey; Werner, Martin; Frezzotti, Massimo

    2017-11-01

    Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i) a temperature scaling based on the δ18O-temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii) a composite-plus-scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these

  3. Antarctic climate variability on regional and continental scales over the last 2000 years

    Directory of Open Access Journals (Sweden)

    B. Stenni

    2017-11-01

    Full Text Available Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i a temperature scaling based on the δ18O–temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii a composite-plus-scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the

  4. Improved climate model evaluation using a new, 750-year Antarctic-wide snow accumulation product

    Science.gov (United States)

    Medley, B.; Thomas, E. R.

    2017-12-01

    Snow that accumulates over the cold, dry grounded ice of Antarctica is an important component of its mass balance, mitigating the ice sheet's contribution to sea level. Secular trends in accumulation not only result trends in the mass balance of the Antarctic Ice Sheet, but also directly and indirectly impact surface height changes. Long-term and spatiotemporally complete records of snow accumulation are needed to understand part and present Antarctic-wide mass balance, to convert from altimetry derived volume change to mass change, and to evaluate the ability of climate models to reproduce the observed climate change. We need measurements in both time and space, yet they typically sample one dimension at the expense of the other. Here, we develop a spatially complete, annually resolved snow accumulation product for the Antarctic Ice Sheet over the past 750 years by combining a newly compiled database of ice core accumulation records with climate model output. We mainly focus on climate model evaluation. Because the product spans several centuries, we can evaluate model ability in representing the preindustrial as well as present day accumulation change. Significant long-term trends in snow accumulation are found over the Ross and Bellingshausen Sea sectors of West Antarctica, the Antarctic Peninsula, and several sectors in East Antarctica. These results suggest that change is more complex over the Antarctic Ice Sheet than a simple uniform change (i.e., more snowfall in a warming world), which highlights the importance of atmospheric circulation as a major driver of change. By evaluating several climate models' ability to reproduce the observed trends, we can deduce whether their projections are reasonable or potentially biased where the latter would result in a misrepresentation of the Antarctic contribution to sea level.

  5. The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

    2014-01-01

    Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate

  6. Projected asymmetric response of Adélie penguins to Antarctic climate change

    Science.gov (United States)

    Cimino, Megan A.; Lynch, Heather J.; Saba, Vincent S.; Oliver, Matthew J.

    2016-06-01

    The contribution of climate change to shifts in a species’ geographic distribution is a critical and often unresolved ecological question. Climate change in Antarctica is asymmetric, with cooling in parts of the continent and warming along the West Antarctic Peninsula (WAP). The Adélie penguin (Pygoscelis adeliae) is a circumpolar meso-predator exposed to the full range of Antarctic climate and is undergoing dramatic population shifts coincident with climate change. We used true presence-absence data on Adélie penguin breeding colonies to estimate past and future changes in habitat suitability during the chick-rearing period based on historic satellite observations and future climate model projections. During the contemporary period, declining Adélie penguin populations experienced more years with warm sea surface temperature compared to populations that are increasing. Based on this relationship, we project that one-third of current Adélie penguin colonies, representing ~20% of their current population, may be in decline by 2060. However, climate model projections suggest refugia may exist in continental Antarctica beyond 2099, buffering species-wide declines. Climate change impacts on penguins in the Antarctic will likely be highly site specific based on regional climate trends, and a southward contraction in the range of Adélie penguins is likely over the next century.

  7. Changes in Arctic and Antarctic Sea Ice as a Microcosm of Global Climate Change

    Science.gov (United States)

    Parkinson, Claire L.

    2014-01-01

    Polar sea ice is a key element of the climate system and has now been monitored through satellite observations for over three and a half decades. The satellite observations reveal considerable information about polar ice and its changes since the late 1970s, including a prominent downward trend in Arctic sea ice coverage and a much lesser upward trend in Antarctic sea ice coverage, illustrative of the important fact that climate change entails spatial contrasts. The decreasing ice coverage in the Arctic corresponds well with contemporaneous Arctic warming and exhibits particularly large decreases in the summers of 2007 and 2012, influenced by both preconditioning and atmospheric conditions. The increasing ice coverage in the Antarctic is not as readily explained, but spatial differences in the Antarctic trends suggest a possible connection with atmospheric circulation changes that have perhaps been influenced by the Antarctic ozone hole. The changes in the polar ice covers and the issues surrounding those changes have many commonalities with broader climate changes and their surrounding issues, allowing the sea ice changes to be viewed in some important ways as a microcosm of global climate change.

  8. Biodiversity change after climate-induced ice-shelf collapse in the Antarctic

    NARCIS (Netherlands)

    Gutt, J.; Barratt, I.; Domack, E.; Scheidat, M.

    2011-01-01

    The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The

  9. A new albedo parameterization for use in climate models over the Antarctic ice sheet

    NARCIS (Netherlands)

    Kuipers Munneke, P.|info:eu-repo/dai/nl/304831891; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; Flanner, M.G.; Gardner, A.S.; van de Berg, W.J.|info:eu-repo/dai/nl/304831611

    2011-01-01

    A parameterization for broadband snow surface albedo, based on snow grain size evolution, cloud optical thickness, and solar zenith angle, is implemented into a regional climate model for Antarctica and validated against field observations of albedo for the period 1995–2004. Over the Antarctic

  10. Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming.

    NARCIS (Netherlands)

    Rinnan, R.; Rousk, J.; Yergeau, E.; Kowalchuk, G.A.; Baath, E.

    2009-01-01

    Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short-term temperature dependencies of Antarctic soil bacterial community growth rates, using

  11. Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

    NARCIS (Netherlands)

    Rinnan, R.; Rousk, J.; Yergeau, E.; Kowalchuk, G.A.; Baath, E.

    2009-01-01

    Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short-term temperature dependencies of Antarctic soil bacterial community growth rates, using

  12. A reversal of fortunes: climate change 'winners' and 'losers' in Antarctic Peninsula penguins.

    Science.gov (United States)

    Clucas, Gemma V; Dunn, Michael J; Dyke, Gareth; Emslie, Steven D; Naveen, Ron; Polito, Michael J; Pybus, Oliver G; Rogers, Alex D; Hart, Tom

    2014-06-12

    Climate change is a major threat to global biodiversity. Antarctic ecosystems are no exception. Investigating past species responses to climatic events can distinguish natural from anthropogenic impacts. Climate change produces 'winners', species that benefit from these events and 'losers', species that decline or become extinct. Using molecular techniques, we assess the demographic history and population structure of Pygoscelis penguins in the Scotia Arc related to climate warming after the Last Glacial Maximum (LGM). All three pygoscelid penguins responded positively to post-LGM warming by expanding from glacial refugia, with those breeding at higher latitudes expanding most. Northern (Pygoscelis papua papua) and Southern (Pygoscelis papua ellsworthii) gentoo sub-species likely diverged during the LGM. Comparing historical responses with the literature on current trends, we see Southern gentoo penguins are responding to current warming as they did during post-LGM warming, expanding their range southwards. Conversely, Adélie and chinstrap penguins are experiencing a 'reversal of fortunes' as they are now declining in the Antarctic Peninsula, the opposite of their response to post-LGM warming. This suggests current climate warming has decoupled historic population responses in the Antarctic Peninsula, favoring generalist gentoo penguins as climate change 'winners', while Adélie and chinstrap penguins have become climate change 'losers'.

  13. Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

    DEFF Research Database (Denmark)

    Rinnan, Riikka; Rousk, Johannes; Yergeau, Etienne

    2009-01-01

    the leucine incorporation technique, in order to predict future changes in temperature sensitivity of resident soil bacterial communities. Soil samples were collected along a climate gradient consisting of locations on the Antarctic Peninsula (Anchorage Island, 67 °34'S, 68 °08'W), Signy Island (60 °43'S, 45...... °38'W) and the Falkland Islands (51 °76'S 59 °03'W). At each location, experimental plots were subjected to warming by open top chambers (OTCs) and paired with control plots on vegetated and fell-field habitats. The bacterial communities were adapted to the mean annual temperature of their environment...

  14. Invited review: climate change impacts in polar regions: lessons from Antarctic moss bank archives.

    Science.gov (United States)

    Royles, Jessica; Griffiths, Howard

    2015-03-01

    Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies and determinants of moss growth for contrasting continental and maritime Antarctic regions, as informed by 13C and 18O signals in organic material. Rates of moss accumulation are more than three times higher in the maritime Antarctic than continental Antarctica with growing season length being a critical determinant of growth rate, and high carbon isotope discrimination values reflecting optimal hydration conditions. Correlation plots of 13C and 18O values show that species (Chorisodontium aciphyllum / Polytrichum strictum) and growth form (hummock / bank) are the major determinants of measured isotope ratios. The interplay between moss growth form, photosynthetic physiology, water status and isotope composition are compared with developments of secondary proxies, such as chlorophyll fluorescence. These approaches provide a framework to consider the potential impact of climate change on terrestrial Antarctic habitats as well as having implications for future studies of temperate, boreal and Arctic peatlands. There are many urgent ecological and environmental problems in the Arctic related to mosses in a changing climate, but the geographical ranges of species and life-forms are difficult to track individually. Our goal was to translate what we have learned from the more simple systems in Antarctica, for application to Arctic habitats. © 2014 John Wiley & Sons Ltd.

  15. Antarctic Forcing of Abrupt Global Climate Change During Isotope Stage 3

    Science.gov (United States)

    Turney, Christian; Jones, Richard; Phipps, Steven; Thomas, Zoë; Hogg, Alan; Kershaw, Peter; Fogwill, Christopher; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad; Staff, Richard; Grosvenor, Mark; Golledge, Nicholas; Haberle, Simon

    2016-04-01

    Contrasting Greenland and Antarctic temperature trends during the late Pleistocene (60,000 to 11,650 years ago) are thought to be driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'), with millennial-scale cooling Dansgaard-Oeschger (D-O) events in the north leading warming in the south. An alternative origin for these abrupt climate shifts, however, is the Southern Hemisphere whereby changes are transmitted globally via atmospheric and/or oceanic teleconnections. Testing these competing hypotheses is challenging given the relatively large uncertainties associated with dating terrestrial, marine and ice core chronologies. Here we use a fully coupled climate system model to investigate whether freshening of the Southern Ocean has extra-regional climate impacts. Focusing on an Isotope Stage 3 cooling event preserved in Antarctic ice cores immediately prior to Antarctic Isotope Maximum 4 (AIM 4; around 29,000 years ago) we undertook an ensemble of transient meltwater simulations. We observe no impact on the Atlantic Meridional Overturning Circulation (AMOC) from freshwater hosing in the Southern Ocean but a dramatic warming over the North Atlantic and contrasting precipitation patterns across the low latitudes. Exploiting a new bidecadally-resolved 14C calibration dataset obtained from New Zealand kauri (Agathis australis) we undertook intensive radiocarbon dating and high-resolution multiproxy analysis of the tropical Australia Lynch's Crater terrestrial peat sequence spanning this same period and find a synchronous change in hydroclimate to the purported meltwater event in the Southern Ocean. Our results imply Southern Ocean dynamics played a significant role in driving global climate change across this period via atmospheric teleconnections, with implications for other abrupt events through the late Pleistocene.

  16. Ancient climate change, antifreeze, and the evolutionary diversification of Antarctic fishes.

    Science.gov (United States)

    Near, Thomas J; Dornburg, Alex; Kuhn, Kristen L; Eastman, Joseph T; Pennington, Jillian N; Patarnello, Tomaso; Zane, Lorenzo; Fernández, Daniel A; Jones, Christopher D

    2012-02-28

    The Southern Ocean around Antarctica is among the most rapidly warming regions on Earth, but has experienced episodic climate change during the past 40 million years. It remains unclear how ancient periods of climate change have shaped Antarctic biodiversity. The origin of antifreeze glycoproteins (AFGPs) in Antarctic notothenioid fishes has become a classic example of how the evolution of a key innovation in response to climate change can drive adaptive radiation. By using a time-calibrated molecular phylogeny of notothenioids and reconstructed paleoclimate, we demonstrate that the origin of AFGP occurred between 42 and 22 Ma, which includes a period of global cooling approximately 35 Ma. However, the most species-rich lineages diversified and evolved significant ecological differences at least 10 million years after the origin of AFGPs, during a second cooling event in the Late Miocene (11.6-5.3 Ma). This pattern indicates that AFGP was not the sole trigger of the notothenioid adaptive radiation. Instead, the bulk of the species richness and ecological diversity originated during the Late Miocene and into the Early Pliocene, a time coincident with the origin of polar conditions and increased ice activity in the Southern Ocean. Our results challenge the current understanding of the evolution of Antarctic notothenioids suggesting that the ecological opportunity that underlies this adaptive radiation is not linked to a single trait, but rather to a combination of freeze avoidance offered by AFGPs and subsequent exploitation of new habitats and open niches created by increased glacial and ice sheet activity.

  17. Reassessing the penultimate interglacial analog for current climate change, evidence from Antarctic dust

    Science.gov (United States)

    Aarons, S. M.; Aciego, S.; McConnell, J.

    2017-12-01

    Dust emissions and transport are linked to spatial and temporal climate variability, with dust provenance providing clues to past climate and climate impacts. The penultimate interglacial period (MIS 5e) has been suggested as an analog to Holocene climate change. We present the first evaluation of the MIS 5e ice archive developed at Taylor Glacier, East Antarctica and provide a record of dust transported to Taylor Glacier during MIS 5e. Our record shows significant differences between MIS 5e, Holocene, and pre-industrial dust transported to East Antarctica. The MIS 5e dust is sourced from New Zealand and southern South America (SSA), while the Holocene dust is sourced from local Antarctic, SSA, and potentially Australian sources. This profound change in composition suggests a variation in atmospheric transport pathways and/or paleo-environmental conditions between the interglacial periods, and indicates that MIS 5e should be reassessed as an analog for climate change and associated impacts.

  18. Antarctic Circumpolar Current Dynamics and Their Relation to Antarctic Ice Sheet and Perennial Sea-Ice Variability in the Central Drake Passage During the Last Climate Cycle

    Science.gov (United States)

    Kuhn, G.; Wu, S.; Hass, H. C.; Klages, J. P.; Zheng, X.; Arz, H. W.; Esper, O.; Hillenbrand, C. D.; Lange, C.; Lamy, F.; Lohmann, G.; Müller, J.; McCave, I. N. N.; Nürnberg, D.; Roberts, J.; Tiedemann, R.; Timmermann, A.; Titschack, J.; Zhang, X.

    2017-12-01

    The evolution of the Antarctic Ice Sheet during the last climate cycle and the interrelation to global atmospheric and ocean circulation remains controversial and plays an important role for our understanding of ice sheet response to modern global warming. The timing and sequence of deglacial warming is relevant for understanding the variability and sensitivity of the Antarctic Ice Sheet to climatic changes, and the continuing rise of atmospheric greenhouse gas concentrations. The Antarctic Ice Sheet is a pivotal component of the global water budget. Freshwater fluxes from the ice sheet may affect the Antarctic Circumpolar Current (ACC), which is strongly impacted by the westerly wind belt in the Southern Hemisphere (SHWW) and constricted to its narrowest extent in the Drake Passage. The flow of ACC water masses through Drake Passage is, therefore, crucial for advancing our understanding of the Southern Ocean's role in global meridional overturning circulation and global climate change. In order to address orbital and millennial-scale variability of the Antarctic ice sheet and the ACC, we applied a multi-proxy approach on a sediment core from the central Drake Passage including grain size, iceberg-rafted debris, mineral dust, bulk chemical and mineralogical composition, and physical properties. In combination with already published and new sediment records from the Drake Passage and Scotia Sea, as well as high-resolution data from Antarctic ice cores (WDC, EDML), we now have evidence that during glacial times a more northerly extent of the perennial sea-ice zone decreased ACC current velocities in the central Drake Passage. During deglaciation the SHWW shifted southwards due to a decreasing temperature gradient between subtropical and polar latitudes caused by sea ice and ice sheet decline. This in turn caused Southern Hemisphere warming, a more vigorous ACC, stronger Southern Ocean ventilation, and warm Circumpolar Deep Water (CDW) upwelling on Antarctic shelves

  19. Seafloor geomorphology of western Antarctic Peninsula bays: a signature of ice flow behaviour

    Science.gov (United States)

    Munoz, Yuribia P.; Wellner, Julia S.

    2018-01-01

    Glacial geomorphology is used in Antarctica to reconstruct ice advance during the Last Glacial Maximum and subsequent retreat across the continental shelf. Analogous geomorphic assemblages are found in glaciated fjords and are used to interpret the glacial history and glacial dynamics in those areas. In addition, understanding the distribution of submarine landforms in bays and the local controls exerted on ice flow can help improve numerical models by providing constraints through these drainage areas. We present multibeam swath bathymetry from several bays in the South Shetland Islands and the western Antarctic Peninsula. The submarine landforms are described and interpreted in detail. A schematic model was developed showing the features found in the bays: from glacial lineations and moraines in the inner bay to grounding zone wedges and drumlinoid features in the middle bay and streamlined features and meltwater channels in the outer bay areas. In addition, we analysed local variables in the bays and observed the following: (1) the number of landforms found in the bays scales to the size of the bay, but the geometry of the bays dictates the types of features that form; specifically, we observe a correlation between the bay width and the number of transverse features present in the bays. (2) The smaller seafloor features are present only in the smaller glacial systems, indicating that short-lived atmospheric and oceanographic fluctuations, responsible for the formation of these landforms, are only recorded in these smaller systems. (3) Meltwater channels are abundant on the seafloor, but some are subglacial, carved in bedrock, and some are modern erosional features, carved on soft sediment. Lastly, based on geomorphological evidence, we propose the features found in some of the proximal bay areas were formed during a recent glacial advance, likely the Little Ice Age.

  20. Antarctic fellfield response to climate change: a tripartite synthesis of experimental data.

    Science.gov (United States)

    Kennedy, Andrew D

    1996-07-01

    This paper explores the biological consequences of climate change by integrating the results of a tripartite investigation involving fumarole, field manipulation and laboratory incubation experiments. The geographical region for this research is the maritime Antarctic. Under contemporary climate conditions, the lithosols in this region support only a sparse cryptogamic flora of limited taxonomic diversity and low structural complexity. However, the existence in geothermal areas of temperate species (e.g. Campylopus introflexus, Marchantia polymorpha, Philonotis acicularis) growing outside their normal biogeographical range suggests that elevated temperature and humidity may alter the trajectory of community development towards Magellanic or Patagonian composition. Productivity is also likely to increase, as indicated by significantly greater vegetative biomass recorded beneath climate-ameliorating soil covers than in controls. Barren fellfield soil samples transplanted to the laboratory and incubated at temperatures of 2-25°C show rapid development of moss, algae and lichen propagules in the range 15-25°C. A variety of species develop that have not been recorded in the field. The presence of exotic taxa indicates the existence of a dormant propagule bank in maritime Antarctic soils and suggests that no significant delay is likely to occur between the onset of climate warming and community development: instead, rapid establishment of those species favoured by the new climate conditions will yield a distinct founder effect, with increasing above- and below-ground biomass stimulating biogeochemical cycling. It is argued that the combined results of this synthesis identify generic responses to climate change arising from the importance at high latitudes of low temperature and water availability as limiting factors: subject to other growth resources being non-limiting, a more consistent stimulatory response to climate change may be expected than in temperate or

  1. Biodiversity change after climate-induced ice-shelf collapse in the Antarctic

    Science.gov (United States)

    Gutt, Julian; Barratt, Iain; Domack, Eugene; d'Udekem d'Acoz, Cédric; Dimmler, Werner; Grémare, Antoine; Heilmayer, Olaf; Isla, Enrique; Janussen, Dorte; Jorgensen, Elaina; Kock, Karl-Hermann; Sophia Lehnert, Linn; López-Gonzáles, Pablo; Langner, Stephanie; Linse, Katrin; Eugenia Manjón-Cabeza, Maria; Meißner, Meike; Montiel, Americo; Raes, Maarten; Robert, Henri; Rose, Armin; Sañé Schepisi, Elisabet; Saucède, Thomas; Scheidat, Meike; Schenke, Hans-Werner; Seiler, Jan; Smith, Craig

    2011-03-01

    The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabenthic shelf species interspersed. Antarctic Minke whales and seals utilised the Larsen A/B area to feed on presumably newly established krill and pelagic fish biomass. Ecosystem impacts also extended well beyond the zone of ice-shelf collapse, with areas of high benthic disturbance resulting from scour by icebergs discharged from the Larsen embayments.

  2. Antarctic climate, Southern Ocean circulation patterns, and deep water formation during the Eocene

    Science.gov (United States)

    Huck, Claire E.; van de Flierdt, Tina; Bohaty, Steven M.; Hammond, Samantha J.

    2017-07-01

    We assess early-to-middle Eocene seawater neodymium (Nd) isotope records from seven Southern Ocean deep-sea drill sites to evaluate the role of Southern Ocean circulation in long-term Cenozoic climate change. Our study sites are strategically located on either side of the Tasman Gateway and are positioned at a range of shallow (fish teeth at intermediate/deep Indian Ocean pelagic sites (Ocean Drilling Program (ODP) Sites 738 and 757 and Deep Sea Drilling Project (DSDP) Site 264), indicate a dominant Southern Ocean-sourced contribution to regional deep waters (ɛNd(t) = -9.3 ± 1.5). IODP Site U1356 off the coast of Adélie Land, a locus of modern-day Antarctic Bottom Water production, is identified as a site of persistent deep water formation from the early Eocene to the Oligocene. East of the Tasman Gateway an additional local source of intermediate/deep water formation is inferred at ODP Site 277 in the SW Pacific Ocean (ɛNd(t) = -8.7 ± 1.5). Antarctic-proximal shelf sites (ODP Site 1171 and Site U1356) reveal a pronounced erosional event between 49 and 48 Ma, manifested by 2 ɛNd unit negative excursions in seawater chemistry toward the composition of bulk sediments at these sites. This erosional event coincides with the termination of peak global warmth following the Early Eocene Climatic Optimum and is associated with documented cooling across the study region and increased export of Antarctic deep waters, highlighting the complexity and importance of Southern Ocean circulation in the greenhouse climate of the Eocene.

  3. CO2-Induced Ocean Warming of the Antarctic Continental Shelf in an Eddying Global Climate Model

    Science.gov (United States)

    Goddard, Paul B.; Dufour, Carolina O.; Yin, Jianjun; Griffies, Stephen M.; Winton, Michael

    2017-10-01

    Ocean warming near the Antarctic ice shelves has critical implications for future ice sheet mass loss and global sea level rise. A global climate model with an eddying ocean is used to quantify the mechanisms contributing to ocean warming on the Antarctic continental shelf in an idealized 2xCO2 experiment. The results indicate that relatively large warm anomalies occur both in the upper 100 m and at depths above the shelf floor, which are controlled by different mechanisms. The near-surface ocean warming is primarily a response to enhanced onshore advective heat transport across the shelf break. The deep shelf warming is initiated by onshore intrusions of relatively warm Circumpolar Deep Water (CDW), in density classes that access the shelf, as well as the reduction of the vertical mixing of heat. CO2-induced shelf freshening influences both warming mechanisms. The shelf freshening slows vertical mixing by limiting gravitational instabilities and the upward diffusion of heat associated with CDW, resulting in the buildup of heat at depth. Meanwhile, freshening near the shelf break enhances the lateral density gradient of the Antarctic Slope Front (ASF) and disconnect isopycnals between the shelf and CDW, making cross-ASF heat exchange more difficult. However, at several locations along the ASF, the cross-ASF heat transport is less inhibited and heat can move onshore. Once onshore, lateral and vertical heat advection work to disperse the heat anomalies across the shelf region. Understanding the inhomogeneous Antarctic shelf warming will lead to better projections of future ice sheet mass loss.

  4. Past Penguin Colony Linkages to Climate Change and Catastrophic Volcanism on the Northern Antarctic Peninsula

    Science.gov (United States)

    Roberts, S. J.; Monien, P.; Foster, L. C.; Loftfield, J.; Schnetger, B.; Pearson, E. J.; Hocking, E. P.; Fretwell, P.; Ireland, L.; Ochyra, R.; Haworth, A.; Allen, C. S.; Brumsack, H. J.; Bentley, M.; Hodgson, D.

    2016-12-01

    Recent warming and reductions in sea-ice in some parts of Antarctica are thought to be having a negative impact on populations of `ice-dependent' penguin species (e.g., Emperor, Adélie) that feed at the sea-ice edge because populations of `ice-avoiding'/more `adaptable' species (e.g., Gentoo, Chinstrap) have remained stable or increased, and some Adélie colonies located in areas of sea-ice expansion have increased. This hypothesis is based on short observational records and limited subfossil evidence, but has not been tested over longer, mid-late Holocene, timescales on the Antarctic Peninsula. Between 1950-1997, the northern Antarctic Peninsula was one of the most rapidly warming regions in the Southern Hemisphere and, over the last 30 years, the largest breeding population of Gentoo penguins in Antarctica on Ardley Island, north-western Antarctic Peninsula, has increased. We tracked past changes in the Ardley Island penguin colony size by comparing detailed biogeochemical analysis of an 8,500-year Ardley Lake sediment profile with past records of penguin presence, climate and sea-ice extent across the Antarctic Peninsula and found that the colony also responded positively during some local-regionally warmer parts of the late Holocene. However, at least three large volcanic eruptions from nearby Deception Island had a devastating impact on the colony between 7000-2000 years ago, with colony recovery taking up to 800 years following the most disruptive period of volcanic activity c. 5500-5000 years ago.

  5. 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

  6. Will the Antarctic tardigradeAcutuncus antarcticusbe able to withstand environmental stresses related to global climate change?

    Science.gov (United States)

    Giovannini, Ilaria; Altiero, Tiziana; Guidetti, Roberto; Rebecchi, Lorena

    2018-02-20

    Because conditions in continental Antarctica are highly selective and extremely hostile to life, its biota is depauperate, but well adapted to live in this region. Global climate change has the potential to impact continental Antarctic organisms because of increasing temperatures and ultraviolet radiation. This research evaluates how ongoing climate changes will affect Antarctic species, and whether Antarctic organisms will be able to adapt to the new environmental conditions. Tardigrades represent one of the main terrestrial components of Antarctic meiofauna; therefore, the pan-Antarctic tardigrade Acutuncus antarcticus was used as model to predict the fate of Antarctic meiofauna threatened by climate change. Acutuncus antarcticus individuals tolerate events of desiccation, increased temperature and UV radiation. Both hydrated and desiccated animals tolerate increases in UV radiation, even though the desiccated animals are more resistant. Nevertheless, the survivorship of hydrated and desiccated animals is negatively affected by the combination of temperature and UV radiation, with the hydrated animals being more tolerant than desiccated animals. Finally, UV radiation has a negative impact on the life history traits of successive generations of A. antarcticus , causing an increase in egg reabsorption and teratological events. In the long run, A. antarcticus could be at risk of population reductions or even extinction. Nevertheless, because the changes in global climate will proceed gradually and an overlapping of temperature and UV increase could be limited in time, A. antarcticus , as well as many other Antarctic organisms, could have the potential to overcome global warming stresses, and/or the time and capability to adapt to the new environmental conditions. © 2018. Published by The Company of Biologists Ltd.

  7. Cretaceous-Tertiary boundary in the Antarctic: Climatic cooling precedes biotic crisis

    Science.gov (United States)

    Stott, Lowell D.; Kennett, James P.

    1988-01-01

    Stable isotopic investigations were conducted on calcareous microfossils across two deep sea Cretaceous-Tertiary boundary sequences on Maud Rise, Weddell Sea, Antarctica. The boundary is taken at the level of massive extinctions in calcareous planktonic microfossils, and coincides with a sharp lithologic change from pure calcareous ooze to calcareous ooze with a large volcanic clay component. The uppermost Maestrichtian is marked by a long-term decrease in delta value of 0 to 18 which spans most of the lower and middle A. mayaroensis Zone and represents a warming trend which culminated in surface water temperatures of about 16 C. At approximately 3 meters below the K-T boundary this warming trend terminates abruptly and benthic and planktonic isotopic records exhibit a rapid increase in delta value of 0 to 18 that continues up to the K-T boundary. The trend towards cooler surface water temperatures stops abruptly at the K-T boundary and delta value of 0 to 18 values remain relatively stable through the Paleocene. Comparison of the Antarctic sequence with the previously documented deep sea records in the South Atlantic reveal shifts of similar magnitude in the latest Maestrichtian. It is indicated that the Southern Ocean underwent the most significant, and apparently permanent, climatic change. The latest Cretaceous oxygen isotopic shift recorded at Maud Rise and other deep sea sites is similar in magnitude to large positive delta valve of 0 to 18 shifts in the middle Eocene, at the Eocene/Oligocene boundary and in the middle Miocene that marked large scale climatic transitions which ultimately lead to cryospheric development of the Antarctic. The climatic shift at the end of the Cretaceous represents one of the most significant climatic transitions recorded in the latest Phanerozoic and had a profound effect on global climate as well as oceanic circulation.

  8. Late Holocene climate change recorded in proxy records from a Bransfield Basin sediment core, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    Alex Barnard

    2014-06-01

    Full Text Available The glacimarine environment of the Antarctic Peninsula region is one of the fastest warming places on Earth today, but details of changes in the recent past remain unknown. Large distances and widespread variability separate late Holocene palaeoclimate reconstructions in this region. This study focuses on a marine sediment core collected from ca. 2000 m below sea level in the Central Bransfield Strait that serves as a key for understanding changes in this region. The core yielded a high sedimentation rate and therefore provides an exceptional high-resolution sedimentary record composed of hemipelagic sediment, with some turbidites. An age model has been created using radiocarbon dates that span the Late Holocene: 3560 cal yr BP to present. This chronostratigraphic framework was used to establish five units, which are grouped into two super-units: a lower super-unit (3560–1600 cal yr BP and an upper super-unit (1600 cal yr BP–present, based on facies descriptions, laser particle size analysis, x-ray analysis, multi-sensor core logger data, weight percentages and isotopic values of total organic carbon and nitrogen. We interpret the signal contained within the upper super-unit as an increase in surface water irradiance and/or shortening of the sea-ice season and the five units are broadly synchronous with climatic intervals across the Antarctic Peninsula region. While the general trends of regional climatic periods are represented in the Bransfield Basin core we have examined, each additional record that is obtained adds variability to the known history of the Antarctic Peninsula, rather than clarifying specific trends.

  9. Impact of Greenland and Antarctic ice sheet interactions on climate sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Goelzer, H.; Huybrechts, P. [Vrije Universiteit Brussel, Earth System Sciences and Departement Geografie, Brussels (Belgium); Loutre, M.F.; Goosse, H.; Fichefet, T. [Universite Catholique de Louvain, Georges Lemaitre Centre for Earth and Climate Research (TECLIM), Earth and Life Institute, Louvain-la-Neuve (Belgium); Mouchet, A. [Universite de Liege, Laboratoire de Physique Atmospherique et Planetaire, Liege (Belgium)

    2011-09-15

    We use the Earth system model of intermediate complexity LOVECLIM to show the effect of coupling interactive ice sheets on the climate sensitivity of the model on a millennial time scale. We compare the response to a 2 x CO{sub 2} warming scenario between fully coupled model versions including interactive Greenland and Antarctic ice sheet models and model versions with fixed ice sheets. For this purpose an ensemble of different parameter sets have been defined for LOVECLIM, covering a wide range of the model's sensitivity to greenhouse warming, while still simulating the present-day climate and the climate evolution over the last millennium within observational uncertainties. Additional freshwater fluxes from the melting ice sheets have a mitigating effect on the model's temperature response, leading to generally lower climate sensitivities of the fully coupled model versions. The mitigation is effectuated by changes in heat exchange within the ocean and at the sea-air interface, driven by freshening of the surface ocean and amplified by sea-ice-related feedbacks. The strength of the effect depends on the response of the ice sheets to the warming and on the model's climate sensitivity itself. The effect is relatively strong in model versions with higher climate sensitivity due to the relatively large polar amplification of LOVECLIM. With the ensemble approach in this study we cover a wide range of possible model responses. (orig.)

  10. Synoptic and mesoscale climate forcing on Antarctic ice shelf surface melt dynamics

    Science.gov (United States)

    Karmosky, Christopher

    Given that the polar regions, especially the Antarctic Peninsula, have experienced one of the largest temperature increases on Earth over the last few decades, an understanding of Antarctic climate has become more urgent. Ice shelves themselves are located at the intersection of the atmosphere, hydrosphere and the cryosphere---the air-ice-ocean boundary, and are sensitive to changes in any of these media. In addition to being particularly sensitive to changes in climate, ice shelves play an important role in controlling the flow of glaciers into the ocean, which has important implications for sea level changes. In a warming world, an increased understanding of how climate change is affecting Antarctic ice shelves is valuable for assessing vulnerable regions of the Antarctic that may be prone to further instability. This work focuses on determining the underlying climatic processes controlling energy and mass balance responsible for driving melting over ice shelves. A novel melt-magnitude retrieval method is presented that uses Moderate Resolution Imaging Spectroradiometer (MODIS)-derived near-IR reflectance coupled with ice surface temperature as a proxy for surface melt magnitude. This method has a higher spatial resolution than passive microwave melt detection, has the added benefit of retrieving melt magnitude rather than a binary melt occurrence or non-occurrence, but has a lower temporal resolution than either passive-microwave or microwave-scatterometry melt detection. This limitation is a result of the opacity of cloud cover to both visible and IR radiation, requiring more satellite overpasses to obtain spatially contiguous imagery. This work also examines several weather variables associated with a large-extent, long-duration surface melt event on the Ross Ice Shelf. It is shown that cloudy conditions coupled with increased sensible and latent heat flux to the surface were present during the event, and these conditions are consistent with those that induce

  11. Representation of the Antarctic circumpolar vortex mixing barrier in a Global Climate Model

    Science.gov (United States)

    Cameron, Chris; Conway, Jono; Bodeker, Greg; Renwick, James

    2017-04-01

    Dynamical processes that occur in the stratosphere between 15 and 50 km above Earth's surface can affect circulation in the troposphere and have an impact on weather and climate. The Antarctic Circumpolar Vortex (ACV) forms each winter and spring as a zone of strong stratospheric westerly winds surrounding Antarctica. The ACV presents a barrier to transport of air masses between middle and high-latitudes, and contributes to stratospheric temperatures above the polar region dropping sufficiently low in spring to allow for ozone loss. The processes controlling the permeability of the ACV, and how they are likely to respond to a changing climate and a recovering ozone hole, have not been well studied, and as a result are not well simulated in Global Climate Models, particularly in terms of sub-grid scale turbulent diffusion which is parameterized in the models. The UK Met Office Unified Model (UM) is used to examine vortex permeability using both the "New Dynamics" and the upgraded "ENDGame" dynamical cores. Results are compared against reanalysis representations of vortex permeability using the MERRA-2 and ERA-Interim reanalyses data sets, which have been shown to have superior performance in the Southern Hemisphere stratosphere when compared against NCEP-CFSR, and MERRA reanalyses. Results are expected to lead to improved representation of ACV transport process in Global Climate Models and subsequent improvements in climate modelling.

  12. Climate change and the marine ecosystem of the western Antarctic Peninsula

    Science.gov (United States)

    Clarke, Andrew; Murphy, Eugene J; Meredith, Michael P; King, John C; Peck, Lloyd S; Barnes, David K.A; Smith, Raymond C

    2006-01-01

    The Antarctic Peninsula is experiencing one of the fastest rates of regional climate change on Earth, resulting in the collapse of ice shelves, the retreat of glaciers and the exposure of new terrestrial habitat. In the nearby oceanic system, winter sea ice in the Bellingshausen and Amundsen seas has decreased in extent by 10% per decade, and shortened in seasonal duration. Surface waters have warmed by more than 1 K since the 1950s, and the Circumpolar Deep Water (CDW) of the Antarctic Circumpolar Current has also warmed. Of the changes observed in the marine ecosystem of the western Antarctic Peninsula (WAP) region to date, alterations in winter sea ice dynamics are the most likely to have had a direct impact on the marine fauna, principally through shifts in the extent and timing of habitat for ice-associated biota. Warming of seawater at depths below ca 100 m has yet to reach the levels that are biologically significant. Continued warming, or a change in the frequency of the flooding of CDW onto the WAP continental shelf may, however, induce sublethal effects that influence ecological interactions and hence food-web operation. The best evidence for recent changes in the ecosystem may come from organisms which record aspects of their population dynamics in their skeleton (such as molluscs or brachiopods) or where ecological interactions are preserved (such as in encrusting biota of hard substrata). In addition, a southwards shift of marine isotherms may induce a parallel migration of some taxa similar to that observed on land. The complexity of the Southern Ocean food web and the nonlinear nature of many interactions mean that predictions based on short-term studies of a small number of species are likely to be misleading. PMID:17405211

  13. Marine Ecosystem Response to Rapid Climate Warming on the West Antarctic Peninsula (Invited)

    Science.gov (United States)

    Ducklow, H.; Baker, K. S.; Doney, S. C.; Fraser, B.; Martinson, D. G.; Meredith, M. P.; Montes-Hugo, M. A.; Sailley, S.; Schofield, O.; Sherrell, R. M.; Stammerjohn, S. E.; Steinberg, D. K.

    2010-12-01

    The Palmer, Antarctica LTER builds on meteorological, ocean color and seabird observations since the late 1970s. It occupies annually in summer a regional-scale grid extending 700 km northward from Charcot Island to Anvers Island, and 200 km cross-shelf from the coast to the shelfbreak. In addition to routine CTD profiles and zooplankton tows throughout the grid, the observing system also includes Slocum Glider surveys and thermistor moorings. Geophysical changes include +6C atmospheric warming in winter since 1950, a 20% increase in heat content over the continental shelf since 1990, a surface ocean warming of +1C since 1950, an 83-day reduction in sea ice duration (advance 48 days later, retreat 35 days earlier) over the greater southern Bellingshausen Sea region from 1979-2007, intensification of westerly winds and differential changes in cloudiness. In response to these large changes in the regional climate, the marine ecosystem of the western Peninsula is changing at all trophic levels from diatoms to penguins. Ocean color indicates differential changes in phytoplankton stocks in response to regional decreases in sea ice cover. Surface chlorophyll has declined 89% in the north and increased 67% in the south. Antarctic krill and salps have declined and increased in our study area, respectively. Penguin diet sampling suggests changes in populations or distributions of the Antarctic Silverfish in the Anvers Island vicinity, possibly in response to ocean warming. Adélie penguins have declined 75% from 15000 to <3000 pairs at since 1975 in response to changes in food availability and increased late spring snow accumulation. Changes in pygoscelid penguin breeding populations in the Anvers Island vicinity of the West Antarctic Peninsula

  14. A model study of the effect of climate and sea-level change on the evolution of the Antarctic Ice Sheet from the Last Glacial Maximum to 2100

    NARCIS (Netherlands)

    Maris, M. N. A.; Van Wessem, J. M.; Van De Berg, W. J.; De Boer, B.; Oerlemans, J.

    2014-01-01

    Due to a scarcity of observations and its long memory of uncertain past climate, the Antarctic Ice Sheet remains a largely unknown factor in the prediction of global sea level change. As the history of the ice sheet plays a key role in its future evolution, in this study we model the Antarctic Ice

  15. Climatic changes in the Antarctic Eocene: - palaeontological, mineralogical and geochemical fossil proxies from bryozoans

    Science.gov (United States)

    Hara, Urszula

    2017-04-01

    (Bartonian in age). Contrary to that, the bryozoan fauna recognized in the upper part of the LMF (Telm7) is composed of the impoverished biota of the scarse lepraliomorphs, poorly preserved cyclostome of Iridmonoidea and Reticrescis, which are abundantly accompanied by the gadiform fish remains, penguin bones and whales. A sharp decrease in the bryozoan diversity near the contact between the Telm5 and Telm6 was connected with the climatic cooling event, which culminated at the time of deposition of the upper part of the LMF. The skeletal mineralogy along with the geochemical stable isotope studies of the bryozoans (Seymour Island, Antarctic Peninsula) help to elucidate the environmental and climatic changes connected with the Early Eocene Climatic Optimum (EECO), Middle Eocene Climatic Optimum (MECO) as well as the EOT in the stratigraphical profile of the La Meseta Formation. References Hara U. 2015. Bryozoan internal moulds from the La Meseta Formation (Eocene) of Seymour Island, Antarctic Peninsula. Polish Polar Research, vol. 36, 25-49. Hara U., Mors T., Hagstrom J. and Reguero M.A. 2017. Eocene bryozoans assemblages from the La Meseta Formation of Seymour Island, Antarctica (in review).

  16. Antarctic Ice Sheet variability across the Eocene-Oligocene boundary climate transition.

    Science.gov (United States)

    Galeotti, Simone; DeConto, Robert; Naish, Timothy; Stocchi, Paolo; Florindo, Fabio; Pagani, Mark; Barrett, Peter; Bohaty, Steven M; Lanci, Luca; Pollard, David; Sandroni, Sonia; Talarico, Franco M; Zachos, James C

    2016-04-01

    About 34 million years ago, Earth's climate cooled and an ice sheet formed on Antarctica as atmospheric carbon dioxide (CO2) fell below ~750 parts per million (ppm). Sedimentary cycles from a drill core in the western Ross Sea provide direct evidence of orbitally controlled glacial cycles between 34 million and 31 million years ago. Initially, under atmospheric CO2 levels of ≥600 ppm, a smaller Antarctic Ice Sheet (AIS), restricted to the terrestrial continent, was highly responsive to local insolation forcing. A more stable, continental-scale ice sheet calving at the coastline did not form until ~32.8 million years ago, coincident with the earliest time that atmospheric CO2 levels fell below ~600 ppm. Our results provide insight into the potential of the AIS for threshold behavior and have implications for its sensitivity to atmospheric CO2 concentrations above present-day levels. Copyright © 2016, American Association for the Advancement of Science.

  17. Antarctic Climate Change: Extreme Events Disrupt Plastic Phenotypic Response in Adélie Penguins

    Science.gov (United States)

    Lescroël, Amélie; Ballard, Grant; Grémillet, David; Authier, Matthieu; Ainley, David G.

    2014-01-01

    In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A ‘natural experiment’ brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The ‘natural experiment’ uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise. PMID:24489657

  18. Antarctic climate change: extreme events disrupt plastic phenotypic response in Adélie penguins.

    Directory of Open Access Journals (Sweden)

    Amélie Lescroël

    Full Text Available In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC on the foraging efficiency of Adélie penguins (Pygoscelis adeliae breeding in the Ross Sea. A 'natural experiment' brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The 'natural experiment' uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise.

  19. Assessing the Global Climate Response to Freshwater Forcing from the Antarctic Ice Sheet Under Future Climate Scenarios

    Science.gov (United States)

    Rogstad, S.; Condron, A.; DeConto, R.; Pollard, D.

    2017-12-01

    Observational evidence indicates that the West Antarctic Ice Sheet (WAIS) is losing mass at an accelerating rate. Impacts to global climate resulting from changing ocean circulation patterns due to increased freshwater runoff from Antarctica in the future could have significant implications for global heat transport, but to-date this topic has not been investigated using complex numerical models with realistic freshwater forcing. Here, we present results from a high resolution fully coupled ocean-atmosphere model (CESM 1.2) forced with runoff from Antarctica prescribed from a high resolution regional ice sheet-ice shelf model. Results from the regional simulations indicate a potential freshwater contribution from Antarctica of up to 1 m equivalent sea level rise by the end of the century under RCP 8.5 indicating that a substantial input of freshwater into the Southern Ocean is possible. Our high resolution global simulations were performed under IPCC future climate scenarios RCP 4.5 and 8.5. We will present results showing the impact of WAIS collapse on global ocean circulation, sea ice, air temperature, and salinity in order to assess the potential for abrupt climate change triggered by WAIS collapse.

  20. Evidence for a dynamic East Antarctic ice sheet during the mid-Miocene climate transition

    Science.gov (United States)

    Pierce, Elizabeth L.; van de Flierdt, Tina; Williams, Trevor; Hemming, Sidney R.; Cook, Carys P.; Passchier, Sandra

    2017-11-01

    The East Antarctic ice sheet underwent a major expansion during the Mid-Miocene Climate Transition, around 14 Ma, lowering sea level by ∼60 m. However, direct or indirect evidence of where changes in the ice sheet occurred is limited. Here we present new insights on timing and locations of ice sheet change from two drill sites offshore East Antarctica. IODP Site U1356, Wilkes Land, and ODP Site 1165, Prydz Bay are located adjacent to two major ice drainage areas, the Wilkes Subglacial Basin and the Lambert Graben. Ice-rafted detritus (IRD), including dropstones, was deposited in concentrations far exceeding those known in the rest of the Miocene succession at both sites between 14.1 and 13.8 Ma, indicating that large amounts of IRD-bearing icebergs were calved from independent drainage basins during this relatively short interval. At Site U1356, the IRD was delivered in distinct pulses, suggesting that the overall ice advance was punctuated by short periods of ice retreat in the Wilkes Subglacial Basin. Provenance analysis of the mid-Miocene IRD and fine-grained sediments provides additional insights on the movement of the ice margin and subglacial geology. At Site U1356, the dominant 40Ar/39Ar thermochronological age of the ice-rafted hornblende grains is 1400-1550 Ma, differing from the majority of recent IRD in the area, from which we infer an inland source area of this thermochronological age extending along the eastern part of the Adélie Craton, which forms the western side of the Wilkes Subglacial Basin. Neodymium isotopic compositions from the terrigenous fine fraction at Site U1356 imply that the ice margin periodically expanded from high ground well into the Wilkes Subglacial Basin during periods of MMCT ice growth. At Site 1165, MMCT pebble-sized IRD are sourced from both the local Lambert Graben and the distant Aurora Subglacial Basin drainage area. Together, the occurrence and provenance of the IRD and glacially-eroded sediment at these two marine

  1. The potential macroalgae habitat shifts in an Antarctic Peninsula fjord due to climate change

    Science.gov (United States)

    Jerosch, Kerstin; Scharf, Frauke; Deregibus, Dolores; Campana, Gabriela; Zacher, Katharina; Hass, Christian; Quartino, Liliana; Abele, Doris

    2016-04-01

    The Western Antarctic Peninsula (WAP) region is one of the most rapidly warming on earth since the last 50 yr. The WAP glaciers currently contribute one third of the melt water to global sea level rise. Climate warming is supposed to induce important changes in polar ecosystems, from microbial communities to apex predators' levels. Macroalgae are the main biomass producers in Potter Cove located at King George Island, the biggest island of the South Shetland Arc. They are sensitive to climate change factors such as suspended particulate matter (SPM). Macroalgae presence and absence data were used to test SDMs suitability and, simultaneously, to assess the environmental response of macroalgae as well as to model four scenarios of distribution shifts by varying SPM conditions due to climate change. Species distribution models (SDM) predict species occurrence based on statistical relationships with environmental conditions. The R-package 'biomod2' which includes 10 different SDM techniques and 10 different evaluation methods was used in this study. According to the averaged evaluation scores of Relative Operating Characteristics (ROC) and True scale statistics (TSS) by models, those methods based on a multitude of decision trees such as Random Forest and Classification Tree Analysis, reached the highest predictive power followed by generalized boosted models (GBM) and maximum-entropy approaches (Maxent). The final ensemble model (EM) used 135 of 200 calculated models (TSS > 0.7) and identified hard substrate and SPM as the most influencing parameters followed by distance to glacier, total organic carbon (TOC), bathymetry and slope. The modeled current status of macroalgae distribution results in only 18.25% of earlier estimated areas populated by macroalgae in Potter Cove. The climate change scenarios show an invasive reaction of the macroalgae in case of less SPM and a retreat of the macroalgae in case of higher assumed SPM values.

  2. Potential climate change effects on the habitat of antarctic krill in the weddell quadrant of the southern ocean.

    Science.gov (United States)

    Hill, Simeon L; Phillips, Tony; Atkinson, Angus

    2013-01-01

    Antarctic krill is a cold water species, an increasingly important fishery resource and a major prey item for many fish, birds and mammals in the Southern Ocean. The fishery and the summer foraging sites of many of these predators are concentrated between 0° and 90°W. Parts of this quadrant have experienced recent localised sea surface warming of up to 0.2°C per decade, and projections suggest that further widespread warming of 0.27° to 1.08°C will occur by the late 21(st) century. We assessed the potential influence of this projected warming on Antarctic krill habitat with a statistical model that links growth to temperature and chlorophyll concentration. The results divide the quadrant into two zones: a band around the Antarctic Circumpolar Current in which habitat quality is particularly vulnerable to warming, and a southern area which is relatively insensitive. Our analysis suggests that the direct effects of warming could reduce the area of growth habitat by up to 20%. The reduction in growth habitat within the range of predators, such as Antarctic fur seals, that forage from breeding sites on South Georgia could be up to 55%, and the habitat's ability to support Antarctic krill biomass production within this range could be reduced by up to 68%. Sensitivity analysis suggests that the effects of a 50% change in summer chlorophyll concentration could be more significant than the direct effects of warming. A reduction in primary production could lead to further habitat degradation but, even if chlorophyll increased by 50%, projected warming would still cause some degradation of the habitat accessible to predators. While there is considerable uncertainty in these projections, they suggest that future climate change could have a significant negative effect on Antarctic krill growth habitat and, consequently, on Southern Ocean biodiversity and ecosystem services.

  3. Potential climate change effects on the habitat of antarctic krill in the weddell quadrant of the southern ocean.

    Directory of Open Access Journals (Sweden)

    Simeon L Hill

    Full Text Available Antarctic krill is a cold water species, an increasingly important fishery resource and a major prey item for many fish, birds and mammals in the Southern Ocean. The fishery and the summer foraging sites of many of these predators are concentrated between 0° and 90°W. Parts of this quadrant have experienced recent localised sea surface warming of up to 0.2°C per decade, and projections suggest that further widespread warming of 0.27° to 1.08°C will occur by the late 21(st century. We assessed the potential influence of this projected warming on Antarctic krill habitat with a statistical model that links growth to temperature and chlorophyll concentration. The results divide the quadrant into two zones: a band around the Antarctic Circumpolar Current in which habitat quality is particularly vulnerable to warming, and a southern area which is relatively insensitive. Our analysis suggests that the direct effects of warming could reduce the area of growth habitat by up to 20%. The reduction in growth habitat within the range of predators, such as Antarctic fur seals, that forage from breeding sites on South Georgia could be up to 55%, and the habitat's ability to support Antarctic krill biomass production within this range could be reduced by up to 68%. Sensitivity analysis suggests that the effects of a 50% change in summer chlorophyll concentration could be more significant than the direct effects of warming. A reduction in primary production could lead to further habitat degradation but, even if chlorophyll increased by 50%, projected warming would still cause some degradation of the habitat accessible to predators. While there is considerable uncertainty in these projections, they suggest that future climate change could have a significant negative effect on Antarctic krill growth habitat and, consequently, on Southern Ocean biodiversity and ecosystem services.

  4. Consistent biases in Antarctic sea ice concentration simulated by climate models

    Science.gov (United States)

    Roach, Lettie A.; Dean, Samuel M.; Renwick, James A.

    2018-01-01

    The simulation of Antarctic sea ice in global climate models often does not agree with observations. In this study, we examine the compactness of sea ice, as well as the regional distribution of sea ice concentration, in climate models from the latest Coupled Model Intercomparison Project (CMIP5) and in satellite observations. We find substantial differences in concentration values between different sets of satellite observations, particularly at high concentrations, requiring careful treatment when comparing to models. As a fraction of total sea ice extent, models simulate too much loose, low-concentration sea ice cover throughout the year, and too little compact, high-concentration cover in the summer. In spite of the differences in physics between models, these tendencies are broadly consistent across the population of 40 CMIP5 simulations, a result not previously highlighted. Separating models with and without an explicit lateral melt term, we find that inclusion of lateral melt may account for overestimation of low-concentration cover. Targeted model experiments with a coupled ocean-sea ice model show that choice of constant floe diameter in the lateral melt scheme can also impact representation of loose ice. This suggests that current sea ice thermodynamics contribute to the inadequate simulation of the low-concentration regime in many models.

  5. The influence of continental shelf bathymetry on Antarctic Ice Sheet response to climate forcing

    Science.gov (United States)

    Bart, Phil; Mullally, Dan; Golledge, Nick

    2017-04-01

    We investigated whether shelf-depth changes would have influenced Antarctic Ice Sheet (AIS) response to climate forcing using the Parallel Ice Sheet Model (PISM). The simulations confirm that this would have indeed been the case. For the last-glacial-cycle (LGC) type forcing we prescribed, a modern-like polar AIS surrounded by shallow and intermediate bathymetries experiences rapid grounding-line advance early during the transition from interglacial to glacial forcing. This is in contrast to our baseline simulation of AIS response on the currently overdeepened bathymetry, which showed the expected gradual advance of grounding lines to the same climatic forcing. In the simulation, the more-positive mass balance for the shallower bathymetry is primarily a result of significantly lower calving fluxes from smaller-area ice shelves. On the basis of these results, we suggest that shelf bathymetry is an important boundary condition that should be considered when reconstructing AIS behavior since at least the middle Miocene. We note that caution should be used when applying these concepts because the particular way in which AIS mass balance is altered by shelf depth depends on how the changes in accumulation and ablation at the marine terminations combine with accumulation and ablation on land.

  6. Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

    Science.gov (United States)

    Li, Feng; Vikhliaev, Yury V.; Newman, Paul A.; Pawson, Steven; Perlwitz, Judith; Waugh, Darryn W.; Douglass, Anne R.

    2016-01-01

    Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model's climatology is evaluated using observations and reanalysis. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

  7. The sensitivity of dimethyl sulfide production to simulated climate change in the Eastern Antarctic Southern Ocean

    International Nuclear Information System (INIS)

    Gabric, Albert J.; Cropp, Roger; Marchant, Harvey

    2003-01-01

    Dimethyl sulfide (DMS) is a radiatively active trace gas produced by enzymatic cleavage of its precursor compound, dimethyl sulfoniopropionate (DMSP), which is released by marine phytoplankton in the upper ocean. Once ventilated to the atmosphere, DMS is oxidised to form non-sea-salt sulfate and methane sulfonate (MSA) aerosols, which are a major source of cloud condensation nuclei (CCN) in remote marine air and may thus play a role in climate regulation. Here we simulate the change in DMS flux in the Eastern Antarctic ocean from 1960-2086, corresponding to equivalent CO 2 tripling relative to pre-industrial levels. Calibration to contemporary climate conditions was carried out using a genetic algorithm to fit the model to surface chlorophyll from the 4-yr SeaWiFs satellite archive and surface DMS from an existing global database. Following the methodology used previously in the Subantarctic Southern Ocean, we then simulated DMS emissions under enhanced greenhouse conditions by forcing the DMS model with output from a coupled atmospheric-ocean general circulation model (GCM). The GCM was run in transient mode under the IPCC/IS92a radiative forcing scenario. By 2086, the change simulated in annual integrated DMS flux is around 20% in ice-free waters, with a greater increase of 45% in the seasonal ice zone (SIZ). Interestingly, the large increase in flux in the SIZ is not due to higher in situ production but mainly because of a loss of ice cover during summer-autumn and an increase in sea-to-air ventilation of DMS. These proportional changes in areal mean flux (25%) are much higher than previously estimated for the Subantarctic Southern Ocean (5%), and point to the possibility of a significant DMS-climate feedback at high Southern latitudes. Due to the nexus between ice cover and food-web structure, the potential for ecological community shifts under enhanced greenhouse conditions is high, and the implications for DMS production are discussed

  8. Antarctic sea ice control on ocean circulation in present and glacial climates.

    Science.gov (United States)

    Ferrari, Raffaele; Jansen, Malte F; Adkins, Jess F; Burke, Andrea; Stewart, Andrew L; Thompson, Andrew F

    2014-06-17

    In the modern climate, the ocean below 2 km is mainly filled by waters sinking into the abyss around Antarctica and in the North Atlantic. Paleoproxies indicate that waters of North Atlantic origin were instead absent below 2 km at the Last Glacial Maximum, resulting in an expansion of the volume occupied by Antarctic origin waters. In this study we show that this rearrangement of deep water masses is dynamically linked to the expansion of summer sea ice around Antarctica. A simple theory further suggests that these deep waters only came to the surface under sea ice, which insulated them from atmospheric forcing, and were weakly mixed with overlying waters, thus being able to store carbon for long times. This unappreciated link between the expansion of sea ice and the appearance of a voluminous and insulated water mass may help quantify the ocean's role in regulating atmospheric carbon dioxide on glacial-interglacial timescales. Previous studies pointed to many independent changes in ocean physics to account for the observed swings in atmospheric carbon dioxide. Here it is shown that many of these changes are dynamically linked and therefore must co-occur.

  9. Oceanic an climatic consequences of a sudden large-scale West Antarctic Ice Sheet collapse

    Science.gov (United States)

    Scarff, Katie; Green, Mattias; Schmittner, Andreas

    2015-04-01

    Atmospheric warming is progressing to the point where the West Antarctic Ice Sheet (WAIS) will experience an elevated rate of discharge. The current discharge rate of WAIS is around 0.005Sv, but this rate will most likely accelerate over this century. The input of freshwater, in the form of ice, may have a profound effect on oceanic circulation systems, including potentially reducing the formation of deep water in the Southern Ocean and thus triggering or enhancing the bipolar seesaw. Using UVic - an intermediate complexity ocean-climate model - we investigate how various hosing rates from the WAIS will impact of the present and future ocean circulation and climate. These scenarios range from observed hosing rates (~0.005Sv) being applied for 100 years, to a total collapse of the WAIS over the next 100 years (the equivalent to a0.7Sv hosing). We show that even the present day observed rates can have a significant impact on the ocean and atmospheric temperatures, and that the bipolar seesaw may indeed be enhanced by the Southern Ocean hosing. Consequently, there is a speed-up of the Meridional Overturning Circulation (MOC) early on during the hosing, which leads to a warming over the North Atlantic, and a subsequent reduction in the MOC on centennial scales. The larger hosing cases show more dramatic effects with near-complete shutdowns of the MOC during the hosing. Furthermore, global warming scenarios based on the IPCC "business as usual" scenario show that the atmospheric warming will change the response of the ocean to Southern Ocean hosing and that the warming will dominate the perturbation. The potential feedback between changes in the ocean stratification in the scenarios and tidally driven abyssal mixing via tidal conversion is also explored.

  10. A synthesis of bentho-pelagic coupling on the Antarctic shelf: Food banks, ecosystem inertia and global climate change

    Science.gov (United States)

    Smith, Craig R.; Mincks, Sarah; DeMaster, David J.

    2006-04-01

    -annual) trends in water-column production. Bentho-pelagic coupling clearly will be altered by Antarctic climate change as patterns of sea-ice cover and water-column recycling vary. However, the nature of such climate-driven changes will be very difficult to predict without further studies of Antarctic benthic ecosystem response to (1) inter-annual variability in export flux, and (2) latitudinal gradients in duration of sea-ice cover and benthic ecosystem function.

  11. Assessment of Gravity Recovery and Climate Experiment (GRACE) temporal signature over the upper Zambezi

    NARCIS (Netherlands)

    Winsemius, H.C.; Savenije, H.H.G.; Van de Giesen, N.C.; Van den Hurk, B.J.J.M.; Zapreeva, E.A.; Klees, R.

    2006-01-01

    The temporal signature of terrestrial storage changes inferred from the Gravity Recovery and Climate Experiment (GRACE) has been assessed by comparison with outputs from a calibrated hydrological model (lumped elementary watershed (LEW)) of the upper Zambezi and surroundings and an inspection of the

  12. Role of CO2-forced Antarctic shelf freshening on local shelf warming in an eddying global climate model

    Science.gov (United States)

    Goddard, P.; Dufour, C.; Yin, J.; Griffies, S. M.; Winton, M.

    2017-12-01

    Ocean warming near the Antarctic ice shelves has critical implications for future ice sheet mass loss and global sea level rise. A global climate model (GFDL CM2.6) with an eddying ocean is used to quantify and better understand the mechanisms contributing to ocean warming on the Antarctic continental shelf in an idealized 2xCO2 experiment. The results indicate that the simulated shelf region warming varies in magnitude at different locations. Relatively large warm anomalies occur both in the upper 100 m and at depth, which are controlled by different mechanisms. Here, we focus on the deep shelf warming and its relationship to shelf freshening. Under CO2-forcing, enhanced runoff from Antarctica, more regional precipitation, and reduction of sea ice contribute to the shelf freshening. The freshening increases the lateral density gradient of the Antarctic Slope Front, which can limit along-isopycnal onshore transport of heat from the Circumpolar Deep Water across the shelf break. Thus, the magnitude and location of the freshening anomalies govern the magnitude and location of onshore heat transport and deep warm anomalies. Additionally, the freshening increases vertical stratification on the shelf. The enhanced stratification reduces vertical mixing of heat associated with diffusion and gravitational instabilities, further contributing to the build-up of temperature anomalies at depth. Freshening is a crucial driver of the magnitude and location of the warming; however, other drivers influence the warming such as CO2-forced weakening of the easterly wind stress and associated shoaling of isotherms. Understanding the relative role of freshening in the inhomogeneous ocean warming of the Antarctic continental shelf would lead to better projections of future ice sheet mass loss, especially near the most vulnerable calving fronts.

  13. Volcanoes and climate: Krakatoa's signature persists in the ocean.

    Science.gov (United States)

    Gleckler, P J; Wigley, T M L; Santer, B D; Gregory, J M; Achutarao, K; Taylor, K E

    2006-02-09

    We have analysed a suite of 12 state-of-the-art climate models and show that ocean warming and sea-level rise in the twentieth century were substantially reduced by the colossal eruption in 1883 of the volcano Krakatoa in the Sunda strait, Indonesia. Volcanically induced cooling of the ocean surface penetrated into deeper layers, where it persisted for decades after the event. This remarkable effect on oceanic thermal structure is longer lasting than has previously been suspected and is sufficient to offset a large fraction of ocean warming and sea-level rise caused by anthropogenic influences.

  14. IPAB Antarctic Drifting Buoy Data

    Data.gov (United States)

    National Aeronautics and Space Administration — The World Climate Research Programme (WCRP) International Programme for Antarctic Buoys (IPAB), through participating research organizations in various countries,...

  15. Unveiling signatures of interdecadal climate changes by Hilbert analysis

    Science.gov (United States)

    Zappalà, Dario; Barreiro, Marcelo; Masoller, Cristina

    2017-04-01

    A recent study demonstrated that, in a class of networks of oscillators, the optimal network reconstruction from dynamics is obtained when the similarity analysis is performed not on the original dynamical time series, but on transformed series obtained by Hilbert transform. [1] That motivated us to use Hilbert transform to study another kind of (in a broad sense) "oscillating" series, such as the series of temperature. Actually, we found that Hilbert analysis of SAT (Surface Air Temperature) time series uncovers meaningful information about climate and is therefore a promising tool for the study of other climatological variables. [2] In this work we analysed a large dataset of SAT series, performing Hilbert transform and further analysis with the goal of finding signs of climate change during the analysed period. We used the publicly available ERA-Interim dataset, containing reanalysis data. [3] In particular, we worked on daily SAT time series, from year 1979 to 2015, in 16380 points arranged over a regular grid on the Earth surface. From each SAT time series we calculate the anomaly series and also, by using the Hilbert transform, we calculate the instantaneous amplitude and instantaneous frequency series. Our first approach is to calculate the relative variation: the difference between the average value on the last 10 years and the average value on the first 10 years, divided by the average value over all the analysed period. We did this calculations on our transformed series: frequency and amplitude, both with average values and standard deviation values. Furthermore, to have a comparison with an already known analysis methods, we did these same calculations on the anomaly series. We plotted these results as maps, where the colour of each site indicates the value of its relative variation. Finally, to gain insight in the interpretation of our results over real SAT data, we generated synthetic sinusoidal series with various levels of additive noise. By applying

  16. 21st Century Trends in Antarctic Temperature and Polar Stratospheric Cloud (PSC) Area in the GEOS Chemistry-Climate Model

    Science.gov (United States)

    Hurwitz, M. M.; Newman, P. A.

    2010-01-01

    This study examines trends in Antarctic temperature and APSC, a temperature proxy for the area of polar stratospheric clouds, in an ensemble of Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) simulations of the 21st century. A selection of greenhouse gas, ozone-depleting substance, and sea surface temperature scenarios is used to test the trend sensitivity to these parameters. One scenario is used to compare temperature trends in two versions of the GEOS CCM. An extended austral winter season is examined in detail. In May, June, and July, the expected future increase in CO2-related radiative cooling drives temperature trends in the Antarctic lower stratosphere. At 50 hPa, a 1.3 K cooling is expected between 2000 and 2100. Ozone levels increase, despite this robust cooling signal and the consequent increase in APSC, suggesting the enhancement of stratospheric transport in future. In the lower stratosphere, the choice of climate change scenarios does not affect the magnitude of the early winter cooling. Midwinter temperature trends are generally small. In October, APSC trends have the same sign as the prescribed halogen trends. That is, there are negative APSC trends in "grealistic future" simulations, where halogen loading decreases in accordance with the Montreal Protocol and CO2 continues to increase. In these simulations, the speed of ozone recovery is not influenced by either the choice of sea surface temperature and greenhouse gas scenarios or by the model version.

  17. Precambrian cyclic rhythmites: solar-climatic or tidal signatures?

    International Nuclear Information System (INIS)

    Williams, G.E.

    1990-01-01

    For more than 60 years geologists have sought evidence of solar-climatic cyclicity in rhythmically laminated sedimentary rocks, but claims in general have not been persuasive. Three Precambrian rhythmite sequences in Australia that comprise varve-like laminae recently have received attention, however, as their conspicuous cycles of ca. 10-14 and/or 20-25 laminae have been ascribed a sunspot-cycle origin. They are the 2500 Ma old Weeli Wolli Formation, the 1750 Ma old Wollogorang Formation and the 650 Ma old Elatina Formation. New observations for the Weeli Wolli Formation, a siliceous banded iron-formation, suggest a cycle period exceeding the 23 microband couplets proposed by Trendall, casting doubt on the solar interpretation. The Weeli Wolli cyclicity may record Earth-tidal rhythms that modulated the discharge and composition of silica- and iron-bearing fumarolic waters. The structure of the cycles of silty dolomite and mudstone in the Wollogorang Formation does not support a sunspot-cycle origin, and a tidal control on sedimentation should be considered. The Elatina sequence of cyclic sandstone and siltstone laminae displays several empirical similarities to the sunspot series. The discovery of thicker, more complex lamina-cycles in the correlative Reynella Siltstone has, however, caused reappraisal of the solar interpretation of the Elatina rhythmites. The Elatina series may encode unique information on lunar orbital periods and the Earth's palaeorotation: the data indicate ca. 30.5 days per lunar month, 13.1 lunar months and ca. 400 days per year, and lunar apsides and lunar nodal cycles of 9.7 and ca. 19.5 years respectively some 650 Ma ago. (author)

  18. Modeling climate change impact in hospitality sector, using building resources consumption signature

    Science.gov (United States)

    Pinto, Armando; Bernardino, Mariana; Silva Santos, António; Pimpão Silva, Álvaro; Espírito Santo, Fátima

    2016-04-01

    Hotels are one of building types that consumes more energy and water per person and are vulnerable to climate change because in the occurrence of extreme events (heat waves, water stress) same failures could compromise the hotel services (comfort) and increase energy cost or compromise the landscape and amenities due to water use restrictions. Climate impact assessments and the development of adaptation strategies require the knowledge about critical climatic variables and also the behaviour of building. To study the risk and vulnerability of buildings and hotels to climate change regarding resources consumption (energy and water), previous studies used building energy modelling simulation (BEMS) tools to study the variation in energy and water consumption. In general, the climate change impact in building is evaluated studying the energy and water demand of the building for future climate scenarios. But, hotels are complex buildings, quite different from each other and assumption done in simplified BEMS aren't calibrated and usually neglect some important hotel features leading to projected estimates that do not usually match hotel sector understanding and practice. Taking account all uncertainties, the use of building signature (statistical method) could be helpful to assess, in a more clear way, the impact of Climate Change in the hospitality sector and using a broad sample. Statistical analysis of the global energy consumption obtained from bills shows that the energy consumption may be predicted within 90% confidence interval only with the outdoor temperature. In this article a simplified methodology is presented and applied to identify the climate change impact in hospitality sector using the building energy and water signature. This methodology is applied to sixteen hotels (nine in Lisbon and seven in Algarve) with four and five stars rating. The results show that is expect an increase in water and electricity consumption (manly due to the increase in

  19. Antarctic glaciations under Pliocene climate conditions from numerical modeling and compilation of local field-based reconstructions

    Science.gov (United States)

    Bernales, Jorge; Rogozhina, Irina; Greve, Ralf

    2014-05-01

    The mid-Pliocene (3.15 to 2.85 million years before present) is the most recent period in Earth's history when temperatures and CO2 concentrations were likely sustainedly higher than pre-industrial values. Furthermore, the positions of the continents and their sea-land distributions had already reached their present configuration, sharing some similarities with today's patterns of ocean circulation and vegetation distributions. Although significant differences exist -such as a peak sea level that could have been 22 ± 10 m higher than it is today and sea surface temperatures particularly warmer at higher latitudes, mid-Pliocene has been identified as an ideal interval for studying the climate system under conditions similar to those projected for the end of this century. Among the sources of uncertainty in the projections, the response of the Antarctic ice sheet (AIS) to warmer-than-today conditions seems to play a central role. Therefore, a better understanding of AIS's behavior during periods like the mid-Pliocene will provide valuable information that could help improve future predictions. For this purpose, we have compiled a wide range of local field-based reconstructions of the ice-sheet margin from Pliocene sediments (with the inclusions of organic matters such as, for instance, diatoms or palynoflora, or ice rafted debris), geochemical records, volcanic ashes and rocks, and geomorphology, and designed numerical experiments of the AIS dynamics during the mid-Pliocene warm period using the large-scale polythermal ice sheet-shelf model SICOPOLIS (Greve, 1997 [1]; Sato and Greve, 2012 [2]). The model is run with a horizontal resolution of 40 × 40 km by the climatology obtained from the PlioMIP Atmosphere Ocean Global Circulation Model experiments (Dolan et al., 2012 [3]). Parameters of the AIS model (e.g. ice calving, sub-ice shelf and surface ice melt, basal sliding, etc.) have initially been estimated using ice-sheet simulations driven by the present

  20. Geomorphic signature of an Antarctic palaeo-ice stream: implications for understanding subglacial processes and grounding line retreat

    Science.gov (United States)

    Livingstone, S. J.; Jamieson, S.; Vieli, A.; O'Cofaigh, C.; Stokes, C. R.; Hillenbrand, C.

    2010-12-01

    The ability to capture the complex spatial and temporal variability exhibited by ice streams in Antarctica and Greenland at short (decadal) time-scales, remains one of the key challenges in numerical modelling and underlies current uncertainties with predicting future contributions of ice sheets to sea-level rise. This has made ice streams a major focus for current glaciological research, particularly with regard to the processes occurring at the ice-bed interface. Such studies unfortunately, only provide a ‘snap-shot’ of the life-cycle of an ice stream, limited to the last few decades, and so there is a need for complementary investigations of former zones of fast flow in palaeo-ice sheets. The ability to observe directly the former beds of palaeo-ice streams has allowed important spatial and temporal information to be obtained on the processes that occurred at the ice-bed interface and on ice dynamics associated with the evolution of palaeo-ice streams. We present new glacial geomorphological evidence from a marine palaeo-ice stream in Marguerite Bay, Antarctic Peninsula (Ó Cofaigh et al. 2002, 2005). The landform assemblage of this palaeo-ice stream system has been derived from the mapping of over 16,000 glacial landforms from high-resolution multibeam swath-bathymetry and input into a GIS database. Analysis of the spatial distribution and geomorphic relationships between landforms and landform assemblages has revealed a complex basal régime, while the overall geomorphic imprint, constrained by radiocarbon dates, has been used to reconstruct the retreat style and history of the palaeo-ice stream. Mapping of relict subglacial meltwater channels has revealed an intricate hydrological system characterised by multiple network types (cf. Anderson & Oakes-Fretwell, 2008) that are strongly dependent on the underlying substrate and which show progressive organisation seaward. Grounding zone wedges (GZWs), formed by the subglacial transport and then deposition of

  1. The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing.

    Science.gov (United States)

    Marshall, John; Armour, Kyle C; Scott, Jeffery R; Kostov, Yavor; Hausmann, Ute; Ferreira, David; Shepherd, Theodore G; Bitz, Cecilia M

    2014-07-13

    In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around 'climate response functions' (CRFs), i.e. the response of the climate to 'step' changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate.

  2. Antarctic science

    Science.gov (United States)

    Summerhayes, Colin

    Once upon a time, dinosaurs roamed Antarctica and swam in its seas. Since then, life evolved as the climate cooled into the ice ages. Life will no doubt continue to evolve there as the globe now warms. But nowadays, humans are having a profound and direct effect on life in Antarctica, the sub-Antarctic islands, and the surrounding Southern Ocean, which are being invaded by a wide range of alien species including microbes, algae, fungi, bryophytes, land plants, invertebrates, fish, birds, and mammals.

  3. A review of Tertiary climate changes in southern South America and the Antarctic Peninsula. Part 2: continental conditions

    Science.gov (United States)

    Le Roux, J. P.

    2012-03-01

    Climate changes in southern South America and the Antarctic Peninsula during the Tertiary show a strong correlation with ocean warming and cooling events, which are in turn related to tectonic processes. During periods of accelerated sea-floor spreading and mid-ocean ridge activity, sea-levels rose so that parts of the continents were flooded and forests were destroyed. However, this was balanced by the large-scale release of CO2 during volcanic outgassing and carbonate precipitation on the continental shelves, which caused rising air temperatures and the poleward expansion of (sub)tropical and temperate forests. Cooling episodes generally caused an increase in the north-south thermal gradient because of an equatorward shift in climate belts, so that the Westerly Winds intensified and brought higher rainfall to the lower latitudes. An increase in wind-blown dust caused temperatures to drop further by reflecting sunlight back into space. The rising Andes Range had a marked influence on climate patterns. Up to the middle Miocene it was still low enough to allow summer rainfall to reach central and north-central Chile, but after about 14 Ma it rose rapidly and effectively blocked the spill-over of moisture from the Atlantic Ocean and Amazon Basin. At this time, the cold Humboldt Current was also established, which together with the Andes helped to create the "Arid Diagonal" of southern South America stretching from the Atacama Desert to the dry steppes of Patagonia. This caused the withdrawal of subtropical forests to south-central Chile and the expansion of sclerophytic vegetation to central Chile. However, at the same time it intercepted more rain from the northeast, causing the effect of the South American monsoon to intensify in northwestern Argentina and southern Bolivia, where forest communities presently occur. In Patagonia, glaciation started as early as 10.5 Ma, but by 7 Ma had become a prominent feature of the landscape and continued apparently

  4. Stable water isotopes of precipitation and firn cores from the northern Antarctic Peninsula region as a proxy for climate reconstruction

    Directory of Open Access Journals (Sweden)

    F. Fernandoy

    2012-03-01

    Full Text Available In order to investigate the climate variability in the northern Antarctic Peninsula region, this paper focuses on the relationship between stable isotope content of precipitation and firn, and main meteorological variables (air temperature, relative humidity, sea surface temperature, and sea ice extent. Between 2008 and 2010, we collected precipitation samples and retrieved firn cores from several key sites in this region. We conclude that the deuterium excess oscillation represents a robust indicator of the meteorological variability on a seasonal to sub-seasonal scale. Low absolute deuterium excess values and the synchronous variation of both deuterium excess and air temperature imply that the evaporation of moisture occurs in the adjacent Southern Ocean. The δ18O-air temperature relationship is complicated and significant only at a (multiseasonal scale. Backward trajectory calculations show that air-parcels arriving at the region during precipitation events predominantly originate at the South Pacific Ocean and Bellingshausen Sea. These investigations will be used as a calibration for ongoing and future research in the area, suggesting that appropriate locations for future ice core research are located above 600 m a.s.l. We selected the Plateau Laclavere, Antarctic Peninsula as the most promising site for a deeper drilling campaign.

  5. Leaf and floral heating in cold climates: do sub-Antarctic megaherbs resemble tropical alpine giants?

    Directory of Open Access Journals (Sweden)

    Lorna Little

    2016-08-01

    Full Text Available High latitude and altitude floras are characterized by low-statured, small, wind-pollinated plants, which mainly reproduce by self-pollination or asexual reproduction. However, at odds with this are some sub-Antarctic islands that have plant species with giant growth forms and large, brightly coloured flowers which require insect visitation for pollination. The size, colour and shape of the inflorescences and leaves of these megaherbs suggest thermal benefits similar to giant tropical alpine plants of equatorial Africa, South America and Hawaii. We evaluated whether heating occurs in sub-Antarctic megaherbs, and to what extent it is related to environmental variables. We measured leaf and inflorescence temperature in six sub-Antarctic megaherb species on Campbell Island, latitude 52.3°S, New Zealand Biological Region. Using thermal imaging techniques, in combination with measurement of solar radiation, ambient air temperature, wind speed, wind chill and humidity, we assessed environmental influences on leaf and floral heating. We found that leaf and inflorescence temperatures of all megaherbs were higher than simultaneously measured ambient temperatures. Greatest heating was seen in Pleurophyllum speciosum, with observed leaves 9°C higher, and inflorescences nearly 11°C higher, than ambient temperature. Heating was highly correlated with brief, unpredictable periods of solar radiation, and occurred most rapidly in species with hairy, corrugated leaves and darkly pigmented, densely packed inflorescences. This is the first evidence that floral and leaf heating occurs in sub-Antarctic megaherbs, and suggests that leaf hairiness, flower colour and shape could provide thermal benefits like those seen in tropical alpine megaherbs.

  6. Orbital and millennial Antarctic climate variability over the past 800,000 years

    DEFF Research Database (Denmark)

    Jouzel, J.; Masson-Delmotte, V.; Cattani, O.

    2007-01-01

    water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We...... suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records. Udgivelsesdato: 10.08...

  7. Climate Change Impacts in the sub-Antarctic Islands Technical Report N.2 of ONERC; Impacts du changement climatique dans les iles subantarctiques. Rapport Technique N.2 de l'ONERC

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    Difficult to apprehend as a whole, the polar regions constitute the Arctic to the North, an ocean surrounded by emerged lands, and the Antarctic to the South, a continent bordered by the Austral Ocean where a belt of sub Antarctic islands lies. Climate change impacts on sub Antarctic islands are varied, direct and indirect: glacier retreat, more favourable conditions for introduced species, marine biodiversity modification, etc. This report discusses the French, British, Australian, South African and New Zealand sub Antarctic islands, the climatic evolutions and the resulting impacts, focused especially on biodiversity. The Observatoire National sur les Effets du Rechauffement Climatique and the International Polar Foundation have been joined in this endeavour by the French polar institute Paul-Emile Victor, the administration of the French Southern and Antarctic Lands (TAAF in French) and the International Union for the Conservation of Nature. (authors)

  8. Biological Interactions and Simulated Climate Change Modulates the Ecophysiological Performance of Colobanthus quitensis in the Antarctic Ecosystem.

    Directory of Open Access Journals (Sweden)

    Cristian Torres-Díaz

    Full Text Available Most climate and environmental change models predict significant increases in temperature and precipitation by the end of the 21st Century, for which the current functional output of certain symbioses may also be altered. In this context we address the following questions: 1 How the expected changes in abiotic factors (temperature, and water differentially affect the ecophysiological performance of the plant Colobanthus quitensis? and 2 Will this environmental change indirectly affect C. quitensis photochemical performance and biomass accumulation by modifying its association with fungal endophytes? Plants of C. quitensis from King George Island in the South Shetland archipelago (62°09' S, and Lagotellerie Island in the Antarctic Peninsula (65°53' S were put under simulated abiotic conditions in growth chambers following predictive models of global climate change (GCC. The indirect effect of GCC on the interaction between C. quitensis and fungal endophytes was assessed in a field experiment carried out in the Antarctica, in which we eliminated endophytes under contemporary conditions and applied experimental watering to simulate increased precipitation input. We measured four proxies of plant performance. First, we found that warming (+W significantly increased plant performance, however its effect tended to be less than watering (+W and combined warming and watering (+T°+W. Second, the presence of fungal endophytes improved plant performance, and its effect was significantly decreased under experimental watering. Our results indicate that both biotic and abiotic factors affect ecophysiological performance, and the directions of these influences will change with climate change. Our findings provide valuable information that will help to predict future population spread and evolution through using ecological niche models under different climatic scenarios.

  9. Biological Interactions and Simulated Climate Change Modulates the Ecophysiological Performance of Colobanthus quitensis in the Antarctic Ecosystem

    Science.gov (United States)

    Torres-Díaz, Cristian; Gallardo-Cerda, Jorge; Lavin, Paris; Oses, Rómulo; Carrasco-Urra, Fernando; Atala, Cristian; Acuña-Rodríguez, Ian S.; Convey, Peter; Molina-Montenegro, Marco A.

    2016-01-01

    Most climate and environmental change models predict significant increases in temperature and precipitation by the end of the 21st Century, for which the current functional output of certain symbioses may also be altered. In this context we address the following questions: 1) How the expected changes in abiotic factors (temperature, and water) differentially affect the ecophysiological performance of the plant Colobanthus quitensis? and 2) Will this environmental change indirectly affect C. quitensis photochemical performance and biomass accumulation by modifying its association with fungal endophytes? Plants of C. quitensis from King George Island in the South Shetland archipelago (62°09′ S), and Lagotellerie Island in the Antarctic Peninsula (65°53′ S) were put under simulated abiotic conditions in growth chambers following predictive models of global climate change (GCC). The indirect effect of GCC on the interaction between C. quitensis and fungal endophytes was assessed in a field experiment carried out in the Antarctica, in which we eliminated endophytes under contemporary conditions and applied experimental watering to simulate increased precipitation input. We measured four proxies of plant performance. First, we found that warming (+W) significantly increased plant performance, however its effect tended to be less than watering (+W) and combined warming and watering (+T°+W). Second, the presence of fungal endophytes improved plant performance, and its effect was significantly decreased under experimental watering. Our results indicate that both biotic and abiotic factors affect ecophysiological performance, and the directions of these influences will change with climate change. Our findings provide valuable information that will help to predict future population spread and evolution through using ecological niche models under different climatic scenarios. PMID:27776181

  10. Climate links and recent extremes in antarctic sea ice, high-latitude cyclones, Southern Annular Mode and ENSO

    Science.gov (United States)

    Pezza, Alexandre Bernardes; Rashid, Harun A.; Simmonds, Ian

    2012-01-01

    In this article, we study the climate link between the Southern Annular Mode (SAM) and the southern sea-ice extent (SIE), and discuss the possible role of stationary waves and synoptic eddies in establishing this link. In doing so, we have used a combination of techniques involving spatial correlations of SIE, eddy streamfunction and wind anomalies, and statistics of high-latitude cyclone strength. It is suggested that stationary waves may be amplified by eddy anomalies associated with high latitude cyclones, resulting in more sea ice when the SAM is in its positive phase for most, but not all, longitudes. A similar association is observed during ENSO (La Niña years). Although this synergy in the SAM/ENSO response may partially reflect preferential areas for wave amplification around Antarctica, the short extent of the climate records does not allow for a definite causality connection to be established with SIE. Stronger polar cyclones are observed over the areas where the stationary waves are amplified. These deeper cyclones will break up and export ice equatorward more efficiently, but the near-coastal regions are cold enough to allow for a rapid re-freeze of the resulting ice break-up. We speculate that if global warming continues this same effect could help reverse the current (positive) Antarctic SIE trends once the ice gets thinner, similarly to what has been observed in the Northern Hemisphere.

  11. Moderate climate signature in cranial anatomy of late holocene human populations from Southern South America.

    Science.gov (United States)

    Paula Menéndez, Lumila

    2018-02-01

    influence of climate on skull shape has probably been the result of directional selection. This study supports that, although cranial vault is the cranial structure more associated to mean annual temperature, the impact of climate signature on morphology decreases when populations from extreme cold environments are excluded from the analysis. Additionally, it shows that the extent of the geographical scales analyzed, as well as differential sampling may lead to different results regarding the role of ecological factors and evolutionary processes on cranial morphology. © 2017 Wiley Periodicals, Inc.

  12. IPAB Antarctic Drifting Buoy Data, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The World Climate Research Programme (WCRP) International Programme for Antarctic Buoys (IPAB), through participating research organizations in various countries,...

  13. Near-surface climate and surface energy budget of Larsen C ice shelf, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    P. Kuipers Munneke

    2012-03-01

    Full Text Available Data collected by two automatic weather stations (AWS on the Larsen C ice shelf, Antarctica, between 22 January 2009 and 1 February 2011 are analyzed and used as input for a model that computes the surface energy budget (SEB, which includes melt energy. The two AWSs are separated by about 70 km in the north–south direction, and both the near-surface meteorology and the SEB show similarities, although small differences in all components (most notably the melt flux can be seen. The impact of subsurface absorption of shortwave radiation on melt and snow temperature is significant, and discussed. In winter, longwave cooling of the surface is entirely compensated by a downward turbulent transport of sensible heat. In summer, the positive net radiative flux is compensated by melt, and quite frequently by upward turbulent diffusion of heat and moisture, leading to sublimation and weak convection over the ice shelf. The month of November 2010 is highlighted, when strong westerly flow over the Antarctic Peninsula led to a dry and warm föhn wind over the ice shelf, resulting in warm and sunny conditions. Under these conditions the increase in shortwave and sensible heat fluxes is larger than the decrease of net longwave and latent heat fluxes, providing energy for significant melt.

  14. The influence of the Calbuco eruption on the 2015 Antarctic ozone hole in a fully coupled chemistry-climate model

    Science.gov (United States)

    Ivy, Diane J.; Solomon, Susan; Kinnison, Doug; Mills, Michael J.; Schmidt, Anja; Neely, Ryan R.

    2017-03-01

    Recent research has demonstrated that the concentrations of anthropogenic halocarbons have decreased in response to the worldwide phaseout of ozone depleting substances. Yet in 2015 the Antarctic ozone hole reached a historical record daily average size in October. Model simulations with specified dynamics and temperatures based on a reanalysis suggested that the record size was likely due to the eruption of Calbuco but did not allow for fully coupled dynamical or thermal feedbacks. We present simulations of the impact of the 2015 Calbuco eruption on the stratosphere using the Whole Atmosphere Community Climate Model with interactive dynamics and temperatures. Comparisons of the interactive and specified dynamics simulations indicate that chemical ozone depletion due to volcanic aerosols played a key role in establishing the record-sized ozone hole of October 2015. The analysis of an ensemble of interactive simulations with and without volcanic aerosols suggests that the forced response to the eruption of Calbuco was an increase in the size of the ozone hole by 4.5 × 106 km2.

  15. Signals from the south; humpback whales carry messages of Antarctic sea-ice ecosystem variability.

    Science.gov (United States)

    Bengtson Nash, Susan M; Castrillon, Juliana; Eisenmann, Pascale; Fry, Brian; Shuker, Jon D; Cropp, Roger A; Dawson, Amanda; Bignert, Anders; Bohlin-Nizzetto, Pernilla; Waugh, Courtney A; Polkinghorne, Bradley J; Dalle Luche, Greta; McLagan, David

    2018-04-01

    Southern hemisphere humpback whales (Megaptera novaeangliae) rely on summer prey abundance of Antarctic krill (Euphausia superba) to fuel one of the longest-known mammalian migrations on the planet. It is hypothesized that this species, already adapted to endure metabolic extremes, will be one of the first Antarctic consumers to show measurable physiological change in response to fluctuating prey availability in a changing climate; and as such, a powerful sentinel candidate for the Antarctic sea-ice ecosystem. Here, we targeted the sentinel parameters of humpback whale adiposity and diet, using novel, as well as established, chemical and biochemical markers, and assembled a time trend spanning 8 years. We show the synchronous, inter-annual oscillation of two measures of humpback whale adiposity with Southern Ocean environmental variables and climate indices. Furthermore, bulk stable isotope signatures provide clear indication of dietary compensation strategies, or a lower trophic level isotopic change, following years indicated as leaner years for the whales. The observed synchronicity of humpback whale adiposity and dietary markers, with climate patterns in the Southern Ocean, lends strength to the role of humpback whales as powerful Antarctic sea-ice ecosystem sentinels. The work carries significant potential to reform current ecosystem surveillance in the Antarctic region. © 2017 John Wiley & Sons Ltd.

  16. Ocean processes at the Antarctic continental slope.

    Science.gov (United States)

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

  17. Dating Antarctic ice sheet collapse: Proposing a molecular genetic approach

    Science.gov (United States)

    Strugnell, Jan M.; Pedro, Joel B.; Wilson, Nerida G.

    2018-01-01

    Sea levels at the end of this century are projected to be 0.26-0.98 m higher than today. The upper end of this range, and even higher estimates, cannot be ruled out because of major uncertainties in the dynamic response of polar ice sheets to a warming climate. Here, we propose an ecological genetics approach that can provide insight into the past stability and configuration of the West Antarctic Ice Sheet (WAIS). We propose independent testing of the hypothesis that a trans-Antarctic seaway occurred at the last interglacial. Examination of the genomic signatures of bottom-dwelling marine species using the latest methods can provide an independent window into the integrity of the WAIS more than 100,000 years ago. Periods of connectivity facilitated by trans-Antarctic seaways could be revealed by dating coalescent events recorded in DNA. These methods allow alternative scenarios to be tested against a fit to genomic data. Ideal candidate taxa for this work would need to possess a circumpolar distribution, a benthic habitat, and some level of genetic structure indicated by phylogeographical investigation. The purpose of this perspective piece is to set out an ecological genetics method to help resolve when the West Antarctic Ice Shelf last collapsed.

  18. Carbon Sinks in a Changing Climate: Relative Buoyancy and Sinking Potentials of Various Antarctic Phytoplankton and Ice Algae

    Science.gov (United States)

    Nirmel, S.; Selz, V.

    2016-12-01

    Polar phytoplankton play instrumental roles in global biogeochemical cycles, sometimes serving as massive carbon sinks via the biological pump. In addition to phytoplankton, sea ice supports a significant amount of ice algae, the essential primary producers for the ecosystem in winter and early spring. While sea ice habitat declines on regional scales, the fate of sea ice algae post-ice melt remains relatively unknown, despite its importance in understanding how the biological pump might be affected by sea ice loss. Through a series of settling column experiments on the icebreaker Nathaniel B. Palmer, we aimed to address the question: What controls the fate of the carbon-rich ice algae across the Western Antarctic Peninsula (WAP) during ice melt? We focused on whether species composition affects the sinking potential of ice algal communities. Using FlowCAM imagery, we classified samples collected from the buoyant, neutral, and negatively buoyant portions of the settling columns into genus-level taxonomic classes. We used image parameters and geometric shape equations to calculate the biovolume of each taxonomic group. We further explored relationships between taxa-specific sinking potentials, environmental parameters (temperature and nutrients), and physiological properties of associated algal communities (as described by Fast Rate Repetition fluorometry). Results indicate that colonial Phaeocystis antarctica tends to dominate lower regions of the settling column. Moreover, we observe strong correlations between geographic location and both nutrients and phytoplankton physiology. We found that these three factors are indeed related to taxa-specific buoyancy and sinking indices. An understanding of these relationships sheds more light on the role P. antarctica (a carbon-rich bloom-forming genus) plays in the biological pump; higher sinking rates suggest greater carbon export to depth, while lower sinking rates increase the likelihood of carbon being respired back

  19. New insights into the use of stable water isotopes at the northern Antarctic Peninsula as a tool for regional climate studies

    Science.gov (United States)

    Fernandoy, Francisco; Tetzner, Dieter; Meyer, Hanno; Gacitúa, Guisella; Hoffmann, Kirstin; Falk, Ulrike; Lambert, Fabrice; MacDonell, Shelley

    2018-03-01

    Due to recent atmospheric and oceanic warming, the Antarctic Peninsula is one of the most challenging regions of Antarctica to understand in terms of both local- and regional-scale climate signals. Steep topography and a lack of long-term and in situ meteorological observations complicate the extrapolation of existing climate models to the sub-regional scale. Therefore, new techniques must be developed to better understand processes operating in the region. Isotope signals are traditionally related mainly to atmospheric conditions, but a detailed analysis of individual components can give new insight into oceanic and atmospheric processes. This paper aims to use new isotopic records collected from snow and firn cores in conjunction with existing meteorological and oceanic datasets to determine changes at the climatic scale in the northern extent of the Antarctic Peninsula. In particular, a discernible effect of sea ice cover on local temperatures and the expression of climatic modes, especially the Southern Annular Mode (SAM), is demonstrated. In years with a large sea ice extension in winter (negative SAM anomaly), an inversion layer in the lower troposphere develops at the coastal zone. Therefore, an isotope-temperature relationship (δ-T) valid for all periods cannot be obtained, and instead the δ-T depends on the seasonal variability of oceanic conditions. Comparatively, transitional seasons (autumn and spring) have a consistent isotope-temperature gradient of +0.69 ‰ °C-1. As shown by firn core analysis, the near-surface temperature in the northern-most portion of the Antarctic Peninsula shows a decreasing trend (-0.33 °C year-1) between 2008 and 2014. In addition, the deuterium excess (dexcess) is demonstrated to be a reliable indicator of seasonal oceanic conditions, and therefore suitable to improve a firn age model based on seasonal dexcess variability. The annual accumulation rate in this region is highly variable, ranging between 1060 and 2470 kg m

  20. The Mendel Formation: Evidence for Late Miocene climatic cyclicity at the northern tip of the Antarctic Peninsula

    Czech Academy of Sciences Publication Activity Database

    Nývlt, D.; Košler, J.; Mlčoch, B.; Mixa, P.; Lisá, Lenka; Bubík, M.; Hendriks, B. W. H.

    2011-01-01

    Roč. 299, 1/2 (2011), s. 363-384 ISSN 0031-0182 Institutional research plan: CEZ:AV0Z30130516 Keywords : Mendel Formation * Late Miocene * chmate * Antarctic Peninsula Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.392, year: 2011

  1. Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes Geoquímica de tefras de volcanes Cuaternarios de la Península Antártica

    Directory of Open Access Journals (Sweden)

    Stefan Kraus

    2013-01-01

    Full Text Available In the northern Antarctic Peninsula area, at least 12 Late Plelstocene-Holocene volcanic centers could be potential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoes using major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. The volcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguish between volcanic centers located on the eastern (Larsen Rift and those situated on the western side (Bransfield Rift of the Antarctic Peninsula. In addition, the Sr/Nb ratio (for samples with SiO2 En la parte norte de la Península Antártica existen, por lo menos, 12 centros volcánicos del Pleistoceno Tardío-Holoceno que podrían representar las fuentes de horizontes de tefra reconocidos en la región. Se reportan aquí análisis químicos de 10 de estos volcanes, que incluyen análisis de elementos mayores, trazas, tierras raras y composición isotópica de 95 muestras de tefra u otros productos eruptivos. Los volcanes tienen, en su mayoría, composición basáltica a basáltico-andesítica. Las razones Nb/Y resultan útiles para distinguir entre centros volcánicos ubicados al lado oriental (Larsen Rift de aquellos ubicados al lado occidental (Bransfield Rift de la Península Antártica. Adicionalmente, las razones Sr/Nb (para muestras con SiO2 <63 wt%, Sr/Y, Ba/La, Zr/Hf y Th/Nb sirven para caracterizar los productos generados por cada centro volcánico. Análisis de microsonda en vidrio muestran que las rocas estudiadas tienen bajos contenidos de K2O, y que vidrios de rocas provenientes de volcanes ubicados en el rift de Bransfield son ricos en SiO2, mientras que las de volcanes del rift de Larsen tienden hacía contenidos elevados de álcalis. Se propone un algoritmo para la identificación del volcán de origen de un horizonte de tefra cualquiera, basado en las distintivas

  2. Glacier History of the Northern Antarctic Peninsula Region Since the End of the Last Ice Age and Implications for Southern Hemisphere Westerly-Climate Changes

    Science.gov (United States)

    Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Peltier, C.; Southon, J. R.; Lepper, K. E.; Winckler, G.

    2017-12-01

    For the area around James Ross Island, we present new cosmogenic 10Be exposure ages on glacial deposits, and 14C ages on associated fossil materials. These data allow us to reconstruct in detail when and how the Antarctic Peninsula Ice Sheet retreated around the Island as the last Ice Age ended, and afterward when local land-based glaciers fluctuated. Similar to other studies, we found widespread deglaciation during the earliest Holocene, with fjords and bays becoming ice free between about 11,000 and 8,000 years ago. After 7,000 years ago, neoglacial type advances initiated. Then, both expansions and ice free periods occurred from the middle to late Holocene. We compare the new glacier record to those in southern Patagonia, which is on the other side of the Drake Passage, and published Southern Ocean marine records, in order to infer past middle to high latitude changes in the Southern Hemisphere Westerlies. Widespread warmth in the earliest Holocene, to the north and south of the Drake Passage, led to small glacier systems in Patagonia and wide-ranging glacier recession around the northern Antarctic Peninsula. We infer that this early Holocene period of overall glacier recession - from Patagonia to the northern Peninsula - was caused by a persistent far-southerly setting of the westerlies and accompanying warm climates. Subsequently, during the middle Holocene renewed glacier expansions occurred on both sides of the Drake Passage, which reflects that the Westerlies and associated colder climate systems were generally more equatorward. From the middle to late Holocene, glacier expansions and ice free periods (and likely related ice shelf behavior) document how the Westerlies and associated higher-latitude climate systems varied.

  3. The influence of the Calbuco eruption on the 2015 Antarctic ozone hole in a fully coupled chemistry-climate model

    OpenAIRE

    Ivy, D; Solomon, S; Kinnison, D; Mills, M; Schmidt, A; Neely III, RR

    2017-01-01

    Recent research has demonstrated that the concentrations of anthropogenic halocarbons have decreased in response to the worldwide phaseout of ozone depleting substances. Yet in 2015 the Antarctic ozone hole reached a historical record daily average size in October. Model simulations with specified dynamics and temperatures based on a reanalysis suggested that the record size was likely due to the eruption of Calbuco but did not allow for fully coupled dynamical or thermal feedbacks. We presen...

  4. Precipitation Modeling over the Greenland and Antarctic Ice Sheets and the Relationship to the Surface Mass Balance and Climate

    Science.gov (United States)

    Bromwich, David H.; Chen, Qui-Shi

    2005-01-01

    Atmospheric numerical simulation and dynamic retrieval method with atmospheric numerical analyses are used to assess the spatial and temporal variability of Antarctic precipitation for the last two decades. First, the Polar MM5 has been run over Antarctica to study the Antarctic precipitation. With a horizontal resolution of 60km, the Polar MM5 has been run for the period of July 1996 through June 1999 in a series of short-term forecasts from initial and boundary conditions provided by the ECMWF operational analyses. In comparison with climatological maps, the major features of the spatial distribution of Antarctic precipitation are well captured by the Polar MM5. Drift snow effects on redistribution of surface accumulation over Antarctica are also assessed with surface wind fields from Polar MM5 in this study. There are complex divergence and convergence patterns of drift snow transport over Antarctica, especially along the coast. It is found that areas with large drift snow transport convergence and divergence are located around escarpment areas where there is large katabatic wind acceleration. In addition, areas with large snow transport divergence are generally accompanied by areas with large snow transport convergence nearby, indicating that drift snow transport is of local importance for the redistribution of the snowfall

  5. Using Oxygen and Carbon Isotopic Signatures in Order to Infer Climatic and Dietary Information in Roman Edessa, Greece

    Science.gov (United States)

    Michael, Dimitra-Ermioni; Dotsika, Elissavet

    2017-12-01

    Even though many isotopic studies have been conducted on ancient populations from Greece for the purpose of dietary reconstruction; mostly through carbon and nitrogen isotopic signals of bone collagen, less attention has been given to the utility of apatite signatures (oxygen and carbon) as dietary and palaeoenvironmental tools. Moreover, until recently the isotopic signal of tooth enamel for both the purposes of environmental and dietary reconstructions has been rarely assessed in ancient Greek societies. Therefore, the present study aims to provide with novel isotopic information regarding Edessa; a town in Northern Greece, during the Roman period. The current study primarily aims to explore the possible differentiation between the present climatic conditions in Edessa in relation to those occurring at the Roman period. Secondly, this study aims to reveal the significant utility of enamel isotopic signatures (carbon and oxygen) in palaeoenvironmental and palaeodietary studies regarding ancient human remains. The isotopic analyses have been conducted at the Stable Isotope and Radiocarbon Unit of INN, NCSR “Demokritos”. The population of Roman Edessa (2nd-4th c. AD) consists of 22 individuals, providing with 19 bone samples and 16 enamel ones. The mean enamel oxygen value is at -7.7 ±1.1 %0, the bone apatite mean oxygen value at -9.2 ±1.9 %0, and finally the mean carbon enamel value is at -11.7 ±1.2 %0. Oxygen values probably indicate that Edessa had a cooler climate during the Roman times in relation to present conditions, even though more research should be carried out in order to be more certain. In addition, the possible existence of non-local individuals has been revealed through the oxygen teeth enamel-bone apatite spacing. Finally, the carbon enamel signature has pointed out possible differentiations between the adult and the juvenile diet. Based on Edessa’s findings, the stated study strongly encourages the enamel oxygen and carbon isotopic signals

  6. Historical Arctic and Antarctic Surface Observational Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This product consists of meteorological data from 105 Arctic weather stations and 137 Antarctic stations, extracted from the National Climatic Data Center (NCDC)'s...

  7. Signatures of diversifying selection at EST-SSR loci and association with climate in natural Eucalyptus populations.

    Science.gov (United States)

    Bradbury, Donna; Smithson, Ann; Krauss, Siegfried L

    2013-10-01

    Understanding the environmental parameters that drive adaptation among populations is important in predicting how species may respond to global climatic changes and how gene pools might be managed to conserve adaptive genetic diversity. Here, we used Bayesian FST outlier tests and allele-climate association analyses to reveal two Eucalyptus EST-SSR loci as strong candidates for diversifying selection in natural populations of a southwestern Australian forest tree, Eucalyptus gomphocephala (Myrtaceae). The Eucalyptus homolog of a CONSTANS-like gene was an FST outlier, and allelic variation showed significant latitudinal clinal associations with annual and winter solar radiation, potential evaporation, summer precipitation and aridity. A second FST outlier locus, homologous to quinone oxidoreductase, was significantly associated with measures of temperature range, high summer temperature and summer solar radiation, with important implications for predicting the effect of temperature on natural populations in the context of climate change. We complemented these data with investigations into neutral population genetic structure and diversity throughout the species range. This study provides an investigation into selection signatures at gene-homologous EST-SSRs in natural Eucalyptus populations, and contributes to our understanding of the relationship between climate and adaptive genetic variation, informing the conservation of both putatively neutral and adaptive components of genetic diversity. © 2013 John Wiley & Sons Ltd.

  8. Signatures of global warming and regional climate shift in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Roshin, R.P.; Narvekar, J.; DineshKumar, P.K.; Vivekanandan, E.

    productivity that is tightly-coupled with the climate-shift. 59 Climate Change and Aquatic Ecosystems- (2010) Climate Change and Aquatic Ecosystems- (2010) 60 61 Climate Change and Aquatic Ecosystems- (2010) Figure 4. Basin-averaged chlorophyll pigment... in the Arabian Sea. They also showed that the warming of winter after 1995 has affected the wheat production of India. In this paper we use the data presented by Prasanna Kumar et al. (2009) and analyze their results in the context of increased marine...

  9. Eddy dynamics in the Southern Ocean: How does the interaction of the Antarctic Circumpolar Current with sea-bed topography influence the surface mixed layer and hence the carbon-climate feedback processes?

    CSIR Research Space (South Africa)

    Kobo, N

    2012-10-01

    Full Text Available Ocean: How does the interaction of the Antarctic Circumpolar Current with sea-bed topography infl uence the surface mixed layer and hence the carbon-climate feedback processes N KOBO, S HERBETTE, PMS MONTEIRO AND C REASON CSIR Natural Resources... encounters topography the generation of mesoscale features (such as eddies) can result. These mesoscale features influence water mass formation, meridional heat transport and carbon dioxide uptake[2]. This project investigates the how. METHODS...

  10. Prominent Midlatitude Circulation Signature in High Asia's Surface Climate During Monsoon

    Science.gov (United States)

    Mölg, Thomas; Maussion, Fabien; Collier, Emily; Chiang, John C. H.; Scherer, Dieter

    2017-12-01

    High Asia has experienced strong environmental changes in recent decades, as evident in records of glaciers, lakes, tree rings, and vegetation. The multiscale understanding of the climatic drivers, however, is still incomplete. In particular, few systematic assessments have evaluated to what degree, if at all, the midlatitude westerly circulation modifies local surface climates in the reach of the Indian Summer Monsoon. This paper shows that a southward shift of the upper-tropospheric westerlies contributes significantly to climate variability in the core monsoon season (July-September) by two prominent dipole patterns at the surface: cooling in the west of High Asia contrasts with warming in the east, while moist anomalies in the east and northwest occur with drying along the southwestern margins. Circulation anomalies help to understand the dipoles and coincide with shifts in both the westerly wave train and the South Asian High, which imprint on air mass advection and local energy budgets. The relation of the variabilities to a well-established index of midlatitude climate dynamics allows future research on climate proxies to include a fresh hypothesis for the interpretation of environmental changes.

  11. South American Rivers: the Signature of Climate Changes in Hydrological Inflows

    Science.gov (United States)

    Pinto, L.; Szczupak, J.; Macedo, L. H.

    2004-12-01

    Hydrological inflows impact the whole society, since water is one of the fundamental sources of life. Even though, science has not yet achieved a complete understanding of river dynamics; characterizing and predicting water inflows is still a challenge. Our work intends to offer a new approach to river flow modeling: instead of analyzing local measurements and trying to find a relationship between them, we searched for a possible connection between inflows and global climate variables and trends. This paper describes the first results of our research through a case study with one of the more important South American rivers: Parana, which flows into Itaipu energy plant (one of the largest plants in the world). It is possible to show an impressive correlation (near 1.0) between the water inflow and some climatic variables around the world (circling the globe: Pacific, Indic, Atlantic oceans). These correlations, evaluated for different time lags, are then used to build a propagation model able to predict the river flow months ahead. Finally, it is shown that the "1970 gap" (one of the most interesting climatic characteristics) is found both in the global climatic variables and in the river flow. It is possible to identify a break-point that divides the water flow history into two very distinct quasi-stationary phenomena: pre- and post-70. Curiously, precipitation variables in the same basin do not present such a clear gap. The answer, still under research, may lie in a combination of human actions (use of the land) and changes in soil physical characteristics.

  12. Regional climatic and North Atlantic Oscillation signatures in West Virginia red cedar over the past millennium

    Science.gov (United States)

    D'Arrigo, Rosanne; Anchukaitis, Kevin J.; Buckley, Brendan; Cook, Ed; Wilson, Rob

    2012-03-01

    We describe a millennial length (~ 1500-yr) tree-ring chronology developed from West Virginia (WVA), USA red cedar (Juniperus virginiana) ring widths that is significantly correlated with local to regional temperature and precipitation for the region. Using ensemble methods of tree-ring standardization, above average ring widths are indicated for the period between ~ 1000 and 1300 CE, the approximate time of the Medieval Climate Anomaly (MCA), the most recent major warm episode prior to the modern era. The chronology then transitions to more negative overall growth persisting through much of the subsequent period known as the Little Ice Age (LIA). While WVA cedar growth levels during the MCA are broadly similar to the 20th century mean, the most positive values during the MCA are associated with RCS-standardized chronologies, which pseudoproxy tests reveal are likely biased artificially positive, warranting further investigation. This cedar record is significantly correlated with the NAO, due to the tendency for warmer, wetter conditions to occur in the eastern-central USA during the NAO's positive phase. These types of conditions are inferred for this cedar chronology during the MCA period, during which NAO reconstructions suggest a persistently-positive NAO state.

  13. Antarctic Tephra Database (AntT)

    Science.gov (United States)

    Kurbatov, A.; Dunbar, N. W.; Iverson, N. A.; Gerbi, C. C.; Yates, M. G.; Kalteyer, D.; McIntosh, W. C.

    2014-12-01

    Modern paleoclimate research is heavily dependent on establishing accurate timing related to rapid shifts in Earth's climate system. The ability to correlate these events at local, and ideally at the intercontinental scales, allows assessment, for example, of phasing or changes in atmospheric circulation. Tephra-producing volcanic eruptions are geologically instantaneous events that are largely independent of climate. We have developed a tephrochronological framework for paleoclimate research in Antarctic in a user friendly, freely accessible online Antarctic tephra (AntT) database (http://cci.um.maine.edu/AntT/). Information about volcanic events, including physical and geochemical characteristics of volcanic products collected from multiple data sources, are integrated into the AntT database.The AntT project establishes a new centralized data repository for Antarctic tephrochronology, which is needed for precise correlation of records between Antarctic ice cores (e.g. WAIS Divide, RICE, Talos Dome, ITASE) and global paleoclimate archives. The AntT will help climatologists, paleoclimatologists, atmospheric chemists, geochemists, climate modelers synchronize paleoclimate archives using volcanic products that establishing timing of climate events in different geographic areas, climate-forcing mechanisms, natural threshold levels in the climate system. All these disciplines will benefit from accurate reconstructions of the temporal and spatial distribution of past rapid climate change events in continental, atmospheric, marine and polar realms. Research is funded by NSF grants: ANT-1142007 and 1142069.

  14. Observed trends of soil fauna in the Antarctic Dry Valleys: early signs of shifts predicted under climate change.

    Science.gov (United States)

    Andriuzzi, W S; Adams, B J; Barrett, J E; Virginia, R A; Wall, D H

    2018-02-01

    Long-term observations of ecological communities are necessary for generating and testing predictions of ecosystem responses to climate change. We investigated temporal trends and spatial patterns of soil fauna along similar environmental gradients in three sites of the McMurdo Dry Valleys, Antarctica, spanning two distinct climatic phases: a decadal cooling trend from the early 1990s through the austral summer of February 2001, followed by a shift to the current trend of warming summers and more frequent discrete warming events. After February 2001, we observed a decline in the dominant species (the nematode Scottnema lindsayae) and increased abundance and expanded distribution of less common taxa (rotifers, tardigrades, and other nematode species). Such diverging responses have resulted in slightly greater evenness and spatial homogeneity of taxa. However, total abundance of soil fauna appears to be declining, as positive trends of the less common species so far have not compensated for the declining numbers of the dominant species. Interannual variation in the proportion of juveniles in the dominant species was consistent across sites, whereas trends in abundance varied more. Structural equation modeling supports the hypothesis that the observed biological trends arose from dissimilar responses by dominant and less common species to pulses of water availability resulting from enhanced ice melt. No direct effects of mean summer temperature were found, but there is evidence of indirect effects via its weak but significant positive relationship with soil moisture. Our findings show that combining an understanding of species responses to environmental change with long-term observations in the field can provide a context for validating and refining predictions of ecological trends in the abundance and diversity of soil fauna. © 2018 by the Ecological Society of America.

  15. 76 FR 39905 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978 (Pub. L. 95-541)

    Science.gov (United States)

    2011-07-07

    ... Antarctic Conservation Act of 1978 (Pub. L. 95-541), as amended by the Antarctic Science, Tourism and..., Switzerland, and the USA) project examining the effects of climate warming on seasonal thawing, permafrost...

  16. Mid-Burdigalian Paratethyan alkenone record reveals link between orbital forcing, Antarctic ice-sheet dynamics and European climate at the verge to Miocene Climate Optimum.

    Science.gov (United States)

    Grunert, Patrick; Tzanova, Alexandrina; Harzhauser, Mathias; Piller, Werner E

    2014-12-01

    The Early Ottnangian Cooling (EOC), a distinct cold-spell in European climate at ~ 18 Ma preceding the Miocene Climate Optimum, is frequently reported in Paratethys records; however, the duration, magnitude, and underlying causes are poorly understood. A new palaeoclimatic data-set provides unexpected insights into this event. U K' 37 -based sea-surface temperatures > 24 °C between ~ 18.1 and 17.7 Myrs substantially exceed existing estimates, and indicate a significantly warmer European climate than previously assumed for this usually poorly recovered time interval. The EOC is expressed as an average drop of 2-3 °C in Paratethyan water temperatures between ~ 18.1 and 17.8 Myrs with two distinct cold snaps at ~ 17.86 Ma and ~ 17.81 Ma. The short duration of the EOC excludes Tethyan Seaway closure as its underlying cause, although the enhanced palaeoclimatic sensitivity of the Paratethys due to this palaeogeographic configuration potentially contributed to the magnitude of SST deterioration during the EOC. The revealed palaeoclimatic pattern shows a strong correlation with isotope event Mi-1b in deep-sea δ 18 O records, and we propose a tight palaeoclimatic link between the Southern Ocean and the Paratethys/Mediterranean realm as an alternative hypothesis. The interplay of modulations in the long-term (~ 400 kyrs) and short-term (~ 100 kyrs) eccentricity cycles most likely acted as pacemaker of this palaeoclimatic interaction.

  17. Historical Arctic and Antarctic Surface Observational Data, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This product consists of meteorological data from 105 Arctic weather stations and 137 Antarctic stations, extracted from the National Climatic Data Center (NCDC)'s...

  18. Antarctic stratospheric ozone and seasonal predictability over southern Africa

    CSIR Research Space (South Africa)

    Engelbrecht, FA

    2015-09-01

    Full Text Available The impact of time-varying Antarctic stratospheric ozone on southern African summer climate variability is explored through atmospheric global circulation model (AGCM) sensitivity experiments. A control experiment following the design...

  19. Eight glacial cycles from an Antarctic ice core

    NARCIS (Netherlands)

    Oerlemans, J.

    2004-01-01

    The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not

  20. Environmental change and Antarctic seabird populations.

    Science.gov (United States)

    Croxall, J P; Trathan, P N; Murphy, E J

    2002-08-30

    Recent changes in Antarctic seabird populations may reflect direct and indirect responses to regional climate change. The best long-term data for high-latitude Antarctic seabirds (Adélie and Emperor penguins and snow petrels) indicate that winter sea-ice has a profound influence. However, some effects are inconsistent between species and areas, some in opposite directions at different stages of breeding and life cycles, and others remain paradoxical. The combination of recent harvest driven changes and those caused by global warming may produce rapid shifts rather than gradual changes.

  1. A shift in the biogenic silica of sediment in the Larsen B continental shelf, off the Eastern Antarctic Peninsula, resulting from climate change.

    Directory of Open Access Journals (Sweden)

    Elisabet Sañé

    Full Text Available In 2002, section B of the Larsen ice shelf, off of the Eastern Antarctic Peninsula, collapsed and created the opportunity to study whether the changes at the sea surface left evidence in the sedimentary record. Biogenic silica is major constituent of Antarctic marine sediment, and its presence in the sediment column is associated with diatom production in the euphotic zone. The abundance of diatom valves and the number of sponge spicules in the biogenic silica was analyzed to determine how the origin of the biogenic silica in the upper layers of the sediment column responded to recent environmental changes. Diatom valves were present only in the upper 2 cm of sediment, which roughly corresponds to the period after the collapse of the ice shelf. In contrast, sponge spicules, a more robust form of biogenic silica, were also found below the upper 2 cm layer of the sediment column. Our results indicate that in this region most of the biogenic silica in the sedimentary record originated from sponge spicules rather than diatoms during the time when the sea surface was covered by the Larsen ice shelf. Since the collapse of the ice shelf, the development of phytoplankton blooms and the consequent influx of diatom debris to the seabed have shifted the biogenic silica record to one dominated by diatom debris, as occurs in most of the Antarctic marine sediment. This shift provides further evidence of the anthropogenic changes to the benthic habitats of the Antarctic and will improve the interpretation of the sedimentary record in Polar Regions where these events occur.

  2. Meteorological observatory for Antarctic data collection

    International Nuclear Information System (INIS)

    Grigioni, P.; De Silvestri, L.

    1996-01-01

    In the last years, a great number of automatic weather stations was installed in Antarctica, with the aim to examine closely the weather and climate of this region and to improve the coverage of measuring points on the Antarctic surface. In 1987 the Italian Antarctic Project started to set up a meteorological network, in an area not completely covered by other countries. Some of the activities performed by the meteorological observatory, concerning technical functions such as maintenance of the AWS's and the execution of radio soundings, or relating to scientific purposes such as validation and elaboration of collected data, are exposed. Finally, some climatological considerations on the thermal behaviour of the Antarctic troposphere such as 'coreless winter', and on the wind field, including katabatic flows in North Victoria Land are described

  3. Reconsidering connectivity in the sub-Antarctic.

    Science.gov (United States)

    Moon, Katherine L; Chown, Steven L; Fraser, Ceridwen I

    2017-11-01

    Extreme and remote environments provide useful settings to test ideas about the ecological and evolutionary drivers of biological diversity. In the sub-Antarctic, isolation by geographic, geological and glaciological processes has long been thought to underpin patterns in the region's terrestrial and marine diversity. Molecular studies using increasingly high-resolution data are, however, challenging this perspective, demonstrating that many taxa disperse among distant sub-Antarctic landmasses. Here, we reconsider connectivity in the sub-Antarctic region, identifying which taxa are relatively isolated, which are well connected, and the scales across which this connectivity occurs in both terrestrial and marine systems. Although many organisms show evidence of occasional long-distance, trans-oceanic dispersal, these events are often insufficient to maintain gene flow across the region. Species that do show evidence of connectivity across large distances include both active dispersers and more sedentary species. Overall, connectivity patterns in the sub-Antarctic at intra- and inter-island scales are highly complex, influenced by life-history traits and local dynamics such as relative dispersal capacity and propagule pressure, natal philopatry, feeding associations, the extent of human exploitation, past climate cycles, contemporary climate, and physical barriers to movement. An increasing use of molecular data - particularly genomic data sets that can reveal fine-scale patterns - and more effective international collaboration and communication that facilitates integration of data from across the sub-Antarctic, are providing fresh insights into the processes driving patterns of diversity in the region. These insights offer a platform for assessing the ways in which changing dispersal mechanisms, such as through increasing human activity and changes to wind and ocean circulation, may alter sub-Antarctic biodiversity patterns in the future. © 2017 Cambridge

  4. Climate-vegetation-soil interactions and long-term hydrologic partitioning: signatures of catchment co-evolution

    Directory of Open Access Journals (Sweden)

    P. A. Troch

    2013-06-01

    Full Text Available Budyko (1974 postulated that long-term catchment water balance is controlled to first order by the available water and energy. This leads to the interesting question of how do landscape characteristics (soils, geology, vegetation and climate properties (precipitation, potential evaporation, number of wet and dry days interact at the catchment scale to produce such a simple and predictable outcome of hydrological partitioning? Here we use a physically-based hydrologic model separately parameterized in 12 US catchments across a climate gradient to decouple the impact of climate and landscape properties to gain insight into the role of climate-vegetation-soil interactions in long-term hydrologic partitioning. The 12 catchment models (with different paramterizations are subjected to the 12 different climate forcings, resulting in 144 10 yr model simulations. The results are analyzed per catchment (one catchment model subjected to 12 climates and per climate (one climate filtered by 12 different model parameterization, and compared to water balance predictions based on Budyko's hypothesis (E/P = ϕ (Ep/P; E: evaporation, P: precipitation, Ep: potential evaporation. We find significant anti-correlation between average deviations of the evaporation index (E/P computed per catchment vs. per climate, compared to that predicted by Budyko. Catchments that on average produce more E/P have developed in climates that on average produce less E/P, when compared to Budyko's prediction. Water and energy seasonality could not explain these observations, confirming previous results reported by Potter et al. (2005. Next, we analyze which model (i.e., landscape filter characteristics explain the catchment's tendency to produce more or less E/P. We find that the time scale that controls subsurface storage release explains the observed trend. This time scale combines several geomorphologic and hydraulic soil properties. Catchments with relatively longer

  5. Isotopic signature of Tian-Shan mountain soils as a record of climatic changes of the Late Pleistocene and Holocene

    Science.gov (United States)

    Kovaleva, N. O.

    2018-01-01

    Specific features of the polygenetic mountain soils of the Tian-Shan (Kyrgystan) are due to the action of present-day and relict soil processes that vary in age and intensity under the influence of glacier movements and climatic fluctuations. These properties can be used as indicators of paleoclimatic changes. The diagnosis of ancient pedogenesis was based on criteria with the longest response time, namely, soil morphology, characteristics of organic matter, 13C-NMR spectra of soil humic acids, isotope composition of humus and carbonates, and the soil age. The results indicate a glacial climate of the Late Pleistocene, a dry and cold climate during the Early Holocene, warm and dry conditions of soil formation in the Middle Holocene, and humidity climate of the Late Holocene.

  6. Constraining recharge and groundwater flow processes in hard-rock aquifers in temperate maritime climate using stable isotope signatures.

    Science.gov (United States)

    Pilatova, Katarina; Ofterdinger, Ulrich

    2015-04-01

    Recharge estimates and in understanding flow process in hard rock aquifers pose significant challenges. These arise from structural complexities of the hardrock aquifers and are further complicated by variability of the superficial cover. A comparative study of three metamorphic catchments situated in the North of Ireland is presented in this study, each with contrasting geology, glaciation history and consequently superficial cover. The presented study focusses on two main strains. Firstly, due to lack of existing records, stable water isotopes in precipitation (δ18O and δ2H) were monitored at the research sites and their temporal and spatial variability was examined. Secondly, flow processes and dynamics of groundwater recharge based on continuous records of stable isotopes in groundwater, collected along catchment transects from various depths, and its variability in relation to the acquired precipitation signal were studied. Each precipitation station exhibited distinct isotopic signatures, where weather effect and proximity to coastline are the main controlling factors governing the isotope signatures. Moreover, in each of the stations the isotopic signature varied seasonally and thus stable isotopes proved a useful tool for assessing the dynamics of groundwater recharge. The analysis of isotope signatures in precipitation and groundwater from various depths within the hard rock aquifers allowed to evaluate the timescale of recharge, with rapid responses varying from few days up to several months. In general, the recharge appeared continuous over the hydrological year within wetter catchments with higher annual precipitation amounts purging the hardrock aquifers throughout the year. However, within comparatively dryer catchments recharge has a more seasonal character, predominantly taking place during the winter half of the year. Spatially, the recharge is highly localised within the elevated catchment areas, where superficial deposits are scarce and the

  7. Ice-Core Study of the Link between Sea-Salt Aerosol, Sea-Ice Cover and Climate in the Antarctic Peninsula Area

    Energy Technology Data Exchange (ETDEWEB)

    Aristarain, A.J. [Laboratorio de Estratigrafia Glaciar y Geoquimica del Agua y de la Nieve LEGAN, Instituto Antartico Argentino, Mendoza (Argentina); Delmas, R.J. [Laboratoire de Glaciologie et Geophysique de l' Environnement LGGE, Centre National de la Recherche Scientifique, BP 96, 38402 St. Martin d' Heres Cedex (France); Stievenard, M. [Laboratoire des Sciences du Climat et de l' Environnement LSCE, Centre d' Etudes de Saclay, 91191 Gif-sur-Yvette, Cedex (France)

    2004-11-01

    Three ice cores and a set of snow pit samples collected on James Ross Island, Antarctic Peninsula, in 1979, 1981 and 1991 have been analyzed for water stable isotope content D or 18O (isotopic temperature) and major chemical species. A reliable and detailed chronological scale has been established first for the upper 24.5 m of water equivalent (1990-1943) where various data sets can be compared, then extended down to 59.5 m of water equivalent (1847) with the aid of seasonal variations and the sulphate peak reflecting the 1883 Krakatoa volcanic eruption. At James Ross Island, sea-salt aerosol is generally produced by ice-free marine surfaces during the summer months, although some winter sea-salt events have been observed. For the upper part of the core (1990-1943), correlations (positive or negative) were calculated between isotopic temperature, chloride content (a sea-salt indicator), sea-ice extent, regional atmospheric temperature changes and atmospheric circulation. The D and chloride content correlation was then extended back to 1847, making it possible to estimate decadal sea-ice cover fluctuations over the study period. Our findings suggest that ice-core records from James Ross Island reflect the recent warming and sea-ice decrease trends observed in the Antarctic Peninsula area from the mid-1940s.

  8. Have historical climate changes affected Gentoo penguin (Pygoscelis papua) populations in Antarctica?

    Science.gov (United States)

    Peña M, Fabiola; Poulin, Elie; Dantas, Gisele P M; González-Acuña, Daniel; Petry, Maria Virginia; Vianna, Juliana A

    2014-01-01

    The West Antarctic Peninsula (WAP) has been suffering an increase in its atmospheric temperature during the last 50 years, mainly associated with global warming. This increment of temperature trend associated with changes in sea-ice dynamics has an impact on organisms, affecting their phenology, physiology and distribution range. For instance, rapid demographic changes in Pygoscelis penguins have been reported over the last 50 years in WAP, resulting in population expansion of sub-Antarctic Gentoo penguin (P. papua) and retreat of Antarctic Adelie penguin (P. adeliae). Current global warming has been mainly associated with human activities; however these climate trends are framed in a historical context of climate changes, particularly during the Pleistocene, characterized by an alternation between glacial and interglacial periods. During the last maximal glacial (LGM∼21,000 BP) the ice sheet cover reached its maximum extension on the West Antarctic Peninsula (WAP), causing local extinction of Antarctic taxa, migration to lower latitudes and/or survival in glacial refugia. We studied the HRVI of mtDNA and the nuclear intron βfibint7 of 150 individuals of the WAP to understand the demographic history and population structure of P. papua. We found high genetic diversity, reduced population genetic structure and a signature of population expansion estimated around 13,000 BP, much before the first paleocolony fossil records (∼1,100 BP). Our results suggest that the species may have survived in peri-Antarctic refugia such as South Georgia and North Sandwich islands and recolonized the Antarctic Peninsula and South Shetland Islands after the ice sheet retreat.

  9. Have historical climate changes affected Gentoo penguin (Pygoscelis papua populations in Antarctica?

    Directory of Open Access Journals (Sweden)

    Fabiola Peña M

    Full Text Available The West Antarctic Peninsula (WAP has been suffering an increase in its atmospheric temperature during the last 50 years, mainly associated with global warming. This increment of temperature trend associated with changes in sea-ice dynamics has an impact on organisms, affecting their phenology, physiology and distribution range. For instance, rapid demographic changes in Pygoscelis penguins have been reported over the last 50 years in WAP, resulting in population expansion of sub-Antarctic Gentoo penguin (P. papua and retreat of Antarctic Adelie penguin (P. adeliae. Current global warming has been mainly associated with human activities; however these climate trends are framed in a historical context of climate changes, particularly during the Pleistocene, characterized by an alternation between glacial and interglacial periods. During the last maximal glacial (LGM∼21,000 BP the ice sheet cover reached its maximum extension on the West Antarctic Peninsula (WAP, causing local extinction of Antarctic taxa, migration to lower latitudes and/or survival in glacial refugia. We studied the HRVI of mtDNA and the nuclear intron βfibint7 of 150 individuals of the WAP to understand the demographic history and population structure of P. papua. We found high genetic diversity, reduced population genetic structure and a signature of population expansion estimated around 13,000 BP, much before the first paleocolony fossil records (∼1,100 BP. Our results suggest that the species may have survived in peri-Antarctic refugia such as South Georgia and North Sandwich islands and recolonized the Antarctic Peninsula and South Shetland Islands after the ice sheet retreat.

  10. Climate and Physical Disturbance Effects on the Spectral Signatures of Biological Soil Crusts: Implications for Future Dryland Energy Balance

    Science.gov (United States)

    Rutherford, W. A.; Flagg, C.; Painter, T. H.; Okin, G. S.; Belnap, J.; Reed, S.

    2014-12-01

    Drylands comprise ≈40% of the terrestrial Earth surface and observations suggest they can respond markedly to climate change. A vital component of dryland ecosystems are biological soil crusts (biocrusts) - a network of surface soil lichens, mosses, and cyanobacteria - that perform critical ecosystem functions, such as stabilizing soil and fixing carbon and nitrogen. Yet, our understanding of the role biocrusts play in dryland energy balance remains poor. Changes in climate can rapidly affect biocrust communities and we have long known that biocrusts respond dramatically to physical disturbance, such as human trampling and grazing animals. Associated changes in biocrust cover often result in increased bare soil; creating higher surface reflectance. We used spectral solar reflectance measurements in two manipulative experiments to compare the effects of climate and physical disturbance on biocrusts of the Colorado Plateau We measured reflectance at two heights: at crust surface and 1 m above. The climate disturbance site has four treatments: control, warming (4°C), altered precipitation, and warming plus altered precipitation. The physical disturbance site was trampled by foot annually since 1998. At the climate experiment, the largest change in reflectance was in the altered precipitation treatment (35% increase) at the surface-level, and the smallest difference was in the warmed (17% increase) at the meter-level. Physical disturbance differences were 10% at meter-level and 25% at surface-level. Unexpectedly, these results suggest that, via effects on biocrust communities, climate change could have a larger effect on dryland energy balance relative to physical disturbance, and result in more radiation from drylands returned to the atmosphere. Biocrusts cover large portions of the Earth's surface and, to our knowledge, these are the first data showing climate-induced changes to biocrust reflectance, with negative feedback in the global energy balance.

  11. Antarctic Ice Velocity Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This compilation of recent ice velocity data of the Antarctic ice sheet is intended for use by the polar scientific community. The data are presented in tabular form...

  12. NEW FRONTIERS OF ANTARCTIC SUBGLACIAL LAKES EXPLORATION

    Directory of Open Access Journals (Sweden)

    Pavel Talalay

    2013-01-01

    Full Text Available Antarctic subglacial aquatic environment have become of great interest to the science community because they may provide unique information about microbial evolution, the past climate of the Earth, and the formation of the Antarctic ice sheet. Nowadays it is generally recognized that a vast network of lakes, rivers, and streams exists thousands of meters beneath Antarctic Ice Sheets. Up to date only four boreholes accessed subglacial aquatic system but three of them were filled with high-toxic drilling fluid, and the subglacial water was contaminated. Two recent exploration programs proposed by UK and USA science communities anticipate direct access down to the lakes Ellsworth and Whillans, respectively, in the 2012/2013 Antarctic season. A team of British scientists and engineers engage in the first attempt to drill into Lake Ellsworth but failed. US research team has successfully drilled through 800 m of Antarctic ice to reach a subglacial lake Whillans and retrieve water and sediment samples. Both activities used hot-water drilling technology to access lakes. The main troublesome of the implemented and planned projects for accessing of Antarctic subglacial lakes is connected with the hydrostatic unbalance resulted in the upwelling of water into the hole with subsequent difficulties. The proposed RECoverable Autonomous Sonde “RECAS” would measure and sample subglacial water while subglacial lake is reliably isolated from surface environment, and at the same time the sonde is able to measure geochemical signals in situ throughout the depth of ice sheet on the way to the bed. All process is going on in semi-automatic mode, and the estimated duration of subglacial lake exploration at the depth of 3500 m is 8–9 months. The general concept of the sonde as well as proposed power-supply and performance are given.

  13. A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond

    OpenAIRE

    Kennicutt, M.C.; Chown, S.L.; Cassano, J.J.; Liggett, D.; Peck, L.S.; Massom, R.; Rintoul, S.R.; Storey, J.; Vaughan, D.G.; Wilson, T.J.; Allison, I.; Ayton, J.; Badhe, R.; Baeseman, J.; Barrett, P.J.

    2015-01-01

    Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consu...

  14. Introduction. Antarctic ecology: from genes to ecosystems. Part 2. Evolution, diversity and functional ecology.

    Science.gov (United States)

    Rogers, Alex D; Murphy, Eugene J; Johnston, Nadine M; Clarke, Andrew

    2007-12-29

    The Antarctic biota has evolved over the last 100 million years in increasingly isolated and cold conditions. As a result, Antarctic species, from micro-organisms to vertebrates, have adapted to life at extremely low temperatures, including changes in the genome, physiology and ecological traits such as life history. Coupled with cycles of glaciation that have promoted speciation in the Antarctic, this has led to a unique biota in terms of biogeography, patterns of species distribution and endemism. Specialization in the Antarctic biota has led to trade-offs in many ecologically important functions and Antarctic species may have a limited capacity to adapt to present climate change. These include the direct effects of changes in environmental parameters and indirect effects of increased competition and predation resulting from altered life histories of Antarctic species and the impacts of invasive species. Ultimately, climate change may alter the responses of Antarctic ecosystems to harvesting from humans. The unique adaptations of Antarctic species mean that they provide unique models of molecular evolution in natural populations. The simplicity of Antarctic communities, especially from terrestrial systems, makes them ideal to investigate the ecological implications of climate change, which are difficult to identify in more complex systems.

  15. Underwater Optics in Sub-Antarctic and Antarctic Coastal Ecosystems.

    Directory of Open Access Journals (Sweden)

    Pirjo Huovinen

    Full Text Available Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39-44°S and in an Antarctic bay (62°S. Based on vertical diffuse attenuation coefficients (Kd, derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1% in these water bodies ranged 2-11 m for UV-B (313 nm, 4-27 m for UV-A (395 nm, and 7-30 m for PAR (euphotic zone. UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be

  16. Serious Learning with Science Comics: "Antarctic Log" as a Tool for Understanding Climate Research in AntarcticaScience comics open doors, providing multiple entry points for diverse learners. Karen Romano Young, award-winning author, presents "Antarctic Log", a comic about her spring 2018 Palmer Station tour, a tool for teaching and inspiration.

    Science.gov (United States)

    Young, K. R.

    2017-12-01

    Graphic nonfiction: what is it? Some call these books and articles science comics, but they're no joke: created through research and direct experience by artists invested in creating multiple entry points for new learners, comics can open doors for discovery as introduction, enrichment, or as a vital center point to teaching. Find out what educational pedagogists, scientists, and - yes! - students themselves think about reading, viewing, learning from, and creating science comics in the classroom. Karen Romano Young is the award-winning author of traditional and graphic fiction and nonfiction for children, including Doodlebug, the forthcoming Diving for Deep-Sea Dragons, and the Odyssey/Muse magazine comics feature Humanimal Doodles. In spring 2018 (Antarctic autumn) Young will work as part of a Bigelow Laboratory team studying the production of DMSP by phytoplankton, and the resulting cloud formation. This is invisible stuff, difficult for lay audiences to envision and comprehend. But the audience is already forming around "Antarctic Log," a science comic that tells the story of the science and the experience of doing climate research at Palmer Station as winter draws near. Science comics aren't just for enrichment. They're an invitation, providing multiple entry points for diverse learners. I have received unanticipated support from education groups (including NSTA and IRA), parenting groups, and special educators because these highly visual presentations of middle grade and middle school level material makes the stories and concepts accessible to atypical fiction- and science-reading audiences. As a result, I've learned a great deal about the underlying differences between my material and traditional, text-oriented materials in which visuals may be highly coordinated but are still ancillary. An article that might seem forbidding as text appears open to interpretation in my format, so that readers can pick where to begin reading and how to proceed through the

  17. Response of Antarctic sea surface temperature and sea ice to ozone depletion

    Science.gov (United States)

    Ferreira, D.; Gnanadesikan, A.; Kostov, Y.; Marshall, J.; Seviour, W.; Waugh, D.

    2017-12-01

    The influence of the Antarctic ozone hole extends all the way from the stratosphere through the troposphere down to the surface, with clear signatures on surface winds, and SST during summer. In this talk we discuss the impact of these changes on the ocean circulation and sea ice state. We are notably motivated by the observed cooling of the surface Southern Ocean and associated increase in Antarctic sea ice extent since the 1970s. These trends are not reproduced by CMIP5 climate models, and the underlying mechanism at work in nature and the models remain unexplained. Did the ozone hole contribute to the observed trends?Here, we review recent advances toward answering these issues using "abrupt ozone depletion" experiments. The ocean and sea ice response is rather complex, comprising two timescales: a fast ( 1-2y) cooling of the surface ocean and sea ice cover increase, followed by a slower warming trend, which, depending on models, flip the sign of the SST and sea ice responses on decadal timescale. Although the basic mechanism seems robust, comparison across climate models reveal large uncertainties in the timescales and amplitude of the response to the extent that even the sign of the ocean and sea ice response to ozone hole and recovery remains unconstrained. After briefly describing the dynamics and thermodynamics behind the two-timescale response, we will discuss the main sources of uncertainties in the modeled response, namely cloud effects and air-sea heat exchanges, surface wind stress response and ocean eddy transports. Finally, we will consider the implications of our results on the ability of coupled climate models to reproduce observed Southern Ocean changes.

  18. Vertical profiles of specific surface area, thermal conductivity and density of mid-latitude, Arctic and Antarctic snow: relationships between snow physics and climat

    Science.gov (United States)

    Domine, F.; Arnaud, L.; Bock, J.; Carmagnola, C.; Champollion, N.; Gallet, J.; Lesaffre, B.; Morin, S.; Picard, G.

    2011-12-01

    We have measured vertical profiles of specific surface area (SSA), thermal conductivity (TC) and density in snow from 12 different climatic regions featuring seasonal snowpacks of maritime, Alpine, taiga and tundra types, on Arctic sea ice, and from ice caps in Greenland and Antarctica. We attempt to relate snow physical properties to climatic variables including precipitation, temperature and its yearly variation, wind speed and its short scale temporal variations. As expected, temperature is a key variable that determines snow properties, mostly by determining the metamorphic regime (temperature gradient or equi-temperature) in conjunction with precipitation. However, wind speed and wind speed distribution also seem to have an at least as important role. For example high wind speeds determine the formation of windpacks of high SSA and high TC instead of depth hoar with lower values of these variables. The distribution of wind speed also strongly affects properties, as for example frequent moderate winds result in frequent snow remobilization, producing snow with higher SSA and lower TC than regions with the same average wind speeds, but with less frequent and more intense wind episodes. These strong effects of climate on snow properties imply that climate change will greatly modify snow properties, which in turn will affect climate, as for example changes in snow SSA modify albedo and changes in TC affect permafrost and the release of greenhouse gases from thawing permafrost. Some of these climate-snow feedbacks will be discussed.

  19. Climate and root proximity as dominant drivers of enzyme activity and C and N isotopic signature in soil

    Science.gov (United States)

    Stock, Svenja; Köster, Moritz; Dippold, Michaela; Boy, Jens; Matus, Francisco; Merino, Carolina; Nájera, Francisco; Spielvogel, Sandra; Gorbushina, Anna; Kuzyakov, Yakov

    2017-04-01

    The Chilean ecosystems provide a unique study area to investigate biotic controls on soil organic matter (SOM) decomposition and mineral weathering depending on climate (from hyper arid to temperate humid). Microorganisms play a crucial role in the SOM decomposition, nutrient release and cycling. By means of extracellular enzymes microorganisms break down organic compounds and provide nutrients for plants. Soil moisture (abiotic factor) and root carbon (biotic factor providing easily available energy source for microorganisms), are important factors for microbial decomposition of SOM and show strong gradients along the investigated climatic gradient. A high input of root carbon increases microbial activity and enzyme production, and facilitates SOM breakdown and nutrient release The aim of this study was to determine the potential enzymatic SOM decomposition and nutrient release depending on root proximity and precipitation. C and N contents, δ13C and δ15N values, and kinetics (Vmax, Km) of six extracellular enzymes, responsible for C, N, and P cycles, were quantified in vertical (soil depth) and horizontal (from roots to bulk soil) gradients in two climatic regions: within a humid temperate forest and a semiarid open forest. The greater productivity of the temperate forest was reflected by higher C and N contents compared to the semiarid forest. Regression lines between δ13C and -[ln(%C)] showed a stronger isotopic fractionation from top- to subsoil at the semiarid open forest, indicating a faster SOM turnover compared to the humid temperate forest. This is the result of more favorable soil conditions (esp. temperature and smaller C/N ratios) in the semiarid forest. Depth trends of δ15N values indicated N limitation in both soils, though the limitation at the temperate site was stronger. The activity of enzymes degrading cellulose and hemicellulose increased with C content. Activity of enzymes involved in C, N and P cycles decreased from top- to subsoil and

  20. Uncertainties in the Antarctic Ice Sheet Contribution to Sea Level Rise: Exploration of Model Response to Errors in Climate Forcing, Boundary Conditions, and Internal Parameters

    Science.gov (United States)

    Schlegel, N.; Seroussi, H. L.; Boening, C.; Larour, E. Y.; Limonadi, D.; Schodlok, M.; Watkins, M. M.

    2017-12-01

    The Jet Propulsion Laboratory-University of California at Irvine Ice Sheet System Model (ISSM) is a thermo-mechanical 2D/3D parallelized finite element software used to physically model the continental-scale flow of ice at high resolutions. Embedded into ISSM are uncertainty quantification (UQ) tools, based on the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA) software. ISSM-DAKOTA offers various UQ methods for the investigation of how errors in model input impact uncertainty in simulation results. We utilize these tools to regionally sample model input and key parameters, based on specified bounds of uncertainty, and run a suite of continental-scale 100-year ISSM forward simulations of the Antarctic Ice Sheet. Resulting diagnostics (e.g., spread in local mass flux and regional mass balance) inform our conclusion about which parameters and/or forcing has the greatest impact on century-scale model simulations of ice sheet evolution. The results allow us to prioritize the key datasets and measurements that are critical for the minimization of ice sheet model uncertainty. Overall, we find that Antartica's total sea level contribution is strongly affected by grounding line retreat, which is driven by the magnitude of ice shelf basal melt rates and by errors in bedrock topography. In addition, results suggest that after 100 years of simulation, Thwaites glacier is the most significant source of model uncertainty, and its drainage basin has the largest potential for future sea level contribution. This work is performed at and supported by the California Institute of Technology's Jet Propulsion Laboratory. Supercomputing time is also supported through a contract with the National Aeronautics and Space Administration's Cryosphere program.

  1. Subsurface Salts in Antarctic Dry Valley Soils

    Science.gov (United States)

    Englert, P.; Bishop, J. L.; Gibson, E. K.; Koeberl, C.

    2013-01-01

    The distribution of water-soluble ions, major and minor elements, and other parameters were examined to determine the extent and effects of chemical weathering on cold desert soils. Patterns at the study sites support theories of multiple salt forming processes, including marine aerosols and chemical weathering of mafic minerals. Periodic solar-mediated ionization of atmospheric nitrogen might also produce high nitrate concentrations found in older sediments. Chemical weathering, however, was the major contributor of salts in Antarctic Dry Valleys. The Antarctic Dry Valleys represent a unique analog for Mars, as they are extremely cold and dry desert environments. Similarities in the climate, surface geology, and chemical properties of the Dry Valleys to that of Mars imply the possible presence of these soil formation mechanisms on Mars, other planets and icy satellites.

  2. The signs of Antarctic ozone hole recovery.

    Science.gov (United States)

    Kuttippurath, Jayanarayanan; Nair, Prijitha J

    2017-04-03

    Absorption of solar radiation by stratospheric ozone affects atmospheric dynamics and chemistry, and sustains life on Earth by preventing harmful radiation from reaching the surface. Significant ozone losses due to increases in the abundances of ozone depleting substances (ODSs) were first observed in Antarctica in the 1980s. Losses deepened in following years but became nearly flat by around 2000, reflecting changes in global ODS emissions. Here we show robust evidence that Antarctic ozone has started to recover in both spring and summer, with a recovery signal identified in springtime ozone profile and total column measurements at 99% confidence for the first time. Continuing recovery is expected to impact the future climate of that region. Our results demonstrate that the Montreal Protocol has indeed begun to save the Antarctic ozone layer.

  3. Development of a regional glycerol dialkyl glycerol tetraether (GDGT)-temperature calibration for Antarctic and sub-Antarctic lakes

    Science.gov (United States)

    Foster, Louise C.; Pearson, Emma J.; Juggins, Steve; Hodgson, Dominic A.; Saunders, Krystyna M.; Verleyen, Elie; Roberts, Stephen J.

    2016-01-01

    A regional network of quantitative reconstructions of past climate variability is required to test climate models. In recent studies, temperature calibration models based on the relative abundances of sedimentary glycerol dialkyl glycerol tetraethers (GDGTs) have enabled past temperature reconstructions in both marine and terrestrial environments. Nevertheless, to date these methods have not been widely applied in high latitude environments due to poor performance of the GDGT-temperature calibrations at lower temperatures. To address this we studied 32 lakes from Antarctica, the sub-Antarctic Islands and Southern Chile to: 1) quantify their GDGT composition and investigate the environmental controls on GDGT composition; and 2) develop a GDGT-temperature calibration model for inferring past temperatures from Antarctic and sub-Antarctic lakes. GDGTs were found in all 32 lakes studied and in 31 lakes branched GDGTs (brGDGTs) were the dominant compounds. Statistical analyses of brGDGT composition in relation to temperature, pH, conductivity and water depth showed that the composition of brGDGTs is strongly correlated with mean summer air temperature (MSAT). This enabled the development of the first regional brGDGT-temperature calibration for use in Antarctic and sub-Antarctic lakes using four brGDGT compounds (GDGT-Ib, GDGT-II, GDGT-III and GDGT-IIIb). A key discovery was that GDGT-IIIb is of particular importance in cold lacustrine environments. The addition of this compound significantly improved the model's performance from r2 = 0.67, RMSEP-LOO (leave-one-out) = 2.23 °C, RMSEP-H (h-block) = 2.37 °C when applying the re-calibrated global GDGT-temperature calibration to our Antarctic dataset to r2 = 0.83, RMSEP-LOO = 1.68 °C, RMSEP-H = 1.65 °C for our new Antarctic calibration. This shows that Antarctic and sub-Antarctic, and possibly other high latitude, palaeotemperature reconstructions should be based on a regional GDGT-temperature calibration where specific

  4. Structural Uncertainty in Antarctic sea ice simulations

    Science.gov (United States)

    Schneider, D. P.

    2016-12-01

    The inability of the vast majority of historical climate model simulations to reproduce the observed increase in Antarctic sea ice has motivated many studies about the quality of the observational record, the role of natural variability versus forced changes, and the possibility of missing or inadequate forcings in the models (such as freshwater discharge from thinning ice shelves or an inadequate magnitude of stratospheric ozone depletion). In this presentation I will highlight another source of uncertainty that has received comparatively little attention: Structural uncertainty, that is, the systematic uncertainty in simulated sea ice trends that arises from model physics and mean-state biases. Using two large ensembles of experiments from the Community Earth System Model (CESM), I will show that the model is predisposed towards producing negative Antarctic sea ice trends during 1979-present, and that this outcome is not simply because the model's decadal variability is out-of-synch with that in nature. In the "Tropical Pacific Pacemaker" ensemble, in which observed tropical Pacific SST anomalies are prescribed, the model produces very realistic atmospheric circulation trends over the Southern Ocean, yet the sea ice trend is negative in every ensemble member. However, if the ensemble-mean trend (commonly interpreted as the forced response) is removed, some ensemble members show a sea ice increase that is very similar to the observed. While this results does confirm the important role of natural variability, it also suggests a strong bias in the forced response. I will discuss the reasons for this systematic bias and explore possible remedies. This an important problem to solve because projections of 21st -Century changes in the Antarctic climate system (including ice sheet surface mass balance changes and related changes in the sea level budget) have a strong dependence on the mean state of and changes in the Antarctic sea ice cover. This problem is not unique to

  5. Antarctic climate variability during the past few centuries based on ice core records from coastal Dronning Maud Land and its implications on the Recent warming

    Digital Repository Service at National Institute of Oceanography (India)

    Thamban, M.; Naik, S.S.; Laluraj, C.M.; Chaturvedi, A.; Ravindra, R.

    records in two cores correspond to changes in low and mid latitude climatic modes like the Southern Annular Mode (SAM) and El Nino Southern Oscillation (ENSO). The estimated surface air temperatures using the delta sup(18) O profiles of two ice cores...

  6. Forecasting Antarctic Sea Ice Concentrations Using Results of Temporal Mixture Analysis

    Science.gov (United States)

    Chi, Junhwa; Kim, Hyun-Cheol

    2016-06-01

    Sea ice concentration (SIC) data acquired by passive microwave sensors at daily temporal frequencies over extended areas provide seasonal characteristics of sea ice dynamics and play a key role as an indicator of global climate trends; however, it is typically challenging to study long-term time series. Of the various advanced remote sensing techniques that address this issue, temporal mixture analysis (TMA) methods are often used to investigate the temporal characteristics of environmental factors, including SICs in the case of the present study. This study aims to forecast daily SICs for one year using a combination of TMA and time series modeling in two stages. First, we identify temporally meaningful sea ice signatures, referred to as temporal endmembers, using machine learning algorithms, and then we decompose each pixel into a linear combination of temporal endmembers. Using these corresponding fractional abundances of endmembers, we apply a autoregressive model that generally fits all Antarctic SIC data for 1979 to 2013 to forecast SIC values for 2014. We compare our results using the proposed approach based on daily SIC data reconstructed from real fractional abundances derived from a pixel unmixing method and temporal endmember signatures. The proposed method successfully forecasts new fractional abundance values, and the resulting images are qualitatively and quantitatively similar to the reference data.

  7. Regional genetic diversity patterns in Antarctic hairgrass (Deschampsia antartica Desv.)

    NARCIS (Netherlands)

    van de Wouw, M.J.; Van Dijk, P.J.; Huiskes, A.H.L.

    2008-01-01

    Aim To determine patterns in diversity of a major Antarctic plant species, including relationships of Antarctic populations with those outside the Antarctic zone. Location Antarctic Peninsula, Maritime Antarctica, sub-Antarctic islands, Falkland Islands and South America. Methods Amplified fragment

  8. Antarctic meteorology, a study with automatic weather stations

    NARCIS (Netherlands)

    Reijmer, C.H.

    2001-01-01

    This thesis chiefly addresses a) the use of Automatic Weather Stations (AWS) in determining the near-surface climate and heat budget of Antarctica and, specifically, Dronning Maud Land (DML), and b) the determination of source regions of Antarctic moisture with the aid of a trajectory model and an

  9. TEMPERATURE REQUIREMENTS AND BIOGEOGRAPHY OF ANTARCTIC, ARCTIC AND AMPHIEQUATORIAL SEAWEEDS

    NARCIS (Netherlands)

    WIENCKE, C; BARTSCH, [No Value; BISCHOFF, B; PETERS, AF; BREEMAN, AM

    The temperature requirements for growth and survival of cold water seaweeds from both Hemispheres are compared and discussed in relation to the climatic history of the various regions and in relation to the origin of amphiequatorial distribution patterns. Endemic Antarctic species are most strongly

  10. Basin-scale heterogeneity in Antarctic precipitation and its impact on surface mass variability

    Directory of Open Access Journals (Sweden)

    J. Fyke

    2017-11-01

    Full Text Available Annually averaged precipitation in the form of snow, the dominant term of the Antarctic Ice Sheet surface mass balance, displays large spatial and temporal variability. Here we present an analysis of spatial patterns of regional Antarctic precipitation variability and their impact on integrated Antarctic surface mass balance variability simulated as part of a preindustrial 1800-year global, fully coupled Community Earth System Model simulation. Correlation and composite analyses based on this output allow for a robust exploration of Antarctic precipitation variability. We identify statistically significant relationships between precipitation patterns across Antarctica that are corroborated by climate reanalyses, regional modeling and ice core records. These patterns are driven by variability in large-scale atmospheric moisture transport, which itself is characterized by decadal- to centennial-scale oscillations around the long-term mean. We suggest that this heterogeneity in Antarctic precipitation variability has a dampening effect on overall Antarctic surface mass balance variability, with implications for regulation of Antarctic-sourced sea level variability, detection of an emergent anthropogenic signal in Antarctic mass trends and identification of Antarctic mass loss accelerations.

  11. Radiation signatures

    International Nuclear Information System (INIS)

    McGlynn, S.P.; Varma, M.N.

    1992-01-01

    A new concept for modelling radiation risk is proposed. This concept is based on the proposal that the spectrum of molecular lesions, which we dub ''the radiation signature'', can be used to identify the quality of the causal radiation. If the proposal concerning radiation signatures can be established then, in principle, both prospective and retrospective risk determination can be assessed on an individual basis. A major goal of biophysical modelling is to relate physical events such as ionization, excitation, etc. to the production of radiation carcinogenesis. A description of the physical events is provided by track structure. The track structure is determined by radiation quality, and it can be considered to be the ''physical signature'' of the radiation. Unfortunately, the uniqueness characteristics of this signature are dissipated in biological systems in ∼10 -9 s. Nonetheless, it is our contention that this physical disturbance of the biological system eventuates later, at ∼10 0 s, in molecular lesion spectra which also characterize the causal radiation. (author)

  12. Modelling the Antarctic Ice Sheet

    DEFF Research Database (Denmark)

    Pedersen, Jens Olaf Pepke; Holm, A.

    2015-01-01

    Science) Antarctic Ice Sheet (DAIS) model (Shaffer 2014) is forced by reconstructed time series of Antarctic temperature, global sea level and ocean subsurface temperature over the last two glacial cycles. In this talk a modelling work of the Antarctic ice sheet over most of the Cenozoic era using...... the DAIS model will be presented. G. Shaffer (2014) Formulation, calibration and validation of the DAIS model (version 1), a simple Antarctic ice sheet model sensitive to variations of sea level and ocean subsurface temperature, Geosci. Model Dev., 7, 1803‐1818...

  13. Aglomerularism in Antarctic fish.

    Science.gov (United States)

    Dobbs, G H; Lin, Y; DeVries, A L

    1974-08-30

    Urine formation in antarctic bony fish does not involve glomerular filtration. Evidence for aglomerularism came from both direct observation of kidney serial sections by light microscopy and the low concentrations of inulin labeled with carbon-14 that were excreted into the urine when this renal clearance tracer was injected into the bloodstream via a cannula implanted in the caudal vein. Aglomerularism most likely prevents urinary loss of glycoproteins with biological antifreeze properties.

  14. Microbial biomass and basal respiration of selected Sub-Antarctic and Antarctic soils in the areas of some Russian polar stations

    Science.gov (United States)

    Abakumov, E.; Mukhametova, N.

    2014-07-01

    Antarctica is a unique place for soil, biological, and ecological investigations. Soils of Antarctica have been studied intensively during the last century, when different national Antarctic expeditions visited the sixth continent with the aim of investigating nature and the environment. Antarctic investigations are comprised of field surveys mainly in the terrestrial landscapes, where the polar stations of different countries are situated. That is why the main and most detailed soil surveys were conducted in the McMurdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann Hills and the Schirmacher Oasis. Our investigations were conducted during the 53rd and 55th Russian Antarctic expeditions in the base of soil pits, and samples were collected in Sub-Antarctic and Antarctic regions. Sub-Antarctic or maritime landscapes are considered to be very different from Antarctic landscapes due to differing climatic and geogenic conditions. Soils of diverse zonal landscapes were studied with the aim of assessing the microbial biomass level, basal respiration rates and metabolic activity of microbial communities. This investigation shows that Antarctic soils are quite diverse in profile organization and carbon content. In general, Sub-Antarctic soils are characterized by more developed humus (sod) organo-mineral horizons as well as by an upper organic layer. The most developed organic layers were revealed in peat soils of King George Island, where its thickness reach, in some cases, was 80 cm. These soils as well as soils formed under guano are characterized by the highest amount of total organic carbon (TOC), between 7.22 and 33.70%. Coastal and continental Antarctic soils exhibit less developed Leptosols, Gleysols, Regolith and rare Ornhitosol, with TOC levels between 0.37 and 4.67%. The metabolic ratios and basal respiration were higher in Sub-Antarctic soils than in Antarctic ones, which can be interpreted as a result of higher amounts of fresh organic

  15. Antarctic, Sub-Antarctic and cold temperate echinoid database

    Directory of Open Access Journals (Sweden)

    Benjamin Pierrat

    2012-06-01

    Full Text Available This database includes spatial data of Antarctic, Sub-Antarctic and cold temperate echinoid distribution (Echinodermata: Echinoidea collected during many oceanographic campaigns led in the Southern Hemisphere from 1872 to 2010. The dataset lists occurrence data of echinoid distribution south of 35°S latitude, together with information on taxonomy (from species to genus level, sampling sources (cruise ID, sampling dates, ship names and sampling sites (geographic coordinates and depth. Echinoid occurrence data were compiled from the Antarctic Echinoid Database (David et al., 2005a, which integrates records from oceanographic cruises led in the Southern Ocean until 2003. This database has been upgraded to take into account data from oceanographic cruises led after 2003. The dataset now reaches a total of 6160 occurrence data that have been checked for systematics reliability and consistency. It constitutes today the most complete database on Antarctic and Sub-Antarctic echinoids.

  16. A multivariate analysis of Antarctic sea ice since 1979

    Energy Technology Data Exchange (ETDEWEB)

    Magalhaes Neto, Newton de; Evangelista, Heitor [Universidade do Estado do Rio de Janeiro (Uerj), LARAMG - Laboratorio de Radioecologia e Mudancas Globais, Maracana, Rio de Janeiro, RJ (Brazil); Tanizaki-Fonseca, Kenny [Universidade do Estado do Rio de Janeiro (Uerj), LARAMG - Laboratorio de Radioecologia e Mudancas Globais, Maracana, Rio de Janeiro, RJ (Brazil); Universidade Federal Fluminense (UFF), Dept. Analise Geoambiental, Inst. de Geociencias, Niteroi, RJ (Brazil); Penello Meirelles, Margareth Simoes [Universidade do Estado do Rio de Janeiro (UERJ)/Geomatica, Maracana, Rio de Janeiro, RJ (Brazil); Garcia, Carlos Eiras [Universidade Federal do Rio Grande (FURG), Laboratorio de Oceanografia Fisica, Rio Grande, RS (Brazil)

    2012-03-15

    Recent satellite observations have shown an increase in the total extent of Antarctic sea ice, during periods when the atmosphere and oceans tend to be warmer surrounding a significant part of the continent. Despite an increase in total sea ice, regional analyses depict negative trends in the Bellingshausen-Amundsen Sea and positive trends in the Ross Sea. Although several climate parameters are believed to drive the formation of Antarctic sea ice and the local atmosphere, a descriptive mechanism that could trigger such differences in trends are still unknown. In this study we employed a multivariate analysis in order to identify the response of the Antarctic sea ice with respect to commonly utilized climate forcings/parameters, as follows: (1) The global air surface temperature, (2) The global sea surface temperature, (3) The atmospheric CO{sub 2} concentration, (4) The South Annular Mode, (5) The Nino 3, (6) The Nino (3 + 4, 7) The Nino 4, (8) The Southern Oscillation Index, (9) The Multivariate ENSO Index, (10) the Total Solar Irradiance, (11) The maximum O{sub 3} depletion area, and (12) The minimum O{sub 3} concentration over Antarctica. Our results indicate that western Antarctic sea ice is simultaneously impacted by several parameters; and that the minimum, mean, and maximum sea ice extent may respond to a separate set of climatic/geochemical parameters. (orig.)

  17. Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

    Science.gov (United States)

    Goldner, A; Herold, N; Huber, M

    2014-07-31

    Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

  18. Monitoring Antarctic ice sheet surface melting with TIMESAT algorithm

    Science.gov (United States)

    Ye, Y.; Cheng, X.; Li, X.; Liang, L.

    2011-12-01

    Antarctic ice sheet contributes significantly to the global heat budget by controlling the exchange of heat, moisture, and momentum at the surface-atmosphere interface, which directly influence the global atmospheric circulation and climate change. Ice sheet melting will cause snow humidity increase, which will accelerate the disintegration and movement of ice sheet. As a result, detecting Antarctic ice sheet melting is essential for global climate change research. In the past decades, various methods have been proposed for extracting snowmelt information from multi-channel satellite passive microwave data. Some methods are based on brightness temperature values or a composite index of them, and others are based on edge detection. TIMESAT (Time-series of Satellite sensor data) is an algorithm for extracting seasonality information from time-series of satellite sensor data. With TIMESAT long-time series brightness temperature (SSM/I 19H) is simulated by Double Logistic function. Snow is classified to wet and dry snow with generalized Gaussian model. The results were compared with those from a wavelet algorithm. On this basis, Antarctic automatic weather station data were used for ground verification. It shows that this algorithm is effective in ice sheet melting detection. The spatial distribution of melting areas(Fig.1) shows that, the majority of melting areas are located on the edge of Antarctic ice shelf region. It is affected by land cover type, surface elevation and geographic location (latitude). In addition, the Antarctic ice sheet melting varies with seasons. It is particularly acute in summer, peaking at December and January, staying low in March. In summary, from 1988 to 2008, Ross Ice Shelf and Ronnie Ice Shelf have the greatest interannual variability in amount of melting, which largely determines the overall interannual variability in Antarctica. Other regions, especially Larsen Ice Shelf and Wilkins Ice Shelf, which is in the Antarctic Peninsula

  19. Synchronizing Greenland ice-core records and the Meerfelder maar sediment record via the global cosmogenic radionuclide signature and insights on climate around 11,230 years BP

    Science.gov (United States)

    Mekhaldi, F.; Czymzik, M.; Brauer, A.; Martin-Puertas, C.; Aldahan, A.; Possnert, G.; Muscheler, R.

    2017-12-01

    The causal investigation of multiple paleoclimate records relies on the accuracy of their respective chronostratigraphy. To achieve relative synchronization, cosmogenic radionuclides are an excellent tool because their common signature is global and can be retrieved and measured in different paleoclimate archives. For instance, 10Be can be measured in both ice cores and lake sediments (Berggren et al., 2013; Czymzik et al., 2016) which allows for both archives to be anchored onto radiocarbon timescales by synchronizing 10Be with 14C. We investigate the period 11,500-11,000 years BP when a short cold climate spell is known, from ice-core proxy records, to have occurred in Greenland shortly after the onset of the Holocene - the Preboreal Oscillation (PBO). This period also coincides with one of the largest and longest-lived increase in 14C production rate during the Holocene, which most likely corresponds to a grand solar minimum (around 11,230-11,000 years BP). In consequence, this period ideally illustrates the potential of using a known and clear signal in the production rate of cosmogenic radionuclides as a synchronizing tool, such as caused by large variations in solar activity. Here we measure 10Be in Meerfelder Maar (a well-dated and widely used sediment record from Germany) around 11,230 years BP which allows us to align the 10Be signal in both the Meerfelder Maar (MFM) sediment record and the GRIP ice core to IntCal13. Doing so, we report that i) the structure of the grand solar minimum is well-preserved in the 10Be signal of MFM sediments, ii) the PBO in Greenland occurs during high levels of solar activity and is not clearly observed in MFM, and iii) the PBO in Greenland ends precisely at the onset of the grand solar minimum at 11,230 years BP which also corresponds to a depositional change in MFM sediments (Martin-Puertas et al., 2017). These results thus suggest that changes in solar activity could have been a forcing at play eventually resulting in the

  20. Contrasting Arctic and Antarctic atmospheric responses to future sea-ice loss

    Science.gov (United States)

    England, M.; Polvani, L. M.; Sun, L.

    2017-12-01

    By the end of this century, the annual mean Antarctic sea ice area is projected to decline by over a third, an amount similar to that in the Arctic, but the effect of Antarctic sea ice loss on the atmosphere remains largely unexplored. Using the Community Earth Systems Model (CESM) Whole Atmosphere Coupled Climate Model (WACCM), we investigate the effect of future Antarctic sea ice loss, and contrast it with its Arctic counterpart. This is accomplished by analyzing integrations of the model with historic and future sea ice levels, using the RCP8.5 scenario. This allows us to disentangle the effect of future sea ice loss on the atmosphere from other aspects of the coupled system. We find that both Antarctic and Arctic sea ice loss act to shift the tropospheric jet equatorwards, counteracting the poleward shift due to increases in greenhouse gases. Although the total forcing to the atmosphere is similar in both hemispheres, the response to Arctic sea ice loss is larger in amplitude and but more seasonally varying, while the response in the Antarctic persists throughout the year but with a smaller amplitude. Furthermore, the atmospheric temperature response over the Antarctic is trapped closer to the surface than in the Arctic, and perhaps surprisingly, we find that the surface temperature response to Antarctic sea ice loss is unable to penetrate the Antarctic continent.

  1. Recovery of the Antarctic Ozone Hole

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve; Schauffler, Sue; Stolarski, Richard S.; Douglass, Anne R.; Pawson, Steven; Nielsen, J. Eric

    2006-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS and OMI instruments. The severity of the hole has been assessed using the minimum total ozone value from the October monthly mean (depth of the hole), the average size during the September-October period, and the ozone mass deficit. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. We use two methods to estimate ozone hole recovery. First, we use projections of halogen levels combined with age-of-air estimates in a parametric model. Second, we use a coupled chemistry climate model to assess recovery. We find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. Furthermore, full recovery to 1980 levels will not occur until approximately 2068. We will also show some error estimates of these dates and the impact of climate change on the recovery.

  2. Ecuadorian antarctic act

    International Nuclear Information System (INIS)

    1998-02-01

    To develop research in this continent involves to take communion with earth where the cold pole of the planet is located, the stormiest sea of the world surround it and where the capricious continental and geographical distribution permits the pass of meteorological violent and continuous systems. The Ecuador, in execution of the acquired commitments like Full Member of the System of the Antarctic Treaty, carried out the VII Expedition to the White Continent with an extensive program of scientific investigation in the field of: Sciences of Life, Sciences of the Earth and Atmospheric Sciences, so much in the environment of the Pacific Southeast, the Drake Pass, Bransfield Strait and the nearby ecosystems antarctic to Point Fort William in the Greenwich Island, site where the Ecuadorian station Pedro Vicente Maldonado is located. The scientific articles, result of the fruitful work of national investigator is consigned in this fourth edition. This publication constitutes our contribution to the world in the knowledge, understanding and handling of the marvelous White Continent from the middle of our planet, Ecuador

  3. Contributions to Antarctic research II

    National Research Council Canada - National Science Library

    Elliot, David H

    1991-01-01

    Contents: The Antarctic research series: statement of objectives - Pedogenic linkages between the cold deserts of Antarctica and the polar deserts - Ablation rates of the ice fields in the vicinity of the Allan Hills, Victoria Land...

  4. Images of Antarctic Ice Shelves

    Data.gov (United States)

    National Aeronautics and Space Administration — Recent changes in the extent and stability of ice shelves in the Antarctic Peninsula prompted NSIDC to begin a monitoring program using data from the AVHRR Polar 1...

  5. Source-specific diatom lipid biomarkers as proxies for Arctic and Antarctic sea ice

    Science.gov (United States)

    Belt, Simon

    2016-04-01

    Sea ice plays a key role in controlling global climate due its influence over heat and gas exchange between the oceans and the atmosphere. In addition, sea ice exerts a strong influence over the absorption of incoming radiation at the ocean surface as a result of its high reflectivity or albedo. Driven, in part, by the recent dramatic changes to sea ice cover in both the Arctic and the Antarctic, the development of proxies for sea ice has received growing attention over the last 10 years or so. Amongst these, some so-called highly branched isoprenoid (HBI) lipid biomarkers have attracted considerable interest, not least, because they are derived from certain diatoms that reside and bloom within the sea ice matrix itself, thus providing a more direct indication of sea ice presence compared with some other proxies. The signature HBI sea proxies are a mono-unsaturated HBI (IP25) for the Arctic and a di-unsaturated HBI (C25:2) for the Antarctic, with different source organisms for each. Although the variability in sedimentary abundances of IP25 and C25:2 in Arctic and Antarctic sediments generally reflect the corresponding changes in sea ice conditions, a more complete picture of reconstructing sea ice conditions likely requires a multi-proxy approach involving, for example, other lipid biomarkers that serve as proxy measures of nearby open water conditions or sea surface temperature. By adoption of such an approach, a research strategy aimed at improving estimates of sea ice concentrations or better definitions of sea ice conditions (e.g. marginal ice zone, polynyas, permanent ice cover) represents the next stage in lipid-based sea ice proxy development. This presentation will focus on recent developments and future plans that involve a multi-proxy approach to improving sea ice reconstruction. An understanding of sources, ecology and environmental fate of various HBIs and other diatom lipids will likely be key in shaping the future direction of lipid-based sea ice

  6. The climatic out of control. the climatic forcing

    International Nuclear Information System (INIS)

    Bony-Lena, S.; Dufresne, J.L.; Acot, P.; Friedlingstein, P.; Berger, A.; Loutre, M.L.; Raynaud, D.; Thuiller, W.; Le Treut, H.; Houssais, M.N.; Duplessy, J.C.; Royer, J.F.; Douville, H.; Barberousse, A.; Quinon, P.

    2007-01-01

    The expert group on the climate evolution affirms that the global warming is unequivocal and that the human being is the main responsible. This document broaches the climatic change under many aspects: the principle, the historical aspect of the greenhouse effect, the GIEC, the carbon cycle, the paleo-climate theory, the antarctic ices and the impacts of the climatic change on the biodiversity, the simulations and the models, the climatic indicators and the climatic forcing by human activities. (A.L.B.)

  7. Mass balance of the Antarctic ice sheet.

    Science.gov (United States)

    Wingham, D J; Shepherd, A; Muir, A; Marshall, G J

    2006-07-15

    The Antarctic contribution to sea-level rise has long been uncertain. While regional variability in ice dynamics has been revealed, a picture of mass changes throughout the continental ice sheet is lacking. Here, we use satellite radar altimetry to measure the elevation change of 72% of the grounded ice sheet during the period 1992-2003. Depending on the density of the snow giving rise to the observed elevation fluctuations, the ice sheet mass trend falls in the range -5-+85Gtyr-1. We find that data from climate model reanalyses are not able to characterise the contemporary snowfall fluctuation with useful accuracy and our best estimate of the overall mass trend-growth of 27+/-29Gtyr-1-is based on an assessment of the expected snowfall variability. Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica. The result exacerbates the difficulty of explaining twentieth century sea-level rise.

  8. Unmanned aerial optical systems for spatial monitoring of Antarctic mosses

    Science.gov (United States)

    Lucieer, Arko; Turner, Darren; Veness, Tony; Malenovsky, Zbynek; Harwin, Stephen; Wallace, Luke; Kelcey, Josh; Robinson, Sharon

    2013-04-01

    The Antarctic continent has experienced major changes in temperature, wind speed and stratospheric ozone levels during the last 50 years. In a manner similar to tree rings, old growth shoots of Antarctic mosses, the only plants on the continent, also preserve a climate record of their surrounding environment. This makes them an ideal bio-indicator of the Antarctic climate change. Spatially extensive ground sampling of mosses is laborious and time limited due to the short Antarctic growing season. Obviously, there is a need for an efficient method to monitor spatially climate change induced stress of the Antarctic moss flora. Cloudy weather and high spatial fragmentation of the moss turfs makes satellite imagery unsuitable for this task. Unmanned aerial systems (UAS), flying at low altitudes and collecting image data even under a full overcast, can, however, overcome the insufficiency of satellite remote sensing. We, therefore, developed scientific UAS, consisting of a remote-controlled micro-copter carrying on-board different remote sensing optical sensors, tailored to perform fast and cost-effective mapping of Antarctic flora at ultra-high spatial resolution (1-10 cm depending on flight altitude). A single lens reflex (SLR) camera carried by UAS acquires multi-view aerial photography, which processed by the Structure from Motion computer vision algorithm provides an accurate three-dimensional digital surface model (DSM) at ultra-high spatial resolution. DSM is the key input parameter for modelling a local seasonal snowmelt run-off, which provides mosses with the vital water supply. A lightweight multispectral camera on-board of UVS is collecting images of six selected spectral wavebands with the full-width-half-maximum (FWHM) of 10 nm. The spectral bands can be used to compute various vegetation optical indices, e.g. Difference Vegetation Index (NDVI) or Photochemical Reflectance Index (PRI), assessing the actual physiological state of polar vegetation. Recently

  9. Contrasting time trends of organic contaminants in Antarctic pelagic and benthic food webs.

    Science.gov (United States)

    van den Brink, Nico W; Riddle, Martin J; van den Heuvel-Greve, Martine; van Franeker, Jan Andries

    2011-01-01

    We demonstrate that pelagic Antarctic seabirds show significant decreases in concentrations of some persistent organic pollutants. Trends in Adélie penguins and Southern fulmars fit in a general pattern revealed by a broad literature review. Downward trends are also visible in pelagic fish, contrasting sharply with steady or increasing concentrations in Antarctic benthic organisms. Transfer of contaminants between Antarctic pelagic and benthic food webs is associated with seasonal sea-ice dynamics which may influence the balance between the final receptors of contaminants under different climatic conditions. This complicates the predictability of future trends of emerging compounds in the Antarctic ecosystem, such as of the brominated compounds that we detected in Antarctic petrels. The discrepancy in trends between pelagic and benthic organisms shows that Antarctic biota are still final receptors of globally released organic contaminants and it remains questionable whether the total environmental burden of contaminants in the Antarctic ecosystem is declining. Copyright © 2010 Elsevier Ltd. All rights reserved.

  10. Environmental contamination in Antarctic ecosystems.

    Science.gov (United States)

    Bargagli, R

    2008-08-01

    Although the remote continent of Antarctica is perceived as the symbol of the last great wilderness, the human presence in the Southern Ocean and the continent began in the early 1900s for hunting, fishing and exploration, and many invasive plant and animal species have been deliberately introduced in several sub-Antarctic islands. Over the last 50 years, the development of research and tourism have locally affected terrestrial and marine coastal ecosystems through fuel combustion (for transportation and energy production), accidental oil spills, waste incineration and sewage. Although natural "barriers" such as oceanic and atmospheric circulation protect Antarctica from lower latitude water and air masses, available data on concentrations of metals, pesticides and other persistent pollutants in air, snow, mosses, lichens and marine organisms show that most persistent contaminants in the Antarctic environment are transported from other continents in the Southern Hemisphere. At present, levels of most contaminants in Antarctic organisms are lower than those in related species from other remote regions, except for the natural accumulation of Cd and Hg in several marine organisms and especially in albatrosses and petrels. The concentrations of organic pollutants in the eggs of an opportunistic top predator such as the south polar skua are close to those that may cause adverse health effects. Population growth and industrial development in several countries of the Southern Hemisphere are changing the global pattern of persistent anthropogenic contaminants and new classes of chemicals have already been detected in the Antarctic environment. Although the Protocol on Environmental Protection to the Antarctic Treaty provides strict guidelines for the protection of the Antarctic environment and establishes obligations for all human activity in the continent and the Southern Ocean, global warming, population growth and industrial development in countries of the Southern

  11. Role of the Tropical Pacific in recent Antarctic Sea-Ice Trends

    Science.gov (United States)

    Codron, F.; Bardet, D.; Allouache, C.; Gastineau, G.; Friedman, A. R.; Douville, H.; Voldoire, A.

    2017-12-01

    The recent (up to 2016) trends in Antarctic sea-ice cover - a global increase masking a dipole between the Ross and Bellingshausen-Weddel seas - are still not well understood, and not reproduced by CMIP5 coupled climate models. We here explore the potential role of atmospheric circulation changes around the Amundsen Sea, themselves possibly forced by tropical SSTs, an explanation that has been recently advanced. As a first check on this hypothesis, we compare the atmospheric circulation trends simulated by atmospheric GCMs coupled with an ocean or with imposed SSTs (AMIP experiment from CMIP5); the latter being in theory able to reproduce changes caused by natural SST variability. While coupled models simulate in aggregate trends that project on the SAM structure, strongest in summer, the AMIP simulations add in the winter season a pronounced Amundsen Sea Low signature (and a PNA signature in the northern hemisphere) both consistent with a Niña-like trend in the tropical Pacific. We then use a specific coupled GCM setup, in which surface wind anomalies over the tropical Pacific are strongly nudged towards the observed ones, including their interannual variability, but the model is free to evolve elsewhere. The two GCMs used then simulate a deepening trend in the Amundsen-Sea Low in winter, and are able to reproduce a dipole in sea-ice cover. Further analysis shows that the sea-ice dipole is partially forced by surface heat flux anomalies in early winter - the extent varying with the region and GCM used. The turbulent heat fluxes then act to damp the anomalies in late winter, which may however be maintained by ice-albedo feedbacks.

  12. Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.

    Science.gov (United States)

    Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun

    2014-01-23

    In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change.

  13. Evaluating Wind Power Potential in the Spanish Antarctic Base (BAE)

    International Nuclear Information System (INIS)

    Arribas, L.M.; Garcia Barquero, C; Navarro, J.; Cuerva, A.; Cruz, I.; Roque, V.; Marti, I.

    2000-01-01

    The objective of the work is to model wind field in the surroundings of the Spanish Antarctic Base (BAE in the following). The need of such a work comes from the necessity of an energy source able to supply the energy demand in the BAE during the Antarctic winter. When the BAE is in operation (in the Antarctic summer) the energy supply comes from a diesel engine. In the Antarctic winter the base is closed, but the demand of energy supply is growing up every year because of the increase in the number of technical and scientific machines that remain in the BAE taking different measurements. For this purpose the top of a closed hill called Pico Radio, not perturbed by close obstacles, has been chosen as the better site for the measurements. The measurement station is made up with a sonic anemometer and a small wind generator to supply the energy needed by the sensors head heating of the anemometer. This way, it will be also used as a proof for the suitability of a wind generator in the new chosen site, under those special climatic conditions.(Author) 3 refs

  14. Antarctic radiation exposure doubles

    Science.gov (United States)

    Blue, Charles

    New data reveal that the Antarctic Peninsula received twice its normal maximum dose of hazardous solar ultraviolet radiation in December 1990. The prolonged persistence of the ozone hole over Antarctica caused an increased exposure of radiation, according to a paper published in the October issue of Geophysical Research Letters.John Frederick and Amy D. Alberts of the University of Chicago calculated the amount of ultraviolet solar spectral radiation from data collected at Palmer Station, Antarctica. During the spring of 1990 the largest observed values for ultraviolet radiation were approximately double the values expected, based on previous years. “The measurements from Palmer Station are consistent with similar data from McMurdo Sound, where a factor of three [ultraviolet radiation] enhancement was recorded, according to work by Knut Stamnes and colleagues at the University of Alaska,” Frederick said. “The radiation levels observed over Palmer Station in December 1990 may be the largest experienced in this region of the world since the development of the Earth's ozone layer,” he added.

  15. Regulating Antarctic Tourism and the Precautionary Principle

    NARCIS (Netherlands)

    Bastmeijer, C.J.; Roura, R.

    2004-01-01

    On the basis of an overview of the developments in Antarctic tourism since 1956, this current development note examines the issue of international regulation of Antarctic tourism. After discussing one of the main management issues in respect of Antarctic tourism ¿ the assessment and prevention of

  16. Antarctic analogs for Enceladus

    Science.gov (United States)

    Murray, A. E.; Andersen, D. T.; McKay, C. P.

    2014-12-01

    Enceladus is a new world for Astrobiology. The Cassini discovery of the icy plume emanating from the South Polar region indicates an active world, where detection of water, organics, sodium, and nano-particle silica in the plume strongly suggests that the source is a subsurface salty ocean reservoir. Recent gravity data from Cassini confirms the presence of a regional sea extending north to 50°S. An ocean habitat under a thick ice cover is perhaps a recurring theme in the Outer Solar System, but what makes Enceladus unique is that the plume jetting out into space is carrying samples of this ocean. Therefore, through the study of Enceladus' plumes we can gain new insights not only of a possible habitable world in the Solar Systems, but also about the formation and evolution of other icy-satellites. Cassini has been able to fly through this plume - effectively sampling the ocean. It is time to plan for future missions that do more detailed analyses, possibly return samples back to Earth and search for evidence of life. To help prepare for such missions, the need for earth-based analog environments is essential for logistical, methodological (life detection) and theoretical development. We have undertaken studies of two terrestrial environments that are close analogs to Enceladus' ocean: Lake Vida and Lake Untersee - two ice-sealed Antarctic lakes that represent physical, chemical and possibly biological analogs for Enceladus. By studying the diverse biology and physical and chemical constraints to life in these two unique lakes we will begin to understand the potential habitability of Enceladus and other icy moons, including possible sources of nutrients and energy, which together with liquid water are the key ingredients for life. Analog research such as this will also enable us to develop and test new strategies to search for evidence of life on Enceladus.

  17. Surface melt on Antarctic ice shelves driven by wind-albedo interactions

    Science.gov (United States)

    Lhermitte, Stef; Lenaerts, Jan

    2017-04-01

    Surface melt and subsequent firn air depletion is considered an important precursor for disintegration of Antarctic ice shelves, causing grounded glaciers to accelerate and sea level to rise. Recent studies have highlighted the impact of surface winds on Antarctic ice shelf melt, both on the Antarctic Peninsula and in East Antarctica. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line, which in the recent past has led to the disintegration of the most northerly ice shelves. On the East Antarctic ice shelves, on the other hand, meltwater-induced firn air depletion is found in the grounding zone as result of persistent katabatic winds, regionally warming the atmosphere and inducing a melt-albedo feedback. Here, we use a combination multi-source satellite imagery, snow modelling, climate model output and in-situ observations to highlight the importance of this wind-induced melt and to show its widespread occurrence across Antarctica. The satellite imagery gives insight in the meltwater drainage systems, showing spatio-temporal changes in both supraglacial and englacial water throughout the melt season and during the subsequent winter. Although the wind-induced melt is a regional phenomenon with strong inter-annual variability, it is strongly correlated to larger scale climate parameters, such as summer surface temperature. Based on these correlations and snow model output driven by future climate scenarios, we can constrain the future changes to this local melt near the grounding line.

  18. Analysis on variability and trend in Antarctic sea ice albedo between 1983 and 2009

    Science.gov (United States)

    Seo, Minji; Kim, Hyun-cheol; Choi, Sungwon; Lee, Kyeong-sang; Han, Kyung-soo

    2017-04-01

    Sea ice is key parameter in order to understand the cryosphere climate change. Several studies indicate the different trend of sea ice between Antarctica and Arctic. Albedo is important factor for understanding the energy budget and factors for observing of environment changes of Cryosphere such as South Pole, due to it mainly covered by ice and snow with high albedo value. In this study, we analyzed variability and trend of long-term sea ice albedo data to understand the changes of sea ice over Antarctica. In addiction, sea ice albedo researched the relationship with Antarctic oscillation in order to determine the atmospheric influence. We used the sea ice albedo data at The Satellite Application Facility on Climate Monitoring and Antarctic Oscillation data at NOAA Climate Prediction Center (CPC). We analyzed the annual trend in albedo using linear regression to understand the spatial and temporal tendency. Antarctic sea ice albedo has two spatial trend. Weddle sea / Ross sea sections represent a positive trend (0.26% ˜ 0.04% yr-1) and Bellingshausen Amundsen sea represents a negative trend (- 0.14 ˜ -0.25%yr-1). Moreover, we performed the correlation analysis between albedo and Antarctic oscillation. As a results, negative area indicate correlation coefficient of - 0.3639 and positive area indicates correlation coefficient of - 0.0741. Theses results sea ice albedo has regional trend according to ocean. Decreasing sea ice trend has negative relationship with Antarctic oscillation, its represent a possibility that sea ice influence atmospheric factor.

  19. Expanding Antarctic Sea Ice: Anthropogenic or Natural Variability?

    Science.gov (United States)

    Bitz, C. M.

    2016-12-01

    Antarctic sea ice extent has increased over the last 36 years according to the satellite record. Concurrent with Antarctic sea-ice expansion has been broad cooling of the Southern Ocean sea-surface temperature. Not only are Southern Ocean sea ice and SST trends at odds with expectations from greenhouse gas-induced warming, the trend patterns are not reproduced in historical simulations with comprehensive global climate models. While a variety of different factors may have contributed to the observed trends in recent decades, we propose that it is atmospheric circulation changes - and the changes in ocean circulation they induce - that have emerged as the most likely cause of the observed Southern Ocean sea ice and SST trends. I will discuss deficiencies in models that could explain their incorrect response. In addition, I will present results from a series of experiments where the Antarctic sea ice and ocean are forced by atmospheric perturbations imposed within a coupled climate model. Figure caption: Linear trends of annual-mean SST (left) and annual-mean sea-ice concentration (right) over 1980-2014. SST is from NOAA's Optimum Interpolation SST dataset (version 2; Reynolds et al. 2002). Sea-ice concentration is from passive microwave observations using the NASA Team algorithm. Only the annual means are shown here for brevity and because the signal to noise is greater than in the seasonal means. Figure from Armour and Bitz (2015).

  20. Velocities of antarctic outlet glaciers determined from sequential Landsat images

    Science.gov (United States)

    MacDonald, Thomas R.; Ferrigno, Jane G.; Williams, Richard S.; Lucchitta, Baerbel K.

    1989-01-01

    Approximately 91.0 percent of the volume of present-day glacier ice on Earth is in Antarctica; Greenland contains about another 8.3 percent of the volume. Thus, together, these two great ice sheets account for an estimated 99.3 percent of the total. Long-term changes in the volume of glacier ice on our planet are the result of global climate change. Because of the relationship of global ice volume to sea level (± 330 cubic kilometers of glacier ice equals ± 1 millimeter sea level), changes in the mass balance of the antarctic ice sheet are of particular importance.Whether the mass balance of the east and west antarctic ice sheets is positive or negative is not known. Estimates of mass input by total annual precipitation for the continent have been made from scattered meteorological observations (Swithinbank 1985). The magnitude of annual ablation of the ice sheet from calving of outlet glaciers and ice shelves is also not well known. Although the velocities of outlet glaciers can be determined from field measurements during the austral summer,the technique is costly, does not cover a complete annual cycle,and has been applied to just a few glaciers. To increase the number of outlet glaciers in Antarctica for which velocities have been determined and to provide additional data for under-standing the dynamics of the antarctic ice sheets and their response to global climate change, sequential Landsat image of several outlet glaciers were measured.

  1. Genome-wide signatures of flowering adaptation to climate temperature: regional analyses in a highly diverse native range of Arabidopsis thaliana.

    Science.gov (United States)

    Tabas-Madrid, Daniel; Méndez-Vigo, Belén; Arteaga, Noelia; Marcer, Arnald; Pascual-Montano, Alberto; Weigel, Detlef; Xavier Picó, F; Alonso-Blanco, Carlos

    2018-03-08

    Current global change is fueling an interest to understand the genetic and molecular mechanisms of plant adaptation to climate. In particular, altered flowering time is a common strategy for escape from unfavorable climate temperature. In order to determine the genomic bases underlying flowering time adaptation to this climatic factor, we have systematically analysed a collection of 174 highly diverse A. thaliana accessions from the Iberian Peninsula. Analyses of 1.88 million SNPs provide evidence for a spatially heterogeneous contribution of demographic and adaptive processes to geographic patterns of genetic variation. Mountains appear to be allele dispersal barriers, whereas the relationship between flowering time and temperature depended on the precise temperature range. Environmental genome-wide associations (EGWA) supported an overall genome adaptation to temperature, with 9.4% of the genes showing significant associations. Furthermore, phenotypic genome-wide associations (PGWA) provided a catalogue of candidate genes underlying flowering time variation. Finally, comparison of EGWA and PGWA genomic regions identified known (TSF, FRL1 and CKB1) and new (ESM1 and VDAC5) genes as candidates for adaptation to climate temperature by altered flowering time. Thus, this regional collection provides an excellent resource to address the spatial complexity of climate adaptation in annual plants. This article is protected by copyright. All rights reserved.

  2. Antarctic grounding-line migration

    Science.gov (United States)

    Slater, T.; Konrad, H.; Shepherd, A.; Gilbert, L.; Hogg, A.; McMillan, M.; Muir, A. S.

    2017-12-01

    Knowledge of grounding-line position is critical for quantifying ice discharge into the ocean, as a boundary condition for numerical models of ice flow, and as an indicator of ice sheet stability. Although geological investigations have documented extensive grounding-line retreat since the period of the Last Glacial Maximum, observations of grounding line migration during the satellite era are restricted to a handful of locations. We combine satellite altimeter observations of ice-elevation change and airborne measurements of ice geometry to track movement of the Antarctic Ice Sheet grounding line. Based on these data, we estimate that 22%, 3%, and 10% of the West Antarctic, East Antarctic, and Antarctic Peninsula ice sheet grounding lines are retreating at rates faster than the typical pace since the Last Glacial Maximum, and that the continent loses over 200 km2 of grounded-ice area per year. Although by far the fastest rates of retreat occurred in the Amundsen Sea Sector, the Pine Island Glacier grounding line has stabilized - likely as a consequence of abated ocean forcing during the survey period.

  3. Antarctic sea ice losses drive gains in benthic carbon drawdown.

    Science.gov (United States)

    Barnes, D K A

    2015-09-21

    Climate forcing of sea-ice losses from the Arctic and West Antarctic are blueing the poles. These losses are accelerating, reducing Earth's albedo and increasing heat absorption. Subarctic forest (area expansion and increased growth) and ice-shelf losses (resulting in new phytoplankton blooms which are eaten by benthos) are the only significant described negative feedbacks acting to counteract the effects of increasing CO2 on a warming planet, together accounting for uptake of ∼10(7) tonnes of carbon per year. Most sea-ice loss to date has occurred over polar continental shelves, which are richly, but patchily, colonised by benthic animals. Most polar benthos feeds on microscopic algae (phytoplankton), which has shown increased blooms coincident with sea-ice losses. Here, growth responses of Antarctic shelf benthos to sea-ice losses and phytoplankton increases were investigated. Analysis of two decades of benthic collections showed strong increases in annual production of shelf seabed carbon in West Antarctic bryozoans. These were calculated to have nearly doubled to >2x10(5) tonnes of carbon per year since the 1980s. Annual production of bryozoans is median within wider Antarctic benthos, so upscaling to include other benthos (combined study species typically constitute ∼3% benthic biomass) suggests an increased drawdown of ∼2.9x10(6) tonnes of carbon per year. This drawdown could become sequestration because polar continental shelves are typically deeper than most modern iceberg scouring, bacterial breakdown rates are slow, and benthos is easily buried. To date, most sea-ice losses have been Arctic, so, if hyperboreal benthos shows a similar increase in drawdown, polar continental shelves would represent Earth's largest negative feedback to climate change. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Science of Signatures Workshop on Secondary Ion Mass Spectrometry (SIMS) Applications July 24, 2012

    Energy Technology Data Exchange (ETDEWEB)

    Hickmott, Donald D [Los Alamos National Laboratory; Riciputi, Lee D [Los Alamos National Laboratory

    2012-07-23

    The science of signatures focus areas are: (1) Radiological and Nuclear; (2) Chemical and Materials (including explosives); (3) Biological - Signatures of Disease and Health; (4) Energy; (5) Climate; and (6) Space.

  5. Low Signature Tent Structures

    National Research Council Canada - National Science Library

    Cox, Randy

    1998-01-01

    .... Modeling shows that visual, near infrared, thermal, and radar signatures should be reduced when compared to other current tent designs. A brief treatise on the role of tent signatures and their results is included.

  6. Functional ecology of an Antarctic Dry Valley

    Science.gov (United States)

    Chan, Yuki; Van Nostrand, Joy D.; Zhou, Jizhong; Pointing, Stephen B.

    2013-01-01

    The McMurdo Dry Valleys are the largest ice-free region in Antarctica and are critically at risk from climate change. The terrestrial landscape is dominated by oligotrophic mineral soils and extensive exposed rocky surfaces where biota are largely restricted to microbial communities, although their ability to perform the majority of geobiological processes has remained largely uncharacterized. Here, we identified functional traits that drive microbial survival and community assembly, using a metagenomic approach with GeoChip-based functional gene arrays to establish metabolic capabilities in communities inhabiting soil and rock surface niches in McKelvey Valley. Major pathways in primary metabolism were identified, indicating significant plasticity in autotrophic, heterotrophic, and diazotrophic strategies supporting microbial communities. This represents a major advance beyond biodiversity surveys in that we have now identified how putative functional ecology drives microbial community assembly. Significant differences were apparent between open soil, hypolithic, chasmoendolithic, and cryptoendolithic communities. A suite of previously unappreciated Antarctic microbial stress response pathways, thermal, osmotic, and nutrient limitation responses were identified and related to environmental stressors, offering tangible clues to the mechanisms behind the enduring success of microorganisms in this seemingly inhospitable terrain. Rocky substrates exposed to larger fluctuations in environmental stress supported greater functional diversity in stress-response pathways than soils. Soils comprised a unique reservoir of genes involved in transformation of organic hydrocarbons and lignin-like degradative pathways. This has major implications for the evolutionary origin of the organisms, turnover of recalcitrant substrates in Antarctic soils, and predicting future responses to anthropogenic pollution. PMID:23671121

  7. Variations of the Antarctic Circumpolar Current (ACC) in the Kerguelen Sector during the Last Deglaciation : sedimentological and geochemical evidences

    Science.gov (United States)

    Bout-Roumazeilles, V.; Beny, F.; Mazaud, A.; Michel, E.; Crosta, X.; Davies, G. R.; Bory, A. J. M.

    2017-12-01

    High-resolution sedimentological and geochemical records were obtained from two sediment cores recovered by the French R/V Marion Dufresne during the INDIEN-SUD-ACC cruises near the sub-Antarctic Kerguelen Islands (49°S). This area is ideal to record past oceanic and atmospheric changes in the Southern Ocean because they are currently located in the northern branch of the Antarctic Circumpolar Current and under the direct influence of Southern Hemisphere Westerly wind belt. This study focuses on the last termination, with specific emphasis on the impact of severe climatic events (Heinrich Stadial 1, Antarctic Cold Reversal, Younger Dryas) onto the ocean-atmospheric exchange. Results indicates that most of the sediment is derived from the Kerguelen Plateau, characterized by high smectite content. Periodically, a minor contribution of Antarctica is noticeable. In particular, illite variations suggest fast and short northward incursions of Antarctic Bottom Water, probably formed in the Prydz Bay during the last glaciation. Grainsize repartition combined to magnetic parameters show a southward migration of the ACC and the fronts associated from the beginning of the deglaciation, which is consistent with Southern Hemisphere climate variations. On the opposite, it highlights an asynchronous decrease of the ACC strength, with a large drop during the Antarctic Cold Reversal when atmospheric CO2 increase was slowed down. Thus, at least in the studied area, the ACC strength and the Antarctic Climate were not synchronous during the last deglaciation.

  8. Deciphering human-climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500 years (Misten bog, Belgium)

    Science.gov (United States)

    Fagel, N.; Allan, M.; Le Roux, G.; Mattielli, N.; Piotrowska, N.; Sikorski, J.

    2014-06-01

    A high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD, 1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change. The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 periods characterised by dominant-distal sources (c. 320 AD, 1000 AD and 1700 AD) are consistent with local wetter-than-average intervals as indicated by a lower degree of peat humification. Local erosion prevails during the drier (higher humification) intervals (100 AD, 600 AD). On a global scale, more distal supplies are driven during colder periods, in particular during the Oort and Maunder minima, suggesting a potential link between dust deposition and global climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

  9. Responses of Antarctic Oscillation to global warming

    Science.gov (United States)

    Feng, S.

    2015-12-01

    The Antarctic Oscillation (AAO) is the major annular mode dominates the spatiotemporal variability of the atmospheric circulation in the Southern Hemisphere. This study examined the sensitivity of AAO to future warming by analyzing the outputs of 34 state-of-the-art climate models participating in phase 5 of the Coupled Model Intercomparion Project (CMIP5). The model simulations include the stabilized (RCP4.5) and business as usual (RCP8.5) scenarios as well as the idealized 1% per year increase in atmospheric CO2 to quadrupling (1pctCO2) and an instantaneous quadrupling of CO2 (abrupt4xCO2). We show that the CMIP5 models on average simulate increases in the AAO in every season by 2100 under the RCP4.5 and RCP8.5 scenarios. However, due to the impacts of ozone, aerosol and land use changes, the amplitudes of the projected changes in AAO to future climate scenarios are quit different on different seasons. After the impact of ozone, aerosol and land use changes were removed; it was found that the impact of greenhouse gases (GHGs) on AAO is similar on all seasons. The increases of AAO are accelerating following the increase of GHGs. Our results are also consistent with the simulations of 1pctCO2 and abrupt4xCO2.

  10. Serum chemistry and antibodies against pathogens in antarctic fur seals, Weddell seals, crabeater seals, and Ross seals.

    Science.gov (United States)

    Tryland, Morten; Nymo, Ingebjørg H; Nielsen, Ole; Nordøy, Erling S; Kovacs, Kit M; Krafft, Bjørn A; Thoresen, Stein I; Åsbakk, Kjetil; Osterrieder, Klaus; Roth, Swaantje J; Lydersen, Christian; Godfroid, Jacques; Blix, Arnoldus S

    2012-07-01

    Information on health parameters, such as antibody prevalences and serum chemistry that can reveal exposure to pathogens, disease, and abnormal physiologic conditions, is scarce for Antarctic seal species. Serum samples from Antarctic fur seals (Arctocephalus gazella, n=88) from Bouvetøya (2000-2001 and 2001-2002), and from Weddell seals (Leptonychotes weddellii, n=20), Ross seals (Ommatophoca rossii, n=20), and crabeater seals (Lobodon carcinophagus, n=9) from the pack-ice off Queen Maud Land, Antarctica (2001) were analyzed for enzyme activity, and concentrations of protein, metabolites, minerals, and cortisol. Adult Antarctic fur seal males had elevated levels of total protein (range 64-99 g/l) compared to adult females and pups (range 52-79 g/l). Antarctic fur seals had higher enzyme activities of creatine kinase, lactate dehydrogenase, and amylase, compared to Weddell, Ross, and crabeater seals. Antibodies against Brucella spp. were detected in Weddell seals (37%), Ross seals (5%), and crabeater seals (11%), but not in Antarctic fur seals. Antibodies against phocine herpesvirus 1 were detected in all species examined (Antarctic fur seals, 58%; Weddell seals, 100%; Ross seals, 15%; and crabeater seals, 44%). No antibodies against Trichinella spp., Toxoplasma, or phocine distemper virus (PDV) were detected (Antarctic fur seals were not tested for PDV antibodies). Antarctic seals are challenged by reduced sea ice and increasing temperatures due to climate change, and increased anthropogenic activity can introduce new pathogens to these vulnerable ecosystems and represent a threat for these animals. Our data provide a baseline for future monitoring of health parameters of these Antarctic seal species, for tracking the impact of environmental, climatic, and anthropogenic changes in Antarctica over time.

  11. Feedbacks of lithosphere dynamics and environmental change of the Cenozoic West Antarctic Rift System.

    NARCIS (Netherlands)

    van der Wateren, F.M.; Cloetingh, S.A.P.L.

    1999-01-01

    This special issue of Global and Planetary Change contains 11 contributions dealing with various aspects of the Cenozoic West Antarctic Rift System. During the last two decades, investigations of the interplay of tectonics and climate greatly improved understanding of Cenozoic global change. Major

  12. Effects of global warming on Antarctic soil microorganisms and associated functions

    NARCIS (Netherlands)

    Yergeau, E.

    2008-01-01

    Summary Soil microorganisms are involved in all the major global biogeochemical cycles, but consequences of ongoing climate changes on these organisms and associated functions are mostly unknown. Antarctic terrestrial habitats are ideal testing grounds for the impacts of perturbation on soil

  13. Polar lessons learned: long-term management based on shared threats in Arctic and Antarctic environments

    NARCIS (Netherlands)

    Bennett, J.R.; Shaw, J.D.; Terauds, A.; Smol, J.P.; Aerts, R.; Bergstrom, D.M.; Blais, J.M.; Cheung, W.W.L.; Chown, S.L.; Lea, M.-A.; Nielsen, U.N.; Pauly, D.; Reimer, K.J.; Riddle, M.J.; Snape, I.; Stark, J.S.; Tulloch, V.J.; Possingham, H.P.

    2015-01-01

    The Arctic and Antarctic polar regions are subject to multiple environmental threats, arising from both local and ex-situ human activities. We review the major threats to polar ecosystems including the principal stressor, climate change, which interacts with and exacerbates other threats such as

  14. FjordPhyto: Antarctic Citizen Science Project

    OpenAIRE

    Lee Cusick, Allison

    2017-01-01

    The FjordPhyto Citizen Science project is designed to engage the International Association of Antarctic Tour Operators and their Guests in hands-on science as they journey along the fjords of the west Antarctic Peninsula. The Antarctic Peninsula is one of the fastest warming regions in the world. Melting glaciers bring an influx of freshwater and nutrients into the fjords potentially altering the biology at the phytoplankton level. Phytoplankton play a critical role in regulating the atmosphe...

  15. Environmental Factors Influencing Antarctic Krill Recruitment along the Western Antarctic Peninsula

    Science.gov (United States)

    Cope, J. S.; Steinberg, D. K.; Thanassekos, S.

    2016-02-01

    Climate warming in the Western Antarctic Peninsula (WAP) is impacting pelagic food web structure. Antarctic krill, Euphausia superba, are a critical food-web link between primary producers and higher trophic levels such as penguins, seals, and whales. Climate-induced changes in krill recruitment are thus an important consideration when evaluating future WAP ecosystem trends. We examined long-term (1993 to 2015) and spatial (north/south) changes in summer krill recruitment. Krill were collected within the epipelagic zone during the Palmer Antarctica Long-Term Ecological Research (PAL LTER) cruises within a 700 x 260 km sampling grid along the WAP. Krill from each tow were enumerated and their lengths were measured. A simple recruitment index based on the proportion of krill smaller than 40 mm (F40) was used in our analyses. There was a significant 5-6-year cyclical trend in F40. In the last 5 years, the southern population has begun to deviate from this cycle. To investigate potential environmental factors leading to this pattern in recruitment success, F40 was regressed with environmental factors and climatological indices for both the whole PAL LTER grid and north/south sub-regions. Over the whole grid, F40 was positively correlated with chlorophyll a and primary production, both with a 1-year lag. Spatially, these trends were strongest for chlorophyll in the north, and primary production in the south. Krill recruitment in the south was also correlated to climatological indices such as the Multivariate El Niño/Southern Oscillation Index (MEI). These correlations could be used to forecast future krill population changes.

  16. ‘New’ Antarctic volcanos

    Science.gov (United States)

    Two previously unknown volcanos that show evidence o f recent eruptions were discovered in March on the east side of the Antarctic Peninsula, according to the National Science Foundation. The discovery brings to five the number of known active volcanos on the continent.Volcanic debris still covers a large swath of the adjacent Larsen Ice Shelf, pointing to very recent activity. In addition, one of the volcanos was steaming when the discovery was made, reports Oscar Gonzalez-Ferran of the University of Chile at Santiago. He made the discovery while doing a geophysical survey by helicopter of the Antarctic Peninsula. The two volcanos constitute the southernmost extension of the eastern side of the ‘ring of fire,’ a ring of volcanos that is believed to mark the active subduction zone on the periphery of the Pacific Ocean.

  17. AGU honored for Antarctic book

    Science.gov (United States)

    AGU has won an honorable mention award at the Fifteenth Annual Awards Program for Excellence in Professional and Scholarly Publishing sponsored by the Association of American Publishers for the book Volcanoes of the Antarctic Plate and Southern Oceans. The book is part of AGU's Antarctic Research Series, an outgrowth of research done during the International Geophysical Year that was begun in 1963 with a grant from the National Science Foundation. The award was presented at the AAP Annual Awards Dinner on February 6 at the Ritz-Carlton Hotel in Washington, D.C. The award consists of a medallion and a plate on which the names of the publisher, title, and authors are engraved.

  18. Sudden increase in Antarctic sea ice: Fact or artifact?

    Science.gov (United States)

    Screen, J. A.

    2011-07-01

    Three sea ice data sets commonly used for climate research display a large and abrupt increase in Antarctic sea ice area (SIA) in recent years. This unprecedented change of SIA is diagnosed to be primarily caused by an apparent sudden increase in sea ice concentrations within the ice pack, especially in the area of the most-concentrated ice (greater than 95% concentration). A series of alternative satellite-derived records do not display any abnormal sudden SIA changes, but do reveal substantial discrepancies between different satellite sensors and sea ice algorithms. Sea ice concentrations in the central ice pack and SIA values derived from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSRE) are consistently greater than those derived from the Special Sensor Microwave Imager (SSMI). A switch in source data from the SSMI to AMSRE in mid-2009 explains most of the SIA increase in all three affected data sets. If uncorrected for, the discontinuity artificially exaggerates the winter Antarctic SIA increase (1979-2010) by more than a factor of 2 and the spring trend by almost a factor of 4. The discontinuity has a weaker influence on the summer and autumn SIA trends, on calculations of Antarctic sea ice extent, and in the Arctic.

  19. Air-sea interaction regimes in the sub-Antarctic Southern Ocean and Antarctic marginal ice zone revealed by icebreaker measurements

    Science.gov (United States)

    Yu, Lisan; Jin, Xiangze; Schulz, Eric W.; Josey, Simon A.

    2017-08-01

    Antarctic continents and provide critical support for Australia's Southern Ocean research operation. Automated meteorological measurement systems are deployed onboard the vessel, providing routine observations of wind, air and sea temperature, humidity, pressure, precipitation and long- and short-wave radiation. Two climatically important regimes are sampled as the icebreaker sails across the sub-Antarctic Southern Ocean and traverses the marginal region of the East Antarctic continent. One regime is the Antarctic Circumpolar Current (ACC) system where strong westerly winds are featured. The other is the Antarctic seasonal marginal ice zone (MIZ), i.e., the narrow transition zone that connects the ice-free sub-Antarctic with the Antarctic ice-covered regime. Observing the remote Southern Ocean has been historically challenging due to the cost realities and logistical difficulties. The shipboard and near-surface meteorological measurements offer a rare and valuable opportunity for gaining an in situ insight into the air-sea heat and momentum exchange in two poorly sampled yet dynamically important regimes.

  20. Heavy metals in Antarctic organisms

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, J.E.A. de; Moreno, V.J. [Universidad Nacional de Mar del Plata (Argentina); Gerpe, M.S.; Vodopivez, C. [Instituto Antartico Argentino, Buenos Aires (Argentina)

    1997-02-01

    To evaluate levels of essential (zinc and copper) and non-essential (mercury and cadmium) heavy metals, 34 species of organisms from different areas close to the Antarctic Peninsula were analysed. These included algae, filter-feeders, omnivorous invertebrates and vertebrates. Mercury was not detected, while cadmium was found in the majority of organisms analysed (detection limit was 0.05 ppm for both metals). The highest cadmium concentration was observed in the starfish Odontaster validus. Anthozoans, sipunculids and nudibranchs showed maximum levels of zinc, while the highest copper level was found in the gastropod Trophon brevispira. Mercury and cadmium levels in fishes were below the detection limit. Concentrations of essential and non-essential metals in birds were highest in liver followed by muscle and eggs. Cadmium and mercury levels in muscle of southern elephant seals were above the detection limit, whereas in Antarctic fur seals they were below it. The objective of the study was to gather baseline information for metals in Antarctic Ocean biota that may be needed to detect, measure and monitor future environmental changes. 46 refs., 7 figs., 8 tabs.

  1. Antarctic skuas recognize individual humans.

    Science.gov (United States)

    Lee, Won Young; Han, Yeong-Deok; Lee, Sang-Im; Jablonski, Piotr G; Jung, Jin-Woo; Kim, Jeong-Hoon

    2016-07-01

    Recent findings report that wild animals can recognize individual humans. To explain how the animals distinguish humans, two hypotheses are proposed. The high cognitive abilities hypothesis implies that pre-existing high intelligence enabled animals to acquire such abilities. The pre-exposure to stimuli hypothesis suggests that frequent encounters with humans promote the acquisition of discriminatory abilities in these species. Here, we examine individual human recognition abilities in a wild Antarctic species, the brown skua (Stercorarius antarcticus), which lives away from typical human settlements and was only recently exposed to humans due to activities at Antarctic stations. We found that, as nest visits were repeated, the skua parents responded at further distances and were more likely to attack the nest intruder. Also, we demonstrated that seven out of seven breeding pairs of skuas selectively responded to a human nest intruder with aggression and ignored a neutral human who had not previously approached the nest. The results indicate that Antarctic skuas, a species that typically inhabited in human-free areas, are able to recognize individual humans who disturbed their nests. Our findings generally support the high cognitive abilities hypothesis, but this ability can be acquired during a relatively short period in the life of an individual as a result of interactions between individual birds and humans.

  2. State of the Antartic climate system Excerpts from SASOCS (Mayewski et al. 2009)

    OpenAIRE

    Mayewski,Paul Andrew

    2012-01-01

    Two recently released reports document the past, present and future predictions for climate over the Antarctic and the Southern Ocean. From these syntheses it is clear that the Antarctic plays a critical role in hemispheric to regional climate change and that in recent times human activities are beginning to have a marked impact on Antarctic temperature, precipitation, atmospheric circulation, ocean circulation, sea ice extent and chemistry of the atmosphere.

  3. WHY ARE THERE SO MANY SPECIES OF BROODING ANTARCTIC ECHINOIDS?

    Science.gov (United States)

    Poulin, Élie; Féral, Jean-Pierre

    1996-04-01

    between planktotrophic and brooding species in relation with the climatic history of the Antarctic. © 1996 The Society for the Study of Evolution.

  4. Antarctic krill 454 pyrosequencing reveals chaperone and stress transcriptome.

    Directory of Open Access Journals (Sweden)

    Melody S Clark

    Full Text Available BACKGROUND: The Antarctic krill Euphausia superba is a keystone species in the Antarctic food chain. Not only is it a significant grazer of phytoplankton, but it is also a major food item for charismatic megafauna such as whales and seals and an important Southern Ocean fisheries crop. Ecological data suggest that this species is being affected by climate change and this will have considerable consequences for the balance of the Southern Ocean ecosystem. Hence, understanding how this organism functions is a priority area and will provide fundamental data for life history studies, energy budget calculations and food web models. METHODOLOGY/PRINCIPAL FINDINGS: The assembly of the 454 transcriptome of E. superba resulted in 22,177 contigs with an average size of 492bp (ranging between 137 and 8515bp. In depth analysis of the data revealed an extensive catalogue of the cellular chaperone systems and the major antioxidant proteins. Full length sequences were characterised for the chaperones HSP70, HSP90 and the super-oxide dismutase antioxidants, with the discovery of potentially novel duplications of these genes. The sequence data contained 41,470 microsatellites and 17,776 Single Nucleotide Polymorphisms (SNPs/INDELS, providing a resource for population and also gene function studies. CONCLUSIONS: This paper details the first 454 generated data for a pelagic Antarctic species or any pelagic crustacean globally. The classical "stress proteins", such as HSP70, HSP90, ferritin and GST were all highly expressed. These genes were shown to be over expressed in the transcriptomes of Antarctic notothenioid fish and hypothesized as adaptations to living in the cold, with the associated problems of decreased protein folding efficiency and increased vulnerability to damage by reactive oxygen species. Hence, these data will provide a major resource for future physiological work on krill, but in particular a suite of "stress" genes for studies understanding

  5. Antarctic krill 454 pyrosequencing reveals chaperone and stress transcriptome.

    Science.gov (United States)

    Clark, Melody S; Thorne, Michael A S; Toullec, Jean-Yves; Meng, Yan; Guan, Le Luo; Peck, Lloyd S; Moore, Stephen

    2011-01-06

    The Antarctic krill Euphausia superba is a keystone species in the Antarctic food chain. Not only is it a significant grazer of phytoplankton, but it is also a major food item for charismatic megafauna such as whales and seals and an important Southern Ocean fisheries crop. Ecological data suggest that this species is being affected by climate change and this will have considerable consequences for the balance of the Southern Ocean ecosystem. Hence, understanding how this organism functions is a priority area and will provide fundamental data for life history studies, energy budget calculations and food web models. The assembly of the 454 transcriptome of E. superba resulted in 22,177 contigs with an average size of 492bp (ranging between 137 and 8515bp). In depth analysis of the data revealed an extensive catalogue of the cellular chaperone systems and the major antioxidant proteins. Full length sequences were characterised for the chaperones HSP70, HSP90 and the super-oxide dismutase antioxidants, with the discovery of potentially novel duplications of these genes. The sequence data contained 41,470 microsatellites and 17,776 Single Nucleotide Polymorphisms (SNPs/INDELS), providing a resource for population and also gene function studies. This paper details the first 454 generated data for a pelagic Antarctic species or any pelagic crustacean globally. The classical "stress proteins", such as HSP70, HSP90, ferritin and GST were all highly expressed. These genes were shown to be over expressed in the transcriptomes of Antarctic notothenioid fish and hypothesized as adaptations to living in the cold, with the associated problems of decreased protein folding efficiency and increased vulnerability to damage by reactive oxygen species. Hence, these data will provide a major resource for future physiological work on krill, but in particular a suite of "stress" genes for studies understanding marine ectotherms' capacities to cope with environmental change.

  6. Organic carbon in Antarctic snow: spatial trends and possible sources

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, R.; Mahalinganathan, K.; Thamban, M.; Nair, S.

    ,J.;vonGlasgow,R.;Weller,R.;Wolff,E.;Zhu,T.Anoverviewof snow photochemistry: Evidence, mechanisms and impacts. Atmos. Chem. Phys. 2007, 7, 4329–4373. (6) Priscu, J. C.; et al. Antarctic subglacial water: Origin, evolution, and ecology. In Polar Lakes and Rivers; Vincent, W. F., Laybourn-Parry, J., Eds...) Jaenicke, R. Atmospheric aerosols and global climate. J. Aerosol Sci. 1980, 11, 577–588. (26) Hodson, A.; Anesio, A. M.; Tranter, M.; Fountain, A.; Osborn, M.; Priscu, J.; Laybourn-Parry, J.; Sattler, B. Glacial ecosystems. Ecol. Monogr. 2008, 78 (1), 41...

  7. Miocene Antarctic Terrestrial Realm

    Science.gov (United States)

    Ashworth, A. C.; Lewis, A.; Marchant, D. R.

    2009-12-01

    alpine lake that formed behind a recessional moraine. The fossils are mostly those of freshwater organisms including numerous species of diatoms and an ostracod species in which the soft anatomy is preserved. The base of the lake is marked by a moss bed with exceptionally well-preserved stems and leaves of the extant species Drepanocladus longifolius. Pollen evidence from the Cape Roberts borehole in the Ross Sea basin suggests that tundra existed from the Oligocene to the Early Miocene. Fossil evidence from the Dry Valleys locations indicates that organisms that could not inhabit Antarctica today persisted until c. 14 Ma. At 14 Ma there was a shift in glacial regimes from wet- to cold-based, marking a profound and abrupt climatic shift. We hypothesize that this climate change from warmer and wetter to colder and drier conditions caused the extinction of the tundra biota. It seems probable that at least some of the mid-Miocene fossils are of organisms whose descendants evolved in Antarctica during the Paleogene or earlier. An important consequence of this hypothesis is that the Cenozoic climate of Antarctica was warm enough until the mid-Miocene to support vascular plants and insects. This research was funded by NSF OPP 0739693.

  8. Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination.

    Science.gov (United States)

    Fogwill, C J; Turney, C S M; Golledge, N R; Etheridge, D M; Rubino, M; Thornton, D P; Baker, A; Woodward, J; Winter, K; van Ommen, T D; Moy, A D; Curran, M A J; Davies, S M; Weber, M E; Bird, M I; Munksgaard, N C; Menviel, L; Rootes, C M; Ellis, B; Millman, H; Vohra, J; Rivera, A; Cooper, A

    2017-01-05

    Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000-11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved 'horizontal ice core' from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600-12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.

  9. Antarctic Wave Dynamics Mystery Discovered by Lidar, Radar and Imager

    Directory of Open Access Journals (Sweden)

    Chen Cao

    2016-01-01

    Full Text Available Since the start of the McMurdo Fe lidar campaign, largeamplitude (~±30 K, long-period (4 to 9 h waves with upward energy propagating signatures are frequently observed in the MLT temperatures. Despite its frequent appearance, such type of wave was neither widely observed nor well understood in the past. At McMurdo (77.8°S, 166.7°E, the simultaneous observations of such waves using lidar, radar and airglow imager can provide 3-D intrinsic wave-propagation properties, which are greatly needed for understanding their sources and potential impacts. This study presents the first coincident observation of these 4–9 h waves by lidar, radar and airglow imager in the Antarctic mesopause region.

  10. Environmental radioactivity in the antarctic station

    International Nuclear Information System (INIS)

    Gonzalez, S.; Osores, J.; Martinez, J.; Lopez, E.; Jara, R.

    1998-01-01

    Study about environmental radioactivity in the Peruvian antarctic station Machu Pichu they were carried out during the last three periods to the southern summer. The objective of the project it is to evaluate environmental component in order to elaborate a study it base on the levels background radioactivity and artificial in the antarctic region

  11. Carbon dioxide emissions of Antarctic tourism

    NARCIS (Netherlands)

    Farreny, R.; Oliver-Solà, J.; Lamers, M.A.J.; Amelung, B.; Gabarrell, X.; Rieradevall, J.; Boada, M.; Benayas, J.

    2011-01-01

    The increase of tourism to the Antarctic continent may entail not only local but also global environmental impacts. These latter impacts, which are mainly caused by transport, have been generally ignored. As a result, there is a lack of data on the global impacts of Antarctic tourism in terms of

  12. South African antarctic biological research programme

    CSIR Research Space (South Africa)

    SASCAR

    1981-07-01

    Full Text Available This document provides a description of the past, current and planned South African biological research activities in the sub-Antarctic and Antarctic regions. Future activities will fall under one of the five components of the research programme...

  13. The climatic out of control. the climatic forcing; L'emballement climatique. Le forcage climatique

    Energy Technology Data Exchange (ETDEWEB)

    Bony-Lena, S.; Dufresne, J.L. [Laboratoire de Meteorologie Dynamique, LMD/IPSL, CNRS-UPMC, 75 - Paris (France); Acot, P. [Institut d' histoire et de philosophie des sciences et des techniques (IHPST), CNRS-Univ. Paris-1-ENS, 75 - Paris (France); Friedlingstein, P. [CEA Saclay, Lab. des Sciences du Climat et l' Environnement (LSCE), 91 - Gif-sur-Yvette (France); Berger, A.; Loutre, M.L. [Universite Catholique de Louvain (UCL), Louvain-la-Neuve (Belgium). Inst. d' Astronomie et de Geophysique G. Lemaitre; Jouzel, J. [Institut Pierre Simon Laplace, 75 - Paris (France); Raynaud, D. [Laboratoire de Glaciologie et Geophysique de l' Environnement (UMR 5183), 38 - Saint Martin d' Heres cedex (France); Thuiller, W. [Universite Joseph-Fourier, Lab. d' Ecologie Alpine, CNRS-Univ. Grenoble-1, 38 (France); Le Treut, H. [Laboratoire de Meteorologie dynamique du CNRS, 75 - Paris (France); Houssais, M.N. [Laboratoire d' Oceanographie et du Climat Experimentation et Approches Numerique (LOCEAN / IPSL), 75 - Paris (France); Duplessy, J.C. [Centre National de la Recherche Scientifique, Laboratoire des Sciences du Climat et de l' Environnement (LSCE), 91 - Gif sur Yvette (France); Royer, J.F.; Douville, H. [Centre National de Recherches Meteorologiques, 31 - Toulouse (France); Barberousse, A. [Institut d' Histoire et de Philosophie des Sciences et des Techniques, CNRS, ENS, 75 - Paris (France); Quinon, P

    2007-03-15

    The expert group on the climate evolution affirms that the global warming is unequivocal and that the human being is the main responsible. This document broaches the climatic change under many aspects: the principle, the historical aspect of the greenhouse effect, the GIEC, the carbon cycle, the paleo-climate theory, the antarctic ices and the impacts of the climatic change on the biodiversity, the simulations and the models, the climatic indicators and the climatic forcing by human activities. (A.L.B.)

  14. Unconditionally Secure Quantum Signatures

    Directory of Open Access Journals (Sweden)

    Ryan Amiri

    2015-08-01

    Full Text Available Signature schemes, proposed in 1976 by Diffie and Hellman, have become ubiquitous across modern communications. They allow for the exchange of messages from one sender to multiple recipients, with the guarantees that messages cannot be forged or tampered with and that messages also can be forwarded from one recipient to another without compromising their validity. Signatures are different from, but no less important than encryption, which ensures the privacy of a message. Commonly used signature protocols—signatures based on the Rivest–Adleman–Shamir (RSA algorithm, the digital signature algorithm (DSA, and the elliptic curve digital signature algorithm (ECDSA—are only computationally secure, similar to public key encryption methods. In fact, since these rely on the difficulty of finding discrete logarithms or factoring large primes, it is known that they will become completely insecure with the emergence of quantum computers. We may therefore see a shift towards signature protocols that will remain secure even in a post-quantum world. Ideally, such schemes would provide unconditional or information-theoretic security. In this paper, we aim to provide an accessible and comprehensive review of existing unconditionally securesecure signature schemes for signing classical messages, with a focus on unconditionally secure quantum signature schemes.

  15. Radar Signature Calculation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: The calculation, analysis, and visualization of the spatially extended radar signatures of complex objects such as ships in a sea multipath environment and...

  16. ARM West Antarctic Radiation Experiment (AWARE) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Lubin, D [National Science Foundation; Bromwich, DH [Ohio State University; Russell, LM [Scripps Institution of Oceanography; Verlinde, J [The Pennsylvania State University; Vogelmann, AM [Brookhaven National Laboratory

    2015-10-01

    West Antarctica is one of the most rapidly warming regions on Earth, and this warming is closely connected with global sea level rise. The discovery of rapid climate change on the West Antarctic Ice Sheet (WAIS) has challenged previous explanations of Antarctic climate change that focused on strengthening of circumpolar westerlies in response to the positive polarity trend in the Southern Annular Mode. West Antarctic warming does not yet have a comprehensive explanation: dynamical mechanisms may vary from one season to the next, and these mechanisms very likely involve complex teleconnections with subtropical and tropical latitudes. The prime motivation for this proposal is that there has been no substantial atmospheric science or climatological field work on West Antarctica since the 1957 International Geophysical Year and that research continued for only a few years. Direct meteorological information on the WAIS has been limited to a few automatic weather stations for several decades, yet satellite imagery and meteorological reanalyses indicate that West Antarctica is highly susceptible to advection of warm and moist maritime air with related cloud cover, depending on the location and strength of low pressure cells in the Amundsen, Ross, and Bellingshausen Seas. There is a need to quantify the role of these changing air masses on the surface energy balance, including all surface energy components and cloud-radiative forcing. More generally, global climate model simulations are known to perform poorly over the Antarctic and Southern Oceans, and the marked scarcity of cloud information at southern high latitudes has so far inhibited significant progress. Fortunately, McMurdo Station, where the Atmospheric Radiation Measurement Facility’s (ARM’s) most advanced cloud and aerosol instrumentation is situated, has a meteorological relationship with the WAIS via circulation patterns in the Ross and Amundsen Seas. We can therefore gather sophisticated data with cloud

  17. The multi-millennial Antarctic commitment to future sea-level rise.

    Science.gov (United States)

    Golledge, N R; Kowalewski, D E; Naish, T R; Levy, R H; Fogwill, C J; Gasson, E G W

    2015-10-15

    Atmospheric warming is projected to increase global mean surface temperatures by 0.3 to 4.8 degrees Celsius above pre-industrial values by the end of this century. If anthropogenic emissions continue unchecked, the warming increase may reach 8-10 degrees Celsius by 2300 (ref. 2). The contribution that large ice sheets will make to sea-level rise under such warming scenarios is difficult to quantify because the equilibrium-response timescale of ice sheets is longer than those of the atmosphere or ocean. Here we use a coupled ice-sheet/ice-shelf model to show that if atmospheric warming exceeds 1.5 to 2 degrees Celsius above present, collapse of the major Antarctic ice shelves triggers a centennial- to millennial-scale response of the Antarctic ice sheet in which enhanced viscous flow produces a long-term commitment (an unstoppable contribution) to sea-level rise. Our simulations represent the response of the present-day Antarctic ice-sheet system to the oceanic and climatic changes of four representative concentration pathways (RCPs) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We find that substantial Antarctic ice loss can be prevented only by limiting greenhouse gas emissions to RCP 2.6 levels. Higher-emissions scenarios lead to ice loss from Antarctic that will raise sea level by 0.6-3 metres by the year 2300. Our results imply that greenhouse gas emissions in the next few decades will strongly influence the long-term contribution of the Antarctic ice sheet to global sea level.

  18. The multi-millennial Antarctic commitment to future sea-level rise

    Science.gov (United States)

    Golledge, Nicholas R.; Kowalewski, Douglas E.; Naish, Timothy R.; Levy, Richard H.; Fogwill, Christopher J.; Gasson, Edward G. W.

    2016-04-01

    Atmospheric warming is projected to increase global mean surface temperatures by 0.3 to 4.8 degrees Celsius above present values by the end of this century (Collins et al., 2013). If anthropogenic emissions continue unchecked, the warming increase may reach 8-10 degrees Celsius by 2300 (Rogelj et al., 2012). The contribution that large ice sheets will make to sea-level rise under such warming scenarios is difficult to quantify because the equilibrium-response timescale of ice sheets is longer than those of the atmosphere or ocean. Here we use a coupled ice-sheet/ice-shelf model to show that if atmospheric warming exceeds 1.5 to 2 degrees Celsius above present, collapse of the major Antarctic ice shelves triggers a centennial- to millennial-scale response of the Antarctic ice sheet in which enhanced viscous flow produces a long-term commitment (an unstoppable contribution) to sea-level rise. Our simulations represent the response of the present-day Antarctic ice-sheet system to the oceanic and climatic changes of four representative concentration pathways (RCPs) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Collins et al., 2013). We find that substantial Antarctic ice loss can be prevented only by limiting greenhouse gas emissions to RCP 2.6 levels. Higher-emissions scenarios lead to ice loss from Antarctic that will raise sea level by 0.6-3 metres by the year 2300. Our results imply that greenhouse gas emissions in the next few decades will strongly influence the long-term contribution of the Antarctic ice sheet to global sea level.

  19. Testing oils in antarctic soils

    International Nuclear Information System (INIS)

    Leufkens, D.

    2001-01-01

    The resident seals, whales and penguins in Antarctica's Ross Sea region have only environmentally friendly ways of getting around. In contrast, wherever humans go in the Antarctic and whatever they do, be it research, tourism or fishing, they need fuel for their planes, icebreaker ships, land vehicles and generators. Because of this, petroleum hydrocarbons are the most likely source of pollution in the Antarctic. Accidental oil spills often occur near scientific stations, where storage and refuelling of aircraft and vehicles can result in spills. Spills also occur as a consequence of drilling activities. Dr Jackie Aislabie, a microbiologist from the New Zealand government's research company Landcare Research, is leading a program aimed at understanding how oil spills impact on Antarctic soils. The properties of pristine soils were compared with oil-contaminated soil at three locations: Scott Base, Marble Point and in the Wright Valley at Bull Pass. Soils in the Scott Base area are impacted by the establishment and continuous habitation of the base over 40 years, and a hydrocarbon-contaminated site was sampled near a former storage area for drums of mixed oils. Soil sampled from Marble Point was taken from near the old Marble Point camp, which was inhabited from 1957 to about 1963. Oil stains were visible on the soil surface, and are assumed to have been there for more than 30 years. The samples selected for analysis from the Wright Valley came from a spill site near Bull Pass that occurred during seismic bore-hole drilling activities in 1985. The contamination levels ranged from below detection to just over 29,000 μg/g of soil. Descriptions and analyse results are included into a Geographic Information System and associated soils database

  20. [Microbiological analysis of terrestrial biotopes of the Antarctic region].

    Science.gov (United States)

    Tashirev, A B; Romanovskaia, V A; Rokitko, P V; Shilin, S O; Chernaia, N A; Tashireva, A A

    2010-01-01

    Microbiological analysis has been made of 120 samples from biotopes of the western coast of the Antarctic peninsula (Rasmussen cope, Tuxen cope, Waugh mountain), Argentine archipelago islands (Galindez, Skua, Corner, Barchans, Irizar, Uruguay, Cluls, Three Little Pigs, King-George), as well as neighbouring islands (Petermann--on the north, a group of Jalour islands--on the east, Berthelot--on the south-east); and more remote islands (Darboux, Lippmann, Booth). It was found out that the total number of chemoorganotrophic aerobic microorganisms was 10(6) - 10(8) cells/g of soil, that was by 2-3 orders lower than in the regions with temperate climate. One can observe a tendency of decreasing the quantity of chemoorganotrophic microorganisms in the Antartic biotopes (cells/g of a sample) in the following order: soil (1 x 10(7) - 8 x 10(8)), underground part of moss (1 x 10(6) - 5 x 10(7)), grass Deschampsia antarctica (10(6) - 10(8), slit of fresh-water reservoir (10(5) - 10(7)), ground part of moss (10(3) - 10(6)), lichens (10(3) - 10(6)). Representatives of several phylogenetic lines: Proteobacteria (genera Pseudomonas, Methylobacterium, Enterobacter), Firmicutes (genera Bacillus, Staphylococcus), Actinobacteria (genera Brevibacterium, Actinomyces, Streptomyces) have been found in the Antarctic samples. As a rule, genera of bacteria found in the Antarctic Region are widely distributed in different regions of the Earth with temperate climate. Microorganisms similar to the species Exophiala nigra (Issatsch.) Haats et de Hoog 1999, which was first detected 100 years ago by Academician B.L. Isachenko in the Arctic region water, were also isolated from biofilms on vertical rocks of the Galindez Island as well as from the soil of the Irizar Island.

  1. Reshaping the Antarctic Circumpolar Current via Antarctic Bottom Water Export

    Science.gov (United States)

    Stewart, A.; Hogg, A.

    2016-02-01

    Westerly wind forcing of Antarctic Circumpolar Current (ACC) is balanced at large-scale topographic obstructions by form drag; the formation of standing meanders produces a net westward pressure gradient associated with the geostrophically balanced meridional flow. These topographic obstructions also support the northward geostrophic flow of Antarctic Bottom Water (AABW), which piles up dense water on the eastern side of the topography and thereby acts to reduce the form drag. We therefore hypothesize that variations in the density of AABW and its export rate must be accommodated by reshaping the ACC's standing meanders in order to preserve the zonal force balance. We test this hypothesis using an idealized, eddy-resolving sector model of the ACC. We find that response of the ACC to switching off AABW production depends on whether the topography is high enough to block barotropic potential vorticity (PV) contours. If re-entrant PV contours exist then the ACC responds similarly to switching off AABW production or halving the westerly wind strength: for example the ACC transport drops by 10-20% and the surface speed in the meander decreases by around 25%. If PV contours are blocked then the ACC transport becomes insensitive to the westerlies, but switching off AABW production still leads to a reduced ACC transport through a wider, slower meander. These results suggest that the warming and freshening of AABW observed in recent decades may have a detectable impact on the surface circulation of the ACC.

  2. Digital Signature Management.

    Science.gov (United States)

    Hassler, Vesna; Biely, Helmut

    1999-01-01

    Describes the Digital Signature Project that was developed in Austria to establish an infrastructure for applying smart card-based digital signatures in banking and electronic-commerce applications. Discusses the need to conform to international standards, an international certification infrastructure, and security features for a public directory…

  3. ARM West Antarctic Radiation Experiment (AWARE) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Lubin, Daniel [Univ. of California, San Diego, CA (United States). Scripps Inst. of Oceanography; Bromwich, David H [Ohio State University; Vogelmann, Andrew M [Brookhaven National Lab. (BNL), Upton, NY (United States); Verlinde, Johannes [Pennsylvania State Univ., University Park, PA (United States); Russell, Lynn M [Univ. of California, San Diego, CA (United States). Scripps Inst. of Oceanography

    2017-09-15

    The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) is the most technologically advanced atmospheric and climate science campaign yet fielded in Antarctica. AWARE was motivated be recent concern about the impact of cryospheric mass loss on global sea level rise. Specifically, the West Antarctic Ice Sheet (WAIS) is now the second largest contributor to rising sea level, after the Greenland Ice Sheet. As steadily warming ocean water erodes the grounding lines of WAIS components where they meet the Amundsen and Bellingshausen Seas, the retreating grounding lines moving inland and downslope on the underlying terrain imply mechanical instability of the entire WAIS. There is evidence that this point of instability may have already been reached, perhaps signifying more rapid loss of WAIS ice mass. At the same time, the mechanical support provided by adjacent ice shelves, and also the fundamental stability of exposed ice cliffs at the ice sheet grounding lines, will be adversely impacted by a warming atmosphere that causes more frequent episodes of surface melting. The surface meltwater damages the ice shelves and ice cliffs through hydrofracturing. With the increasing concern regarding these rapid cryospheric changes, AWARE was motivated by the need to (a) diagnose the surface energy balance in West Antarctica as related to both summer season climatology and potential surface melting, and (b) improve global climate model (GCM) performance over Antarctica, such that future cryospheric projections can be more reliable.

  4. Mean Antarctic Circumpolar Current transport measured in Drake Passage

    Science.gov (United States)

    Donohue, K. A.; Tracey, K. L.; Watts, D. R.; Chidichimo, M. P.; Chereskin, T. K.

    2016-11-01

    The Antarctic Circumpolar Current is an important component of the global climate system connecting the major ocean basins as it flows eastward around Antarctica, yet due to the paucity of data, it remains unclear how much water is transported by the current. Between 2007 and 2011 flow through Drake Passage was continuously monitored with a line of moored instrumentation with unprecedented horizontal and temporal resolution. Annual mean near-bottom currents are remarkably stable from year to year. The mean depth-independent or barotropic transport, determined from the near-bottom current meter records, was 45.6 sverdrup (Sv) with an uncertainty of 8.9 Sv. Summing the mean barotropic transport with the mean baroclinic transport relative to zero at the seafloor of 127.7 Sv gives a total transport through Drake Passage of 173.3 Sv. This new measurement is 30% larger than the canonical value often used as the benchmark for global circulation and climate models.

  5. Two Antarctic penguin genomes reveal insights into their evolutionary history and molecular changes related to the Antarctic environment.

    Science.gov (United States)

    Li, Cai; Zhang, Yong; Li, Jianwen; Kong, Lesheng; Hu, Haofu; Pan, Hailin; Xu, Luohao; Deng, Yuan; Li, Qiye; Jin, Lijun; Yu, Hao; Chen, Yan; Liu, Binghang; Yang, Linfeng; Liu, Shiping; Zhang, Yan; Lang, Yongshan; Xia, Jinquan; He, Weiming; Shi, Qiong; Subramanian, Sankar; Millar, Craig D; Meader, Stephen; Rands, Chris M; Fujita, Matthew K; Greenwold, Matthew J; Castoe, Todd A; Pollock, David D; Gu, Wanjun; Nam, Kiwoong; Ellegren, Hans; Ho, Simon Yw; Burt, David W; Ponting, Chris P; Jarvis, Erich D; Gilbert, M Thomas P; Yang, Huanming; Wang, Jian; Lambert, David M; Wang, Jun; Zhang, Guojie

    2014-01-01

    Penguins are flightless aquatic birds widely distributed in the Southern Hemisphere. The distinctive morphological and physiological features of penguins allow them to live an aquatic life, and some of them have successfully adapted to the hostile environments in Antarctica. To study the phylogenetic and population history of penguins and the molecular basis of their adaptations to Antarctica, we sequenced the genomes of the two Antarctic dwelling penguin species, the Adélie penguin [Pygoscelis adeliae] and emperor penguin [Aptenodytes forsteri]. Phylogenetic dating suggests that early penguins arose ~60 million years ago, coinciding with a period of global warming. Analysis of effective population sizes reveals that the two penguin species experienced population expansions from ~1 million years ago to ~100 thousand years ago, but responded differently to the climatic cooling of the last glacial period. Comparative genomic analyses with other available avian genomes identified molecular changes in genes related to epidermal structure, phototransduction, lipid metabolism, and forelimb morphology. Our sequencing and initial analyses of the first two penguin genomes provide insights into the timing of penguin origin, fluctuations in effective population sizes of the two penguin species over the past 10 million years, and the potential associations between these biological patterns and global climate change. The molecular changes compared with other avian genomes reflect both shared and diverse adaptations of the two penguin species to the Antarctic environment.

  6. The Antarctic Ozone Hole: New Approaches for Detection of the Onset of Stratospheric Ozone Recovery

    Science.gov (United States)

    de Laat, J.; van Weele, M.; van der A, R. J.

    2016-12-01

    An important aspect of human influences on climate concerns the Antarctic ozone hole, the strong thinning of the thickness of the ozone layer during springtime over Antarctica, first observed in the early 1980s. Antarctic stratospheric ozone is expected to fully recover in the second half of the 21st century because of policy measures to eliminate emissions of ozone depleting substances. Identification of the onset of this recovery would mark an important scientific and political milestone, but has remained difficult so far owing to natural climate variability and methodological ambiguities. In this presentation, we will first give a brief introduction to methods that have been used in the past to try to identify the onset of recovery, and discuss their shortcomings and ambiguities. Secondly, we introduce and discuss a several observations-based new approaches for ozone recovery detection in the Antarctic Ozone Hole that we have developed, explain why we believe these methods are more robust than standard methods, and outline how they circumvent crucial pitfalls of the previously used methods. Finally, we present our analyses, showing that these new approaches applied to various sets of remote sensing observations provide the best evidence to date that that ozone destruction within the Antarctic Ozone Hole has significantly decreased since approximately the year 2000, and which can be attributed to concurrently decreasing ozone depleting substances.

  7. The changing form of Antarctic biodiversity.

    Science.gov (United States)

    Chown, Steven L; Clarke, Andrew; Fraser, Ceridwen I; Cary, S Craig; Moon, Katherine L; McGeoch, Melodie A

    2015-06-25

    Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change nonetheless pose challenges to the current and future understanding of Antarctic biodiversity. Life in the Antarctic and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewhere.

  8. UV Signature Mutations †

    Science.gov (United States)

    2014-01-01

    Sequencing complete tumor genomes and exomes has sparked the cancer field's interest in mutation signatures for identifying the tumor's carcinogen. This review and meta-analysis discusses signatures and their proper use. We first distinguish between a mutagen's canonical mutations – deviations from a random distribution of base changes to create a pattern typical of that mutagen – and the subset of signature mutations, which are unique to that mutagen and permit inference backward from mutations to mutagen. To verify UV signature mutations, we assembled literature datasets on cells exposed to UVC, UVB, UVA, or solar simulator light (SSL) and tested canonical UV mutation features as criteria for clustering datasets. A confirmed UV signature was: ≥60% of mutations are C→T at a dipyrimidine site, with ≥5% CC→TT. Other canonical features such as a bias for mutations on the non-transcribed strand or at the 3' pyrimidine had limited application. The most robust classifier combined these features with criteria for the rarity of non-UV canonical mutations. In addition, several signatures proposed for specific UV wavelengths were limited to specific genes or species; non-signature mutations induced by UV may cause melanoma BRAF mutations; and the mutagen for sunlight-related skin neoplasms may vary between continents. PMID:25354245

  9. Spatial and temporal variability across life's hierarchies in the terrestrial Antarctic.

    Science.gov (United States)

    Chown, Steven L; Convey, Peter

    2007-12-29

    Antarctica and its surrounding islands lie at one extreme of global variation in diversity. Typically, these regions are characterized as being species poor and having simple food webs. Here, we show that terrestrial systems in the region are nonetheless characterized by substantial spatial and temporal variations at virtually all of the levels of the genealogical and ecological hierarchies which have been thoroughly investigated. Spatial variation at the individual and population levels has been documented in a variety of genetic studies, and in mosses it appears that UV-B radiation might be responsible for within-clump mutagenesis. At the species level, modern molecular methods have revealed considerable endemism of the Antarctic biota, questioning ideas that small organisms are likely to be ubiquitous and the taxa to which they belong species poor. At the biogeographic level, much of the relatively small ice-free area of Antarctica remains unsurveyed making analyses difficult. Nonetheless, it is clear that a major biogeographic discontinuity separates the Antarctic Peninsula and continental Antarctica, here named the 'Gressitt Line'. Across the Southern Ocean islands, patterns are clearer, and energy availability is an important correlate of indigenous and exotic species richness, while human visitor numbers explain much of the variation in the latter too. Temporal variation at the individual level has much to do with phenotypic plasticity, and considerable life-history and physiological plasticity seems to be a characteristic of Antarctic terrestrial species. Environmental unpredictability is an important driver of this trait and has significantly influenced life histories across the region and probably throughout much of the temperate Southern Hemisphere. Rapid climate change-related alterations in the range and abundance of several Antarctic and sub-Antarctic populations have taken place over the past several decades. In many sub-Antarctic locations, these

  10. Mother Vocal Recognition in Antarctic Fur Seal Arctocephalus gazella Pups: A Two-Step Process.

    Directory of Open Access Journals (Sweden)

    Thierry Aubin

    Full Text Available In otariids, mother's recognition by pups is essential to their survival since females nurse exclusively their own young and can be very aggressive towards non-kin. Antarctic fur seal, Arctocephalus gazella, come ashore to breed and form dense colonies. During the 4-month lactation period, females alternate foraging trips at sea with suckling period ashore. On each return to the colony, females and pups first use vocalizations to find each other among several hundred conspecifics and olfaction is used as a final check. Such vocal identification has to be highly efficient. In this present study, we investigated the components of the individual vocal signature used by pups to identify their mothers by performing playback experiments on pups with synthetic signals. We thus tested the efficiency of this individual vocal signature by performing propagation tests and by testing pups at different playback distances. Pups use both amplitude and frequency modulations to identify their mother's voice, as well as the energy spectrum. Propagation tests showed that frequency modulations propagated reliably up to 64m, whereas amplitude modulations and spectral content greatly were highly degraded for distances over 8m. Playback on pups at different distances suggested that the individual identification is a two-step process: at long range, pups identified first the frequency modulation pattern of their mother's calls, and other components of the vocal signature at closer range. The individual vocal recognition system developed by Antarctic fur seals is well adapted to face the main constraint of finding kin in a crowd.

  11. Machine Fault Signature Analysis

    Directory of Open Access Journals (Sweden)

    Pratesh Jayaswal

    2008-01-01

    Full Text Available The objective of this paper is to present recent developments in the field of machine fault signature analysis with particular regard to vibration analysis. The different types of faults that can be identified from the vibration signature analysis are, for example, gear fault, rolling contact bearing fault, journal bearing fault, flexible coupling faults, and electrical machine fault. It is not the intention of the authors to attempt to provide a detailed coverage of all the faults while detailed consideration is given to the subject of the rolling element bearing fault signature analysis.

  12. Threshold Signature Schemes Application

    Directory of Open Access Journals (Sweden)

    Anastasiya Victorovna Beresneva

    2015-10-01

    Full Text Available This work is devoted to an investigation of threshold signature schemes. The systematization of the threshold signature schemes was done, cryptographic constructions based on interpolation Lagrange polynomial, elliptic curves and bilinear pairings were examined. Different methods of generation and verification of threshold signatures were explored, the availability of practical usage of threshold schemes in mobile agents, Internet banking and e-currency was shown. The topics of further investigation were given and it could reduce a level of counterfeit electronic documents signed by a group of users.

  13. Carbonate Deposition on Antarctic Shelves

    Science.gov (United States)

    Frank, T. D.; James, N. P.; Malcolm, I.

    2011-12-01

    Limestones associated with glaciomarine deposits occur throughout the geologic record but remain poorly understood. The best-described examples formed during major ice ages of the Neoproterozoic and Late Paleozoic. Quaternary analogs on Antarctic shelves have received comparatively little study. Here, we report on the composition, spatial distribution, and stratigraphic context of carbonate sediments contained in piston cores from the Ross Sea. The goals of this work are to (1) document the nature and distribution of carbonate sediments on the Ross Sea continental shelf and (2) examine temporal relationships to Quaternary glaciation. Results will be used to develop criteria that will improve understanding of analogous deposits in the ancient record. All carbonate-rich intervals in piston cores from the Ross Rea, now housed at the Antarctic Marine Geology Research Facility at Florida State University, were examined and described in detail. Sediment samples were disaggregated and sieved into size fractions before description with paleontological analysis carried out on the coarsest size fraction (>250 microns). Carbonate-rich sediments are concentrated in the northwestern Ross Sea, along the distal margins of Mawson and Pennell Banks. Calcareous facies include a spectrum of lithologies that range from fossiliferous mud, sand, and gravel to skeletal floatstone-rudstone and bafflestone. Floatstone-rudstone and bafflestone is most abundant along western-facing slopes in areas protected from the Antarctic Coastal Current. Sand-prone facies dominate the tops of banks and mud-prone, often spicultic, facies occur in deeper areas. The carbonate factory is characterized by a low-diversity, heterozoan assemblage that is dominated by stylasterine hydrocorals, barnacles, and bryozoans. Molluscs and echinoids are present but not abundant. Planktic and benthic foraminifera are ubiquitous components of the sediment matrix, which is locally very rich in sponge spicules. Biota rarely

  14. Environmental Working Group Arctic Meteorology and Climate Atlas, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Arctic Meteorology and Climate Atlas was developed by specialists from the Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia, the University...

  15. Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East Antarctic Adélie Penguin Populations.

    Science.gov (United States)

    Southwell, Colin; Emmerson, Louise; McKinlay, John; Newbery, Kym; Takahashi, Akinori; Kato, Akiko; Barbraud, Christophe; DeLord, Karine; Weimerskirch, Henri

    2015-01-01

    Seabirds are considered to be useful and practical indicators of the state of marine ecosystems because they integrate across changes in the lower trophic levels and the physical environment. Signals from this key group of species can indicate broad scale impacts or response to environmental change. Recent studies of penguin populations, the most commonly abundant Antarctic seabirds in the west Antarctic Peninsula and western Ross Sea, have demonstrated that physical changes in Antarctic marine environments have profound effects on biota at high trophic levels. Large populations of the circumpolar-breeding Adélie penguin occur in East Antarctica, but direct, standardized population data across much of this vast coastline have been more limited than in other Antarctic regions. We combine extensive new population survey data, new population estimation methods, and re-interpreted historical survey data to assess decadal-scale change in East Antarctic Adélie penguin breeding populations. We show that, in contrast to the west Antarctic Peninsula and western Ross Sea where breeding populations have decreased or shown variable trends over the last 30 years, East Antarctic regional populations have almost doubled in abundance since the 1980's and have been increasing since the earliest counts in the 1960's. The population changes are associated with five-year lagged changes in the physical environment, suggesting that the changing environment impacts primarily on the pre-breeding age classes. East Antarctic marine ecosystems have been subject to a number of changes over the last 50 years which may have influenced Adélie penguin population growth, including decadal-scale climate variation, an inferred mid-20th century sea-ice contraction, and early-to-mid 20th century exploitation of fish and whale populations.

  16. Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East Antarctic Adélie Penguin Populations.

    Directory of Open Access Journals (Sweden)

    Colin Southwell

    Full Text Available Seabirds are considered to be useful and practical indicators of the state of marine ecosystems because they integrate across changes in the lower trophic levels and the physical environment. Signals from this key group of species can indicate broad scale impacts or response to environmental change. Recent studies of penguin populations, the most commonly abundant Antarctic seabirds in the west Antarctic Peninsula and western Ross Sea, have demonstrated that physical changes in Antarctic marine environments have profound effects on biota at high trophic levels. Large populations of the circumpolar-breeding Adélie penguin occur in East Antarctica, but direct, standardized population data across much of this vast coastline have been more limited than in other Antarctic regions. We combine extensive new population survey data, new population estimation methods, and re-interpreted historical survey data to assess decadal-scale change in East Antarctic Adélie penguin breeding populations. We show that, in contrast to the west Antarctic Peninsula and western Ross Sea where breeding populations have decreased or shown variable trends over the last 30 years, East Antarctic regional populations have almost doubled in abundance since the 1980's and have been increasing since the earliest counts in the 1960's. The population changes are associated with five-year lagged changes in the physical environment, suggesting that the changing environment impacts primarily on the pre-breeding age classes. East Antarctic marine ecosystems have been subject to a number of changes over the last 50 years which may have influenced Adélie penguin population growth, including decadal-scale climate variation, an inferred mid-20th century sea-ice contraction, and early-to-mid 20th century exploitation of fish and whale populations.

  17. Antarctic Subglacial Lake Classification Inventory, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set is an Antarctic radar-based subglacial lake classification collection, which focuses on the radar reflection properties of each given lake.

  18. Abundance, viability and culturability of Antarctic bacteria

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.; DeSouza, M.J.B.D.; Nair, S.; Chandramohan, D.

    The viability of total number of bacteria decide the mineralisation rate in any ecosystem and ultimately the fertility of the region. This study aims at establishing the extent of viability in the standing stock of the Antarctic bacterial population...

  19. South African Antarctic earth science research programme

    CSIR Research Space (South Africa)

    SASCAR

    1984-02-01

    Full Text Available This document describes the past, current and planned future South African earth science research programme in the Antarctic, Southern Ocean and subantarctic regions. The scientific programme comprises five components into which present and future...

  20. Advanced Missile Signature Center

    Data.gov (United States)

    Federal Laboratory Consortium — The Advanced Missile Signature Center (AMSC) is a national facility supporting the Missile Defense Agency (MDA) and other DoD programs and customers with analysis,...

  1. Ross Ice Shelf, Antarctic Ice and Clouds

    Science.gov (United States)

    1991-01-01

    In this view of Antarctic ice and clouds, (56.5S, 152.0W), the Ross Ice Shelf of Antarctica is almost totally clear, showing stress cracks in the ice surface caused by wind and tidal drift. Clouds on the eastern edge of the picture are associated with an Antarctic cyclone. Winds stirred up these storms have been known to reach hurricane force.

  2. 78 FR 56247 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978 (Pub. L. 95-541)

    Science.gov (United States)

    2013-09-12

    ... climate change during the last 50- 1000 years. Location ASPA 113 Litchfield Island. Dates November 1, 2013... Conservation Act of 1978, Public Law 95-541. SUMMARY: The National Science Foundation (NSF) is required to... Conservation Act of 1978. NSF has published regulations under the Antarctic Conservation Act at Title 45 Part...

  3. Volcanic deposits in Antarctic snow and ice

    Science.gov (United States)

    Delmas, Robert J.; Legrand, Michel; Aristarain, Alberto J.; Zanolini, FrançOise

    1985-12-01

    Major volcanic eruptions are able to spread large amounts of sulfuric acid all over the world. Acid layers of volcanic origin were detected for the first time a few years ago by Hammer in Greenland ice. The present paper deals with volcanic deposits in the Antarctic. The different methods that can be used to find volcanic acid deposits in snow and ice cores are compared: electrical conductivity, sulfate, and acidity measurements. Numerous snow and ice samples collected at several Antarctic locations were analyzed. The results reveal that the two major volcanic events recorded by H2SO4, fallout in Antarctic ice over the last century are the eruptions of Krakatoa (1883) and Agung (1963), both located at equatorial latitudes in the southern hemisphere. The volcanic signals are found to be particularly well defined at central Antarctic locations apparently in relation to the low snow accumulation rates in these areas. It is demonstrated that volcanic sulfuric acid in snow is not even partially neutralized by ammonia. The possible influence of Antarctic volcanic activity on snow chemistry is also discussed, using the three recent eruptions of the Deception Island volcano as examples. Only one of them seems to have had a significant effect on the chemistry of snow at a location 200 km from this volcano. It is concluded that Antarctic volcanic ice records are less complicated than Greenland records because of the limited number of volcanos in the southern hemisphere and the apparently higher signal to background ratio for acidity in Antarctica than in Greenland.

  4. Ecology of antarctic marine sponges: an overview.

    Science.gov (United States)

    McClintock, James B; Amsler, Charles D; Baker, Bill J; van Soest, Rob W M

    2005-04-01

    Sponges are important components of marine benthic communities of Antarctica. Numbers of species are high, within the lower range for tropical latitudes, similar to those in the Arctic, and comparable or higher than those of temperate marine environments. Many have circumpolar distributions and in some habitats hexactinellids dominate benthic biomass. Antarctic sponge assemblages contribute considerable structural heterogeneity for colonizing epibionts. They also represent a significant source of nutrients to prospective predators, including a suite of spongivorous sea stars whose selective foraging behaviors have important ramifications upon community structure. The highly seasonal plankton blooms that typify the Antarctic continental shelf are paradoxical when considering the planktivorous diets of sponges. Throughout much of the year Antarctic sponges must either exploit alternate sources of nutrition such as dissolved organic carbon or be physiologically adapted to withstand resource constraints. In contrast to predictions that global patterns of predation should select for an inverse correlation between latitude and chemical defenses in marine sponges, such defenses are not uncommon in Antarctic sponges. Some species sequester their defensive metabolites in the outermost layers where they are optimally effective against sea star predation. Secondary metabolites have also been shown to short-circuit molting in sponge-feeding amphipods and prevent fouling by diatoms. Coloration in Antarctic sponges may be the result of relict pigments originally selected for aposematism or UV screens yet conserved because of their defensive properties. This hypothesis is supported by the bioactive properties of pigments examined to date in a suite of common Antarctic sponges.

  5. Antarctic volcanoes: A remote but significant hazard

    Science.gov (United States)

    Geyer, Adelina; Martí, Alex; Folch, Arnau; Giralt, Santiago

    2017-04-01

    Ash emitted during explosive volcanic eruptions can be dispersed over massive areas of the globe, posing a threat to both human health and infrastructures, such as the air traffic. Some of the last eruptions occurred during this decade (e.g. 14/04/2010 - Eyjafjallajökull, Iceland; 24/05/2011-Grímsvötn, Iceland; 05/06/2011-Puyehue-Cordón Caulle, Chile) have strongly affected the air traffic in different areas of the world, leading to economic losses of billions of euros. From the tens of volcanoes located in Antarctica, at least nine are known to be active and five of them have reported volcanic activity in historical times. However, until now, no attention has been paid to the possible social, economical and environmental consequences of an eruption that would occur on high southern latitudes, perhaps because it is considered that its impacts would be minor or local, and mainly restricted to the practically inhabited Antarctic continent. We show here, as a case study and using climate models, how volcanic ash emitted during a regular eruption of one of the most active volcanoes in Antarctica, Deception Island (South Shetland Islands), could reach the African continent as well as Australia and South America. The volcanic cloud could strongly affect the air traffic not only in the region and at high southern latitudes, but also the flights connecting Africa, South America and Oceania. Results obtained are crucial to understand the patterns of volcanic ash distribution at high southern latitudes with obvious implications for tephrostratigraphical and chronological studies that provide valuable isochrones with which to synchronize palaeoclimate records. This research was partially funded by the MINECO grants VOLCLIMA (CGL2015-72629-EXP)and POSVOLDEC(CTM2016-79617-P)(AEI/FEDER, UE), the Ramón y Cajal research program (RYC-2012-11024) and the NEMOH European project (REA grant 34 agreement n° 289976).

  6. Passive warming reduces stress and shifts reproductive effort in the Antarctic moss, Polytrichastrum alpinum.

    Science.gov (United States)

    Shortlidge, Erin E; Eppley, Sarah M; Kohler, Hans; Rosenstiel, Todd N; Zúñiga, Gustavo E; Casanova-Katny, Angélica

    2017-01-01

    The Western Antarctic Peninsula is one of the most rapidly warming regions on Earth, and many biotic communities inhabiting this dynamic region are responding to these well-documented climatic shifts. Yet some of the most prevalent organisms of terrestrial Antarctica, the mosses, and their responses to warming have been relatively overlooked and understudied. In this research, the impacts of 6 years of passive warming were investigated using open top chambers (OTCs), on moss communities of Fildes Peninsula, King George Island, Antarctica. The effects of experimental passive warming on the morphology, sexual reproductive effort and stress physiology of a common dioicous Antarctic moss, Polytrichastrum alpinum ,: were tested, gaining the first species-specific mechanistic insight into moss responses to warming in the Antarctic. Additionally community analyses were conducted examining the impact of warming on overall moss percentage cover and sporophyte production in intact Antarctic moss communities. Our results show a generally greater percentage moss cover under warming conditions as well as increased gametangia production in P. alpinum Distinct morphological and physiological shifts in P. alpinum were found under passive warming compared with those without warming: warmed mosses reduced investment in cellular stress defences, but invested more towards primary productivity and gametangia development. Taken together, results from this study of mosses under passive warming imply that in ice-free moss-dominated regions, continued climate warming will probably have profound impacts on moss biology and colonization along the Western Antarctic Peninsula. Such findings highlight the fundamental role that mosses will play in influencing the terrestrialization of a warming Antarctica. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Polar solar panels: Arctic and Antarctic microbiomes display similar taxonomic profiles.

    Science.gov (United States)

    Tanner, Kristie; Martí, Jose Manuel; Belliure, Josabel; Fernández-Méndez, Mar; Molina-Menor, Esther; Peretó, Juli; Porcar, Manuel

    2018-02-01

    Solar panels located on high (Arctic and Antarctic) latitudes combine the harshness of the climate with that of the solar exposure. We report here that these polar solar panels are inhabited by similar microbial communities in taxonomic terms, dominated by Hymenobacter spp., Sphingomonas spp. and Ascomycota. Our results suggest that solar panels, even on high latitudes, can shape a microbial ecosystem adapted to irradiation and desiccation. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  8. When shape matters: strategies of different Antarctic ascidians morphotypes to deal with sedimentation

    OpenAIRE

    Torre, Luciana; Abele, Doris; Lagger, Cristian; Momo, Fernando; Sahade, Ricardo

    2014-01-01

    Climate change leads to increased melting of tidewater glaciers in theWestern Antarctic Peninsula region and sediment bearing glacial melt waters negatively affects filter feeding species as solitary ascidians. In previous work the erect-forms Molgula pedunculata and Cnemidocarpa verrucosa (Order Stolidobranchiata) appeared more sensitive than the flat form Ascidia challengeri (Order Phlebobranchiata). Sedimentation exposure is expected to induce up-regulation of anaerobic metabol...

  9. The Influence of Platelet Ice and Snow on Antarctic Land-fast Sea Ice

    OpenAIRE

    Hoppmann, Mario; Nicolaus, Marcel

    2011-01-01

    Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climate- and ecosystems. Near Antarctic ice shelves, this land-fast sea ice exhibits two unique characteristics that distinguish it from most other sea ice: 1) Ice platelets form and grow in super-cooled water, which originates from ice shelf cavities. The crystals accumulate beneath the solid sea-ice cover and are incorporated into the sea-ice fabric, contributing between 10 and 60% to the mas...

  10. Synchronicity of Antarctic temperatures and local solar insolation on orbital timescales.

    Science.gov (United States)

    Laepple, Thomas; Werner, Martin; Lohmann, Gerrit

    2011-03-03

    The Milankovitch theory states that global climate variability on orbital timescales from tens to hundreds of thousands of years is dominated by the summer insolation at high northern latitudes. The supporting evidence includes reconstructed air temperatures in Antarctica that are nearly in phase with boreal summer insolation and out of phase with local summer insolation. Antarctic climate is therefore thought to be driven by northern summer insolation. A clear mechanism that links the two hemispheres on orbital timescales is, however, missing. We propose that key Antarctic temperature records derived from ice cores are biased towards austral winter because of a seasonal cycle in snow accumulation. Using present-day estimates of this bias in the 'recorder' system, here we show that the local insolation can explain the orbital component of the temperature record without having to invoke a link to the Northern Hemisphere. Therefore, the Antarctic ice-core-derived temperature record, one of the best-dated records of the late Pleistocene temperature evolution, cannot be used to support or contradict the Milankovitch hypothesis that global climate changes are driven by Northern Hemisphere summer insolation variations.

  11. The Last Interglacial History of the Antarctic Ice sheet

    Science.gov (United States)

    Bradley, Sarah; Siddall, Mark; Milne, Glenn A.; Masson-Delmotte, Valerie; Wolff, Eric; Hindmarsh, Richard C. A.

    2014-05-01

    In this paper we present a summary of the work which was conducted as part of the 'PAST4FUTURE -WP4.1: Sea Level and Ice sheets' project. The overall aim of this study was to understand the response of the Antarctic Ice sheet (AIS) to climate forcing during the Last interglacial (LIG) and its contribution to the observed higher than present sea level during this period. The study involved the application and development of a novel technique which combined East Antarctic stable isotope ice core data with the output from a Glacial Isostatic Adjustment (GIA) model [Bradley et al., 2012]. We investigated if the stable isotope ice core data are sensitive to detecting isostatically driven changes in the surface elevation driven by changes in the ice-loading history of the AIS and if so, could we address some key questions relating to the LIG history of the AIS. Although it is believed that the West Antarctic Ice sheet (WAIS) reduced in size during the LIG compared to the Holocene, major uncertainties and unknowns remain unresolved: Did the WAIS collapse? What would the contribution of such a collapse be the higher than present LIG eustatic sea level (ESL)? We will show that a simulated collapse of the WAIS does not generate a significant elevation driven signal at the EAIS LIG ice core sites, and as such, these ice core records cannot be used to assess WAIS stability over this period. However, we will present 'treasure maps' [Bradley et al., 2012] to identify regions of the AIS where results from geological studies and/or new paleoclimate data may be sensitive to detecting a WAIS collapse. These maps can act as a useful tool for the wider science community/field scientists as a guide to highlight sites suitable to constrain the evolution of the WAIS during the LIG. Studies have proposed that the surface temperature across the East Antarctic Ice Sheet (EAIS) was significantly warmer, 2-5°C during the LIG compared to present [Lang and Wolff, 2011]. These higher

  12. Health aspects of Antarctic tourism.

    Science.gov (United States)

    Prociv, P

    1998-12-01

    Increasing numbers of seaborne tourists are visiting Antarctica, with most coming from the United States (3503 in 1996-97), Germany (777), and Australia (680; cf. 356 in 1994-95 and 410 in 1995-96). The impression among travel medicine clinicians is that, each year, more prospective travelers seek advice about the health demands of this type of adventure, mostly relating to fitness for travel, exposure to extreme cold, hazards in ice and snow, and other potential health risks. This is a recent phenomenon. While a regular shipping service had been established between the Falklands and the subantarctic islands of South Georgia and the South Shetlands by 1924, the first documented tourists accompanied an Argentine expedition to the South Orkneys in 1933.1 Commercial airline flights over these islands and the Antarctic Peninsula began in 1956, from Chile, and recreational cruises to the Peninsula began in 1958. Tourist numbers subsequently grew slowly, for what was clearly an exclusive and very expensive undertaking, with few ships available for these hazardous voyages. From 1957 to 1993, 37,000 tourists visited by sea, most seeing only the Peninsula.2 The dramatic recent growth in numbers is a consequence of the collapse of the Soviet Union. The small fleet of ice-strengthened research vessels and working icebreakers, which was made redundant by withdrawal of central government support from isolated communities and military activities along the northern coast of Siberia (and from Antarctic research bases), now accounts for the bulk of charter-cruise tourism to Antarctica, at competitive prices. According to the International Association of Antarctica Tour Operators,3 7322 people traveled to Antarctica on commercially organized voyages in the 1996-97 season, and a record 10,000 shipborne visitors were expected for the 1997-98 season (November-March), traveling mainly from South America to the Peninsula on 15 ice-reinforced vessels, each carrying between 36 and 180

  13. Improved simulation of Antarctic sea ice due to the radiative effects of falling snow

    Science.gov (United States)

    Li, J.-L. F.; Richardson, Mark; Hong, Yulan; Lee, Wei-Liang; Wang, Yi-Hui; Yu, Jia-Yuh; Fetzer, Eric; Stephens, Graeme; Liu, Yinghui

    2017-08-01

    Southern Ocean sea-ice cover exerts critical control on local albedo and Antarctic precipitation, but simulated Antarctic sea-ice concentration commonly disagrees with observations. Here we show that the radiative effects of precipitating ice (falling snow) contribute substantially to this discrepancy. Many models exclude these radiative effects, so they underestimate both shortwave albedo and downward longwave radiation. Using two simulations with the climate model CESM1, we show that including falling-snow radiative effects improves the simulations relative to cloud properties from CloudSat-CALIPSO, radiation from CERES-EBAF and sea-ice concentration from passive microwave sensors. From 50-70°S, the simulated sea-ice-area bias is reduced by 2.12 × 106 km2 (55%) in winter and by 1.17 × 106 km2 (39%) in summer, mainly because increased wintertime longwave heating restricts sea-ice growth and so reduces summer albedo. Improved Antarctic sea-ice simulations will increase confidence in projected Antarctic sea level contributions and changes in global warming driven by long-term changes in Southern Ocean feedbacks.

  14. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, H.; Roberts, A. P.; Dekkers, M. J.; Liu, X.; Rohling, E. J.; Shi, Z.; An, Z.; Zhao, X.

    2016-12-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (˜8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  15. Soils of Sub-Antarctic tundras: diversity and basic chemical characteristics

    Science.gov (United States)

    Abakumov, Evgeny; Vlasov, Dmitry; Mukhametova, Nadezhda

    2014-05-01

    Antarctic peninsula is known as specific part of Antarctica, which is characterizes by humid and relatively warm climate of so-called sub Antarctic (maritime) zone. Annual precipitation and long above zero period provides the possibility of sustainable tundra's ecosystem formation. Therefore, the soil diversity of these tundra landscapes is maximal in the whole Antarctic. Moreover, the thickness of parent material debris's is also highest and achieves a 1 or 2 meters as highest. The presence of higher vascular plants Deshampsia antarctica which is considered as one of the main edificators provides the development of humus accumulation in upper solum. Penguins activity provides an intensive soil fertilization and development of plant communities with increased density. All these factors leads to formation of specific and quite diverse soil cover in sub Antarctic tundra's. These ecosystems are presented by following permafrost affected soils: Leptosols, Lithoosols, Crysols, Gleysols, Peats and Ornhitosols. Also the post Ornhitosols are widely spreaded in subantarcic ecosystems, they forms on the penguin rockeries during the plant succession development, leaching of nutrients and organic matter mineralization. "Amphibious" soils are specific for seasonal lakes, which evaporates in the end if Australian summer. These soils have specific features of bio sediments and soils as well. Soil chemical characteristic as well as organic matter features discussed in comparison with Antacrtic continental soil in presentation.

  16. Lipophilic pigments from the benthos of a perennially ice-covered Antarctic lake

    Science.gov (United States)

    Palmisano, A. C.; Wharton, R. A. Jr; Cronin, S. E.; Des Marais, D. J.; Wharton RA, J. r. (Principal Investigator)

    1989-01-01

    The benthos of a perennially ice-covered Antarctic lake, Lake Hoare, contained three distinct 'signatures' of lipophilic pigments. Cyanobacterial mats found in the moat at the periphery of the lake were dominated by the carotenoid myxoxanthophyll; carotenoids: chlorophyll a ratios in this high light environment ranged from 3 to 6.8. Chlorophyll c and fucoxanthin, pigments typical of golden-brown algae, were found at 10 to 20 m depths where the benthos is aerobic. Anaerobic benthic sediments at 20 to 30 m depths were characterized by a third pigment signature dominated by a carotenoid, tentatively identified as alloxanthin from planktonic cryptomonads, and by phaeophytin b from senescent green algae. Pigments were not found associated with alternating organic and sediment layers. As microzooplankton grazers are absent from this closed system and transformation rates are reduced at low temperatures, the benthos beneath the lake ice appears to contain a record of past phytoplankton blooms undergoing decay.

  17. Practical quantum digital signature

    Science.gov (United States)

    Yin, Hua-Lei; Fu, Yao; Chen, Zeng-Bing

    2016-03-01

    Guaranteeing nonrepudiation, unforgeability as well as transferability of a signature is one of the most vital safeguards in today's e-commerce era. Based on fundamental laws of quantum physics, quantum digital signature (QDS) aims to provide information-theoretic security for this cryptographic task. However, up to date, the previously proposed QDS protocols are impractical due to various challenging problems and most importantly, the requirement of authenticated (secure) quantum channels between participants. Here, we present the first quantum digital signature protocol that removes the assumption of authenticated quantum channels while remaining secure against the collective attacks. Besides, our QDS protocol can be practically implemented over more than 100 km under current mature technology as used in quantum key distribution.

  18. Antarctic station life: The first 15 years of mixed expeditions to the Antarctic

    Science.gov (United States)

    Sarris, Aspa

    2017-02-01

    This study examined the experiences of women who lived and worked on remote and isolated Antarctic stations for up to 15 months at a time. The study employed purposeful sampling and a longitudinal - processual approach to study women's experiences over the first 15 years of mixed gender Antarctic expeditions. The retrospective analysis was based on a semi-structured interview administered to 14 women upon their return to Australia. The results showed that women referred to the natural physical Antarctic environment as one of the best aspects of their experience and the reason they would recommend the Antarctic to their friends as a good place to work. In describing the worst aspect of their experience, women referred to aspects of Antarctic station life, including: (i) the male dominated nature of station culture; (ii) the impact of interpersonal conflict, including gender based conflict and friction between scientists and trades workers; and (iii) the lack of anonymity associated with living and working with the same group of individuals, mainly men, for up to 12 months or more. The results are discussed within the context of the evolution of Antarctic station culture and recommendations are made in terms of the demography of expeditions, expeditioner selection and recruitment and the ongoing monitoring of Antarctic station culture. The study presents a framework that can be applied to groups and teams living and working in analogous isolated, confined and extreme work environments, including outer space missions.

  19. Recommendations of the National Academies' Study: A Strategic Vision for NSF Investments in Antarctic and Southern Ocean Research

    Science.gov (United States)

    Weller, R. A.; Geller, L.; Schofield, O.

    2016-02-01

    A new study from the National Academy of Sciences, involving input from over 450 scientists around the country, has proposed a strategic vision and priorities for NSF's investments in Antarctic and Southern Ocean research for the coming decade. The Committee recommended that NSF continue to invest in a broad portfolio of research, balanced with a few larger-scale, more directed efforts, including the following priority initiatives: How fast and how far will sea level rise? The Changing Antarctic Ice Sheets Initiative How do Antarctic biota evolve and adapt to the changing environment? Decoding the genomic and transcriptomic bases of biological adaptation and response across Antarctic organisms and ecosystems How did our Universe begin and what are the underlying physical laws that govern its evolution and ultimate fate? A next generation cosmic microwave background program. Here we will focus on the proposed "Changing Ice Sheets Initiative", which includes following main elements: A multidisciplinary campaign to understand why the Antarctic ice sheets are changing now and how they will change in the future. Advancing understanding of the complex interactions among ice, ocean, atmosphere, and climate that drive Antarctic ice sheet changes will require a coordinated campaign of focused process studies, sustained observations, and mapping of unknown terrains in critical regions of the ocean, ice surface, and sub-ice environment, along with advancement of the coupled models. Using multiple records of past ice sheet change to understand rates and processes. Integrated studies of ice cores from the last interglacial period that can provide annual-scale resolution, together with marine sediment cores from key areas, may yield new insights on how fast ice sheets have collapsed in the past. We will discuss how this proposed initiative can build upon West Antarctic Ice Sheet research to date, and what types of infrastructure and logistical support are most critical for

  20. Dynamic Antarctic ice sheet during the early to mid-Miocene

    Science.gov (United States)

    Gasson, Edward; DeConto, Robert M.; Pollard, David; Levy, Richard H.

    2016-03-01

    Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate-ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet-climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52-0.66‰, or a sea level equivalent change of 30-36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability.

  1. Meteorological observatory for Antarctic data collection; L`Osservatorio per l`acquisizione dei dati meteorologici in Antartide

    Energy Technology Data Exchange (ETDEWEB)

    Grigioni, P.; De silvestri, L. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dip. Ambiente; Della Vedova, A.M. [Istituto Nazionale di Geofisica, P.N.R.A., Rome (Italy)

    1996-12-31

    In the last years, a great number of automatic weather stations was installed in Antarctica, with the aim to examine closely the weather and climate of this region and to improve the coverage of measuring points on the Antarctic surface. In 1987 the Italian Antarctic Project started to set up a meteorological network, in an area not completely covered by other countries. Some of the activities performed by the meteorological observatory, concerning technical functions such as maintenance of the AWS`s and the execution of radio soundings, or relating to scientific purposes such as validation and elaboration of collected data, are exposed. Finally, some climatological considerations on the thermal behaviour of the Antarctic troposphere such as `coreless winter`, and on the wind field, including katabatic flows in North Victoria Land are described.

  2. Statistical clumped isotope signatures

    NARCIS (Netherlands)

    Röckmann, T.; Popa, M.E.; Krol, M.C.; Hofmann, M.E.G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of

  3. Signatures of the Invisible

    CERN Multimedia

    Strom, D

    2003-01-01

    On the Net it is possible to take a look at art from afar via Virtual Museums. One such exhibition was recently in the New York Museum of Modern Art's branch, PS1. Entitled 'Signatures of the Invisible' it was a collaborative effort between artists and physicists (1/2 page).

  4. Massively parallel signature sequencing.

    Science.gov (United States)

    Zhou, Daixing; Rao, Mahendra S; Walker, Roger; Khrebtukova, Irina; Haudenschild, Christian D; Miura, Takumi; Decola, Shannon; Vermaas, Eric; Moon, Keith; Vasicek, Thomas J

    2006-01-01

    Massively parallel signature sequencing is an ultra-high throughput sequencing technology. It can simultaneously sequence millions of sequence tags, and, therefore, is ideal for whole genome analysis. When applied to expression profiling, it reveals almost every transcript in the sample and provides its accurate expression level. This chapter describes the technology and its application in establishing stem cell transcriptome databases.

  5. Ice age aerosol content from east Antarctic ice core samples and past wind strength

    International Nuclear Information System (INIS)

    Petit, J.R.; Briat, M.; Royer, A.

    1981-01-01

    The possible link between the aerosol content from the 905 deep Dome C ice core (East Antartica) which spans some 32,000 yr (Lorius et al. Nature; 280:644 (1979)) and climate, is considered. No evidence of major global or local volcanic activity was found though large marine and continental inputs (respectively 5 and 20 times higher than present) were observed at the end of the last Glacial stage. It is considered that they reflect glacial age climate with stronger atmospheric circulation, enhanced aridity and faster aerosol transport towards the Antarctic continent. (U.K.)

  6. Export of nutrient rich Northern Component Water preceded early Oligocene Antarctic glaciation

    Science.gov (United States)

    Coxall, Helen K.; Huck, Claire E.; Huber, Matthew; Lear, Caroline H.; Legarda-Lisarri, Alba; O'Regan, Matt; Sliwinska, Kasia K.; van de Flierdt, Tina; de Boer, Agatha M.; Zachos, James C.; Backman, Jan

    2018-03-01

    The onset of the North Atlantic Deep Water formation is thought to have coincided with Antarctic ice-sheet growth about 34 million years ago (Ma). However, this timing is debated, in part due to questions over the geochemical signature of the ancient Northern Component Water (NCW) formed in the deep North Atlantic. Here we present detailed geochemical records from North Atlantic sediment cores located close to sites of deep-water formation. We find that prior to 36 Ma, the northwestern Atlantic was stratified, with nutrient-rich, low-salinity bottom waters. This restricted basin transitioned into a conduit for NCW that began flowing southwards approximately one million years before the initial Antarctic glaciation. The probable trigger was tectonic adjustments in subarctic seas that enabled an increased exchange across the Greenland-Scotland Ridge. The increasing surface salinity and density strengthened the production of NCW. The late Eocene deep-water mass differed in its carbon isotopic signature from modern values as a result of the leakage of fossil carbon from the Arctic Ocean. Export of this nutrient-laden water provided a transient pulse of CO2 to the Earth system, which perhaps caused short-term warming, whereas the long-term effect of enhanced NCW formation was a greater northward heat transport that cooled Antarctica.

  7. Glacier extent in sub-Antarctic Kerguelen archipelago from MIS 3 period: Evidence from 36Cl dating

    Science.gov (United States)

    Jomelli, Vincent; Schimmelpfennig, Irene; Favier, Vincent; Mokadem, Fatima; Landais, Amaelle; Rinterknecht, Vincent; Brunstein, Daniel; Verfaillie, Deborah; Legentil, Claude; Aumaitre, Georges; Bourlès, Didier L.; Keddadouche, Karim

    2018-03-01

    Documenting sub-Antarctic glacier variations during the local last glacial maximum is of major interest to better understand their sensitivity to atmospheric and oceanic temperature changes in conjunction with Antarctic ice sheet changes. However, data are sparse because evidence of earlier glacier extents is for most sub-Antarctic islands located offshore making their observation complex. Here, we present 22 cosmogenic 36Cl surface exposure ages obtained from five sites at Kerguelen to document the glacial history. The 36Cl ages from roche moutonnee surfaces, erratics and boulders collected on moraines span from 41.9 ± 4.4 ka to 14.3 ± 1.1 ka. Ice began to retreat on the eastern part of the main island before 41.4 ± 4.4 ka. Slow deglaciation occurred from ∼41 to ∼29 ka. There is no evidence of advances between 29 ka and the Antarctic Cold Reversal (ACR) period (∼14.5-12.9 ka) period. During the ACR, however, the Bontemps and possibly Belvedere moraines were formed by the advance of a Cook Ice Cap outlet glacier and a local glacier on the Presque Ile Jeanne d'Arc, respectively. This glacier evolution differs partly from that of glaciers in New Zealand and in Patagonia. These asynchronous glacier changes in the sub-Antarctic region are however in agreement with sea surface temperature changes recorded around Antarctica, which suggest differences in the climate evolution of the Indo-Pacific and Atlantic sectors of Antarctica.

  8. The German Antarctic Receiving Station GARS O'Higgins: Remote sensing as core for a broader range of activities

    Science.gov (United States)

    Höppner, Kathrin; Diedrich, Erhard; Klügel, Thomas; Metzig, Robert

    2014-05-01

    Since 1991 the German Antarctic Station GARS O'Higgins is operated by the German Aerospace Center (DLR) in cooperation with the Federal Agency for Cartography and Geodesy (BKG). The station is located about 30 km west of the northern tip of the Antarctic Peninsula in the direct vicinity of the Chilean Antarctic Base General Bernardo O'Higgins. The most important scientific instrument of the station is the 9-m antenna system which is used for the reception of satellite data, telecommanding of satellites and also for geodetic radiotelescope measurements. The antenna has been designed for use in extreme Antarctic conditions. With this antenna system a wide range of Earth observation data of European and German satellite missions (ERS-1/-2, TerraSAR-X, TanDEM-X) are recorded since 1991. These data provide important insights into the climate and environmental changes at the Antarctic Peninsula since 20 years now. Since the beginning of 2010 the station is operational and manned year-around in a 7/24 schedule. Future plans envisage a development towards an observatory for environmentally relevant research. That means that the portfolio of the station will be expanded including the development of the infrastructure, in particular the construction and operation of new scientific instruments that will be focused on long-term measurements. The paper presents an introduction to the GARS O'Higgins station, the current state and future plans.

  9. Impact of biogenic very short-lived bromine on the Antarctic ozone hole during the 21st century

    Science.gov (United States)

    Fernandez, Rafael Pedro; Kinnison, Douglas E.; Lamarque, Jean-Francois; Tilmes, Simone; Saiz-Lopez, Alfonso

    2017-04-01

    Active bromine released from the photochemical decomposition of biogenic very short-lived bromocarbons (VSLBr) enhances stratospheric ozone depletion. Based on a dual set of 1960-2100 coupled chemistry-climate simulations (i.e. with and without VSLBr), we show that the maximum Antarctic ozone hole depletion increases by up to 14% when natural VSLBr are considered, in better agreement with ozone observations. The impact of the additional 5 pptv VSLBr on Antarctic ozone is most evident in the periphery of the ozone hole, producing an expansion of the ozone hole area of 5 million km2, which is equivalent in magnitude to the recently estimated Antarctic ozone healing due to the implementation of the Montreal Protocol. We find that the inclusion of VSLBr in CAM-Chem does not introduce a significant delay of the modelled ozone return date to 1980 October levels, but instead affect the depth and duration of the simulated ozone hole. Our analysis further shows that total bromine-catalysed ozone destruction in the lower stratosphere surpasses that of chlorine by year 2070, and indicates that natural VSLBr chemistry would dominate Antarctic ozone seasonality before the end of the 21st century. This work suggests a large influence of biogenic bromine on the future Antarctic ozone layer.

  10. Dense shelf water spreading from Antarctic coastal polynyas to the deep Southern Ocean: A regional circumpolar model study

    Science.gov (United States)

    Kusahara, Kazuya; Williams, Guy D.; Tamura, Takeshi; Massom, Robert; Hasumi, Hiroyasu

    2017-08-01

    The spreading of dense shelf water (DSW) from Antarctic coastal margins to lower latitudes plays a vital role in the ocean thermohaline circulation and the global climate system. Through enhanced localized sea ice production in Antarctic coastal polynyas, cold and saline DSW is formed over the continental shelf regions as a precursor to Antarctic Bottom Water (AABW). However, the detailed fate of coastal DSW over the Southern Ocean is still unclear. Here we conduct extensive passive tracer experiments using a circumpolar ocean-sea ice-ice shelf model to investigate pathways of the regional polynya-based DSW from the Antarctic margins to the deep Southern Ocean basins. In the numerical experiments, the Antarctic coastal margin is divided into nine regions, and a passive tracer is released from each region at the same rate as the local sea ice production. The modeled spatial distribution of the total concentration of the nine tracers is consistent with the observed AABW distribution and clearly demonstrates nine routes of the DSW over the Southern Ocean along its bottom topography. Furthermore, the model shows that while ˜50% of the total tracer is distributed northward from the continental shelf to the deep ocean, ˜7% is transported poleward beneath ice shelf cavities. The comprehensive tracer experiments allow us to estimate the contribution of local DSW to the total concentration along each of the pathways.

  11. [New data on trematodes of Antarctic fish].

    Science.gov (United States)

    Sokolov, S G; Gordeev, I I

    2015-01-01

    Deepwater fishes from the Amundsen Sea, d'Urville Sea, Ross Sea, Cooperation Sea, Weddell Sea, and open waters of the South-West part of the Pacific sector of the Antarctic were examined. Fourteen species of trematodes were found. Muraenolepitrema magnatestis Gaevskaya et Rodjuk, 1988 and Helicometrina sp. were found in the Antarctic for the first time. Muraenolepitrema magnatestis was redescribed and basing on this, diagnosis of the genus Muraenolepitrema was amended. Muraenolepitrema magnatestis possesses the uroproct and glandular cells that are loosely arranged around the external seminal vesicle (without a membranous sac).

  12. A new research project on the interaction of the solid Earth and the Antarctic Ice Sheet

    Science.gov (United States)

    Fukuda, Y.; Nishijima, J.; Kazama, T.; Nakamura, K.; Doi, K.; Suganuma, Y.; Okuno, J.; Araya, A.; Kaneda, H.; Aoyama, Y.

    2017-12-01

    A new research project of "Grant-in-Aid for Scientific Research on Innovative Areas" funded by JSPS (Japan Society for the Promotion of Science) has recently been launched. The title of the project is "Giant reservoirs of heat/water/material: Global environmental changes driven by Southern Ocean and Antarctic Ice Sheet", and as a five years project, is aiming to establish a new research area for Antarctic environmental system science. The project consists of 7 research topics, including Antarctic ice sheet and Southern ocean sciences, new observation methodology, modeling and other interdisciplinary topics, and we are involved in the topic A02-2, "Interaction of the solid Earth and the Antarctic Ice Sheet". The Antarctic ice sheet, which relates to the global climate changes through the sea level rise and ocean circulation, is an essential element of the Earth system for predicting the future environment changes. Thus many studies of the ice sheet changes have been conducted by means of geomorphological, geological, geodetic surveys, as well as satellite gravimetry and satellite altimetry. For these studies, one of the largest uncertainties is the effects of GIA. Therefore, GIA as a key to investigate the interaction between the solid Earth and the ice sheet changes, we plan to conduct geomorphological, geological and geodetic surveys in the inland mountain areas and the coastal areas including the surrounding areas of a Japanese station Syowa in East Antarctica, where the in-situ data for constraining GIA models are very few. Combining these new observations with other in-site data, various satellite data and numerical modeling, we aim to estimating a precise GIA model, constructing a reliable ice melting history after the last glacial maximum and obtaining the viscoelastic structure of the Earth's interior. In the presentation, we also show the five years research plans as well. This study was partially supported by JSPS KAKENHI Grant No. 17H06321.

  13. Assessment of Arctic and Antarctic sea ice predictability in CMIP5 decadal hindcasts

    Directory of Open Access Journals (Sweden)

    C.-Y. Yang

    2016-10-01

    Full Text Available This paper examines the ability of coupled global climate models to predict decadal variability of Arctic and Antarctic sea ice. We analyze decadal hindcasts/predictions of 11 Coupled Model Intercomparison Project Phase 5 (CMIP5 models. Decadal hindcasts exhibit a large multi-model spread in the simulated sea ice extent, with some models deviating significantly from the observations as the predicted ice extent quickly drifts away from the initial constraint. The anomaly correlation analysis between the decadal hindcast and observed sea ice suggests that in the Arctic, for most models, the areas showing significant predictive skill become broader associated with increasing lead times. This area expansion is largely because nearly all the models are capable of predicting the observed decreasing Arctic sea ice cover. Sea ice extent in the North Pacific has better predictive skill than that in the North Atlantic (particularly at a lead time of 3–7 years, but there is a re-emerging predictive skill in the North Atlantic at a lead time of 6–8 years. In contrast to the Arctic, Antarctic sea ice decadal hindcasts do not show broad predictive skill at any timescales, and there is no obvious improvement linking the areal extent of significant predictive skill to lead time increase. This might be because nearly all the models predict a retreating Antarctic sea ice cover, opposite to the observations. For the Arctic, the predictive skill of the multi-model ensemble mean outperforms most models and the persistence prediction at longer timescales, which is not the case for the Antarctic. Overall, for the Arctic, initialized decadal hindcasts show improved predictive skill compared to uninitialized simulations, although this improvement is not present in the Antarctic.

  14. A Roadmap for Antarctic and Southern Ocean Science for the Next Two Decades and Beyond

    Science.gov (United States)

    Kennicutt, M. C., II

    2015-12-01

    Abstract: Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to 'scan the horizon' to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.

  15. Microbial community composition of transiently wetted Antarctic Dry Valley soils.

    Science.gov (United States)

    Niederberger, Thomas D; Sohm, Jill A; Gunderson, Troy E; Parker, Alexander E; Tirindelli, Joëlle; Capone, Douglas G; Carpenter, Edward J; Cary, Stephen C

    2015-01-01

    During the summer months, wet (hyporheic) soils associated with ephemeral streams and lake edges in the Antarctic Dry Valleys (DVs) become hotspots of biological activity and are hypothesized to be an important source of carbon and nitrogen for arid DV soils. Recent research in the DV has focused on the geochemistry and microbial ecology of lakes and arid soils, with substantially less information being available on hyporheic soils. Here, we determined the unique properties of hyporheic microbial communities, resolved their relationship to environmental parameters and compared them to archetypal arid DV soils. Generally, pH increased and chlorophyll a concentrations decreased along transects from wet to arid soils (9.0 to ~7.0 for pH and ~0.8 to ~5 μg/cm(3) for chlorophyll a, respectively). Soil water content decreased to below ~3% in the arid soils. Community fingerprinting-based principle component analyses revealed that bacterial communities formed distinct clusters specific to arid and wet soils; however, eukaryotic communities that clustered together did not have similar soil moisture content nor did they group together based on sampling location. Collectively, rRNA pyrosequencing indicated a considerably higher abundance of Cyanobacteria in wet soils and a higher abundance of Acidobacterial, Actinobacterial, Deinococcus/Thermus, Bacteroidetes, Firmicutes, Gemmatimonadetes, Nitrospira, and Planctomycetes in arid soils. The two most significant differences at the genus level were Gillisia signatures present in arid soils and chloroplast signatures related to Streptophyta that were common in wet soils. Fungal dominance was observed in arid soils and Viridiplantae were more common in wet soils. This research represents an in-depth characterization of microbial communities inhabiting wet DV soils. Results indicate that the repeated wetting of hyporheic zones has a profound impact on the bacterial and eukaryotic communities inhabiting in these areas.

  16. EBSD in Antarctic and Greenland Ice

    Science.gov (United States)

    Weikusat, Ilka; Kuiper, Ernst-Jan; Pennock, Gill; Sepp, Kipfstuhl; Drury, Martyn

    2017-04-01

    Ice, particularly the extensive amounts found in the polar ice sheets, impacts directly on the global climate by changing the albedo and indirectly by supplying an enormous water reservoir that affects sea level change. The discharge of material into the oceans is partly controlled by the melt excess over snow accumulation, partly by the dynamic flow of ice. In addition to sliding over bedrock, an ice body deforms gravitationally under its own weight. In order to improve our description of this flow, ice microstructure studies are needed that elucidate the dominant deformation and recrystallization mechanisms involved. Deformation of hexagonal ice is highly anisotropic: ice is easily sheared in the basal plane and is about two orders of magnitude harder parallel to the c-axis. As dislocation creep is the dominant deformation mechanism in polar ice this strong anisotropy needs to be understood in terms of dislocation activity. The high anisotropy of the ice crystal is usually ascribed to a particular behaviour of dislocations in ice, namely the extension of dislocations into partials on the basal plane. Analysis of EBSD data can help our understanding of dislocation activity by characterizing subgrain boundary types thus providing a tool for comprehensive dislocation characterization in polar ice. Cryo-EBSD microstructure in combination with light microscopy measurements from ice core material from Antarctica (EPICA-DML deep ice core) and Greenland (NEEM deep ice core) are presented and interpreted regarding substructure identification and characterization. We examined one depth for each ice core (EDML: 656 m, NEEM: 719 m) to obtain the first comparison of slip system activity from the two ice sheets. The subgrain boundary to grain boundary threshold misorientation was taken to be 3-5° (Weikusat et al. 2011). EBSD analyses suggest that a large portion of edge dislocations with slip systems basal gliding on the basal plane were indeed involved in forming subgrain

  17. The changing form of Antarctic biodiversity

    OpenAIRE

    Chown, Steven L.; Clarke, Andrew; Fraser, Ceridwen I.; Cary, S. Craig; Moon, Katherine L.; McGeoch, Melodie A.

    2015-01-01

    Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change non...

  18. Evolution of the early Antarctic ice ages

    NARCIS (Netherlands)

    Liebrand, Diederik; de Bakker, Anouk T M|info:eu-repo/dai/nl/371573734; Beddow, Helen M; Wilson, Paul A; Bohaty, Steven M; Ruessink, Gerben|info:eu-repo/dai/nl/169093360; Pälike, Heiko; Batenburg, Sietske J; Hilgen, Frederik J|info:eu-repo/dai/nl/102639876; Hodell, David A; Huck, Claire E; Kroon, Dick; Raffi, Isabella; Saes, Mischa J M; van Dijk, Arnold E|info:eu-repo/dai/nl/341412082; Lourens, Lucas J|info:eu-repo/dai/nl/125023103

    2017-01-01

    Understanding the stability of the early Antarctic ice cap in the geological past is of societal interest because present-day atmospheric CO2 concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution

  19. 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...

  20. Antarctic Intermediate Water Formation in a High-Resolution OGCM

    Science.gov (United States)

    Fetter, Antonio; Schodlok, Michael; Zlotnicki, Victor

    2010-05-01

    The importance of the Antarctic Circumpolar Current (ACC), and the Southern Ocean, in the Climate System, has become apparent in the last decades. Water masses formed at these high latitudes are linked to the shallow and deep branches of the meridional overturning circulation. The Antarctic Intermediate Water (AAIW), as the main water mass ventilating the base of the worlds ocean thermocline, plays a central role not only in the climate system dynamics, but also in the global cycles of carbon dioxide and other bio-geochemical tracers. The mechanisms AAIW formation, as well as, the relationship among the rate of formation of the AAIW, the ACC frontal locations and mesoscale activity at the fronts are investigated in this study. Thus, in this research the output of the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project is used. It is a global high-resolution data synthesis in space and time, that is obtained through an orthogonal projection of the Massachusetts Institute of Technology general circulation model (MITgcm) onto available satellite and in-situ data. During winter, deep mixed layers (ML) of up to 600 m are formed as a result of deep convection. In turn, the deep ML are the nursery grounds for the Subantarctic Mode Water (SAMW), the lighter precursor of the AAIW. Diapycnal transformation of AAIW, due to internal mixing and air-sea interactions, is found to occur mainly in the South Pacific Ocean, which is known to be one of the most important regions for AAIW transformation. However, significant AAIW transformation is also observed in the South Indian Ocean. In ECCO2, AAIW is represented for by the water masses within the 27-27.8 kg m-3 neutral density range. While the heaviest AAIW (27.4-27.8 kg.m-3) is formed in the South Indian Ocean, reaching a peak production of about 40Sv during late July, the lighter version of the AAIW (27-27.4 kg.m-3) is mainly produced in the South Pacific Ocean. We found that eddy fluxes efficiently

  1. Antarctic Peninsula troposphere-stratosphere-ionosphere coupling (APTIC) and conjugate events investigation

    Science.gov (United States)

    Milinevsky, G.

    2005-04-01

    Researches of troposphere-stratosphere-ionosphere coupling are based on idea of the strong influence of the long- and short-term solar activity variations on the polar terrestrial climate and the asymmetry in the energy deposition from the magnetosphere into the polar ionospheres. The solar activity variations produce changeable impact on magnetosphere and polar ionosphere in both hemispheres. Results of this impact are (1) differences in the ozone concentrations in the Antarctic and Arctic stratosphere due to different forcing in spring; (2) different planetary wave activity; (3) different gravity wave flux intensity depended on strengths of the weather frontal cyclones activity. The study of upper atmosphere in both hemispheres is necessary to better understand various physical mechanisms responsible for the energy transfer from the Sun into atmosphere and ionosphere as well as reverse flux from troposphere to geospace. A simultaneous consideration of phenomena occurring over both polar regions is very important for understanding of these processes. The solution of the problem of energy exchange between neutral atmosphere and geospace plasma is need in study of industrial EM pollution from Earth surface to geospace. A corresponding work must promote modeling space weather on satellite heights and earthquake prediction using ionosphere parameters changes. A determinative significance of Antarctic Peninsula is caused by following features: (1) Antarctic Peninsula is situated near an extremely cyclonic active region - Drake Passage, (2) only this region in Antarctica is magnetically conjugated to industrial area in Northern hemisphere, and (3) this region contains many Antarctic stations which are good equipped by devices to study weather and climate, ozone layer, ionosphere and magnetic field. Last years weather observations at Vernadsky station show that up to 60 atmospheric frontal cyclones (with pressure variation more 20 millibars) swept over Antarctic

  2. Early signatures of regime shifts in complex dynamical systems

    Indian Academy of Sciences (India)

    2015-02-05

    Feb 5, 2015 ... A large number of studies have recently been carried out on the early signatures of regime shifts in a number of dynamical systems, e.g., ecosystems, the climate, fish and wildlife populations, ... Noise-induced regime shifts are also possible for which the vicinity of the bifurcation point is not essential. In this ...

  3. Early signatures of regime shifts in complex dynamical systems

    Indian Academy of Sciences (India)

    2015-02-05

    Feb 5, 2015 ... Abstract. A large number of studies have recently been carried out on the early signatures of regime shifts in a number of dynamical systems, e.g., ecosystems, the climate, fish and wildlife populations, financial markets, complex diseases and gene circuits. The underlying model in most cases is that of the ...

  4. Signatures of topological superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Yang

    2017-07-19

    The prediction and experimental discovery of topological insulators brought the importance of topology in condensed matter physics into the limelight. Topology hence acts as a new dimension along which more and more new states of matter start to emerge. One of these topological states of matter, namely topological superconductors, comes into the focus because of their gapless excitations. These gapless excitations, especially in one dimensional topological superconductors, are Majorana zero modes localized at the ends of the superconductor and exhibit exotic nonabelian statistics, which can be potentially applied to fault-tolerant quantum computation. Given their highly interesting physical properties and potential applications to quantum computation, both theorists and experimentalists spend great efforts to realize topological supercondoctors and to detect Majoranas. In two projects within this thesis, we investigate the properties of Majorana zero modes in realistic materials which are absent in simple theoretical models. We find that the superconducting proximity effect, an essential ingredient in all existing platforms for topological superconductors, plays a significant role in determining the localization property of the Majoranas. Strong proximity coupling between the normal system and the superconducting substrate can lead to strongly localized Majoranas, which can explain the observation in a recent experiment. Motivated by experiments in Molenkamp's group, we also look at realistic quantum spin Hall Josephson junctions, in which charge puddles acting as magnetic impurities are coupled to the helical edge states. We find that with this setup, the junction generically realizes an exotic 8π periodic Josephson effect, which is absent in a pristine Josephson junction. In another two projects, we propose more pronounced signatures of Majoranas that are accessible with current experimental techniques. The first one is a transport measurement, which uses

  5. Signature CERN-URSS

    CERN Document Server

    Jentschke,W

    1975-01-01

    Le DG W.Jentschke souhaite la bienvenue à l'assemblée et aux invités pour la signature du protocole entre le Cern et l'URSS qui est un événement important. C'est en 1955 que 55 visiteurs soviétiques ont visité le Cern pour la première fois. Le premier DG au Cern, F.Bloch, et Mons.Amaldi sont aussi présents. Tandis que le discours anglais de W.Jentschke est traduit en russe, le discours russe de Mons.Morozov est traduit en anglais.

  6. Emerging spatial patterns in Antarctic prokaryotes.

    Science.gov (United States)

    Chong, Chun-Wie; Pearce, David A; Convey, Peter

    2015-01-01

    Recent advances in knowledge of patterns of biogeography in terrestrial eukaryotic organisms have led to a fundamental paradigm shift in understanding of the controls and history of life on land in Antarctica, and its interactions over the long term with the glaciological and geological processes that have shaped the continent. However, while it has long been recognized that the terrestrial ecosystems of Antarctica are dominated by microbes and their processes, knowledge of microbial diversity and distributions has lagged far behind that of the macroscopic eukaryote organisms. Increasing human contact with and activity in the continent is leading to risks of biological contamination and change in a region whose isolation has protected it for millions of years at least; these risks may be particularly acute for microbial communities which have, as yet, received scant recognition and attention. Even a matter apparently as straightforward as Protected Area designation in Antarctica requires robust biodiversity data which, in most parts of the continent, remain almost completely unavailable. A range of important contributing factors mean that it is now timely to reconsider the state of knowledge of Antarctic terrestrial prokaryotes. Rapid advances in molecular biological approaches are increasingly demonstrating that bacterial diversity in Antarctica may be far greater than previously thought, and that there is overlap in the environmental controls affecting both Antarctic prokaryotic and eukaryotic communities. Bacterial dispersal mechanisms and colonization patterns remain largely unaddressed, although evidence for regional evolutionary differentiation is rapidly accruing and, with this, there is increasing appreciation of patterns in regional bacterial biogeography in this large part of the globe. In this review, we set out to describe the state of knowledge of Antarctic prokaryote diversity patterns, drawing analogy with those of eukaryote groups where appropriate

  7. The response of a simple Antarctic ice-flow model to temperature and sea-level fluctuations over the Cenozoic era

    NARCIS (Netherlands)

    van Tuyll, C.I.|info:eu-repo/dai/nl/304831875; van de Wal, R.S.W.|info:eu-repo/dai/nl/101899556; Oerlemans, J.|info:eu-repo/dai/nl/06833656X

    2007-01-01

    An ice-flow model is used to simulate the Antarctic ice-sheet volume and deep-sea temperature record during Cenozoic times. We used a vertically integrated axisymmetric ice-sheet model, including bedrock adjustment. In order to overcome strong numerical hysteresis effects during climate change, the

  8. [History of Polish botanical and mycological researches on sheets of land of Antarctic and Sub-Antarctic in the years 1977-2009].

    Science.gov (United States)

    Köhler, Piotr; Olech, Maria

    2011-01-01

    The work includes a description of the period from the moment of setting up Polish Polar Station on King George Island (1977) to the end of International Polar Year IV in 2009. Researches on flower plants focused, among others, on plants' morphology, morphological composition of the pollen and anatomical ultra-structure of the leaves. There were also carried out biochemical and other searches for the internal mutability. Within physiological studies one concentrated on the problem of reaction to temperature stress. Biological researches focused mainly on solving taxonomic and bio-geographic problems. Finally, were published several monographs and, among others, the first in history complete description of moss' flora of the whole of Antarctic (2008). Research works over algae included also such issues as floristics, bio-geography, taxonomy and ecology (for instance, the rookery's impact on distribution of algae, or the influence of inanimate factors on dynamics of condensing the Diatoma in different water and soil-bound tanks). Up till now, within mycological investigations has been identified a variety of lichen fungi that for the most part of Antarctic are a novelty. There were scientifically described new for science genera and species of Western Antarctic. Lichenological studies were made in the field of taxonomy, geography, lichenometry, biochemistry of lichens, lichenoindication, ecophysiology and from the point of analysis of base metals' content. There were also described new for science species. Since 1991, were published the results of searches for the base metals' content and vestigial chemical elements in lichens' thallus. Ecophysiological researches concerned both micro-climatic conditions' impact on primary production and lichens' adaptation to a very cold climate. One discovered a mechanism of two-phase hydratization/dehydratization of lichens' thallus. On the ground of palaeobotanical analyzes was reconstructed a development of flora in Western

  9. Electronic Signature (eSig)

    Data.gov (United States)

    Department of Veterans Affairs — Beginning with the Government Paperwork Elimination Act of 1998 (GPEA), the Federal government has encouraged the use of electronic / digital signatures to enable...

  10. Expressiveness considerations of XML signatures

    DEFF Research Database (Denmark)

    Jensen, Meiko; Meyer, Christopher

    2011-01-01

    XML Signatures are used to protect XML-based Web Service communication against a broad range of attacks related to man-in-the-middle scenarios. However, due to the complexity of the Web Services specification landscape, the task of applying XML Signatures in a robust and reliable manner becomes...... more and more challenging. In this paper, we investigate this issue, describing how an attacker can still interfere with Web Services communication even in the presence of XML Signatures. Additionally, we discuss the interrelation of XML Signatures and XML Encryption, focussing on their security...

  11. Electronic Warfare Signature Measurement Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Electronic Warfare Signature Measurement Facility contains specialized mobile spectral, radiometric, and imaging measurement systems to characterize ultraviolet,...

  12. Overview of the chemical ecology of benthic marine invertebrates along the western Antarctic peninsula.

    Science.gov (United States)

    McClintock, James B; Amsler, Charles D; Baker, Bill J

    2010-12-01

    WAP, community-level non-consumptive effects occur when amphipods chemically sense fish predators and respond by seeking refuge in chemically-defended macroalgae. Such interactions may be important in releasing amphipods from predation pressure and facilitating their unusually high abundances along the WAP. Moreover, recent studies on the sensory biology of the Antarctic keystone sea star Odontaster validus indicate that chemotactile-mediated interactions between conspecifics and other sympatric predatory sea stars may have significant ramifications in structuring community dynamics. Finally, from a global environmental perspective, understanding how chemical ecology structures marine benthic communities along the WAP must increasingly be viewed in the context of the dramatic impacts of rapid climatic change now occurring in this biogeographic region.

  13. A simulated Antarctic fast ice ecosystem

    Science.gov (United States)

    Arrigo, Kevin R.; Kremer, James N.; Sullivan, Cornelius W.

    1993-01-01

    A 2D numerical ecosystem model of Antarctic land fast ice is developed to elucidate the primary production with the Antarctic sea ice zone. The physical component employs atmospheric data to simulate congelation ice growth, initial brine entrapment, desalination, and nutrient flux. The biological component is based on the concept of a maximum temperature-dependent algal growth rate which is reduced by limitations imposed from insufficient light or nutrients, as well as suboptimal salinity. Preliminary simulations indicate that, during a bloom, microalgae are able to maintain their vertical position relative to the lower congelation ice margin and are not incorporated into the crystal matrix as the ice sheet thickens. It is inferred that land fast sea ice contains numerous microhabitats that are functionally distinct based upon the unique set of processes that control microalgal growth and accumulation within each.

  14. The effects of greenhouse gases on the Antarctic ozone hole in the past, present, and future

    Science.gov (United States)

    Newman, P. A.; Li, F.; Lait, L. R.; Oman, L.

    2017-12-01

    The Antarctic ozone hole is primarily caused by human-produced ozone depleting substances such as chlorine-containing chlorofluorocarbons (CFCs) and bromine-containing halons. The large ozone spring-time depletion relies on the very-cold conditions of the Antarctic lower stratosphere, and the general containment of air by the polar night jet over Antarctica. Here we show the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM) coupled ocean-atmosphere-chemistry model for exploring the impact of increasing greenhouse gases (GHGs). Model simulations covering the 1960-2010 period are shown for: 1) a control ensemble with observed levels of ODSs and GHGs, 2) an ensemble with fixed 1960 GHG concentrations, and 3) an ensemble with fixed 1960 ODS levels. We look at a similar set of simulations (control, 2005 fixed GHG levels, and 2005 fixed ODS levels) with a new version of GEOSCCM over the period 2005-2100. These future simulations show that the decrease of ODSs leads to similar ozone recovery for both the control run and the fixed GHG scenarios, in spite of GHG forced changes to stratospheric ozone levels. These simulations demonstrate that GHG levels will have major impacts on the stratosphere by 2100, but have only small impacts on the Antarctic ozone hole.

  15. A diagnostic study of Antarctic fog

    Science.gov (United States)

    Lazzara, Matthew A.

    2008-10-01

    The United States Antarctic Program (USAP) is the largest scientific research program in the Antarctic and requires a considerable aviation operation. Although fog is one of the top three forecast problems related to flights aborted due to weather, it is largely unstudied. The objective of this project is to gain an understanding of fog that affects McMurdo Station, Antarctica and its nearby airfields. This understanding is gained through analyses of surface based weather observations, satellite measurements and numerical weather prediction models. Multi-channel satellite observations indicate that most austral summer fog events are "advective" in nature. This is supported by weather observations from McMurdo Station and nearby airfields where fog occurs at moderate wind speeds, and primarily from the eastward direction. Analyses using both a back trajectory model and mesoscale numerical model are consistent with this finding. The primary source region for fog is found to be from the southeast over the Ross Ice Shelf (72% of the cases studied), while only a minority of cases (23%) reveals a secondary source of fog from the north along the Scott Coast with airflow influences from the East Antarctic Plateau. McMurdo experiences two fog seasons with a primary peak in January and a secondary peak in September. Fog events are often short lived---typically 1 to 3 hours, though some can last up to 30 hours. Fog occurrences over the last 30 years appear to be decreasing. Time series analysis between the observed fog variability and large-scale circulations (e.g., El Nino, Antarctic Oscillation) yielded no correlations, while there is only a limited relationship of fog occurrence to ice concentration in nearby Lewis Bay and McMurdo Sound. Fog is more likely to take place at the nearby airfields rather than at McMurdo Station, which is consistent with the advective nature of the fog.

  16. Spectroscopic characterization of Antarctic marine aerosol

    Science.gov (United States)

    Paglione, Marco; Zanca, Nicola; Rinaldi, Matteo; Dall'osto, Manuel; Simo, Rafel; Facchini, Maria Cristina; Decesari, Stefano

    2017-04-01

    Marine aerosol constitutes an important and not thoroughly investigated natural aerosol system. In particular, the poor knowledge of the physical-chemical properties of primary (sea-spray) and secondary particles, especially over biologically active seawaters, affects the current capability of modeling the effect of marine aerosol on climate (O'Dowd et al., 2004). In polar regions, surface seawater composition and its exchanges with the atmosphere is complicated also by the presence of sea-ice and of the variety of micro-organisms (viruses, prokaryotes and microalgae) living within it (Levasseur,2013). In the framework of the Spanish project PEGASO (Plankton-derived Emission of Gases and Aerosols in the Southern Ocean) submicron aerosol samples were collected during a 6 weeks long oceanographic cruise (2nd January 2015 - 11th February 2015) conducted in the regions of Antarctic Peninsula, South Orkney and South Georgia Islands, an area of the Southern Ocean characterized every summer by both large patches of productive waters (phytoplankton blooms) and sea-ice cover. The collected samples were analyzed by means of proton-Nuclear Magnetic Resonance (H-NMR) spectroscopy with aim of organic compounds characterization in terms of functional groups and specific molecular tracers identification (Decesari et al., 2011). H-NMR spectral features resulted quite variable among the different samples both in terms of relative abundance of main functional groups and in terms of presence of specific compounds. In all the samples were found biogenic markers, like low-molecular-weight alkyl-amines and methanesulphonate (MSA), of secondary origin (formed by the condensation of vapors onto particles). Resonance signals of other aliphatic compounds of possible primary origin, like lipids, aminoacids (e.g. alanine) and sugars (e.g. sucrose) are present in variable concentrations in the samples. A hierarchical cluster analysis applied on the NMR spectra allowed to identify similarities

  17. Antarctic isolation: immune and viral studies

    Science.gov (United States)

    Tingate, T. R.; Lugg, D. J.; Muller, H. K.; Stowe, R. P.; Pierson, D. L.

    1997-01-01

    Stressful environmental conditions are a major determinant of immune reactivity. This effect is pronounced in Australian National Antarctic Research Expedition populations exposed to prolonged periods of isolation in the Antarctic. Alterations of T cell function, including depression of cutaneous delayed-type hypersensitivity responses and a peak 48.9% reduction of T cell proliferation to the mitogen phytohaemagglutinin, were documented during a 9-month period of isolation. T cell dysfunction was mediated by changes within the peripheral blood mononuclear cell compartment, including a paradoxical atypical monocytosis associated with altered production of inflammatory cytokines. There was a striking reduction in the production by peripheral blood mononuclear cells of the predominant pro-inflammatory monokine TNF-alpha and changes were also detected in the production of IL-1, IL-2, IL-6, IL-1ra and IL-10. Prolonged Antarctic isolation is also associated with altered latent herpesvirus homeostasis, including increased herpesvirus shedding and expansion of the polyclonal latent Epstein-Barr virus-infected B cell population. These findings have important long-term health implications.

  18. EVA: Evryscopes for the Arctic and Antarctic

    Science.gov (United States)

    Richichi, A.; Law, N.; Tasuya, O.; Fors, O.; Dennihy, E.; Carlberg, R.; Tuthill, P.; Ashley, M.; Soonthornthum, B.

    2017-06-01

    We are planning to build Evryscopes for the Arctic and Antarctic (EVA), which will enable the first ultra-wide-field, high-cadence sky survey to be conducted from both Poles. The system is based on the successful Evryscope concept, already installed and operating since 2015 at Cerro Tololo in Chile with the following characteristics: robotic operation, 8,000 square degrees simultaneous sky coverage, 2-minute cadence, milli-mag level photometric accuracy, pipelined data processing for real-time analysis and full data storage for off-line analysis. The initial location proposed for EVA is the PEARL station on Ellesmere island; later also an antarctic location shall be selected. The science goals enabled by this unique combination of almost full-sky coverage and high temporal cadence are numerous, and include among others ground-breaking forays in the fields of exoplanets, stellar variability, asteroseismology, supernovae and other transient events. The EVA polar locations will enable uninterrupted observations lasting in principle over weeks and months. EVA will be fully robotic. We discuss the EVA science drivers and expected results, and present the logistics and the outline of the project which is expected to have first light in the winter of 2018. The cost envelope can be kept very competitive thanks to R&D already employed for the CTIO Evryscope, to our experience with both Arctic and Antarctic locations, and to the use of off-the-shelf components.

  19. Olfactory sex recognition investigated in Antarctic prions.

    Directory of Open Access Journals (Sweden)

    Francesco Bonadonna

    Full Text Available Chemical signals can yield information about an animal such as its identity, social status or sex. Such signals have rarely been considered in birds, but recent results have shown that chemical signals are actually used by different bird species to find food and to recognize their home and nest. This is particularly true in petrels whose olfactory anatomy is among the most developed in birds. Recently, we have demonstrated that Antarctic prions, Pachyptila desolata, are also able to recognize and follow the odour of their partner in a Y-maze.However, the experimental protocol left unclear whether this choice reflected an olfactory recognition of a particular individual (i.e. partner or a more general sex recognition mechanism. To test this second hypothesis, male and female birds' odours were presented simultaneously to 54 Antarctic prions in a Y-maze. Results showed random behaviour by the tested bird, independent of its sex or reproductive status. Present results do not support the possibility that Antarctic prions can distinguish the sex of a conspecific through its odour but indirectly support the hypothesis that they can distinguish individual odours.

  20. Balance of the West Antarctic Ice Sheet

    Science.gov (United States)

    2002-01-01

    For several decades, measurements of the West Antarctic Ice Sheet showed it to be retreating rapidly. But new data derived from satellite-borne radar sensors show the ice sheet to be growing. Changing Antarctic ice sheets remains an area of high scientific interest, particularly in light of recent global warming concerns. These new findings are significant because scientists estimate that sea level would rise 5-6 meters (16-20 feet) if the ice sheet collapsed into the sea. Do these new measurements signal the end of the ice sheet's 10,000-year retreat? Or, are these new satellite data simply much more accurate than the sparse ice core and surface measurements that produced the previous estimates? Another possibility is that the ice accumulation may simply indicate that the ice sheet naturally expands and retreats in regular cycles. Cryologists will grapple with these questions, and many others, as they examine the new data. The image above depicts the region of West Antarctica where scientists measured ice speed. The fast-moving central ice streams are shown in red. Slower tributaries feeding the ice streams are shown in blue. Green areas depict slow-moving, stable areas. Thick black lines depict the areas that collect snowfall to feed their respective ice streams. Reference: Ian Joughin and Slawek Tulaczyk Science Jan 18 2002: 476-480. Image courtesy RADARSAT Antarctic Mapping Project

  1. Secondary Fe and Al in Antarctic paleosols: Correlation to Mars with prospect for the presence of life

    Science.gov (United States)

    Mahaney, William C.; Dohm, James; Kapran, Barbara; Hancock, Ronald G. V.; Milner, Michael W.

    2009-09-01

    Middle-Miocene age paleosols in the Antarctic Dry Valleys were studied for their compositional variation and concentrations of secondary oxides/coatings in progression of release of secondary oxides of Fe and Al shows variable percentages of individual oxihydrites relative to chemical element totals, and thus, to consume total Fe and Al would require tens of millions of additional years. The slow progression of Fe d/Fe t, used as a measure of relative age in other warmer alpine and Arctic climates, is shown here to amount to arithmetic functions argue for extremely slow but sustainable release of oxides in a cold, polar desert climate, in which temperatures prohibit the formation of clay minerals. The secondary mineral species present likely amount to residue from past climates that were more conducive to clay mineral genesis and aerosolic input over time. The presence of microbial life in Antarctic paleosols, with minor amounts of Fe available for physiological processes to function, argues for the potential existence of microorganisms in ice-enriched paleosols of Mars, particularly given its watery and dynamic geologic past and relatively high concentration of total Fe in subaerial paleosols. The distribution of Fe over a large part of the northern plains of Mars as determined by the GRS instrument is invoked as a comparison with the Antarctic.

  2. Protistan communities in the Australian sector of the Sub-Antarctic Zone during SAZ-Sense

    Science.gov (United States)

    de Salas, Miguel F.; Eriksen, Ruth; Davidson, Andrew T.; Wright, Simon W.

    2011-11-01

    Protistan species composition and abundance in the Sub-Antarctic Zone (SAZ) and Polar Front Zone (PFZ) south of Tasmania were determined by microscopy and pigment analysis from samples collected during the Sub-Antarctic Zone—Sensitivity of the sub-Antarctic Zone to Environmental Change (SAZ-Sense) voyage, in January and February of 2007. A primary goal of this voyage was to determine the potential effects of climate change-induced natural iron fertilisation of the SAZ on the protistan community by exploring differences between communities in waters west of Tasmania, which are low in iron, and eastern waters, which are fertilised by continental iron input and mixing across the subtropical front. The SAZ is a sink for anthropogenic CO 2 in spring, but the magnitude of this may vary depending on seasonal changes in protistan abundance, composition and trophodynamics. Protistan species composition and abundance in the western Sub-Antarctic Zone at process station 1 (P1) showed a community in which low carbon biomass was dominated by a Thalassiosira sp., which was very weakly silicified under strong silica limitation. Protistan cell carbon was dominated by diatoms and nano-picoflagellates at process station 2 (P2) in the Polar Front Zone (PFZ), while dinoflagellates dominated in the iron-enriched waters of eastern SAZ at station 3 (P3). Iron enrichment enhanced production and favoured proliferation of small flagellates during summer in the silica-depleted eastern SAZ rather than large diatoms, though the effect this may have on the vertical export of particulate organic carbon (POC) is still unclear.

  3. Future Antarctic bed topography and its implications for ice sheet dynamics

    Science.gov (United States)

    Adhikari, S.; Ivins, E. R.; Larour, E.; Seroussi, H.; Morlighem, M.; Nowicki, S.

    2014-06-01

    The Antarctic bedrock is evolving as the solid Earth responds to the past and ongoing evolution of the ice sheet. A recently improved ice loading history suggests that the Antarctic Ice Sheet (AIS) has generally been losing its mass since the Last Glacial Maximum. In a sustained warming climate, the AIS is predicted to retreat at a greater pace, primarily via melting beneath the ice shelves. We employ the glacial isostatic adjustment (GIA) capability of the Ice Sheet System Model (ISSM) to combine these past and future ice loadings and provide the new solid Earth computations for the AIS. We find that past loading is relatively less important than future loading for the evolution of the future bed topography. Our computations predict that the West Antarctic Ice Sheet (WAIS) may uplift by a few meters and a few tens of meters at years AD 2100 and 2500, respectively, and that the East Antarctic Ice Sheet is likely to remain unchanged or subside minimally except around the Amery Ice Shelf. The Amundsen Sea Sector in particular is predicted to rise at the greatest rate; one hundred years of ice evolution in this region, for example, predicts that the coastline of Pine Island Bay will approach roughly 45 mm yr-1 in viscoelastic vertical motion. Of particular importance, we systematically demonstrate that the effect of a pervasive and large GIA uplift in the WAIS is generally associated with the flattening of reverse bed slope, reduction of local sea depth, and thus the extension of grounding line (GL) towards the continental shelf. Using the 3-D higher-order ice flow capability of ISSM, such a migration of GL is shown to inhibit the ice flow. This negative feedback between the ice sheet and the solid Earth may promote stability in marine portions of the ice sheet in the future.

  4. Future Antarctic Bed Topography and Its Implications for Ice Sheet Dynamics

    Science.gov (United States)

    Adhikari, Surendra; Ivins, Erik R.; Larour, Eric Y.; Seroussi, Helene L.; Morlighem, Mathieu; Nowicki, S.

    2014-01-01

    The Antarctic bedrock is evolving as the solid Earth responds to the past and ongoing evolution of the ice sheet. A recently improved ice loading history suggests that the Antarctic Ice Sheet (AIS) has generally been losing its mass since the Last Glacial Maximum. In a sustained warming climate, the AIS is predicted to retreat at a greater pace, primarily via melting beneath the ice shelves.We employ the glacial isostatic adjustment (GIA) capability of the Ice Sheet System Model (ISSM) to combine these past and future ice loadings and provide the new solid Earth computations for the AIS.We find that past loading is relatively less important than future loading for the evolution of the future bed topography. Our computations predict that the West Antarctic Ice Sheet (WAIS) may uplift by a few meters and a few tens of meters at years AD 2100 and 2500, respectively, and that the East Antarctic Ice Sheet is likely to remain unchanged or subside minimally except around the Amery Ice Shelf. The Amundsen Sea Sector in particular is predicted to rise at the greatest rate; one hundred years of ice evolution in this region, for example, predicts that the coastline of Pine Island Bay will approach roughly 45mmyr-1 in viscoelastic vertical motion. Of particular importance, we systematically demonstrate that the effect of a pervasive and large GIA uplift in the WAIS is generally associated with the flattening of reverse bed slope, reduction of local sea depth, and thus the extension of grounding line (GL) towards the continental shelf. Using the 3-D higher-order ice flow capability of ISSM, such a migration of GL is shown to inhibit the ice flow. This negative feedback between the ice sheet and the solid Earth may promote stability in marine portions of the ice sheet in the future.

  5. Halogen species record Antarctic sea ice extent over glacial–interglacial periods

    Directory of Open Access Journals (Sweden)

    A. Spolaor

    2013-07-01

    Full Text Available Sea ice is an integral part of the earth's climate system because it affects planetary albedo, sea-surface salinity, and the atmosphere–ocean exchange of reactive gases and aerosols. Bromine and iodine chemistry is active at polar sea ice margins with the occurrence of bromine explosions and the biological production of organoiodine from sea ice algae. Satellite measurements demonstrate that concentrations of bromine oxide (BrO and iodine oxide (IO decrease over sea ice toward the Antarctic interior. Here we present speciation measurements of bromine and iodine in the TALDICE (TALos Dome Ice CorE ice core (159°11' E, 72°49' S; 2315 m a.s.l. spanning the last 215 ky. The Talos Dome ice core is located 250 km inland and is sensitive to marine air masses intruding onto the Antarctic Plateau. Talos Dome bromide (Br− is positively correlated with temperature and negatively correlated with sodium (Na. Based on the Br−/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I− and iodate (IO3−, peaks during glacials with lower values during interglacial periods. Although IO3− is considered the most stable iodine species in the atmosphere it was only observed in the TALDICE record during glacial maxima. Sea ice dynamics are arguably the primary driver of halogen fluxes over glacial–interglacial timescales, by altering the distance between the sea ice edge and the Antarctic plateau and by altering the surface area of sea ice available to algal colonization. Based on our results we propose the use of both halogens for examining Antarctic variability of past sea ice extent.

  6. The Australasian Antarctic Expedition 2013-2014: Practicing 'Citizen-Science' in a Changing World

    Science.gov (United States)

    Fogwill, C. J.; Turney, C. S.

    2014-12-01

    Government funding is the cornerstone of modern science. But with declining investment in science across most of the Western World, a major challenge for society is where best to place what little resource we have. Which research questions should have the greatest priority? Nowhere are these issues more pressing than in the Antarctic, where bases have and continue to play host to 'big-science', multi-year programmes of research, locking up logistical support and costs. But in a warming world, the areas with the greatest effects of climate change aren't always near government research stations. With this in mind, in 2012 a plan was formed to visit Commonwealth Bay, a remote area off the East Antarctic Ice Sheet, where in 2010, an iceberg the size of Rhode Island, known as B09B, dramatically knocked a 60-mile long tongue of ice off the Mertz Glacier into the Southern Ocean, setting off a cascade of change. Inspired by the expeditions of the past, we advertised berths for sale to take citizen scientists south with us, harnessing their interest, experience and investment. People responded far and wide. We were oversubscribed, and the Australasian Antarctic Expedition 2013-2014 was born. With the Russian-owned MV Akademik Shokalskiy as the expedition vessel, we set out south from the New Zealand port of Bluff in late November 2013. During our journey south and on the ice we undertook a number of scientific firsts for the region actively engaging the volunteer scientists on board in projects ranging from oceanography, biology, ecology, geology and glaciaology. The expedition demostrated how private funding could support targeted programmes of research and communicate it to the wider world. Small-science research can capture the public's imagination and also reap real scientific outputs. Although it is a funding model developed in the Antarctic a hundred years ago, the beauty is it can applied anywhere in the world.

  7. A New Antarctic Field Course for Undergraduates at Michigan State University

    Science.gov (United States)

    Tweedie, C. E.; Hesse, J.; Hollister, R. D.; Roberts, P.; Wilson, J.; Wilson, M. I.; Webber, P. J.

    2003-12-01

    Field courses in remote and extreme environments immerse students in new and unfamiliar cultural and environmental settings where the impact from learning is high and the conventional wisdom, mindsets, and life skills of students are challenged. Through the Office of Study Abroad at Michigan State University (MSU), a new field course for undergraduates entitled `Studies in Antarctic System Science' embraces these principles. The three week, 6 credit course will be convened for the first time during the 2003-04 austral summer and will feature field based activities and classroom sessions beginning in Ushuaia, Tierra Del Fuego, Argentina. The defining experience of the program will be a cruise of the Antarctic Peninsula on a tourist ship partnered to the International Association of Antarctic Tour Operators (IAATO). This cruise will include landings on a daily basis at various sites of interest and international research stations en route. In 2003-04, the course will comprise 20 students and three faculty members from MSU. The non-major course curriculum has been compiled from materials based on original research by program faculty, relevant literature, information obtained directly from the international research community, and the Antarctic tourist industry. Subject areas will span multiple disciplines including palaeohistory and ecology, oceanography, climatology, geology and glaciology, marine, terrestrial and aerobiology, early exploration, policy and management, and the potential impacts from climate change and humans. It is intended that the course be repeated on an annual basis and that the curriculum be expanded to include greater coverage of ongoing research activities, especially NSF funded research. We welcome contact and feedback from educators and scientists interested in this endeavor, especially those who would like to broaden the impact of their own education interests or research by offering materials that could enhance the curriculum of the course

  8. An assessment of historical Antarctic precipitation and temperature trend using CMIP5 models and reanalysis datasets

    Science.gov (United States)

    Tang, Malcolm S. Y.; Chenoli, Sheeba Nettukandy; Samah, Azizan Abu; Hai, Ooi See

    2018-03-01

    The study of Antarctic precipitation has attracted a lot of attention recently. The reliability of climate models in simulating Antarctic precipitation, however, is still debatable. This work assess the precipitation and surface air temperature (SAT) of Antarctica (90 oS to 60 oS) using 49 Coupled Model Intercomparison Project phase 5 (CMIP5) global climate models and the European Centre for Medium-range Weather Forecasts "Interim" reanalysis (ERA-Interim); the National Centers for Environmental Prediction Climate Forecast System Reanalysis (CFSR); the Japan Meteorological Agency 55-year Reanalysis (JRA-55); and the Modern Era Retrospective-analysis for Research and Applications (MERRA) datasets for 1979-2005 (27 years). For precipitation, the time series show that the MERRA and JRA-55 have significantly increased from 1979 to 2005, while the ERA-Int and CFSR have insignificant changes. The reanalyses also have low correlation with one another (generally less than +0.69). 37 CMIP5 models show increasing trend, 18 of which are significant. The resulting CMIP5 MMM also has a significant increasing trend of 0.29 ± 0.06 mm year-1. For SAT, the reanalyses show insignificant changes and have high correlation with one another, while the CMIP5 MMM shows a significant increasing trend. Nonetheless, the variability of precipitation and SAT of MMM could affect the significance of its trend. One of the many reasons for the large differences of precipitation is the CMIP5 models' resolution.

  9. Recent aerogeophysical exploration under the East Antarctic Ice Sheet in Wilkes Land

    Science.gov (United States)

    Bozzo, E.; Ferraccioli, F.; Armadillo, E.; Jordan, T. A.; Corr, H.; Hill, D. J.

    2009-12-01

    An extensive aerogeophysical survey was flown in Wilkes Land (East Antarctica) during the 2005/06 Antarctic field-campaign as part of a joint Italian-UK exploration project, WISE (Wilkes WIlkes Basin/Transantarctic Mountains System Exploration)/ ISODYN (Icehouse Earth: Stability Or DYNamism?). The Italian Antarctic programme provided major logistic support at Mario Zucchelli Station, at two remote field camps, Talos Dome and Sitry, and at Mid-Point. 68 survey flights led to the collection of over 60,000 line-km of new aerogeophysical data over a frontier region that had not been explored since the 70’s. Airborne radar, aeromagnetic and airborne gravity data were simultaneously collected on a British Antarctic Survey Twin Otter with the overarching aim of providing new basal boundary conditions for the dynamics and stability of the East Antarctic Ice Sheet, and characterizing geological structures in the Wilkes Subglacial Basin (WSB) and adjacent Transantarctic Mountains (TAM). During the International Polar Year our efforts focused on data analysis and subsequent development of new interpretations. Here we review some of the results. Our new bedrock topography map derived from airborne radar reveals major subglacial basins with depths up to 2.1 km below sea-level within the WSB region. These sub-basins are in places up to 1.5 km deeper than imaged by BEDMAP, have different orientations, and are flanked by major bedrock plateaus that differ from alpine-type landscapes exposed over the adjacent TAM in northern Victoria Land. The new subglacial topography for the region is a critical boundary condition to develop next generation coupled ice sheet and climate models over East Antarctica. These models are targeting the contentious stability of this marine-based part of the East Antarctic Ice Sheet during warm periods in the geological past and may provide a tool for assessing its longer term future behaviour in a warmer climate. The airborne radar dataset

  10. Ocean Circulation and Dynamics on the West Antarctic Peninsula Continental Shelf

    Science.gov (United States)

    2007-09-01

    d the shladig the stand( ardl error. 169 60 06S 720o\\ 68 OW 64 0W 60 OW 56 OW Longitude [m/yr]I 1 2 3 4 5 Figure 5-13: Modeled p)recipjitation ininus...for Climate and Ocean Research , both at WHOI. The atmospheric modelling presented in Chapter 5 was performed at the British Antarctic Survey with...Components ...... .................... 50 3.3.2 Diurnal Components ...... ....................... 52 3.3.3 Comparison with the AntPen04.01 Tidal Model

  11. Multisensors signature prediction workbench

    Science.gov (United States)

    Latger, Jean; Cathala, Thierry

    2015-10-01

    Guidance of weapon systems relies on sensors to analyze targets signature. Defense weapon systems also need to detect then identify threats also using sensors. The sensors performance is very dependent on conditions e.g. time of day, atmospheric propagation, background ... Visible camera are very efficient for diurnal fine weather conditions, long wave infrared sensors for night vision, radar systems very efficient for seeing through atmosphere and/or foliage ... Besides, multi sensors systems, combining several collocated sensors with associated algorithms of fusion, provide better efficiency (typically for Enhanced Vision Systems). But these sophisticated systems are all the more difficult to conceive, assess and qualify. In that frame, multi sensors simulation is highly required. This paper focuses on multi sensors simulation tools. A first part makes a state of the Art of such simulation workbenches with a special focus on SE-Workbench. SEWorkbench is described with regards to infrared/EO sensors, millimeter waves sensors, active EO sensors and GNSS sensors. Then a general overview of simulation of targets and backgrounds signature objectives is presented, depending on the type of simulation required (parametric studies, open loop simulation, closed loop simulation, hybridization of SW simulation and HW ...). After the objective review, the paper presents some basic requirements for simulation implementation such as the deterministic behavior of simulation, mandatory to repeat it many times for parametric studies... Several technical topics are then discussed, such as the rendering technique (ray tracing vs. rasterization), the implementation (CPU vs. GP GPU) and the tradeoff between physical accuracy and performance of computation. Examples of results using SE-Workbench are showed and commented.

  12. Decadal-interdecadal climate variability over Antarctica and linkages to the Tropics : analysis of ice core, instrumental, and tropical proxy data

    OpenAIRE

    Okumura, Yuko; Schneider, David; Deser, Clara; Wilson, Rob

    2012-01-01

    The Antarctic continent contains the majority of the global ice volume and plays an important role in a changing climate. The nature and causes of Antarctic climate variability are, however, poorly understood beyond interannual time scales due to the paucity of long, reliable meteorological observations. This study analyzes decadal-interdecadal climate variability over Antarctica using a network of annually resolved ice core records and various instrumental and tropical proxy data for the 19t...

  13. The Middle Miocene Climate Transition in the Central Mediterranean. Geologica Ultraiectina (326)

    NARCIS (Netherlands)

    Mourik, A.A.

    2010-01-01

    The Middle Miocene Climate Transition (~15-13.7 Ma) is one of the major steps in Cenozoic climate evolution. The rapid expansion of the East Antarctic Ice Sheet at ~13.9 – 13.7 Ma caused important climate changes on a global scale. The aim of this PhD research has been to study the effects of the

  14. The Antarctic krill Euphausia superba shows diurnal cycles of transcription under natural conditions.

    Directory of Open Access Journals (Sweden)

    Cristiano De Pittà

    Full Text Available BACKGROUND: Polar environments are characterized by extreme seasonal changes in day length, light intensity and spectrum, the extent of sea ice during the winter, and food availability. A key species of the Southern Ocean ecosystem, the Antarctic krill (Euphausia superba has evolved rhythmic physiological and behavioral mechanisms to adapt to daily and seasonal changes. The molecular organization of the clockwork underlying these biological rhythms is, nevertheless, still only partially understood. METHODOLOGY/PRINCIPAL FINDINGS: The genome sequence of the Antarctic krill is not yet available. A normalized cDNA library was produced and pyrosequenced in the attempt to identify large numbers of transcripts. All available E. superba sequences were then assembled to create the most complete existing oligonucleotide microarray platform with a total of 32,217 probes. Gene expression signatures of specimens collected in the Ross Sea at five different time points over a 24-hour cycle were defined, and 1,308 genes differentially expressed were identified. Of the corresponding transcripts, 609 showed a significant sinusoidal expression pattern; about 40% of these exibithed a 24-hour periodicity while the other 60% was characterized by a shorter (about 12-hour rhythm. We assigned the differentially expressed genes to functional categories and noticed that those concerning translation, proteolysis, energy and metabolic process, redox regulation, visual transduction and stress response, which are most likely related to daily environmental changes, were significantly enriched. Two transcripts of peroxiredoxin, thought to represent the ancestral timekeeping system that evolved about 2.5 billion years ago, were also identified as were two isoforms of the EsRh1 opsin and two novel arrestin1 sequences involved in the visual transduction cascade. CONCLUSIONS: Our work represents the first characterization of the krill diurnal transcriptome under natural conditions

  15. Signatures de l'invisible

    CERN Multimedia

    CERN Press Office. Geneva

    2000-01-01

    "Signatures of the Invisible" is an unique collaboration between contemporary artists and contemporary physicists which has the potential to help redefine the relationship between science and art. "Signatures of the Invisible" is jointly organised by the London Institute - the world's largest college of art and design and CERN*, the world's leading particle physics laboratory. 12 leading visual artists:

  16. Detection of Tephra Layers in Antarctic Sediment Cores with Hyperspectral Imaging

    Science.gov (United States)

    Aymerich, Ismael F.; Oliva, Marc; Giralt, Santiago; Martín-Herrero, Julio

    2016-01-01

    Tephrochronology uses recognizable volcanic ash layers (from airborne pyroclastic deposits, or tephras) in geological strata to set unique time references for paleoenvironmental events across wide geographic areas. This involves the detection of tephra layers which sometimes are not evident to the naked eye, including the so-called cryptotephras. Tests that are expensive, time-consuming, and/or destructive are often required. Destructive testing for tephra layers of cores from difficult regions, such as Antarctica, which are useful sources of other kinds of information beyond tephras, is always undesirable. Here we propose hyperspectral imaging of cores, Self-Organizing Map (SOM) clustering of the preprocessed spectral signatures, and spatial analysis of the classified images as a convenient, fast, non-destructive method for tephra detection. We test the method in five sediment cores from three Antarctic lakes, and show its potential for detection of tephras and cryptotephras. PMID:26815202

  17. Reaching for the Horizon: Enabling 21st Century Antarctic Science

    Science.gov (United States)

    Rogan-Finnemore, M.; Kennicutt, M. C., II; Kim, Y.

    2015-12-01

    The Council of Managers of National Antarctic Programs' (COMNAP) Antarctic Roadmap Challenges(ARC) project translated the 80 highest priority Antarctic and Southern Ocean scientific questionsidentified by the community via the SCAR Antarctic Science Horizon Scan into the highest prioritytechnological, access, infrastructure and logistics needs to enable the necessary research to answer thequestions. A workshop assembled expert and experienced Antarctic scientists and National AntarcticProgram operators from around the globe to discern the highest priority technological needs includingthe current status of development and availability, where the technologies will be utilized in the Antarctic area, at what temporal scales and frequencies the technologies will be employed,and how broadly applicable the technologies are for answering the highest priority scientific questions.Secondly the logistics, access, and infrastructure requirements were defined that are necessary todeliver the science in terms of feasibility including cost and benefit as determined by expected scientific return on investment. Finally, based on consideration of the science objectives and the mix oftechnologies implications for configuring National Antarctic Program logistics capabilities andinfrastructure architecture over the next 20 years were determined. In particular those elements thatwere either of a complexity, requiring long term investments to achieve and/or having an associated cost that realistically can only (or best) be achieved by international coordination, planning and partnerships were identified. Major trends (changes) in logistics, access, and infrastructure requirements were identified that allow for long-term strategic alignment of international capabilities, resources and capacity. The outcomes of this project will be reported.

  18. Antarctic bacteria inhibit growth of foodborne microorganisms at low temperatures.

    NARCIS (Netherlands)

    O'Brien, A.C.; Sharp, R.; Russell, N.J.; Roller, S.

    2004-01-01

    The aim of this study was to identify Antarctic microorganisms with the ability to produce cold-active antimicrobial compounds with potential for use in chilled food preservation. Colonies (4496) were isolated from 12 Antarctic soil samples and tested against Listeria innocua, Pseudomonas fragi and

  19. Biological studies in the Antarctic waters: A review

    Digital Repository Service at National Institute of Oceanography (India)

    Dhargalkar, V.K.

    stream_size 12 stream_content_type text/plain stream_name Proc_Workshop_Antarct_Stud_1990_407.pdf.txt stream_source_info Proc_Workshop_Antarct_Stud_1990_407.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset...

  20. Marine and terrestrial factors affecting Adélie penguin Pygoscelis adeliae chick growth and recruitment off the western Antarctic Peninsula

    Science.gov (United States)

    Chapman, Erik W.; Hofmann, Eileen E.; Patterson, Donna L.; Ribic, Christine A.; Fraser, William R.

    2011-01-01

    An individual-based bioenergetics model that simulates the growth of an Adélie penguin Pygoscelis adeliaechick from hatching to fledging was used to assess marine and terrestrial factors that affect chick growth and fledging mass off the western Antarctic Peninsula. Simulations considered the effects on Adélie penguin fledging mass of (1) modification of chick diet through the addition of Antarctic silverfish Pleuragramma antarcticum to an all-Antarctic krillEuphausia superba diet, (2) reduction of provisioning rate which may occur as a result of an environmental stress such as reduced prey availability, and (3) increased thermoregulatory costs due to wetting of chicks which may result from increased precipitation or snow-melt in colonies. Addition of 17% Antarctic silverfish of Age-Class 3 yr (AC3) to a penguin chick diet composed of Antarctic krill increased chick fledging mass by 5%. Environmental stress that results in >4% reduction in provisioning rate or wetting of just 10% of the chick’s surface area decreased fledging mass enough to reduce the chick’s probability of successful recruitment. The negative effects of reduced provisioning and wetting on chick growth can be compensated for by inclusion of Antarctic silverfish of AC3 and older in the chick diet. Results provide insight into climate-driven processes that influence chick growth and highlight a need for field research designed to investigate factors that determine the availability of AC3 and older Antarctic silverfish to foraging Adélie penguins and the influence of snowfall on chick wetting, thermoregulation and adult provisioning rate.

  1. Microfossils in the Antarctic cold desert: Possible implications for Mars

    Science.gov (United States)

    Friedmann, E. I.; Ocampo-Friedmann, R.

    1986-01-01

    In the Ross Desert of Antarctica, the principal life form is the cryptoendolithic microbial community in the near-surface layers of porous sandstone rocks. Biological, geological, and climatic factors interact in a complex and precarious balance, making life possible in an otherwise hostile environment. Once this balance is tipped, fossilization sets in. In the reverse case, new colonization of the rock surface may be initiated. As a result, fossilization is contemporary with modern life and both may be simultaneously present in a mosaic pattern. Also, different stages of fossilization are present. The process of fossilization takes place in a nonaquatic environment. If primitive life ever appeared on Mars, it is possible that with increasing aridity, life withdrew into an endolithic niche similar to that in the Antarctic desert. Fossilization in a nonaquatic environment may have set in with the result that traces of past life could be preserved. If such was the case, the study of the fossilization process in Antarctica may hold useful information for the analysis of Martian samples for microfossils.

  2. Greenhouse gas emissions from the Brazilian Antarctic Station "Comandante Ferraz".

    Science.gov (United States)

    Leripio, Alexandre de Avila; Torres, João Paulo Machado; Viana, Mariana de Sá; Echelmeier, Gustavo Rohden

    2012-12-01

    Climate change is a natural phenomenon that has been intensified due to increased emissions of greenhouse gases (GHG). It has become an indispensable issue in international negotiations related to global sustainability and is deeply related to the overall status of environmental health in our planet. We compiled an inventory of GHG emissions that resulted from human activities at the Brazilian Antarctic Scientific Station "Comandante Ferraz" (EACF) and collected emissions data relating to these activities from January to March 2011. The present work aims to identify the sources of GHG emissions, their characteristics, and composition, using as methodology and framework basis the international ISO 14,064:07 and the GHG Protocol. We addressed emissions of CO(2), CH(4), and N(2)O arising from the use of vehicles, diesel-electric generators, boilers, and wastewater treatment for the sewage treatment plant. We identified that the main GHG emissions derived from the activities of power generation using diesel and boilers (more than 80% of the emissions), adding more than 772 t of CO(2) equivalents. We identified that the diesel generators and boilers are the most important sources of emission by Expedition XXIX (2010-2011). In that CO(2) is principally emitted in relation to electrical energy generation from diesel generators, we emphasize the need for fuel burning reduction through energy consumption reduction. Copyright © 2012 Wiley Periodicals, Inc.

  3. Statistical clumped isotope signatures

    Science.gov (United States)

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  4. Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years

    Science.gov (United States)

    Gardner, Alex S.; Moholdt, Geir; Scambos, Ted; Fahnstock, Mark; Ligtenberg, Stefan; van den Broeke, Michiel; Nilsson, Johan

    2018-02-01

    Ice discharge from large ice sheets plays a direct role in determining rates of sea-level rise. We map present-day Antarctic-wide surface velocities using Landsat 7 and 8 imagery spanning 2013-2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since ˜ 2008. The new mapping provides complete coastal and inland coverage of ice velocity north of 82.4° S with a mean error of the daylight period. Using an optimized flux gate, ice discharge from Antarctica is 1929 ± 40 Gigatons per year (Gt yr-1) in 2015, an increase of 36 ± 15 Gt yr-1 from the time of the radar mapping. Flow accelerations across the grounding lines of West Antarctica's Amundsen Sea Embayment, Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula, account for 88 % of this increase. In contrast, glaciers draining the East Antarctic Ice Sheet have been remarkably constant over the period of observation. Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 183 ± 94 Gt yr-1 between 2008 and 2015. The modest increase in ice discharge over the past 7 years is contrasted by high rates of ice sheet mass loss and distinct spatial patters of elevation lowering. The West Antarctic Ice Sheet is experiencing high rates of mass loss and displays distinct patterns of elevation lowering that point to a dynamic imbalance. We find modest increase in ice discharge over the past 7 years, which suggests that the recent pattern of mass loss in Antarctica is part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent-wide radar mapping of ice flow.

  5. Proliferation of East Antarctic Adélie penguins in response to historical deglaciation.

    Science.gov (United States)

    Younger, Jane; Emmerson, Louise; Southwell, Colin; Lelliott, Patrick; Miller, Karen

    2015-11-18

    Major, long-term environmental changes are projected in the Southern Ocean and these are likely to have impacts for marine predators such as the Adélie penguin (Pygoscelis adeliae). Decadal monitoring studies have provided insight into the short-term environmental sensitivities of Adélie penguin populations, particularly to sea ice changes. However, given the long-term nature of projected climate change, it is also prudent to consider the responses of populations to environmental change over longer time scales. We investigated the population trajectory of Adélie penguins during the last glacial-interglacial transition to determine how the species was affected by climate warming over millennia. We focussed our study on East Antarctica, which is home to 30 % of the global population of Adélie penguins. Using mitochondrial DNA from extant colonies, we reconstructed the population trend of Adélie penguins in East Antarctica over the past 22,000 years using an extended Bayesian skyline plot method. To determine the relationship of East Antarctic Adélie penguins with populations elsewhere in Antarctica we constructed a phylogeny using mitochondrial DNA sequences. We found that the Adélie penguin population expanded 135-fold from approximately 14,000 years ago. The population growth was coincident with deglaciation in East Antarctica and, therefore, an increase in ice-free ground suitable for Adélie penguin nesting. Our phylogenetic analysis indicated that East Antarctic Adélie penguins share a common ancestor with Adélie penguins from the Antarctic Peninsula and Scotia Arc, with an estimated age of 29,000 years ago, in the midst of the last glacial period. This finding suggests that extant colonies in East Antarctica, the Scotia Arc and the Antarctic Peninsula were founded from a single glacial refuge. While changes in sea ice conditions are a critical driver of Adélie penguin population success over decadal and yearly timescales, deglaciation appears to have

  6. Emerging spatial patterns in Antarctic prokaryotes

    Directory of Open Access Journals (Sweden)

    Chun Wie eChong

    2015-09-01

    Full Text Available Recent advances in knowledge of patterns of biogeography in terrestrial eukaryotic organisms have led to a fundamental paradigm shift in understanding of the controls and history of life on land in Antarctica, and its interactions over the long term with the glaciological and geological processes that have shaped the continent. However, while it has long been recognized that the terrestrial ecosystems of Antarctica are dominated by microbes and their processes, knowledge of microbial diversity and distributions has lagged far behind that of the macroscopic eukaryote organisms. Increasing human contact with and activity in the continent is leading to risks of biological contamination and change in a region whose isolation has protected it for millions of years at least; these risks may be particularly acute for microbial communities which have, as yet, received scant recognition and attention. Even a matter apparently as straightforward as Protected Area designation in Antarctica requires robust biodiversity data which, in most parts of the continent, remain almost completely unavailable. A range of important contributing factors mean that it is now timely to reconsider the state of knowledge of Antarctic terrestrial prokaryotes. Rapid advances in molecular biological approaches are increasingly demonstrating that bacterial diversity in Antarctica may be far greater than previously thought, and that there is overlap in the environmental controls affecting both Antarctic prokaryotic and eukaryotic communities. Bacterial dispersal mechanisms and colonization patterns remain largely unaddressed, although evidence for regional evolutionary differentiation is rapidly accruing and, with this, there is increasing appreciation of patterns in regional bacterial biogeography in this large part of the globe. In this review, we set out to describe the state of knowledge of Antarctic prokaryote diversity patterns, drawing analogy with those of eukaryote

  7. Super-aggregations of krill and humpback whales in Wilhelmina Bay, Antarctic Peninsula.

    Directory of Open Access Journals (Sweden)

    Douglas P Nowacek

    Full Text Available Ecological relationships of krill and whales have not been explored in the Western Antarctic Peninsula (WAP, and have only rarely been studied elsewhere in the Southern Ocean. In the austral autumn we observed an extremely high density (5.1 whales per km(2 of humpback whales (Megaptera novaeangliae feeding on a super-aggregation of Antarctic krill (Euphausia superba in Wilhelmina Bay. The krill biomass was approximately 2 million tons, distributed over an area of 100 km(2 at densities of up to 2000 individuals m(-3; reports of such 'super-aggregations' of krill have been absent in the scientific literature for >20 years. Retentive circulation patterns in the Bay entrained phytoplankton and meso-zooplankton that were grazed by the krill. Tagged whales rested during daylight hours and fed intensively throughout the night as krill migrated toward the surface. We infer that the previously unstudied WAP embayments are important foraging areas for whales during autumn and, furthermore, that meso-scale variation in the distribution of whales and their prey are important features of this system. Recent decreases in the abundance of Antarctic krill around the WAP have been linked to reductions in sea ice, mediated by rapid climate change in this area. At the same time, baleen whale populations in the Southern Ocean, which feed primarily on krill, are recovering from past exploitation. Consideration of these features and the effects of climate change on krill dynamics are critical to managing both krill harvests and the recovery of baleen whales in the Southern Ocean.

  8. Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

    Science.gov (United States)

    Genthon, Christophe; Piard, Luc; Vignon, Etienne; Madeleine, Jean-Baptiste; Casado, Mathieu; Gallée, Hubert

    2017-01-01

    Supersaturation often occurs at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high Antarctic Plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic Plateau is presented. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content, even in the case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the Antarctic Plateau are thus likely biased low. The measurements are compared with results from two models implementing cold microphysics parameterizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the two models, leaving much room for model improvement. This is unlikely to strongly affect estimations of surface sublimation because supersaturation is more frequent as temperature is lower, and moisture quantities and thus water fluxes are small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high-altitude cirrus clouds in meteorological and climate models.

  9. Penguin Proxies: Deciphering Millennial-Scale Antarctic Ecosystem Change using Amino Acid Stable Isotope Analysis.

    Science.gov (United States)

    Michelson, C.; McMahon, K.; Emslie, S. D.; Patterson, W. P.; McCarthy, M. D.; Polito, M. J.

    2017-12-01

    The Southern Ocean ecosystem is undergoing rapid environmental change due to ongoing and historic anthropogenic impacts such as climate change and marine mammal harvesting. These disturbances may have cascading effects through the Antarctic food webs, resulting in profound shifts in the sources and cycling of organic matter supporting higher-trophic organisms, such as penguins. For example, bulk stable isotope analyses of modern and ancient preserved penguin tissues suggest variations in penguin feeding ecology throughout the Holocene with dramatic isotopic shifts in the last 200 years. However, it is not clear whether these isotopic shifts resulted from changes at the base of the food web, dietary shifts in penguins, or some combination of both factors. Newly developed compound-specific stable nitrogen isotope analysis of individual amino acids (CSIA-AA) may provide a powerful new tool to tease apart these confounding variables. Stable nitrogen isotope values of trophic amino acids (e.g., glutamic acid) increase substantially with each trophic transfer in the food web, while source amino acid (e.g., phenylalanine) stable nitrogen isotope values remain relatively unchanged and reflect ecosystem baselines. As such, we can use this CSIA-AA approach to decipher between baseline and dietary shifts in penguins over time from modern and ancient eggshells of Pygoscelis penguins in the Antarctic Peninsula and the Ross Sea regions of Antarctica. In order to accurately apply this CSIA-AA approach, we first characterized the trophic fractionation factors of individual amino acids between diet and penguin consumers in a long-term controlled penguin feeding experiment. We then applied these values to modern and ancient eggshells from the Antarctic Peninsula and Ross Sea to evaluate shifts in penguin trophic dynamics as a function of climate and anthropogenic interaction throughout much of the Holocene. This work develops a cutting edge new molecular geochemistry approach

  10. Super-aggregations of krill and humpback whales in Wilhelmina Bay, Antarctic Peninsula.

    Science.gov (United States)

    Nowacek, Douglas P; Friedlaender, Ari S; Halpin, Patrick N; Hazen, Elliott L; Johnston, David W; Read, Andrew J; Espinasse, Boris; Zhou, Meng; Zhu, Yiwu

    2011-04-27

    Ecological relationships of krill and whales have not been explored in the Western Antarctic Peninsula (WAP), and have only rarely been studied elsewhere in the Southern Ocean. In the austral autumn we observed an extremely high density (5.1 whales per km(2)) of humpback whales (Megaptera novaeangliae) feeding on a super-aggregation of Antarctic krill (Euphausia superba) in Wilhelmina Bay. The krill biomass was approximately 2 million tons, distributed over an area of 100 km(2) at densities of up to 2000 individuals m(-3); reports of such 'super-aggregations' of krill have been absent in the scientific literature for >20 years. Retentive circulation patterns in the Bay entrained phytoplankton and meso-zooplankton that were grazed by the krill. Tagged whales rested during daylight hours and fed intensively throughout the night as krill migrated toward the surface. We infer that the previously unstudied WAP embayments are important foraging areas for whales during autumn and, furthermore, that meso-scale variation in the distribution of whales and their prey are important features of this system. Recent decreases in the abundance of Antarctic krill around the WAP have been linked to reductions in sea ice, mediated by rapid climate change in this area. At the same time, baleen whale populations in the Southern Ocean, which feed primarily on krill, are recovering from past exploitation. Consideration of these features and the effects of climate change on krill dynamics are critical to managing both krill harvests and the recovery of baleen whales in the Southern Ocean.

  11. Holocene accumulation and ice flow near the West Antarctic Ice Sheet Divide ice core site

    Science.gov (United States)

    Koutnik, Michelle R.; Fudge, T. J.; Conway, Howard; Waddington, Edwin D.; Neumann, Thomas A.; Cuffey, Kurt M.; Buizert, Christo; Taylor, Kendrick C.

    2016-05-01

    The West Antarctic Ice Sheet Divide Core (WDC) provided a high-resolution climate record from near the Ross-Amundsen Divide in Central West Antarctica. In addition, radar-detected internal layers in the vicinity of the WDC site have been dated directly from the ice core to provide spatial variations in the age structure of the region. Using these two data sets together, we first infer a high-resolution Holocene accumulation-rate history from 9.2 kyr of the ice-core timescale and then confirm that this climate history is consistent with internal layers upstream of the core site. Even though the WDC was drilled only 24 km from the modern ice divide, advection of ice from upstream must be taken into account. We evaluate histories of accumulation rate by using a flowband model to generate internal layers that we compare to observed layers. Results show that the centennially averaged accumulation rate was over 20% lower than modern at 9.2 kyr before present (B.P.), increased by 40% from 9.2 to 2.3 kyr B.P., and decreased by at least 10% over the past 2 kyr B.P. to the modern values; these Holocene accumulation-rate changes in Central West Antarctica are larger than changes inferred from East Antarctic ice-core records. Despite significant changes in accumulation rate, throughout the Holocene the regional accumulation pattern has likely remained similar to today, and the ice-divide position has likely remained on average within 5 km of its modern position. Continent-scale ice-sheet models used for reconstructions of West Antarctic ice volume should incorporate this accumulation history.

  12. The late Cainozoic East Antarctic ice sheet

    International Nuclear Information System (INIS)

    Colhoun, E.A.

    1999-01-01

    A review, mainly of East Antarctic late Cainozoic (post 40 Ma) geological and geomorphological evidence, supports the hypothesis of the continuous presence of an ice sheet, of about the present size, since the late Miocene. Evidence is presented and the view advanced that, during the late Wisconsin maximum of isotope stage 2, ice was not nearly as thick or extensive over the continental shelf as required by the model of 'maximum' Antarctic glaciation. Some of the factors influencing the contribution of Antarctica to post-glacial sea-level rise are discussed. It is considered that Antarctica's contribution was probably considerably less than previously estimated. The dating of marine and freshwater sequences in the Vestfold and Bunger Hills is consistent with deglaciation around the Pleistocene Holocene boundary, after the Late Wisconsin maximum. A date of ∼25 ka BP from permafrost in the Larsemann Hills means that either the Larsemann Hills were not glaciated during the Late Wisconsin or the ice failed to erode much of the permafrost surface. The degree of weathering of rock and glacial drifts in the Vestfold, Larsemann and Bunger Hills suggests a long time for formation, perhaps considerably longer than indicated by the dated marine and freshwater sediment sequences. Cosmogenic isotope dating in the Vestfold Hills has provided equivocal ages for deglaciation. While the results could indicate deglaciation before 80 ka BP, they do not confirm such early deglaciation. If the ice cover was thin and failed to remove the previous rock exposure profile, then the assays could predate the last ice advance. Weathered iron crust fragments in the till suggest little erosion. The raised beaches of the oases are Holocene. Assuming they have been produced by post Late Wisconsin isostatic uplift and by the Holocene transgression, calculations show that the Antarctic continental ice sheet could not have been more than ∼500 m thicker in the inner shelf-coastal zone. The

  13. Portable Habitat for Antarctic Scientific Research (PHASR)

    Science.gov (United States)

    Griswold, Samantha S.

    1992-01-01

    The Portable Habitat for Antarctic Scientific Research, PHASR, is designed as a versatile, general purpose habitat system that addresses the problem of functional space and environmental soundness in a partially fabric-covered shelter. PHASR is used for remote field site applications that can be quickly deployed. PHASR will also provide four scientists with a comfortable and efficient use of interior space. PHASR is a NASA/USRA Advanced Design Program project conducted at the University of Houston College of Architecture, Sasadawa International Center for Space Architecture (SICSA). This report is prepared for NASA/USRA.

  14. Ozone zonal asymmetry and planetary wave characterization during Antarctic spring

    Directory of Open Access Journals (Sweden)

    I. Ialongo

    2012-03-01

    Full Text Available A large zonal asymmetry of ozone has been observed over Antarctica during winter-spring, when the ozone hole develops. It is caused by a planetary wave-driven displacement of the polar vortex. The total ozone data by OMI (Ozone Monitoring Instrument and the ozone profiles by MLS (Microwave Limb Sounder and GOMOS (Global Ozone Monitoring by Occultation of Stars were analysed to characterize the ozone zonal asymmetry and the wave activity during Antarctic spring. Both total ozone and profile data have shown a persistent zonal asymmetry over the last years, which is usually observed from September to mid-December. The largest amplitudes of planetary waves at 65° S (the perturbations can achieve up to 50% of zonal mean values is observed in October. The wave activity is dominated by the quasi-stationary wave 1 component, while the wave 2 is mainly an eastward travelling wave. Wave numbers 1 and 2 generally explain more than the 90% of the ozone longitudinal variations. Both GOMOS and MLS ozone profile data show that ozone zonal asymmetry covers the whole stratosphere and extends up to the altitudes of 60–65 km. The wave amplitudes in ozone mixing ratio decay with altitude, with maxima (up to 50% below 30 km.

    The characterization of the ozone zonal asymmetry has become important in the climate research. The inclusion of the polar zonal asymmetry in the climate models is essential for an accurate estimation of the future temperature trends. This information might also be important for retrieval algorithms that rely on ozone a priori information.

  15. Environmental Variation and Cohort Effects in an Antarctic Predator

    Science.gov (United States)

    Garrott, Robert A.; Rotella, Jay J.; Siniff, Donald B.; Parkinson, Claire L.; Stauffer, Glenn E.

    2011-01-01

    ice associated with climate change, suggest significant alterations in Antarctic marine ecosystems in the future.

  16. Ice-sheet mass balance and climate change.

    Science.gov (United States)

    Hanna, Edward; Navarro, Francisco J; Pattyn, Frank; Domingues, Catia M; Fettweis, Xavier; Ivins, Erik R; Nicholls, Robert J; Ritz, Catherine; Smith, Ben; Tulaczyk, Slawek; Whitehouse, Pippa L; Zwally, H Jay

    2013-06-06

    Since the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, new observations of ice-sheet mass balance and improved computer simulations of ice-sheet response to continuing climate change have been published. Whereas Greenland is losing ice mass at an increasing pace, current Antarctic ice loss is likely to be less than some recently published estimates. It remains unclear whether East Antarctica has been gaining or losing ice mass over the past 20 years, and uncertainties in ice-mass change for West Antarctica and the Antarctic Peninsula remain large. We discuss the past six years of progress and examine the key problems that remain.

  17. Drivers of Antarctic sea-ice expansion and Southern Ocean surface cooling over the past four decades

    Science.gov (United States)

    Purich, Ariaan; England, Matthew

    2017-04-01

    Despite global warming, total Antarctic sea-ice coverage has increased overall during the past four decades. In contrast, the majority of CMIP5 models simulate a decline. In addition, Southern Ocean surface waters have largely cooled, in stark contrast to almost all historical CMIP5 simulations. Subantarctic Surface Waters have cooled and freshened while waters to the north of the Antarctic Circumpolar Current have warmed and increased in salinity. It remains unclear as to what extent the cooling and Antarctic sea-ice expansion is due to natural variability versus anthropogenic forcing; due for example to changes in the Southern Annular Mode (SAM). It is also unclear what the respective role of surface buoyancy fluxes is compared to internal ocean circulation changes, and what the implications are for longer-term climate change in the region. In this presentation we will outline three distinct drivers of recent Southern Ocean surface trends that have each made a significant contribution to regional cooling: (1) wind-driven surface cooling and sea-ice expansion due to shifted westerly winds, (2) teleconnections of decadal variability from the tropical Pacific, and (3) surface cooling and ice expansion due to large-scale Southern Ocean freshening, most likely driven by SAM-related precipitation trends over the open ocean. We will also outline the main reasons why climate models for the most part miss these Southern Ocean cooling trends, despite capturing overall trends in the SAM.

  18. Retail applications of signature verification

    Science.gov (United States)

    Zimmerman, Thomas G.; Russell, Gregory F.; Heilper, Andre; Smith, Barton A.; Hu, Jianying; Markman, Dmitry; Graham, Jon E.; Drews, Clemens

    2004-08-01

    The dramatic rise in identity theft, the ever pressing need to provide convenience in checkout services to attract and retain loyal customers, and the growing use of multi-function signature captures devices in the retail sector provides favorable conditions for the deployment of dynamic signature verification (DSV) in retail settings. We report on the development of a DSV system to meet the needs of the retail sector. We currently have a database of approximately 10,000 signatures collected from 600 subjects and forgers. Previous work at IBM on DSV has been merged and extended to achieve robust performance on pen position data available from commercial point of sale hardware, achieving equal error rates on skilled forgeries and authentic signatures of 1.5% to 4%.

  19. Password-based digital signatures

    OpenAIRE

    Sivagnanasuntharam, Sangeepan

    2013-01-01

    This thesis is about implementing a digital signature scheme proposed by associate professor Kristian Gjøsteen and Oystein Thuen.The thesis explains the implementation, the challenges met and a security assessment of the implementation.

  20. Initial Semantics for Strengthened Signatures

    Directory of Open Access Journals (Sweden)

    André Hirschowitz

    2012-02-01

    Full Text Available We give a new general definition of arity, yielding the companion notions of signature and associated syntax. This setting is modular in the sense requested by Ghani and Uustalu: merging two extensions of syntax corresponds to building an amalgamated sum. These signatures are too general in the sense that we are not able to prove the existence of an associated syntax in this general context. So we have to select arities and signatures for which there exists the desired initial monad. For this, we follow a track opened by Matthes and Uustalu: we introduce a notion of strengthened arity and prove that the corresponding signatures have initial semantics (i.e. associated syntax. Our strengthened arities admit colimits, which allows the treatment of the λ-calculus with explicit substitution.

  1. Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover

    Science.gov (United States)

    Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A.; Zhou, Mingyu; Lenschow, Donald H.; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua

    2017-04-01

    Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration.

  2. Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean.

    Science.gov (United States)

    Coxall, Helen K; Wilson, Paul A; Pälike, Heiko; Lear, Caroline H; Backman, Jan

    2005-01-06

    The ocean depth at which the rate of calcium carbonate input from surface waters equals the rate of dissolution is termed the calcite compensation depth. At present, this depth is approximately 4,500 m, with some variation between and within ocean basins. The calcite compensation depth is linked to ocean acidity, which is in turn linked to atmospheric carbon dioxide concentrations and hence global climate. Geological records of changes in the calcite compensation depth show a prominent deepening of more than 1 km near the Eocene/Oligocene boundary (approximately 34 million years ago) when significant permanent ice sheets first appeared on Antarctica, but the relationship between these two events is poorly understood. Here we present ocean sediment records of calcium carbonate content as well as carbon and oxygen isotopic compositions from the tropical Pacific Ocean that cover the Eocene/Oligocene boundary. We find that the deepening of the calcite compensation depth was more rapid than previously documented and occurred in two jumps of about 40,000 years each, synchronous with the stepwise onset of Antarctic ice-sheet growth. The glaciation was initiated, after climatic preconditioning, by an interval when the Earth's orbit of the Sun favoured cool summers. The changes in oxygen-isotope composition across the Eocene/Oligocene boundary are too large to be explained by Antarctic ice-sheet growth alone and must therefore also indicate contemporaneous global cooling and/or Northern Hemisphere glaciation.

  3. Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover.

    Science.gov (United States)

    Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A; Zhou, Mingyu; Lenschow, Donald H; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua

    2017-04-05

    Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration.

  4. When will the Antarctic Ozone Hole Recover?

    Science.gov (United States)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

    2006-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the .TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to, both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. The ozone hole will begin to show first signs of recovery in about 2023, and the hole will fully recover to pre-1980 levels in approximately 2070. This 2070 recovery is 20 years later than recent projections.

  5. CHAMP Magnetic Anomalies of the Antarctic Crust

    Science.gov (United States)

    Kim, Hyung Rae; Gaya-Pique, Luis R.; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo

    2003-01-01

    Regional magnetic signals of the crust are strongly masked by the core field and its secular variations components and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated- behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar regions relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects. To help isolate regional lithospheric from core field components, the correlations between CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations can also be exploited.. Employing these procedures, we processed the CHAMP magnetic observations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Orsted and noisier Magsat observations, the CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intracrustal magnetic features and crustal thickness variations of the Antarctic.

  6. Extremophiles in an Antarctic Marine Ecosystem

    Directory of Open Access Journals (Sweden)

    Iain Dickinson

    2016-01-01

    Full Text Available Recent attempts to explore marine microbial diversity and the global marine microbiome have indicated a large proportion of previously unknown diversity. However, sequencing alone does not tell the whole story, as it relies heavily upon information that is already contained within sequence databases. In addition, microorganisms have been shown to present small-to-large scale biogeographical patterns worldwide, potentially making regional combinations of selection pressures unique. Here, we focus on the extremophile community in the boundary region located between the Polar Front and the Southern Antarctic Circumpolar Current in the Southern Ocean, to explore the potential of metagenomic approaches as a tool for bioprospecting in the search for novel functional activity based on targeted sampling efforts. We assessed the microbial composition and diversity from a region north of the current limit for winter sea ice, north of the Southern Antarctic Circumpolar Front (SACCF but south of the Polar Front. Although, most of the more frequently encountered sequences  were derived from common marine microorganisms, within these dominant groups, we found a proportion of genes related to secondary metabolism of potential interest in bioprospecting. Extremophiles were rare by comparison but belonged to a range of genera. Hence, they represented interesting targets from which to identify rare or novel functions. Ultimately, future shifts in environmental conditions favoring more cosmopolitan groups could have an unpredictable effect on microbial diversity and function in the Southern Ocean, perhaps excluding the rarer extremophiles.

  7. Microbial biomass and basal respiration in Sub-Antarctic and Antarctic soils in the areas of some Russian polar stations

    Science.gov (United States)

    Abakumov, E.; Mukhametova, N.

    2014-03-01

    Antarctica is the unique place for pedological investigations. Soils of Antarctica have been studied intensively during the last century. Antarctic logistic provides the possibility to scientists access the terrestrial landscapes mainly in the places of polar stations. That is why the main and most detailed pedological investigations were conducted in Mc Murdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann hills and Schirmacher Oasis. Investigations were conducted during the 53rd and 55th Russian Antarctic expeditions on the base of soil pits and samples collected in Sub-Antarctic and Antarctic regions. Soils of diverse Antarctic landscapes were studied with aim to assess the microbial biomass level, basal respiration rates and metabolic activity of microbial communities. The investigation conducted shows that soils of Antarctic are quite different in profile organization and carbon content. In general, Sub-Antarctic soils are characterized by more developed humus (sod) organo-mineral horizons as well as the upper organic layer. The most developed organic layers were revealed in peat soils of King-George Island, where its thickness reach even 80 cm. These soils as well as soils under guano are characterized by the highest amount of total organic carbon (TOC) 7.22-33.70%. Coastal and continental soils of Antarctic are presented by less developed Leptosols, Gleysols, Regolith and rare Ornhitosol with TOC levels about 0.37-4.67%. The metabolic ratios and basal respiration were higher in Sub-Antarctic soils than in Antarctic ones which can be interpreted as result of higher amounts of fresh organic remnants in organic and organo-mineral horizons. Also the soils of King-George island have higher portion of microbial biomass (max 1.54 mg g-1) than coastal (max 0.26 mg g-1) and continental (max 0.22 mg g-1) Antarctic soils. Sub-Antarctic soils mainly differ from Antarctic ones in increased organic layers thickness and total organic carbon content

  8. Exposure age and ice-sheet model constraints on Pliocene East Antarctic ice sheet dynamics.

    Science.gov (United States)

    Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki

    2015-04-24

    The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East Antarctic Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from West Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea ice cover and inhibited active moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas.

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

    Science.gov (United States)

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

    2017-12-01

    -ice production in the Adélie and more widely. Our work provides a mechanism for rapid expansion of Antarctic sea ice with a background of a warming climate and highlights how better representation of meltwater inputs and sea ice dynamics will be fundamental to improving projections for future climate change in the Antarctic. Hein, et al,. Nat. Comms, 12511, 2016.

  10. The lithosphere of the Antarctic continent: new insights from satellite gravity gradient data

    Science.gov (United States)

    Ferraccioli, Fausto; Ebbing, Jorg; Pappa, Folker; Kern, Michael; Forsberg, Rene

    2017-04-01

    The GOCE+Antarctica project, part of the Support to Science (STSE) program of the European Space Agency (ESA) is a new polar geosciences research initiative that aims to investigate the thermal and compositional structure of the Antarctic lithosphere by combing satellite gravity gradients (Bouman et al., 2016), airborne gravity data compilations (Scheinert et al., 2016), seismological (e.g. An et al., 2015) and petrological models in a forward and inverse manner. This approach promises to shed new light into the fundamental interplays between Antarctic lithospheric architecture, bedrock topography, ice sheet dynamics, and also its dynamic relations with Glacial Isostatic Adjustment (GIA). Here we focus on the satellite gravity gradient signatures and superimpose these on major known tectonic and bedrock topography elements, as well as independent seismically-derived estimates of crustal thickness for the Antarctic continent. An ad hoc India up reference system was used to facilitate the initial interpretation of the satellite gravity gradient data images. The GIU component clearly reveals the marked contrast between the thinner crust and lithosphere underlying the West Antarctic Rift System and also the Weddell Sea Rift System and the thicker lithosphere of East Antarctica. Notably, the new images suggests that more distributed wide-mode lithospheric and crustal extension affects the Ross Sea Embayment and continues under the Ross Ice Shelf, but this pattern is less clear towards the Bellingshousen Embayment. This suggests that the rift system narrows considerably as it reaches the southern edge of the Antarctic Peninsula, perhaps also in response to the relatively thicker crust and potentially relatively more rigid Precambrian lithosphere of the displaced Haag-Ellsworth block, which was originally located closer to East Antarctica, prior to distributed Jurassic lithospheric and crustal extension in the Weddell Sea Rift System. In East Antarctica, the satellite

  11. SIGNATURE: A workbench for gene expression signature analysis

    Directory of Open Access Journals (Sweden)

    Chang Jeffrey T

    2011-11-01

    Full Text Available Abstract Background The biological phenotype of a cell, such as a characteristic visual image or behavior, reflects activities derived from the expression of collections of genes. As such, an ability to measure the expression of these genes provides an opportunity to develop more precise and varied sets of phenotypes. However, to use this approach requires computational methods that are difficult to implement and apply, and thus there is a critical need for intelligent software tools that can reduce the technical burden of the analysis. Tools for gene expression analyses are unusually difficult to implement in a user-friendly way because their application requires a combination of biological data curation, statistical computational methods, and database expertise. Results We have developed SIGNATURE, a web-based resource that simplifies gene expression signature analysis by providing software, data, and protocols to perform the analysis successfully. This resource uses Bayesian methods for processing gene expression data coupled with a curated database of gene expression signatures, all carried out within a GenePattern web interface for easy use and access. Conclusions SIGNATURE is available for public use at http://genepattern.genome.duke.edu/signature/.

  12. Simulating realistic predator signatures in quantitative fatty acid signature analysis

    Science.gov (United States)

    Bromaghin, Jeffrey F.

    2015-01-01

    Diet estimation is an important field within quantitative ecology, providing critical insights into many aspects of ecology and community dynamics. Quantitative fatty acid signature analysis (QFASA) is a prominent method of diet estimation, particularly for marine mammal and bird species. Investigators using QFASA commonly use computer simulation to evaluate statistical characteristics of diet estimators for the populations they study. Similar computer simulations have been used to explore and compare the performance of different variations of the original QFASA diet estimator. In both cases, computer simulations involve bootstrap sampling prey signature data to construct pseudo-predator signatures with known properties. However, bootstrap sample sizes have been selected arbitrarily and pseudo-predator signatures therefore may not have realistic properties. I develop an algorithm to objectively establish bootstrap sample sizes that generates pseudo-predator signatures with realistic properties, thereby enhancing the utility of computer simulation for assessing QFASA estimator performance. The algorithm also appears to be computationally efficient, resulting in bootstrap sample sizes that are smaller than those commonly used. I illustrate the algorithm with an example using data from Chukchi Sea polar bears (Ursus maritimus) and their marine mammal prey. The concepts underlying the approach may have value in other areas of quantitative ecology in which bootstrap samples are post-processed prior to their use.

  13. Adjustment of pigment composition in Desmarestia (Desmarestiaceae species along a sub-Antarctic to Antarctic latitudinal gradient

    Directory of Open Access Journals (Sweden)

    Andrés Mansilla

    2016-08-01

    Full Text Available Photosynthesis at high latitudes demands efficient strategies of light utilization to maintain algal fitness and performance. The fitness, and physiological adaptation, of a plant or algae species depends in part on the abundance and efficiency of the pigments it can produce to utilize the light resource from its environment. We quantified pigment composition and concentration in six species of the brown macroalgal genus Desmarestia, collected from sub-Antarctic sites (Strait of Magellan, Beagle Channel–Cape Horn Province and sites on the Antarctic Peninsula and adjacent islands. Sub-Antarctic Desmarestia species exhibited lower concentrations of chlorophyll a, chlorophyll c and fucoxanthin than endemic Antarctic species. Antarctic samples of D. menziesii and D. antarctica collected along a decreasing latitudinal gradient showed spatial and interspecific differences in light-harvesting pigment composition. Our results suggest distinct physiological adjustments in Desmarestia species in response to heterogeneous abiotic environmental conditions. The marine sub-Antarctic and Antarctic ecosystems are characterized by harsh environments (e.g., extreme irradiance, photoperiod, temperature, salinity to which the physiology of macroalgal species must adapt.

  14. Climate and energy

    International Nuclear Information System (INIS)

    Anon.

    1996-01-01

    The dossier on Climate and Energy encompasses contributions addressing the following topics: Climate research in Germany, perspectives of the energy of the future; Energy-conserving building design, construction and retrofitting; Companies developing ecological awareness and ecological performance; World population, energy consumption and greenhouse gas abatement; On the uncertainty involved in political evaluation of the global climate change; Economic aspects of the carbon dioxide issue; Ozone - polar stratospheres - clouds and ozone hole; Ozone - vertical ozone distribution in the antarctic region; Sudden climate change; Sulfate aerosols and climate change; Symptoms of the global climate change; IKARUS - greenhouse gas abatement strategies; Energy from fossil fuels; Renewable energy sources; Nuclear fusion; Is there a chance for nuclear energy?; Least-cost planning leading to energy-conserving power plants; Pleading for a sustainable energy economy; Why we both love and destroy nature. The concluding two contributions are interviews highlighting two statements: We will persist in our intention to achieve the declared objectives for greenhouse gas abatement, and: We cannot do without nuclear energy. (RHM) [de

  15. Recent Measurements of Ice Flux From Outlet Glaciers of the South Shetlands and Antarctic Peninsula

    Science.gov (United States)

    Koppes, M.; Hallet, B.; Rignot, E.; Jaffrey, M.

    2007-12-01

    One of the most significant events in the evolution of the Antarctic climate and cryosphere was the pronounced glacial erosion in the late Cenozoic that led to the considerable depth and landward sloping profile of the continental shelf, affecting both ice sheet dynamics and the oceanographic processes that drive circulation on the shelf. Understanding how changes in glacial conditions during the LGM may have led to enhanced glacial erosion, however, requires us to first identify the factors that control the amount and rate of glacier erosion in Antarctica today. The bays and fjords of the Antarctic Peninsula contain a rich history of climate change recorded both in proxy climate data (e.g., forams, oxygen isotopes) and in sediment accumulation rates that reflect changes in glacial erosion and sediment transfer. Prior studies revealed large variations in the rate of sediment accumulation across the Peninsula, with a general trend of decreasing sedimentation from north to south and west to east, attributed to climate-driven differences in glacier dynamics. Little is known to date, however, about the individual dynamics of the glaciers in these fjords, and the variability in their sediment delivery, particularly as many of them start to accelerate and retreat (Cook et al., 2005; Rignot, 1998; Angelis and Skvarca, 2003). As part of a study concerning the factors controlling rates of glacial erosion and sedimentation across climatic regimes, the cross-sectional area at the ELA of 16 tidewater glaciers in the South Shetland Islands and the western coast of the Antarctic Peninsula were measured in April 2007. The cross-section area of each glacier is then combined with the mean surface velocity, measured remotely using SAR interferometry, to reconstruct the contemporary ice flux through these glacier systems. The study area spans almost 4° of latitude and 8° of mean annual temperature, encompassing both sub-polar and polar regimes, from Maxwell Bay, South Shetland

  16. Signature molecular descriptor : advanced applications.

    Energy Technology Data Exchange (ETDEWEB)

    Visco, Donald Patrick, Jr. (Tennessee Technological University, Cookeville, TN)

    2010-04-01

    In this work we report on the development of the Signature Molecular Descriptor (or Signature) for use in the solution of inverse design problems as well as in highthroughput screening applications. The ultimate goal of using Signature is to identify novel and non-intuitive chemical structures with optimal predicted properties for a given application. We demonstrate this in three studies: green solvent design, glucocorticoid receptor ligand design and the design of inhibitors for Factor XIa. In many areas of engineering, compounds are designed and/or modified in incremental ways which rely upon heuristics or institutional knowledge. Often multiple experiments are performed and the optimal compound is identified in this brute-force fashion. Perhaps a traditional chemical scaffold is identified and movement of a substituent group around a ring constitutes the whole of the design process. Also notably, a chemical being evaluated in one area might demonstrate properties very attractive in another area and serendipity was the mechanism for solution. In contrast to such approaches, computer-aided molecular design (CAMD) looks to encompass both experimental and heuristic-based knowledge into a strategy that will design a molecule on a computer to meet a given target. Depending on the algorithm employed, the molecule which is designed might be quite novel (re: no CAS registration number) and/or non-intuitive relative to what is known about the problem at hand. While CAMD is a fairly recent strategy (dating to the early 1980s), it contains a variety of bottlenecks and limitations which have prevented the technique from garnering more attention in the academic, governmental and industrial institutions. A main reason for this is how the molecules are described in the computer. This step can control how models are developed for the properties of interest on a given problem as well as how to go from an output of the algorithm to an actual chemical structure. This report

  17. Evolution of the eastward shift in the quasi-stationary minimum of the Antarctic total ozone column

    Science.gov (United States)

    Grytsai, Asen; Klekociuk, Andrew; Milinevsky, Gennadi; Evtushevsky, Oleksandr; Stone, Kane

    2017-02-01

    The quasi-stationary pattern of the Antarctic total ozone has changed during the last 4 decades, showing an eastward shift in the zonal ozone minimum. In this work, the association between the longitudinal shift of the zonal ozone minimum and changes in meteorological fields in austral spring (September-November) for 1979-2014 is analyzed using ERA-Interim and NCEP-NCAR reanalyses. Regressive, correlative and anomaly composite analyses are applied to reanalysis data. Patterns of the Southern Annular Mode and quasi-stationary zonal waves 1 and 3 in the meteorological fields show relationships with interannual variability in the longitude of the zonal ozone minimum. On decadal timescales, consistent longitudinal shifts of the zonal ozone minimum and zonal wave 3 pattern in the middle-troposphere temperature at the southern midlatitudes are shown. Attribution runs of the chemistry-climate version of the Australian Community Climate and Earth System Simulator (ACCESS-CCM) model suggest that long-term shifts of the zonal ozone minimum are separately contributed by changes in ozone-depleting substances and greenhouse gases. As is known, Antarctic ozone depletion in spring is strongly projected on the Southern Annular Mode in summer and impacts summertime surface climate across the Southern Hemisphere. The results of this study suggest that changes in zonal ozone asymmetry accompanying ozone depletion could be associated with regional climate changes in the Southern Hemisphere in spring.

  18. Photosynthesis in a sub-Antarctic shore-zone lichen

    NARCIS (Netherlands)

    Smith, V.; Gremmen, N.J.M.

    2001-01-01

    Photosynthetic responses to moisture, light, temperature, salinity and inorganic nitrogen fertilization are reported for a shore-zone lichen Turgidiusculum complicatulum (formerly Mastodia tesselata), a possible recent introduction to sub-Antarctic Marion Island. Optimum moisture contents for net

  19. Radarsat Antarctic Mapping Project Digital Elevation Model, Version 2

    Data.gov (United States)

    National Aeronautics and Space Administration — The high-resolution Radarsat Antarctic Mapping Project (RAMP) Digital Elevation Model (DEM) combines topographic data from a variety of sources to provide consistent...

  20. Antarctic Active Subglacial Lake Inventory from ICESat Altimetry, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains lake boundaries, volume changes, and gridded elevations for 124 active subglacial lakes beneath the Antarctic ice sheet. Lakes were identified...

  1. Antarctic Glacial Chronology: New Constraints from Surface Exposure Dating

    National Research Council Canada - National Science Library

    Ackert, Robert

    2000-01-01

    .... New He-3 production rates are determined from a 125 ka lava flow. Measurements of inherited He-3/He-4 in two common Antarctic lithologies allow measurement of exposure ages < 6000 years. At Mt...

  2. University of Wisconsin Antarctic Soils Database, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The University of Wisconsin Antarctic Soils Database contains data collected by Dr. James G. Bockheim and his colleagues from 1975 through 1987. Data include site...

  3. Morphogenesis of Antarctic Paleosols: Martian Analogue

    Science.gov (United States)

    Mahaney, W. C.; Dohm, J. M.; Baker, V. R.; Newsom, Horton E.; Malloch, D.; Hancock, R. G. V.; Campbell, Iain; Sheppard, D.; Milner, M. W.

    2001-11-01

    Samples of horizons in paleosols from the Quartermain Mountains of the Antarctic Dry Valleys (Aztec and New Mountain areas) were analyzed for their physical characteristics, mineralogy, chemical composition, and microbiology to determine the accumulation and movement of salts and other soluble constituents and the presence/absence of microbial populations. Salt concentrations are of special interest because they are considered to be a function of age, derived over time, in part from nearby oceanic and high-altitude atmospheric sources. The chemical composition of ancient Miocene-age paleosols in these areas is the direct result of the deposition and weathering of airborne-influxed salts and other materials, as well as the weathering of till derived principally from local dolerite and sandstone outcrops. Paleosols nearer the coast have greater contents of Cl, whereas near the inland ice sheet, nitrogen tends to increase on a relative basis. The accumulation and vertical distribution of salts and other soluble chemical elements indicate relative amounts of movement in the profile over long periods of time, in the order of several million years. Four of the six selected subsamples from paleosol horizons in two ancient soil profiles contained nil concentrations of bacteria and fungi. However, two horizons at depths of between 3 and 8 cm, in two profiles, yielded several colonies of the fungi Beauveria bassiana and Penicillium brevicompactum, indicating very minor input of organic carbon. Beauveria bassiana is often reported in association with insects and is used commercially for the biological control of some insect pests. Penicillium species are commonly isolated from Arctic, temperate, and tropical soils and are known to utilize a wide variety of organic carbon and nitrogen compounds. The cold, dry soils of the Antarctic bear a close resemblance to various present and past martian environments where similar weathering could occur and possible microbial populations

  4. Fundamental differences between Arctic and Antarctic ozone depletion

    OpenAIRE

    Solomon, Susan; Haskins, Jessica; Ivy, Diane J.; Min, Flora

    2014-01-01

    Fundamental differences in observed ozone depletion between the Arctic and the Antarctic are shown, clarifying distinctions between both average and extreme ozone decreases in the two hemispheres. Balloon-borne and satellite measurements in the heart of the ozone layer near 18−24 km altitude show that extreme ozone decreases often observed in the Antarctic ozone hole region have not yet been measured in the Arctic in any year, including the unusually cold Arctic spring of 2011. The data provi...

  5. Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean.

    Science.gov (United States)

    Menezes, Viviane V; Macdonald, Alison M; Schatzman, Courtney

    2017-01-01

    Southern Ocean abyssal waters, in contact with the atmosphere at their formation sites around Antarctica, not only bring signals of a changing climate with them as they move around the globe but also contribute to that change through heat uptake and sea level rise. A repeat hydrographic line in the Indian sector of the Southern Ocean, occupied three times in the last two decades (1994, 2007, and, most recently, 2016), reveals that Antarctic Bottom Water (AABW) continues to become fresher (0.004 ± 0.001 kg/g decade -1 ), warmer (0.06° ± 0.01°C decade -1 ), and less dense (0.011 ± 0.002 kg/m 3 decade -1 ). The most recent observations in the Australian-Antarctic Basin show a particularly striking acceleration in AABW freshening between 2007 and 2016 (0.008 ± 0.001 kg/g decade -1 ) compared to the 0.002 ± 0.001 kg/g decade -1 seen between 1994 and 2007. Freshening is, in part, responsible for an overall shift of the mean temperature-salinity curve toward lower densities. The marked freshening may be linked to an abrupt iceberg-glacier collision and calving event that occurred in 2010 on the George V/Adélie Land Coast, the main source region of bottom waters for the Australian-Antarctic Basin. Because AABW is a key component of the global overturning circulation, the persistent decrease in bottom water density and the associated increase in steric height that result from continued warming and freshening have important consequences beyond the Southern Indian Ocean.

  6. Atmospheric moisture supersaturatons in the near-surface atmosphere of Dome C, Antarctic Plateau

    Science.gov (United States)

    Genthon, Christophe; Piard, Luc; Vignon, Etienne; Madeleine, Jean-Baptiste; Casado, Mathieu; Gallée, Hubert

    2017-04-01

    Moisture supersaturations occur at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high antarctic plateau. This study presents one year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic plateau. The measurements are obtained using commercial hygrometry sensors adapted to allow air sampling without affecting the moisture content even in case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the antarctic plateau are thus likely biased low. The measurements are compared with results from 2 models with cold microphysics parametrizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the 2 models, leaving much room for model improvement. The representation of supersaturations is not critical for the estimations of surface sublimation since they are more frequent as temperature is lower i.e. as moisture quantities and water fluxes are small. However, ignoring near-surface supersaturation may be a more serious issue for the modeling of fog and when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high altitude cirrus clouds in

  7. Permafrost and Active Layer Monitoring in the Maritime Antarctic: A Contribution to TSP and ANTPAS projects

    Science.gov (United States)

    Vieira, G.; Ramos, M.; Batista, V.; Caselli, A.; Correia, A.; Fragoso, M.; Gruber, S.; Hauck, C.; Kenderova, R.; Lopez-Martinez, J.; Melo, R.; Mendes-Victor, L. A.; Miranda, P.; Mora, C.; Neves, M.; Pimpirev, C.; Rocha, M.; Santos, F.; Blanco, J. J.; Serrano, E.; Trigo, I.; Tome, D.; Trindade, A.

    2008-12-01

    Permafrost and active layer monitoring in the Maritime Antarctic (PERMANTAR) is a Portuguese funded International Project that, in cooperation with the Spanish project PERMAMODEL, will assure the installation and the maintenance of a network of boreholes and active layer monitoring sites, in order to characterize the spatial distribution of the physical and thermal properties of permafrost, as well as the periglacial processes in Livingston and Deception Islands (South Shetlands). The project is part of the International Permafrost Association IPY projects Thermal State of Permafrost (TSP) and Antarctic and Sub-Antarctic Permafrost, Soils and Periglacial Environments (ANTPAS). It contributes to GTN-P and CALM-S networks. The PERMANTAR-PERMAMODEL permafrost and active layer monitoring network includes several boreholes: Reina Sofia hill (since 2000, 1.1m), Incinerador (2000, 2.3m), Ohridski 1 (2008, 5m), Ohridski 2 (2008, 6m), Gulbenkian-Permamodel 1 (2008, 25m) and Gulbenkian- Permamodel 2 (2008, 15m). For active layer monitoring, several CALM-S sites have been installed: Crater Lake (2006), Collado Ramos (2007), Reina Sofia (2007) and Ohridski (2007). The monitoring activities are accompanied by detailed geomorphological mapping in order to identify and map the geomorphic processes related to permafrost or active layer dynamics. Sites will be installed in early 2009 for monitoring rates of geomorphological activity in relation to climate change (e.g. solifluction, rockglaciers, thermokarst). In order to analyse the spatial distribution of permafrost and its ice content, electrical resistivity tomography (ERT), and seismic refraction surveys have been performed and, in early 2009, continuous ERT surveying instrumentation will be installed for monitoring active layer evolution. The paper presents a synthesis of the activities, as well as the results obtained up to the present, mainly relating to ground temperature monitoring and from permafrost characteristics and

  8. Transcriptomics and comparative analysis of three antarctic notothenioid fishes.

    Directory of Open Access Journals (Sweden)

    Seung Chul Shin

    Full Text Available For the past 10 to 13 million years, Antarctic notothenioid fish have undergone extraordinary periods of evolution and have adapted to a cold and highly oxygenated Antarctic marine environment. While these species are considered an attractive model with which to study physiology and evolutionary adaptation, they are poorly characterized at the molecular level, and sequence information is lacking. The transcriptomes of the Antarctic fishes Notothenia coriiceps, Chaenocephalus aceratus, and Pleuragramma antarcticum were obtained by 454 FLX Titanium sequencing of a normalized cDNA library. More than 1,900,000 reads were assembled in a total of 71,539 contigs. Overall, 40% of the contigs were annotated based on similarity to known protein or nucleotide sequences, and more than 50% of the predicted transcripts were validated as full-length or putative full-length cDNAs. These three Antarctic fishes shared 663 genes expressed in the brain and 1,557 genes expressed in the liver. In addition, these cold-adapted fish expressed more Ub-conjugated proteins compared to temperate fish; Ub-conjugated proteins are involved in maintaining proteins in their native state in the cold and thermally stable Antarctic environments. Our transcriptome analysis of Antarctic notothenioid fish provides an archive for future studies in molecular mechanisms of fundamental genetic questions, and can be used in evolution studies comparing other fish.

  9. Potential of the solid-Earth response for limiting long-term West Antarctic Ice Sheet retreat

    Science.gov (United States)

    Konrad, Hannes; Sasgen, Ingo; Pollard, David; Klemann, Volker

    2016-04-01

    The West Antarctic Ice Sheet (WAIS) is assumed to be inherently unstable because it is grounded below sea level in a large part, where the bedrock deepens from today's grounding line towards the interior of the ice sheet. Idealized simulations have shown that bedrock uplift due to isostatic adjustment of the solid Earth and the associated sea-level fall may stop the retreat of such a marine-based ice sheet (Gomez et al., 2012). Here, we employ a coupled model for ice-sheet dynamics and solid-Earth dynamics, including a gravitationally consistent description of sea level, to investigate the influence of the viscoelastic Earth structure on the WAIS' future stability (Konrad et al. 2015). For this, we start from a steady-state condition for the Antarctic Ice Sheet close to present-day observations and apply atmospheric and oceanic forcing of different strength to initiate the retreat of the WAIS and investigate the effect of the viscoelastic deformation on the ice evolution for a range of solid-Earth rheologies. We find that the climate forcing is the primary control on the occurrence of the WAIS collapse. However, for moderate climate forcing and a weak solid-Earth rheology associated with the West Antarctic rift system (asthenosphere viscosities of 3x10^19 Pa s or less), we find that the combined effect of bedrock uplift and gravitational sea-level fall limits the retreat to the Amundsen Sea embayment on millennial time scales. In contrast, a stiffer Earth rheology yields a collapse under these conditions. Under a stronger climate forcing, weak Earth structures do not prevent the WAIS collapse; however, they produce a delay of up to 5000 years in comparison to a stiffer solid-Earth rheology. In an additional experiment, we test the impact of sea-level rise from an assumed fast deglaciation of the Greenland Ice Sheet. In cases when the climatic forcing is too weak to force WAIS collapse by itself, the additional rise in sea-level leads to disintegration of the WAIS

  10. Parasites of the Antarctic toothfish (Dissostichus mawsoni Norman, 1937 (Perciformes, Nototheniidae in the Pacific sector of the Antarctic

    Directory of Open Access Journals (Sweden)

    Ilya I. Gordeev

    2016-06-01

    Full Text Available The Antarctic toothfish (Dissostichus mawsoni Norman, 1937 is one of the main target species of commercial fisheries in the Antarctic. It is an endemic and is found along the shelf of Antarctica, as well as on the slopes of seamounts, underwater elevations and islands in the sub-Antarctic. It feeds on a variety of fish and cephalopods and can be an intermediate/paratenic host of some helminthes, whose final hosts are whales, seals, large rays and sharks. This article presents new data on toothfish infection in the Pacific sector of the Antarctic. Specimens were examined during commercial longline fishing in the Ross Sea and the Amundsen Sea in January–February 2013. Fourteen species of parasites were found using standard parasitological methods and genetic analysis.

  11. A long term strategy for Antarctic tourism : The key to decision making within the Antarctic Treaty System?

    NARCIS (Netherlands)

    Bastmeijer, C.J.; Maher, P.; Stewart, E.; Lück, M.

    2011-01-01

    The fast increase of Antarctic tourism raises various management questions. Questions relating to the safety of tourists, questions regarding the interaction between science and tourism and questions relating to direct, indirect or cumulative affects on Antarctica's environment and wilderness

  12. Antarctic sea ice variability using NASA team algorithm data

    Science.gov (United States)

    Barreira, S.; Compagnucci, R.

    Sea ice is an important, highly variable feature of the Earth's surface, both reflecting and influencing climatic conditions. Sea ice covers approximately 7 percent of the world oceans, significantly reduces the amount of solar radiation absorbed at the Earth's surface, greatly restricts the transfer of heat from the ocean to the atmosphere in winter, and influences global atmospheric and oceanic circulation. In this paper, monthly through interannual variability of the sea ice between 0 and 120W is analysed for the 22-year period 1979 through 2000. The monthly Polar Gridded Sea Ice Concentrations data set derived from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and the Defense Meteorological Satellite Program's (DMSP) DMSP-F8, F11 and F13, Special Sensor Microwave/Imager (SSM/I) generated by NASA team algorithm were used. This data were acquired from the National Snow and Ice Data Center (NSIDC) and are gridded on the SSM/I polar stereographic grid (25 x 25 km) provided in two-byte integer format. Principal Components Analysis in T-Mode was performed on pre-processed sea ice data (anomalies from which have been removed continent and perennial open water), in order to investigate which are the main space patterns, when do they present and how they are coupled to different atmospheric variables. This analysis provide 12 patterns (6 in direct mode and 6 in inverse mode) that represent the most important spatial features that dominate sea ice variability in the Weddell, Amudsen and Bellinghausen Seas. These 12 patterns, or their combinations, describe completely the behavior of the 264 month means sea ice concentration anomalies of the record we used of the selected Antarctic region.

  13. Five Guidelines for Selecting Hydrological Signatures

    Science.gov (United States)

    McMillan, H. K.; Westerberg, I.; Branger, F.

    2017-12-01

    Hydrological signatures are index values derived from observed or modeled series of hydrological data such as rainfall, flow or soil moisture. They are designed to extract relevant information about hydrological behavior, such as to identify dominant processes, and to determine the strength, speed and spatiotemporal variability of the rainfall-runoff response. Hydrological signatures play an important role in model evaluation. They allow us to test whether particular model structures or parameter sets accurately reproduce the runoff generation processes within the watershed of interest. Most modeling studies use a selection of different signatures to capture different aspects of the catchment response, for example evaluating overall flow distribution as well as high and low flow extremes and flow timing. Such studies often choose their own set of signatures, or may borrow subsets of signatures used in multiple other works. The link between signature values and hydrological processes is not always straightforward, leading to uncertainty and variability in hydrologists' signature choices. In this presentation, we aim to encourage a more rigorous approach to hydrological signature selection, which considers the ability of signatures to represent hydrological behavior and underlying processes for the catchment and application in question. To this end, we propose a set of guidelines for selecting hydrological signatures. We describe five criteria that any hydrological signature should conform to: Identifiability, Robustness, Consistency, Representativeness, and Discriminatory Power. We describe an example of the design process for a signature, assessing possible signature designs against the guidelines above. Due to their ubiquity, we chose a signature related to the Flow Duration Curve, selecting the FDC mid-section slope as a proposed signature to quantify catchment overall behavior and flashiness. We demonstrate how assessment against each guideline could be used to

  14. Atmospheric sulfur and climate changes: a modelling study at mid and high-southern latitudes

    International Nuclear Information System (INIS)

    Castebrunet, H.

    2007-09-01

    The mid and high-southern latitudes are still marginally affected by anthropogenic sulfur emissions. They are the only regions in the world where the natural cycle of the atmospheric sulfur may still be observed. Sulfur aerosols are well-known for their radiative impact, and thus interact with climate. Climate can in turn affect atmospheric sulfur sources, distribution and chemistry. Antarctic ice cores provide information on the evolution of climate and sulfur deposition at the surface of the ice sheet at glacial-interglacial time scales. The aim of this thesis is to develop and use modeling towards a better understanding of the atmospheric sulfur cycle in antarctic and sub-antarctic regions. Ice core data are used to validate model results under glacial climate conditions. An Atmospheric General Circulation Model (AGCM) coupled to a sulfur chemistry module is used: the LMD-ZTSulfur model, version 4. An update of both the physical and chemical parts of the model. The model was first performed. The impact of there changes on modelled sulfur cycle are evaluated for modern climate. Further, boundary conditions are adapted to simulate the atmospheric circulation and sulfur cycle at the Last Glacial Maximum, approximately 20,000 years ago. In the model, sulfur is found to be highly sensitive to antarctic sea-ice coverage, which is still poorly known during the ice age. An original dataset of ice-age sea-ice coverage was developed. Its impact on the oceanic emissions of dimethyl sulfide, main precursor of sulfur aerosols at high-southern latitudes, is discussed. Using the same oceanic sulfur reservoirs as for present day climate, the model broadly reproduces the glacial deposits of sulfur aerosols on the Antarctic plateau, suggesting little impact of climate on oceanic sulfur production in the Antarctic region. Sensitivity tests were carried out to draw an up-to-date status of major uncertainties and difficulties facing future progress in understanding atmospheric

  15. High resolution climate reconstructions of recent warming using instrumental and ice core records from coastal Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Thamban, M.; Naik, S.S.; Laluraj, C.M.; Ravindra, R.

    . These ice records provided insights on the influence of solar forcing on Antarctic climate system as well as its linkages with the tropical and mid-latitude climatic modes like the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO...

  16. Initiation and long-term instability of the East Antarctic Ice Sheet

    Science.gov (United States)

    Gulick, Sean P. S.; Shevenell, Amelia E.; Montelli, Aleksandr; Fernandez, Rodrigo; Smith, Catherine; Warny, Sophie; Bohaty, Steven M.; Sjunneskog, Charlotte; Leventer, Amy; Frederick, Bruce; Blankenship, Donald D.

    2017-12-01

    Antarctica’s continental-scale ice sheets have evolved over the past 50 million years. However, the dearth of ice-proximal geological records limits our understanding of past East Antarctic Ice Sheet (EAIS) behaviour and thus our ability to evaluate its response to ongoing environmental change. The EAIS is marine-terminating and grounded below sea level within the Aurora subglacial basin, indicating that this catchment, which drains ice to the Sabrina Coast, may be sensitive to climate perturbations. Here we show, using marine geological and geophysical data from the continental shelf seaward of the Aurora subglacial basin, that marine-terminating glaciers existed at the Sabrina Coast by the early to middle Eocene epoch. This finding implies the existence of substantial ice volume in the Aurora subglacial basin before continental-scale ice sheets were established about 34 million years ago. Subsequently, ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs. Tunnel valleys associated with half of these glaciations indicate that a surface-meltwater-rich sub-polar glacial system existed under climate conditions similar to those anticipated with continued anthropogenic warming. Cooling since the late Miocene resulted in an expanded polar EAIS and a limited glacial response to Pliocene warmth in the Aurora subglacial basin catchment. Geological records from the Sabrina Coast shelf indicate that, in addition to ocean temperature, atmospheric temperature and surface-derived meltwater influenced East Antarctic ice mass balance under warmer-than-present climate conditions. Our results imply a dynamic EAIS response with continued anthropogenic warming and suggest that the EAIS contribution to future global sea-level projections may be under-estimated.

  17. A new source of Southern Ocean and Antarctic aerosol from tropospheric polar cell chemistry of sea ice emissions

    Science.gov (United States)

    Humphries, R. S.; Klekociuk, A. R.; Schofield, R.; Robinson, A. D.; Harris, N. R. P.; Keywood, M.; Ward, J.; Galbally, I.; Molloy, S.; Thomas, A.; Wilson, S. R.

    2014-12-01

    and the contribution of Antarctic aerosol production to global loading. As climate change intensifies and the ozone hole recovers, the Antarctic polar front may shift latitudes, potentially changing Antarctic and regional aerosol loading, resulting in changes to tropospheric and stratospheric chemistry and radiative budgets.

  18. Satellite mapping and automated feature extraction: Geographic information system-based change detection of the Antarctic coast

    Science.gov (United States)

    Kim, Kee-Tae

    Declassified Intelligence Satellite Photograph (DISP) data are important resources for measuring the geometry of the coastline of Antarctica. By using the state-of-art digital imaging technology, bundle block triangulation based on tie points and control points derived from a RADARSAT-1 Synthetic Aperture Radar (SAR) image mosaic and Ohio State University (OSU) Antarctic digital elevation model (DEM), the individual DISP images were accurately assembled into a map quality mosaic of Antarctica as it appeared in 1963. The new map is one of important benchmarks for gauging the response of the Antarctic coastline to changing climate. Automated coastline extraction algorithm design is the second theme of this dissertation. At the pre-processing stage, an adaptive neighborhood filtering was used to remove the film-grain noise while preserving edge features. At the segmentation stage, an adaptive Bayesian approach to image segmentation was used to split the DISP imagery into its homogenous regions, in which the fuzzy c-means clustering (FCM) technique and Gibbs random field (GRF) model were introduced to estimate the conditional and prior probability density functions. A Gaussian mixture model was used to estimate the reliable initial values for the FCM technique. At the post-processing stage, image object formation and labeling, removal of noisy image objects, and vectorization algorithms were sequentially applied to segmented images for extracting a vector representation of coastlines. Results were presented that demonstrate the effectiveness of the algorithm in segmenting the DISP data. In the cases of cloud cover and little contrast scenes, manual editing was carried out based on intermediate image processing and visual inspection in comparison of old paper maps. Through a geographic information system (GIS), the derived DISP coastline data were integrated with earlier and later data to assess continental scale changes in the Antarctic coast. Computing the area of

  19. Ca isotopic geochemistry of an Antarctic aquatic system

    Science.gov (United States)

    Lyons, W. Berry; Bullen, Thomas D.; Welch, Kathleen A.

    2017-01-01

    The McMurdo Dry Valleys, Antarctica, are a polar desert ecosystem. The hydrologic system of the dry valleys is linked to climate with ephemeral streams that flow from glacial melt during the austral summer. Past climate variations have strongly influenced the closed-basin, chemically stratified lakes on the valley floor. Results of previous work point to important roles for both in-stream processes (e.g., mineral weathering, precipitation and dissolution of salts) and in-lake processes (e.g., mixing with paleo-seawater and calcite precipitation) in determining the geochemistry of these lakes. These processes have a significant influence on calcium (Ca) biogeochemistry in this aquatic ecosystem, and thus variations in Ca stable isotope compositions of the waters can aid in validating the importance of these processes. We have analyzed the Ca stable isotope compositions of streams and lakes in the McMurdo Dry Valleys. The results validate the important roles of weathering of aluminosilicate minerals and/or CaCO3 in the hyporheic zone of the streams, and mixing of lake surface water with paleo-seawater and precipitation of Ca-salts during cryo-concentration events to form the deep lake waters. The lakes in the McMurdo Dry Valleys evolved following different geochemical pathways, evidenced by their unique, nonsystematic Ca isotope signatures.

  20. (137)Cs concentrations in Atlantic and western Antarctic surface waters: results of the 7th Ukrainian Antarctic Expedition, 2002.

    Science.gov (United States)

    Gulin, S B; Stokozov, N A

    2005-01-01

    The latitudinal distribution of (137)Cs in the Atlantic--western Antarctic surface waters was studied during the 7th Ukrainian Antarctic Expedition in January--May 2002. The (137)Cs concentrations have also been measured in the upper ice of the coastal glacier Woozle Hill located near the Ukrainian Antarctic station "Akademik Vernadsky" (western Antarctica, 65 degrees 15' S-64 degrees 16' W). Comparison of these data with results of previous same-route expeditions SWEDARP (Swedish Antarctic Research Expedition, 1988/1989) and the French R/V "Jeanne d'Arc" (1992/1993), has shown practically parallel changes of (137)Cs surface concentrations between 40 degrees N and 20 degrees S, pointing to decrease of (137)Cs radioactivity at these latitudes with an apparent half-life of 10--15 years (12.5+/-2.1 years on average). This suggests that decrease of (137)Cs surface concentration within this latitude band is controlled, besides the radioactive decay of (137)Cs (half-life=30 years), by vertical mixing of the upper water masses. South of 20 degrees S, the (137)Cs concentrations in surface water have decreased more rapidly because of the influence of the less contaminated Antarctic waters. At 50--60 degrees S and near the Antarctic coast, the (137)Cs activity in 2002 was similar to those measured during the SWEDARP and "Jeanne d'Arc" expeditions, suggesting an additional input of (137)Cs to these waters from the melted ice from the adjacent glaciers.

  1. Re-assessing the influence of glacial-isostatic adjustment on Antarctic ice-mass balance estimated from GRACE

    Science.gov (United States)

    Konrad, H.; Sasgen, I.; Klemann, V.; Ivins, E. R.; Martinec, Z.

    2012-04-01

    Satellite gravimetry observations of the contemporary ice-mass balance in Antarctica are strongly influenced by mass movements in the Earth interior induced by ice-load variations during the last glacial cycle, i.e. the glacial-isostatic adjustment (GIA). Newly available GPS observations collected within the POLENET project (www.polenet.org) represent a valuable constraint on GIA models predicting surface deformation and gravity-field change in Antarctica. Here, we re-assess the influence of GIA on Antarctic ice-mass balance estimated from the Gravity Recovery and Climate Experiment (GRACE). For this, we apply a viscoelastic Earth model, accounting for the rheological differences between East and West Antarctica, to three independent glacial histories ICE-5G (Peltier, 2004), IJ05 (Ivins & James, 2005) and HUY (Huybrechts, 2002). We predict the associated Antarctic GIA signal. With a stochastic approach, the glacial histories are regionally modified to satisfy GPS, GRACE as well as the combination of both observation types. We assess the influence of constraining GIA with GPS/GRACE on the reduction of the error budget of Antarctic ice-mass balances from GRACE.

  2. Interaction of ice sheets and climate on geological time scales

    NARCIS (Netherlands)

    Stap, L.B.

    2017-01-01

    Since the inception of the Antarctic ice sheet at the Eocene-Oligocene Transition (~34 Myr ago), land ice plays a crucial role in Earth’s climate. Through the ice-albedo and surface-height-temperature feedbacks, land ice variability strengthens atmospheric temperature changes induced by orbital and

  3. Motif signatures of transcribed enhancers

    KAUST Repository

    Kleftogiannis, Dimitrios

    2017-09-14

    In mammalian cells, transcribed enhancers (TrEn) play important roles in the initiation of gene expression and maintenance of gene expression levels in spatiotemporal manner. One of the most challenging questions in biology today is how the genomic characteristics of enhancers relate to enhancer activities. This is particularly critical, as several recent studies have linked enhancer sequence motifs to specific functional roles. To date, only a limited number of enhancer sequence characteristics have been investigated, leaving space for exploring the enhancers genomic code in a more systematic way. To address this problem, we developed a novel computational method, TELS, aimed at identifying predictive cell type/tissue specific motif signatures. We used TELS to compile a comprehensive catalog of motif signatures for all known TrEn identified by the FANTOM5 consortium across 112 human primary cells and tissues. Our results confirm that distinct cell type/tissue specific motif signatures characterize TrEn. These signatures allow discriminating successfully a) TrEn from random controls, proxy of non-enhancer activity, and b) cell type/tissue specific TrEn from enhancers expressed and transcribed in different cell types/tissues. TELS codes and datasets are publicly available at http://www.cbrc.kaust.edu.sa/TELS.

  4. Signature simulation of mixed materials

    Science.gov (United States)

    Carson, Tyler D.; Salvaggio, Carl

    2015-05-01

    Soil target signatures vary due to geometry, chemical composition, and scene radiometry. Although radiative transfer models and function-fit physical models may describe certain targets in limited depth, the ability to incorporate all three signature variables is difficult. This work describes a method to simulate the transient signatures of soil by first considering scene geometry synthetically created using 3D physics engines. Through the assignment of spectral data from the Nonconventional Exploitation Factors Data System (NEFDS), the synthetic scene is represented as a physical mixture of particles. Finally, first principles radiometry is modeled using the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model. With DIRSIG, radiometric and sensing conditions were systematically manipulated to produce and record goniometric signatures. The implementation of this virtual goniometer allows users to examine how a target bidirectional reflectance distribution function (BRDF) will change with geometry, composition, and illumination direction. By using 3D computer graphics models, this process does not require geometric assumptions that are native to many radiative transfer models. It delivers a discrete method to circumnavigate the significant cost of time and treasure associated with hardware-based goniometric data collections.

  5. Epigenetic Signatures of Cigarette Smoking

    NARCIS (Netherlands)

    R. Joehanes (Roby); Just, A.C. (Allan C.); R.E. Marioni (Riccardo); L.C. Pilling (Luke); L.M. Reynolds (Lindsay); Mandaviya, P.R. (Pooja R.); W. Guan (Weihua); Xu, T. (Tao); C.E. Elks (Cathy); Aslibekyan, S. (Stella); H. Moreno-Macías (Hortensia); J.A. Smith (Jennifer A); J. Brody (Jennifer); Dhingra, R. (Radhika); P. Yousefi (Paul); J.S. Pankow (James); Kunze, S. (Sonja); Shah, S.H. (Sonia H.); A.F. McRae (Allan F.); K. Lohman (Kurt); Sha, J. (Jin); D. Absher (Devin); L. Ferrucci (Luigi); Zhao, W. (Wei); E.W. Demerath (Ellen); J. Bressler (Jan); M.L. Grove (Megan); T. Huan (Tianxiao); C. Liu (Chunyu); Mendelson, M.M. (Michael M.); C. Yao (Chen); D.P. Kiel (Douglas P.); A. Peters (Annette); R. Wang-Sattler (Rui); P.M. Visscher (Peter); N.R. Wray (Naomi); J.M. Starr (John); Ding, J. (Jingzhong); Rodriguez, C.J. (Carlos J.); N.J. Wareham (Nick); Irvin, M.R. (Marguerite R.); Zhi, D. (Degui); M. Barrdahl (Myrto); P. Vineis (Paolo); Ambatipudi, S. (Srikant); A.G. Uitterlinden (André); A. Hofman (Albert); Schwartz, J. (Joel); Colicino, E. (Elena); Hou, L. (Lifang); Vokonas, P.S. (Pantel S.); D.G. Hernandez (Dena); A. Singleton (Andrew); S. Bandinelli (Stefania); S.T. Turner (Stephen); E.B. Ware (Erin B.); Smith, A.K. (Alicia K.); T. Klengel (Torsten); E.B. Binder (Elisabeth B.); B.M. Psaty (Bruce); K.D. Taylor (Kent); S.A. Gharib (Sina); Swenson, B.R. (Brenton R.); Liang, L. (Liming); D.L. Demeo (Dawn L.); G.T. O'Connor (George); Z. Herceg (Zdenko); Ressler, K.J. (Kerry J.); K.N. Conneely (Karen N.); N. Sotoodehnia (Nona); Kardia, S.L.R. (Sharon L. R.); D. Melzer (David); A.A. Baccarelli (Andrea A.); J.B.J. van Meurs (Joyce); I. Romieu (Isabelle); D.K. Arnett (Donna); Ong, K.K. (Ken K.); Y. Liu (YongMei); M. Waldenberger (Melanie); I.J. Deary (Ian J.); M. Fornage (Myriam); D. Levy (Daniel); S.J. London (Stephanie J.)

    2016-01-01

    textabstractBackground-DNA methylation leaves a long-term signature of smoking exposure and is one potential mechanism by which tobacco exposure predisposes to adverse health outcomes, such as cancers, osteoporosis, lung, and cardiovascular disorders. Methods and Results-To comprehensively determine

  6. Signature Pedagogy in Theatre Arts

    Science.gov (United States)

    Kornetsky, Lisa

    2017-01-01

    Critique in undergraduate theatre programs is at the heart of training actors at all levels. It is accepted as the signature pedagogy and is practiced in multiple ways. This essay defines critique and presents the case for why it is used as the single most important way that performers come to understand the language, values, and discourse of the…

  7. Galaxy interactions : The HI signature

    NARCIS (Netherlands)

    Sancisi, R; Barnes, JE; Sanders, DB

    1999-01-01

    HI observations are an excellent tool for investigating tidal interactions. Ongoing major and minor interactions which can lead to traumatic mergers or to accretion and the triggering of star formation, show distinct HI signatures. Interactions and mergers in the recent past can also be recognized

  8. Carbon and Nitrogen Use Efficiency in Microbial Communities in Antarctic Soils

    Science.gov (United States)

    Prommer, Judith; Spohn, Marie; Klaus, Karoline; Kusch, Stephanie; Wanek, Wolfgang; Dercon, Gerd; Richter, Andreas

    2016-04-01

    Terrestrial ecosystems in the Antarctic experience harsh environmental conditions including very low temperatures and a low carbon input leading to poorly developed ecosystems with low diversity and a low soil organic matter content, which may be vulnerable to perturbations in a future climate. Microbial transformation and decomposition of soil organic matter under the extreme climatic conditions in the Antarctic has received little attention so far. Specifically, little is known about microbial process rates and how they might be affected by climate warming. We here report on C and N transformation rates and their corresponding microbial use efficiencies in two soil horizons of two sites on King George Island, the maritime Antarctica. We used novel isotope techniques to estimate microbial carbon use efficiency (CUE; based on incorporation of 18O from water into DNA) and nitrogen use efficiency (NUE; based on a 15N isotope pool dilution assays). The investigated two contrasting sites at marine terraces on basaltic rocks that were characterized by a stable surface. While both sites were similar in exposition, distance from sea and elevation, they differed in their vegetation cover and several biogeochemical parameters, such as soil pH and soil organic carbon and nitrogen content. Surprisingly, we found low soil C:N ratios at both sites and for both horizons, i.e. below 12 in the organic crust and below 8 in the first mineral horizon. This indicates a low carbon availability relative to nitrogen and would thus imply a high microbial CUE. However, our results showed also a low CUE at both sites and in both horizons (CUE of 24% and 9% in the organic crust and mineral layer, respectively). In contrast, NUE was very high in organic layers (98%), pointing towards a strong nitrogen limitation, while in the mineral horizons, NUE was lower (between 84% and 72%), as expected for soil horizons with a C:N ratio below 8. Thus, the NUE pattern followed stoichiometric theory (i

  9. Exploring the data constrained phase space of the last Antarctic glacial cycle

    Science.gov (United States)

    Lecavalier, Benoit; Tarasov, Lev

    2017-04-01

    The evolution of the Antarctic Ice Sheet over the last two glacial cycles is studied using the Glacial Systems Model (GSM). Glaciological modelling is an effective tool to generate continental-scale reconstructions over glacial cycles, but the models depend on parameterizations to account for the deficiencies (e.g., missing physics, unresolved sub-grid processes, uncertain boundary conditions) inherent in any numerical model. These parameters, considered together, form a parameter phase space from which sets of parameters can be sampled; each set corresponds to an ice sheet reconstruction. The GSM has been updated with a number of recent developments: hybrid SIA-SSA physics, Schoof grounding line parameterization, broadened degrees of freedom in the climate forcing, sub-shelf melt explicitly dependent on ocean temperatures, improved hydrofracturing, cliff failure at the margins, basal topographic uncertainties, impact of basal drag roughness and subgrid statistics, and first order geoidal corrections in the coupled glacial isostatic adjustment component. Parametric uncertainties are defined in the GSM using >36 ensemble parameters. Prior to conducting a full Bayesian calibration, one must first validate the ability of the GSM to simulate a broad range of responses. We attempt this by latin hypercube sampling of the parameter phase space and comparing the model predictions against our constraint database consisting of past elevation, extent and relative sea level observations and the present day geometry. We document the capability of the GSM to envelope the observational constraints given the parametric uncertainties and discuss the implications for the evolution of the Antarctic Ice Sheet.

  10. Dating Antarctic soils using atmosphere-derived 10Be and nitrate

    International Nuclear Information System (INIS)

    Graham, I.J.; Ditchburn, R.G.; Claridge, G.G.C.; Whitehead, N.E.; Zondervan, A.; Sheppard, D.S.

    2002-01-01

    Because they are slow forming, Antarctic soils have the potential to yield considerable climatic information from the past c.20 m.y. However, these soils have proved difficult to date absolutely by conventional means. Here we present a novel approach to the problem, based on atmosphere-derived 10 Be and nitrate contents. In situations where medium to long term deposition rates can be reasonably estimated from ice core data, the total nitrate inventory in an Antarctic soil can place constraints on its formation age. 10 Be radioactive decay may then be used, assuming steady state equilibrium, to further refine the age profile. We have applied such models to a complex soil from the Taylor Valley region in South Victoria Land, deriving an overall nitrate inventory age of c. 18 Ma, and 10 Be decay ages for the upper and middle layers of c.15 and c.17 Ma, respectively. These results are consistent with the >10 Ma age of the soil deduced from stratigraphic and geomorphological information. (author). 28 refs., 4 figs., 2 tabs

  11. Resolving the Antarctic contribution to sea-level rise: a hierarchical modelling framework.

    Science.gov (United States)

    Zammit-Mangion, Andrew; Rougier, Jonathan; Bamber, Jonathan; Schön, Nana

    2014-06-01

    Determining the Antarctic contribution to sea-level rise from observational data is a complex problem. The number of physical processes involved (such as ice dynamics and surface climate) exceeds the number of observables, some of which have very poor spatial definition. This has led, in general, to solutions that utilise strong prior assumptions or physically based deterministic models to simplify the problem. Here, we present a new approach for estimating the Antarctic contribution, which only incorporates descriptive aspects of the physically based models in the analysis and in a statistical manner. By combining physical insights with modern spatial statistical modelling techniques, we are able to provide probability distributions on all processes deemed to play a role in both the observed data and the contribution to sea-level rise. Specifically, we use stochastic partial differential equations and their relation to geostatistical fields to capture our physical understanding and employ a Gaussian Markov random field approach for efficient computation. The method, an instantiation of Bayesian hierarchical modelling, naturally incorporates uncertainty in order to reveal credible intervals on all estimated quantities. The estimated sea-level rise contribution using this approach corroborates those found using a statistically independent method. © 2013 The Authors. Environmetrics Published by John Wiley & Sons, Ltd.

  12. Changes in ice dynamics and mass balance of the Antarctic ice sheet.

    Science.gov (United States)

    Rignot, Eric

    2006-07-15

    The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 degrees C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.

  13. Environmental drivers of viral community composition in Antarctic soils identified by viromics.

    Science.gov (United States)

    Adriaenssens, Evelien M; Kramer, Rolf; Van Goethem, Marc W; Makhalanyane, Thulani P; Hogg, Ian; Cowan, Don A

    2017-07-19

    The Antarctic continent is considered the coldest and driest place on earth with simple ecosystems, devoid of higher plants. Soils in the ice-free regions of Antarctica are known to harbor a wide range of microorganisms from primary producers to grazers, yet their ecology and particularly the role of viruses is poorly understood. In this study, we examined the virus community structures of 14 soil samples from the Mackay Glacier region. Viral communities were extracted from soil and the dsDNA was extracted, amplified using single-primer amplification, and sequenced using the Ion Torrent Proton platform. Metadata on soil physico-chemistry was collected from all sites. Both read and contig datasets were analyzed with reference-independent and reference-dependent methods to assess viral community structures and the influence of environmental parameters on their distribution. We observed a high heterogeneity in virus signatures, independent of geographical proximity. Tailed bacteriophages were dominant in all samples, but the incidences of the affiliated families Siphoviridae and Myoviridae were inversely correlated, suggesting direct competition for hosts. Viruses of the families Phycodnaviridae and Mimiviridae were present at significant levels in high-diversity soil samples and were found to co-occur, implying little competition between them. Combinations of soil factors, including pH, calcium content, and site altitude, were found to be the main drivers of viral community structure. The pattern of viral community structure with higher levels of diversity at lower altitude and pH, and co-occurring viral families, suggests that these cold desert soil viruses interact with each other, the host, and the environment in an intricate manner, playing a potentially crucial role in maintaining host diversity and functioning of the microbial ecosystem in the extreme environments of Antarctic soil.

  14. Tropospheric entrainment as a source of ground level aerosols within the polar Antarctic cell

    Science.gov (United States)

    Humphries, R. S.; Schofield, R.; Keywood, M.; Wilson, S. R.; Klekociuk, A. R.; Paton-Walsh, C.

    2013-12-01

    region which, being a sea-ice/ocean region, is a significant precursor source compared to the continent. After tropospheric formation, populations descending at the poles are transported northward and reach the surface at the edge of the continent. Current measurements of Antarctic aerosol suggest very low loading which may be explained by these circulation patterns and as such, may underestimate the total loading in this region as well as the contribution of aerosol production in this region to global loading. As climate change intensifies and the ozone hole recovers, the polar Antarctic front may shift latitudes, potentially changing Antarctic aerosol loading, resulting in changes to tropospheric and stratospheric chemistry and reducing transport to other global regions.

  15. Model calculations of the age of firn air across the Antarctic continent

    Directory of Open Access Journals (Sweden)

    K. A. Kaspers

    2004-01-01

    Full Text Available The age of firn air in Antarctica at pore close-off depth is only known for a few specific sites where firn air has been sampled for analyses. We present a model that calculates the age of firn air at pore close-off depth for the entire Antarctic continent. The model basically uses four meteorological parameters as input (surface temperature, pressure, accumulation rate and wind speed. Using parameterisations for surface snow density, pore close-off density and tortuosity, in combination with a density-depth model and data of a regional atmospheric climate model, distribution of pore close-off depth for the entire Antarctic continent is determined. The deepest pore close-off depth was found for the East Antarctic Plateau near 72° E, 82° S, at 150±15 m (2σ. A firn air diffusion model was applied to calculate the age of CO2 at pore close-off depth. The results predict that the oldest firn gas (CO2 age is located between Dome Fuji, Dome Argos and Vostok at 43° E, 78° S being 148±23 (1σ or 38 for 2σ years old. At this location an atmospheric trace gas record should be obtained. In this study we show that methyl chloride could be recorded with a predicted length of 125 years as an example for trace gas records at this location. The longest record currently available from firn air is derived at South Pole, being 80 years. Sensitivity tests reveal that the locations with old firn air (East Antarctic Plateau have an estimated uncertainty (2σ for the modelled CO2 age at pore close-off depth of 30% and of about 40% for locations with younger firn air (CO2 age typically 40 years. Comparing the modelled age of CO2 at pore close-off depth with directly determined ages at seven sites yielded a correlation coefficient of 0.90 and a slope close to 1, suggesting a high level of confidence for the modelled results in spite of considerable remaining uncertainties.

  16. U-Series Disequilibria across the New Southern Ocean Mantle Province, Australian-Antarctic Ridge

    Science.gov (United States)

    Scott, S. R.; Sims, K. W. W.; Park, S. H.; Langmuir, C. H.; Lin, J.; Kim, S. S.; Blichert-Toft, J.; Michael, P. J.; Choi, H.; Yang, Y. S.

    2017-12-01

    Mid-ocean ridge basalts (MORB) provide a unique window into the temporal and spatial scales of mantle evolution. Long-lived radiogenic isotopes in MORB have demonstrated that the mantle contains many different chemical components or "flavors". U-series disequilibria in MORB have further shown that different chemical components/lithologies in the mantle contribute differently to mantle melting processes beneath mid-ocean ridges. Recent Sr, Nd, Hf, and Pb isotopic analyses from newly collected basalts along the Australian-Antarctic Ridge (AAR) have revealed that a large distinct mantle province exists between the Australian-Antarctic Discordance and the Pacific-Antarctic Ridge, extending from West Antarctica and Marie Byrd Land to New Zealand and Eastern Australia (Park et al., submitted). This southern mantle province is located between the Indian-type mantle and the Pacific-type mantle domains. U-series measurements in the Southeast Indian Ridge and East Pacific Rise provinces show distinct signatures suggestive of differences in melting processes and source lithology. To examine whether the AAR mantle province also exhibits different U-series systematics we have measured U-Th-Ra disequilibria data on 38 basalts from the AAR sampled along 500 km of ridge axis from two segments that cross the newly discovered Southern Ocean Mantle province. We compare the data to those from nearby ridge segments show that the AAR possesses unique U-series disequilibria, and are thus undergoing distinct mantle melting dynamics relative to the adjacent Pacific and Indian ridges. (230Th)/(238U) excesses in zero-age basalts (i.e., those with (226Ra)/(230Th) > 1.0) range from 1.3 to 1.7, while (226Ra)/(230Th) ranges from 1.0 to 2.3. (226Ra)/(230Th) and (230Th)/(238U) are negatively correlated, consistent with the model of mixing between deep and shallow melts. The AAR data show higher values of disequilibria compared to the Indian and Pacific Ridges, which can be explained by either

  17. Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic.

    Science.gov (United States)

    Tremblin, Maxime; Hermoso, Michaël; Minoletti, Fabrice

    2016-10-18

    Growth of the first permanent Antarctic ice sheets at the Eocene-Oligocene Transition (EOT), ∼33.7 million years ago, indicates a major climate shift within long-term Cenozoic cooling. The driving mechanisms that set the stage for this glaciation event are not well constrained, however, owing to large uncertainties in temperature reconstructions during the Eocene, especially at lower latitudes. To address this deficiency, we used recent developments in coccolith biogeochemistry to reconstruct equatorial Atlantic sea surface temperature (SST) and atmospheric pCO 2 values from pelagic sequences preceding and spanning the EOT. We found significantly more variability in equatorial SSTs than previously reported, with pronounced cooling from the Early to Middle Eocene and subsequent warming during the Late Eocene. Thus, we show that the Antarctic glaciation at the Eocene-Oligocene boundary was preceded by a period of heat accumulation in the low latitudes, likely focused in a progressively contracting South Atlantic gyre, which contributed to cooling high-latitude austral regions. This prominent redistribution of heat corresponds to the emplacement of a strong meridional temperature gradient that typifies icehouse climate conditions. Our equatorial coccolith-derived geochemical record thus highlights an important period of global climatic and oceanic upheaval, which began 4 million years before the EOT and, superimposed on a long-term pCO 2 decline, drove the Earth system toward a glacial tipping point in the Cenozoic.

  18. Is it Becoming Warmer and Wetter in the Antarctic? A Look at Evaporation from the Southern Ocean

    Science.gov (United States)

    Boisvert, L.; Shie, C. L.

    2017-12-01

    The process of evaporation provides water vapor from the surface to the atmosphere, where it becomes the most radiatively important and abundant greenhouse gas altering the Earth's energy balance. Hence evaporation plays an essential role in a wide variety of atmospheric and oceanic problems. Evaporation is a key component of both the water cycle and the surface energy balance and thus information on this process is crucial in understanding the interaction between the atmosphere and oceans, global energy and water cycle variability, and in improving model simulations of climate variations. Although evaporation is an important term in climate model physics it is often poorly captured because surface in-situ measurements of evaporation are scarce in both space and time, especially over the Polar Regions, because evaporation is not easily measured directly. The Antarctic sea ice acts as a barrier between the ocean and atmosphere inhibiting the exchange of heat, momentum, and moisture. However, variations in the sea ice cover could lead to changes in the amount of moisture supplied to the atmosphere. Variations in the sea ice coverage could potentially allow for larger vertical moisture fluxes that affect surface energy budgets, larger occurrences of low-level clouds, and higher near-surface humidity and temperatures. These changes to the local atmosphere could then potentially impact nearby atmospheric conditions over the Antarctic ice sheet, which could be particularly important in regions that are susceptible to collapse like the West Antarctic Ice Sheet. NASA's Atmospheric Infrared Sounder (AIRS) has been used in multiple studies to study sea-ice atmosphere interactions in the Arctic Ocean with great success, specifically in evaporation (i.e. the moisture flux). However, little research has been done looking at the moisture flux from the Antarctic sea ice pack and nearby areas of the Southern Ocean. This work will use data from AIRS and the moisture flux scheme

  19. Some oceanographic observations in the polynya and along a section in the southwest Indian/ Antarctic Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.

    , silicate, pH and alkalinity through Antarctic, subantarctic and subtropical zones are presented and discussed. The Antarctic Divergence is observed appreciably to the south of its previously reported positions around 20~'E longitude, indicating some...

  20. US International Trans-Antarctic Scientific Expedition (US ITASE) Glaciochemical Data, Version 2

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains sub-annually resolved ice core chemistry data from various sites on the Antarctic Ice Sheet during the US International Trans-Antarctic...

  1. Online Signature Verification on MOBISIG Finger-Drawn Signature Corpus

    Directory of Open Access Journals (Sweden)

    Margit Antal

    2018-01-01

    Full Text Available We present MOBISIG, a pseudosignature dataset containing finger-drawn signatures from 83 users captured with a capacitive touchscreen-based mobile device. The database was captured in three sessions resulting in 45 genuine signatures and 20 skilled forgeries for each user. The database was evaluated by two state-of-the-art methods: a function-based system using local features and a feature-based system using global features. Two types of equal error rate computations are performed: one using a global threshold and the other using user-specific thresholds. The lowest equal error rate was 0.01% against random forgeries and 5.81% against skilled forgeries using user-specific thresholds that were computed a posteriori. However, these equal error rates were significantly raised to 1.68% (random forgeries case and 14.31% (skilled forgeries case using global thresholds. The same evaluation protocol was performed on the DooDB publicly available dataset. Besides verification performance evaluations conducted on the two finger-drawn datasets, we evaluated the quality of the samples and the users of the two datasets using basic quality measures. The results show that finger-drawn signatures can be used by biometric systems with reasonable accuracy.

  2. Skip spawning as a reproductive strategy in Antarctic fish species: the Antarctic silverfish (Pleuragramma antarctica case study

    Directory of Open Access Journals (Sweden)

    Eva Pisano

    2015-11-01

    Full Text Available The Antarctic silverfish Pleuragramma antarctica (Notothenioidei, Nototheniidae is the most abundant pelagic fish inhabiting the frigid Antarctic coastal waters. It plays relevant roles in the local ecosystems, where it is often considered a keystone species connecting lower and upper trophic levels within the coastal marine food web. Despite its ecological relevance, and although many aspects of the Antarctic silverfish biology have already been elucidated, knowledge on important components of its life cycle, including the reproductive features, is still poor. The available data on the reproduction of the Antarctic silverfish remains fragmentary and, in particular, information on the silverfish from the Ross Sea is lacking, in spite of the intensive ecological studies on this unique region and the fact that the only known nursery ground for this species is located in Terra Nova Bay (Ross Sea where hatching occurs under the sea-ice. We present the here first description of the reproductive features of Antarctic silverfish from fish sampled in late Summer (mid February 2008 in the Ross Sea. The gross reproductive traits are consistent with those reported from other Antarctic sectors but, interestingly, widespread follicular atresia has been detected in the fish examined. The intensity and prevalence of such a follicular degenerative process suggest that skip spawning (not all adults spawn every year could be a reproductive strategy of this Antarctic species. Such an hypothesis is discussed both on the short-term and on the evolutionary time-scale. Overall, the data presented also contribute to support the acknowledgment that skip-spawning is a diffuse phenomenon in fishes.

  3. A new paradigm of quantifying ecosystem stress through chemical signatures

    Energy Technology Data Exchange (ETDEWEB)

    Kravitz, Ben [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, P.O. Box 999, MSIN K9-30 Richland Washington 99352 USA; Guenther, Alex B. [Department of Earth System Science, University of California Irvine, 3200 Croul Hall Street Irvine California 92697 USA; Gu, Lianhong [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831 USA; Karl, Thomas [Institute of Atmospheric and Crysopheric Sciences, University of Innsbruck, Innrain 52f A-6020 Innsbruck Austria; Kaser, Lisa [National Center for Atmospheric Research, P.O. Box 3000 Boulder Colorado 80307 USA; Pallardy, Stephen G. [Department of Forestry, University of Missouri, 203 Anheuser-Busch Natural Resources Building Columbia Missouri 65211 USA; Peñuelas, Josep [CREAF, Cerdanyola del Vallès 08193 Catalonia Spain; Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Vallès 08193 Catalonia Spain; Potosnak, Mark J. [Department of Environmental Science and Studies, DePaul University, McGowan South, Suite 203 Chicago Illinois 60604 USA; Seco, Roger [Department of Earth System Science, University of California Irvine, 3200 Croul Hall Street Irvine California 92697 USA

    2016-11-01

    Stress-induced emissions of biogenic volatile organic compounds (VOCs) from terrestrial ecosystems may be one of the dominant sources of VOC emissions world-wide. Understanding the ecosystem stress response could reveal how ecosystems will respond and adapt to climate change and, in turn, quantify changes in the atmospheric burden of VOC oxidants and secondary organic aerosols. Here we argue, based on preliminary evidence from several opportunistic measurement sources, that chemical signatures of stress can be identified and quantified at the ecosystem scale. We also outline future endeavors that we see as next steps toward uncovering quantitative signatures of stress, including new advances in both VOC data collection and analysis of "big data."

  4. Antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore South Australia

    Science.gov (United States)

    Calvo, Eva; Pelejero, Carles; De Deckker, Patrick; Logan, Graham A.

    2007-07-01

    Comparison of ice cores from Greenland and Antarctica shows an asynchronous two-step warming at these high latitudes during the Last Termination. However, the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the Southern Hemisphere. New data from a marine core collected off South Australia (~36°S) allows a detailed reconstruction of sea-surface temperatures over the Last Termination. This confirms the existence of an Antarctic-type deglacial pattern and shows no indication of cooling associated with the Northern Hemisphere YD event. The SST record also provides a new comparison with the more extensive paleoclimatic data available from continental Australia. This shows a strong climatic link between onshore and offshore records for Australia and to Southern Hemisphere paleorecords. We also show a progressive SST drop over the last ~6.5 kyr not seen before for the Australian region.

  5. Carbon dynamics modelization and biological community sensitivity to temperature in an oligotrophic freshwater Antarctic lake

    DEFF Research Database (Denmark)

    Antonio Villaescusa, Juan; Jorgensen, Sven Erik; Rochera, Carlos

    2016-01-01

    , and therefore its abundance in lake water, greatly increased when temperature rise was higher. However, the highly variable meteorology over years in such an extreme environment causes that our model may fit well for some years, but fails to describe the system in years with contrasting meteorological...... conditions. Despite this assumption, the model reveals that maritime Antarctic lakes are very sensitive to temperature changes. This response can be monitored using eco-exergy, which allows a description of the system complexity. Due to this temperature sensitivity, the warming occurring in this area would...... interannual variability in the area of Byers Peninsula. With the aim of increasing the knowledge of this ecosystem and its sensibility to climate change as a model ecosystem, as well as to calibrate the extent of the interannual variability, a carbon flow model was developed partly describing its microbial...

  6. Summer diet of the Salvin's prion at sub-Antarctic Marion Island

    African Journals Online (AJOL)

    1988-02-14

    Feb 14, 1988 ... Thirty-nine food samples were collected from Salvin's prions Pachyptila salvini at sub-Antarctic Marion Island,. Prince Edward Islands. ..... guide to foraging methods used by marine birds in. Antarctic and sub-Antarctic seas. BIOMASS Handbook. 24: 1-22. GRINDLEY, J.R. & LANE, S.B. 1979. Zooplankton.

  7. Nonlinear control of magnetic signatures

    Science.gov (United States)

    Niemoczynski, Bogdan

    Magnetic properties of ferrite structures are known to cause fluctuations in Earth's magnetic field around the object. These fluctuations are known as the object's magnetic signature and are unique based on the object's geometry and material. It is a common practice to neutralize magnetic signatures periodically after certain time intervals, however there is a growing interest to develop real time degaussing systems for various applications. Development of real time degaussing system is a challenging problem because of magnetic hysteresis and difficulties in measurement or estimation of near-field flux data. The goal of this research is to develop a real time feedback control system that can be used to minimize magnetic signatures for ferrite structures. Experimental work on controlling the magnetic signature of a cylindrical steel shell structure with a magnetic disturbance provided evidence that the control process substantially increased the interior magnetic flux. This means near field estimation using interior sensor data is likely to be inaccurate. Follow up numerical work for rectangular and cylindrical cross sections investigated variations in shell wall flux density under a variety of ambient excitation and applied disturbances. Results showed magnetic disturbances could corrupt interior sensor data and magnetic shielding due to the shell walls makes the interior very sensitive to noise. The magnetic flux inside the shell wall showed little variation due to inner disturbances and its high base value makes it less susceptible to noise. This research proceeds to describe a nonlinear controller to use the shell wall data as an input. A nonlinear plant model of magnetics is developed using a constant tau to represent domain rotation lag and a gain function k to describe the magnetic hysteresis curve for the shell wall. The model is justified by producing hysteresis curves for multiple materials, matching experimental data using a particle swarm algorithm, and

  8. Scientific aspects of climate change

    International Nuclear Information System (INIS)

    Sanchez, G.

    2007-01-01

    For the last 35 years, the average temperature of the planet has been steadily increasing- Are the greenhouse gases emitted by human beings the cause? What will the consequences be? What can we do? The fourth report of the intergovernmental Panel on Climate change tries to answer these questions. There are clear signs of thawing that primary affect Greenland and the Antarctic, but there are still many doubts what the consequences will be throughout the century. In any case, it seems obvious that, if greenhouse gas emissions are not substantially reduced very soon, the rising temperature trend and its associated consequences will persist beyond the 21st century. (Author)

  9. Antarctic fish in a changing world: metabolic, osmoregulatory and endocrine stress response

    Directory of Open Access Journals (Sweden)

    Pedro Miguel Guerreiro

    2015-10-01

    Full Text Available Fish around Antarctic Peninsula are exposed to the fastest climate change rate in the planet, up to ten times higher than the global average. The evolution in extreme stenothermal isolation was a strong selective pressure for the development of a highly endemic fish fauna, with likely structural and functional constraints. To which extent can coastal notothenioid fish adjust to the conditions forecasted by the models of climate change? Experiments were run in the Arctowski (PL station at Admiralty Bay, King George Island, in 2012/13. Fish, Notothenia rossii and N. coriiceps, were collected by boat at 5-25 meter deep using fishing poles and were transferred to experimental tanks in cold rooms acclimated to natural temperatures (0-2°C. Fish were exposed to rapid/ gradual changes in water temperature or/and salinity (to 6-8°C using thermostat-controlled heaters, to 20-10‰ by addition of freshwater to recirculating tanks, over a period of up to 10 days to evaluate the response of several physiological processes. The stress endocrine axis was tested by injecting known blockers/ agonists of cortisol release and receptors. Exposure to altered conditions had no effect in immediate mortality. Increased temperature reduced overall activity and behavioral response to stimuli, although it had no clear effect on mobilization of energetic substrate. Both cortisol and gene expression of metabolic-related proteins and glucocorticoid- and mineralocorticoid receptors were modified after heat shock, but that the cortisol response to handling was reduced. The rise in temperature induced a dependent decrease in plasma osmolality while increasing branchial Na+/K+-ATPase activity, thus decreasing osmoregulatory efficiency. In conclusion, Antarctic fish are reactive to environmental change, but that their ability to accommodate rapid or adaptive responses may be compromised.

  10. Drake Passage-Antarctic Peninsula Ecosystem Research: Spring and Fall Zooplankton and Seabird Assemblages

    Science.gov (United States)

    Loeb, V. J.; Chereskin, T. K.; Santora, J. A.

    2016-02-01

    Acoustic Doppler Current Profiler (ADCP) records from multiple "L.M. Gould" supply transits of Drake Passage from 1999 to present demonstrate spatial and temporal (diel, seasonal, annual and longer term) variability in acoustics backscattering. Acoustics backscattering strength in the upper water column corresponds to zooplankton and nekton biomass that relates to seabird and mammal distribution and abundance. Recent results indicate that interannual variability in backscattering strength is correlated to climate indices. The interpretation of these ecological changes is severely limited because the sound scatterers previously had not been identified and linkages to upper trophic level predators are unknown. Net-tows, depth-referenced underwater videography and seabird/mammal visual surveys during spring 2014 and fall 2015 transits provided information on the taxonomic-size composition, distribution, aggregation and behavioral patterns of dominant ADCP backscattering organisms and relate these to higher level predator populations. The distribution and composition of zooplankton species and seabird assemblages conformed to four biogeographic regions. Areas of elevated secondary productivity coincided with increased ADCP target strength with highest concentrations off Patagonia and Antarctic Peninsula and secondary peaks around the Polar Front. Small sized zooplankton taxa dominated north of the Polar Front while larger taxa dominated to the south. Regionally important prey items likely are: copepods, amphipods, small euphausiids and fish (Patagonia); copepods, myctophids, shelled pteropods and squid (Polar Front); large euphausiids (Antarctic Peninsula). This study demonstrates that biological observations during "L.M. Gould" supply transits greatly augment the value of routinely collected ADCP and XBT data and provide basic information relevant to the impacts of climate change in this rapidly warming portion of the Southern Ocean

  11. Overview and Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992-2009

    Science.gov (United States)

    Zwally, H. Jay; Giovinetto, Mario B.

    2011-01-01

    Mass balance estimates for the Antarctic Ice Sheet (AIS) in the 2007 report by the Intergovernmental Panel on Climate Change and in more recent reports lie between approximately ?50 to -250 Gt/year for 1992 to 2009. The 300 Gt/year range is approximately 15% of the annual mass input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (?28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. We also modify the IOM estimate using (1) an alternate extrapolation to estimate the discharge from the non-observed 15% of the periphery, and (2) substitution of input from a field data compilation for input from an atmospheric model in 6% of area. The modified IOM estimate reduces the loss from 136 Gt/year to 13 Gt/year. Two ERS-based estimates, the modified IOM, and a GRACE-based estimate for observations within 1992 2005 lie in a narrowed range of ?27 to -40 Gt/year, which is about 3% of the annual mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992 2001 is -47 Gt/year for West Antarctica, ?16 Gt/year for East Antarctica, and -31 Gt/year overall (?0.1 mm/year SLE), not including part of the Antarctic Peninsula (1.07% of the AIS area). Although recent reports of large and increasing rates of mass loss with time from GRACE-based studies cite agreement with IOM results, our evaluation does not support that conclusion

  12. Expedition to the Antarctic Peninsula in the 2012-2013 campaign with participation of the CIEMAT; Expedicion a la Peninsula Antartica en la campana 2012-2013 con participacion del CIEMAT

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, T.; Lopez Martinez, J.; Duran Valsero, J. J.; O' Neill, T.

    2013-07-01

    Antarctica is the most remote, hostile and uninhabited continent on Earth. It is key to understand how our planet works and the impact we have on it. The Antarctic has many unique geological, glaciological and biological features. Its environment and its biological communities have a limited natural capacity for recovery from the alterations they undergo and therefore can be easily and irreversibly damaged. This is why the Antarctic Treaty and, in particular, the Protocol on Environmental Protection of the Antarctic Treaty (the Madrid Protocol) pay special attention to these matters. In this context, the effects of climate change and also the growing pressure of human activities, including scientific research and tourist visits, are reason for this attention. (Author)

  13. Progress on Antarctic Glacial Isostatic Adjustment and GRACE constraints on ice loss (Invited)

    Science.gov (United States)

    Ivins, E. R.; James, T. S.; Wahr, J. M.; Schrama, E. J.; Simon, K. M.; Landerer, F. W.; Watkins, M. M.; Wiese, D. N.

    2013-12-01

    Preparations for the Intergovermental Panel on Climate Change: Assessment Report 5 (IPCC AR5) has placed pressure on various research groups to accelerate the pace of their work in order to meet the Report deadlines. While this stimulates both positive and negative bi-products, it helped to focus attention to irreconcilable mass balance determinations for the Antarctic Ice Sheet (AIS) using space and airborne data. A glaring ';sore-thumb' for determining AIS trends from Gravity Recovery and Climate Experiment (GRACE) satellite data is the large signal of glacial isostatic adjustment (GIA) that is poorly constrained and possibly of the same magnitude as the present-day mass change. The report published in Science (vol. 338, pp. 1183-89) by S13 [Shepherd et al. 2013] met this challenge head-on by investing heavily in improving the GIA models with new GPS data, and new chronological constraints on ice sheet evolution across the Antarctic continent. This new data has emerged only within the last five years, and it came at a fortuitous time for advancing the IPCC AR5 goals. In this presentation we speak to the improvements developed in a recent JGR Solid Earth publication (14 June 2013). We extend the analysis using all of the official 05 releases of the analysis centers, including the JPL-mascon fields. The total error budgets of GIA correction are poorly determined, in spite of the great model improvements witnessed in the past 5 years. S12 reported the uncertainty for space-based sea level sourcing during 1992-2011 to Antarctica at roughly 0.23 mm/yr. Although GRACE 2002-2013 estimates vary, the uncertainly is about half this value. Here we examine how much of that uncertainty is still caused by GIA models and discuss how new classes of GIA models, and the collection of yet new GPS and ice constraint data for Antarctica, will enhance the value of a GRACE Follow-On mission. However, there will be a limit to constraining GIA, and a limit, therefore, to GIA error due to

  14. Time Series Based for Online Signature Verification

    Directory of Open Access Journals (Sweden)

    I Ketut Gede Darma Putra

    2013-11-01

    Full Text Available Signature verification system is to match the tested signature with a claimed signature. This paper proposes time series based for feature extraction method and dynamic time warping for match method. The system made by process of testing 900 signatures belong to 50 participants, 3 signatures for reference and 5 signatures from original user, simple imposters and trained imposters for signatures test. The final result system was tested with 50 participants with 3 references. This test obtained that system accuracy without imposters is 90,44897959% at threshold 44 with rejection errors (FNMR is 5,2% and acceptance errors (FMR is 4,35102%, when with imposters system accuracy is 80,1361% at threshold 27 with error rejection (FNMR is 15,6% and acceptance errors (average FMR is 4,263946%, with details as follows: acceptance errors is 0,391837%, acceptance errors simple imposters is 3,2% and acceptance errors trained imposters is 9,2%.

  15. Spectral signature selection for mapping unvegetated soils

    Science.gov (United States)

    May, G. A.; Petersen, G. W.

    1975-01-01

    Airborne multispectral scanner data covering the wavelength interval from 0.40-2.60 microns were collected at an altitude of 1000 m above the terrain in southeastern Pennsylvania. Uniform training areas were selected within three sites from this flightline. Soil samples were collected from each site and a procedure developed to allow assignment of scan line and element number from the multispectral scanner data to each sampling location. These soil samples were analyzed on a spectrophotometer and laboratory spectral signatures were derived. After correcting for solar radiation and atmospheric attenuation, the laboratory signatures were compared to the spectral signatures derived from these same soils using multispectral scanner data. Both signatures were used in supervised and unsupervised classification routines. Computer-generated maps using the laboratory and multispectral scanner derived signatures resulted in maps that were similar to maps resulting from field surveys. Approximately 90% agreement was obtained between classification maps produced using multispectral scanner derived signatures and laboratory derived signatures.

  16. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

    Directory of Open Access Journals (Sweden)

    R. S. Humphries

    2016-02-01

    Full Text Available Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3 concentrations exhibited a five-fold increase moving across the polar front, with mean polar cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between

  17. Asian Eocene monsoons as revealed by leaf architectural signatures

    Science.gov (United States)

    Spicer, Robert A.; Yang, Jian; Herman, Alexei B.; Kodrul, Tatiana; Maslova, Natalia; Spicer, Teresa E. V.; Aleksandrova, Galina; Jin, Jianhua

    2016-09-01

    The onset and development of the Asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations, coupled with a diversity of definitions and metrics characterizing monsoon phenomena, have generated much debate. Failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the Inter-tropical Convergence Zone (ITCZ) from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics. Here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils. Leaf form adapts to the prevailing climate, particularly under the extreme seasonal stresses imposed by monsoons, so it is likely that fossil leaves carry a unique signature of past monsoon regimes. Leaf form trait spectra obtained from fossils from Eocene basins in southern China were compared with those seen in modern leaves growing under known climate regimes. The fossil leaf trait spectra, including those derived from previously published fossil floras from northwestern India, were most similar to those found in vegetation exposed to the modern Indonesia-Australia Monsoon (I-AM), which is largely a product of seasonal migrations of the ITCZ. The presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in Eocene time across southern Asia the characteristics of the modern topographically-enhanced South Asia Monsoon had yet to develop. By the Eocene leaves in South Asia had become well adapted to an I-AM type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the Eocene. No fossil trait spectra typical of exposure to the modern East Asia monsoon were seen, suggesting the effects of this system in southern

  18. Temperature-dependent enthalpy of oxygenation in Antarctic fish hemoglobins

    DEFF Research Database (Denmark)

    Fago, A.; Wells, R.M.G.; Weber, Roy E.

    1997-01-01

    literature data for the enthalpy of oxygenation in Antarctic fish hemoglobins derives from the use of the nonintegrated (linearized) form of the van't Hoff equation over different temperature ranges. The general assumption that a low heat of oxygenation in hemoglobins from polar animals represents......The effect of temperature on the oxygen-binding properties of the hemoglobins of three cold-adapted Antarctic fish species, Dissostichus mawsoni, Pagothenia borchgrevinki and Trematomus, sp., has been investigated under different pH values and buffer conditions. A clear non linear van't Hoff plot...

  19. GLACIOCLIM-SAMBA: A Terre Adelie / Wilkes Land Antarctic surface mass balance observatory

    Science.gov (United States)

    Genthon, C.; Frezzotti, M.; Le Meur, E.; Magand, O.; Six, D.; Wagnon, P.

    2005-12-01

    While local measurements at hundreds of sites are now available (although sometimes questionable, e.g. Magand et al., this volume) to verify how large-scale models reproduce the spatial distribution of the surface mass balance (SMB) of Antarctica, few field observations yet make it possible to verify current intra- and inter-annual variability and trends of the SMB in the models, and to evaluate the processes that relate this variability with that of climate. It is a major aim of the GLACIOCLIM-SAMBA observatory (http://lgge.obs.ujf-grenoble.fr/~christo/glacioclim/samba/), initiated in 2004, to provide such observations in the Terre Adelie and Wilkes Land area. Recognizing that the largest absolute changes (and thus contribution to sea-level) of Antarctic SMB are expected where the current mean SMB is largest, that is in the coastal regions, SAMBA is largely focused on ice sheet margin. To sample spatial scales compatible with the scales resolved by models used to predict climate and SMB changes, a 150 km accumulation stakes line is being set up from the coast near the French Dumont d'Urville station, towards to Antarctic plateau in the general direction of the Italy/France Concordia station. Ground penetrating radar survey will provide snap-shot SMB interpolation along the stakes line. A blue ice stretch at the coast is being monitored by a 50-stake ablation network. Three 50-stakes networks are being set up near Concordia station to relate coastal and plateau SMB variability and change. An automatic weather station (AWS, including radiation) deployed at the coast, and the D-10, D-47 and DCII Antarctic Meteorological Research Center (http://amrc.ssec.wisc.edu/) AWSs, provide meteorological information to relate observed SMB and climate. Italian meteorology and radiation programs at Concordia, planned micrometeorology special campaigns at the margin, and precipitation monitoring at both sites, should help decipher the processes that relate SMB and climate

  20. Model bias for South Atlantic Antarctic intermediate water in CMIP5

    Science.gov (United States)

    Zhu, Chenyu; Liu, Zhengyu; Gu, Sifan

    2017-07-01

    Characterized by a salinity minimum in the mid-depth, the Antarctic Intermediate Water (AAIW) is an important component of global ocean water mass. The simulation of the AAIW in current climate models, however, has remained deficient, especially in the Atlantic sector. Here, we evaluate the simulation of the South Atlantic AAIW in eleven state-of-the-art coupled climate models. It is found that all the models show a common AAIW bias relative to the observation, with a saltier, warmer and lighter core located at a shallower depth. This AAIW bias seems to contribute to a deficient freshwater export by the Atlantic Meridional Overturning Circulation (AMOC), potentially overstabilizing the AMOC. The causes of the bias are investigated in sensitivity experiments using an ocean alone model. It is found that the AAIW bias is caused neither by the surface climate bias nor the North Atlantic bias, although is weakly affected by the inter-basin exchange. This left the conclusion that the AAIW bias is caused predominantly by the deficient model representation of ocean dynamics and mixing processes in the AAIW region.

  1. Aerial Photography Estimation of CH4 and N2O Emissions from Adelie Penguins During 1983-2012 in Victoria Land, Antarctic

    Science.gov (United States)

    He, H.; Li, X.; Cheng, X.

    2016-12-01

    Sea animals are the "bio-indicators" of the climate change in the Antarctic. The abundant nutrient components in their excreta such as carbon (C) and nitrogen (N) promote the emissions of greenhouse gases (GHGs) including methane (CH4) and nitrous oxide (N2O). Adélie Penguins are important sea animals, their colonies therefore become the potential "hotspots" of the GHGs emissions. Some field observations have been carried out to study the penguin excreta on CH4 and N2O emissions in the Antarctic peninsula. However, due to the lacking of the penguin population data, the total emissions of GHGs have not been estimated at regional scale. This study aimed to extract penguin information from two period aerial photographs respectively in 1983 and 2012 using object-oriented method in Victoria Land, Antarctic, and then estimate the Adélie penguin populations on Inexpressible Island combined with the shadow analysis. Meanwhile, a GHGs model was developed to estimate CH4 and N2O emissions from Adelie penguins based on the CH4 and N2O fluxes of penguin guanos, the number of penguins, and the fresh weight of penguin guanos and so on. The results indicated that object-oriented method was effective in penguin information extraction from high-resolution images, and there were 17120 and 21183 Adélie penguins respectively in 1983 and 2012, respectively. The main reasons for the increase in penguin populations from 1983 to 2012 might be explained from physical environment and biological environment, such as the rising temperatures and reduced Antarctic toothfishes. And the total CH4 and N2O emissions from penguins on Inexpressible Island during breeding season were 246 kg CH4 and 2.67 kg N2O in 1983, and 304 kg CH4 and 3.31 kg N2O in 2012. Our study aimed to provide important reference value for the estimation of GHG budget in Antarctic.

  2. What is happening in the International Polar Year? Latest news about the climate changes

    International Nuclear Information System (INIS)

    Orheim, Olav

    2008-01-01

    The International Polar (IPY) Year 2007-2008 is a large scientific programme focused on the Arctic and the Antarctic. Scientists from over 60 nations participates. The IPY have two primary objectives: to improve weather forecasts especially regarding extreme weather and to improve climatic models for better understanding of possible instabilities, especially regarding ocean currents. The presentation includes data on natural climate change, temperature anomaly, the ice in the Arctic Ocean and Northern and Southern Hemisphere sea ice area, current in Southern and Northern hemisphere sea ice area and variations of the surface temperature ice arctic regions antarctic regions. The presentation was held at the MNT-Forum, 29. January 2008

  3. Diagnostic Comparison of Meteorological Analyses during the 2002 Antarctic Winter

    Science.gov (United States)

    Manney, Gloria L.; Allen, Douglas R.; Kruger, Kirstin; Naujokat, Barbara; Santee, Michelle L.; Sabutis, Joseph L.; Pawson, Steven; Swinbank, Richard; Randall, Cora E.; Simmons, Adrian J.; hide

    2005-01-01

    Several meteorological datasets, including U.K. Met Office (MetO), European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP), and NASA's Goddard Earth Observation System (GEOS-4) analyses, are being used in studies of the 2002 Southern Hemisphere (SH) stratospheric winter and Antarctic major warming. Diagnostics are compared to assess how these studies may be affected by the meteorological data used. While the overall structure and evolution of temperatures, winds, and wave diagnostics in the different analyses provide a consistent picture of the large-scale dynamics of the SH 2002 winter, several significant differences may affect detailed studies. The NCEP-NCAR reanalysis (REAN) and NCEP-Department of Energy (DOE) reanalysis-2 (REAN-2) datasets are not recommended for detailed studies, especially those related to polar processing, because of lower-stratospheric temperature biases that result in underestimates of polar processing potential, and because their winds and wave diagnostics show increasing differences from other analyses between similar to 30 and 10 hPa (their top level). Southern Hemisphere polar stratospheric temperatures in the ECMWF 40-Yr Re-analysis (ERA-40) show unrealistic vertical structure, so this long-term reanalysis is also unsuited for quantitative studies. The NCEP/Climate Prediction Center (CPC) objective analyses give an inferior representation of the upper-stratospheric vortex. Polar vortex transport barriers are similar in all analyses, but there is large variation in the amount, patterns, and timing of mixing, even among the operational assimilated datasets (ECMWF, MetO, and GEOS-4). The higher-resolution GEOS-4 and ECMWF assimilations provide significantly better representation of filamentation and small-scale structure than the other analyses, even when fields gridded at reduced resolution are studied. The choice of which analysis to use is most critical for detailed transport

  4. Forecast of Antarctic Sea Ice and Meteorological Fields

    Science.gov (United States)

    Barreira, S.; Orquera, F.

    2017-12-01

    Since 2001, we have been forecasting the climatic fields of the Antarctic sea ice (SI) and surface air temperature, surface pressure and precipitation anomalies for the Southern Hemisphere at the Meteorological Department of the Argentine Naval Hydrographic Service with different techniques that have evolved with the years. Forecast is based on the results of Principal Components Analysis applied to SI series (S-Mode) that gives patterns of temporal series with validity areas (these series are important to determine which areas in Antarctica will have positive or negative SI anomalies based on what happen in the atmosphere) and, on the other hand, to SI fields (T-Mode) that give us the form of the SI fields anomalies based on a classification of 16 patterns. Each T-Mode pattern has unique atmospheric fields associated to them. Therefore, it is possible to forecast whichever atmosphere variable we decide for the Southern Hemisphere. When the forecast is obtained, each pattern has a probability of occurrence and sometimes it is necessary to compose more than one of them to obtain the final result. S-Mode and T-Mode are monthly updated with new data, for that reason the forecasts improved with the increase of cases since 2001. We used the Monthly Polar Gridded Sea Ice Concentrations database derived from satellite information generated by NASA Team algorithm provided monthly by the National Snow and Ice Data Center of USA that begins in November 1978. Recently, we have been experimenting with multilayer Perceptron (neuronal network) with supervised learning and a back-propagation algorithm to improve the forecast. The Perceptron is the most common Artificial Neural Network topology dedicated to image pattern recognition. It was implemented through the use of temperature and pressure anomalies field images that were associated with a the different sea ice anomaly patterns. The variables analyzed included only composites of surface air temperature and pressure anomalies

  5. {sup 137}Cs concentrations in Atlantic and western Antarctic surface waters: results of the 7th Ukrainian Antarctic Expedition, 2002

    Energy Technology Data Exchange (ETDEWEB)

    Gulin, S.B. [Institute of Biology of the Southern Seas (IBSS), 2, Nakhimov Av., Sevastopol, 99011 (Ukraine)]. E-mail: sergei@gulin.sebastopol.ua; Stokozov, N.A. [Institute of Biology of the Southern Seas (IBSS), 2, Nakhimov Av., Sevastopol, 99011 (Ukraine)

    2005-07-01

    The latitudinal distribution of {sup 137}Cs in the Atlantic-western Antarctic surface waters was studied during the 7th Ukrainian Antarctic Expedition in January-May 2002. The {sup 137}Cs concentrations have also been measured in the upper ice of the coastal glacier Woozle Hill located near the Ukrainian Antarctic station 'Akademik Vernadsky' (western Antarctica, 65 deg 15' S-64 deg 16' W). Comparison of these data with results of previous same-route expeditions SWEDARP (Swedish Antarctic Research Expedition, 1988/1989) and the French R/V 'Jeanne d'Arc' (1992/1993), has shown practically parallel changes of {sup 137}Cs surface concentrations between 40 deg N and 20 deg S, pointing to decrease of {sup 137}Cs radioactivity at these latitudes with an apparent half-life of 10-15 years (12.5{+-}2.1 years on average). This suggests that decrease of {sup 137}Cs surface concentration within this latitude band is controlled, besides the radioactive decay of {sup 137}Cs (half-life=30 years), by vertical mixing of the upper water masses. South of 20 deg S, the {sup 137}Cs concentrations in surface water have decreased more rapidly because of the influence of the less contaminated Antarctic waters. At 50-60 deg S and near the Antarctic coast, the {sup 137}Cs activity in 2002 was similar to those measured during the SWEDARP and 'Jeanne d'Arc' expeditions, suggesting an additional input of {sup 137}Cs to these waters from the melted ice from the adjacent glaciers.

  6. Infrared signatures for remote sensing

    Energy Technology Data Exchange (ETDEWEB)

    McDowell, R.S.; Sharpe, S.W.; Kelly, J.F.

    1994-04-01

    PNL`s capabilities for infrared and near-infrared spectroscopy include tunable-diode-laser (TDL) systems covering 300--3,000 cm{sup {minus}1} at <10-MHz bandwidth; a Bruker Fourier-transform infrared (FTIR) spectrometer for the near- to far-infrared at 50-MHz resolution; and a stable line-tunable, 12-w cw CO{sub 2} laser. PNL also has a beam expansion source with a 12-cm slit, which provides a 3-m effective path for gases at {approximately}10 K, giving a Doppler width of typically 10 MHz; and long-path static gas cells (to 100 m). In applying this equipment to signatures work, the authors emphasize the importance of high spectral resolution for detecting and identifying atmospheric interferences; for identifying the optimum analytical frequencies; for deriving, by spectroscopic analysis, the molecular parameters needed for modeling; and for obtaining data on species and/or bands that are not in existing databases. As an example of such spectroscopy, the authors have assigned and analyzed the C-Cl stretching region of CCl{sub 4} at 770--800 cm{sup {minus}1}. This is an important potential signature species whose IR absorption has remained puzzling because of the natural isotopic mix, extensive hot-band structure, and a Fermi resonance involving a nearby combination band. Instrument development projects include the IR sniffer, a small high-sensitivity, high-discrimination (Doppler-limited) device for fence-line or downwind monitoring that is effective even in regions of atmospheric absorption; preliminary work has achieved sensitivities at the low-ppb level. Other work covers trace species detection with TDLs, and FM-modulated CO{sub 2} laser LIDAR. The authors are planning a field experiment to interrogate the Hanford tank farm for signature species from Rattlesnake Mountain, a standoff of ca. 15 km, to be accompanied by simultaneous ground-truthing at the tanks.

  7. Diatom-induced silicon isotopic fractionation in Antarctic sea ice

    Science.gov (United States)

    Francois, F.; Damien, C.; Jean-Louis, T.; Anthony, W.; Luc, A.

    2006-12-01

    We measured silicon-isotopic composition of dissolved silicon and biogenic silica collected by sequential melting from spring 2003 Antarctic pack ice (Australian sector). Sea ice is a key ecosystem in the Southern Ocean and its melting in spring has been often thought to have a seeding effect for the surface waters, triggering blooms in the mixed layer. This work is the first investigation of the silicon isotopes' proxy in sea ice and allows to estimate the activity of sea-ice diatoms in the different brine structures and the influence of sea- ice diatoms on the spring ice edge blooms. The relative use of the dissolved silicon pool by sea-ice diatoms is usually assessed by calculating nutrient:salinity ratios in the brines. However such an approach is biased by difficulties in evaluating the initial nutrient concentrations in the different brines structures, and by the impossibility to account for late sporadic nutrient replenishments. The silicon-isotopic composition of biogenic silica is a convenient alternative since it integrates an average Si utilization on all generations of diatoms. Measurements were performed on a MC-ICP-MS, in dry plasma mode using external Mg doping. Results are expressed as delta29Si relative to the NBS28 standard. From three sea ice cores with contrasted physico-chemical characteristics, we report significant isotopic fractionations linked to the diatoms activity, with distinct silicon biogeochemical dynamics between different brine structure. The diatoms in snow ice and in brine pockets of frazil or congelation ice have the most positive silicon-isotopic composition (+0.53 to +0.86 p.mil), indicating that they grow in a closed system and use a significant part of the small dissolved silicon pool. In the brine channels and skeletal layer, diatoms display a relatively less positive Si-isotopic composition (+0.41 to +0.70 p.mil), although it is still heavier compared to equilibrium fractionation (+0.38 p.mil). This suggests that they have

  8. Metabolic signatures of bacterial vaginosis.

    Science.gov (United States)

    Srinivasan, Sujatha; Morgan, Martin T; Fiedler, Tina L; Djukovic, Danijel; Hoffman, Noah G; Raftery, Daniel; Marrazzo, Jeanne M; Fredricks, David N

    2015-04-14

    Bacterial vaginosis (BV) is characterized by shifts in the vaginal microbiota from Lactobacillus dominant to a microbiota with diverse anaerobic bacteria. Few studies have linked specific metabolites with bacteria found in the human vagina. Here, we report dramatic differences in metabolite compositions and concentrations associated with BV using a global metabolomics approach. We further validated important metabolites using samples from a second cohort of women and a different platform to measure metabolites. In the primary study, we compared metabolite profiles in cervicovaginal lavage fluid from 40 women with BV and 20 women without BV. Vaginal bacterial representation was determined using broad-range PCR with pyrosequencing and concentrations of bacteria by quantitative PCR. We detected 279 named biochemicals; levels of 62% of metabolites were significantly different in women with BV. Unsupervised clustering of metabolites separated women with and without BV. Women with BV have metabolite profiles marked by lower concentrations of amino acids and dipeptides, concomitant with higher levels of amino acid catabolites and polyamines. Higher levels of the signaling eicosanoid 12-hydroxyeicosatetraenoic acid (12-HETE), a biomarker for inflammation, were noted in BV. Lactobacillus crispatus and Lactobacillus jensenii exhibited similar metabolite correlation patterns, which were distinct from correlation patterns exhibited by BV-associated bacteria. Several metabolites were significantly associated with clinical signs and symptoms (Amsel criteria) used to diagnose BV, and no metabolite was associated with all four clinical criteria. BV has strong metabolic signatures across multiple metabolic pathways, and these signatures are associated with the presence and concentrations of particular bacteria. Bacterial vaginosis (BV) is a common but highly enigmatic condition that is associated with adverse outcomes for women and their neonates. Small molecule metabolites in the

  9. Antarctic and Greenland ice sheet mass balance products from satellite gravimetry

    Science.gov (United States)

    Horwath, Martin; Groh, Andreas; Horvath, Alexander; Forsberg, René; Meister, Rakia; Barletta, Valentina R.; Shepherd, Andrew

    2017-04-01

    Because of their important role in the Earth's climate system, ESA's Climate Change Initiative (CCI) has identified both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS) as Essential Climate Variables (ECV). Since respondents of a user survey indicated that the ice sheet mass balance is one of the most important ECV data products needed to better understand climate change, the AIS_cci and the GIS_cci project provide Gravimetric Mass Balance (GMB) products based on satellite gravimetry data. The GMB products are derived from GRACE (Gravity Recovery and Climate Experiment) monthly solutions of release ITSG-Grace2016 produced at TU Graz. GMB basin products (i.e. time series of monthly mass changes for the entire ice sheets and selected drainage basins) and GMB gridded products (e.g. mass balance estimates with a formal resolution of about 50km, covering the entire ice sheets) are generated for the period from 2002 until present. The first GMB product was released in mid 2016. Here we present an extended and updated version of the ESA CCI GMB products, which are freely available through data portals hosted by the projects (https://data1.geo.tu-dresden.de/ais_gmb, http://products.esa-icesheets-cci.org/products/downloadlist/GMB). Since the initial product release, the applied processing strategies have been improved in order to further reduce GRACE errors and to enhance the separation of signals super-imposed to the ice mass changes. While a regional integration approach is used by the AIS_cci project, the GMB products of the GIS_cci project are derived using a point mass inversion. The differences between both approaches are investigated through the example of the GIS, where an alternative GMB product was generated using the regional integration approach implemented by the AIS_cci. Finally, we present the latest mass balance estimates for both ice sheets as well as their corresponding contributions to global sea level rise.

  10. Greenlandic Inuit show genetic signatures of diet and climate adaptation

    DEFF Research Database (Denmark)

    Fumagalli, Matteo; Moltke, Ida; Grarup, Niels

    2015-01-01

    The indigenous people of Greenland, the Inuit, have lived for a long time in the extreme conditions of the Arctic, including low annual temperatures, and with a specialized diet rich in protein and fatty acids, particularly omega-3 polyunsaturated fatty acids (PUFAs). A scan of Inuit genomes......, with the effect on height replicated in Europeans. By analyzing membrane lipids, we found that the selected alleles modulate fatty acid composition, which may affect the regulation of growth hormones. Thus, the Inuit have genetic and physiological adaptations to a diet rich in PUFAs....

  11. Impacts of Atmosphere-Ocean Coupling on Southern Hemisphere Climate Change

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven

    2013-01-01

    Climate in the Southern Hemisphere (SH) has undergone significant changes in recent decades. These changes are closely linked to the shift of the Southern Annular Mode (SAM) towards its positive polarity, which is driven primarily by Antarctic ozone depletion. There is growing evidence that Antarctic ozone depletion has significant impacts on Southern Ocean circulation change. However, it is poorly understood whether and how ocean feedback might impact the SAM and climate change in the SH atmosphere. This outstanding science question is investigated using the Goddard Earth Observing System Coupled Atmosphere-Ocean-Chemistry Climate Model(GEOS-AOCCM).We perform ensemble simulations of the recent past (1960-2010) with and without the interactive ocean. For simulations without the interactive ocean, we use sea surface temperatures and sea ice concentrations produced by the interactive ocean simulations. The differences between these two ensemble simulations quantify the effects of atmosphere-ocean coupling. We will investigate the impacts of atmosphere-ocean coupling on stratospheric processes such as Antarctic ozone depletion and Antarctic polar vortex breakup. We will address whether ocean feedback affects Rossby wave generation in the troposphere and wave propagation into the stratosphere. Another focuson this study is to assess how ocean feedback might affect the tropospheric SAM response to Antarctic ozone depletion

  12. Climatological implications of Australian-Antarctic separation

    NARCIS (Netherlands)

    Warnaar, J.

    2006-01-01

    We face a major challenge in learning how to quantify the impact of the anticipated global warming before it occurs. It is widely recognized that the application of coupled ocean-atmosphere global circulation models (GCMs) offers a sophisticated method of predicting climate. However, while GCMs

  13. Parameter Estimations of Dynamic Energy Budget (DEB) Model over the Life History of a Key Antarctic Species: The Antarctic Sea Star Odontaster validus Koehler, 1906.

    Science.gov (United States)

    Agüera, Antonio; Collard, Marie; Jossart, Quentin; Moreau, Camille; Danis, Bruno

    2015-01-01

    Marine organisms in Antarctica are adapted to an extreme ecosystem including extremely stable temperatures and strong seasonality due to changes in day length. It is now largely accepted that Southern Ocean organisms are particularly vulnerable to global warming with some regions already being challenged by a rapid increase of temperature. Climate change affects both the physical and biotic components of marine ecosystems and will have an impact on the distribution and population dynamics of Antarctic marine organisms. To predict and assess the effect of climate change on marine ecosystems a more comprehensive knowledge of the life history and physiology of key species is urgently needed. In this study we estimate the Dynamic Energy Budget (DEB) model parameters for key benthic Antarctic species the sea star Odontaster validus using available information from literature and experiments. The DEB theory is unique in capturing the metabolic processes of an organism through its entire life cycle as a function of temperature and food availability. The DEB model allows for the inclusion of the different life history stages, and thus, becomes a tool that can be used to model lifetime feeding, growth, reproduction, and their responses to changes in biotic and abiotic conditions. The DEB model presented here includes the estimation of reproduction handling rules for the development of simultaneous oocyte cohorts within the gonad. Additionally it links the DEB model reserves to the pyloric caeca an organ whose function has long been ascribed to energy storage. Model parameters described a slowed down metabolism of long living animals that mature slowly. O. validus has a large reserve that-matching low maintenance costs- allow withstanding long periods of starvation. Gonad development is continuous and individual cohorts developed within the gonads grow in biomass following a power function of the age of the cohort. The DEB model developed here for O. validus allowed us to

  14. Parameter Estimations of Dynamic Energy Budget (DEB Model over the Life History of a Key Antarctic Species: The Antarctic Sea Star Odontaster validus Koehler, 1906.

    Directory of Open Access Journals (Sweden)

    Antonio Agüera

    Full Text Available Marine organisms in Antarctica are adapted to an extreme ecosystem including extremely stable temperatures and strong seasonality due to changes in day length. It is now largely accepted that Southern Ocean organisms are particularly vulnerable to global warming with some regions already being challenged by a rapid increase of temperature. Climate change affects both the physical and biotic components of marine ecosystems and will have an impact on the distribution and population dynamics of Antarctic marine organisms. To predict and assess the effect of climate change on marine ecosystems a more comprehensive knowledge of the life history and physiology of key species is urgently needed. In this study we estimate the Dynamic Energy Budget (DEB model parameters for key benthic Antarctic species the sea star Odontaster validus using available information from literature and experiments. The DEB theory is unique in capturing the metabolic processes of an organism through its entire life cycle as a function of temperature and food availability. The DEB model allows for the inclusion of the different life history stages, and thus, becomes a tool that can be used to model lifetime feeding, growth, reproduction, and their responses to changes in biotic and abiotic conditions. The DEB model presented here includes the estimation of reproduction handling rules for the development of simultaneous oocyte cohorts within the gonad. Additionally it links the DEB model reserves to the pyloric caeca an organ whose function has long been ascribed to energy storage. Model parameters described a slowed down metabolism of long living animals that mature slowly. O. validus has a large reserve that-matching low maintenance costs- allow withstanding long periods of starvation. Gonad development is continuous and individual cohorts developed within the gonads grow in biomass following a power function of the age of the cohort. The DEB model developed here for O

  15. Emplacement of Antarctic ice sheet mass affects circumpolar ocean flow

    NARCIS (Netherlands)

    Rugenstein, Maria; Stocchi, Paolo; von der Heydt, Anna; Dijkstra, Hendrik; Brinkhuis, Henk

    2014-01-01

    During the Cenozoic the Antarctic continent experienced large fluctuations in ice-sheet volume. We investigate the effects of Glacial Isostatic Adjustment (GIA) on Southern Ocean circulation for the first continental scale glaciation of Antarctica (~34 Myr) by combining solid Earth and ocean dynamic

  16. Metagenomic analysis of a Southern Maritime Antarctic soil

    Directory of Open Access Journals (Sweden)

    David Anthony Pearce

    2012-12-01

    Full Text Available Our current understanding of Antarctic soils is derived from direct culture on selective media, biodiversity studies based on clone library construction and analysis, quantitative PCR amplification of specific gene sequences and the application of generic microarrays for microbial community analysis. Here, we investigated the biodiversity and functional potential of a soil community at Mars Oasis on Alexander Island in the southern Maritime Antarctic, by applying 454 pyrosequencing technology to a metagenomic library constructed from soil genomic DNA. The results suggest that the commonly cited range of phylotypes used in clone library construction and analysis of 78-730 OTUs (de-replicated to 30-140 provides low coverage of the major groups present (~5%. The vast majority of functional genes (>77% were for structure, carbohydrate metabolism and DNA/RNA processing and modification. This study suggests that prokaryotic diversity in Antarctic terrestrial environments appears to be limited at the generic level, with Proteobacteria, Actinobacteria being common. Cyanobacteria were surprisingly under-represented at 2.6% of sequences, although ~1% of the genes identified were involved in CO2 fixation. At the sequence level there appeared to be much greater heterogeneity, and this might be due to high divergence within the relatively restricted lineages which have successfully colonized Antarctic terrestrial environments.

  17. During the British Antarctic Survey's Offshore Biological Programme ...

    African Journals Online (AJOL)

    spamer

    bearing distal portion. The. Antarctic material has tentacular club suckers which possess, on the distal half of the ring, a prominent central recurved median tooth flanked by two triangular teeth on each side. The proximal half of the ring is smooth.

  18. 77 FR 5403 - Conservation of Antarctic Animals and Plants

    Science.gov (United States)

    2012-02-03

    ... NATIONAL SCIENCE FOUNDATION 45 CFR Part 670 Conservation of Antarctic Animals and Plants AGENCY... practice and procedure, Antarctica, Exports, Imports, Plants, Reporting and recordkeeping requirements... Plaque Commemorating the PM-3A Nuclear Power Plant at McMurdo Station. HSM 86 No.1 Building Commemorating...

  19. Genetics differentiation between Arctic and Antarctic monothalamous foraminiferans

    DEFF Research Database (Denmark)

    Pawlowski, Jan; Majewski, Wojciech; Longet, David

    2008-01-01

    distinct genetically. As expected, Arctic specimens were usually more closely related to those from Northern Europe than to their Antarctic representatives. The deep-sea specimens from Weddell Sea branched as a sister to the McMurdo Sound population, while those from the Arctic Ocean clustered with ones...

  20. Distribution of dissolved and particulate metals in Antarctic sea ice

    NARCIS (Netherlands)

    Lannuzel, D.; Bowie, A.R.; van der Merwe, P.C.; Townsend, A.T.; Schoemann, V.

    2011-01-01

    Samples were collected in East Antarctic sea ice in late winter/early austral spring 2007 to assess the distributions of Al, Cr, Mn, Cu, Zn, Mo. Cd and Ba. Total dissolved (<02 mu m) and particulate (>0.2 mu m) concentrations were measured by Inductively Coupled Plasma-Sector Field Mass Spectrometry

  1. Estimates of numbers of kelp gulls and Kerguelen and Antarctic ...

    African Journals Online (AJOL)

    Four species are regular breeders at the islands: Subantarctic skua Catharacta antarctica, kelp gull Larus dominicanus, Antarctic tern Sterna vittata and Kerguelen tern S. virgata. The latter three species currently each have populations of below 150 breeding pairs at the islands. Kelp gull numbers appear to be relatively ...

  2. Present and future variations in Antarctic firn air content

    NARCIS (Netherlands)

    Ligtenberg, S. R M; Kuipers Munneke, P.; Van Den Broeke, M. R.

    2014-01-01

    A firn densification model (FDM) is used to assess spatial and temporal (1979-2200) variations in the depth, density and temperature of the firn layer covering the Antarctic ice sheet (AIS). A time-dependent version of the FDM is compared to more commonly used steady-state FDM results. Although the

  3. South African Antarctic research programme 1978-1982

    CSIR Research Space (South Africa)

    SASCAR

    1978-12-01

    Full Text Available This document provides a comprehensive review of the planned South African scientific activities in Antarctica and on the sub-Antarctic islands in the five year period starting in 1978. The scientific programmes are classified under five headings...

  4. Petrology of Antarctic Eucrites PCA 91078 and PCA 91245

    Science.gov (United States)

    Howard, L. M.; Domanik, K. J.; Drake, M. J.; Mittlefehldt, D. W.

    2002-01-01

    Antarctic eucrites PCA 91078 and PCA 91245, are petrographically characterized and found to be unpaired, type 6, basaltic eucrites. Observed textures that provide insight into the petrogenesis of these meteorites are also discussed. Additional information is contained in the original extended abstract.

  5. Molecular evolution of hemoglobins of Antarctic fishes (Notothenioidei)

    NARCIS (Netherlands)

    Stam, W.T.; Beintema, J.J; D Avino, R.; Tamburrini, M.; di Prisco, G.

    1997-01-01

    Amino acid sequences of alpha- and beta-chains of human hemoglobin and of hemoglobins of coelacanth and 24 teleost fish species, including 11 antarctic and two temperate Notothenioidei, were analyzed using maximum parsimony. Trees were derived for the alpha- and beta-chains separately and for

  6. Maneuver simulation model of an experimental hovercraft for the Antarctic

    Science.gov (United States)

    Murao, Rinichi

    Results of an investigation of a hovercraft model designed for Antarctic conditions are presented. The buoyancy characteristics, the propellant control system, and simulation model control are examined. An ACV (air cushion vehicle) model of the hovercraft is used to examine the flexibility and friction of the skirt. Simulation results are presented which show the performance of the hovercraft.

  7. Is vertical migration in Antarctic krill (Euphausia superba) influenced ...

    Indian Academy of Sciences (India)

    Antarctic krill (Euphausia superba) is a keystone species in the southern ocean ecosystem where it is the main consumer of phytoplankton and constitutes the main food item of many higher predators. Both food and predators are most abundant at the surface, thus krill hide in the depth of the ocean during the day and ...

  8. Emplacement of Antarctic ice sheet mass affects circumpolar ocean flow

    NARCIS (Netherlands)

    Rugenstein, M.; Stocchi, P.; van der Heydt, A.; Brinkhuis, H.

    2014-01-01

    During the Cenozoic the Antarctic continent experienced large fluctuations in ice-sheet volume. We investigate the effects of Glacial Isostatic Adjustment (GIA) on Southern Ocean circulation for the first continental scale glaciation of Antarctica (~ 34 Myr) by combining solid Earth and ocean

  9. Microbial ecology and biogeochemistry of continental Antarctic soils

    Directory of Open Access Journals (Sweden)

    Don A Cowan

    2014-04-01

    Full Text Available The Antarctica Dry Valleys are regarded as the coldest hyperarid desert system on Earth. While a wide variety of environmental stressors including very low minimum temperatures, frequent freeze-thaw cycles and low water availability impose severe limitations to life, suitable niches for abundant microbial colonization exist. Antarctic desert soils contain much higher levels of microbial diversity than previously thought. Edaphic niches, including cryptic and refuge habitats, microbial mats and permafrost soils all harbour microbial communities which drive key biogeochemical cycling processes. For example, lithobionts (hypoliths and endoliths possess a genetic capacity for nitrogen and carbon cycling, polymer degradation and other system processes. Nitrogen fixation rates of hypoliths, as assessed through acetylene reduction assays, suggest that these communities are a significant input source for nitrogen into these oligotrophic soils. Here we review aspects of microbial diversity in Antarctic soils with an emphasis on functionality and capacity. We assess current knowledge regarding adaptations to Antarctic soil environments and highlight the current threats to Antarctic desert soil communities.

  10. Modeling the Thermal Interactions of Meteorites Below the Antarctic Ice

    Science.gov (United States)

    Oldroyd, William Jared; Radebaugh, Jani; Stephens, Denise C.; Lorenz, Ralph; Harvey, Ralph; Karner, James

    2017-10-01

    Meteorites with high specific gravities, such as irons, appear to be underrepresented in Antarctic collections over the last 40 years. This underrepresentation is in comparison with observed meteorite falls, which are believed to represent the actual population of meteorites striking Earth. Meteorites on the Antarctic ice sheet absorb solar flux, possibly leading to downward tunneling into the ice, though observations of this in action are very limited. This descent is counteracted by ice sheet flow supporting the meteorites coupled with ablation near mountain margins, which helps to force meteorites towards the surface. Meteorites that both absorb adequate thermal energy and are sufficiently dense may instead reach a shallow equilibrium depth as downward melting overcomes upward forces during the Antarctic summer. Using a pyronometer, we have measured the incoming solar flux at multiple depths in two deep field sites in Antarctica, the Miller Range and Elephant Moraine. We compare these data with laboratory analogues and model the thermal and physical interactions between a variety of meteorites and their surroundings. Our Matlab code model will account for a wide range of parameters used to characterize meteorites in an Antarctic environment. We will present the results of our model along with depth estimates for several types of meteorites. The recovery of an additional population of heavy meteorites would increase our knowledge of the formation and composition of the solar system.

  11. Sector of West Antarctic Ice Sheet in "Irreversible Retreat"

    Science.gov (United States)

    Showstack, Randy

    2014-05-01

    A large sector of the West Antarctic Ice Sheet "has gone into a state of irreversible retreat," according to glaciologist Eric Rignot, lead author of the paper "Widespread rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler Glaciers in West Antarctica from 1992 to 2011," which has been accepted for publication in Geophysical Research Letters (GRL).

  12. Calving fluxes and basal melt rates of Antarctic ice shelves

    NARCIS (Netherlands)

    Depoorter, M.A.; Bamber, J.L.; Griggs, J.A.; Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; Ligtenberg, S.R.M.|info:eu-repo/dai/nl/32821177X; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Moholdt, G.

    2013-01-01

    Iceberg calving has been assumed to be the dominant cause of mass loss for the Antarctic ice sheet, with previous estimates of the calving flux exceeding 2,000 gigatonnes per year1, 2. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near

  13. Dynamic thinning of glaciers on the Southern Antarctic Peninsula

    NARCIS (Netherlands)

    Wouters, B.; Martin-Espanol, A.; Helm, V.; Flament, T.; van Wessem, J. M.; Ligtenberg, S. R. M.; van den Broeke, M. R.; Bamber, J. L.

    2015-01-01

    Growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice, especially if it is resting on bedrock below sea level. Much of the Southern Antarctic Peninsula satisfies this condition and also possesses a bed slope that deepens inland. Such ice sheet geometry

  14. Mucilaginibacter terrae sp nov., isolated from Antarctic soil

    Czech Academy of Sciences Publication Activity Database

    Sedláček, I.; Pantůček, R.; Králová, S.; Mašlaňová, I.; Holochová, P.; Staňková, E.; Sobotka, Roman; Barták, M.; Busse, H.-J.; Švec, P.

    2017-01-01

    Roč. 67, č. 10 (2017), s. 4002-4007 ISSN 1466-5026 R&D Projects: GA MŠk(CZ) LO1416 Institutional support: RVO:61388971 Keywords : Mucilaginibacter terrae sp nov. * James ross island * Antarctic Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 2.134, year: 2016

  15. Holocene subsurface temperature variability in the eastern Antarctic continental margin

    NARCIS (Netherlands)

    Kim, J.H.; Crosta, X.; Willmott, V.; Renssen, H.; Bonnin, J.; Helmke, P.; Schouten, S.; Sinninghe Damsté, J.S.

    2012-01-01

    We reconstructed subsurface (similar to 45-200 m water depth) temperature variability in the eastern Antarctic continental margin during the late Holocene, using an archaeal lipid-based temperature proxy (TEX86 L). Our results reveal that subsurface temperature changes were probably positively

  16. UV radiation and primary production in the Antarctic waters

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.; Krishnakumari, L.; Bhattathiri, P.M.A.; Chandramohan, D.

    of depth from 21/1/94 to 6/3/94. Fifteen stations in the Antarctic waters (69 degrees 53 minutes to 70 degrees 02 second S) and 6 en route (64 degrees 53 minutes 30 degrees 01 minutes S) were analysed. The average values for surface chlorophyll a and pp...

  17. Freshwater invertebrates of sub-Antarctic Marion Island | Dartnall ...

    African Journals Online (AJOL)

    Antarctic Marion Island were examined for invertebrates. Sixty-eight species were found, including 45 new records for the Island. Of these 56 were bona fide aquatic invertebrates, the rest being terrestrial or brackish interlopers that had fallen or been ...

  18. Theoretical Characterizaiton of Visual Signatures

    Science.gov (United States)

    Kashinski, D. O.; Chase, G. M.; di Nallo, O. E.; Scales, A. N.; Vanderley, D. L.; Byrd, E. F. C.

    2015-05-01

    We are investigating the accuracy of theoretical models used to predict the visible, ultraviolet, and infrared spectra, as well as other properties, of product materials ejected from the muzzle of currently fielded systems. Recent advances in solid propellants has made the management of muzzle signature (flash) a principle issue in weapons development across the calibers. A priori prediction of the electromagnetic spectra of formulations will allow researchers to tailor blends that yield desired signatures and determine spectrographic detection ranges. Quantum chemistry methods at various levels of sophistication have been employed to optimize molecular geometries, compute unscaled vibrational frequencies, and determine the optical spectra of specific gas-phase species. Electronic excitations are being computed using Time Dependent Density Functional Theory (TD-DFT). A full statistical analysis and reliability assessment of computational results is currently underway. A comparison of theoretical results to experimental values found in the literature is used to assess any affects of functional choice and basis set on calculation accuracy. The status of this work will be presented at the conference. Work supported by the ARL, DoD HPCMP, and USMA.

  19. Is there a distinct continental slope fauna in the Antarctic?

    Science.gov (United States)

    Kaiser, Stefanie; Griffiths, Huw J.; Barnes, David K. A.; Brandão, Simone N.; Brandt, Angelika; O'Brien, Philip E.

    2011-02-01

    The Antarctic continental slope spans the depths from the shelf break (usually between 500 and 1000 m) to ˜3000 m, is very steep, overlain by 'warm' (2-2.5 °C) Circumpolar Deep Water (CDW), and life there is poorly studied. This study investigates whether life on Antarctica's continental slope is essentially an extension of the shelf or the abyssal fauna, a transition zone between these or clearly distinct in its own right. Using data from several cruises to the Weddell Sea and Scotia Sea, including the ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) I-III, BIOPEARL (BIOdiversity, Phylogeny, Evolution and Adaptive Radiation of Life in Antarctica) 1 and EASIZ (Ecology of the Antarctic Sea Ice Zone) II cruises as well as current databases (SOMBASE, SCAR-MarBIN), four different taxa were selected (i.e. cheilostome bryozoans, isopod and ostracod crustaceans and echinoid echinoderms) and two areas, the Weddell Sea and the Scotia Sea, to examine faunal composition, richness and affinities. The answer has important ramifications to the link between physical oceanography and ecology, and the potential of the slope to act as a refuge and resupply zone to the shelf during glaciations. Benthic samples were collected using Agassiz trawl, epibenthic sledge and Rauschert sled. By bathymetric definition, these data suggest that despite eurybathy in some of the groups examined and apparent similarity of physical conditions in the Antarctic, the shelf, slope and abyssal faunas were clearly separated in the Weddell Sea. However, no such separation of faunas was apparent in the Scotia Sea (except in echinoids). Using a geomorphological definition of the slope, shelf-slope-abyss similarity only changed significantly in the bryozoans. Our results did not support the presence of a homogenous and unique Antarctic slope fauna despite a high number of species being restricted to the slope. However, it remains the case that there may be

  20. On the origin and evolution of Antarctic Peracarida (Crustacea, Malacostraca

    Directory of Open Access Journals (Sweden)

    Angelika Brandt

    1999-12-01

    Full Text Available The early separation of Gondwana and the subsequent isolation of Antarctica caused a long evolutionary history of its fauna. Both, long environmental stability over millions of years and habitat heterogeneity, due to an abundance of sessile suspension feeders on the continental shelf, favoured evolutionary processes of preadapted taxa, like for example the Peracarida. This taxon performs brood protection and this might be one of the most important reasons why it is very successful (i.e. abundant and diverse in most terrestrial and aquatic environments, with some species even occupying deserts. The extinction of many decapod crustaceans in the Cenozoic might have allowed the Peracarida to find and use free ecological niches. Therefore the palaeogeographic, palaeoclimatologic, and palaeo-hydrographic changes since the Palaeocene (at least since about 60 Ma ago and the evolutionary success of some peracarid taxa (e.g. Amphipoda, Isopoda led to the evolution of many endemic species in the Antarctic. Based on a phylogenetic analysis of the Antarctic Tanaidacea, Sieg (1988 demonstrated that the tanaid fauna of the Antarctic is mainly represented by phylogenetically younger taxa, and data from other crustacean taxa led Sieg (1988 to conclude that the recent Antarctic crustacean fauna must be comparatively young. His arguments are scrutinized on the basis of more recent data on the phylogeny and biodiversity of crustacean taxa, namely the Ostracoda, Decapoda, Mysidacea, Cumacea, Amphipoda, and Isopoda. This analysis demonstrates that the origin of the Antarctic fauna probably has different roots: an adaptive radiation of descendants from old Gondwanian ancestors was hypothesized for the isopod families Serolidae and Arcturidae, an evolution and radiation of phylogenetically old taxa in Antarctica could also be shown for the Ostracoda and the amphipod family Iphimediidae. A recolonization via the Scotia Arc appears possible for some species, though it is

  1. Intrusion signature creation via clustering anomalies

    Science.gov (United States)

    Hendry, Gilbert R.; Yang, Shanchieh J.

    2008-03-01

    Current practices for combating cyber attacks typically use Intrusion Detection Systems (IDSs) to detect and block multistage attacks. Because of the speed and impacts of new types of cyber attacks, current IDSs are limited in providing accurate detection while reliably adapting to new attacks. In signature-based IDS systems, this limitation is made apparent by the latency from day zero of an attack to the creation of an appropriate signature. This work hypothesizes that this latency can be shortened by creating signatures via anomaly-based algorithms. A hybrid supervised and unsupervised clustering algorithm is proposed for new signature creation. These new signatures created in real-time would take effect immediately, ideally detecting new attacks. This work first investigates a modified density-based clustering algorithm as an IDS, with its strengths and weaknesses identified. A signature creation algorithm leveraging the summarizing abilities of clustering is investigated. Lessons learned from the supervised signature creation are then leveraged for the development of unsupervised real-time signature classification. Automating signature creation and classification via clustering is demonstrated as satisfactory but with limitations.

  2. Institute of Geophysics, Planetary Physics, and Signatures

    Data.gov (United States)

    Federal Laboratory Consortium — The Institute of Geophysics, Planetary Physics, and Signatures at Los Alamos National Laboratory is committed to promoting and supporting high quality, cutting-edge...

  3. On reliable discovery of molecular signatures

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    Björkegren Johan

    2009-01-01

    Full Text Available Abstract Background Molecular signatures are sets of genes, proteins, genetic variants or other variables that can be used as markers for a particular phenotype. Reliable signature discovery methods could yield valuable insight into cell biology and mechanisms of human disease. However, it is currently not clear how to control error rates such as the false discovery rate (FDR in signature discovery. Moreover, signatures for cancer gene expression have been shown to be unstable, that is, difficult to replicate in independent studies, casting doubts on their reliability. Results We demonstrate that with modern prediction methods, signatures that yield accurate predictions may still have a high FDR. Further, we show that even signatures with low FDR may fail to replicate in independent studies due to limited statistical power. Thus, neither stability nor predictive accuracy are relevant when FDR control is the primary goal. We therefore develop a general statistical hypothesis testing framework that for the first time provides FDR control for signature discovery. Our method is demonstrated to be correct in simulation studies. When applied to five cancer data sets, the method was able to discover molecular signatures with 5% FDR in three cases, while two data sets yielded no significant findings. Conclusion Our approach enables reliable discovery of molecular signatures from genome-wide data with current sample sizes. The statistical framework developed herein is potentially applicable to a wide range of prediction problems in bioinformatics.

  4. An Arbitrated Quantum Signature Scheme without Entanglement"*

    International Nuclear Information System (INIS)

    Li Hui-Ran; Luo Ming-Xing; Peng Dai-Yuan; Wang Xiao-Jun

    2017-01-01

    Several quantum signature schemes are recently proposed to realize secure signatures of quantum or classical messages. Arbitrated quantum signature as one nontrivial scheme has attracted great interests because of its usefulness and efficiency. Unfortunately, previous schemes cannot against Trojan horse attack and DoS attack and lack of the unforgeability and the non-repudiation. In this paper, we propose an improved arbitrated quantum signature to address these secure issues with the honesty arbitrator. Our scheme takes use of qubit states not entanglements. More importantly, the qubit scheme can achieve the unforgeability and the non-repudiation. Our scheme is also secure for other known quantum attacks . (paper)

  5. An Arbitrated Quantum Signature Scheme without Entanglement*

    Science.gov (United States)

    Li, Hui-Ran; Luo, Ming-Xing; Peng, Dai-Yuan; Wang, Xiao-Jun

    2017-09-01

    Several quantum signature schemes are recently proposed to realize secure signatures of quantum or classical messages. Arbitrated quantum signature as one nontrivial scheme has attracted great interests because of its usefulness and efficiency. Unfortunately, previous schemes cannot against Trojan horse attack and DoS attack and lack of the unforgeability and the non-repudiation. In this paper, we propose an improved arbitrated quantum signature to address these secure issues with the honesty arbitrator. Our scheme takes use of qubit states not entanglements. More importantly, the qubit scheme can achieve the unforgeability and the non-repudiation. Our scheme is also secure for other known quantum attacks.

  6. Regional Antarctic snow accumulation over the past 1000 years

    Science.gov (United States)

    Thomas, Elizabeth R.; Melchior van Wessem, J.; Roberts, Jason; Isaksson, Elisabeth; Schlosser, Elisabeth; Fudge, Tyler J.; Vallelonga, Paul; Medley, Brooke; Lenaerts, Jan; Bertler, Nancy; van den Broeke, Michiel R.; Dixon, Daniel A.; Frezzotti, Massimo; Stenni, Barbara; Curran, Mark; Ekaykin, Alexey A.

    2017-11-01

    Here we present Antarctic snow accumulation variability at the regional scale over the past 1000 years. A total of 79 ice core snow accumulation records were gathered and assigned to seven geographical regions, separating the high-accumulation coastal zones below 2000 m of elevation from the dry central Antarctic Plateau. The regional composites of annual snow accumulation were evaluated against modelled surface mass balance (SMB) from RACMO2.3p2 and precipitation from ERA-Interim reanalysis. With the exception of the Weddell Sea coast, the low-elevation composites capture the regional precipitation and SMB variability as defined by the models. The central Antarctic sites lack coherency and either do not represent regional precipitation or indicate the model inability to capture relevant precipitation processes in the cold, dry central plateau. Our results show that SMB for the total Antarctic Ice Sheet (including ice shelves) has increased at a rate of 7 ± 0.13 Gt decade-1 since 1800 AD, representing a net reduction in sea level of ˜ 0.02 mm decade-1 since 1800 and ˜ 0.04 mm decade-1 since 1900 AD. The largest contribution is from the Antarctic Peninsula (˜ 75 %) where the annual average SMB during the most recent decade (2001-2010) is 123 ± 44 Gt yr-1 higher than the annual average during the first decade of the 19th century. Only four ice core records cover the full 1000 years, and they suggest a decrease in snow accumulation during this period. However, our study emphasizes the importance of low-elevation coastal zones, which have been under-represented in previous investigations of temporal snow accumulation.

  7. Regional Antarctic snow accumulation over the past 1000 years

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    E. R. Thomas

    2017-11-01

    Full Text Available Here we present Antarctic snow accumulation variability at the regional scale over the past 1000 years. A total of 79 ice core snow accumulation records were gathered and assigned to seven geographical regions, separating the high-accumulation coastal zones below 2000 m of elevation from the dry central Antarctic Plateau. The regional composites of annual snow accumulation were evaluated against modelled surface mass balance (SMB from RACMO2.3p2 and precipitation from ERA-Interim reanalysis. With the exception of the Weddell Sea coast, the low-elevation composites capture the regional precipitation and SMB variability as defined by the models. The central Antarctic sites lack coherency and either do not represent regional precipitation or indicate the model inability to capture relevant precipitation processes in the cold, dry central plateau. Our results show that SMB for the total Antarctic Ice Sheet (including ice shelves has increased at a rate of 7 ± 0.13 Gt decade−1 since 1800 AD, representing a net reduction in sea level of ∼ 0.02 mm decade−1 since 1800 and ∼ 0.04 mm decade−1 since 1900 AD. The largest contribution is from the Antarctic Peninsula (∼ 75 % where the annual average SMB during the most recent decade (2001–2010 is 123 ± 44 Gt yr−1 higher than the annual average during the first decade of the 19th century. Only four ice core records cover the full 1000 years, and they suggest a decrease in snow accumulation during this period. However, our study emphasizes the importance of low-elevation coastal zones, which have been under-represented in previous investigations of temporal snow accumulation.

  8. Satellite Observed Variability in Antarctic and Arctic Surface Temperatures and Their Correlation to Open Water Areas

    Science.gov (United States)

    Comiso, Josefino C.; Zukor, Dorothy (Technical Monitor)

    2000-01-01

    Recent studies using meterological station data have indicated that global surface air temperature has been increasing at a rate of 0.05 K/decade. Using the same set of data but for stations in the Antarctic and Arctic regions (>50 N) only, the increases in temperature were 0.08, and 0.22 K/decade, when record lengths of 100 and 50 years, respectively, were used. To gain insights into the increasing rate of warming, satellite infrared and passive microwave observations over the Arctic region during the last 20 years were processed and analyzed. The results show that during this period, the ice extent in the Antarctic has been increasing at the rate of 1.2% per decade while the surface temperature has been decreasing at about 0.08 K per decade. Conversely, in the Northern Hemisphere, the ice extent has been decreasing at a rate of 2.8% per decade, while the surface temperatures have been increasing at the rate of 0.38 K per decade. In the Antarctic, it is surprising that there is a short term trend of cooling during a global period of warming. Very large anomalies in open water areas in the Arctic were observed especially in the western region, that includes the Beaufort Sea, where the observed open water area was about 1x10(exp 6) sq km, about twice the average for the region, during the summer of 1998. In the eastern region, that includes the Laptev Sea, the area of open water was also abnormally large in the summer of 1995. Note that globally, the warmest and second warmest years in this century, were 1998 and 1995, respectively. The data, however, show large spatial variability with the open water area distribution showing a cyclic periodicity of about ten years, which is akin to the North Atlantic and Arctic Oscillations. This was observed in both western and eastern regions but with the phase of one lagging the other by about two years. This makes it difficult to interpret what the trends really mean. But although the record length of satellite data is still

  9. Recent Climate and Ice-Sheet Changes in West Antarctica Compared with the Past 2,000 Years

    Science.gov (United States)

    Steig, Eric J.; Ding, Qinghua; White, James W.; Kuttel, Marcel; Rupper, Summer B.; Neumann, Thomas Allen; Neff, Peter D.; Gallant, Ailie J. E.; Mayewski, Paul A.; Taylor, Kendrick C.; hide

    2013-01-01

    Changes in atmospheric circulation over the past five decades have enhanced the wind-driven inflow of warm ocean water onto the Antarctic continental shelf, where it melts ice shelves from below1-3. Atmospheric circulation changes have also caused rapid warming4 over the West Antarctic Ice Sheet, and contributed to declining sea-ice cover in the adjacent Amundsen-Bellingshausen seas5. It is unknown whether these changes are part of a longer-term trend. Here, we use waterisotope (Delta O-18) data from an array of ice-core records to place recent West Antarctic climate changes in the context of the past two millennia. We find that the d18O of West Antarctic precipitation has increased significantly in the past 50 years, in parallel with the trend in temperature, and was probably more elevated during the 1990s than at any other time during the past 200 years. However, Delta O-18 anomalies comparable to those of recent decades occur about 1% of the time over the past 2,000 years. General circulation model simulations suggest that recent trends in Delta O-18 and climate in West Antarctica cannot be distinguished from decadal variability that originates in the tropics. We conclude that the uncertain trajectory of tropical climate variability represents a significant source of uncertainty in projections of West Antarctic climate and ice-sheet change.

  10. Light intensity modulates the response of two Antarctic diatom species to ocean acidification

    Directory of Open Access Journals (Sweden)

    Jasmin Pascale Heiden

    2016-12-01

    Full Text Available It is largely unknown how rising atmospheric CO2 concentrations and changes in the upper mixed layer depth, with its subsequent effects on light availability will affect phytoplankton physiology in the Southern Ocean. Linking seasonal variations in the availability of CO2 and light to abundances and physiological traits of key phytoplankton species could aid to understand their abilities to acclimate to predicted future climatic conditions. To investigate the combined effects of CO2 and light on two ecologically relevant Antarctic diatoms (Fragilariopsis curta and Odontella weisflogii a matrix of three light intensities (LL=20, ML=200, HL=500 µmol photons m-2 s-1 and three pCO2 levels (low=180, ambient=380, high=1000 µatm was applied assessing their effects on growth, particulate organic carbon (POC fixation and photophysiology. Under ambient pCO2, POC production rates were highest already at low light in Fragilariopsis, indicating saturation of photosynthesis, while in Odontella highest rates were only reached at medium irradiances. In both species ocean acidification did not stimulate, but rather inhibited, growth and POC production under low and medium light. This effect was, however, amended under high growth irradiances. Low pCO2 levels inhibited growth and POC production in both species at low and medium light, and further decreased absETRs under high light. Our results suggest that Southern Ocean diatoms were sensitive to changes in pCO2, showing species-specific responses, which were further modulated by light intensity. The two diatom species represent distinct ecotypes and revealed discrete physiological traits that matched their seasonal occurrence with the related physical conditions in Antarctic coastal waters.

  11. Concentrations, metabolic clearance rates, production rates and plasma binding of cortisol in Antarctic phocid seals.

    Science.gov (United States)

    Liggins, G C; France, J T; Schneider, R C; Knox, B S; Zapol, W M

    1993-10-01

    We have reported previously that plasma of the Weddell seal, a member of the phocid family, contains a very high concentration of cortisol. The present study was undertaken to determine whether high cortisol levels were common to seals in the Antarctic environment, or to other phocidae, and to determine the mechanism of the hypercortisolaemia. High levels of cortisol (0.82-2.38 mumol/l) were found in 4 phocidae (Weddell, crabeater, leopard and Southern elephant seals), whereas levels in a member of the otariid family (Antarctic fur seal) were similar to human values. Metabolic clearance rates (MCR) and production rates (PR) of cortisol were determined in the field in Weddell (N = 1), crabeater (N = 3) and leopard (N = 3) seals following bolus injections of [3H] cortisol. The MCR and PR did not differ between the three phocids, but whereas the MCR of 410-590 1/day was twice that of human values, the PR of 460-1180 mumol.m-2 x d-1 was up to 40-fold greater. The binding capacity of corticosteroid-binding globulin (CBG) was equal to or greater than the plasma concentrations of cortisol, resulting in relatively low concentrations of free cortisol. We conclude that hypercortisolaemia is maintained in phocid seals mainly by a high production rate--the highest (corrected for surface area) reported in any species. The relatively low cortisol levels in otariid seals studied in the same environment suggest that the high PR in phocidae is unrelated to the harsh climatic conditions, but may be part of their adaptation for diving to extreme depths.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. When shape matters: strategies of different Antarctic ascidians morphotypes to deal with sedimentation.

    Science.gov (United States)

    Torre, Luciana; Abele, Doris; Lagger, Cristian; Momo, Fernando; Sahade, Ricardo

    2014-08-01

    Climate change leads to increased melting of tidewater glaciers in the Western Antarctic Peninsula region and sediment bearing glacial melt waters negatively affects filter feeding species as solitary ascidians. In previous work the erect-forms Molgula pedunculata and Cnemidocarpa verrucosa (Order Stolidobranchiata) appeared more sensitive than the flat form Ascidia challengeri (Order Phlebobranchiata). Sedimentation exposure is expected to induce up-regulation of anaerobic metabolism by obstructing the organs of gas exchange (environmental hypoxia) or causes enhanced squirting activity (functional hypoxia). In this study we evaluated the possible relationship between ascidian morphotype and their physiological response to sedimentation. Together with some behavioural observations, we analysed the response of anaerobic metabolic parameters (lactate formation and glycogen consumption) in different tissues of three Antarctic ascidians, exposed to high sediment concentrations (200 mgL(-1)). The results were compared to experimental hypoxia (10% pO2) and exercise (induced muscular contraction) effects, in order to discriminate the effect of sediment on each species and morpho-type (erect vs. flat forms). Our results suggest that the styled (erect) C. verrucosa increases muscular squirting activity in order to expulse excessive material, while the flat-form A. challengeri reacts more passively by down-regulating its aerobic metabolism under sediment exposure. Contrary, the erect ascidian M. pedunculata did not show any measurable response to the treatments, indicating that filtration and ingestion activities were not reduced or altered even under high sedimentation (low energetic material) which could be disadvantageous on the long-term and could explain why M. pedunculata densities decline in the study area. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Subglacial Calcites from Northern Victoria Land: archive of Antarctic volcanism in the Last Glacial Maximum

    Science.gov (United States)

    Frisia, Silvia; Weirich, Laura; Hellstrom, John; Borsato, Andrea; Golledge, Nicholas R.; Anesio, Alexandre M.; Bajo, Petra; Drysdale, Russell N.; Augustinus, Paul C.; Barbante, Carlo; Cooper, Alan

    2017-04-01

    Subglacial carbonates bear similarities to stalagmites in their fabrics and the potential to obtain precise chronologies using U-series methods. Their chemical properties also reflect those of their parent waters, which, in contrast to stalagmites, are those of subglacial meltwaters. In analogy to speleothems, stable Carbon isotope ratios and trace elements such as Uranium, Iron and Manganese provide the opportunity to investigate ancient extreme environments without the need to drill through thousands of metres of ice. Sedimentological, geochemical and microbial evidence preserved in LGM subglacial calcites from Northern Victoria Land, close to the East Antarctic Ice Sheet margin, allow us to infer that subglacial volcanism was active in the Trans Antarctic Mountain region and induced basal ice melting. We hypothesize that a meltwater reservoir was drained and injected into interconnected basal pore systems where microbial processes enhanced bedrock weathering and, thus, released micronutrients. Volcanic influence is supported by the presence of fluorine (F) and sulphur in sediment-laden calcite layers containing termophilic species. Notably, calcite δ13C points to dissolved inorganic carbon evolved from subglacial metabolic processes. Once transported to the sea, soluble iron likely contributed to fertilizing the Southern Ocean and CO2 drawdown. This is the first well-dated evidence for LGM volcanism in Antarctica, which complements the record of volcanic eruptions retrieved from Talos Dome ice core, and supports the hypothesis of large-scale volcanism as an important driver of climate change. We conclude that subglacial carbonates are equivalent to speleothems in their palaeoclimate potential and may become a most useful source of information of ecosystems and processes at peak glacials in high altitude/high latitude settings.

  14. Potential sea-level rise from Antarctic ice-sheet instability constrained by observations.

    Science.gov (United States)

    Ritz, Catherine; Edwards, Tamsin L; Durand, Gaël; Payne, Antony J; Peyaud, Vincent; Hindmarsh, Richard C A

    2015-12-03

    Large parts of the Antarctic ice sheet lying on bedrock below sea level may be vulnerable to marine-ice-sheet instability (MISI), a self-sustaining retreat of the grounding line triggered by oceanic or atmospheric changes. There is growing evidence that MISI may be underway throughout the Amundsen Sea embayment (ASE), which contains ice equivalent to more than a metre of global sea-level rise. If triggered in other regions, the centennial to millennial contribution could be several metres. Physically plausible projections are challenging: numerical models with sufficient spatial resolution to simulate grounding-line processes have been too computationally expensive to generate large ensembles for uncertainty assessment, and lower-resolution model projections rely on parameterizations that are only loosely constrained by present day changes. Here we project that the Antarctic ice sheet will contribute up to 30 cm sea-level equivalent by 2100 and 72 cm by 2200 (95% quantiles) where the ASE dominates. Our process-based, statistical approach gives skewed and complex probability distributions (single mode, 10 cm, at 2100; two modes, 49 cm and 6 cm, at 2200). The dependence of sliding on basal friction is a key unknown: nonlinear relationships favour higher contributions. Results are conditional on assessments of MISI risk on the basis of projected triggers under the climate scenario A1B (ref. 9), although sensitivity to these is limited by theoretical and topographical constraints on the rate and extent of ice loss. We find that contributions are restricted by a combination of these constraints, calibration with success in simulating observed ASE losses, and low assessed risk in some basins. Our assessment suggests that upper-bound estimates from low-resolution models and physical arguments (up to a metre by 2100 and around one and a half by 2200) are implausible under current understanding of physical mechanisms and potential triggers.

  15. Onset of Antarctic Circumpolar Current 30 million years ago as Tasmanian Gateway aligned with westerlies.

    Science.gov (United States)

    Scher, Howie D; Whittaker, Joanne M; Williams, Simon E; Latimer, Jennifer C; Kordesch, Wendy E C; Delaney, Margaret L

    2015-07-30

    Earth's mightiest ocean current, the Antarctic Circumpolar Current (ACC), regulates the exchange of heat and carbon between the ocean and the atmosphere, and influences vertical ocean structure, deep-water production and the global distribution of nutrients and chemical tracers. The eastward-flowing ACC occupies a unique circumglobal pathway in the Southern Ocean that was enabled by the tectonic opening of key oceanic gateways during the break-up of Gondwana (for example, by the opening of the Tasmanian Gateway, which connects the Indian and Pacific oceans). Although the ACC is a key component of Earth's present and past climate system, the timing of the appearance of diagnostic features of the ACC (for example, low zonal gradients in water-mass tracer fields) is poorly known and represents a fundamental gap in our understanding of Earth history. Here we show, using geophysically determined positions of continent-ocean boundaries, that the deep Tasmanian Gateway opened 33.5 ± 1.5 million years ago (the errors indicate uncertainty in the boundary positions). Following this opening, sediments from Indian and Pacific cores recorded Pacific-type neodymium isotope ratios, revealing deep westward flow equivalent to the present-day Antarctic Slope Current. We observe onset of the ACC at around 30 million years ago, when Southern Ocean neodymium isotopes record a permanent shift to modern Indian-Atlantic ratios. Our reconstructions of ocean circulation show that massive reorganization and homogenization of Southern Ocean water masses coincided with migration of the northern margin of the Tasmanian Gateway into the mid-latitude westerly wind band, which we reconstruct at 64° S, near to the northern margin. Onset of the ACC about 30 million years ago coincided with major changes in global ocean circulation and probably contributed to the lower atmospheric carbon dioxide levels that appear after this time.

  16. Temporal and Regional Variability in the Skin Microbiome of Humpback Whales along the Western Antarctic Peninsula.

    Science.gov (United States)

    Bierlich, K C; Miller, Carolyn; DeForce, Emelia; Friedlaender, Ari S; Johnston, David W; Apprill, Amy

    2018-03-01

    The skin is the first line of defense between an animal and its environment, and disruptions in skin-associated microorganisms can be linked to an animal's health and nutritional state. To better understand the skin microbiome of large whales, high-throughput sequencing of partial small subunit rRNA genes was used to study the skin-associated bacteria of 89 seemingly healthy humpback whales ( Megaptera novaeangliae ) sampled along the Western Antarctic Peninsula (WAP) during early (2010) and late (2013) austral summers. Six core groups of bacteria were present in 93% or more of all humpback skin samples. A shift was observed in the average relative abundances of these core bacteria over time, with the emergence of four additional core groups of bacteria that corresponded to a decrease in water temperature, possibly caused by season- or foraging-related changes in skin biochemistry that influenced microbial growth, or other temporal factors. The skin microbiome differed between whales sampled at several regional locations along the WAP, suggesting that environmental factors or population may also influence the whale skin microbiome. Overall, the skin microbiome of humpback whales appears to provide insight into animal- and environment-related factors and may serve as a useful indicator for animal health or ecosystem alterations. IMPORTANCE The microbiomes of wild animals are currently understudied but may provide information about animal health and/or animal-environment interactions. In the largest sampling of any marine mammal microbiome, this study demonstrates conservation in the skin microbiome of 89 seemingly healthy humpback whales sampled in the Western Antarctic Peninsula, with shifts in the bacterial community composition related to temporal and regional variability. This study is important because it suggests that the skin microbiome of humpback whales could provide insight into animal nutritional or seasonal/environment-related factors, which are becoming

  17. Novel Applications of Meteoric- and In Situ-Produced Beryllium-10 in the East Antarctic

    Science.gov (United States)

    Valletta, Rachel D.

    This work comprises three novel applications of in situ- and meteoric-produced beryllium-10 (Be-10) in East Antarctica. Sampled deposits cover a wide spatiotemporal transect through the Dry Valleys, from an inland, middle elevation location of Quaternary age, to a mid-valley, high elevation location of Miocene age, and finally to an offshore, submarine location of Pliocene age. Each research chapter we present is a unique project unto itself, but all chapters utilize the cosmogenic radionuclide Be-10. In the first application, we present "Difference Dating,'' a new approach to date glacial moraines in regions where traditional exposure age dating is fraught with complications. Difference Dating allows for the construction of deglaciation chronologies in regions where they are frequently precluded by inheritance issues. We use Difference Dating to constrain the ages of Quaternary moraines in an alpine glacial cirque, Wright Valley, Dry Valleys. The second and third applications use meteoric-produced Be-10 in two different depositional settings. In marine sediments, we recast the Be-10/Be-9 ratio as a proxy for East Antarctic Ice Sheet freshwater discharge during mid-Pliocene interglacials. Using this record, we suggest that zones of deep water formation may be significant in funneling Be into the global thermohaline circulation belt. We also apply the meteoric-produced Be-10 system to paleolake sediments, where extremely low concentrations are used to construct an age model extending to 14-17.5 Ma. This range is commensurate with lake sediment deposition during the Middle Miocene Climatic Optimum, a rare Antarctic terrestrial deposit of this globally significant warming event.

  18. Ice Algae-Produced Carbon Is Critical for Overwintering of Antarctic Krill Euphausia superba

    Directory of Open Access Journals (Sweden)

    Doreen Kohlbach

    2017-09-01

    Full Text Available Antarctic krill Euphausia superba (“krill” constitute a fundamental food source for Antarctic seabirds and mammals, and a globally important fisheries resource. The future resilience of krill to climate change depends critically on the winter survival of young krill. To survive periods of extremely low production by pelagic algae during winter, krill are assumed to rely partly on carbon produced by ice algae. The true dependency on ice algae-produced carbon, however, is so far unquantified. This confounds predictions on the future resilience of krill stocks to sea ice decline. Fatty acid (FA analysis, bulk stable isotope analysis (BSIA, and compound-specific stable isotope analysis (CSIA of diatom- and dinoflagellate-associated marker FAs were applied to quantify the dependency of overwintering larval, juvenile, and adult krill on ice algae-produced carbon (αIce during winter 2013 in the Weddell-Scotia Confluence Zone. Our results demonstrate that the majority of the carbon uptake of the overwintering larval and juvenile krill originated from ice algae (up to 88% of the carbon budget, and that the dependency on ice algal carbon decreased with ontogeny, reaching <56% of the carbon budget in adults. Spatio-temporal variability in the utilization of ice algal carbon was more pronounced in larvae and juvenile krill than in adults. Differences between αIce estimates derived from short- vs. long-term FA-specific isotopic compositions suggested that ice algae-produced carbon gained importance as the winter progressed, and might become critical at the late winter-spring transition, before the phytoplankton bloom commences. Where the sea ice season shortens, reduced availability of ice algae might possibly not be compensated by surplus phytoplankton production during wintertime. Hence, sea ice decline could seriously endanger the winter survival of recruits, and subsequently overall biomass of krill.

  19. Design and implementation of a Cube satellite mission for Antarctic glacier and sea ice observation

    Science.gov (United States)

    Wu, Shufan; Zhao, Tiancheng; Gao, Yuan; Cheng, Xiao

    2017-10-01

    The research for global climate changes calls for high quality satellite data and imageries regarding the Polar Regions. In recent years, the emerging Earth-Observation micro/nano satellite technology provides new data sources for polar region observations. The STU-2A, also named TW-1A, is such a nano satellite designed for polar region observation activities. It is a 3U CubeSat of 2.9 kg with a size of 30 × 10 × 10 cm carrying an Earth observation camera, launched into a Sun Synchronous Orbit (SSO) at 481 km with an inclination of 97.3°, on September 25, 2015. During the Antarctic summer of 2015/16, it has acquired visible-light true color images with a resolution of 94 m, covering different sea and coastal regions including Amundsen Sea, Ross Sea and Vincennes Bay. These images were used to analyze the change of glacier and sea ice, compared and calibrated with reference to the publically available MODIS images with a resolution of 250 m. As the camera was specially designed for the Polar regions which have an environment of low solar elevation angle and high surface reflectance, it eliminates the oversaturation problem of the MODIS sensors and can provide high quality images. Based on data analysis and assessment, it is confirmed that this satellite data can meet the demand of glacier and sea ice observation. This paper presents the Cubesat system design and configuration, the payload camera design, and its application in Antarctic glacier and sea ice observation.

  20. At-Sea Distribution and Prey Selection of Antarctic Petrels and Commercial Krill Fisheries.

    Directory of Open Access Journals (Sweden)

    Sébastien Descamps

    Full Text Available Commercial fisheries may impact marine ecosystems and affect populations of predators like seabirds. In the Southern Ocean, there is an extensive fishery for Antarctic krill Euphausia superba that is projected to increase further. Comparing distribution and prey selection of fishing operations versus predators is needed to predict fishery-related impacts on krill-dependent predators. In this context, it is important to consider not only predators breeding near the fishing grounds but also the ones breeding far away and that disperse during the non-breeding season where they may interact with fisheries. In this study, we first quantified the overlap between the distribution of the Antarctic krill fisheries and the distribution of a krill dependent seabird, the Antarctic petrel Thalassoica antarctica, during both the breeding and non-breeding season. We tracked birds from the world biggest Antarctic petrel colony (Svarthamaren, Dronning Maud Land, located >1000 km from the main fishing areas, during three consecutive seasons. The overall spatial overlap between krill fisheries and Antarctic petrels was limited but varied greatly among and within years, and was high in some periods during the non-breeding season. In a second step, we described the length frequency distribution of Antarctic krill consumed by Antarctic petrels, and compared this with results from fisheries, as well as from diet studies in other krill predators. Krill taken by Antarctic petrels did not differ in size from that taken by trawls or from krill taken by most Antarctic krill predators. Selectivity for specific Antarctic krill stages seems generally low in Antarctic predators. Overall, our results show that competition between Antarctic petrels and krill fisheries is currently likely negligible. However, if krill fisheries are to increase in the future, competition with the Antarctic petrel may occur, even with birds breeding thousands of kilometers away.

  1. Signature spectrale des grains interstellaires.

    Science.gov (United States)

    Léger, A.

    Notre connaissance de la nature des grains interstellaires reposait sur un nombre très restreint de signatures spectrales dans la courbe d'extinction du milieu interstellaire. Une information considérable est contenue dans les 40 bandes interstellaires diffuses dans le visible, mais reste inexploitée. L'interprétation récente des cinq bandes IR en émission, en terme de molécules d'hydrocarbures aromatiques polycycliques, est développée. Elle permet l'utilisation d'une information spectroscopique comparable, à elle seule, à ce sur quoi était basée jusqu'alors notre connaissance de la matière interstellaire condensée. Différentes implications de cette mise en évidence sont proposées.

  2. Molecular ecophysiology of Antarctic notothenioid fishes.

    Science.gov (United States)

    Cheng, C-H Christina; Detrich, H William

    2007-12-29

    The notothenioid fishes of the Southern Ocean surrounding Antarctica are remarkable examples of organismal adaptation to extreme cold. Their evolution since the mid-Miocene in geographical isolation and a chronically cold marine environment has resulted in extreme stenothermality of the extant species. Given the unique thermal history of the notothenioids, one may ask what traits have been gained, and conversely, what characters have been lost through change in the information content of their genomes. Two dramatic changes that epitomize such evolutionary transformations are the gain of novel antifreeze proteins, which are obligatory for survival in icy seawater, by most notothenioids and the paradoxical loss of respiratory haemoproteins and red blood cells, normally deemed indispensable for vertebrate life, by the species of a highly derived notothenioid family, the icefishes. Here, we review recent advances in our understanding of these traits and their evolution and suggest future avenues of investigation. The formerly coherent paradigm of notothenioid freeze avoidance, developed from three decades of study of antifreeze glycoprotein (AFGP) based cold adaptation, now faces challenges stemming from the recent discovery of antifreeze-deficient, yet freeze-resistant, early notothenioid life stages and from definitive evidence that the liver is not the physiological source of AFGPs in notothenioid blood. The resolution of these intriguing observations is likely to reveal new physiological traits that are unique to the notothenioids. Similarly, the model of AFGP gene evolution from a notothenioid pancreatic trypsinogen-like gene precursor is being expanded and refined based on genome-level analyses of the linked AFGP loci and their ancestral precursors. Finally, the application of comparative genomics to study evolutionary change in the AFGP genotypes of cool-temperate notothenioids from sub-Antarctic habitats, where these genes are not necessary, will contribute to

  3. Prediction of soil effects on GPR signatures

    NARCIS (Netherlands)

    Rhebergen, J.B.; Lensen, H.A.; Wijk, C.V. van; Hendrickx, J.M.H.; Dam, R. van; Borchers, B.

    2004-01-01

    In previous work we have shown that GPR signatures are affected by soil texture and soil water content. In this contribution we will use a three dimensional electromagnetic model and a hydrological soil model to explore in more detail the relationships between GPR signatures, soil physical

  4. Measuring ship acoustic signatures against mine threat

    NARCIS (Netherlands)

    Jong, C.A.F. de; Quesson, B.A.J.; Ainslie, M.A.; Vermeulen, R.C.N.

    2012-01-01

    The NATO standard ‘AMP-15’ [1] provides procedures for the measurement and reporting of the acoustic signature of ships and for the establishment of acoustic signature goals to counter the naval mine threat. Measurements are carried out at dedicated shallow water acoustic ranges. Measurements

  5. The Pedagogic Signature of the Teaching Profession

    Science.gov (United States)

    Kiel, Ewald; Lerche, Thomas; Kollmannsberger, Markus; Oubaid, Viktor; Weiss, Sabine

    2016-01-01

    Lee S. Shulman deplores that the field of education as a profession does not have a pedagogic signature, which he characterizes as a synthesis of cognitive, practical and moral apprenticeship. In this context, the following study has three goals: 1) In the first theoretical part, the basic problems of constructing a pedagogic signature are…

  6. Infrared ship signature analysis and optimisation

    NARCIS (Netherlands)

    Neele, F.P.

    2005-01-01

    The last decade has seen an increase in the awareness of the infrared signature of naval ships. New ship designs show that infrared signature reduction measures are being incorporated, such as exhaust gas cooling systems, relocation of the exhausts and surface cooling systems. Hull and

  7. Quantum signature scheme for known quantum messages

    International Nuclear Information System (INIS)

    Kim, Taewan; Lee, Hyang-Sook

    2015-01-01

    When we want to sign a quantum message that we create, we can use arbitrated quantum signature schemes which are possible to sign for not only known quantum messages but also unknown quantum messages. However, since the arbitrated quantum signature schemes need the help of a trusted arbitrator in each verification of the signature, it is known that the schemes are not convenient in practical use. If we consider only known quantum messages such as the above situation, there can exist a quantum signature scheme with more efficient structure. In this paper, we present a new quantum signature scheme for known quantum messages without the help of an arbitrator. Differing from arbitrated quantum signature schemes based on the quantum one-time pad with the symmetric key, since our scheme is based on quantum public-key cryptosystems, the validity of the signature can be verified by a receiver without the help of an arbitrator. Moreover, we show that our scheme provides the functions of quantum message integrity, user authentication and non-repudiation of the origin as in digital signature schemes. (paper)

  8. Analysis of signature wrapping attacks and countermeasures

    DEFF Research Database (Denmark)

    Gajek, Sebastian; Jensen, Meiko; Liao, Lijun

    2009-01-01

    In recent research it turned out that Boolean verification, of digital signatures in the context of WSSecurity, is likely to fail: If parts of a SOAP message, are signed and the signature verification applied to, the whole document returns true, then nevertheless the, document may have been...

  9. Analysis of Glacial Change in the Northern Antarctic Peninsula Region Using Photogrammetry

    Science.gov (United States)

    Vargas, W.; Arkle, J.; Devillier, K.; Neely, N.; Velasco, A. A.

    2009-05-01

    Clearly and robustly documenting global climate change over this past century remains a key goal for researchers. Polar regions are an ideal place to study change, since they are particularly sensitive to temperature changes. As part of an International Polar Year (IPY) grant called IPY-ROAM (Research and Educational Opportunities in Antarctica for Minorities), faculty at the University of Texas at El Paso (UTEP) took 29 underrepresented minority students and teachers on a research expedition to Antarctica over winter break 2007. One goal of the program was to document glacial change along the Antarctic Peninsula over the past century using photogrammetry, a technique that uses photos to make accurate geographic measurements. Prior to embarkation, we gathered historic photos of glaciers along our travel route. During the expedition, new photos were taken within the old photo sites, where we made Global Positioning System (GPS) readings and accurately measurement angles to the geographic features. The geographic features (including top and bottom of a glacier) were then mapped onto a Geographical Information Systems (GIS) that allowed us to determine location, scale and distance to these features on the photos. With the angle and distance, the height difference between the old and current photo of the glacier was calculated using basic trigonometric functions. In one case, we determined a 14 m reduction in glacier height from 1934 to 2007. Future work will include analysis from more glaciers in the region, and to determine if there is a correlation between glacier retreat and climate change. ROAM/index.html

  10. Temporal variability of the Antarctic Ice sheet observed from space-based geodesy

    Science.gov (United States)

    Memin, A.; King, M. A.; Boy, J. P.; Remy, F.

    2017-12-01

    Quantifying the Antarctic Ice Sheet (AIS) mass balance still remains challenging as several processes compete to differing degrees at the basin scale with regional variations, leading to multiple mass redistribution patterns. For instance, analysis of linear trends in surface-height variations from 1992-2003 and 2002-2006 shows that the AIS is subject to decimetric scale variability over periods of a few years. Every year, snowfalls in Antarctica represent the equivalent of 6 mm of the mean sea level. Therefore, any fluctuation in precipitation can lead to changes in sea level. Besides, over the last decade, several major glaciers have been thinning at an accelerating rate. Understanding the processes that interact on the ice sheet is therefore important to precisely determine the response of the ice sheet to a rapid changing climate and estimate its contribution to sea level changes. We estimate seasonal and interannual changes of the AIS between January 2003 and October 2010 and to the end of 2016 from a combined analysis of surface-elevation and surface-mass changes derived from Envisat data and GRACE solutions, and from GRACE solutions only, respectively. While we obtain a good correlation for the interannual signal between the two techniques, important differences (in amplitude, phase, and spatial pattern) are obtained for the seasonal signal. We investigate these discrepancies by comparing the crustal motion observed by GPS and those predicted using monthly surface mass balance derived from the regional atmospheric climate model RACMO.

  11. The topographic signature of anthropogenic geomorphic processes

    Science.gov (United States)

    Tarolli, P.; Sofia, G.

    2014-12-01

    Within an abiotic-dominated context, geomorphologic patterns and dynamics are single expressions of trade-offs between the physical resistance forces, and the mechanical and chemical forces related to climate and erosion. Recently, however, it has become essential for the geomorphological community to take into account also biota as a fundamental geomorphologic agent acting from local to regional scales. However, while there is a recent flourishing literature about the impacts of vegetation on geomorphic processes, the study of anthropogenic pressure on geomorphology is still at its early stages. Humans are indeed among the most prominent geomorphic agents, redistributing land surface, and causing drastic changes to the geomorphic organization of the landscape (e.g. intensive agriculture, urbanization), with direct consequences on land degradation and watershed response. The reconstruction or identification of artificial or anthropogenic topographies, therefore, provides a mechanism for quantifying anthropogenic changes to the landscape systems in the context of the Anthropocene epoch. High-resolution topographic data derived from the recent remote sensing technologies (e.g. lidar, SAR, SfM), offer now new opportunities to recognize better understand geomorphic processes from topographic signatures, especially in engineered landscapes where the direct anthropic alteration of processes is significant. It is possible indeed to better recognize human-induced geomorphic and anthropogenic features (e.g. road networks, agricultural terraces), and the connected erosion. The study presented here may allow improved understanding and targeted mitigation of the processes driving geomorphic changes during urban development and help guide future research directions for development-based watershed studies. Human society is deeply affecting the environment with consequences on the landscape. It is therefore fundamental to establish greater management control over the Earth

  12. Persistent solar signatures in cloud cover: spatial and temporal analysis</