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

    2017-11-28

    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. 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 ...

  7. The Antarctic - the wild card in the global climate

    International Nuclear Information System (INIS)

    Oesterhus, Svein; Gammelsroed, Tor; Foldvik, Arne; Noest, Ole Anders

    1999-01-01

    The overview gives an account of studies of snowfall, ice melting and formation and water flow patterns in the Antarctic during the present global warming period. It also gives a survey of the ice area in the region. The sea water warming is dramatic and a large floating glacier seems to be decomposing which is disrupting the oceanographic and ecological relations in the region and globally and is significantly influencing the global climate

  8. 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.

  9. 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.

  10. 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

  11. 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)

  12. High-resolution climate modelling of Antarctica and the Antarctic Peninsula

    NARCIS (Netherlands)

    van Wessem, J.M.|info:eu-repo/dai/nl/413533085

    2016-01-01

    In this thesis we have used a high-resolution regional atmospheric climate model (RACMO2.3) to simulate the present-day climate (1979-2014) of Antarctica and the Antarctic Peninsula. We have evaluated the model results with several observations, such as in situ surface energy balance (SEB)

  13. 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...

  14. 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...

  15. 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

  16. Icebergs, sea ice, blue carbon and Antarctic climate feedbacks.

    Science.gov (United States)

    Barnes, David K A; Fleming, Andrew; Sands, Chester J; Quartino, Maria Liliana; Deregibus, Dolores

    2018-06-28

    Sea ice, including icebergs, has a complex relationship with the carbon held within animals (blue carbon) in the polar regions. Sea-ice losses around West Antarctica's continental shelf generate longer phytoplankton blooms but also make it a hotspot for coastal iceberg disturbance. This matters because in polar regions ice scour limits blue carbon storage ecosystem services, which work as a powerful negative feedback on climate change (less sea ice increases phytoplankton blooms, benthic growth, seabed carbon and sequestration). This resets benthic biota succession (maintaining regional biodiversity) and also fertilizes the ocean with nutrients, generating phytoplankton blooms, which cascade carbon capture into seabed storage and burial by benthos. Small icebergs scour coastal shallows, whereas giant icebergs ground deeper, offshore. Significant benthic communities establish where ice shelves have disintegrated (giant icebergs calving), and rapidly grow to accumulate blue carbon storage. When 5000 km 2 giant icebergs calve, we estimate that they generate approximately 10 6 tonnes of immobilized zoobenthic carbon per year (t C yr -1 ). However, their collisions with the seabed crush and recycle vast benthic communities, costing an estimated 4 × 10 4  t C yr -1 We calculate that giant iceberg formation (ice shelf disintegration) has a net potential of approximately 10 6  t C yr -1 sequestration benefits as well as more widely known negative impacts.This article is part of the theme issue 'The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change'. © 2018 The Authors.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. Peatland Ecosystem Processes in the Maritime Antarctic During Warm Climates.

    Science.gov (United States)

    Loisel, Julie; Yu, Zicheng; Beilman, David W; Kaiser, Karl; Parnikoza, Ivan

    2017-09-27

    We discovered a 50-cm-thick peat deposit near Cape Rasmussen (65.2°S), in the maritime Antarctic. To our knowledge, while aerobic 'moss banks' have often been examined, waterlogged 'peatlands' have never been described in this region before. The waterlogged system is approximately 100 m 2 , with a shallow water table. Surface vegetation is dominated by Warnstorfia fontinaliopsis, a wet-adapted moss commonly found in the Antarctic Peninsula. Peat inception was dated at 2750 cal. BP and was followed by relatively rapid peat accumulation (~0.1 cm/year) until 2150 cal. BP. Our multi-proxy analysis then shows a 2000-year-long stratigraphic hiatus as well as the recent resurgence of peat accumulation, sometime after 1950 AD. The existence of a thriving peatland at 2700-2150 cal. BP implies regionally warm summer conditions extending beyond the mid-Holocene; this finding is corroborated by many regional records showing moss bank initiation and decreased sea ice extent during this time period. Recent peatland recovery at the study site (maritime Antarctic region may promote a more peatland-rich landscape in the future.

  2. Modeling Antarctic Ice Sheet retreat in warm climates: a historical perspective.

    Science.gov (United States)

    Pollard, D.; Deconto, R. M.; Gasson, E.

    2016-12-01

    Early modeling of Antarctic Ice Sheet size vs. climate focused on asymmetry between retreat and growth, with much greater warming needed to cause retreat from full ice cover, due to Height Mass Balance Feedback and albedo feedback. This led to a long-standing model-data conflict, with models needing 1000 to2000 ppmv atmospheric CO2 to produce retreat from full size, vs. proxy data of large ice fluctuations despite much lower CO2 since the Miocene.Subsequent modeling with marine ice physics found that the West Antarctic Ice Sheet could undergo repeated warm-period collapses with realistic past forcing. However, that yields only 3 to 7 m equivalent sea-level rise above modern, compared to 10 to 20 m or more suggested by some geologic data. Large subglacial basins in East Antarctica could be vulnerable to the same processes,but did not retreat in most models due to narrower and shallower sills.After recent modifications, some ice sheet models were able to produce warm-period collapse of major East Antarctic basins, with sea-level rise of up to 15 m. The modifications are (i) hydrofracturing by surface melt, and structural failure of ice cliffs, or (ii) numerical treatment at the grounding line. In these models, large retreat occurs both for past warmintervals, and also for future business-as-usual scenarios.Some interpretations of data in the late Oligocene and Miocene suggest yet larger fluctuations, between 50 to 100% of modern Antarctic size. That would require surface-melt driven retreat of some terrestrial East Antarctic ice, despite the hysteresis issue raised above. A recent study using a coupled climate-ice sheet model found that with a finer climate gridand more frequent coupling exchange, substantial retreat of terrestrial Antarctica can occur with 500 to 840 ppmv CO2, much lower than in earlier models. This will allow meaningful interactions between modeling and deeper-time geologic interpretations since the late Oligocene.

  3. 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.

  4. The temperature signature of an IMF-driven change to the global atmospheric electric circuit (GEC) in the Antarctic troposphere

    Science.gov (United States)

    Freeman, Mervyn; Lam, Mai Mai; Chisham, Gareth

    2017-04-01

    We use National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data to show that Antarctic surface air temperature anomalies result from differences in the daily-mean duskward component,By, of the interplanetary magnetic field (IMF). We find the anomalies have strong geographical and seasonal variations. Regional anomalies are evident poleward of 60˚ S and are of diminishing representative peak amplitude from autumn (3.2˚ C) to winter (2.4˚ C) to spring (1.6˚ C) to summer (0.9˚ C). We demonstrate that anomalies of statistically-significant amplitude are due to geostrophic wind anomalies, resulting from the same By changes, moving air across large meridional gradients in zonal mean air temperature between 60 and 80˚ S. Additionally, we find that the mean tropospheric temperature anomaly for geographical latitudes ≤ -70˚ peaks at about 0.7 K and is statistically significant at the 1 - 5% level between air pressures of 1000 and 500 hPa (i.e., ˜0.1 to 5.6 km altitude above sea level) and for time lags with respect to the IMF of up to 7 days. The signature propagates vertically between air pressure p ≥ 850 hPa (≤ 1.5 km) and p = 500 hPa (˜5.6 km). The characteristics of prompt response and vertical propagation within the troposphere have previously been seen in the correlation between the IMF and high-latitude air pressure anomalies, known as the Mansurov effect, at higher statistical significances (1%). We conclude that we have identified the temperature signature of the Mansurov effect in the Antarctic troposphere. Since these tropospheric anomalies have been associated with By-driven anomalies in the electric potential of the ionosphere, we further conclude that they are caused by IMF-induced changes to the global atmospheric electric circuit (GEC). Our results support the view that variations in the ionospheric potential act on the troposphere via the action of resulting variations in the

  5. An ikaite record of late Holocene climate at the Antarctic Peninsula

    Science.gov (United States)

    Lu, Zunli; Rickaby, Rosalind E. M.; Kennedy, Hilary; Kennedy, Paul; Pancost, Richard D.; Shaw, Samuel; Lennie, Alistair; Wellner, Julia; Anderson, John B.

    2012-04-01

    Calcium carbonate can crystallize in a hydrated form as ikaite at low temperatures. The hydration water in ikaite grown in laboratory experiments records the δ18O of ambient water, a feature potentially useful for reconstructing δ18O of local seawater. We report the first downcore δ18O record of natural ikaite hydration waters and crystals collected from the Antarctic Peninsula (AP), a region sensitive to climate fluctuations. We are able to establish the zone of ikaite formation within shallow sediments, based on porewater chemical and isotopic data. Having constrained the depth of ikaite formation and δ18O of ikaite crystals and hydration waters, we are able to infer local changes in fjord δ18O versus time during the late Holocene. This ikaite record qualitatively supports that both the Medieval Warm Period and Little Ice Age extended to the Antarctic Peninsula.

  6. Ice core melt features in relation to Antarctic coastal climate

    NARCIS (Netherlands)

    Kaczmarska, M.; Isaksson, E.; Karlöf, L.; Brandt, O.; Winther, J.G.; van de Wal, R.S.W.; van den Broeke, M.R.; Johnsen, S.J.

    2006-01-01

    Measurement of light intensity transmission was carried out on an ice core S100 from coastal Dronning Maud Land (DML). Ice lenses were observed in digital pictures of the core and recorded as peaks in the light transmittance record. The frequency of ice layer occurrence was compared with climate

  7. 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

  8. 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

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

    Directory of Open Access Journals (Sweden)

    Y. P. Munoz

    2018-01-01

    Full Text Available 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.

  10. 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.

  11. 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.

  12. 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.)

  13. 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

  14. 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

    2007-01-29

    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.

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. The Global and Local Climatic Response to the Collapse of the West Antarctic Ice Sheet

    Science.gov (United States)

    Huybers, K. M.; Singh, H.; Steiger, N. J.; Frierson, D. M.; Steig, E. J.; Bitz, C. M.

    2014-12-01

    Glaciologists have suggested that a relatively small external forcing may compromise the stability of the West Antarctic Ice Sheet (WAIS). Further, there is compelling physical evidence that the WAIS has collapsed in the past, at times when the mean global temperature was only a few degrees warmer than it is today. In addition to a rapid increase in global sea level, the collapse of the WAIS could also affect the global circulation of the atmosphere. Ice sheets are some of the largest topographic features on Earth, causing large regional anomalies in albedo and radiative balance. Our work uses idealized aquaplanet models in tandem with a fully coupled ocean/atmosphere/sea-ice model (CCSM4) to compare the atmospheric, radiative, and oceanic response to a complete loss of the WAIS. Initial findings indicate that the loss of the WAIS leads to a weakening and equator-ward shift of the zonal winds, a development of strong zonal asymmetries in the meridional wind, and a northward migration of the Intertropical Convergence Zone. We aim to characterize how the local and global climate is affected by the presence of the WAIS, and how changes in the distribution of Southern Hemisphere ice may be represented in the proxy record.

  3. 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.

  4. Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma

    Directory of Open Access Journals (Sweden)

    N. R. Golledge

    2017-07-01

    Full Text Available The geometry of Antarctic ice sheets during warm periods of the geological past is difficult to determine from geological evidence, but is important to know because such reconstructions enable a more complete understanding of how the ice-sheet system responds to changes in climate. Here we investigate how Antarctica evolved under orbital and greenhouse gas conditions representative of an interglacial in the early Pliocene at 4.23 Ma, when Southern Hemisphere insolation reached a maximum. Using offline-coupled climate and ice-sheet models, together with a new synthesis of high-latitude palaeoenvironmental proxy data to define a likely climate envelope, we simulate a range of ice-sheet geometries and calculate their likely contribution to sea level. In addition, we use these simulations to investigate the processes by which the West and East Antarctic ice sheets respond to environmental forcings and the timescales over which these behaviours manifest. We conclude that the Antarctic ice sheet contributed 8.6 ± 2.8 m to global sea level at this time, under an atmospheric CO2 concentration identical to present (400 ppm. Warmer-than-present ocean temperatures led to the collapse of West Antarctica over centuries, whereas higher air temperatures initiated surface melting in parts of East Antarctica that over one to two millennia led to lowering of the ice-sheet surface, flotation of grounded margins in some areas, and retreat of the ice sheet into the Wilkes Subglacial Basin. The results show that regional variations in climate, ice-sheet geometry, and topography produce long-term sea-level contributions that are non-linear with respect to the applied forcings, and which under certain conditions exhibit threshold behaviour associated with behavioural tipping points.

  5. Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma

    Science.gov (United States)

    Golledge, Nicholas R.; Thomas, Zoë A.; Levy, Richard H.; Gasson, Edward G. W.; Naish, Timothy R.; McKay, Robert M.; Kowalewski, Douglas E.; Fogwill, Christopher J.

    2017-07-01

    The geometry of Antarctic ice sheets during warm periods of the geological past is difficult to determine from geological evidence, but is important to know because such reconstructions enable a more complete understanding of how the ice-sheet system responds to changes in climate. Here we investigate how Antarctica evolved under orbital and greenhouse gas conditions representative of an interglacial in the early Pliocene at 4.23 Ma, when Southern Hemisphere insolation reached a maximum. Using offline-coupled climate and ice-sheet models, together with a new synthesis of high-latitude palaeoenvironmental proxy data to define a likely climate envelope, we simulate a range of ice-sheet geometries and calculate their likely contribution to sea level. In addition, we use these simulations to investigate the processes by which the West and East Antarctic ice sheets respond to environmental forcings and the timescales over which these behaviours manifest. We conclude that the Antarctic ice sheet contributed 8.6 ± 2.8 m to global sea level at this time, under an atmospheric CO2 concentration identical to present (400 ppm). Warmer-than-present ocean temperatures led to the collapse of West Antarctica over centuries, whereas higher air temperatures initiated surface melting in parts of East Antarctica that over one to two millennia led to lowering of the ice-sheet surface, flotation of grounded margins in some areas, and retreat of the ice sheet into the Wilkes Subglacial Basin. The results show that regional variations in climate, ice-sheet geometry, and topography produce long-term sea-level contributions that are non-linear with respect to the applied forcings, and which under certain conditions exhibit threshold behaviour associated with behavioural tipping points.

  6. 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.

  7. Airspace: Antarctic Sound Transmission

    OpenAIRE

    Polli, Andrea

    2009-01-01

    This paper investigates how sound transmission can contribute to the public understanding of climate change within the context of the Poles. How have such transmission-based projects developed specifically in the Arctic and Antarctic, and how do these works create alternative pathways in order to help audiences better understand climate change? The author has created the media project Sonic Antarctica from a personal experience of the Antarctic. The work combines soundscape recordings and son...

  8. Unexpected effects of climate change on the predation of Antarctic petrels

    NARCIS (Netherlands)

    Franeker, van J.A.; Creuwels, J.C.S.; Veer, van der W.; Cleland, S.; Robertson, G.

    2001-01-01

    Antarctic petrels Thalassoica antarctica on Ardery Island, Antarctica (66°S, 110°E), experienced major reductions in breeding success and breeder survival over four seasons between 1984/85 and 1996/97. In 1996 the reason was revealed. A large snowdrift covered part of the study colony on the cliffs.

  9. Signatures of Climatic Change In Human Mitochondrial Dna From Europe

    Science.gov (United States)

    Richards, M. B.; Macaulay, V. A.; Torroni, A.; Bandelt, H.-J.

    Founder analysis is an approach to analysing non-recombining DNA sequence data, such as variation in the mitochondrial DNA (mtDNA), which aims at identifying and dating migrations into new territory. We applied the approach to about 4,000 human mtDNA sequences from Europe and the Near East, in order to estimate the proportion of modern lineages whose ancestors arrived at various times during the continent's past. We found that the major signal dates to about 15,000 years ago, at the time of rewarming following the Last Glacial Maximum (LGM). There is little or no archaeological evidence for immigration into Europe at this time, and the record indicates that at least parts of southern Europe remained populated during the LGM. Therefore, we interpret this signal as the trace of a bottleneck at the time of the LGM, as a result of the retreat from northern Europe during the peak of the glaciation, followed by a re-expansion from one or more refugial zones. Immigration episodes then figure at the beginning of the Early Upper Palaeolithic, during the Middle Upper Palaeolithic, and with the Neolithic. The impact of the latter on the composition of the European mtDNA pool was evidently rather minor. This result implies that climate is likely to have been a major force shaping human demographic history in Europe.

  10. 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)

  11. 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.

  12. The genome of the Antarctic-endemic copepod, Tigriopus kingsejongensis.

    Science.gov (United States)

    Kang, Seunghyun; Ahn, Do-Hwan; Lee, Jun Hyuck; Lee, Sung Gu; Shin, Seung Chul; Lee, Jungeun; Min, Gi-Sik; Lee, Hyoungseok; Kim, Hyun-Woo; Kim, Sanghee; Park, Hyun

    2017-01-01

    The Antarctic intertidal zone is continuously subjected to extremely fluctuating biotic and abiotic stressors. The West Antarctic Peninsula is the most rapidly warming region on Earth. Organisms living in Antarctic intertidal pools are therefore interesting for research into evolutionary adaptation to extreme environments and the effects of climate change. We report the whole genome sequence of the Antarctic-endemic harpacticoid copepod Tigriopus kingsejongensi . The 37 Gb raw DNA sequence was generated using the Illumina Miseq platform. Libraries were prepared with 65-fold coverage and a total length of 295 Mb. The final assembly consists of 48 368 contigs with an N50 contig length of 17.5 kb, and 27 823 scaffolds with an N50 contig length of 159.2 kb. A total of 12 772 coding genes were inferred using the MAKER annotation pipeline. Comparative genome analysis revealed that T. kingsejongensis -specific genes are enriched in transport and metabolism processes. Furthermore, rapidly evolving genes related to energy metabolism showed positive selection signatures. The T. kingsejongensis genome provides an interesting example of an evolutionary strategy for Antarctic cold adaptation, and offers new genetic insights into Antarctic intertidal biota. © The Author 2017. Published by Oxford University Press.

  13. 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

  14. 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.

  15. 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.

  16. Tropospheric jet response to Antarctic ozone depletion: An update with Chemistry-Climate Model Initiative (CCMI) models

    Science.gov (United States)

    Son, Seok-Woo; Han, Bo-Reum; Garfinkel, Chaim I.; Kim, Seo-Yeon; Park, Rokjin; Abraham, N. Luke; Akiyoshi, Hideharu; Archibald, Alexander T.; Butchart, N.; Chipperfield, Martyn P.; Dameris, Martin; Deushi, Makoto; Dhomse, Sandip S.; Hardiman, Steven C.; Jöckel, Patrick; Kinnison, Douglas; Michou, Martine; Morgenstern, Olaf; O’Connor, Fiona M.; Oman, Luke D.; Plummer, David A.; Pozzer, Andrea; Revell, Laura E.; Rozanov, Eugene; Stenke, Andrea; Stone, Kane; Tilmes, Simone; Yamashita, Yousuke; Zeng, Guang

    2018-05-01

    The Southern Hemisphere (SH) zonal-mean circulation change in response to Antarctic ozone depletion is re-visited by examining a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models reasonably well reproduce Antarctic ozone depletion in the late 20th century. The related SH-summer circulation changes, such as a poleward intensification of westerly jet and a poleward expansion of the Hadley cell, are also well captured. All experiments exhibit quantitatively the same multi-model mean trend, irrespective of whether the ocean is coupled or prescribed. Results are also quantitatively similar to those derived from the Coupled Model Intercomparison Project phase 5 (CMIP5) high-top model simulations in which the stratospheric ozone is mostly prescribed with monthly- and zonally-averaged values. These results suggest that the ozone-hole-induced SH-summer circulation changes are robust across the models irrespective of the specific chemistry-atmosphere-ocean coupling.

  17. Group Climate & Individual Functioning in an All-women Antarctic Expedition Team

    OpenAIRE

    Kahn, P. M.; Leon, G. R.

    2000-01-01

    This study focused on four female Antarctic expedition team members who successfully skied to the South Pole in 67 days but did not meet their original objective of traversing the continent. The three phases of data collection included (1) a preexpedition personality assessment, (b) daily self-ratings of mood, task effectiveness, stress, coping, and exertion, and (c) postexpedition interviews about stress and coping. Personality measures showed a group high in confidence and achievement and l...

  18. Antarctic 20th Century Accumulation Changes Based on Regional Climate Model Simulations

    Directory of Open Access Journals (Sweden)

    Klaus Dethloff

    2010-01-01

    investigated on the basis of ERA-40 data and HIRHAM simulations. It is shown that the regional accumulation changes are largely driven by changes in the transient activity around the Antarctic coasts due to the varying AAO phases. During positive AAO, more transient pressure systems travelling towards the continent, and Western Antarctica and parts of South-Eastern Antarctica gain more precipitation and mass. Over central Antarctica the prevailing anticyclone causes a strengthening of polar desertification connected with a reduced surface mass balance in the northern part of East Antarctica.

  19. Age, origin and evolution of Antarctic debris-covered glaciers: Implications for landscape evolution and long-term climate change

    Science.gov (United States)

    Mackay, Sean Leland

    Antarctic debris-covered glaciers are potential archives of long-term climate change. However, the geomorphic response of these systems to climate forcing is not well understood. To address this concern, I conducted a series of field-based and numerical modeling studies in the McMurdo Dry Valleys of Antarctica (MDV), with a focus on Mullins and Friedman glaciers. I used data and results from geophysical surveys, ice-core collection and analysis, geomorphic mapping, micro-meteorological stations, and numerical-process models to (1) determine the precise origin and distribution of englacial and supraglacial debris within these buried-ice systems, (2) quantify the fundamental processes and feedbacks that govern interactions among englacial and supraglacial debris, (3) establish a process-based model to quantify the inventory of cosmogenic nuclides within englacial and supraglacial debris, and (4) isolate the governing relationships between the evolution of englacial /supraglacial debris and regional climate forcing. Results from 93 field excavations, 21 ice cores, and 24 km of ground-penetrating radar data show that Mullins and Friedman glaciers contain vast areas of clean glacier ice interspersed with inclined layers of concentrated debris. The similarity in the pattern of englacial debris bands across both glaciers, along with model results that call for negligible basal entrainment, is best explained by episodic environmental change at valley headwalls. To constrain better the timing of debris-band formation, I developed a modeling framework that tracks the accumulation of cosmogenic 3He in englacial and supraglacial debris. Results imply that ice within Mullins Glacier increases in age non-linearly from 12 ka to ˜220 ka in areas of active flow (up to >> 1.6 Ma in areas of slow-moving-to-stagnant ice) and that englacial debris bands originate with a periodicity of ˜41 ka. Modeling studies suggest that debris bands originate in synchronicity with changes in

  20. 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.

  1. 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

  2. Infrared Thermal Signature Evaluation of a Pure and Saline Ice for Marine Operations in Cold Climate

    Directory of Open Access Journals (Sweden)

    Taimur Rashid

    2015-11-01

    Full Text Available Marine operations in cold climates are subjected to abundant ice accretion, which can lead to heavy ice loads over larger surface area. For safe and adequate operations on marine vessels over a larger area, remote ice detection and ice mitigation system can be useful. To study this remote ice detection option, lab experimentation was performed to detect the thermal gradient of ice with the infrared camera. Two different samples of ice blocks were prepared from tap water and saline water collected from the North Atlantic Ocean stream. The surfaces of ice samples were observed at room temperature. A complete thermal signature over the surface area was detected and recorded until the meltdown process was completed. Different temperature profiles for saline and pure ice samples were observed, which were kept under similar conditions. This article is focused to understand the experimentation methodology and thermal signatures of samples. However, challenges remains in terms of the validation of the detection signature and elimination of false detection.

  3. El Niño and the Antarctic During Recent Climatic Events

    Science.gov (United States)

    Kidwell, A. N.; Jo, Y. H.; Yan, X. H.

    2014-12-01

    The difference between eastern Pacific (EP) and central Pacific (CP) type El Niños has been noted in the tropical Pacific Ocean. During recent global warming hiatus, the Pacific Decadal Oscillations (PDO) switches to the negative phase while the CP El Niños occur more often than EP El Niños. The changes of El Niño type in conjunction with westward drift and increasing warm pool size shows an interesting multidecadal change in the warm pool (Kidwell et al, 2014). However, the effect of these variations in other regions is not fully explored. A comprehensive study of the El Niño /La Niña (EN/LN) events and their Antarctic teleconnections was conducted using multiple remote sensing and composite data sets. During the time period from April 2002-April 2011, the sea ice coverage, remotely sensed sea surface temperature (SST), outgoing longwave radiation (OLR) and continental water mass variations data were all collected and analyzed. The results show the different ways in which the variations in tropical SST and OLR associated with CP and EP El Niños cause regional changes in sea ice coverage around the continent of Antarctica as well as changes in continental water mass during six distinct El Niño events and three distinct La Niña events. The El Niño Southern Oscillation (ENSO) diversity and the Southern Ocean deep warming around the Antarctic during recent "Hiatus" will also be discussed.

  4. 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,...

  5. 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.

  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

    A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, 800,000 years ago. Experiments performed with an atmospheric general circulation model including wa...

  7. Satellite gravimetry observation of Antarctic snow accumulation related to ENSO

    OpenAIRE

    Ingo Sasgen; Henryk Dobslaw; Z. Martinec; Maik Thomas

    2010-01-01

    Interannual ice-mass variations along the Antarctic Peninsula (AP) and in the Amundsen Sea Sector (AS) are obtained for the years 2002 until 2009 using satellite data of the Gravity Recovery and Climate Experiment, that correlate well (r ≈ 0.7) with accumulation variations based on the net precipitation from the European Centre for Medium Range Weather Forecasts. Moreover, mass signals for AP and AS are anti-correlated in time (r ≈ − 0.4) and contain El Niño Southern Oscillation signatures re...

  8. 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.

  9. 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

  10. 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

  11. Stable isotopes and Antarctic moss banks: Plants and soil microbes respond to recent warming on the Antarctic Peninsula

    Science.gov (United States)

    Royles, Jessica; Amesbury, Matthew; Ogée, Jérôme; Wingate, Lisa; Convey, Peter; Hodgson, Dominic; Griffiths, Howard; Leng, Melanie; Charman, Dan

    2014-05-01

    The Antarctic Peninsula is one of the most rapidly warming regions on Earth, with air temperature increases of as much as 3°C recorded since the 1950s. However, the longer-term context of this change is limited and existing records, largely relying on ice core data, are not suitably located to be able to trace the spatial signature of change over time. We are working on a project exploiting stable isotope records preserved in moss peat banks spanning 10 degrees of latitude along the Antarctic Peninsula as an archive of late Holocene climate variability. Here we present a unique time series of past moss growth and soil microbial activity that has been produced from a 150 year old moss bank at Lazarev Bay, Alexander Island (69°S), a site at the southern limit of significant plant growth in the Antarctic Peninsula region. These moss banks are ideal archives for palaeoclimate research as they are well-preserved by freezing, generally monospecific, easily dated by radiocarbon techniques, and have sufficiently high accumulation rates to permit decadal resolution. We use accumulation rates, cellulose δ13C and fossil testate amoebae to show that growth rates, assimilation and microbial productivity rose rapidly in the 1960s, consistent with temperature change, although recently may have stalled, concurrent with other evidence. The increase in biological activity is unprecedented in the last 150 years. Along with work completed on Signy Island (60°S), in the South Orkney Islands, in which we used carbon isotope evidence to show recent climate-related enhancement of CO2 assimilation and peat accumulation rates in Antarctica, the observed relationships between moss growth, microbial activity and climate suggests that moss bank records have the potential to test the regional expression of temperature variability shown by instrumental data on the Antarctic Peninsula over centennial to millennial timescales, by providing long-term records of summer growth conditions

  12. 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.

  13. 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

  14. 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

  15. Maintenance of high HCl/Cly and NOx/NOy in the Antarctic vortex: A chemical signature of confinement during spring

    International Nuclear Information System (INIS)

    Michelsen, H. A.; Webster, C. R.; Manney, G. L.; Scott, D. C.; Margitan, J. J.; May, R. D.; Irion, F. W.; Gunson, M. R.; Russell, J. M. III; Spivakovsky, C. M.

    1999-01-01

    Observations made in the 1994 Antarctic vortex show that Cl y recovered completely into HCl following conversion of Cl y reservoir species to active radicals, and NO x constituted a 4-5 times higher fraction of NO y inside the vortex than outside. Measurements made in October and November from the Airborne Southern Hemisphere Ozone Expedition/Measurements of the Atmospheric Effects of Stratospheric Aircraft (ASHOE/MAESA) ER-2 aircraft mission, the third Atmospheric Laboratory for Applications and Science (ATLAS-3) space shuttle mission, and the Upper Atmosphere Research Satellite (UARS) demonstrate that this unusual partitioning of Cl y and NO y was maintained for at least 4 weeks in the springtime vortex. In response to severe ozone loss, abundances of HCl and NO x remained high despite temperatures low enough to reactivate Cl y and convert NO x to HNO 3 via heterogeneous processes. Thus, under severely ozone depleted conditions, high HCl and NO x abundances in the vortex are maintained until the vortex breaks up or an influx of ozone-rich extravortex air is entrained into the vortex. These observations suggest that the flux of extravortex air entering the core of the lower stratospheric vortex was small or negligible above ∼400 K during late spring, despite weakening of the vortex during this time period. Results of a photochemical model constrained by the measurements suggest that extravortex air entrained into the vortex during October and early November made up less than 5% of the vortex core air at 409 K. The model results also show that heterogeneous chemistry has little effect on the Cl y and NO y partitioning once high abundances of HCl have been attained under ozone depleted conditions, even when aerosol loading is high. (c) 1999 American Geophysical Union

  16. 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...

  17. Lead isotopic signatures in Antarctic marine sediment cores: A comparison between 1 M HCl partial extraction and HF total digestion pre-treatments for discerning anthropogenic inputs

    International Nuclear Information System (INIS)

    Townsend, A.T.; Snape, I.; Palmer, A.S.; Seen, A.J.

    2009-01-01

    Sensitive analytical techniques are typically required when dealing with samples from Antarctica as even low concentrations of contaminants can have detrimental environmental effects. Magnetic Sector ICP-MS is an ideal technique for environmental assessment as it offers high sensitivity, multi-element capability and the opportunity to determine isotope ratios. Here we consider the Pb isotope record of five marine sediment cores collected from three sites in the Windmill Islands area of East Antarctica: Brown Bay adjacent to the current Australian station Casey, Wilkes near the abandoned US/Australian Station and McGrady Cove lying midway between the two. Two sediment pre-treatment approaches were considered, namely partial extraction with 1 M HCl and total dissolution involving HF. Lead isotope ratio measurements made following sediment partial extraction provided a more sensitive indication of Pb contamination than either Pb concentrations alone (irrespective of sample pre-treatment method) or isotope ratios made after HF digestion, offering greater opportunity for discrimination between impacted and natural/geogenic samples and sites. Over 90% of the easily extractable Pb from sediments near Casey was anthropogenic in origin, consisting of Pb from major Australian deposits. At Wilkes impact from discarded batteries with a unique isotopic signature was found to be a key source of Pb contamination to the marine environment with ∼ 70-80% of Pb being anthropogenic in origin. The country and source of origin of these batteries remain unknown. Little evidence was found suggesting contamination at Wilkes by Pb originating from the major US source, Missouri. No definitive assessment could be made regarding Pb impact at McGrady Cove as the collected sediment core was of insufficient depth. Although Pb isotope ratio signatures may indicate anthropogenic input, spatial concentration gradients at nearby Brown Bay suggest contamination at McGrady Cove is unlikely. We

  18. 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

  19. Modelling the Antarctic Ice Sheet

    DEFF Research Database (Denmark)

    Pedersen, Jens Olaf Pepke; Holm, A.

    2015-01-01

    to sea level high stands during past interglacial periods. A number of AIS models have been developed and applied to try to understand the workings of the AIS and to form a robust basis for future projections of the AIS contribution to sea level change. The recent DCESS (Danish Center for Earth System......The Antarctic ice sheet is a major player in the Earth’s climate system and is by far the largest depository of fresh water on the planet. Ice stored in the Antarctic ice sheet (AIS) contains enough water to raise sea level by about 58 m, and ice loss from Antarctica contributed significantly...

  20. 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.

  1. Climate-induced signatures in the zooplankton communities: a meta-analysis at a European scale.

    Directory of Open Access Journals (Sweden)

    Sónia Cotrim Marques

    2014-05-01

    Full Text Available Several recent studies have revealed the impacts of the climate variability in the dynamic of zooplankton in different estuarine ecosystems, imposing a need for more and continued global studies. Presently, there is a growing appreciation in international collaborations to compare and contrast estuarine ecosystem response to climate variability across geographical gradients, including long-term changes in zooplankton. We performed a meta-analysis comprising field data from 7 location (Mondego estuary-Portugal, Seine estuary- France, Sheldt estuary- Belgium, Kiel fjord - Germany, Gulf of Riga- Latvia, Gulf of Bothnia – Sweden and Finland Archipelagos. The use of climatic modes (e.g. NAO, ENSO has proven useful in investigating links between climatic variations and ecological patterns. Therefore, the main focus will be to test the influence of the NAO on abundance of organisms, key species, local environment and whether these relationships are generally positive, whether they are sensitive to methodological differences among studies, between taxonomic group and key species. The knowledge gained will contribute to quantitatively evaluate the multi-scale structure of climate and marine environment and to identify a set of environmental indicators to assess the estuarine ecosystem state and risks for ecological shifts.

  2. Plants and soil microbes respond to recent warming on the Antarctic Peninsula

    Science.gov (United States)

    Amesbury, M. J.; Royles, J.; Hodgson, D.; Convey, P.; Griffiths, H.; Charman, D.

    2013-12-01

    The Antarctic Peninsula is one of the most rapidly warming regions on Earth, with temperature increases of as much as 3°C recorded since the 1950s. However, the longer-term context of this change is limited and existing records are not suitably located to be able to trace the spatial signature of change over time. This paper will present the first published results from a wider project exploiting peat moss banks spanning 10 degrees of latitude along the Antarctic Peninsula as an archive of late Holocene climate variability. These moss banks are ideal archives for palaeoclimate research as they are well-preserved by freezing, generally monospecific, easily dated by radiocarbon techniques and have sufficiently high accumulation rates to permit decadal resolution. A unique time series of past moss growth and soil microbial activity has been produced from a 150 year old moss bank at Lazarev Bay, Alexander Island, a site at the southern limit of significant plant growth in the Antarctic Peninsula region. We use accumulation rates, cellulose δ13C and fossil testate amoebae to provide an indication of ecosystem productivity. We show that both moss and microbial population growth rates rose rapidly in the 1960s, consistent with temperature change, although recently may have stalled, concurrent with other evidence. The increase in terrestrial plant growth rates and soil microbial activity is unprecedented in the last 150 years. The observed relationship between moss growth, microbial activity and climate at Lazarev Bay suggests that moss bank records have the potential to test the regional expression of temperature variability shown by instrumental data on the Antarctic Peninsula over centennial to millennial timescales, by providing long-term records of summer growth conditions, complementing the more distant and widely dispersed ice core records. As a result, we will conclude by placing the Lazarev Bay record into the wider context of the latest progress of analysis of

  3. 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.

    phytoplankton biomass during fall and winter is attributed to the iron-fertilization driven by enhanced dust-delivery under this regional climate shift. Finally, it is shown that the increased fish (oil-sardine) catch in the eastern and western Arabian Sea after...

  4. MECHANISMS FOR THE SEASONAL CYCLE IN THE ANTARCTIC COASTAL OCEANS

    OpenAIRE

    オオシマ; Kay I., OHSHIMA

    1996-01-01

    Seasonal variations of the Antarctic coastal oceans has not been well understood owing to logistical difficulties in observations, especially during the ice-covered season. Recently, 'Weddell Gyre Study' and 'Japanese Antarctic Climate Research program' have revealed the following seasonal variations in the Antarctic coastal ocean. First, the thickness of the Winter Water (WW) layer, characterized by cold, fresh, oxygen-rich water, exhibits its maximum in the austral fall and its minimum in t...

  5. 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.

  6. 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.

  7. Combined ice core and climate-model evidence for the collapse of the West Antarctic Ice Sheet during Marine Isotope Stage 5e.

    Science.gov (United States)

    Steig, Eric J.; Huybers, Kathleen; Singh, Hansi A.; Steiger, Nathan J.; Frierson, Dargan M. W.; Popp, Trevor; White, James W. C.

    2015-04-01

    It has been speculated that collapse of the West Antarctic Ice Sheet explains the very high eustatic sea level rise during the last interglacial period, marine isotope stage (MIS) 5e, but the evidence remains equivocal. Changes in atmospheric circulation resulting from a collapse of the West Antarctic Ice Sheet (WAIS) would have significant regional impacts that should be detectable in ice core records. We conducted simulations using general circulation models (GCMs) at varying levels of complexity: a gray-radiation aquaplanet moist GCM (GRaM), the slab ocean version of GFDL-AM2 (also as an aquaplanet), and the fully-coupled version of NCAR's CESM with realistic topography. In all the experiments, decreased elevation from the removal of the WAIS leads to greater cyclonic circulation over the West Antarctic region. This creates increased advection of relatively warm marine air from the Amundsen-Bellingshausen Seas towards the South Pole, and increased cold-air advection from the East Antarctic plateau towards the Ross Sea and coastal Marie Byrd Land. The result is anomalous warming in some areas of the East Antarctic interior, and significant cooling in Marie Byrd Land. Comparison of ice core records shows good agreement with the model predictions. In particular, isotope-paleotemperature records from ice cores in East Antarctica warmed more between the previous glacial period (MIS 6) and MIS 5e than coastal Marie Byrd Land. These results add substantial support to other evidence for WAIS collapse during the last interglacial period.

  8. Lichen flora around the Korean Antarctic Scientific Station, King George Island, Antarctic.

    Science.gov (United States)

    Kim, Ji Hee; Ahn, In-Young; Hong, Soon Gyu; Andreev, Mikhail; Lim, Kwang-Mi; Oh, Mi Jin; Koh, Young Jin; Hur, Jae-Seoun

    2006-10-01

    As part of the long-term monitoring projects on Antarctic terrestrial vegetation in relation to global climate change, a lichen floristical survey was conducted around the Korean Antarctic Station (King Sejong Station), which is located on Barton Peninsula, King George Island, in January and February of 2006. Two hundred and twenty-five lichen specimens were collected and sixty-two lichen species in 38 genera were identified by morphological characteristics, chemical constituents, TLC analysis and ITS nucleotide sequence analysis.

  9. Antarctic research today

    International Nuclear Information System (INIS)

    Hempel, G.

    1982-01-01

    With the appetite for living and dead natural resources, the political and economical interest concerning the Antarctic increases throughout the world. There are three interrelated main subjects accounting for the international interest: The shelf tectonic puzzle of the original continent of Gondwana, where the Antarctic is situated in the centre, between Australia, South Africa and South America, and the hopes concerning the existence of mineral resources under the ice of the Antarctic are based thereon. The Antarctic forms the biggest unified living space of the world. (orig.)

  10. Time series analysis of the Antarctic Circumpolar Wave via symbolic transfer entropy

    Science.gov (United States)

    Oh, Mingi; Kim, Sehyun; Lim, Kyuseong; Kim, Soo Yong

    2018-06-01

    An attempt to interpret a large-scale climate phenomenon in the Southern Ocean (SO), the Antarctic Circumpolar Wave (ACW), has been made using an information entropy method, symbolic transfer entropy (STE). Over the areas of 50-60∘S latitude belt, information flow for four climate variables, sea surface temperature (SST), sea-ice edge (SIE), sea level pressure (SLP) and meridional wind speed (MWS) is examined. We found a tendency that eastward flow of information is preferred only for oceanic variables, which is a main characteristic of the ACW, an eastward wave making a circuit around the Antarctica. Since the ACW is the coherent pattern in both ocean and atmosphere it is reasonable to infer that the tendency reflects the Antarctic Circumpolar Current (ACC) encircling the Antarctica, rather than an evidence of the ACW. We observed one common feature for all four variables, a strong information flow over the area of the eastern Pacific Ocean, which suggest a signature of El Nino Southern Oscillation (ENSO).

  11. Antarctic news clips, 1991

    Science.gov (United States)

    1991-08-01

    Published stories are presented that sample a year's news coverage of Antarctica. The intent is to provide the U.S. Antarctic Program participants with a digest of current issues as presented by a variety of writers and popular publications. The subject areas covered include the following: earth science; ice studies; stratospheric ozone; astrophysics; life science; operations; education; antarctic treaty issues; and tourism

  12. 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

  13. 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

  14. Coral Records of 20th Century Central Tropical Pacific SST and Salinity: Signatures of Natural and Anthropogenic Climate Change

    Science.gov (United States)

    Nurhati, I. S.; Cobb, K.; Di Lorenzo, E.

    2011-12-01

    Accurate forecasts of regional climate changes in many regions of the world largely depend on quantifying anthropogenic trends in tropical Pacific climate against its rich background of interannual to decadal-scale climate variability. However, the strong natural climate variability combined with limited instrumental climate datasets have obscured potential anthropogenic climate signals in the region. Here, we present coral-based sea-surface temperature (SST) and salinity proxy records over the 20th century (1898-1998) from the central tropical Pacific - a region sensitive to El Niño-Southern Oscillation (ENSO) whose variability strongly impacts the global climate. The SST and salinity proxy records are reconstructed via coral Sr/Ca and the oxygen isotopic composition of seawater (δ18Osw), respectively. On interannual (2-7yr) timescales, the SST proxy record tracks both eastern- and central-Pacific flavors of ENSO variability (R=0.65 and R=0.67, respectively). Interannual-scale salinity variability in our coral record highlights profound differences in precipitation and ocean advections during the two flavors of ENSO. On decadal (8yr-lowpassed) timescales, the central tropical Pacific SST and salinity proxy records are controlled by different sets of dynamics linked to the leading climate modes of North Pacific climate variability. Decadal-scale central tropical Pacific SST is highly correlated to the recently discovered North Pacific Gyre Oscillation (NPGO; R=-0.85), reflecting strong dynamical links between the central Pacific warming mode and extratropical decadal climate variability. Whereas decadal-scale salinity variations in the central tropical Pacific are significantly correlated with the Pacific Decadal Oscillation (PDO; R=0.54), providing a better understanding on low-frequency salinity variability in the region. Having characterized natural climate variability in this region, the coral record shows a +0.5°C warming trend throughout the last century

  15. 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

  16. 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.

  17. 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.

  18. Signature Balancing

    NARCIS (Netherlands)

    Noordkamp, H.W.; Brink, M. van den

    2006-01-01

    Signatures are an important part of the design of a ship. In an ideal situation, signatures must be as low as possible. However, due to budget constraints it is most unlikely to reach this ideal situation. The arising question is which levels of signatures are optimal given the different scenarios

  19. 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...

  20. 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.

  1. Spatial structures in the heat budget of the Antarctic Atmospheric Boundary Layer

    NARCIS (Netherlands)

    van der Berg, W.J.; van den Broeke, M.R.; van Meijgaard, E.

    2008-01-01

    Output from the regional climate model RACMO2/ANT is used to calculate the heat budget of the Antarctic atmospheric boundary layer (ABL). The main feature of the wintertime Antarctic ABL is a persistent temperature deficit compared to the free atmosphere. The magnitude of this deficit is controlled

  2. Biological invasions in the Antarctic: extent, impacts and implications.

    Science.gov (United States)

    Frenot, Yves; Chown, Steven L; Whinam, Jennie; Selkirk, Patricia M; Convey, Peter; Skotnicki, Mary; Bergstrom, Dana M

    2005-02-01

    Alien microbes, fungi, plants and animals occur on most of the sub-Antarctic islands and some parts of the Antarctic continent. These have arrived over approximately the last two centuries, coincident with human activity in the region. Introduction routes have varied, but are largely associated with movement of people and cargo in connection with industrial, national scientific program and tourist operations. The large majority of aliens are European in origin. They have both direct and indirect impacts on the functioning of species-poor Antarctic ecosystems, in particular including substantial loss of local biodiversity and changes to ecosystem processes. With rapid climate change occurring in some parts of Antarctica, elevated numbers of introductions and enhanced success of colonization by aliens are likely, with consequent increases in impacts on ecosystems. Mitigation measures that will substantially reduce the risk of introductions to Antarctica and the sub-Antarctic must focus on reducing propagule loads on humans, and their food, cargo, and transport vessels.

  3. 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

  4. 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.

  5. Diversification, evolution and sub-functionalization of 70kDa heat-shock proteins in two sister species of antarctic krill: differences in thermal habitats, responses and implications under climate change.

    Science.gov (United States)

    Cascella, Kévin; Jollivet, Didier; Papot, Claire; Léger, Nelly; Corre, Erwan; Ravaux, Juliette; Clark, Melody S; Toullec, Jean-Yves

    2015-01-01

    A comparative thermal tolerance study was undertaken on two sister species of Euphausiids (Antarctic krills) Euphausia superba and Euphausia crystallorophias. Both are essential components of the Southern Ocean ecosystem, but occupy distinct environmental geographical locations with slightly different temperature regimes. They therefore provide a useful model system for the investigation of adaptations to thermal tolerance. Initial CTmax studies showed that E. superba was slightly more thermotolerant than E. crystallorophias. Five Hsp70 mRNAs were characterized from the RNAseq data of both species and subsequent expression kinetics studies revealed notable differences in induction of each of the 5 orthologues between the two species, with E. crystallorophias reacting more rapidly than E. superba. Furthermore, analyses conducted to estimate the evolutionary rates and selection strengths acting on each gene tended to support the hypothesis that diversifying selection has contributed to the diversification of this gene family, and led to the selective relaxation on the inducible C form with its possible loss of function in the two krill species. The sensitivity of the epipelagic species E. crystallorophias to temperature variations and/or its adaptation to cold is enhanced when compared with its sister species, E. superba. These results indicate that ice krill could be the first of the two species to be impacted by the warming of coastal waters of the Austral ocean in the coming years due to climate change.

  6. 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.

  7. 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

  8. A new method to detect transitory signatures and local time/space variability structures in the climate system: the scale-dependent correlation analysis

    Science.gov (United States)

    Rodó, Xavier; Rodríguez-Arias, Miquel-Àngel

    2006-10-01

    The study of transitory signals and local variability structures in both/either time and space and their role as sources of climatic memory, is an important but often neglected topic in climate research despite its obvious importance and extensive coverage in the literature. Transitory signals arise either from non-linearities, in the climate system, transitory atmosphere-ocean couplings, and other processes in the climate system evolving after a critical threshold is crossed. These temporary interactions that, though intense, may not last long, can be responsible for a large amount of unexplained variability but are normally considered of limited relevance and often, discarded. With most of the current techniques at hand these typology of signatures are difficult to isolate because the low signal-to-noise ratio in midlatitudes, the limited recurrence of the transitory signals during a customary interval of data considered. Also, there is often a serious problem arising from the smoothing of local or transitory processes if statistical techniques are applied, that consider all the length of data available, rather than taking into account the size of the specific variability structure under investigation. Scale-dependent correlation (SDC) analysis is a new statistical method capable of highlighting the presence of transitory processes, these former being understood as temporary significant lag-dependent autocovariance in a single series, or covariance structures between two series. This approach, therefore, complements other approaches such as those resulting from the families of wavelet analysis, singular-spectrum analysis and recurrence plots. A main feature of SDC is its high-performance for short time series, its ability to characterize phase-relationships and thresholds in the bivariate domain. Ultimately, SDC helps tracking short-lagged relationships among processes that locally or temporarily couple and uncouple. The use of SDC is illustrated in the present

  9. 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

  10. On the mechanisms of late 20th century sea-surface temperature trends over the Antarctic Circumpolar Current

    Science.gov (United States)

    Kravtsov, Sergey; Kamenkovich, Igor; Hogg, Andrew M.; Peters, John M.

    2011-11-01

    The Antarctic Circumpolar Current (ACC), with its associated three-dimensional circulation, plays an important role in global climate. This study concentrates on surface signatures of recent climate change in the ACC region and on mechanisms that control this change. Examination of climate model simulations shows that they match the observed late 20th century sea-surface temperature (SST) trends averaged over this region quite well, despite underestimating the observed surface-wind increases. Such wind increases, however, are expected to lead to significant cooling of the region, contradicting the observed SST trends. Motivated by recent theories of the ACC response to variable wind and radiative forcing, the authors used two idealized models to assess contributions of various dynamical processes to the SST evolution in the region. In particular, a high-resolution channel model of the ACC responds to increasing winds by net surface ACC warming due to enhanced mesoscale turbulence and associated heat transports in the mixed layer. These fluxes, modeled, in a highly idealized fashion, via increased lateral surface mixing in a coarse-resolution hybrid climate model, substantially offset zonally non-uniform surface cooling due to air-sea flux and Ekman-transport anomalies. These results suggest that the combination of these opposing effects must be accounted for when estimating climate response to any external forcing in the ACC region.

  11. Cosmogenic nuclides constrain surface fluctuations of an East Antarctic outlet glacier since the Pliocene.

    OpenAIRE

    Jones, R.S.; Norton, K.P.; Mackintosh, A.N.; Anderson, J.T.H.; Kubik, P.; Vockenhuber, C.; Wittman, H.; Fink, D.; Wilson, G.S.; Golledge, N.R.; McKay, R.

    2017-01-01

    Understanding past changes in the Antarctic ice sheets provides insight into how they might respond to future climate warming. During the Pliocene and Pleistocene, geological data show that the East Antarctic Ice Sheet responded to glacial and interglacial cycles by remaining relatively stable in its interior, but oscillating at its marine-based margin. It is currently not clear how outlet glaciers, which connect the ice sheet interior to its margin, responded to these orbitally-paced climate...

  12. 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.

  13. A method for separating Antarctic postglacial rebound and ice mass balance using future ICESat Geoscience Laser Altimeter System, Gravity Recovery and Climate Experiment, and GPS satellite data

    OpenAIRE

    Velicogna, Isabella; Wahr, John

    2002-01-01

    Measurements of ice elevation from the Geoscience Laser Altimeter System (GLAS) aboard the Ice, Cloud, and Land Elevation Satellite can be combined with time-variable geoid measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to learn about ongoing changes in polar ice mass and viscoelastic rebound of the lithosphere under the ice sheet. We estimate the accuracy in recovering the spatially varying ice mass trend and postglacial rebound signals for Antarctica...

  14. 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

  15. Antarctic and Southern Ocean influences on Late Pliocene global cooling

    NARCIS (Netherlands)

    McKay, R.; Naish, T.; Carter, L.; Riesselman, C.; Dunbar, R.; Sjunneskog, C.; Winter, D.; Sangiorgi, F.; Warren, C.; Pagani, M.; Schouten, S.; Willmott, V.; Levy, R.; DeConto , R.M.; Powell, R.D.

    2012-01-01

    The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL

  16. 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.

  17. Antarctic aerosols - A review

    Science.gov (United States)

    Shaw, Glenn E.

    1988-02-01

    Tropospheric aerosols with the diameter range of half a micron reside in the atmosphere for tens of days and teleconnect Antarctica with other regions by transport that reaches planetary scales of distances; thus, the aerosol on the Antarctic ice represents 'memory modules' of events that took place at regions separated from Antarctica by tens of thousands of kilometers. In terms of aerosol mass, the aerosol species include insoluble crustal products (less than 5 percent), transported sea-salt residues (highly variable but averaging about 10 percent), Ni-rich meteoric material, and anomalously enriched material with an unknown origin. Most (70-90 percent by mass) of the aerosol over the Antarctic ice shield, however, is the 'natural acid sulfate aerosol', apparently deriving from biological processes taking place in the surrounding oceans.

  18. Antarctic Meteorite Newsletter

    Science.gov (United States)

    Lindstrom, Marilyn

    2000-01-01

    This newsletter contains something for everyone! It lists classifications of about 440 meteorites mostly from the 1997 and 1998 ANSMET (Antarctic Search for Meteorites) seasons. It also gives descriptions of about 45 meteorites of special petrologic type. These include 1 iron, 17 chondrites (7 CC, 1 EC, 9 OC) and 27 achondrites (25 HED, UR). Most notable are an acapoloite (GRA98028) and an olivine diogenite (GRA98108).

  19. Unveiling the Antarctic subglacial landscape.

    Science.gov (United States)

    Warner, Roland; Roberts, Jason

    2010-05-01

    revealed by this approach, and we advocate its consideration in future ice thickness data syntheses. REFERENCES Budd, W.F., and R.C. Warner, 1996. A computer scheme for rapid calculations of balance-flux distributions. Annals of Glaciology 23, 21-27. Bamber, J.L., J.L. Gomez Dans and J.A. Griggs, 2009. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data. Part I: Data and methods. The Cryosphere 3 (2), 101-111. Griggs, J.A., and J.L. Bamber, 2009. A new digital elevation model of Antarctica derived from combined radar and laser altimetry data. Part II: Validation and error estimates, The Cryosphere, 3(2), 113-123. Le Brocq, A.M., A.J. Payne and M.J. Siegert, 2006. West Antarctic balance calculations: Impact of flux-routing algorithm, smoothing algorithm and topography. Computers and Geosciences 23(10): 1780-1795. Lythe, M. B., D.G. Vaughan, and the BEDMAP Consortium 2001, BEDMAP: A new ice thickness and subglacial topographic model of Antarctica, J. of Geophys. Res., 106(B6),11,335-11,351. van de Berg, W.J., M.R. van den Broeke, C.H. Reijmer, and E. van Meijgaard, 2006. Reassessment of the Antarctic surface mass balance using calibrated output of a regional atmospheric climate model, J. Geophys. Res., 111, D11104,doi:10.1029/2005JD006495. Warner, R.C., and W.F. Budd, 2000. Derivation of ice thickness and bedrock topography in data-gap regions over Antarctica, Annals of Glaciology, 31, 191-197. Wright, A.P., M.J. Siegert, A.M. Le Brocq, and D.B. Gore, 2008. High sensitivity of subglacial hydrological pathways in Antarctica to small ice-sheet changes, Geophys. Res. Lett., 35, L17504, doi:10.1029/2008GL034937.

  20. 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.)

  1. Distribution and abundance of Antarctic krill (Euphausia superba) along the Antarctic Peninsula

    Science.gov (United States)

    Siegel, Volker; Reiss, Christian S.; Dietrich, Kimberly S.; Haraldsson, Matilda; Rohardt, Gerhard

    2013-07-01

    Net-based data on the abundance, distribution, and demographic patterns of Antarctic krill are quantified from a contemporaneous two ship survey of the Antarctic Peninsula during austral summer 2011. Two survey areas were sampled focussed on Marguerite Bay in the south, and the tip of the Antarctic Peninsula in the north. Data from 177 stations showed that the highest concentrations of krill were found in the southern sampling area. Differences between areas were associated with a few large catches of one year old krill found in anomalously warm and productive waters in Marguerite Bay, and small krill catches in the less-productive, offshore waters in the north. Estimated krill density across the survey area was 3.4 krill m-2, and was low compared to the long-term average of 45 krill m-2 for the Elephant Island area. Overall recruitment between the two survey regions was similar, but per capita recruitment was about 60% lower than historical mean recruitment levels measured at Elephant Island since the late 1970s. Demographic patterns showed small krill concentrated near the coast, and large krill concentrated offshore on the shelf and slope all along the survey area. The offshore distribution of adult krill was delineated by the warm (˜1 °C), low salinity (33.8) water at 30 m, suggesting that most krill were present shoreward of the southern boundary of Antarctic Circumpolar Current Front. Distributions of larvae indicated that three hotspot areas were important for the production of krill: slope areas outside Marguerite Bay and north of the South Shetland Islands, and near the coast around Antarctic Sound. Successful spawning, as inferred from larval abundance, was roughly coincident with the shelf break and not with inshore waters. Given the rapid changes in climate along the Antarctic Peninsula and the lower per capita recruitment observed in recent years, studies comparing and contrasting production, growth, and recruitment across the Peninsula will be

  2. 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)

  3. 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.

  4. 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.

  5. 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

  6. Revisiting Antarctic Ozone Depletion

    Science.gov (United States)

    Grooß, Jens-Uwe; Tritscher, Ines; Müller, Rolf

    2015-04-01

    Antarctic ozone depletion is known for almost three decades and it has been well settled that it is caused by chlorine catalysed ozone depletion inside the polar vortex. However, there are still some details, which need to be clarified. In particular, there is a current debate on the relative importance of liquid aerosol and crystalline NAT and ice particles for chlorine activation. Particles have a threefold impact on polar chlorine chemistry, temporary removal of HNO3 from the gas-phase (uptake), permanent removal of HNO3 from the atmosphere (denitrification), and chlorine activation through heterogeneous reactions. We have performed simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) employing a recently developed algorithm for saturation-dependent NAT nucleation for the Antarctic winters 2011 and 2012. The simulation results are compared with different satellite observations. With the help of these simulations, we investigate the role of the different processes responsible for chlorine activation and ozone depletion. Especially the sensitivity with respect to the particle type has been investigated. If temperatures are artificially forced to only allow cold binary liquid aerosol, the simulation still shows significant chlorine activation and ozone depletion. The results of the 3-D Chemical Transport Model CLaMS simulations differ from purely Lagrangian longtime trajectory box model simulations which indicates the importance of mixing processes.

  7. 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

  8. RADARSAT: The Antarctic Mapping Project

    Science.gov (United States)

    Jezek, Kenneth C.; Lindstrom, E. (Technical Monitor)

    2002-01-01

    The first Antarctic Imaging Campaign (AIC) occurred during the period September 9, 1997 through October 20, 1997. The AIC utilized the unique attributes of the Canadian RADARSAT-1 to acquire the first, high-resolution, synthetic aperture imagery covering the entire Antarctic Continent. Although the primary goal of the mission was the acquisition of image data, the nearly flawless execution of the mission enabled additional collections of exact repeat orbit data. These data, covering an extensive portion of the interior Antarctic, potentially are suitable for interferometric analysis of topography and surface velocity. This document summarizes the Project through completion with delivery of products to the NASA DAACs.

  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 The Southern Ocean is an important sink for heat and CO2 and is one of the world’s most productive regions. The unique absence of blocking continents allows the Antarctic Circumpolar Current (ACC) to connect all ocean basins (Atlantic, Pacific...

  10. Vigorous lateral export of the meltwater outflow from beneath an Antarctic ice shelf.

    Science.gov (United States)

    Garabato, Alberto C Naveira; Forryan, Alexander; Dutrieux, Pierre; Brannigan, Liam; Biddle, Louise C; Heywood, Karen J; Jenkins, Adrian; Firing, Yvonne L; Kimura, Satoshi

    2017-02-09

    The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change. The increased freshwater output from Antarctica is important in determining sea level rise, the fate of Antarctic sea ice and its effect on the Earth's albedo, ongoing changes in global deep-ocean ventilation, and the evolution of Southern Ocean ecosystems and carbon cycling. A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported meltwater. This is usually represented by climate-scale models as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the meltwater to be concentrated at deeper levels. Here we use observations of the turbulent properties of the meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the meltwater. We show that the initial ascent of the meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.

  11. 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.)

  12. Antarctic crabs: invasion or endurance?

    Directory of Open Access Journals (Sweden)

    Huw J Griffiths

    Full Text Available Recent scientific interest following the "discovery" of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This "invasion hypothesis" suggests that decapod crabs were driven out of Antarctica 40-15 million years ago and are only now returning as "warm" enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura, and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60 °S. All are restricted to waters warmer than 0 °C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW. Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day "crab invasion". We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the

  13. 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.

  14. Current and historical climate signatures to deconstructed tree species richness pattern in South America - doi: 10.4025/actascibiolsci.v35i2.14202

    Directory of Open Access Journals (Sweden)

    Daniel Paiva Silva

    2013-05-01

    Full Text Available The purpose of this study was to investigate the importance of present and historical climate as determinants of current species richness pattern of forestry trees in South America. The study predicted the distribution of 217 tree species using Maxent models, and calculated the potential species richness pattern, which was further deconstructed based on range sizes and modeled against current and historical climates predictors using Geographically Weighted Regressions (GWR analyses. The current climate explains more of the wide-ranging species richness patterns than that of the narrow-ranging species, while the historical climate explained an equally small amount of variance for both narrow-and-wide ranging tree species richness patterns. The richness deconstruction based on range size revealed that the influences of current and historical climate hypotheses underlying patterns in South American tree species richness differ from those found in the Northern Hemisphere. Notably, the historical climate appears to be an important determinant of richness only in regions with marked climate changes and proved Pleistocenic refuges, while the current climate predicts the species richness across those Neotropical regions, with non-evident refuges in the Last Glacial Maximum. Thus, this study's analyses show that these climate hypotheses are complementary to explain the South American tree species richness. Keywords: climate changes, glacial refuges, water-energy availability, GWR analysis, spatial non-stationarity

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. Climate

    International Nuclear Information System (INIS)

    Fellous, J.L.

    2005-02-01

    This book starts with a series of about 20 preconceived ideas about climate and climatic change and analyses each of them in the light of the present day knowledge. Using this approach, it makes a status of the reality of the climatic change, of its causes and of the measures to be implemented to limit its impacts and reduce its most harmful consequences. (J.S.)

  20. 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

  1. The ANDRILL programme: a new multinational initiative to investigate Antarctica's climatic and tectonic history from stratigraphic drilling

    Science.gov (United States)

    Naish, T.; Andrill Steering Committee

    2003-04-01

    ANDRILL is a multinational initiative to investigate Antarctica’s role in Cenozoic-Recent (65 million years ago to the present) climatic, glacial and tectonic change through the recovery of stratigraphic records from and around the Antarctic margin. The ANDRILL programme was initially conceived and promoted by scientists who led the successful Cape Roberts Project (CRP) and other interested parties. A key motivation of ANDRILL is that the role of the Antarctic cryosphere (ice sheets, ice shelves and sea ice) in the climate system is complex and very poorly understood. While, high-quality sedimentary archives of past ice sheet behaviour have recently be-come available from projects such as the Cape Roberts Project and the Ocean Drilling Program (Leg 188, Prydz Bay), unfortunately they are too few in number to allow a comprehensive understanding of the continents influence on global climate. ANDRILL will address this issue through drilling a targeted portfolio of sites initially in the McMurdo Sound region. Here the dynamic behaviour of the East and West Antarctic ice sheets, and the Ross Ice Shelf have left their signature in the thick Cenozoic sedimentary fills of the West Antarctic Rift system and flexural moat basins. The ANDRILL McMurdo Sound Portfolio, is an 8 to 9 year programme spanning from 2001 to 2010 of which geophysical and site survey scientific investigations are nearing completion and the drilling phase will soon begin. An ANDRILL consortium has been established comprising five countries : USA, Italy, Germany, UK and NZ. This paper will present the scientific objectives of the programme, discuss the current status and future plans.

  2. Low genetic diversity in Antarctic populations of the lichen-forming ascomycete Cetraria aculeata and its photobiont

    Directory of Open Access Journals (Sweden)

    Stephanie Domaschke

    2012-03-01

    Full Text Available Lichens, symbiotic associations of fungi (mycobionts and green algae or cyanobacteria (photobionts, are poikilohydric organisms that are particularly well adapted to withstand adverse environmental conditions. Terrestrial ecosystems of the Antarctic are therefore largely dominated by lichens. The effects of global climate change are especially pronounced in the maritime Antarctic and it may be assumed that the lichen vegetation will profoundly change in the future. The genetic diversity of populations is closely correlated to their ability to adapt to changing environmental conditions and to their future evolutionary potential. In this study, we present evidence for low genetic diversity in Antarctic mycobiont and photobiont populations of the widespread lichen Cetraria aculeata. We compared between 110 and 219 DNA sequences from each of three gene loci for each symbiont. A total of 222 individuals from three Antarctic and nine antiboreal, temperate and Arctic populations were investigated. The mycobiont diversity is highest in Arctic populations, while the photobionts are most diverse in temperate regions. Photobiont diversity decreases significantly towards the Antarctic but less markedly towards the Arctic, indicating that ecological factors play a minor role in determining the diversity of Antarctic photobiont populations. Richness estimators calculated for the four geographical regions suggest that the low genetic diversity of Antarctic populations is not a sampling artefact. Cetraria aculeata appears to have diversified in the Arctic and subsequently expanded its range into the Southern Hemisphere. The reduced genetic diversity in the Antarctic is most likely due to founder effects during long-distance colonization.

  3. 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.

  4. 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).

  5. Arctic and Antarctic Sea Ice Changes and Impacts (Invited)

    Science.gov (United States)

    Nghiem, S. V.

    2013-12-01

    The extent of springtime Arctic perennial sea ice, important to preconditioning summer melt and to polar sunrise photochemistry, continues its precipitous reduction in the last decade marked by a record low in 2012, as the Bromine, Ozone, and Mercury Experiment (BROMEX) was conducted around Barrow, Alaska, to investigate impacts of sea ice reduction on photochemical processes, transport, and distribution in the polar environment. In spring 2013, there was further loss of perennial sea ice, as it was not observed in the ocean region adjacent to the Alaskan north coast, where there was a stretch of perennial sea ice in 2012 in the Beaufort Sea and Chukchi Sea. In contrast to the rapid and extensive loss of sea ice in the Arctic, Antarctic sea ice has a trend of a slight increase in the past three decades. Given the significant variability in time and in space together with uncertainties in satellite observations, the increasing trend of Antarctic sea ice may arguably be considered as having a low confidence level; however, there was no overall reduction of Antarctic sea ice extent anywhere close to the decreasing rate of Arctic sea ice. There exist publications presenting various factors driving changes in Arctic and Antarctic sea ice. After a short review of these published factors, new observations and atmospheric, oceanic, hydrological, and geological mechanisms contributed to different behaviors of sea ice changes in the Arctic and Antarctic are presented. The contribution from of hydrologic factors may provide a linkage to and enhance thermal impacts from lower latitudes. While geological factors may affect the sensitivity of sea ice response to climate change, these factors can serve as the long-term memory in the system that should be exploited to improve future projections or predictions of sea ice changes. Furthermore, similarities and differences in chemical impacts of Arctic and Antarctic sea ice changes are discussed. Understanding sea ice changes and

  6. 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 unfavourable 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 Arabidopsis thaliana accessions from the Iberian Peninsula. Analyses of 1.88 million single nucleotide polymorphisms 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 supported an overall genome adaptation to temperature, with 9.4% of the genes showing significant associations. Furthermore, phenotypic genome-wide associations provided a catalogue of candidate genes underlying flowering time variation. Finally, comparison of environmental and phenotypic genome-wide associations identified known (Twin Sister of FT, FRIGIDA-like 1, and Casein Kinase II Beta chain 1) and new (Epithiospecifer Modifier 1 and Voltage-Dependent Anion Channel 5) 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. © 2018 John Wiley & Sons Ltd.

  7. 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.

  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 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. 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

  10. 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.

  11. 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.

  12. 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

  13. Signature-based User Authentication

    OpenAIRE

    Hámorník, Juraj

    2015-01-01

    This work aims on missing handwritten signature authentication in Windows. Result of this work is standalone software that allow users to log into Windows by writing signature. We focus on security of signature authentification and best overall user experience. We implemented signature authentification service that accept signature and return user access token if signature is genuine. Signature authentification is done by comparing given signature to signature patterns by their similarity. Si...

  14. 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.

  15. Electronic Signature Policy

    Science.gov (United States)

    Establishes the United States Environmental Protection Agency's approach to adopting electronic signature technology and best practices to ensure electronic signatures applied to official Agency documents are legally valid and enforceable

  16. Lesson 6: Signature Validation

    Science.gov (United States)

    Checklist items 13 through 17 are grouped under the Signature Validation Process, and represent CROMERR requirements that the system must satisfy as part of ensuring that electronic signatures it receives are valid.

  17. Exotic signatures from supersymmetry

    International Nuclear Information System (INIS)

    Hall, L.J.

    1989-08-01

    Minor changes to the standard supersymmetric model, such as soft flavor violation and R parity violation, cause large changes in the signatures. The origin of these changes and the resulting signatures are discussed. 15 refs., 7 figs., 2 tabs

  18. 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.

  19. 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.

  20. Air content and O2/N2 tuned chronologies on local insolation signatures in the Vostok ice core are similar

    Science.gov (United States)

    Lipenkov, V.; Raynaud, D.; Loutre, M.-F.; Duval, P.; Lemieux-Dudon, B.

    2009-04-01

    An accurate chronology of ice cores is needed for interpreting the paleoclimatic record and understanding the relation between insolation and climate. A new domain of research in this area has been initially stimulated by the work of M. Bender (2002) linking the record of O2/N2 ratio in the air trapped in the Vostok ice with the local insolation. More recently, it has been proposed that the long-term changes in air content, V, recorded in ice from the high Antarctic plateau is also dominantly imprinted by the local summer insolation (Raynaud et al., 2007). The present paper presents a new V record from Vostok, which is compared with the published Vostok O2/N2 record for the same period of time (150-400 ka BP) by using the same spectral analysis methods. The spectral differences between the two properties and the possible mechanisms linking them with insolation through the surface snow structure and the close-off processes are discussed. The main result of our study is that the two experimentally independent local insolation proxies lead to absolute (orbital) time scales, which agree together within a standard deviation of 0.6 ka. This result strongly adds credibility to the air content of ice and the O2 to N2 ratio of the air trapped in ice as equally reliable and complementary tools for accurate dating of existing and future deep ice cores. References: M. Bender, Orbital tuning chronology for the Vostok climate record supported by trapped gas composition, Earth and Planetary Science Letters 204(2002) 275-289. D. Raynaud, V. Lipenkov, B. Lemieux-Dudon, P. Duval, M.F. Loutre, N. Lhomme, The local insolation signature of air content in Antarctic ice: a new step toward an absolute dating of ice records, Earth and Planetary Science Letters 261(2007) 337-349.

  1. Blinding for unanticipated signatures

    NARCIS (Netherlands)

    D. Chaum (David)

    1987-01-01

    textabstractPreviously known blind signature systems require an amount of computation at least proportional to the number of signature types, and also that the number of such types be fixed in advance. These requirements are not practical in some applications. Here, a new blind signature technique

  2. Fair quantum blind signatures

    International Nuclear Information System (INIS)

    Tian-Yin, Wang; Qiao-Yan, Wen

    2010-01-01

    We present a new fair blind signature scheme based on the fundamental properties of quantum mechanics. In addition, we analyse the security of this scheme, and show that it is not possible to forge valid blind signatures. Moreover, comparisons between this scheme and public key blind signature schemes are also discussed. (general)

  3. 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

  4. 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.

  5. 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.)

  6. Real Traceable Signatures

    Science.gov (United States)

    Chow, Sherman S. M.

    Traceable signature scheme extends a group signature scheme with an enhanced anonymity management mechanism. The group manager can compute a tracing trapdoor which enables anyone to test if a signature is signed by a given misbehaving user, while the only way to do so for group signatures requires revealing the signer of all signatures. Nevertheless, it is not tracing in a strict sense. For all existing schemes, T tracing agents need to recollect all N' signatures ever produced and perform RN' “checks” for R revoked users. This involves a high volume of transfer and computations. Increasing T increases the degree of parallelism for tracing but also the probability of “missing” some signatures in case some of the agents are dishonest.

  7. 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

  8. 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...

  9. 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

  10. The Effect of Representing Bromine from VSLS on the Simulation and Evolution of Antarctic Ozone

    Science.gov (United States)

    Oman, Luke D.; Douglass, Anne R.; Salawitch, Ross J.; Canty, Timothy P.; Ziemke, Jerald R.; Manyin, Michael

    2016-01-01

    We use the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM), a contributor to both the 2010 and 2014 WMO Ozone Assessment Reports, to show that inclusion of 5 parts per trillion (ppt) of stratospheric bromine(Br(sub y)) from very short lived substances (VSLS) is responsible for about a decade delay in ozone hole recovery. These results partially explain the significantly later recovery of Antarctic ozone noted in the 2014 report, as bromine from VSLS was not included in the 2010 Assessment. We show multiple lines of evidence that simulations that account for VSLS Br(sub y) are in better agreement with both total column BrO and the seasonal evolution of Antarctic ozone reported by the Ozone Monitoring Instrument (OMI) on NASAs Aura satellite. In addition, the near zero ozone levels observed in the deep Antarctic lower stratospheric polar vortex are only reproduced in a simulation that includes this Br(sub y) source from VSLS.

  11. Pakistan and Antarctic research - an overview

    International Nuclear Information System (INIS)

    Rizvi, S.H.

    1993-01-01

    The paper describes the significance of Antarctica and the necessity of conducting scientific research for the understanding of the global environment and through various environmental processes operative in Antarctica. The paper presents a review of the Pakistan's activities and research interests in Antarctica focussing on the salient features of the Pakistan's Antarctic Research Programme and objectives. It summarises the significance of Antarctica, Antarctic Research and the interests of the world in Antarctica and international co-operation for Antarctic Research. The paper also highlights the philosophy of Antarctic Science and provides some guidelines for the development of Antarctic Research programmes for Pakistan and for the newcomers in Antarctica particularly for the developing countries. (author)

  12. What is the climate system able to do ‘on its own’?

    Directory of Open Access Journals (Sweden)

    Lennart Bengtsson

    2013-03-01

    Full Text Available The climate of the Earth, like planetary climates in general, is broadly controlled by solar irradiation, planetary albedo and emissivity as well as its rotation rate and distribution of land (with its orography and oceans. However, the majority of climate fluctuations that affect mankind are internal modes of the general circulation of the atmosphere and the oceans. Some of these modes, such as El Nino-Southern Oscillation (ENSO, are quasi-regular and have some longer-term predictive skill; others like the Arctic and Antarctic Oscillation are chaotic and generally unpredictable beyond a few weeks. Studies using general circulation models indicate that internal processes dominate the regional climate and that some like ENSO events have even distinct global signatures. This is one of the reasons why it is so difficult to separate internal climate processes from external ones caused, for example, by changes in greenhouse gases and solar irradiation. However, the accumulation of the warmest seasons during the latest two decades is lending strong support to the forcing of the greenhouse gases. As models are getting more comprehensive, they show a gradually broader range of internal processes including those on longer time scales, challenging the interpretation of the causes of past and present climate events further.

  13. 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

  14. 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.

  15. The Future of the United States Antarctic Program

    Science.gov (United States)

    Thom, J. E.; Weidner, G. A.; Lazzara, M. A.; Knuth, S. L.; Cassano, J. J.

    2009-04-01

    The last three decades have seen Antarctic surface meteorological observations augmented by an increasing number of automated weather stations (AWS). Since 1980, the University of Wisconsin-Madison has managed an expanding array of AWS in Antarctica that are funded through the United States' National Science Foundation. The AWS network began with six stations and has grown to approximately 60 stations. The majority of the AWS use a custom electronics package designed in the 1970s and modified over approximately 20 years. However, dramatic changes in the electronics industry have led the UW-Madison to transition its AWS to commercial-off-the-shelf (COTS) components capable of integrating on-station storage, varied sensors, multiple data telemetry options, and a flexible operating system. Among the important technical issues arising from adopting a COTS-based AWS system are limited temperature certification for Antarctic conditions; non-standard integration of the varied telecommunications equipment; potentially inflexible data acquisition schemes; and frequent product upgrades, changes, and obsolescence. The UW-Madison presents the current status of its AWS system; its recent experience with new data loggers, sensors, and communication options; and its attempts to obtain a standardized AWS. The intent is to encourage the development of a forum where groups can document their experiences with varied AWS systems in the extreme polar climate. Recent events have added another challenge within the United States Antarctic Program, as it has become clear that budgetary and logistic limitations will drastically impact the AWS program. With logistical costs playing a bigger factor in funding AWS operations, international coordination and cooperation will be important in deploying and maintaining the AWS networks (such as GCOS) that are critical to monitoring the world's climate.

  16. [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.

  17. 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

  18. Satellite gravity gradient views help reveal the Antarctic lithosphere

    Science.gov (United States)

    Ferraccioli, F.; Ebbing, J.; Pappa, F.; Kern, M.; Forsberg, R.

    2017-12-01

    Here we present and analyse satellite gravity gradient signatures derived from GOCE and superimpose these on tectonic and bedrock topography elements, as well as seismically-derived estimates of crustal thickness for the Antarctic continent. The GIU satellite gravity component images the contrast between the thinner crust and lithosphere underlying the West Antarctic Rift System and the Weddell Sea Rift System and the thicker lithosphere of East Antarctica. The new images also suggest that more distributed wide-mode lithospheric and crustal extension affects both the Ross Sea Embayment and the less well known Ross Ice Shelf segment of the rift system. However, this pattern is less clear towards the Bellingshousen Embayment, indicating that the rift system narrows towards the southern edge of the Antarctic Peninsula. In East Antarctica, the satellite gravity data provides new views into the Archean to Mesoproterozoic Terre Adelie Craton, and clearly shows the contrast wrt to the crust and lithosphere underlying both the Wilkes Subglacial Basin to the east and the Sabrina Subglacial Basin to the west. This finding augments recent interpretations of aeromagnetic and airborne gravity data over the region, suggesting that the Mawson Continent is a composite lithospheric-scale entity, which was affected by several Paleoproterozoic and Mesoproterozoic orogenic events. Thick crust is imaged beneath the Transantarctic Mountains, the Terre Adelie Craton, the Gamburtsev Subglacial Mountains and also Eastern Dronning Maud Land, in particular beneath the recently proposed region of the Tonian Oceanic Arc Superterrane. The GIA and GIU components help delineate the edges of several of these lithospheric provinces. One of the most prominent lithospheric-scale features discovered in East Antarctica from satellite gravity gradient imaging is the Trans East Antarctic Shear Zone that separates the Gamburtsev Province from the Eastern Dronning Maud Land Province and appears to form the

  19. Reconciling projections of the Antarctic contribution to sea level rise

    Science.gov (United States)

    Edwards, Tamsin; Holden, Philip; Edwards, Neil; Wernecke, Andreas

    2017-04-01

    Two recent studies of the Antarctic contribution to sea level rise this century had best estimates that differed by an order of magnitude (around 10 cm and 1 m by 2100). The first, Ritz et al. (2015), used a model calibrated with satellite data, giving a 5% probability of exceeding 30cm by 2100 for sea level rise due to Antarctic instability. The second, DeConto and Pollard (2016), used a model evaluated with reconstructions of palaeo-sea level. They did not estimate probabilities, but using a simple assumption here about the distribution shape gives up to a 5% chance of Antarctic contribution exceeding 2.3 m this century with total sea level rise approaching 3 m. If robust, this would have very substantial implications for global adaptation to climate change. How are we to make sense of this apparent inconsistency? How much is down to the data - does the past tell us we will face widespread and rapid Antarctic ice losses in the future? How much is due to the mechanism of rapid ice loss ('cliff failure') proposed in the latter paper, or other parameterisation choices in these low resolution models (GRISLI and PISM, respectively)? How much is due to choices made in the ensemble design and calibration? How do these projections compare with high resolution, grounding line resolving models such as BISICLES? Could we reduce the huge uncertainties in the palaeo-study? Emulation provides a powerful tool for understanding these questions and reconciling the projections. By describing the three numerical ice sheet models with statistical models, we can re-analyse the ensembles and re-do the calibrations under a common statistical framework. This reduces uncertainty in the PISM study because it allows massive sampling of the parameter space, which reduces the sensitivity to reconstructed palaeo-sea level values and also narrows the probability intervals because the simple assumption about distribution shape above is no longer needed. We present reconciled probabilistic

  20. 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.

  1. Sulfur Speciation in Peat: a Time-zero Signature for the " Spruce and Peatland Responses Under Climate and Environmental Change" Experiment

    Science.gov (United States)

    Furman, O.; Toner, B. M.; Sebestyen, S. D.; Kolka, R. K.; Nater, E. A.

    2014-12-01

    As part of the "Spruce and Peatland Responses Under Climate and Environmental Change" (SPRUCE) experiment, we made initial measurements of sulfur speciation in peat. These observations represent a "time-zero" relative to the intended soil warming experiment which begins in 2015. Total sulfur and sulfur speciation were measured in peat cores (solid phase) from nine plots (hollows and hummocks) to a depth of 2 m. Peat samples were packed under nitrogen and frozen in the field immediately after collection. All subsequent sample storage, handling, and processing were conducted under inert gas. Sulfur speciation was measured using bulk sulfur 1s X-ray absorption near edge structure (XANES) spectroscopy at the SXRMB instrument at the Canadian Light Source, Saskatoon, SK, Canada and at the 9-BM instrument, Advanced Photon Source, Argonne National Laboratory, IL, USA. Total sulfur concentrations ranged from 968 to 4077 mg sulfur / kg dry peat. Sulfur content increased with depth from 2 g sulfur / m2 in the 0-10 cm increment to a maximum value of 38 g sulfur / m2 in the 50-60 cm increment. These sulfur loadings produced high quality XANES spectra. The nine cores exhibited reproducible trends with depth in both total sulfur and specific sulfur species; however, variability in sulfur speciation was greatest in the top 40 cm. All sulfur detected within the peat solids was in an organic form. The most abundant sulfur species group was composed of organic mono-sulfide and thiol forms, representing approximately half of the total sulfur at all depths. Sulfonate and ester-sulfate species were 10-15 mol% of sulfur and exhibited low variability with depth. A subsurface maximum in organic di-sulfide was observed in the 20-30 cm depth increment, which is the transition zone between transiently oxidized acrotelm and permanently saturated anaerobic catotelm. Quantification of major sulfur pools is important for the SPRUCE experiment as they are likely to be indicators of changes in the

  2. 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.

  3. 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...

  4. 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.

  5. Chilean Antarctic Stations on King George Island

    OpenAIRE

    Katsutada Kaminuma

    2000-01-01

    The purpose of my visit to Chilean Antarctic Stations was to assess the present status of geophysical observations and research, as the South Shetland Island, West Antarctica, where the stations are located, are one of the most active tectonic regions on the Antarctic plate. The Instituto Antartico Chileno (INACH) kindly gave me a chance to stay in Frei/Escudero Bases as an exchange scientist under the Antarctic Treaty for two weeks in January 2000. I stayed in Frei Base as a member of a geol...

  6. 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.

  7. Constraining the Antarctic contribution to interglacial sea-level rise

    Science.gov (United States)

    Naish, T.; Mckay, R. M.; Barrett, P. J.; Levy, R. H.; Golledge, N. R.; Deconto, R. M.; Horgan, H. J.; Dunbar, G. B.

    2015-12-01

    Observations, models and paleoclimate reconstructions suggest that Antarctica's marine-based ice sheets behave in an unstable manner with episodes of rapid retreat in response to warming climate. Understanding the processes involved in this "marine ice sheet instability" is key for improving estimates of Antarctic ice sheet contribution to future sea-level rise. Another motivating factor is that far-field sea-level reconstructions and ice sheet models imply global mean sea level (GMSL) was up to 20m and 10m higher, respectively, compared with present day, during the interglacials of the warm Pliocene (~4-3Ma) and Late Pleistocene (at ~400ka and 125ka). This was when atmospheric CO2 was between 280 and 400ppm and global average surface temperatures were 1- 3°C warmer, suggesting polar ice sheets are highly sensitive to relatively modest increases in climate forcing. Such magnitudes of GMSL rise not only require near complete melt of the Greenland Ice Sheet and the West Antarctic Ice Sheet, but a substantial retreat of marine-based sectors of East Antarctic Ice Sheet. Recent geological drilling initiatives on the continental margin of Antarctica from both ship- (e.g. IODP; International Ocean Discovery Program) and ice-based (e.g. ANDRILL/Antarctic Geological Drilling) platforms have provided evidence supporting retreat of marine-based ice. However, without direct access through the ice sheet to archives preserved within sub-glacial sedimentary basins, the volume and extent of ice sheet retreat during past interglacials cannot be directly constrained. Sediment cores have been successfully recovered from beneath ice shelves by the ANDRILL Program and ice streams by the WISSARD (Whillans Ice Stream Sub-glacial Access Research Drilling) Project. Together with the potential of the new RAID (Rapid Access Ice Drill) initiative, these demonstrate the technological feasibility of accessing the subglacial bed and deeper sedimentary archives. In this talk I will outline the

  8. 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

  9. Simulating a Dynamic Antarctic Ice Sheet in the Early to Middle Miocene

    Science.gov (United States)

    Gasson, E.; DeConto, R.; Pollard, D.; Levy, R. H.

    2015-12-01

    There are a variety of sources of geological data that suggest major variations in the volume and extent of the Antarctic ice sheet during the early to middle Miocene. Simulating such variability using coupled climate-ice sheet models is problematic due to a strong hysteresis effect caused by height-mass balance feedback and albedo feedback. This results in limited retreat of the ice sheet once it has reached the continental size, as likely occurred prior to the Miocene. Proxy records suggest a relatively narrow range of atmospheric CO2 during the early to middle Miocene, which exacerbates this problem. We use a new climate forcing which accounts for ice sheet-climate feedbacks through an asynchronous GCM-RCM coupling, which is able to better resolve the narrow Antarctic ablation zone in warm climate simulations. When combined with recently suggested mechanisms for retreat into subglacial basins due to ice shelf hydrofracture and ice cliff failure, we are able to simulate large-scale variability of the Antarctic ice sheet in the Miocene. This variability is equivalent to a seawater oxygen isotope signal of ~0.5 ‰, or a sea level equivalent change of ~35 m, for a range of atmospheric CO2 between 280 - 500 ppm.

  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. 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.

  12. 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.

  13. Gravity Maps of Antarctic Lithospheric Structure from Remote-Sensing and Seismic Data

    Science.gov (United States)

    Tenzer, Robert; Chen, Wenjin; Baranov, Alexey; Bagherbandi, Mohammad

    2018-02-01

    Remote-sensing data from altimetry and gravity satellite missions combined with seismic information have been used to investigate the Earth's interior, particularly focusing on the lithospheric structure. In this study, we use the subglacial bedrock relief BEDMAP2, the global gravitational model GOCO05S, and the ETOPO1 topographic/bathymetric data, together with a newly developed (continental-scale) seismic crustal model for Antarctica to compile the free-air, Bouguer, and mantle gravity maps over this continent and surrounding oceanic areas. We then use these gravity maps to interpret the Antarctic crustal and uppermost mantle structure. We demonstrate that most of the gravity features seen in gravity maps could be explained by known lithospheric structures. The Bouguer gravity map reveals a contrast between the oceanic and continental crust which marks the extension of the Antarctic continental margins. The isostatic signature in this gravity map confirms deep and compact orogenic roots under the Gamburtsev Subglacial Mountains and more complex orogenic structures under Dronning Maud Land in East Antarctica. Whereas the Bouguer gravity map exhibits features which are closely spatially correlated with the crustal thickness, the mantle gravity map reveals mainly the gravitational signature of the uppermost mantle, which is superposed over a weaker (long-wavelength) signature of density heterogeneities distributed deeper in the mantle. In contrast to a relatively complex and segmented uppermost mantle structure of West Antarctica, the mantle gravity map confirmed a more uniform structure of the East Antarctic Craton. The most pronounced features in this gravity map are divergent tectonic margins along mid-oceanic ridges and continental rifts. Gravity lows at these locations indicate that a broad region of the West Antarctic Rift System continuously extends between the Atlantic-Indian and Pacific-Antarctic mid-oceanic ridges and it is possibly formed by two major

  14. Monitoring of Antarctic moss ecosystems using a high spatial resolution imaging spectroscopy

    Science.gov (United States)

    Malenovsky, Zbynek; Lucieer, Arko; Robinson, Sharon; Harwin, Stephen; Turner, Darren; Veness, Tony

    2013-04-01

    The most abundant photosynthetically active plants growing along the rocky Antarctic shore are mosses of three species: Schistidium antarctici, Ceratodon purpureus, and Bryum pseudotriquetrum. Even though mosses are well adapted to the extreme climate conditions, their existence in Antarctica depends strongly on availability of liquid water from snowmelt during the short summer season. Recent changes in temperature, wind speed and stratospheric ozone are stimulating faster evaporation, which in turn influences moss growing rate, health state and abundance. This makes them an ideal bio-indicator of the Antarctic climate change. Very short growing season, lasting only about three months, requires a time efficient, easily deployable and spatially resolved method for monitoring the Antarctic moss beds. Ground and/or low-altitude airborne imaging spectroscopy (called also hyperspectral remote sensing) offers a fast and spatially explicit approach to investigate an actual spatial extent and physiological state of moss turfs. A dataset of ground-based spectral images was acquired with a mini-Hyperspec imaging spectrometer (Headwall Inc., the USA) during the Antarctic summer 2012 in the surroundings of the Australian Antarctic station Casey (Windmill Islands). The collection of high spatial resolution spectral images, with pixels about 2 cm in size containing from 162 up to 324 narrow spectral bands of wavelengths between 399 and 998 nm, was accompanied with point moss reflectance measurements recorded with the ASD HandHeld-2 spectroradiometer (Analytical Spectral Devices Inc., the USA). The first spectral analysis indicates significant differences in red-edge and near-infrared reflectance of differently watered moss patches. Contrary to high plants, where the Normalized Difference Vegetation Index (NDVI) represents an estimate of green biomass, NDVI of mosses indicates mainly the actual water content. Similarly to high plants, reflectance of visible wavelengths is

  15. 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...

  16. 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...

  17. 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.

  18. Reflectance of Antarctic surfaces from multispectral radiometers: The correction of atmospheric effects

    International Nuclear Information System (INIS)

    Zibordi, G.; Maracci, G.

    1993-01-01

    Monitoring reflectance of polar icecaps has relevance in climate studies. In fact, climate changes produce variations in the morphology of ice and snow covers, which are detectable as surface reflectance change. Surface reflectance can be retrieved from remotely sensed data. However, absolute values independent of atmospheric turbidity and surface altitude can only be obtained after removing masking effects of the atmosphere. An atmospheric correction model, accounting for surface and sensor altitudes above sea level, is described and validated through data detected over Antarctic surfaces with a Barnes Modular Multispectral Radiometer having bands overlapping those of the Landsat Thematic Mapper. The model is also applied in a sensitivity analysis to investigate error induced in reflectance obtained from satellite data by indeterminacy in optical parameters of atmospheric constituents. Results show that indeterminacy in the atmospheric water vapor optical thickness is the main source of nonaccuracy in the retrieval of surface reflectance from data remotely sensed over Antarctic regions

  19. 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).

  20. 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.

  1. Changes in glacier dynamics in the northern Antarctic Peninsula since 1985

    Science.gov (United States)

    Seehaus, Thorsten; Cook, Alison J.; Silva, Aline B.; Braun, Matthias

    2018-02-01

    The climatic conditions along the northern Antarctic Peninsula have shown significant changes within the last 50 years. Here we present a comprehensive analysis of temporally and spatially detailed observations of the changes in ice dynamics along both the east and west coastlines of the northern Antarctic Peninsula. Temporal evolutions of glacier area (1985-2015) and ice surface velocity (1992-2014) are derived from a broad multi-mission remote sensing database for 74 glacier basins on the northern Antarctic Peninsula ( disintegration showed the largest retreat by 208.59 km2. Glaciers on the east coast north of the former Prince Gustav Ice Shelf extent in 1986 receded by only 21.07 km2 (1985-2015) and decelerated by about 58 % on average (1992-2014). A dramatic acceleration after ice shelf disintegration with a subsequent deceleration is observed at most former ice shelf tributaries on the east coast, combined with a significant frontal retreat. In 2014, the flow speed of the former ice shelf tributaries was 26 % higher than before 1996. Along the west coast the average flow speeds of the glaciers increased by 41 %. However, the glaciers on the western Antarctic Peninsula revealed a strong spatial variability of the changes in ice dynamics. By applying a hierarchical cluster analysis, we show that this is associated with the geometric parameters of the individual glacier basins (hypsometric indexes, maximum surface elevation of the basin, flux gate to catchment size ratio). The heterogeneous spatial pattern of ice dynamic evolutions at the northern Antarctic Peninsula shows that temporally and spatially detailed observations as well as further monitoring are necessary to fully understand glacier change in regions with such strong topographic and climatic variances.

  2. 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...

  3. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013

    OpenAIRE

    Seo, Ki-Weon; Wilson, Clark R.; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E.; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-01-01

    Abstract Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE?derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by ...

  4. West Antarctic Ice Sheet collapse – the fall and rise of a paradigm

    OpenAIRE

    Vaughan, David G.

    2008-01-01

    It is now almost 30 years since John Mercer (1978) first presented the idea that climate change could eventually cause a rapid deglaciation, or “collapse”, of a large part of the West Antarctic ice sheet (WAIS), raising world sea levels by 5 metres and causing untold economic and social impacts. This idea, apparently simple and scientifically plausible, created a vision of the future, sufficiently alarming that it became a paradigm for a generation of researchers and provided an icon for the ...

  5. 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.

  6. Antarctic Peninsula mass balance at present-day and over the past 150 years employing constraints from GRACE, GPS and other data

    Science.gov (United States)

    Ivins, E. R.; Wiese, D. N.; Watkins, M. M.; Landerer, F. W.; Simms, A.; Yuan, D.; Boening, C.

    2013-12-01

    Warming on the Antarctic Peninsula (AP) land mass and adjacent islands has been ocurring for more than 100 years. The rate of warming is at the extreme end of all Earth observations: during the 2nd half of the 20th century the rate is 3.5°C per century and has a dramatic effect of glaciers: west coast glaciers show diminishing outlet heights at a rate of 0.28 × 0.03 m/yr since the mid-1960s (Kunz et al., 2012). Since the late 1980's, notably on the northeastern edge of the AP, many of the outlet glaciers have experienced the loss of ice shelf buttressing forces that retard the outlet flow velocity (e.g., Berthier et al., 2012). The loss of these buttressing forces has caused outlet glaciers to speed up. It is clear from ice core and in situ records that the AP snow accumulation has also been increasing. While there is growing confidence that all space borne data are consistent with a net mass loss of the Antarctic Peninsula since 1990, there is relatively little convergence on the total mass loss, and its temporal variability, other than that measured by the Gravity Recovery and Climate Experiment (GRACE). Employing JPL mascon analyses, Ivins et al. (2011) employed 6.25 years of GRACE data, glacial isostatic adjustment (GIA) modeling with GPS data, to determine the mass trend of Graham Land (north of 67° S) at -32 × 6 Gt/yr and -9.5 × 3 Gt/yr for the remainder of the AP (74° S - 67° S). Neither region exhibited any significant non-secular signatures during 2003-2009.25. However, some outlet glaciers have shown both height and velocity changes over the period 2002-2012 that indicate increasing rates of loss - via laser altimetry and InSAR measurements (Anya Wendt, personal communication, 2012). In a combined examination of AP mass balance (with a slightly larger area for AP definition), recent work extended to mid 2013, indicates that the region of the Antarctic Peninsula has a loss rate of about -32.5 × 12 Gt/yr, with distinct and significant speed-up after

  7. Snow surface microbiome on the High Antarctic Plateau (DOME C).

    Science.gov (United States)

    Michaud, Luigi; Lo Giudice, Angelina; Mysara, Mohamed; Monsieurs, Pieter; Raffa, Carmela; Leys, Natalie; Amalfitano, Stefano; Van Houdt, Rob

    2014-01-01

    The cryosphere is an integral part of the global climate system and one of the major habitable ecosystems of Earth's biosphere. These permanently frozen environments harbor diverse, viable and metabolically active microbial populations that represent almost all the major phylogenetic groups. In this study, we investigated the microbial diversity in the surface snow surrounding the Concordia Research Station on the High Antarctic Plateau through a polyphasic approach, including direct prokaryotic quantification by flow cytometry and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH), and phylogenetic identification by 16S RNA gene clone library sequencing and 454 16S amplicon pyrosequencing. Although the microbial abundance was low (<10(3) cells/ml of snowmelt), concordant results were obtained with the different techniques. The microbial community was mainly composed of members of the Alpha-proteobacteria class (e.g. Kiloniellaceae and Rhodobacteraceae), which is one of the most well-represented bacterial groups in marine habitats, Bacteroidetes (e.g. Cryomorphaceae and Flavobacteriaceae) and Cyanobacteria. Based on our results, polar microorganisms could not only be considered as deposited airborne particles, but as an active component of the snowpack ecology of the High Antarctic Plateau.

  8. Snow surface microbiome on the High Antarctic Plateau (DOME C.

    Directory of Open Access Journals (Sweden)

    Luigi Michaud

    Full Text Available The cryosphere is an integral part of the global climate system and one of the major habitable ecosystems of Earth's biosphere. These permanently frozen environments harbor diverse, viable and metabolically active microbial populations that represent almost all the major phylogenetic groups. In this study, we investigated the microbial diversity in the surface snow surrounding the Concordia Research Station on the High Antarctic Plateau through a polyphasic approach, including direct prokaryotic quantification by flow cytometry and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH, and phylogenetic identification by 16S RNA gene clone library sequencing and 454 16S amplicon pyrosequencing. Although the microbial abundance was low (<10(3 cells/ml of snowmelt, concordant results were obtained with the different techniques. The microbial community was mainly composed of members of the Alpha-proteobacteria class (e.g. Kiloniellaceae and Rhodobacteraceae, which is one of the most well-represented bacterial groups in marine habitats, Bacteroidetes (e.g. Cryomorphaceae and Flavobacteriaceae and Cyanobacteria. Based on our results, polar microorganisms could not only be considered as deposited airborne particles, but as an active component of the snowpack ecology of the High Antarctic Plateau.

  9. Recent Aeromagnetic Anomaly views of the Antarctic continent

    Science.gov (United States)

    Ferraccioli, F.

    2012-04-01

    Antarctica is a keystone within the Gondwana and Rodinia supercontinents. However, despite intense geological research along the coastal fringes of Antarctica, the interior of the continent remains one of the most poorly understood regions on Earth. Aeromagnetic investigations are a useful tool to help disclose the structure and the evolution of continents from the Precambrian to the Cenozoic and Antarctica is no exception. Here I review a variety of aeromagnetic studies in East and West Antarctica performed since the completion of the first generation ADMAP -Antarctic Digital Magnetic Anomaly Project- in 2001. In western Dronning Maud, in East Antarctica, aeromagnetic data help delineate the extent of the Jurassic Jutulstraumen subglacial rift that is flanked by remnants of a Grenvillian-age (ca 1.1. Ga) igneous province and magmatic arc. Different magnetic signatures appear to characterize the Coats Land block but reconnaissance surveys are insufficient to fully delineate the extent and significance of the Coats Land block, a possible tectonic tracer of Laurentia within Rodinia (Loewy et al., 2011). Further in the interior of East Antarctica, a mosaic of distinct and hitherto largely unknown Precambrian provinces has recently been revealed by combining aeromagnetic and satellite magnetic data with models of crustal thickness constrained by gravity modeling and seismology (Ferraccioli et al., 2011, Nature). A major collisional suture may lie between the Archean Ruker Province and an inferred Proterozoic Gamburtsev Province but the age of final assembly of central East Antarctica remains uncertain and controversial. I favour a Grenville-age collisional event (linked to Rodinia assembly) or possibly older Paleoproteroic collision, followed by intraplate reactivation, as opposed to Neoproterozoic or Early Cambrian collision linked to East-West Gondwana assembly (Boger, 2011). New aerogeophysical surveys over Prince Elizabeth and Queen Mary Land could test this

  10. 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,...

  11. THE ELECTRONIC SIGNATURE

    Directory of Open Access Journals (Sweden)

    Voiculescu Madalina Irena

    2009-05-01

    Full Text Available Article refers to significance and the digital signature in electronic commerce. Internet and electronic commerce open up many new opportunities for the consumer, yet, the security (or perceived lack of security of exchanging personal and financial data

  12. Digital signature feasibility study

    Science.gov (United States)

    2008-06-01

    The purpose of this study was to assess the advantages and disadvantages of using digital signatures to assist the Arizona Department of Transportation in conducting business. The Department is evaluating the potential of performing more electronic t...

  13. Physics Signatures at CLIC

    CERN Document Server

    Battaglia, Marco

    2001-01-01

    A set of signatures for physics processes of potential interests for the CLIC programme at = 1 - 5 TeV are discussed. These signatures, that may correspond to the manifestation of different scenarios of new physics as well as to Standard Model precision tests, are proposed as benchmarks for the optimisation of the CLIC accelerator parameters and for a first definition of the required detector response.

  14. Combined ground-based and satellite remote sensing of atmospheric aerosol and Earth surface in the Antarctic

    Science.gov (United States)

    Chaikovsky, Anatoli; Korol, Michail; Malinka, A.; Zege, E.; Katsev, I.; Prikhach, A.; Denisov, S.; Dick, V.; Goloub, P.; Blarel, L.; Chaikovskaya, L.; Lapyonok, A.; Podvin, T.; Denishchik-Nelubina, N.; Fedarenka, A.; Svidinsky, V.

    2016-01-01

    The paper presents lecture materials given at the Nineteenth International Conference and School on Quantum Electronics "Laser Physics and Applications" (19th ICSQE) in 2016, Sozopol, Bulgaria and contains the results of the 10-year research of Belarusian Antarctic expeditions to study the atmospheric aerosol and Earth surface in Antarctica. The works focus on the studying variability and trends of aerosol, cloud and snow characteristics in the Antarctic and the links of these processes with the long range transport of atmospheric pollutants and climate changes.

  15. 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

  16. 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.

  17. [Distribution of bacteria of Methylobacterium genus in the terrestrial biotopes of the Antarctic region].

    Science.gov (United States)

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

    2009-01-01

    Methylotrophs distribution has been studied in the terrestrial biotopes (moss, lichen, grass, soil, sludge of lakes) on the islands of Galindez, Barkhans, Irizar, Uruguay, Jalour, Petermann, Berthelot, Cruls, King George, Corner, Skua located in the Pacific sector of the Antarctic Region, as well as in analogous biotopes on the western shore of the Antarctic peninsula Basing on a complex of diagnosis features the isolated pink-pigmented strains, which facultatively use methanol and realize the serine cycle of assimilation of one-carbon compounds, are attributed to Methylobacterium genus. Methylobacterium strains occur more often in mosses, grass Deschampsia antarctica and lichens, than in the soil and lake sludge. Some regions ofAntarctica are comparable by the number of Methylobacterium cells with the same in the regions with moderate climate. An analysis of gene sequences 16S rRNA of the Antarctic methylobacteria with those of GenBank has shown a high extent of similarity with Methylobacterium extorquens (99.4-99.7%). Notwithstanding that the strains of Methylobacterium are resistant to the broad range of extreme factors (gamma-irradiation, UV-irradiation, dehydration), the Antarctic and collection strains of the genus were sensitive to the ions of such heavy metals as Cu, Hg, Cd, Cr (10 mg/l).

  18. 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.

  19. Impacts of marine instability across the East Antarctic Ice Sheet on Southern Ocean dynamics

    Directory of Open Access Journals (Sweden)

    S. J. Phipps

    2016-09-01

    Full Text Available Recent observations and modelling studies have demonstrated the potential for rapid and substantial retreat of large sectors of the East Antarctic Ice Sheet (EAIS. This has major implications for ocean circulation and global sea level. Here we examine the effects of increasing meltwater from the Wilkes Basin, one of the major marine-based sectors of the EAIS, on Southern Ocean dynamics. Climate model simulations reveal that the meltwater flux rapidly stratifies surface waters, leading to a dramatic decrease in the rate of Antarctic Bottom Water (AABW formation. The surface ocean cools but, critically, the Southern Ocean warms by more than 1 °C at depth. This warming is accompanied by a Southern Ocean-wide “domino effect”, whereby the warming signal propagates westward with depth. Our results suggest that melting of one sector of the EAIS could result in accelerated warming across other sectors, including the Weddell Sea sector of the West Antarctic Ice Sheet. Thus, localised melting of the EAIS could potentially destabilise the wider Antarctic Ice Sheet.

  20. Antarctic new particle formation from continental biogenic precursors

    Directory of Open Access Journals (Sweden)

    E.-M. Kyrö

    2013-04-01

    Full Text Available Over Antarctica, aerosol particles originate almost entirely from marine areas, with minor contribution from long-range transported dust or anthropogenic material. The Antarctic continent itself, unlike all other continental areas, has been thought to be practically free of aerosol sources. Here we present evidence of local aerosol production associated with melt-water ponds in continental Antarctica. We show that in air masses passing such ponds, new aerosol particles are efficiently formed and these particles grow up to sizes where they may act as cloud condensation nuclei (CCN. The precursor vapours responsible for aerosol formation and growth originate very likely from highly abundant cyanobacteria Nostoc commune (Vaucher communities of local ponds. This is the first time freshwater vegetation has been identified as an aerosol precursor source. The influence of the new source on clouds and climate may increase in future Antarctica, and possibly elsewhere undergoing accelerating summer melting of semi-permanent snow cover.

  1. Radiative effects of clouds and cryosphere in the Antarctic

    Directory of Open Access Journals (Sweden)

    Takashi Yamanouchi

    1997-03-01

    Full Text Available Examination of the effects of clouds, ice sheet and sea ice on the radiation budget in the Antarctic using Earth Radiation Budget Experiment (ERBE data were reported. The continental ice sheet affects not only the albedo, but also the surface temperature because of elevation, and hence the OLR. Sea ice, which is a critical climate feedback factor, appears to have less impact on radiation than do clouds. However, these surfaces lie underneath clouds, and it was found that the independent effect of sea ice is as large as that of clouds, and clouds are masking the radiative effect of sea ice by more than half. The radiation budget at the top of the atmosphere from satellite observation and that at the surface from the surface radiation measurements at Syowa and South Pole Stations were compared. Cloud radiative forcing at both stations for the surface, atmosphere and top of the atmosphere was derived.

  2. Antarctic new particle formation from continental biogenic precursors

    Science.gov (United States)

    Kyrö, E.-M.; Kerminen, V.-M.; Virkkula, A.; Dal Maso, M.; Parshintsev, J.; Ruíz-Jimenez, J.; Forsström, L.; Manninen, H. E.; Riekkola, M.-L.; Heinonen, P.; Kulmala, M.

    2013-04-01

    Over Antarctica, aerosol particles originate almost entirely from marine areas, with minor contribution from long-range transported dust or anthropogenic material. The Antarctic continent itself, unlike all other continental areas, has been thought to be practically free of aerosol sources. Here we present evidence of local aerosol production associated with melt-water ponds in continental Antarctica. We show that in air masses passing such ponds, new aerosol particles are efficiently formed and these particles grow up to sizes where they may act as cloud condensation nuclei (CCN). The precursor vapours responsible for aerosol formation and growth originate very likely from highly abundant cyanobacteria Nostoc commune (Vaucher) communities of local ponds. This is the first time freshwater vegetation has been identified as an aerosol precursor source. The influence of the new source on clouds and climate may increase in future Antarctica, and possibly elsewhere undergoing accelerating summer melting of semi-permanent snow cover.

  3. 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.

  4. 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.

  5. 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.

  6. 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.)

  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. Chilean Antarctic Stations on King George Island

    Directory of Open Access Journals (Sweden)

    Katsutada Kaminuma

    2000-07-01

    Full Text Available The purpose of my visit to Chilean Antarctic Stations was to assess the present status of geophysical observations and research, as the South Shetland Island, West Antarctica, where the stations are located, are one of the most active tectonic regions on the Antarctic plate. The Instituto Antartico Chileno (INACH kindly gave me a chance to stay in Frei/Escudero Bases as an exchange scientist under the Antarctic Treaty for two weeks in January 2000. I stayed in Frei Base as a member of a geological survey group named "Tectonic Evolution of the Antarctic Peninsula" which was organized by Prof. F. Herve, University of Chile, from January 05 to 19,2000. All my activity in the Antarctic was organized by INACH. During my stay in Frei Base, I also visited Bellingshausen (Russian, Great Wall (China and Artigas (Uruguay stations. All these stations are located within walking distance of Frei Base. King Sejong Station (Korea, located 10km east from Frei Base, and Jubany Base (Argentine, another 6km south-east from King Sejong Station, were also visited with the aid of a zodiac boat that was kindly operated for us by King Sejong Station. All stations except Escudero Base carry out meteorological observations. The seismological observations in Frei Base are operated by Washington State University of the U. S. monitoring of earthquake activity and three-component geomagnetic observations are done at King Sejong and Great Wall stations. Earth tide is monitored at Artigas Base. Continuous monitoring of GPS and gravity change are planned at King Sejong Station in the near future. Scientific research activities of each country in the area in the 1999/2000 Antarctic summer season were studied and the logistic ability of all stations was also assessed for our future international cooperation.

  9. 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.

  10. Uncertainty in hydrological signatures

    Science.gov (United States)

    McMillan, Hilary; Westerberg, Ida

    2015-04-01

    Information that summarises the hydrological behaviour or flow regime of a catchment is essential for comparing responses of different catchments to understand catchment organisation and similarity, and for many other modelling and water-management applications. Such information types derived as an index value from observed data are known as hydrological signatures, and can include descriptors of high flows (e.g. mean annual flood), low flows (e.g. mean annual low flow, recession shape), the flow variability, flow duration curve, and runoff ratio. Because the hydrological signatures are calculated from observed data such as rainfall and flow records, they are affected by uncertainty in those data. Subjective choices in the method used to calculate the signatures create a further source of uncertainty. Uncertainties in the signatures may affect our ability to compare different locations, to detect changes, or to compare future water resource management scenarios. The aim of this study was to contribute to the hydrological community's awareness and knowledge of data uncertainty in hydrological signatures, including typical sources, magnitude and methods for its assessment. We proposed a generally applicable method to calculate these uncertainties based on Monte Carlo sampling and demonstrated it for a variety of commonly used signatures. The study was made for two data rich catchments, the 50 km2 Mahurangi catchment in New Zealand and the 135 km2 Brue catchment in the UK. For rainfall data the uncertainty sources included point measurement uncertainty, the number of gauges used in calculation of the catchment spatial average, and uncertainties relating to lack of quality control. For flow data the uncertainty sources included uncertainties in stage/discharge measurement and in the approximation of the true stage-discharge relation by a rating curve. The resulting uncertainties were compared across the different signatures and catchments, to quantify uncertainty

  11. 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.

  12. Mysterious iodine-overabundance in Antarctic meteorites

    Science.gov (United States)

    Dreibus, G.; Waenke, H.; Schultz, L.

    1986-01-01

    Halogen as well as other trace element concentrations in meteorite finds can be influenced by alteration processes on the Earth's surface. The discovery of Antarctic meteorites offered the opportunity to study meteorites which were kept in one of the most sterile environment of the Earth. Halogen determination in Antartic meteorites was compared with non-Antarctic meteorites. No correlation was found between iodine concentration and the weathering index, or terrestrial age. The halogen measurements indicate a contaminating phase rich in iodine and also containing chlorine. Possible sources for this contamination are discussed.

  13. Mysterious iodine-overabundance in Antarctic meteorites

    International Nuclear Information System (INIS)

    Dreibus, G.; Waenke, H.; Schultz, L.

    1986-01-01

    Halogen as well as other trace element concentrations in meteorite finds can be influenced by alteration processes on the Earth's surface. The discovery of Antarctic meteorites offered the opportunity to study meteorites which were kept in one of the most sterile environment of the Earth. Halogen determination in Antartic meteorites was compared with non-Antarctic meteorites. No correlation was found between iodine concentration and the weathering index, or terrestrial age. The halogen measurements indicate a contaminating phase rich in iodine and also containing chlorine. Possible sources for this contamination are discussed

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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).

  20. Tolerance of Antarctic soil fungi to hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Kevin A.; Bridge, Paul; Clark, Melody S. [British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET (United Kingdom)

    2007-01-01

    Little is known about the effects of hydrocarbons and fuel oil on Antarctic filamentous fungi in the terrestrial Antarctic environment. Growth of fungi and bacteria from soils around Rothera Research Station (Adelaide Island, Antarctic Peninsula) was assessed in the presence of ten separate aromatic and aliphatic hydrocarbons [marine gas oil (MGO), dodecane, hexadecane, benzoic acid, p-hydroxybenzoic acid, toluene, phenol, biphenyl, naphthalene and m- and p-xylenes with ethylbenzene]. Aromatic hydrocarbons inhibited soil microbial growth more than aliphatic hydrocarbons. Soil microorganisms from a moss patch, where little previous impact or hydrocarbon contamination had occurred, were less tolerant of hydrocarbons than those from high impact sites. Fungal growth rates of Mollisia sp., Penicillium commune, Mortierella sp., Trichoderma koningii, Trichoderma sp. and Phoma herbarum were assessed in the presence of hydrocarbons. Generally, aromatic hydrocarbons inhibited or stopped hyphal extension, though growth rates increased with some aliphatic hydrocarbons. Hyphal dry weight measurements suggested that Mortierella sp. may be able to use dodecane as sole carbon and energy source. Hydrocarbon-degrading Antarctic fungi may have use in future hydrocarbon spill bioremediation. (author)

  1. 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...

  2. 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...

  3. Tephra compositions from Late Quaternary volcanoes around the Antarctic Peninsula

    Science.gov (United States)

    Kraus, S.

    2009-12-01

    /Hf ratios lower than N-MORB, all other volcanoes including the Larsen Rift centers display Zr/Hf higher than N-MORB. It is expected that the correlation of the new data with published data from tephra layers found in ice, lake and marine sediment cores will contribute to a better constrained timing of individual climatic events identified in the northern Antarctic Peninsula area. Late Quaternary volcanoes around the northern Antarctic Peninsula.

  4. A recent case of Antarctic bioprospecting from Japan

    Directory of Open Access Journals (Sweden)

    Akiho Shibata

    2010-03-01

    Full Text Available Antarctic bioprospecting, namely the search for valuable genetic or chemical compounds in Antarctic nature, has been the subject of intense discussion within Antarctic Treaty Consultative Meetings. In this discussion, based on the so-called "end-users view point," utilizing the patent database to see how much Antarctic biological material has been used in patents, Antarctic bioprospecting has been depicted as a lucrative commercial activity operated by big multinational companies. This paper, instead, proposes an "access view point" for Antarctic bioprospecting, by examining a recent Japanese case in which scientists participating in the Japanese Antarctic Research Expedition in 2007 collected some sediment from Antarctic lakes near Syowa Station, isolated and cultured a particular fungus, and found the first evidence of the presence of antifreezing activity in oomycetes. In 2009, the scientists' affiliate institutions, including the National Institute of Advanced Industrial Science and Technology, applied for a patent on Antarctomyces psychrotrophicus Syw-1 and the antifreeze protein obtained from it. A detailed examination of this case demonstrates that the dichotomy of Antarctic bioprospecting into "commercial" and "scientific" does not reflect the reality of bioprospecting activities and, therefore, does not provide an appropriate ground for legal and policy discussion on Antarctic bioprospecting.

  5. The Antarctic Master Directory -- the Electronic Card Catalog of Antarctic Data

    Science.gov (United States)

    Scharfen, G.; Bauer, R.

    2003-12-01

    The Antarctic Master Directory (AMD) is a Web-based, searchable record of thousands of Antarctic data descriptions. These data descriptions contain information about what data were collected, where they were collected, when they were collected, who the scientists are, who the point of contact is, how to get the data, and information about the format of the data and what documentation and bibliographic information exists. With this basic descriptive information about content and access for thousands of Antarctic scientific data sets, the AMD is a resource for scientists to advertise the data they have collected and to search for data they need. The AMD has been created by more than twenty nations which conduct research in the Antarctic under the auspices of the Antarctic Treaty. It is a part of the International Directory Network/Global Change Master Directory (IDN/GCMD). Using the AMD is easy. Users can search on subject matter key words, data types, geographic place-names, temporal or spatial ranges, or conduct free-text searches. To search the AMD go to: http://gcmd.nasa.gov/Data/portals/amd/. Contributing your own data descriptions for Antarctic data that you have collected is also easy. Scientists can start by submitting a short data description first (as a placeholder in the AMD, and to satisfy National Science Foundation (NSF) reporting requirements), and then add to, modify or update their record whenever it is appropriate. An easy to use on-line tool and a simple tutorial are available at: http://nsidc.org/usadcc. With NSF Office of Polar Programs (OPP) funding, the National Snow and Ice Data Center (NSIDC) operates the U.S. Antarctic Data Coordination Center (USADCC), partly to assist scientists in using and contributing to the AMD. The USADCC website is at http://nsidc.org/usadcc.

  6. A Directed Signature Scheme and its Applications

    OpenAIRE

    Lal, Sunder; Kumar, Manoj

    2004-01-01

    This paper presents a directed signature scheme with the property that the signature can be verified only with the help of signer or signature receiver. We also propose its applications to share verification of signatures and to threshold cryptosystems.

  7. Formation of Antarctic Intermediate Water during the Plio-Pleistocene

    Science.gov (United States)

    Karas, C.; Goldstein, S. L.; deMenocal, P. B.

    2017-12-01

    Antarctic Intermediate Water (AAIW) plays a fundamental role in modern climate change. It is an important sink for anthropogenic CO2, it represents an important source water in several (sub)tropical upwelling regions and it is the coldwater route from the Southern Hemisphere to the North Atlantic Ocean replacing North Atlantic Deep Water (NADW). During the last 4 million years, which marks the transition from the warm Pliocene climate towards icehouse conditions, the formation of this watermass is still largely unknown. We here present a multi-proxy approach using neodymium isotopes (ɛNd) on Fe-Mn encrusted foraminifera and coupled benthic Mg/Ca and stable isotopes from South Atlantic Site 516, within AAIW, to reconstruct its variability. Our data show that the modern formation of AAIW started about 3 million years ago, indicated by a distinct drop of ɛNd by 1.5, a cooling and freshening of benthic TMg/Ca by 8°C and a drop in benthic d13C values towards modern times. We interpret these changes as a reduced inflow of Pacific waters into the South Atlantic and the onset of modern deep vertical mixing at the source regions of AAIW near the polar front. These processes had significant effects on the CO2 storage of the ocean that supported global cooling and the intensification of the Northern Hemisphere Glaciation.

  8. Psychrotrophic metal tolerant bacteria for mobilisation of metals in Antarctic waters

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, M.J.B.D.

    Cold tolerant psychrotrophic bacteria abound in the Antarctic waters. While Antarctic krills are known to concentrate heavy metals at ppm levels, psychrotrophic bacteria from Antarctic fresh and marine waters have been reported to tolerate them...

  9. 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

  10. Environmental constraints on West Antarctic ice-sheet formation

    Energy Technology Data Exchange (ETDEWEB)

    Lindstrom, D R; MacAyeal, D R

    1987-01-01

    Small perturbations in Antarctic environmental conditions can culminate in the demise of the Antarctic ice sheet's western sector. This may have happened during the last interglacial period, and could recur within the next millennium due to atmospheric warming from trace gas and CO/sub 2/ increases. In this study, we investigate the importance of sea-level, accumulation rate, and ice influx from the East Antarctic ice sheet in the re-establishment of the West Antarctic ice sheet from a thin cover using a time-dependent numerical ice-shelf model. Our results show that a precursor to the West Antarctic ice sheet can form within 3000 years. Sea-level lowering caused by ice-sheet development in the Northern Hemisphere has the greatest environmental influence. Under favorable conditions, ice grounding occurs over all parts of the West Antarctic ice sheet except up-stream of Thwaites Glacier and in the Ross Sea region.

  11. [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

  12. Antarctic Meteorite Classification and Petrographic Database

    Science.gov (United States)

    Todd, Nancy S.; Satterwhite, C. E.; Righter, Kevin

    2011-01-01

    The Antarctic Meteorite collection, which is comprised of over 18,700 meteorites, is one of the largest collections of meteorites in the world. These meteorites have been collected since the late 1970's as part of a three-agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution [1]. Samples collected each season are analyzed at NASA s Meteorite Lab and the Smithsonian Institution and results are published twice a year in the Antarctic Meteorite Newsletter, which has been in publication since 1978. Each newsletter lists the samples collected and processed and provides more in-depth details on selected samples of importance to the scientific community. Data about these meteorites is also published on the NASA Curation website [2] and made available through the Meteorite Classification Database allowing scientists to search by a variety of parameters

  13. 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.

  14. Antarctic Glaciological Data at NSIDC: field data, temperature, and ice velocity

    Science.gov (United States)

    Bauer, R.; Bohlander, J.; Scambos, T.; Berthier, E.; Raup, B.; Scharfen, G.

    2003-12-01

    An extensive collection of many Antarctic glaciological parameters is available for the polar science community upon request. The National Science Foundation's Office of Polar Programs funds the Antarctic Glaciological Data Center (AGDC) at the National Snow and Ice Data Center (NSIDC) to archive and distribute Antarctic glaciological and cryospheric system data collected by the U.S. Antarctic Program. AGDC facilitates data exchange among Principal Investigators, preserves recently collected data useful to future research, gathers data sets from past research, and compiles continent-wide information useful for modeling and field work planning. Data sets are available via our web site, http://nsidc.org/agdc/. From here, users can access extensive documentation, citation information, locator maps, derived images and references, and the numerical data. More than 50 Antarctic scientists have contributed data to the archive. Among the compiled products distributed by AGDC are VELMAP and THERMAP. THERMAP is a compilation of over 600 shallow firn temperature measurements ('10-meter temperatures') collected since 1950. These data provide a record of mean annual temperature, and potentially hold a record of climate change on the continent. The data are represented with maps showing the traverse route, and include data sources, measurement technique, and additional measurements made at each site, i.e., snow density and accumulation. VELMAP is an archive of surface ice velocity measurements for the Antarctic Ice Sheet. The primary objective of VELMAP is to assemble a historic record of outlet glaciers and ice shelf ice motion over the Antarctic. The collection includes both PI-contributed measurements and data generated at NSIDC using Landsat and SPOT satellite imagery. Tabular data contain position, speed, bearing, and data quality information, and related references. Two new VELMAP data sets are highlighted: the Mertz Glacier and the Institute Ice Stream. Mertz Glacier ice

  15. Satellite magnetic anomalies of the Antarctic crust

    Directory of Open Access Journals (Sweden)

    D. E. Alsdorf

    2000-06-01

    Full Text Available Spatially and temporally static crustal magnetic anomalies are contaminated by static core field effects above spherical harmonic degree 12 and dynamic, large-amplitude external fields. To extract crustal magnetic anomalies from the measurements of NASA's Magsat mission, we separate crustal signals from both core and external field effects. In particular, we define Magsat anomalies relative to the degree 11 field and use spectral correlation theory to reduce them for external field effects. We obtain a model of Antarctic crustal thickness by comparing the region's terrain gravity effects to free-air gravity anomalies derived from the Earth Gravity Model 1996 (EGM96. To separate core and crustal magnetic effects, we obtain the pseudo-magnetic effect of the crustal thickness variations from their gravity effect via Poisson's theorem for correlative potentials. We compare the pseudo-magnetic effect of the crustal thickness variations to field differences between degrees 11 and 13 by spectral correlation analysis. We thus identify and remove possible residual core field effects in the Magsat anomalies relative to the degree 11 core field. The resultant anomalies reflect possible Antarctic contrasts due both to crustal thickness and intracrustal variations of magnetization. In addition, they provide important constraints on the geologic interpretation of aeromagnetic survey data, such as are available for the Weddell Province. These crustal anomalies also may be used to correct for long wavelength errors in regional compilations of near-surface magnetic survey data. However, the validity of these applications is limited by the poor quality of the Antarctic Magsat data that were obtained during austral Summer and Fall when south polar external field activity was maximum. Hence an important test and supplement for the Antarctic crustal Magsat anomaly map will be provided by the data from the recently launched Ørsted mission, which will yield coverage

  16. Antarctic carbonaceous chondrites - New opportunities for research

    Science.gov (United States)

    McSween, Harry Y., Jr.

    An account is given of the types of carbonaceous meteorites available in the Antarctic collections of the U.S. and Japan. In the case of the collection for Victoria Land and Queen Maud Land, all known classes for meteorites except C1 are present; available pairing data, though limited, are indicative of the presence of many different falls. Thus far, attention has been focused on the largest meteorites. Most samples, however, are small.

  17. America on the Ice. Antarctic Policy Issues

    Science.gov (United States)

    1990-01-01

    Malay- sian Prime Minister- Mahatir Mohamad-fired the open- ing volleys during a UN General Assembly speech in September of that year. He noted...define the problem of unin- habited lands." According to Mahatir , the Antarctic conti- nent clearly qualified for such consideration and, not... Mahatir , 109 Molodezhnaya station, 124 Moon Treaty (1979), 108 Mount Erebus, 134 Myhre, Jeffrey, 59 NASA. See National Aeronautics and Space

  18. Estimating Antarctic Geothermal Heat Flux using Gravity Inversion

    Science.gov (United States)

    Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; Golynsky, A. V.; Sasha Rogozhina, Irina

    2013-04-01

    Geothermal heat flux (GHF) in Antarctica is very poorly known. We have determined (Vaughan et al. 2012) top basement heat-flow for Antarctica and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning (Chappell & Kusznir 2008). Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental and oceanic lithosphere. The sensitivity of present-day Antarctic top basement heat-flow to initial continental radiogenic heat productivity, continental rift and margin breakup age has been examined. Knowing GHF distribution for East Antarctica and the Gamburtsev Subglacial Mountains (GSM) region in particular is critical because: 1) The GSM likely acted as key nucleation point for the East Antarctic Ice Sheet (EAIS); 2) the region may contain the oldest ice of the EAIS - a prime target for future ice core drilling; 3) GHF is important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology (Bell et al. 2011). An integrated multi-dataset-based GHF model for East Antarctica is planned that will resolve the wide range of estimates previously published using single datasets. The new map and existing GHF distribution estimates available for Antarctica will be evaluated using direct ice temperature measurements obtained from deep ice cores, estimates of GHF derived from subglacial lakes, and a thermodynamic ice-sheet model of the Antarctic Ice Sheet driven by past climate reconstructions and each of analysed heat flow maps, as has recently been done for the Greenland region (Rogozhina et al. 2012). References Bell, R.E., Ferraccioli, F., Creyts, T.T., Braaten, D., Corr, H., Das, I., Damaske, D., Frearson, N

  19. Archival processes of the water stable isotope signal in East Antarctic ice cores

    Science.gov (United States)

    Casado, Mathieu; Landais, Amaelle; Picard, Ghislain; Münch, Thomas; Laepple, Thomas; Stenni, Barbara; Dreossi, Giuliano; Ekaykin, Alexey; Arnaud, Laurent; Genthon, Christophe; Touzeau, Alexandra; Masson-Delmotte, Valerie; Jouzel, Jean

    2018-05-01

    The oldest ice core records are obtained from the East Antarctic Plateau. Water isotopes are key proxies to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in trajectory-based Rayleigh distillation and isotope-enabled climate models. However, a quantitative understanding of processes potentially altering snow isotopic composition after deposition is still missing. In low-accumulation sites, such as those found in East Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretability of an ice core's isotopic composition. By combining observations of isotopic composition in vapour, precipitation, surface snow and buried snow from Dome C, a deep ice core site on the East Antarctic Plateau, we found indications of a seasonal impact of metamorphism on the surface snow isotopic signal when compared to the initial precipitation. Particularly in summer, exchanges of water molecules between vapour and snow are driven by the diurnal sublimation-condensation cycles. Overall, we observe in between precipitation events modification of the surface snow isotopic composition. Using high-resolution water isotopic composition profiles from snow pits at five Antarctic sites with different accumulation rates, we identified common patterns which cannot be attributed to the seasonal variability of precipitation. These differences in the precipitation, surface snow and buried snow isotopic composition provide evidence of post-deposition processes affecting ice core records in low-accumulation areas.

  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. 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.

  2. 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.

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

    NARCIS (Netherlands)

    Mourik, A.A.|info:eu-repo/dai/nl/304849383

    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

  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. Modem Signature Analysis.

    Science.gov (United States)

    1982-10-01

    AD-A127 993 MODEM SIGNATURE ANALISIS (U) PAR TECHNOLOGY CORP NEW / HARTFORD NY V EDWARDS ET AL. OCT 82 RADC-TR-82-269 F30602-80-C-0264 NCLASSIFIED F/G...as an indication of the class clustering and separation between different classes in the modem data base. It is apparent from the projection that the...that as the clusters disperse, the likelihood of a sample crossing the boundary into an adjacent region and causing a symbol decision error increases. As

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. IODP Expedition 318: From Greenhouse to Icehouse at the Wilkes Land Antarctic Margin

    Directory of Open Access Journals (Sweden)

    Adam Klaus

    2011-09-01

    Full Text Available Integrated Ocean Drilling Program (IODP Expedition 318, Wilkes Land Glacial History, drilled a transect of sites across the Wilkes Land margin of Antarctica to provide a long-term record of the sedimentary archives of Cenozoic Antarctic glaciation and its intimate relationships with global climatic and oceanographic change. The Wilkes Land drilling program was undertaken to constrain the age, nature, and paleoenvironment of the previously only seismicallyinferred glacial sequences. The expedition (January–March 2010 recovered ~2000 meters of high-quality middle Eocene–Holocene sediments from water depths between 400 m and 4000 m at four sites on the Wilkes Land rise (U1355, U1356, U1359, and U1361 and three sites on the Wilkes Land shelf (U1357, U1358, and U1360. These records span ~53 million years of Antarctic history, and the various seismic units (WL-S4–WL-S9 have been successfully dated. The cores reveal the history of the Wilkes Land Antarctic margin from an ice-free “greenhouse” Antarctica, to the first cooling, to the onset and erosional consequences of the first glaciation and the subsequentdynamics of the waxing and waning ice sheets, all the way to thick, unprecedented “tree ring style” records with seasonal resolution of the last deglaciation that began ~10,000 y ago. The cores also reveal details of the tectonic history of the Australo-Antarctic Gulf from 53 Ma, portraying the onset of the second phase of rifting between Australia and Antarctica, to ever-subsiding margins and deepening,to the present continental and ever-widening ocean/continent configuration.

  12. 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

  13. Microbial ecology of extreme environments: Antarctic yeasts and growth in substrate-limited habitats

    Science.gov (United States)

    Vishniac, H. S.

    1985-01-01

    The high, dry valleys of the Ross Desert of Antarctic, characterized by extremely low temperatures, aridity and a depauperate biota, are used as an analog of the postulated extreme climates of other planetary bodies of the Solar System to test the hypothesis that if life could be supported by Ross, it might be possible where similar conditions prevail. The previously considered sterility of the Ross Desert soil ecosystem has yielded up an indigenous yeast, Cryptoccus vishniacci, which is able to resist the extremes of cold, wet and dry freezing, and long arid periods, while making minimal nutritional demands on the soil.

  14. Antarctic Ice Sheet Discharge Driven by Atmosphere-Ocean Feedbacks Across the Last Glacial Termination

    Science.gov (United States)

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

    2016-12-01

    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 identify ice-climate feedbacks that could improve future projections1,2. Whilst the sequence of events during this period are reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records2, making it difficult to assess relationships between Antarctic ice-sheet dynamics, climate change and sea-level rise3-5. Here we present results from a highly-resolved `horizontal ice core'6,7 from the Weddell Sea Embayment, which records millennial-scale ice-sheet dynamics across this extensive sector of Antarctica. Counterintuitively, we find ice-sheet surface drawdown of 600 m across the Antarctic Cold Reversal (ACR; 14,600-12,700 yrs ago)5, with stabilisation during the subsequent millennia of atmospheric warming. Earth system and ice-sheet modelling highlights that this response was likely sustained by strong ocean-ice feedbacks4,8; however, the drivers remain uncertain. Given the coincidence of the ice-sheet changes recorded with marked shifts in atmospheric circulation9,10,11we suggest that millennial-scale Antarctic ice-sheet behaviour was initiated and sustained by global atmospheric teleconnections across the LGT. This has important ramifications ice-sheet stability under contemporary climate change, with changing atmospheric and oceanic circulation patterns. 1 Collins, M. et al. in Climate Change 2013: The Physical Science Basis. 2 Weber, M. E. et al. Nature 510, 134-138, (2014). 3 Weaver, A. J., et al., Science 299, 1709-1713, (2003). 4 Golledge, N. R. et al. Nat Commun 5, (2014). 5 Pedro, J. B. et al. Nature Geosci9. 51-55 (2015). 6 Turney, C. S. M. et al. Journal of Quaternary Science 28, 697-704 (2013). 7 Winter, K. et al. Geophys. Res. Lett.43. 5. 2019-2026 (2016). 8 Menviel, L., A. et al., Quaternary Science Reviews 30, 1155-1172 (2011). 9 Hogg

  15. Proxies and measurement techinques for mineral dust in antarctic ice cores

    DEFF Research Database (Denmark)

    Ruth..[], Urs; Bigler, Matthias

    2008-01-01

    analysis), elemental analysis (inductively coupled plasma mass spectroscopy at pH 1 and after full acid digestion), and water-insoluble elemental analysis (proton induced X-ray emission). Antarctic ice core samples covering the last deglaciation from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land......-MS measurements depends on the digestion method and is different for different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analyzed samples further reveal a change...

  16. Links between Patagonian Ice Sheet fluctuations and Antarctic dust variability during the last glacial period (MIS 4-2)

    Science.gov (United States)

    Kaiser, Jérôme; Lamy, Frank

    2010-06-01

    Antarctic and Greenland ice-core records reveal large fluctuations of dust input on both orbital and millennial time-scales with potential global climate implications. At least during glacial periods, the Antarctic dust fluctuations appear to be largely controlled by environmental changes in southern South America. We compare dust flux records from two Antarctic ice-cores to variations in the composition of the terrigenous supply at ODP Site 1233 located off southern Chile and known to record fluctuations in the extent of the northern part of the Patagonian ice-sheet (NPIS) during the last glacial period (Marine Isotope Stage, MIS, 4 to 2). Within age uncertainties, millennial-scale glacial advances (retreats) of the NPIS correlate to Antarctic dust maxima (minima). In turn, NPIS fluctuations were closely related to offshore sea surface temperature (SST) changes. This pattern suggests a causal link involving changes in temperature, in rock flour availability, in latitudinal extensions of the westerly winds and in foehn winds in the southern Pampas and Patagonia. We further suggest that the long-term trend of dust accumulation is partly linked to the sea-level related changes in the size if the Patagonian source area due to the particular morphology of the Argentine shelf. We suggest that sea-level drops at the beginning of MIS 4 and MIS 2 were important for long-term dust increases, while changes in the Patagonian dust source regions primarily control the early dust decrease during the MIS 4/3 transition and Termination 1.

  17. Individual odor recognition in birds: an endogenous olfactory signature on petrels' feathers?

    Science.gov (United States)

    Bonadonna, Francesco; Miguel, Eve; Grosbois, Vladimir; Jouventin, Pierre; Bessiere, Jean-Marie

    2007-09-01

    A growing body of evidence indicates that odors are used in individual, sexual, and species recognition in vertebrates, and may be reliable signals of quality and compatibility. Petrels are seabirds that exhibit an acute sense of smell. During the breeding period, many species of petrels live in dense colonies on small oceanic islands and form pairs that use individual underground burrows. Mates alternate between parental duties and foraging trips at sea. Returning from the ocean at night (to avoid bird predators), petrels must find their nest burrow. Antarctic prions, Pachyptila desolata, are thought to identify their nest by recognizing their partner's odor, suggesting the existence of an individual odor signature. We used gas chromatography and mass spectrometry to analyze extracts obtained from the feathers of 13 birds. The chemical profile of a single bird was more similar to itself, from year to year, than to that of any other bird. The profile contained up to a hundred volatile lipids, but the odor signature may be based on the presence or absence of a few specific compounds. Our results show that the odor signature in Antarctic prions is probably endogenous, suggesting that in some species of petrels it may broadcast compatibility and quality of potential mates.

  18. Draft genome of the Antarctic dragonfish, Parachaenichthys charcoti.

    Science.gov (United States)

    Ahn, Do-Hwan; Shin, Seung Chul; Kim, Bo-Mi; Kang, Seunghyun; Kim, Jin-Hyoung; Ahn, Inhye; Park, Joonho; Park, Hyun

    2017-08-01

    The Antarctic bathydraconid dragonfish, Parachaenichthys charcoti, is an Antarctic notothenioid teleost endemic to the Southern Ocean. The Southern Ocean has cooled to -1.8ºC over the past 30 million years, and the seawater had retained this cold temperature and isolated oceanic environment because of the Antarctic Circumpolar Current. Notothenioids dominate Antarctic fish, making up 90% of the biomass, and all notothenioids have undergone molecular and ecological diversification to survive in this cold environment. Therefore, they are considered an attractive Antarctic fish model for evolutionary and ancestral genomic studies. Bathydraconidae is a speciose family of the Notothenioidei, the dominant taxonomic component of Antarctic teleosts. To understand the process of evolution of Antarctic fish, we select a typical Antarctic bathydraconid dragonfish, P. charcoti. Here, we have sequenced, de novo assembled, and annotated a comprehensive genome from P. charcoti. The draft genome of P. charcoti is 709 Mb in size. The N50 contig length is 6145 bp, and its N50 scaffold length 178 362 kb. The genome of P. charcoti is predicted to contain 32 712 genes, 18 455 of which have been assigned preliminary functions. A total of 8951 orthologous groups common to 7 species of fish were identified, while 333 genes were identified in P. charcoti only; 2519 orthologous groups were also identified in both P. charcoti and N. coriiceps, another Antarctic fish. Four gene ontology terms were statistically overrepresented among the 333 genes unique to P. charcoti, according to gene ontology enrichment analysis. The draft P. charcoti genome will broaden our understanding of the evolution of Antarctic fish in their extreme environment. It will provide a basis for further investigating the unusual characteristics of Antarctic fishes. © The Author 2017. Published by Oxford University Press.

  19. Southern Ocean Phytoplankton in a Changing Climate

    OpenAIRE

    Deppeler, Stacy L.; Davidson, Andrew T.

    2017-01-01

    Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced sal...

  20. 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

  1. 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...

  2. 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...

  3. 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,...

  4. 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.

  5. 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: National Science Foundation. ACTION: Final rule. SUMMARY: Pursuant to the Antarctic Conservation Act of 1978, The National Science Foundation (NSF) is amending its regulations to reflect newly designated...

  6. Transcriptome of the Antarctic brooding gastropod mollusc Margarella antarctica.

    Science.gov (United States)

    Clark, Melody S; Thorne, Michael A S

    2015-12-01

    454 RNA-Seq transcriptome data were generated from foot tissue of the Antarctic brooding gastropod mollusc Margarella antarctica. A total of 6195 contigs were assembled de novo, providing a useful resource for researchers with an interest in Antarctic marine species, phylogenetics and mollusc biology, especially shell production. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. 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.

  8. 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...

  9. Water Circulation and Marine Environment in the Antarctic Traced by Speciation of 129I and 127I

    DEFF Research Database (Denmark)

    Xing, Shan; Hou, Xiaolin; Aldahan, Ala

    2017-01-01

    Emissions of anthropogenic 129I from human nuclear activities are now detected in the surface water of the Antarctic seas. Surface seawater samples from the Drake Passage, Bellingshausen, Amundsen, and Ross Seas were analyzed for total 129I and 127I, as well as for iodide and iodate of these two....... The iodine distribution patterns provide useful information on surface water transport and mixing that are vital for better understanding of the Southern Oceans effects on the global climate change. The results indicate multiple spatial interactions between the Antarctic Circumpolar Current (ACC......) and Antarctic Peninsula Coastal Current (APCC). These interactions happen in restricted circulation pathways that may partly relate to glacial melting and icebergs transport. Biological activity during the warm season should be one of the key factors controlling the reduction of iodate in the coastal water...

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

    NARCIS (Netherlands)

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

    2018-01-01

    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

  11. Revision of Eocene Antarctic carpet sharks (Elasmobranchii, Orectolobiformes) from Seymour Island, Antarctic Peninsula.

    Science.gov (United States)

    Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo A; Kriwet, Jürgen

    2017-01-01

    Seymour Island, Antarctic Peninsula, was once called the 'Rosetta Stone' of Southern Hemisphere palaeobiology, because this small island provides the most complete and richly fossiliferous Palaeogene sequence in Antarctica. Among fossil marine vertebrate remains, chondrichthyans seemingly were dominant elements in the Eocene Antarctic fish fauna. The fossiliferous sediments on Seymour Island are from the La Meseta Formation, which was originally divided into seven stratigraphical levels, TELMs 1-7 (acronym for Tertiary Eocene La Meseta) ranging from the upper Ypresian (early Eocene) to the late Priabonian (late Eocene). Bulk sampling of unconsolidated sediments from TELMs 5 and 6, which are Ypresian (early Eocene) and Lutetian (middle Eocene) in age, respectively, yielded very rich and diverse chondrichthyan assemblages including over 40 teeth of carpet sharks representing two new taxa, Notoramphoscyllium woodwardi gen. et sp. nov. and Ceolometlaouia pannucae gen. et sp. nov. Two additional teeth from TELM 5 represent two different taxa that cannot be assigned to any specific taxon and thus are left in open nomenclature. The new material not only increases the diversity of Eocene Antarctic selachian faunas but also allows two previous orectolobiform records to be re-evaluated. Accordingly, Stegostoma cf. faciatum is synonymized with Notoramphoscyllium woodwardi gen. et sp. nov., whereas Pseudoginglymostoma cf. brevicaudatum represents a nomen dubium . The two new taxa, and probably the additional two unidentified taxa, are interpreted as permanent residents, which most likely were endemic to Antarctic waters during the Eocene and adapted to shallow and estuarine environments.

  12. Signatures of Mechanosensitive Gating.

    Science.gov (United States)

    Morris, Richard G

    2017-01-10

    The question of how mechanically gated membrane channels open and close is notoriously difficult to address, especially if the protein structure is not available. This perspective highlights the relevance of micropipette-aspirated single-particle tracking-used to obtain a channel's diffusion coefficient, D, as a function of applied membrane tension, σ-as an indirect assay for determining functional behavior in mechanosensitive channels. While ensuring that the protein remains integral to the membrane, such methods can be used to identify not only the gating mechanism of a protein, but also associated physical moduli, such as torsional and dilational rigidity, which correspond to the protein's effective shape change. As an example, three distinct D-versus-σ "signatures" are calculated, corresponding to gating by dilation, gating by tilt, and gating by a combination of both dilation and tilt. Both advantages and disadvantages of the approach are discussed. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  13. Switch of flow direction in an Antarctic ice stream.

    Science.gov (United States)

    Conway, H; Catania, G; Raymond, C F; Gades, A M; Scambos, T A; Engelhardt, H

    2002-10-03

    Fast-flowing ice streams transport ice from the interior of West Antarctica to the ocean, and fluctuations in their activity control the mass balance of the ice sheet. The mass balance of the Ross Sea sector of the West Antarctic ice sheet is now positive--that is, it is growing--mainly because one of the ice streams (ice stream C) slowed down about 150 years ago. Here we present evidence from both surface measurements and remote sensing that demonstrates the highly dynamic nature of the Ross drainage system. We show that the flow in an area that once discharged into ice stream C has changed direction, now draining into the Whillans ice stream (formerly ice stream B). This switch in flow direction is a result of continuing thinning of the Whillans ice stream and recent thickening of ice stream C. Further abrupt reorganization of the activity and configuration of the ice streams over short timescales is to be expected in the future as the surface topography of the ice sheet responds to the combined effects of internal dynamics and long-term climate change. We suggest that caution is needed when using observations of short-term mass changes to draw conclusions about the large-scale mass balance of the ice sheet.

  14. 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 image pairs acquired during 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.

  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. An interpretation of signature inversion

    International Nuclear Information System (INIS)

    Onishi, Naoki; Tajima, Naoki

    1988-01-01

    An interpretation in terms of the cranking model is presented to explain why signature inversion occurs for positive γ of the axially asymmetric deformation parameter and emerges into specific orbitals. By introducing a continuous variable, the eigenvalue equation can be reduced to a one dimensional Schroedinger equation by means of which one can easily understand the cause of signature inversion. (author)

  17. Cell short circuit, preshort signature

    Science.gov (United States)

    Lurie, C.

    1980-01-01

    Short-circuit events observed in ground test simulations of DSCS-3 battery in-orbit operations are analyzed. Voltage signatures appearing in the data preceding the short-circuit event are evaluated. The ground test simulation is briefly described along with performance during reconditioning discharges. Results suggest that a characteristic signature develops prior to a shorting event.

  18. Ship Signature Management System : Functionality

    NARCIS (Netherlands)

    Arciszewski, H.F.R.; Lier, L. van; Meijer, Y.G.S.; Noordkamp, H.W.; Wassenaar, A.S.

    2010-01-01

    A signature of a platform is the manner in which the platform manifests itself to a certain type of sensor and how observable it is when such a sensor is used to detect the platform. Because many military platforms use sensors in different media, it is the total of its different signatures that

  19. Tropically driven and externally forced patterns of Antarctic sea ice change: reconciling observed and modeled trends

    Science.gov (United States)

    Schneider, David P.; Deser, Clara

    2017-09-01

    Recent work suggests that natural variability has played a significant role in the increase of Antarctic sea ice extent during 1979-2013. The ice extent has responded strongly to atmospheric circulation changes, including a deepened Amundsen Sea Low (ASL), which in part has been driven by tropical variability. Nonetheless, this increase has occurred in the context of externally forced climate change, and it has been difficult to reconcile observed and modeled Antarctic sea ice trends. To understand observed-model disparities, this work defines the internally driven and radiatively forced patterns of Antarctic sea ice change and exposes potential model biases using results from two sets of historical experiments of a coupled climate model compared with observations. One ensemble is constrained only by external factors such as greenhouse gases and stratospheric ozone, while the other explicitly accounts for the influence of tropical variability by specifying observed SST anomalies in the eastern tropical Pacific. The latter experiment reproduces the deepening of the ASL, which drives an increase in regional ice extent due to enhanced ice motion and sea surface cooling. However, the overall sea ice trend in every ensemble member of both experiments is characterized by ice loss and is dominated by the forced pattern, as given by the ensemble-mean of the first experiment. This pervasive ice loss is associated with a strong warming of the ocean mixed layer, suggesting that the ocean model does not locally store or export anomalous heat efficiently enough to maintain a surface environment conducive to sea ice expansion. The pervasive upper-ocean warming, not seen in observations, likely reflects ocean mean-state biases.

  20. Tropically driven and externally forced patterns of Antarctic sea ice change: reconciling observed and modeled trends

    Science.gov (United States)

    Schneider, David P.; Deser, Clara

    2018-06-01

    Recent work suggests that natural variability has played a significant role in the increase of Antarctic sea ice extent during 1979-2013. The ice extent has responded strongly to atmospheric circulation changes, including a deepened Amundsen Sea Low (ASL), which in part has been driven by tropical variability. Nonetheless, this increase has occurred in the context of externally forced climate change, and it has been difficult to reconcile observed and modeled Antarctic sea ice trends. To understand observed-model disparities, this work defines the internally driven and radiatively forced patterns of Antarctic sea ice change and exposes potential model biases using results from two sets of historical experiments of a coupled climate model compared with observations. One ensemble is constrained only by external factors such as greenhouse gases and stratospheric ozone, while the other explicitly accounts for the influence of tropical variability by specifying observed SST anomalies in the eastern tropical Pacific. The latter experiment reproduces the deepening of the ASL, which drives an increase in regional ice extent due to enhanced ice motion and sea surface cooling. However, the overall sea ice trend in every ensemble member of both experiments is characterized by ice loss and is dominated by the forced pattern, as given by the ensemble-mean of the first experiment. This pervasive ice loss is associated with a strong warming of the ocean mixed layer, suggesting that the ocean model does not locally store or export anomalous heat efficiently enough to maintain a surface environment conducive to sea ice expansion. The pervasive upper-ocean warming, not seen in observations, likely reflects ocean mean-state biases.

  1. 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

  2. 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

  3. 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.

  4. Automatic focusing system of BSST in Antarctic

    Science.gov (United States)

    Tang, Peng-Yi; Liu, Jia-Jing; Zhang, Guang-yu; Wang, Jian

    2015-10-01

    Automatic focusing (AF) technology plays an important role in modern astronomical telescopes. Based on the focusing requirement of BSST (Bright Star Survey Telescope) in Antarctic, an AF system is set up. In this design, functions in OpenCV is used to find stars, the algorithm of area, HFD or FWHM are used to degree the focus metric by choosing. Curve fitting method is used to find focus position as the method of camera moving. All these design are suitable for unattended small telescope.

  5. 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

  6. Antarctic Lithosphere Studies: Progress, Problems and Promise

    Science.gov (United States)

    Dalziel, I. W. D.; Wilson, T. J.

    2017-12-01

    In the sixty years since the International Geophysical Year, studies of the Antarctic lithosphere have progressed from basic geological observations and sparse geophysical measurements to continental-scale datasets of radiometric dates, ice thickness, bedrock topography and characteristics, seismic imaging and potential fields. These have been augmented by data from increasingly dense broadband seismic and geodetic networks. The Antarctic lithosphere is known to have been an integral part, indeed a "keystone" of the Pangea ( 250-185Ma) and Gondwanaland ( 540-180 Ma) supercontinents. It is widely believed to have been part of hypothetical earlier supercontinents Rodinia ( 1.0-0.75 Ga) and Columbia (Nuna) ( 2.0-1.5 Ga). Despite the paucity of exposure in East Antarctica, the new potential field datasets have emboldened workers to extrapolate Precambrian geological provinces and structures from neighboring continents into Antarctica. Hence models of the configuration of Columbia and its evolution into Rodinia and Gondwana have been proposed, and rift-flank uplift superimposed on a Proterozoic orogenic root has been hypothesized to explain the Gamburtsev Subglacial Mountains. Mesozoic-Cenozoic rifting has imparted a strong imprint on the West Antarctic lithosphere. Seismic tomographic evidence reveals lateral variation in lithospheric thickness, with the thinnest zones within the West Antarctic rift system and underlying the Amundsen Sea Embayment. Upper mantle low velocity zones are extensive, with a deeper mantle velocity anomaly underlying Marie Byrd Land marking a possible mantle plume. Misfits between crustal motions measured by GPS and GIA model predictions can, in part, be linked with the changes in lithosphere thickness and mantle rheology. Unusually high uplift rates measured by GPS in the Amundsen region can be interpreted as the response of regions with thin lithosphere and weak mantle to late Holocene ice mass loss. Horizontal displacements across the TAM

  7. Terrestrial and exposure histories of Antarctic meteorites

    International Nuclear Information System (INIS)

    Nishiizumi, K.

    1986-01-01

    Records of cosmogenic effects were studied in a large suite of Antarctic meteorites. The cosmogenic nuclide measurements together with cosmic ray track measurements on Antartic meteorites provide information such as exposure age, terrestrial age, size and depth in meteoroid or parent body, influx rate in the past, and pairing. The terrestrail age is the time period between the fall of the meteorite on the Earth and the present. To define terrestrial age, two or more nuclides with different half-lives and possibly noble gases are required. The cosmogenic radionuclides used are C-14, Kr-81, Cl-36, Al-26, Be-10, Mn-53, and K-40

  8. Terrestrial and exposure histories of Antarctic meteorites

    Science.gov (United States)

    Nishiizumi, K.

    1986-01-01

    Records of cosmogenic effects were studied in a large suite of Antarctic meteorites. The cosmogenic nuclide measurements together with cosmic ray track measurements on Antartic meteorites provide information such as exposure age, terrestrial age, size and depth in meteoroid or parent body, influx rate in the past, and pairing. The terrestrail age is the time period between the fall of the meteorite on the Earth and the present. To define terrestrial age, two or more nuclides with different half-lives and possibly noble gases are required. The cosmogenic radionuclides used are C-14, Kr-81, Cl-36, Al-26, Be-10, Mn-53, and K-40.

  9. Rapid Evolutionary Rates and Unique Genomic Signatures Discovered in the First Reference Genome for the Southern Ocean Salp, Salpa thompsoni (Urochordata, Thaliacea).

    Science.gov (United States)

    Jue, Nathaniel K; Batta-Lona, Paola G; Trusiak, Sarah; Obergfell, Craig; Bucklin, Ann; O'Neill, Michael J; O'Neill, Rachel J

    2016-10-30

    A preliminary genome sequence has been assembled for the Southern Ocean salp, Salpa thompsoni (Urochordata, Thaliacea). Despite the ecological importance of this species in Antarctic pelagic food webs and its potential role as an indicator of changing Southern Ocean ecosystems in response to climate change, no genomic resources are available for S. thompsoni or any closely related urochordate species. Using a multiple-platform, multiple-individual approach, we have produced a 318,767,936-bp genome sequence, covering >50% of the estimated 602 Mb (±173 Mb) genome size for S. thompsoni Using a nonredundant set of predicted proteins, >50% (16,823) of sequences showed significant homology to known proteins and ∼38% (12,151) of the total protein predictions were associated with Gene Ontology functional information. We have generated 109,958 SNP variant and 9,782 indel predictions for this species, serving as a resource for future phylogenomic and population genetic studies. Comparing the salp genome to available assemblies for four other urochordates, Botryllus schlosseri, Ciona intestinalis, Ciona savignyi and Oikopleura dioica, we found that S. thompsoni shares the previously estimated rapid rates of evolution for these species. High mutation rates are thus independent of genome size, suggesting that rates of evolution >1.5 times that observed for vertebrates are a broad taxonomic characteristic of urochordates. Tests for positive selection implemented in PAML revealed a small number of genes with sites undergoing rapid evolution, including genes involved in ribosome biogenesis and metabolic and immune process that may be reflective of both adaptation to polar, planktonic environments as well as the complex life history of the salps. Finally, we performed an initial survey of small RNAs, revealing the presence of known, conserved miRNAs, as well as novel miRNA genes; unique piRNAs; and mature miRNA signatures for varying developmental stages. Collectively, these

  10. 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.

  11. 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.

  12. Advective pathways near the tip of the Antarctic Peninsula: Trends, variability and ecosystem implications

    Science.gov (United States)

    Renner, Angelika H. H.; Thorpe, Sally E.; Heywood, Karen J.; Murphy, Eugene J.; Watkins, Jon L.; Meredith, Michael P.

    2012-05-01

    Pathways and rates of ocean flow near the Antarctic Peninsula are strongly affected by frontal features, forcings from the atmosphere and the cryosphere. In the surface mixed layer, the currents advect material from the northwestern Weddell Sea on the eastern side of the Peninsula around the tip of the Peninsula to its western side and into the Scotia Sea, connecting populations of Antarctic krill (Euphausia superba) and supporting the ecosystem of the region. Modelling of subsurface drifters using a particle tracking algorithm forced by the velocity fields of a coupled sea ice-ocean model (ORCA025-LIM2) allows analysis of the seasonal and interannual variability of drifter pathways over 43 years. The results show robust and persistent connections from the Weddell Sea both to the west into the Bellingshausen Sea and across the Scotia Sea towards South Georgia, reproducing well the observations. The fate of the drifters is sensitive to their deployment location, in addition to other factors. From the shelf of the eastern Antarctic Peninsula, the majority enter the Bransfield Strait and subsequently the Bellingshausen Sea. When originating further offshore over the deeper Weddell Sea, drifters are more likely to cross the South Scotia Ridge and reach South Georgia. However, the wind field east and southeast of Elephant Island, close to the tip of the Peninsula, is crucial for the drifter trajectories and is highly influenced by the Southern Annular Mode (SAM). Increased advection and short travel times to South Georgia, and reduced advection to the western Antarctic Peninsula can be linked to strong westerlies, a signature of the positive phase of the SAM. The converse is true for the negative phase. Strong westerlies and shifts of ocean fronts near the tip of the Peninsula that are potentially associated with both the SAM and the El Niño-Southern Oscillation restrict the connection from the Weddell Sea to the west, and drifters then predominantly follow the open

  13. Recruitment, growth and mortality of an Antarctic hexactinellid sponge, Anoxycalyx joubini.

    Directory of Open Access Journals (Sweden)

    Paul K Dayton

    Full Text Available Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future.

  14. 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.

  15. 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.

  16. The Impact of Warm Pool El Nino Events on Antarctic Ozone

    Science.gov (United States)

    Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.

    2011-01-01

    Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a warming of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN events as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN events with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN events and the second set representing neutral ENSO events, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN events on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.

  17. Personal care products and steroid hormones in the Antarctic coastal environment associated with two Antarctic research stations, McMurdo Station and Scott Base.

    Science.gov (United States)

    Emnet, Philipp; Gaw, Sally; Northcott, Grant; Storey, Bryan; Graham, Lisa

    2015-01-01

    Pharmaceutical and personal care products (PPCPs) are a major source of micropollutants to the aquatic environment. Despite intense research on the fate and effects of PPCPs in temperate climates, there is a paucity of data on their presence in polar environments. This study reports the presence of selected PPCPs in sewage effluents from two Antarctic research stations, the adjacent coastal seawater, sea ice, and biota. Sewage effluents contained bisphenol-A, ethinylestradiol, estrone, methyl triclosan, octylphenol, triclosan, and three UV-filters. The maximum sewage effluent concentrations of 4-methyl-benzylidene camphor, benzophenone-1, estrone, ethinylestradiol, and octylphenol exceeded concentrations previously reported. Coastal seawaters contained bisphenol-A, octylphenol, triclosan, three paraben preservatives, and four UV-filters. The sea ice contained a similar range and concentration of PPCPs as the seawater. Benzophenone-3 (preferential accumulation in clams), estradiol, ethinylestradiol, methyl paraben (preferential accumulation in fish, with concentrations correlating negatively with fillet size), octylphenol, and propyl paraben were detected in biota samples. PPCPs were detected in seawater and biota at distances up to 25 km from the research stations WWTP discharges. Sewage effluent discharges and disposal of raw human waste through sea ice cracks have been identified as sources of PPCPs to Antarctic coastal environments. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. 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.

  19. 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.

  20. Metal complexation capacity of Antarctic lacustrine sediments.

    Science.gov (United States)

    Alberti, Giancarla; Mussi, Matteo; Quattrini, Federico; Pesavento, Maria; Biesuz, Raffaela

    2018-04-01

    The purpose of this study is to implement a work that is a part of a project funded by the Italian National Antarctic Research Program (PNRA, Piano Nazionale di Ricerche in Antartide) within the main thematic focus "Chemical Contamination-Global Change". This research was devoted to detect and characterize micro and nano components with strong complexing capability towards metal ions at trace level in sea water, lakes and lacustrine sediments, sampled during the XXII expedition of PNRA. In particular, in the present work, the sorption complexation capacity of an Antarctic lacustrine sediments toward Cu(II) and Pb(II) is described. The characterization of the sorption was undertaken, studying kinetics and isotherm profiles. The lake here considered is Tarn Flat in the area of Terra Nova Bay. The sorption equilibria of Cu(II) and Pb(II) on the lacustrine sediments were reached in about 10 h, and they were best modelled by the Langmuir equation. Preliminary, to establish if the data here obtained were consistent with those reported for the same area in other expeditions, a common multivariate techniques, namely the principal component analysis (PCA), was applied and finally the consistency of the data has been confirmed. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. 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.

  2. Atmospheric and oceanic impacts of Antarctic glaciation across the Eocene-Oligocene transition.

    Science.gov (United States)

    Kennedy, A T; Farnsworth, A; Lunt, D J; Lear, C H; Markwick, P J

    2015-11-13

    The glaciation of Antarctica at the Eocene-Oligocene transition (approx. 34 million years ago) was a major shift in the Earth's climate system, but the mechanisms that caused the glaciation, and its effects, remain highly debated. A number of recent studies have used coupled atmosphere-ocean climate models to assess the climatic effects of Antarctic glacial inception, with often contrasting results. Here, using the HadCM3L model, we show that the global atmosphere and ocean response to growth of the Antarctic ice sheet is sensitive to subtle variations in palaeogeography, using two reconstructions representing Eocene and Oligocene geological stages. The earlier stage (Eocene; Priabonian), which has a relatively constricted Tasman Seaway, shows a major increase in sea surface temperature over the Pacific sector of the Southern Ocean in response to the ice sheet. This response does not occur for the later stage (Oligocene; Rupelian), which has a more open Tasman Seaway. This difference in temperature response is attributed to reorganization of ocean currents between the stages. Following ice sheet expansion in the earlier stage, the large Ross Sea gyre circulation decreases in size. Stronger zonal flow through the Tasman Seaway allows salinities to increase in the Ross Sea, deep-water formation initiates and multiple feedbacks then occur amplifying the temperature response. This is potentially a model-dependent result, but it highlights the sensitive nature of model simulations to subtle variations in palaeogeography, and highlights the need for coupled ice sheet-climate simulations to properly represent and investigate feedback processes acting on these time scales. © 2015 The Author(s).

  3. 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

  4. Constraining the Antarctic contribution to global sea-level change: ANDRILL and beyond

    Science.gov (United States)

    Naish, Timothy

    2016-04-01

    Observations, models and paleoclimate reconstructions suggest that Antarctica's marine-based ice sheets behave in an unstable manner with episodes of rapid retreat in response to warming climate. Understanding the processes involved in this "marine ice sheet instability" is key for improving estimates of Antarctic ice sheet contribution to future sea-level rise. Another motivating factor is that far-field sea-level reconstructions and ice sheet models imply global mean sea level (GMSL) was up to 20m and 10m higher, respectively, compared with present day, during the interglacials of the warm Pliocene (~4-3Ma) and Late Pleistocene (at ~400ka and 125ka). This was when atmospheric CO2 was between 280 and 400ppm and global average surface temperatures were 1 to 3°C warmer, suggesting polar ice sheets are highly sensitive to relatively modest increases in climate forcing. Such magnitudes of GMSL rise not only require near complete melt of the Greenland Ice Sheet and the West Antarctic Ice Sheet, but a substantial retreat of marine-based sectors of East Antarctic Ice Sheet. Recent geological drilling initiatives on the continental margin of Antarctica from both ship- (e.g. IODP; International Ocean Discovery Program) and ice-based (e.g. ANDRILL/Antarctic Geological Drilling) platforms have provided evidence supporting retreat of marine-based ice. However, without direct access through the ice sheet to archives preserved within sub-glacial sedimentary basins, the volume and extent of ice sheet retreat during past interglacials cannot be directly constrained. Sediment cores have been successfully recovered from beneath ice shelves by the ANDRILL Program and ice streams by the WISSARD (Whillans Ice Stream Sub-glacial Access Research Drilling) Project. Together with the potential of the new RAID (Rapid Access Ice Drill) initiative, these demonstrate the technological feasibility of accessing the subglacial bed and deeper sedimentary archives. In this talk I will outline the

  5. 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.

  6. 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%.

  7. Magnetic Signature Analysis & Validation System

    National Research Council Canada - National Science Library

    Vliet, Scott

    2001-01-01

    The Magnetic Signature Analysis and Validation (MAGSAV) System is a mobile platform that is used to measure, record, and analyze the perturbations to the earth's ambient magnetic field caused by object such as armored vehicles...

  8. 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...

  9. Searching for eukaryotic life preserved in Antarctic permafrost

    DEFF Research Database (Denmark)

    Zucconi, L.; Selbmann, L.; Buzzini, P.

    2012-01-01

    Fungi and yeasts isolated in pure culture from Antarctic permafrost collected at different depths in the McMurdo Dry Valleys were identified with cultural, physiological and molecular methods. Fungi belonged to the genera Penicillium, Eurotium, Cladosporium, Alternaria, Engyodonthium, Aureobasidium...

  10. STRATEGIES AND KINETICS OF PHOTOACCLIMATION IN 3 ANTARCTIC NANOPHYTOFLAGELLATES

    NARCIS (Netherlands)

    BUMA, AGJ; NOORDELOOS, AAM; LARSEN, J

    Three Antarctic nanophytoflagellates (two cryptophyte species and a Pyramimonas sp.) were compared for their capacity to photoacclimate and for their kinetic responses in changing photic environments. Division rate, cell size, cellular fluorescence, and chlorophyll a content were measured during

  11. 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...

  12. 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

  13. German Antarctic Receiving Station (GARS) O'Higgins

    Science.gov (United States)

    Neidhardt, Alexander; Ploetz, Christian; Kluegel, Thomas

    2013-01-01

    In 2012, the German Antarctic Receiving Station (GARS) O'Higgins contributed to the IVS observing program with four observation sessions. Maintenance and upgrades were made, and a new replacement dewar is under construction in the observatory at Yebes, Spain.

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

    Directory of Open Access Journals (Sweden)

    A. S. Gardner

    2018-02-01

    Full Text Available 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 < 10 m yr−1, resulting from multiple overlapping image pairs acquired during 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.

  15. Extensive lake sediment coring survey on Sub-Antarctic Indian Ocean Kerguelen Archipelago (French Austral and Antarctic Lands)

    Science.gov (United States)

    Arnaud, Fabien; Fanget, Bernard; Malet, Emmanuel; Poulenard, Jérôme; Støren, Eivind; Leloup, Anouk; Bakke, Jostein; Sabatier, Pierre

    2016-04-01

    Recent paleo-studies revealed climatic southern high latitude climate evolution patterns that are crucial to understand the global climate evolution(1,2). Among others the strength and north-south shifts of westerlies wind appeared to be a key parameter(3). However, virtually no lands are located south of the 45th South parallel between Southern Georgia (60°W) and New Zealand (170°E) precluding the establishment of paleoclimate records of past westerlies dynamics. Located around 50°S and 70°E, lost in the middle of the sub-Antarctic Indian Ocean, Kerguelen archipelago is a major, geomorphologically complex, land-mass that is covered by hundreds lakes of various sizes. It hence offers a unique opportunity to reconstruct past climate and environment dynamics in a region where virtually nothing is known about it, except the remarkable recent reconstructions based on a Lateglacial peatbog sequence(4). During the 2014-2015 austral summer, a French-Norwegian team led the very first extensive lake sediment coring survey on Kerguelen Archipelago under the umbrella of the PALAS program supported by the French Polar Institute (IPEV). Two main areas were investigated: i) the southwest of the mainland, so-called Golfe du Morbihan, where glaciers are currently absent and ii) the northernmost Kerguelen mainland peninsula so-called Loranchet, where cirque glaciers are still present. This double-target strategy aims at reconstructing various independent indirect records of precipitation (glacier advance, flood dynamics) and wind speed (marine spray chemical species, wind-borne terrigenous input) to tackle the Holocene climate variability. Despite particularly harsh climate conditions and difficult logistics matters, we were able to core 6 lake sediment sites: 5 in Golfe du Morbihan and one in Loranchet peninsula. Among them two sequences taken in the 4km-long Lake Armor using a UWITEC re-entry piston coring system by 20 and 100m water-depth (6 and 7m-long, respectively). One

  16. 21 CFR 11.50 - Signature manifestations.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Signature manifestations. 11.50 Section 11.50 Food... RECORDS; ELECTRONIC SIGNATURES Electronic Records § 11.50 Signature manifestations. (a) Signed electronic...: (1) The printed name of the signer; (2) The date and time when the signature was executed; and (3...

  17. 76 FR 30542 - Adult Signature Services

    Science.gov (United States)

    2011-05-26

    ... POSTAL SERVICE 39 CFR Part 111 Adult Signature Services AGENCY: Postal Service\\TM\\. ACTION: Final..., Domestic Mail Manual (DMM[supreg]) 503.8, to add a new extra service called Adult Signature. This new service has two available options: Adult Signature Required and Adult Signature Restricted Delivery. DATES...

  18. 1 CFR 18.7 - Signature.

    Science.gov (United States)

    2010-01-01

    ... 1 General Provisions 1 2010-01-01 2010-01-01 false Signature. 18.7 Section 18.7 General Provisions... PREPARATION AND TRANSMITTAL OF DOCUMENTS GENERALLY § 18.7 Signature. The original and each duplicate original... stamped beneath the signature. Initialed or impressed signatures will not be accepted. Documents submitted...

  19. Attribute-Based Digital Signature System

    NARCIS (Netherlands)

    Ibraimi, L.; Asim, Muhammad; Petkovic, M.

    2011-01-01

    An attribute-based digital signature system comprises a signature generation unit (1) for signing a message (m) by generating a signature (s) based on a user secret key (SK) associated with a set of user attributes, wherein the signature generation unit (1) is arranged for combining the user secret

  20. 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

  1. Evaluating Potential Tipping Points of Antarctic basins

    Science.gov (United States)

    Durand, G.; Sainan, S.; Pattyn, F.; Jourdain, N.

    2017-12-01

    Antarctica is currently loosing mass and its forthcoming contribution to sea-level rise could substantially increase during the coming centuries. This is essentially due to geometrical constraints, i.e., in regions where grounded ice lies on a bedrock below sea-level sloping down towards the interior of the ice sheet (retrograde slope). For such a configuration the ice sheet is considered potentially unstable, as suggested by theory. However, recent observations on accelerated grounding-line retreat and new insights in modeling Pine Island and Thwaites glaciers give evidence that such self-sustained retreat, called marine ice sheet instability (MISI), has already been on its way. Although West Antarctica appears to be the most vulnerable region for MISI occurrence, similar topographic configurations are also observed in East Antarctica, in the Wilkes Basin in particular. Therefore, evaluating the MISI potential at a pan-Antarctic scale is becoming a priority. Here, using the f.ETISh ice sheet model, an ensemble of simulations of the entire contemporary Antarctic ice sheet has been carried out. In particular, we investigate the debuttressing of ice shelves required to initiate MISI for each coastal region around Antarctica by forcing the model with realistic sub-shelf melt pulses of varying duration and amplitude. We further identify the currently grounded areas where the outlet glaciers could hardly stabilize, the Amundsen Sea Sector being the more prone to large self-sustained retreats. On the contrary, the ability of Cook and Ninnis ice shelves to recover after large perturbations and enough buttress upstream outlet glaciers tends to limit self-sustained retreat of the sector. For each basin, rates of contribution to sea-level rise are discussed together with the RCPs and time when tipping points could be reached and MISI triggered.

  2. Antarctic Martian Meteorites at Johnson Space Center

    Science.gov (United States)

    Funk, R. C.; Satterwhite, C. E.; Righter, K.; Harrington, R.

    2018-01-01

    This past year marked the 40th anniversary of the first Martian meteorite found in Antarctica by the ANSMET Antarctic Search for Meteorites) program, ALH 77005. Since then, an additional 14 Martian meteorites have been found by the ANSMET program making for a total of 15 Martian meteorites in the U. S. Antarctic meteorite collection at Johnson Space Center (JSC). Of the 15 meteorites, some have been paired so the 15 meteorites actually represent a total of approximately 9 separate samples. The first Martian meteorite found by ANSMET was ALH 77005 (482.500 g), a lherzolitic shergottite. When collected, this meteorite was split as a part of the joint expedition with the National Institute of Polar Research (NIPR) Japan. Originally classified as an "achondrite-unique", it was re-classified as a Martian lherzolitic shergottite in 1982. This meteorite has been allocated to 137 scientists for research and there are 180.934 g remaining at JSC. Two years later, one of the most significant Martian meteorites of the collection at JSC was found at Elephant Moraine, EET 79001 (7942.000 g), a shergottite. This meteorite is the largest in the Martian collection at JSC and was the largest stony meteorite sample collected during the 1979 season. In addition to its size, this meteorite is of particular interest because it contains a linear contact separating two different igneous lithologies, basaltic and olivine-phyric. EET 79001 has glass inclusions that contain noble gas and nitrogen compositions that are proportionally identical to the Martian atmosphere, as measured by the Viking spacecraft. This discovery helped scientists to identify where the "SNC" meteorite suite had originated, and that we actually possessed Martian samples. This meteorite has been allocated to 205 scientists for research and 5,298.435 g of sample is available.

  3. Absorption of ultraviolet radiation by antarctic phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Vernet, M.; Mitchell, B.G. (Univ. of California-San Diego, La Jolla (United States))

    1990-01-09

    Antarctic phytoplankton contain UV-absorbing compounds that may block damaging radiation. Compounds that absorb from 320-340 nm were observed in spectral absorption of both particulates and in methanol extracts of the particulates. The decrease in the total concentration of these UV compounds with respect to chlorophyll a, as measured by the ratio of in vitro absorption at 335 nm to absorption at 665 nm is variable and decreases with depth. We observed up to 5-fold decrease in this ratio for samples within the physically mixes surface layer. The absorption of UV radiation in methanol extracts, which peaks from 320 to 340 nm, may be composed of several compounds. Shifts in peak absorption with depth (for example, from 331 nm at surface to 321 nm at 75 m), may be interpreted as a change in composition. Ratios of protective yellow xanthophylls (diadinoxanthin + diatoxanthin) to photosynthetic fucoxanthin-like pigments have highest values in surface waters. As these pigments also absorb in the near UV, their function might extend to protection as well as utilization of UV radiation for photosynthesis. We document strong absorption in the UV from 320-330 nm for Antarctic marine particulates. Below this region of the solar energy spectrum, absolute energy levels of incident radiation drop off dramatically. Only wavelengths shorter than about 320 nm will be significantly enhanced due to ozone depletion. If the absorption we observed serves a protective role for phytoplankton photosynthesis, it appears the peak band is in the region where solar energy increases rapidly, and not in the region where depletion would cause significant variations in absolute flux.

  4. 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.

  5. Antarctic contribution to sea level rise observed by GRACE with improved GIA correction

    Science.gov (United States)

    Ivins, Erik R.; James, Thomas S.; Wahr, John; Schrama, Ernst J. O.; Landerer, Felix W.; Simon, Karen M.

    2013-06-01

    Antarctic volume changes during the past 21 thousand years are smaller than previously thought, and here we construct an ice sheet history that drives a forward model prediction of the glacial isostatic adjustment (GIA) gravity signal. The new model, in turn, should give predictions that are constrained with recent uplift data. The impact of the GIA signal on a Gravity Recovery and Climate Experiment (GRACE) Antarctic mass balance estimate depends on the specific GRACE analysis method used. For the method described in this paper, the GIA contribution to the apparent surface mass change is re-evaluated to be +55±13 Gt/yr by considering a revised ice history model and a parameter search for vertical motion predictions that best fit the GPS observations at 18 high-quality stations. Although the GIA model spans a range of possible Earth rheological structure values, the data are not yet sufficient for solving for a preferred value of upper and lower mantle viscosity nor for a preferred lithospheric thickness. GRACE monthly solutions from the Center for Space Research Release 04 (CSR-RL04) release time series from January 2003 to the beginning of January 2012, uncorrected for GIA, yield an ice mass rate of +2.9± 29 Gt/yr. The new GIA correction increases the solved-for ice mass imbalance of Antarctica to -57±34 Gt/yr. The revised GIA correction is smaller than past GRACE estimates by about 50 to 90 Gt/yr. The new upper bound to the sea level rise from the Antarctic ice sheet, averaged over the time span 2003.0-2012.0, is about 0.16±0.09 mm/yr.

  6. Water masses transform at mid-depths over the Antarctic Continental Slope

    Science.gov (United States)

    Mead Silvester, Jess; Lenn, Yueng-Djern; Polton, Jeffrey; Phillips, Helen E.; Morales Maqueda, Miguel

    2017-04-01

    The Meridional Overturning Circulation (MOC) controls the oceans' latitudinal heat distribution, helping to regulate the Earth's climate. The Southern Ocean is the primary place where cool, deep waters return to the surface to complete this global circulation. While water mass transformations intrinsic to this process predominantly take place at the surface following upwelling, recent studies implicate vertical mixing in allowing transformation at mid-depths over the Antarctic continental slope. We deployed an EM-Apex float near Elephant Island, north of the Antarctic Peninsula's tip, to profile along the slope and use potential vorticity to diagnose observed instabilities. The float captures direct heat exchange between a lens of Upper Circumpolar Deep Water (UCDW) and surrounding Lower Circumpolar Deep Waters (LCDW) at mid-depths and over the course of several days. Heat fluxes peak across the top and bottom boundaries of the UCDW lens and peak diffusivities across the bottom boundary are associated with shear instability. Estimates of diffusivity from shear-strain finestructure parameterisation and heat fluxes are found to be in reasonable agreement. The two-dimensional Ertel potential vorticity is elevated both inside the UCDW lens and along its bottom boundary, with a strong contribution from the shear term in these regions and instabilities are associated with gravitational and symmetric forcing. Thus, shear instabilities are driving turbulent mixing across the lower boundary between these two water masses, leading to the observed heat exchange and transformation at mid-depths over the Antarctic continental slope. This has implications for our understanding of the rates of upwelling and ocean-atmosphere exchanges of heat and carbon at this critical location.

  7. (Pre-) calibration of a Reduced Complexity Model of the Antarctic Contribution to Sea-level Changes

    Science.gov (United States)

    Ruckert, K. L.; Guan, Y.; Shaffer, G.; Forest, C. E.; Keller, K.

    2015-12-01

    (Pre-) calibration of a Reduced Complexity Model of the Antarctic Contribution to Sea-level ChangesKelsey L. Ruckert1*, Yawen Guan2, Chris E. Forest1,3,7, Gary Shaffer 4,5,6, and Klaus Keller1,7,81 Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania, USA 2 Department of Statistics, The Pennsylvania State University, University Park, Pennsylvania, USA 3 Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania, USA 4 GAIA_Antarctica, University of Magallanes, Punta Arenas, Chile 5 Center for Advanced Studies in Arid Zones, La Serena, Chile 6 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark 7 Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, USA 8 Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA * Corresponding author. E-mail klr324@psu.eduUnderstanding and projecting future sea-level changes poses nontrivial challenges. Sea-level changes are driven primarily by changes in the density of seawater as well as changes in the size of glaciers and ice sheets. Previous studies have demonstrated that a key source of uncertainties surrounding sea-level projections is the response of the Antarctic ice sheet to warming temperatures. Here we calibrate a previously published and relatively simple model of the Antarctic ice sheet over a hindcast period from the last interglacial period to the present. We apply and compare a range of (pre-) calibration methods, including a Bayesian approach that accounts for heteroskedasticity. We compare the model hindcasts and projections for different levels of model complexity and calibration methods. We compare the projections with the upper bounds from previous studies and find our projections have a narrower range in 2100. Furthermore we discuss the implications for the design of climate risk management strategies.

  8. Glacial morphology and depositional sequences of the Antarctic Continental Shelf

    Science.gov (United States)

    ten Brink, Uri S.; Schneider, Christopher

    1995-01-01

    Proposes a simple model for the unusual depositional sequences and morphology of the Antarctic continental shelf. It considers the regional stratal geometry and the reversed morphology to be principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the ice grounding line. The model offers several guidelines for stratigraphic interpretation of the Antarctic shelf and a Northern Hemisphere shelf, both of which were subject to many glacial advances and retreats. -Authors

  9. Leadership in politics and science within the Antarctic Treaty

    OpenAIRE

    John R. Dudeney; David W.H. Walton

    2012-01-01

    For over 50 years the Antarctic has been governed through the Antarctic Treaty, an international agreement now between 49 nations of whom 28 Consultative Parties (CPs) undertake the management role. Ostensibly, these Parties have qualified for their position on scientific grounds, though diplomacy also plays a major role. This paper uses counts of policy papers and science publications to assess the political and scientific outputs of all CPs over the last 18 years. We show that a subset of t...

  10. Wind profile radar for study of Antarctic air circulation

    International Nuclear Information System (INIS)

    Ragaini, E.; Sarango, M.F.; Vasquez, E.H.

    1992-01-01

    After a brief discussion of meteorological methods used in the Antarctic, the paper gives an outline of a coordinated international research project whose objective is to set up a wind profiler radar station that would give meteorologists information regarding Antarctic atmospheric dynamics useful in their investigation of the causes and effects of the hole in the ozone layer. The radar instrumentation is to provide continuous readings of wind velocity at varying altitudes above the polar continent

  11. 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

  12. Quantum messages with signatures forgeable in arbitrated quantum signature schemes

    International Nuclear Information System (INIS)

    Kim, Taewan; Choi, Jeong Woon; Jho, Nam-Su; Lee, Soojoon

    2015-01-01

    Even though a method to perfectly sign quantum messages has not been known, the arbitrated quantum signature scheme has been considered as one of the good candidates. However, its forgery problem has been an obstacle to the scheme becoming a successful method. In this paper, we consider one situation, which is slightly different from the forgery problem, that we use to check whether at least one quantum message with signature can be forged in a given scheme, although all the messages cannot be forged. If there are only a finite number of forgeable quantum messages in the scheme, then the scheme can be secured against the forgery attack by not sending forgeable quantum messages, and so our situation does not directly imply that we check whether the scheme is secure against the attack. However, if users run a given scheme without any consideration of forgeable quantum messages, then a sender might transmit such forgeable messages to a receiver and in such a case an attacker can forge the messages if the attacker knows them. Thus it is important and necessary to look into forgeable quantum messages. We show here that there always exists such a forgeable quantum message-signature pair for every known scheme with quantum encryption and rotation, and numerically show that there are no forgeable quantum message-signature pairs that exist in an arbitrated quantum signature scheme. (paper)

  13. 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/.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. Glacial History of Southernmost South America and Implications for Movement of the Westerlies and Antarctic Frontal Zone

    Science.gov (United States)

    Kaplan, M. R.; Fogwill, C. J.; Hulton, N. R.; Sugden, D. E.; Peter, K. W.

    2004-12-01

    The ~1 Myr glacial geologic record in southern South American is one of the few available terrestrial paleoclimate proxies at orbital and suborbital time scales in the middle latitudes of the Southern Hemisphere. Presently, southernmost Patagonia lies about 3\\deg north of the Antarctic frontal zone and within the middle latitude westerlies and the climate is controlled by the surrounding maritime conditions. Thus, the long-term glacial record provides insight into the history of climatic boundaries over the middle and high latitude southern ocean, including the upwind SE Pacific Ocean, tectonic-glacial evolution of the Andes, and global climate. To date, cosmogenic nuclide and 14C dating have focused on glacial fluctuations between 51 and 53\\deg S (Torres del Paine to northern Tierra del Fuego) during the last glacial cycle, including the late glacial period. At least 4 advances occurred between ca. 25 and 17 ka, with the maximum expansion of ice ca. 25-24 ka. Major deglaciation commenced after ca. 17.5 ka, which was interrupted by a major glacial-climate event ca. 14-12 ka. Modelling experiments suggest that the ice mass needed to form the glacial maximum moraines required about a 6\\deg cooling and a slight drying relative to the present. Such a fundamental temperature reduction, despite high summer isolation, strongly suggests northward movement of the westerlies and the polar front on millennial timescales. The Patagonian record also indicates that on orbital timescales equatorward movement of climate boundaries and glacial growth was in phase with major Northern Hemisphere ice volume change, despite high local summer insolation. At suborbital timescales, the picture is more complex. While major facets of the last glacial maximum appear to be in phase between the hemispheres, at least some late glacial events may be in step with Antarctic climate change. Present and future research will further constrain the timing of glacial events over the last 1 Myr and

  19. 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

    2017-12-13

    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.

  20. 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

  1. Development of a Regional Glycerol Dialkyl Glycerol Tetraether (GDGT) - Temperature Calibration for Antarctic and sub-Antarctic Lakes

    Science.gov (United States)

    Roberts, S. J.; Foster, L. C.; Pearson, E. J.; Steve, J.; Hodgson, D.; Saunders, K. M.; Verleyen, E.

    2016-12-01

    Temperature calibration models based on the relative abundances of sedimentary glycerol dialkyl glycerol tetraethers (GDGTs) have been used to reconstruct past temperatures in both marine and terrestrial environments, but have not been widely applied in high latitude environments. This is mainly because the performance of GDGT-temperature calibrations at lower temperatures and GDGT provenance in many lacustrine settings remains uncertain. To address these issues, we examined surface sediments from 32 Antarctic, sub-Antarctic and Southern Chilean lakes. First, we quantified GDGT compositions present and then investigated modern-day environmental controls on GDGT composition. GDGTs were found in all 32 lakes studied. Branched GDGTs (brGDGTs) were dominant in 31 lakes and statistical analyses showed that their composition was strongly correlated with mean summer air temperature (MSAT) rather than pH, conductivity or water depth. Second, we developed the first regional brGDGT-temperature calibration for Antarctic and sub-Antarctic lakes based on four brGDGT compounds (GDGT-Ib, GDGT-II, GDGT-III and GDGT-IIIb). Of these, GDGT-IIIb proved particularly important in cold lacustrine environments. Our brGDGT-Antarctic temperature calibration dataset has an improved statistical performance at low temperatures compared to previous global calibrations (r2=0.83, RMSE=1.45°C, RMSEP-LOO=1.68°C, n=36 samples), highlighting the importance of basing palaeotemperature reconstructions on regional GDGT-temperature calibrations, especially if specific compounds lead to improved model performance. Finally, we applied the new Antarctic brGDGT-temperature calibration to two key lake records from the Antarctic Peninsula and South Georgia. In both, downcore temperature reconstructions show similarities to known Holocene warm periods, providing proof of concept for the new Antarctic calibration model.

  2. 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

  3. Impact of increasing antarctic glacial freshwater release on regional sea-ice cover in the Southern Ocean

    Science.gov (United States)

    Merino, Nacho; Jourdain, Nicolas C.; Le Sommer, Julien; Goosse, Hugues; Mathiot, Pierre; Durand, Gael

    2018-01-01

    The sensitivity of Antarctic sea-ice to increasing glacial freshwater release into the Southern Ocean is studied in a series of 31-year ocean/sea-ice/iceberg model simulations. Glaciological estimates of ice-shelf melting and iceberg calving are used to better constrain the spatial distribution and magnitude of freshwater forcing around Antarctica. Two scenarios of glacial freshwater forcing have been designed to account for a decadal perturbation in glacial freshwater release to the Southern Ocean. For the first time, this perturbation explicitly takes into consideration the spatial distribution of changes in the volume of Antarctic ice shelves, which is found to be a key component of changes in freshwater release. In addition, glacial freshwater-induced changes in sea ice are compared to typical changes induced by the decadal evolution of atmospheric states. Our results show that, in general, the increase in glacial freshwater release increases Antarctic sea ice extent. But the response is opposite in some regions like the coastal Amundsen Sea, implying that distinct physical mechanisms are involved in the response. We also show that changes in freshwater forcing may induce large changes in sea-ice thickness, explaining about one half of the total change due to the combination of atmospheric and freshwater changes. The regional contrasts in our results suggest a need for improving the representation of freshwater sources and their evolution in climate models.

  4. Interannual variation of the Antarctic Ice Sheet from a combined analysis of satellite gravimetry and altimetry data

    Science.gov (United States)

    Mémin, A.; Flament, T.; Alizier, B.; Watson, C.; Rémy, F.

    2015-07-01

    Assessment of the long term mass balance of the Antarctic Ice Sheet, and thus the determination of its contribution to sea level rise, requires an understanding of interannual variability and associated causal mechanisms. We performed a combined analysis of surface-mass and elevation changes using data from the GRACE and Envisat satellite missions, respectively. Using empirical orthogonal functions and singular value decompositions of each data set, we find a quasi 4.7-yr periodic signal between 08/2002 and 10/2010 that accounts for ∼ 15- 30% of the time variability of the filtered and detrended surface-mass and elevation data. Computation of the density of this variable mass load corresponds to snow or uncompacted firn. Changes reach maximum amplitude within the first 100 km from the coast where it contributes up to 30-35% of the annual rate of accumulation. Extending the analysis to 09/2014 using surface-mass changes only, we have found anomalies with a periodicity of about 4-6 yrs that circle the AIS in about 9-10 yrs. These properties connect the observed anomalies to the Antarctic Circumpolar Wave (ACW) which is known to affect several key climate variables, including precipitation. It suggests that variability in the surface-mass balance of the Antarctic Ice Sheet may also be modulated by the ACW.

  5. 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

  6. 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.

  7. Spatial structures in the heat budget of the Antarctic atmospheric boundary layer

    Directory of Open Access Journals (Sweden)

    W. J. van de Berg

    2008-01-01

    Full Text Available Output from the regional climate model RACMO2/ANT is used to calculate the heat budget of the Antarctic atmospheric boundary layer (ABL. The main feature of the wintertime Antarctic ABL is a persistent temperature deficit compared to the free atmosphere. The magnitude of this deficit is controlled by the heat budget. During winter, transport of heat towards the surface by turbulence and net longwave emission are the primary ABL cooling terms. These processes show horizontal spatial variability only on continental scales. Vertical and horizontal, i.e. along-slope, advection of heat are the main warming terms. Over regions with convex ice sheet topography, i.e. domes and ridges, warming by downward vertical advection is enhanced due to divergence of the ABL wind field. Horizontal advection balances excess warming caused by vertical advection, hence the temperature deficit in the ABL weakens over domes and ridges along the prevailing katabatic wind. Conversely, vertical advection is reduced in regions with concave topography, i.e. valleys, where the ABL temperature deficit enlarges along the katabatic wind. Along the coast, horizontal and vertical advection is governed by the inability of the large-scale circulation to adapt to small scale topographic features. Meso-scale topographic structures have thus a strong impact on the ABL winter temperature, besides latitude and surface elevation. During summer, this mechanism is much weaker, and the horizontal variability of ABL temperatures is smaller.

  8. Coherency Between Volume Transport in the Antarctic Circumpolar Current and Southern Hemisphere Winds

    Science.gov (United States)

    Makowski, Jessica; Chambers, Don; Bonin, Jennifer

    2013-04-01

    Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). The OBP observations from the Gravity Recovery and Climate Experiment (GRACE) will be used to calculate transport along the 150°E longitude choke point, between Antarctica and Australia. We will examine whether zonally averaged wind stress, wind stress curl, or local zonal winds are more coherent with zonal mass transport variability. Preliminary studies suggest that seasonal variation in transport across 150°E is more correlated with winds along and north of the northern front of the ACC: the Sub Tropical front (STF). It also appears that interannual variations in transport along 150°E are related to wind variations south of the STF and centered south of the Sub Antarctic Front (SAF). We have observed a strong anti-correlation across the SAF, in the Indian Ocean, which suggests wind stress curl may also be responsible for transport variations. Preliminary results will be presented.

  9. Microbial activity during a coastal phytoplankton bloom on the Western Antarctic Peninsula in late summer.

    Science.gov (United States)

    Alcamán-Arias, María E; Farías, Laura; Verdugo, Josefa; Alarcón-Schumacher, Tomás; Díez, Beatriz

    2018-05-01

    Phytoplankton biomass during the austral summer is influenced by freezing and melting cycles as well as oceanographic processes that enable nutrient redistribution in the West Antarctic Peninsula (WAP). Microbial functional capabilities, metagenomic and metatranscriptomic activities as well as inorganic 13C- and 15N-assimilation rates were studied in the surface waters of Chile Bay during two contrasting summer periods in 2014. Concentrations of Chlorophyll a (Chla) varied from 0.3 mg m-3 in February to a maximum of 2.5 mg m-3 in March, together with a decrease in nutrients; however, nutrients were never depleted. The microbial community composition remained similar throughout both sampling periods; however, microbial abundance and activity changed with Chla levels. An increased biomass of Bacillariophyta, Haptophyceae and Cryptophyceae was observed along with night-grazing activity of Dinophyceae and ciliates (Alveolates). During high Chla conditions, HCO3- uptake rates during daytime incubations increased 5-fold (>2516 nmol C L-1 d-1), and increased photosynthetic transcript numbers that were mainly associated with cryptophytes; meanwhile night time NO3- (>706 nmol N L-1 d-1) and NH4+ (41.7 nmol N L-1 d-1) uptake rates were 2- and 3-fold higher, respectively, due to activity from Alpha-/Gammaproteobacteria and Bacteroidetes (Flavobacteriia). Due to a projected acceleration in climate change in the WAP, this information is valuable for predicting the composition and functional changes in Antarctic microbial communities.

  10. Genetic diversity among populations of Antarctic springtails (Collembola) within the Mackay Glacier ecotone.

    Science.gov (United States)

    Beet, Clare R; Hogg, Ian D; Collins, Gemma E; Cowan, Don A; Wall, Diana H; Adams, Byron J

    2016-09-01

    Climate changes are likely to have major influences on the distribution and abundance of Antarctic terrestrial biota. To assess arthropod distribution and diversity within the Ross Sea region, we examined mitochondrial DNA (COI) sequences for three currently recognized species of springtail (Collembola) collected from sites in the vicinity, and to the north of, the Mackay Glacier (77°S). This area acts as a transition between two biogeographic regions (northern and southern Victoria Land). We found populations of highly divergent individuals (5%-11.3% intraspecific sequence divergence) for each of the three putative springtail species, suggesting the possibility of cryptic diversity. Based on molecular clock estimates, these divergent lineages are likely to have been isolated for 3-5 million years. It was during this time that the Western Antarctic Ice Sheet (WAIS) was likely to have completely collapsed, potentially facilitating springtail dispersal via rafting on running waters and open seaways. The reformation of the WAIS would have isolated newly established populations, with subsequent dispersal restricted by glaciers and ice-covered areas. Given the currently limited distributions for these genetically divergent populations, any future changes in species' distributions can be easily tracked through the DNA barcoding of springtails from within the Mackay Glacier ecotone.

  11. 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.

  12. 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.

  13. 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

    2014-01-01

    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. PMID:25505370

  14. The Antarctic Centennial Oscillation: A Natural Paleoclimate Cycle in the Southern Hemisphere That Influences Global Temperature

    Directory of Open Access Journals (Sweden)

    W. Jackson Davis

    2018-01-01

    Full Text Available We report a previously-unexplored natural temperature cycle recorded in ice cores from Antarctica—the Antarctic Centennial Oscillation (ACO—that has oscillated for at least the last 226 millennia. Here we document the properties of the ACO and provide an initial assessment of its role in global climate. We analyzed open-source databases of stable isotopes of oxygen and hydrogen as proxies for paleo-temperatures. We find that centennial-scale spectral peaks from temperature-proxy records at Vostok over the last 10,000 years occur at the same frequencies (±2.4% in three other paleoclimate records from drill sites distributed widely across the East Antarctic Plateau (EAP, and >98% of individual ACOs evaluated at Vostok match 1:1 with homologous cycles at the other three EAP drill sites and conversely. Identified ACOs summate with millennial periodicity to form the Antarctic Isotope Maxima (AIMs known to precede Dansgaard-Oeschger (D-O oscillations recorded in Greenland ice cores. Homologous ACOs recorded at the four EAP drill sites during the last glacial maximum appeared first at lower elevations nearest the ocean and centuries later on the high EAP, with latencies that exceed dating uncertainty >30-fold. ACO homologs at different drill sites became synchronous, however, during the warmer Holocene. Comparative spectral analysis suggests that the millennial-scale AIM cycle declined in period from 1500 to 800 years over the last 70 millennia. Similarly, over the last 226 millennia ACO repetition period (mean 352 years declined by half while amplitude (mean 0.67 °C approximately doubled. The period and amplitude of ACOs oscillate in phase with glacial cycles and related surface insolation associated with planetary orbital forces. We conclude that the ACO: encompasses at least the EAP; is the proximate source of D-O oscillations in the Northern Hemisphere; therefore affects global temperature; propagates with increased velocity as temperature

  15. 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.

  16. 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.

  17. Samarium-Neodymium model age and Geochemical (Sr-Nd) signature of a bedrock inclusion from lake Vostok accretion ice.

    Science.gov (United States)

    Delmonte, B.; Petit, J. R.; Michard, A.; Basile-Doelsch, I.; Lipenkov, V.

    2003-04-01

    We investigated properties of the basal ice from Vostok ice core as well as the sediment inclusions within the accreted ice. The Vostok ice core preserves climatic information for the last 420 kyrs down to 3310m depth, but below this depth the horizontal layers of the climatic record are disrupted by the glacier dynamics. From 3450 m to 3538 m depth thin bedrock particles, as glacial flour, are entrapped. Glacial flour is released in the northern area lake, where glacier mostly melts and contributes to sediment accumulation. In the southern area, close to Vostok station, the lake water freezes and the upstream glacial flour does not contribute to sedimentation. The accreted ice contains visible sediment inclusions down to 3608 m (accretion ice 1), while below this depth and likely down to the water interface (˜3750 m), the ice is clear (accretion ice 2). The fine inclusions (1-2mm in diameter) from Accretion Ice 1 mostly consist of fine clays and quartz aggregates and we suggest they are entrained into ice as the glacier floats over shallow depth bay then it grounds against a relief rise. Afterward the glacier freely floats over the deep lake before reaching Vostok, and accreted ice 2 is clean. Sm-Nd dating of one of two inclusions at 3570 m depth gives 1.88 (+/-0.13)Ga (DM model age), corresponding to 1.47 Ga (TCHUR), suggesting a Precambrian origin. Also the isotopic signature of such inclusion (87Sr/86Sr= 0.8232 and eNd= -16) and that of a second one (87Sr/86Sr= 0.7999 and eNd= -15) are coherent with the nature of an old continental shield. Sediments that may initially accumulate in the shallow bay prior the Antarctic glaciation, should have been eroded and exported out of the lake by the glacier movement, this assuming processes for ice accretion and for sediment entrapping operate since a long time. As the glacial flour from upstream does not contribute to sedimentation, sediments need to be renewed at the surface of the bedrock rising question about the way

  18. 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

  19. 78 FR 28000 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-05-13

    ... 1978 (Pub. L. 95-541), as amended by the Antarctic Science, Tourism and Conservation Act of 1996, has... facilities and equipment. Location Antarctic Peninsula region, ASPA 117-Avian Island, ASPA 128 Cape...

  20. 78 FR 54686 - Notice of Permit Applications Received under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-09-05

    ... the Antarctic Conservation Act of 1978 (Pub. L. 95-541), as amended by the Antarctic Science, Tourism... of the ongoing effort to monitor the spatial scale of human impacts in Antarctica. Samples taken near...

  1. Metal and antibiotic-resistance in psychrotrophic bacteria from Antarctic marine waters

    Digital Repository Service at National Institute of Oceanography (India)

    De; Nair, S.; LokaBharathi, P.A.; Chandramohan, D.

    In the wake of the findings that Antarctic krills concentrate heavy metals at ppm level, (Yamamoto et al., 1987), the Antarctic waters from the Indian side were examined for the incidence of metal and antibiotic-resistant bacteria during...

  2. 77 FR 50720 - Notice of Permit Modification Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2012-08-22

    ... Antarctic Conservation Act of 1978 (Pub. L. 95-541), as amended by the Antarctic Science, Tourism and..., bill and flipper dimensions taken, 3-5 feathers removed to confirm gender of the penguin, and have GPS...

  3. 78 FR 56743 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-09-13

    ... by the Antarctic Conservation Act of 1978 (Pub. L. 95-541), as amended by the Antarctic Science... measure ablation and GPS units to monitor the motion of the glacier. The GPR system will be moved...

  4. 77 FR 67407 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2012-11-09

    ... designation of certain animals and certain geographic areas a requiring special protection. The regulations establish such a permit system to designate Antarctic Specially Protected Areas. The applications received... NATIONAL SCIENCE FOUNDATION Notice of Permit Applications Received Under the Antarctic...

  5. 78 FR 56744 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-09-13

    ... requiring special protection. The regulations establish such a permit system to designate Antarctic... NATIONAL SCIENCE FOUNDATION Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978 AGENCY: National Science Foundation. ACTION: Notice of Permit Applications Received...

  6. 77 FR 38834 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2012-06-29

    ... requiring special protection. The regulations establish such a permit system to designate Antarctic... NATIONAL SCIENCE FOUNDATION Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978 AGENCY: National Science Foundation. ACTION: Notice of permit applications received...

  7. 78 FR 59728 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-09-27

    ... requiring special protection. The regulations establish such a permit system to designate Antarctic... NATIONAL SCIENCE FOUNDATION Notice of Permit Applications Received Under the Antarctic... Foundation (NSF) is required to publish a notice of permit applications received to conduct activities...

  8. Digital Signature Schemes with Complementary Functionality and Applications

    OpenAIRE

    S. N. Kyazhin

    2012-01-01

    Digital signature schemes with additional functionality (an undeniable signature, a signature of the designated confirmee, a signature blind, a group signature, a signature of the additional protection) and examples of their application are considered. These schemes are more practical, effective and useful than schemes of ordinary digital signature.

  9. Persistence of Antarctic polar stratospheric clouds

    Science.gov (United States)

    Mccormick, M. Patrick; Trepte, C. R.

    1988-01-01

    The persistence of Polar Stratospheric Clouds (PSCs) observed by the Stratospheric Aerosol Measurement (SAM) 2 satellite sensor over a 9-year period is compared and contrasted. Histograms of the SAM 2 1.0 micron extinction ratio data (aerosol extinction normalized by the molecular extinction) at an altitude of 18 km in the Antarctic have been generated for three 10-day periods in the month of September. Statistics for eight different years (1979 to 1982 and 1984 to 1987) are shown in separate panels for each figure. Since the SAM 2 system is a solar occultation experiment, observations are limited to the edge of the polar night and no measurements are made deep within the vortex where temperatures could be colder. For this reason, use is made of the NMC global gridded fields and the known temperature-extinction relationship to infer additional information on the occurrence and areal coverage of PSCs. Calculations of the daily areal coverage of the 195 K isotherm will be presented for this same period of data. This contour level lies in the range of the predicted temperature for onset of the Type 1 particle enhancement mode at 50 mb (Poole and McCormick, 1988b) and should indicate approximately when formation of the binary HNO3-H2O particles begins.

  10. Peripheral cold acclimatization in Antarctic scuba divers.

    Science.gov (United States)

    Bridgman, S A

    1991-08-01

    Peripheral acclimatization to cold in scuba divers stationed at the British Antarctic Survey's Signy Station was investigated during a year in Antarctica. Five divers and five non-diver controls underwent monthly laboratory tests of index finger immersion in cold water for 30 min. Index finger pulp temperature and time of onset of cold-induced vasodilatation (CIVD) were measured. Pain was recorded with verbal and numerical psychophysical subjective pain ratings. Average finger temperatures and median finger pain from 6-30 min of immersion, maximum finger temperatures during the first CIVD cycle, and finger temperatures at the onset of CIVD were calculated. Comparison of the variables recorded from divers and non-divers were performed with analysis of variance. No significant differences were found among the variables recorded from divers and non-divers. From a review of the literature, divers have responses typical of non-cold-adapted Caucasians. There is, therefore, no evidence that Signy divers peripherally acclimatized to cold. We suggest that these findings occur because either the whole body cooling which divers undergo inhibits peripheral acclimatization or because of insufficiently frequent or severe cold exposure while diving. Further basic studies on the duration, frequency and severity of cold exposure necessary to induce peripheral cold acclimatization are required before this question can be satisfactorily answered.

  11. The safety band of Antarctic ice shelves

    Science.gov (United States)

    Fürst, Johannes Jakob; Durand, Gaël; Gillet-Chaulet, Fabien; Tavard, Laure; Rankl, Melanie; Braun, Matthias; Gagliardini, Olivier

    2016-05-01

    The floating ice shelves along the seaboard of the Antarctic ice sheet restrain the outflow of upstream grounded ice. Removal of these ice shelves, as shown by past ice-shelf recession and break-up, accelerates the outflow, which adds to sea-level rise. A key question in predicting future outflow is to quantify the extent of calving that might precondition other dynamic consequences and lead to loss of ice-shelf restraint. Here we delineate frontal areas that we label as `passive shelf ice’ and that can be removed without major dynamic implications, with contrasting results across the continent. The ice shelves in the Amundsen and Bellingshausen seas have limited or almost no `passive’ portion, which implies that further retreat of current ice-shelf fronts will yield important dynamic consequences. This region is particularly vulnerable as ice shelves have been thinning at high rates for two decades and as upstream grounded ice rests on a backward sloping bed, a precondition to marine ice-sheet instability. In contrast to these ice shelves, Larsen C Ice Shelf, in the Weddell Sea, exhibits a large `passive’ frontal area, suggesting that the imminent calving of a vast tabular iceberg will be unlikely to instantly produce much dynamic change.

  12. Antarctic icebergs distributions 1992-2014

    Science.gov (United States)

    Tournadre, J.; Bouhier, N.; Girard-Ardhuin, F.; Rémy, F.

    2016-01-01

    Basal melting of floating ice shelves and iceberg calving constitute the two almost equal paths of freshwater flux between the Antarctic ice cap and the Southern Ocean. The largest icebergs (>100 km2) transport most of the ice volume but their basal melting is small compared to their breaking into smaller icebergs that constitute thus the major vector of freshwater. The archives of nine altimeters have been processed to create a database of small icebergs (law of slope -1.52 ± 0.32 close to the -3/2 laws observed and modeled for brittle fragmentation. The global volume of ice and its distribution between the ocean basins present a very strong interannual variability only partially explained by the number of large icebergs. Indeed, vast zones of the Southern Ocean free of large icebergs are largely populated by small iceberg drifting over thousands of kilometers. The correlation between the global small and large icebergs volumes shows that small icebergs are mainly generated by large ones breaking. Drifting and trapping by sea ice can transport small icebergs for long period and distances. Small icebergs act as an ice diffuse process along large icebergs trajectories while sea ice trapping acts as a buffer delaying melting.

  13. 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)

  14. Characterizing Resident Space Object Earthshine Signature Variability

    Science.gov (United States)

    Van Cor, Jared D.

    There are three major sources of illumination on objects in the near Earth space environment: Sunshine, Moonshine, and Earthshine. For objects in this environment (satellites, orbital debris, etc.) known as Resident Space Objects (RSOs), the sun and the moon have consistently small illuminating solid angles and can be treated as point sources; this makes their incident illumination easily modeled. The Earth on the other hand has a large illuminating solid angle, is heterogeneous, and is in a constant state of change. The objective of this thesis was to characterize the impact and variability of observed RSO Earthshine on apparent magnitude signatures in the visible optical spectral region. A key component of this research was creating Earth object models incorporating the reflectance properties of the Earth. Two Earth objects were created: a homogeneous diffuse Earth object and a time sensitive heterogeneous Earth object. The homogeneous diffuse Earth object has a reflectance equal to the average global albedo, a standard model used when modeling Earthshine. The time sensitive heterogeneous Earth object was created with two material maps representative of the dynamic reflectance of the surface of the earth, and a shell representative of the atmosphere. NASA's Moderate-resolution Imaging Spectroradiometer (MODIS) Earth observing satellite product libraries, MCD43C1 global surface BRDF map and MOD06 global fractional cloud map, were utilized to create the material maps, and a hybridized version of the Empirical Line Method (ELM) was used to create the atmosphere. This dynamic Earth object was validated by comparing simulated color imagery of the Earth to that taken by: NASAs Earth Polychromatic Imaging Camera (EPIC) located on the Deep Space Climate Observatory (DSCOVR), and by MODIS located on the Terra satellite. The time sensitive heterogeneous Earth object deviated from MODIS imagery by a spectral radiance root mean square error (RMSE) of +/-14.86 [watts/m. 2sr

  15. Levoglucosan indicates high levels of biomass burning aerosols over oceans from the Arctic to Antarctic.

    Science.gov (United States)

    Hu, Qi-Hou; Xie, Zhou-Qing; Wang, Xin-Ming; Kang, Hui; Zhang, Pengfei

    2013-11-01

    Biomass burning is known to affect air quality, global carbon cycle, and climate. However, the extent to which biomass burning gases/aerosols are present on a global scale, especially in the marine atmosphere, is poorly understood. Here we report the molecular tracer levoglucosan concentrations in marine air from the Arctic Ocean through the North and South Pacific Ocean to Antarctica during burning season. Levoglucosan was found to be present in all regions at ng/m(3) levels with the highest atmospheric loadings present in the mid-latitudes (30°-60° N and S), intermediate loadings in the Arctic, and lowest loadings in the Antarctic and equatorial latitudes. As a whole, levoglucosan concentrations in the Southern Hemisphere were comparable to those in the Northern Hemisphere. Biomass burning has a significant impact on atmospheric Hg and water-soluble organic carbon (WSOC) from pole-to-pole, with more contribution to WSOC in the Northern Hemisphere than in the Southern Hemisphere.

  16. Measuring Zonal Transport Variability of the Antarctic Circumpolar Current Using GRACE Ocean Bottom Pressure

    Science.gov (United States)

    Makowski, J.; Chambers, D. P.; Bonin, J. A.

    2012-12-01

    Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). Using OBP data from the JPL ECCO model and the Gravity Recovery and Climate Experiment (GRACE), we examine the zonal transport variability of the ACC integrated between the major fronts between 2003-2010. The JPL ECCO data are used to determine average front positions for the time period studies, as well as where transport is mainly zonal. Statistical analysis will be conducted to determine the uncertainty of the GRACE observations using a simulated data set. We will also begin looking at low frequency changes and how coherent transport variability is from region to region of the ACC. Correlations with bottom pressure south of the ACC and the average basin transports will also be calculated to determine the probability of using bottom pressure south of the ACC as a means for describing the ACC dynamics and transport.

  17. 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…

  18. 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.

  19. Quark-Gluon Plasma Signatures

    CERN Document Server

    Vogt, Ramona

    1998-01-01

    Aspects of quark-gluon plasma signatures that can be measured by CMS are discussed. First the initial conditions of the system from minijet production are introduced, including shadowing effects. Color screening of the Upsilon family is then presented, followed by energy loss effects on charm and bottom hadrons, high Pt jets and global observables.

  20. 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

  1. 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.

  2. 78 FR 41959 - Notice of Permit Modification Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2013-07-12

    ... Areas (ASPA) or involving Antarctic Flora and Fauna. Starting in 2013, all new permits issued for ASPA entry or involving Antarctic Flora and Flora require the permittee to submit an annual report to the... Specially Protected Areas (ASPA) or involving Antarctic Flora and Fauna issued prior to 2013 that require...

  3. 77 FR 41809 - Notice of Permit Applications Received Under the Antarctic Conservation Act of 1978

    Science.gov (United States)

    2012-07-16

    ..., Lockheed Martin IS&GS, Antarctic Support Contract, 7400 S. Tucson Way, Centennial, CO 80112-3938. Activity..., Antarctic Support Contract, 7400 S. Tucson Way, Centennial, CO 80112-3938. Activity for Which Permit Is.... Applicant: Celia Lang, Lockheed Martin IS&GS, Antarctic Support Contract, 7400 S. Tucson Way, Centennial, CO...

  4. Feasibility of Using Alternate Fuels in the U.S. Antarctic Program: Initial Assessment

    Science.gov (United States)

    2017-09-01

    Polar Programs. Morris, A. 2015a. Email communication. 21 April. Centennial , CO: Antarctic Support Contractor. ———. 2015b. Personal...communication. 19 May. Centennial , CO: Antarctic Support Contractor. ———. 2014. Email communication. 24 November. Centennial , CO: Antarctic Support

  5. Isolation and characterization of Campylobacter spp. from Antarctic fur seals (Arctocephalus gazella) at Deception Island, Antarctica.

    Science.gov (United States)

    García-Peña, F J; Pérez-Boto, D; Jiménez, C; San Miguel, E; Echeita, A; Rengifo-Herrera, C; García-Párraga, D; Ortega-Mora, L M; Pedraza-Díaz, S

    2010-09-01

    The presence of Campylobacter spp. was investigated in 41 Antarctic fur seals (Arctocephalus gazella) and 9 Weddell seals (Leptonychotes weddellii) at Deception Island, Antarctica. Infections were encountered in six Antarctic fur seals. The isolates, the first reported from marine mammals in the Antarctic region, were identified as Campylobacter insulaenigrae and Campylobacter lari.

  6. 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

     °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...

  7. 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)

  8. 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

  9. Can we observe the fronts of the Antarctic Circumpolar Current using GRACE OBP?

    Science.gov (United States)

    Makowski, J.; Chambers, D. P.; Bonin, J. A.

    2014-12-01

    The Antarctic Circumpolar Current (ACC) and the Southern Ocean remains one of the most undersampled regions of the world's oceans. The ACC is comprised of four major fronts: the Sub-Tropical Front (STF), the Polar Front (PF), the Sub-Antarctic Front (SAF), and the Southern ACC Front (SACCF). These were initially observed individually from repeat hydrographic sections and their approximate locations globally have been quantified using all available temperature data from the World Ocean and Climate Experiment (WOCE). More recent studies based on satellite altimetry have found that the front positions are more dynamic and have shifted south by up to 1° on average since 1993. Using ocean bottom pressure (OBP) data from the current Gravity Recovery and Climate Experiment (GRACE) we have measured integrated transport variability of the ACC south of Australia. However, differentiation of variability of specific fronts has been impossible due to the necessary smoothing required to reduce noise and correlated errors in the measurements. The future GRACE Follow-on (GFO) mission and the post 2020 GRACE-II mission are expected to produce higher resolution gravity fields with a monthly temporal resolution. Here, we study the resolution and error characteristics of GRACE gravity data that would be required to resolve variations in the front locations and transport. To do this, we utilize output from a high-resolution model of the Southern Ocean, hydrology models, and ice sheet surface mass balance models; add various amounts of random and correlated errors that may be expected from GFO and GRACE-II; and quantify requirements needed for future satellite gravity missions to resolve variations along the ACC fronts.

  10. 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.

  11. Trans-pacific glacial response to the Antarctic Cold Reversal in the southern mid-latitudes

    Science.gov (United States)

    Sagredo, Esteban A.; Kaplan, Michael R.; Araya, Paola S.; Lowell, Thomas V.; Aravena, Juan C.; Moreno, Patricio I.; Kelly, Meredith A.; Schaefer, Joerg M.

    2018-05-01

    Elucidating the timing and regional extent of abrupt climate events during the last glacial-interglacial transition (∼18-11.5 ka) is critical for identifying spatial patterns and mechanisms responsible for large-magnitude climate events. The record of climate change in the Southern Hemisphere during this time period, however, remains scarce and unevenly distributed. We present new geomorphic, chronological, and equilibrium line altitude (ELA) data from a climatically sensitive mountain glacier at Monte San Lorenzo (47°S), Central Patagonia. Twenty-four new cosmogenic 10Be exposure ages from moraines provide a comprehensive glacial record in the mid-latitudes of South America, which constrain the timing, spatial extent and magnitude of glacial fluctuations during the Antarctic Cold Reversal (ACR, ∼14.5-12.9 ka). Río Tranquilo glacier advanced and reached a maximum extent at 13.9 ± 0.7 ka. Three additional inboard moraines afford statistically similar ages, indicating repeated glacier expansions or marginal fluctuations over the ACR. Our record represents the northernmost robust evidence of glacial fluctuations during the ACR in southern South America, documenting not only the timing of the ACR maximum, but also the sequence of glacier changes within this climate event. Based on ELA reconstructions, we estimate a cooling of >1.6-1.8 °C at the peak of the ACR. The Río Tranquilo record along with existing glacial reconstructions from New Zealand (43°S) and paleovegetation records from northwestern (41°S) and central-west (45°S) Patagonia, suggest an uniform trans-Pacific glacier-climate response to an ACR trigger across the southern mid-latitudes. We posit that the equatorial migration of the southern westerly winds provides an adequate mechanism to propagate a common ACR signal across the Southern Hemisphere.

  12. Geological isotope anomalies as signatures of nearby supernovae

    CERN Document Server

    Ellis, Jonathan Richard; Schramm, David N; Ellis, John; Fields, Brian D; Schramm, David N

    1996-01-01

    Nearby supernova explosions may cause geological isotope anomalies via the direct deposition of debris or by cosmic-ray spallation in the earth's atmosphere. We estimate the mass of material deposited terrestrially by these two mechanisms, showing the dependence on the supernova distance. A number of radioactive isotopes are identified as possible diagnostic tools, such as Be-10, Al-26, Cl-36, Mn-53, Fe-60, and Ni-59, as well as the longer-lived I-129, Sm-146, and Pu-244. We discuss whether the 35 and 60 kyr-old Be-10 anomalies observed in the Vostok antarctic ice cores could be due to supernova explosions. Combining our estimates for matter deposition with results of recent nucleosynthesis yields, we calculate the expected signal from nearby supernovae using ice cores back to \\sim 300 kyr ago, and we discuss using deep ocean sediments back to several hundred Myr. In particular, we examine the prospects for identifying isotope anomalies due to the Geminga supernova explosion, and signatures of the possibility...

  13. Biodiversity of Antarctic echinoids: a comprehensive and interactive database

    Directory of Open Access Journals (Sweden)

    Bruno David

    2005-12-01

    Full Text Available Eighty-one echinoid species are present south of the Antarctic Convergence, and they represent an important component of the benthic fauna. “Antarctic echinoids” is an interactive database synthesising the results of more than 100 years of Antarctic expeditions, and comprising information about all echinoid species. It includes illustrated keys for determination of the species, and information about their morphology and ecology (text, illustrations and glossary and their distribution (maps and histograms of bathymetrical distribution; the sources of the information (bibliography, collections and expeditions are also provided. All these data (taxonomic, morphologic, geographic, bathymetric… can be interactively queried in two main ways: (1 display of listings that can be browsed, sorted according to various criteria, or printed; and (2 interactive requests crossing the different kinds of data. Many other possibilities are offered, and an on-line help file is also available.

  14. Spatial-temporal variations in surface ozone over Ushuaia and the Antarctic region: observations from in situ measurements, satellite data, and global models.

    Science.gov (United States)

    Nadzir, Mohd Shahrul Mohd; Ashfold, Matthew J; Khan, Md Firoz; Robinson, Andrew D; Bolas, Conor; Latif, Mohd Talib; Wallis, Benjamin M; Mead, Mohammed Iqbal; Hamid, Haris Hafizal Abdul; Harris, Neil R P; Ramly, Zamzam Tuah Ahmad; Lai, Goh Thian; Liew, Ju Neng; Ahamad, Fatimah; Uning, Royston; Samah, Azizan Abu; Maulud, Khairul Nizam; Suparta, Wayan; Zainudin, Siti Khalijah; Wahab, Muhammad Ikram Abdul; Sahani, Mazrura; Müller, Moritz; Yeok, Foong Swee; Rahman, Nasaruddin Abdul; Mujahid, Aazani; Morris, Kenobi Isima; Sasso, Nicholas Dal

    2018-01-01

    The Antarctic continent is known to be an unpopulated region due to its extreme weather and climate conditions. However, the air quality over this continent can be affected by long-lived anthropogenic pollutants from the mainland. The Argentinian region of Ushuaia is often the main source area of accumulated hazardous gases over the Antarctic Peninsula. The main objective of this study is to report the first in situ observations yet known of surface ozone (O 3 ) over Ushuaia, the Drake Passage, and Coastal Antarctic Peninsula (CAP) on board the RV Australis during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC'16). Hourly O 3 data was measured continuously for 23 days using an EcoTech O 3 analyzer. To understand more about the distribution of surface O 3 over the Antarctic, we present the spatial and temporal of surface O 3 of long-term data (2009-2015) obtained online from the World Meteorology Organization of World Data Centre for greenhouse gases (WMO WDCGG). Furthermore, surface O 3 satellite data from the free online NOAA-Atmospheric Infrared Sounder (AIRS) database and online data assimilation from the European Centre for Medium-Range Weather Forecasts (ECMWF)-Monitoring Atmospheric Composition and Climate (MACC) were used. The data from both online products are compared to document the data sets and to give an indication of its quality towards in situ data. Finally, we used past carbon monoxide (CO) data as a proxy of surface O 3 formation over Ushuaia and the Antarctic region. Our key findings were that the surface O 3 mixing ratio during MASEC'16 increased from a minimum of 5 ppb to ~ 10-13 ppb approaching the Drake Passage and the Coastal Antarctic Peninsula (CAP) region. The anthropogenic and biogenic O 3 precursors from Ushuaia and the marine region influenced the mixing ratio of surface O 3 over the Drake Passage and CAP region. The past data from WDCGG showed that the annual O 3 cycle has a maximum during the winter of 30 to 35

  15. 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

  16. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

    Science.gov (United States)

    Humphries, R. S.; Klekociuk, A. R.; Schofield, R.; Keywood, M.; Ward, J.; Wilson, S. R.

    2016-02-01

    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 simulations and observations of

  17. In vitro immunobiological activity of an Antarctic streptomyces polysaccharide

    International Nuclear Information System (INIS)

    Toshkova, R.; Yossifova, L.; Gardeva, E.; Zvetkova, E.; Ivanova, V.

    2010-01-01

    Antarctic Streptomyces sp. 1010, were obtained from sea water samples (Livingston Island, Antarctica), during the Third Bulgarian Antarctic Scientific Expedition (1994-1995). The ecophysiological methods for isolation and characterization of these active, cold-adapted, Gram-positive microorganisms (psychrophiles) in morphological, phenotypic, genetic and taxonomic aspects, have been earlier reported. In this study, a new extracellular polysaccharide (heteropolysaccharide) has been isolated and purified from cultured broth of the Antarctic Streptomyces sp. 1010. The monosaccharide content of the Antarctic streptomyces heteropolysaccharide has been examined by TLC and GC/MS. The mitogenic and immuno potential properties of the purified Antarctic Streptomyces polysaccharide (ASMP) have been studied in vitro - in the short-term cultures of human peripheral blood mononuclear cells (hPBMCs - lymphocytes and monocytes) and mouse spleen lymphocytes (mouse splenocytes - mSps). The results obtained show that ASMP has a double lectin-like effect on the proliferative activity of hPBMCs: similar to this of Con A on the lymphoid cells (preliminary T-lymphocytes) and to the effect of LPS on the mononuclear from monocyte-macrophage lineage. Expressed as proliferative index (PI), the mitogenic response of mSps to the in vitro influence of ASMP was also higher than PI in the negative, as well as in the positive controls (mSps, cultured in the presence of PHA, Con A and LPS). The new Antarctic Streptomyces' heteropolysaccharide examined could be useful in the future as an immunomodulative biologically active substance and its extracellular production may contribute to the development of thermobiochemistry, immunomodulative drug therapy and immunopharmaceutical industry. (authors)

  18. 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."

  19. 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.

  20. Unsupervised signature extraction from forensic logs

    NARCIS (Netherlands)

    Thaler, S.M.; Menkovski, V.; Petkovic, M.; Altun, Y.; Das, K.; Mielikäinen, T.; Malerba, D.; Stefanowski, J.; Read, J.; Žitnik, M.; Ceci, M.

    2017-01-01

    Signature extraction is a key part of forensic log analysis. It involves recognizing patterns in log lines such that log lines that originated from the same line of code are grouped together. A log signature consists of immutable parts and mutable parts. The immutable parts define the signature, and

  1. 7 CFR 718.9 - Signature requirements.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Signature requirements. 718.9 Section 718.9... MULTIPLE PROGRAMS General Provisions § 718.9 Signature requirements. (a) When a program authorized by this chapter or Chapter XIV of this title requires the signature of a producer; landowner; landlord; or tenant...

  2. 42 CFR 424.36 - Signature requirements.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Signature requirements. 424.36 Section 424.36... (CONTINUED) MEDICARE PROGRAM CONDITIONS FOR MEDICARE PAYMENT Claims for Payment § 424.36 Signature requirements. (a) General rule. The beneficiary's own signature is required on the claim unless the beneficiary...

  3. 17 CFR 12.12 - Signature.

    Science.gov (United States)

    2010-04-01

    ... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Signature. 12.12 Section 12.12... General Information and Preliminary Consideration of Pleadings § 12.12 Signature. (a) By whom. All... document on behalf of another person. (b) Effect. The signature on any document of any person acting either...

  4. 25 CFR 213.10 - Lessor's signature.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Lessor's signature. 213.10 Section 213.10 Indians BUREAU... MEMBERS OF FIVE CIVILIZED TRIBES, OKLAHOMA, FOR MINING How to Acquire Leases § 213.10 Lessor's signature... thumbprint which shall be designated as “right” or “left” thumbmark. Such signatures must be witnessed by two...

  5. Signature effects in 2-qp rotational bands

    International Nuclear Information System (INIS)

    Jain, A.K.; Goel, A.

    1992-01-01

    The authors briefly review the progress in understanding the 2-qp rotational bands in odd-odd nuclei. Signature effects and the phenomenon of signature inversion are discussed. The Coriolis coupling appears to have all the ingredients to explain the inversion. Some recent work on signature dependence in 2-qp bands of even-even nuclei is also discussed; interesting features are pointed out

  6. 27 CFR 17.6 - Signature authority.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Signature authority. 17.6... PRODUCTS General Provisions § 17.6 Signature authority. No claim, bond, tax return, or other required... other proper notification of signature authority has been filed with the TTB office where the required...

  7. High-speed high-security signatures

    NARCIS (Netherlands)

    Bernstein, D.J.; Duif, N.; Lange, T.; Schwabe, P.; Yang, B.Y.

    2011-01-01

    This paper shows that a $390 mass-market quad-core 2.4GHz Intel Westmere (Xeon E5620) CPU can create 108000 signatures per second and verify 71000 signatures per second on an elliptic curve at a 2128 security level. Public keys are 32 bytes, and signatures are 64 bytes. These performance figures

  8. 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

  9. Some Proxy Signature and Designated verifier Signature Schemes over Braid Groups

    OpenAIRE

    Lal, Sunder; Verma, Vandani

    2009-01-01

    Braids groups provide an alternative to number theoretic public cryptography and can be implemented quite efficiently. The paper proposes five signature schemes: Proxy Signature, Designated Verifier, Bi-Designated Verifier, Designated Verifier Proxy Signature And Bi-Designated Verifier Proxy Signature scheme based on braid groups. We also discuss the security aspects of each of the proposed schemes.

  10. 222Rn in the Antarctic Peninsula during 1986

    International Nuclear Information System (INIS)

    Pereira, E.B.; Setzer, A.W.; Cavalcanti, I.F.A.

    1988-01-01

    222 Rn was continuously measured at the Brazilian Antarctic Station (62 0 S, 58 0 W) during the year of 1986. Baseline radon concentration averaged 0.02 Bq.m -3 with surges peaking 0.4 Bq.m -3 . The data exhibited a characteristic periodicity of about 25 days and a strong positive association with short term fluctuations of atmospheric temperature. No seasonal variations of radon were observed. Interpretation of the radon surges with reference to synoptic charts and weather satellite pictures showed that the continental influence of radon at the Antarctic Peninsula is very small and comes only from the tip of the South American cone. (author)

  11. Microbiology and Geochemistry of Antarctic Paleosols

    Science.gov (United States)

    Mahaney, W. C.; Malloch, D.; Hancock, R. G. V.; Campbell, I. B.; Sheppard, D.

    2000-08-01

    Samples of ancient soils from horizons in paleosols from the Quartermain Mountains (Aztec and New Mountain areas of the Antarctic Dry Valleys) were analyzed for their chemical composition and microbiology to determine the accumulation and movement of salts and other soluble constituents. The salt concentrations are of special interest because they are considered to be a function of age, derived in part from nearby oceanic and high altitude atmospheric sources. The geochemistry of ancient Miocene-age paleosols in these areas is the direct result of the deposition and weathering of till, derived principally from dolerite and sandstone source rock, in association with airborne-influxed salts. Paleosols nearer the coast have greater contents of chlorine, and farther inland 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, to the order of several million years. Iron, both in total concentration and in the form of various extracts, indicates it can be used as a geochronometer to assess the buildup of goethite plus hematite over time in the paleosols. Trends for ferrihydrite, a partially soluble Fe-hydroxide, shows limited profile translocation that might be related to the movement of salt. Six of the eight selected subsamples from paleosol horizons in three soil profiles contained nil concentrations of bacteria and fungi. However, two horizons at depths of between three to eight centimeters yielded several colonies of the fungi Beauveria bassiana and Penicillium spp., indicating some 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

  12. Antarctic biology in the 21st century - Advances in, and beyond the international polar year 2007-2008’

    Science.gov (United States)

    Stoddart, Michael

    2010-08-01

    The International Polar Year 2007-2008 (IPY) has provided an opportunity for biology to show itself as an important part of Antarctic science in a manner in which it was not seen during earlier Polar Years. Of the 15 endorsed biological projects in Antarctica, 7 included more than 20 scientists and could be deemed truly international. Four were conducted in the marine environment, and one each in the fields of biological invasions, microbial ecology, and terrestrial ecology, and one was SCAR’s over-arching ‘Evolution and Biodiversity in the Antarctic’. The marine projects have left a robust legacy of data for future research into the consequences of environmental change, and into future decisions about marine protected areas. Studies on introductions of exotic organisms reveal an ever-present threat to the warmer parts of the high-latitude Southern Ocean, or parts which might become warmer with climate change. Studies on microbial ecology reveal great complexity of ecosystems with high numbers of unknown species. Terrestrial research has shown how vulnerable the Antarctic is to accidental introductions, and how productive the soils can be under changed climate conditions. Antarctic biology has come-of-age during IPY 2007-2008 and the campaign has set the scene for future research.

  13. 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

  14. 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

  15. 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

  16. Nonlinear analysis of dynamic signature

    Science.gov (United States)

    Rashidi, S.; Fallah, A.; Towhidkhah, F.

    2013-12-01

    Signature is a long trained motor skill resulting in well combination of segments like strokes and loops. It is a physical manifestation of complex motor processes. The problem, generally stated, is that how relative simplicity in behavior emerges from considerable complexity of perception-action system that produces behavior within an infinitely variable biomechanical and environmental context. To solve this problem, we present evidences which indicate that motor control dynamic in signing process is a chaotic process. This chaotic dynamic may explain a richer array of time series behavior in motor skill of signature. Nonlinear analysis is a powerful approach and suitable tool which seeks for characterizing dynamical systems through concepts such as fractal dimension and Lyapunov exponent. As a result, they can be analyzed in both horizontal and vertical for time series of position and velocity. We observed from the results that noninteger values for the correlation dimension indicates low dimensional deterministic dynamics. This result could be confirmed by using surrogate data tests. We have also used time series to calculate the largest Lyapunov exponent and obtain a positive value. These results constitute significant evidence that signature data are outcome of chaos in a nonlinear dynamical system of motor control.

  17. 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

  18. Persistent organohalogen contaminant burdens in Antarctic krill (Euphausia superba) from the eastern Antarctic sector: A baseline study

    International Nuclear Information System (INIS)

    Bengtson Nash, S.M.; Poulsen, A.H.; Kawaguchi, S.; Vetter, W.; Schlabach, M.

    2008-01-01

    A baseline for persistent organohalogen compound (POC) accumulation in the Antarctic keystone species, Antarctic krill (Euphausia superba) has been established for a 50 deg. longitudinal range of the eastern Antarctic sector. Samples of adult krill, caught from 12 sites distributed between 30 deg. and 80 deg. E (60-70 deg. S), were analysed for > 100 organohalogen compounds including chlorinated pesticides, polychlorinated biphenyls (PCBs), polybrominated organic compounds and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs). Organochlorine pesticides dominated measured krill contaminant burdens with hexachlorobenzene (HCB) as the single most abundant compound quantified. Krill HCB concentrations were comparable to those detected at this trophic level in both the Arctic and temperate northwest Atlantic, lending support for the hypothesis that HCB will approach global equilibrium at a faster rate than other POCs. Para, para'-dichlorodiphenylethene (p,p'-DDE) was detected at notable concentrations. Measurements of DDT and its degradation products provide an important baseline for monitoring the temporal and geographical influence of renewed, DDT usage for malaria-control in affected southern hemisphere countries. In contrast to the Arctic, PCBs did not feature prominently in contaminant burdens of Antarctic krill. The major commercial polybrominated diphenyl ether (PBDE) congeners -99 and -47 were quantified at low background levels with clear concentration spikes observed at around 70 deg. E , in the vicinity of modern, active research stations. The likelihood that local anthropogenic activities are supplementing low PBDE levels, delivered otherwise primarily via long range environmental transport, is discussed. The suspected naturally occurring brominated organic compound, 2,4,6-tribromoanisole (TBA), was a ubiquitous contaminant in all samples whereas the only PCDD/Fs quantifiable were trace levels of octachlorodibenzo-p-dioxin (OCDD) and 1,2,3

  19. 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.

  20. The Antarctic permafrost as a testbed for REMS (Rover Environmental Monitoring Station-Mars Science Laboratory)

    Science.gov (United States)

    Esteban, B.; Ramos, M.; Sebastián, E.; Armiens, C.; Gómez-Elvira, J.; Cabos, W.; de Pablo, M. A.

    2009-04-01

    The present climatic characteristics of Mars favor the presence of extense permafrost areas in this lonely planet. Therefore environmental parameters that are included in Martian Rover missions are also used for monitoring thermal soil surface evolution in order to study the permafrost active layer thickness and the energy balance in the soil-atmosphere boundary limit layer. The REMS (Rover Environmental Monitoring Station) is an environmental station designed by the Centro de Astrobiología (CAB- Spain) with the collaboration of national and international partners (CRISA/EADS, UPC and FMI), which is part of the payload of the MSL (Mars Science Laboratory) NASA mission to Mars (http://mars.jpl.nasa.gov/msl/overview/). This mission is expected to be launched in the final months of 2009, and mainly consists of a Rover, with a complete set of scientific instruments; the Rover will carry the biggest, most advanced suite of instruments for scientific studies ever sent to the Martian surface. Five sensors compose the REMS instrument: ground (GT-REMS) and air temperatures, wind speed and direction, pressure, humidity and ultraviolet radiation (UV-REMS). A simplified setup of the REMS was deployed on Antarctica in the surroundings of the Spanish Antarctic Stations on Livingston and Deception Islands (Maritime Antarctica), where the permafrost distribution is well-known. The aim of the experiment was to check REMS's sensors response against hard environmental conditions and calibrates their measures with standard Antarctic devices. The experimental apparatuses included some standard meteorological and thermopiles sensors corresponding to the REMS. All the sensors are mounted in a 1.8 m mast and include a Pt100 air temperature sensor with shield solar protection on the mast top, a Kipp and Zonnen CNR1 net radiometer for measuring infrared (5-50 μm) and short wave solar (305-2800 nm) radiation at 1.5 m high, GT-REMS sensor and its amplification box at 0.7 m high and finally

  1. 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

  2. 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.

  3. 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%.

  4. 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

  5. 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

  6. Novel Cold-Adapted Esterase MHlip from an Antarctic Soil Metagenome

    Directory of Open Access Journals (Sweden)

    Moreno Galleni

    2013-01-01

    Full Text Available An Antarctic soil metagenomic library was screened for lipolytic enzymes and allowed for the isolation of a new cytosolic esterase from the a/b hydrolase family 6, named MHlip. This enzyme is related to hypothetical genes coding esterases, aryl-esterases and peroxydases, among others. MHlip was produced, purified and its activity was determined. The substrate profile of MHlip reveals a high specificity for short p-nitrophenyl-esters. The apparent optimal activity of MHlip was measured for p-nitrophenyl-acetate, at 33 °C, in the pH range of 6–9. The MHlip thermal unfolding was investigated by spectrophotometric methods, highlighting a transition (Tm at 50 °C. The biochemical characterization of this enzyme showed its adaptation to cold temperatures, even when it did not present evident signatures associated with cold-adapted proteins. Thus, MHlip adaptation to cold probably results from many discrete structural modifications, allowing the protein to remain active at low temperatures. Functional metagenomics is a powerful approach to isolate new enzymes with tailored biophysical properties (e.g., cold adaptation. In addition, beside the ever growing amount of sequenced DNA, the functional characterization of new catalysts derived from environment is still required, especially for poorly characterized protein families like α/b hydrolases.

  7. 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

  8. 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

  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. 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...

  11. 76 FR 60933 - Antarctic Conservation Act Permit Applications

    Science.gov (United States)

    2011-09-30

    ... NATIONAL SCIENCE FOUNDATION Antarctic Conservation Act Permit Applications AGENCY: National... Conservation Act of 1978. DATES: Interested parties are invited to submit written data, comments, or views with... Regulation for conduct of a flight from South America, over the South Pole, landing at Teniente Marsh Base...

  12. Microbial ecology and biogeochemistry of continental Antarctic soils.

    Science.gov (United States)

    Cowan, Don A; Makhalanyane, Thulani P; Dennis, Paul G; Hopkins, David W

    2014-01-01

    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 harbor 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.

  13. 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 ...

  14. 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.

  15. Freshwater invertebrates of sub-Antarctic Marion Island | Dartnall ...

    African Journals Online (AJOL)

    The aquatic species include five platyhelminthes, a gastrotrich, three tardigrades, 28 rotifers, six nematodes, two annelids and 11 arthropods. Most are familiar species that have been recorded on other sub-Antarctic islands. The invertebrate faunas of the various freshwater habitats were basically similar in species ...

  16. 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

  17. Insignificant change in Antarctic snowmelt volume since 1979

    NARCIS (Netherlands)

    Kuipers Munneke, P.; Picard, G.; van den Broeke, M.R.; Lenaerts, J.T.M.; van Meijgaard, E.

    2012-01-01

    Surface snowmelt is widespread in coastal Antarctica. Satellite-based microwave sensors have been observing melt area and duration for over three decades. However, these observations do not reveal the total volume of meltwater produced on the ice sheet. Here we present an Antarctic melt volume

  18. 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.; Ligtenberg, S.R.M.; van den Broeke, M.R.; 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

  19. 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

  20. 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

  1. 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.

  2. The Antarctic is a region where the largest human- induced ...

    African Journals Online (AJOL)

    induced perturbation of the marine ecosystem in the world has ... and minke whales feed mainly on krill, and they share a similar feeding area near the Antarctic ice edge. In the .... a result of improved analytical techniques). ...... of this functional response, and further field studies ... ASH, C. E. 1962 — The Whaler's Eye.

  3. 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

  4. 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

  5. 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....

  6. Regional Antarctic snow accumulation over the past 1000 years

    Directory of Open Access Journals (Sweden)

    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.

  7. Passive Polarimetric Microwave Signatures Observed Over Antarctica

    Science.gov (United States)

    WindSat satellite-based fully polarimetric passive microwave observations, expressed in the form of the Stokes vector, were analyzed over the Antarctic ice sheet. The vertically and horizontally polarized brightness temperatures (first two Stokes components) from WindSat are shown to be consistent w...

  8. Trace-element analysis of Antarctic H chondrites: Chemical weathering and comparisons with their non-Antarctic counterparts

    International Nuclear Information System (INIS)

    Kwok, J.E.

    1986-01-01

    Large numbers of meteorites have been discovered in Antarctica over the last decade (7000 fragments probably representing over 1200 separate events). They are important for their numbers and for their complement of unique or rare specimens; they also have long terrestrial ages (up to 1,000,000 years) compared to non-Antarctic falls (usually < 200 years). We report compositional data for mobile/volatile trace elements Ag, Au, Bi, Cd, Co, Cs, In, Rb, Sb, Se, Te, Ti, U, and Zn in a suite of Antarctic H chondrites. Our data show that heavily oxidized H chondrites are leached of a portion of their trace elements and, therefore, have been chemically compromised by their stay in Antarctica. The less oxidized specimens seem to have retained their chemical integrity. We suggest possibilities for using chemical data to measure the degree of a chondrite's chemical weathering. We compare our data to that obtained previously for non-Antarctic H chondrites (Linger et al., 1986), by petrologic type (H4, H5, H6, H4-6) and shock-loading (moderately shocked facies a-c, heavily shocked facies d-f). Many statistically significant differences are found between non-Antarctic and Victoria Land, Antarctica H chondrites of each petrologic type and of shock facies d-f

  9. Infrared signatures for remote sensing

    International Nuclear Information System (INIS)

    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 -1 at 2 laser. PNL also has a beam expansion source with a 12-cm slit, which provides a 3-m effective path for gases at ∼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 4 at 770--800 cm -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 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

  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. 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.

    2015-12-01

    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.

  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. 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.

  14. Empirical estimation of present-day Antarctic glacial isostatic adjustment and ice mass change

    Science.gov (United States)

    Gunter, B. C.; Didova, O.; Riva, R. E. M.; Ligtenberg, S. R. M.; Lenaerts, J. T. M.; King, M. A.; van den Broeke, M. R.; Urban, T.

    2014-04-01

    This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new Ice, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related mass change estimates for the entire Antarctic ice sheet ranged from 53 to 103 Gt yr-1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr-1. Over the time frame February 2003-October 2009, the corresponding ice mass change showed an average value of -100 ± 44 Gt yr-1 (EA: 5 ± 38, WA: -105 ± 22), consistent with other recent estimates in the literature, with regional mass loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and ice mass change, particularly with respect to determining more reliable uncertainties.

  15. Bacterial diversity in rhizosphere soil from Antarctic vascular plants of Admiralty Bay, maritime Antarctica.

    Science.gov (United States)

    Teixeira, Lia C R S; Peixoto, Raquel S; Cury, Juliano C; Sul, Woo Jun; Pellizari, Vivian H; Tiedje, James; Rosado, Alexandre S

    2010-08-01

    The Antarctic is a pristine environment that contributes to the maintenance of the global climate equilibrium. The harsh conditions of this habitat are fundamental to selecting those organisms able to survive in such an extreme habitat and able to support the relatively simple ecosystems. The DNA of the microbial community associated with the rhizospheres of Deschampsia antarctica Desv (Poaceae) and Colobanthus quitensis (Kunth) BartI (Caryophyllaceae), the only two native vascular plants that are found in Antarctic ecosystems, was evaluated using a 16S rRNA multiplex 454 pyrosequencing approach. This analysis revealed similar patterns of bacterial diversity between the two plant species from different locations, arguing against the hypothesis that there would be differences between the rhizosphere communities of different plants. Furthermore, the phylum distribution presented a peculiar pattern, with a bacterial community structure different from those reported of many other soils. Firmicutes was the most abundant phylum in almost all the analyzed samples, and there were high levels of anaerobic representatives. Also, some phyla that are dominant in most temperate and tropical soils, such as Acidobacteria, were rarely found in the analyzed samples. Analyzing all the sample libraries together, the predominant genera found were Bifidobacterium (phylum Actinobacteria), Arcobacter (phylum Proteobacteria) and Faecalibacterium (phylum Firmicutes). To the best of our knowledge, this is the first major bacterial sequencing effort of this kind of soil, and it revealed more than expected diversity within these rhizospheres of both maritime Antarctica vascular plants in Admiralty Bay, King George Island, which is part of the South Shetlands archipelago.

  16. 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.

  17. 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

  18. Signature Curves Statistics of DNA Supercoils

    OpenAIRE

    Shakiban, Cheri; Lloyd, Peter

    2004-01-01

    In this paper we describe the Euclidean signature curves for two dimensional closed curves in the plane and their generalization to closed space curves. The focus will be on discrete numerical methods for approximating such curves. Further we will apply these numerical methods to plot the signature curves related to three-dimensional simulated DNA supercoils. Our primary focus will be on statistical analysis of the data generated for the signature curves of the supercoils. We will try to esta...

  19. The effect of environmental change on vascular plant and cryptogam communities from the Falkland Islands and the Maritime Antarctic

    Directory of Open Access Journals (Sweden)

    Convey Peter

    2007-12-01

    Full Text Available Abstract Background Antarctic terrestrial vegetation is subject to one of the most extreme climates on Earth. Currently, parts of Antarctica are one of the fastest warming regions on the planet. During 3 growing seasons, we investigated the effect of experimental warming on the diversity and abundance of coastal plant communities in the Maritime Antarctic region (cryptogams only and the Falkland Islands (vascular plants only. We compared communities from the Falkland Islands (51°S, mean annual temperature 7.9°C, with those of Signy Island (60°S, -2.1°C and Anchorage Island (67°S, -2.6°C, and experimental temperature manipulations at each of the three islands using Open Top Chambers (OTCs. Results Despite the strong difference in plant growth form dominance between the Falkland Islands and the Maritime Antarctic, communities across the gradient did not differ in total diversity and species number. During the summer months, the experimental temperature increase at 5 cm height in the vegetation was similar between the locations (0.7°C across the study. In general, the response to this experimental warming was low. Total lichen cover showed a non-significant decreasing trend at Signy Island (p Conclusion These results suggest that small temperature increases may rapidly lead to decreased soil moisture, resulting in more stressful conditions for plants. The more open plant communities (grass and lichen appeared more negatively affected by such changes than dense communities (dwarf shrub and moss.

  20. Carbon Storage in Soils: Climate vs. Geology

    International Nuclear Information System (INIS)

    Doetterl, Sebastian; Boeckx, Pascal; Stevens, Antoine; Van Oost, Kristof; Six, Johan; Merckx, Roel; Casanova Pinto, Manuel; Casanova-Katny, Angélica; Muñoz, Cristina; Zagal Venegas, Erick; Boudin, Mathieu

    2016-01-01

    In a recently published Nature Geoscience article, scientists took a closer look at the much-discussed topic of carbon storage in soils under Climate Change. In a large-scale study across Chile and the Antarctic Peninsula, they showed that the role of precipitation and temperature in controlling carbon dynamics in soils is less than currently considered in Global Ecosystem Models. Soils are important for carbon (C) storage and thus for atmospheric CO 2 concentrations. Whether soils act as a sink or source for atmospheric C generally depend on climatic factors, as they control plant growth (driving the incorporation of C into the soil), the activity of soil microorganism (driving the release of C from the soil to the atmosphere), as well as several other chemical processes in soils. However, we still do not fully understand the response of soil C to Climate Change. An international team of researchers led by Pascal Boeckx and Sebastian Doetterl from Ghent University, Belgium and Erick Zagal from University of Concepcion in Chile, have been investigating the interaction between climate, different types of soil minerals, and soil as sink or source for C. They studied this interaction by sampling soils from numerous locations representing different vegetation types in Chile and the Antarctic Peninsula

  1. 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...

  2. On reliable discovery of molecular signatures

    Directory of Open Access Journals (Sweden)

    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.

  3. Modeling the Thermal Signature of Natural Backgrounds

    National Research Council Canada - National Science Library

    Gamborg, Marius

    2002-01-01

    Two measuring stations have been established the purpose being to collect comprehensive databases of thermal signatures of background elements in addition to the prevailing meteorological conditions...

  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. The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet-climate model

    NARCIS (Netherlands)

    Stap, Lennert B.; Van De Wal, Roderik S.W.; De Boer, Bas; Bintanja, Richard; Lourens, Lucas J.

    2017-01-01

    Since the inception of the Antarctic ice sheet at the Eocene-Oligocene transition ( ~34 Myr ago), land ice has played a crucial role in Earth's climate. Through feedbacks in the climate system, land ice variability modifies atmospheric temperature changes induced by orbital, topographical, and

  6. A compendium and functional characterization of mammalian genes involved in adaptation to Arctic or Antarctic environments.

    Science.gov (United States)

    Yudin, Nikolay S; Larkin, Denis M; Ignatieva, Elena V

    2017-12-28

    Many mammals are well adapted to surviving in extremely cold environments. These species have likely accumulated genetic changes that help them efficiently cope with low temperatures. It is not known whether the same genes related to cold adaptation in one species would be under selection in another species. The aims of this study therefore were: to create a compendium of mammalian genes related to adaptations to a low temperature environment; to identify genes related to cold tolerance that have been subjected to independent positive selection in several species; to determine promising candidate genes/pathways/organs for further empirical research on cold adaptation in mammals. After a search for publications containing keywords: "whole genome", "transcriptome or exome sequencing data", and "genome-wide genotyping array data" authors looked for information related to genetic signatures ascribable to positive selection in Arctic or Antarctic mammalian species. Publications related to Human, Arctic fox, Yakut horse, Mammoth, Polar bear, and Minke whale were chosen. The compendium of genes that potentially underwent positive selection in >1 of these six species consisted of 416 genes. Twelve of them showed traces of positive selection in three species. Gene ontology term enrichment analysis of 416 genes from the compendium has revealed 13 terms relevant to the scope of this study. We found that enriched terms were relevant to three major groups: terms associated with collagen proteins and the extracellular matrix; terms associated with the anatomy and physiology of cilium; terms associated with docking. We further revealed that genes from compendium were over-represented in the lists of genes expressed in the lung and liver. A compendium combining mammalian genes involved in adaptation to cold environment was designed, based on the intersection of positively selected genes from six Arctic and Antarctic species. The compendium contained 416 genes that have been

  7. Projected continent-wide declines of the emperor penguin under climate change

    NARCIS (Netherlands)

    Jenouvrier, S.; Holland, M.; Stroeve, J.; Serreze, M.; Barbraud, C.; Weimerskirch, H.; Caswell, H.

    2014-01-01

    Climate change has been projected to affect species distribution1 and future trends of local populations2, 3, but projections of global population trends are rare. We analyse global population trends of the emperor penguin (Aptenodytes forsteri), an iconic Antarctic top predator, under the influence

  8. Turning microplastics into nanoplastics through digestive fragmentation by Antarctic krill.

    Science.gov (United States)

    Dawson, Amanda L; Kawaguchi, So; King, Catherine K; Townsend, Kathy A; King, Robert; Huston, Wilhelmina M; Bengtson Nash, Susan M

    2018-03-08

    Microplastics (plastics microplastics through ingestion. Here, by exposing Antarctic krill (Euphausia superba) to microplastics under acute static renewal conditions, we present evidence of physical size alteration of microplastics ingested by a planktonic crustacean. Ingested microplastics (31.5 µm) are fragmented into pieces less than 1 µm in diameter. Previous feeding studies have shown spherical microplastics either; pass unaffected through an organism and are excreted, or are sufficiently small for translocation to occur. We identify a new pathway; microplastics are fragmented into sizes small enough to cross physical barriers, or are egested as a mixture of triturated particles. These findings suggest that current laboratory-based feeding studies may be oversimplifying interactions between zooplankton and microplastics but also introduces a new role of Antarctic krill, and potentially other species, in the biogeochemical cycling and fate of plastic.

  9. Natural and anthropogenic hydrocarbons in the Antarctic pack ice

    International Nuclear Information System (INIS)

    Nemirovskaya, I.A.; Novigatsky, A.N.

    2004-01-01

    A field experiment was conducted near the Russian Antarctic stations in May, 2001 in the Pridz Bay and coastal part of the Davies Sea to examine the content of dissolved and suspended forms of aliphatic hydrocarbons in melted snow samples, pack ice and ice cores. The site included clean control areas and polluted test areas. A spill was performed by covering the bare ice surface with marine diesel fuel. The different physical characteristics of clean and polluted ice were measured. This included radiation balance, reflected solar radiation, integral albedo radiation, surface temperature, seawater temperature, salinity at depth, and ice salinity. The study showed that accumulation of natural and anthropogenic hydrocarbon took place in the ice-water barrier zone, mostly in suspended form. It was concluded that for oil spills in pack Antarctic ice, the mechanism of filtration due to convection-diffusion plays an important role in the transformation of diesel fuel. 14 refs., 2 tabs., 2 figs

  10. Are Antarctic ozone variations a manifestation of dynamics or chemistry?

    Science.gov (United States)

    Tung, K.-K.; Ko, M. K. W.; Rodriguez, J. M.; Sze, N. D.

    1986-01-01

    The existence of a reverse circulation cell with rising motion in the polar lower stratosphere is suggested as an explanation for the temporal behavior of the ozone column density in the Antarctic region. The upwelling brings ozone-poor air from below 100 mbar to the stratosphere, possibly contributing to the observed ozone decline in early spring. At the same time, the Antarctic stratosphere might contain a very low concentration of NO(x), a condition that could favor a greatly enhanced catalytic removal of O3 by halogen species. It is argued that heterogeneous processes and formation of OClO by the reaction BrO+ClO - OClO+Br before and after the polar night might help to suppress the NO(x) levels during the early spring period.

  11. Development of the interface software for the Antarctic penetrator

    Directory of Open Access Journals (Sweden)

    Kazuo Shibuya

    2005-11-01

    Full Text Available We have developed PC-based interface software which controls ground system segments (GSSs of the Antarctic penetrator through an automatic data collection system onboard a helicopter. A pen-touch panel was developed for easy operation. There are six basic functions in the interface software; GSS time synchronization", make schedule file", send schedule file", GSS time calibration", data read-out", and sleep". The sleep command enables us to cut off the radio transmitter/receiver to save power during a pre-determined period. After execution of each command, log files are saved automatically. In order to monitor processing by eye, a bar graph appears during execution of time synchronization" and data read-out". As for malfunctioning encountered during the 43rd Japanese Antarctic Research Expedition, the related software bugs were identified and the codes were rewritten.

  12. The delta18O composition of Antarctic coastal current waters

    International Nuclear Information System (INIS)

    Frew, R.; Heywood, K.; Dennis, P.

    1997-01-01

    The varying proportions of 18 O to 16 O in sea water provide an oceanographic trace like salinity, but with an extra degree of freedom: salt is a tracer for the oceanic fluid, whereas the isotopic composition is a tracer specifically for the water component of that fluid. Hydrogen and oxygen isotopes are the variables most intimately related to the water component in the sea, therefore thay furnish a direct link to the water in the atmosphere and on continents and to the precipitation cycle which caused the salinity changes. The ratio of 18 O to 16 O (delta 18 O) ot waters is a powerful tracer in polar regions where sea and glacial ice processes decouple delta 18 O from salinity. Here we present observations from a significant but relatively unexplored component of the Southern Ocean current system, the Antarctic Coastal Current, and its associated Antarctic Slope Front. (author)

  13. Depletion of stratospheric ozone over the Antarctic and Arctic: Responses of plants of polar terrestrial ecosystems to enhanced UV-B, an overview

    International Nuclear Information System (INIS)

    Rozema, Jelte; Boelen, Peter; Blokker, Peter

    2005-01-01

    Depletion of stratospheric ozone over the Antarctic has been re-occurring yearly since 1974, leading to enhanced UV-B radiation. Arctic ozone depletion has been observed since 1990. Ozone recovery has been predicted by 2050, but no signs of recovery occur. Here we review responses of polar plants to experimentally varied UV-B through supplementation or exclusion. In supplementation studies comparing ambient and above ambient UV-B, no effect on growth occurred. UV-B-induced DNA damage, as measured in polar bryophytes, is repaired overnight by photoreactivation. With UV exclusion, growth at near ambient may be less than at below ambient UV-B levels, which relates to the UV response curve of polar plants. UV-B screening foils also alter PAR, humidity, and temperature and interactions of UV with environmental factors may occur. Plant phenolics induced by solar UV-B, as in pollen, spores and lignin, may serve as a climate proxy for past UV. Since the Antarctic and Arctic terrestrial ecosystems differ essentially (e.g. higher species diversity and more trophic interactions in the Arctic), generalization of polar plant responses to UV-B needs caution. - Polar plant responses to UV-B may be different in the Arctic than Antarctic regions

  14. Kinetic control on Zn isotope signatures recorded in marine diatoms

    Science.gov (United States)

    Köbberich, Michael; Vance, Derek

    2017-08-01

    Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that

  15. Persistent solar signatures in cloud cover: spatial and temporal analysis

    International Nuclear Information System (INIS)

    Voiculescu, M; Usoskin, I

    2012-01-01

    A consensus regarding the impact of solar variability on cloud cover is far from being reached. Moreover, the impact of cloud cover on climate is among the least understood of all climate components. This motivated us to analyze the persistence of solar signals in cloud cover for the time interval 1984–2009, covering two full solar cycles. A spatial and temporal investigation of the response of low, middle and high cloud data to cosmic ray induced ionization (CRII) and UV irradiance (UVI) is performed in terms of coherence analysis of the two signals. For some key geographical regions the response of clouds to UVI and CRII is persistent over the entire time interval indicating a real link. In other regions, however, the relation is not consistent, being intermittent or out of phase, suggesting that some correlations are spurious. The constant in phase or anti-phase relationship between clouds and solar proxies over some regions, especially for low clouds with UVI and CRII, middle clouds with UVI and high clouds with CRII, definitely requires more study. Our results show that solar signatures in cloud cover persist in some key climate-defining regions for the entire time period and supports the idea that, if existing, solar effects are not visible at the global level and any analysis of solar effects on cloud cover (and, consequently, on climate) should be done at the regional level. (letter)

  16. Molluscan systematics and biostratigraphy: lower tertiary, La Meseta formation, Seymour Island, Antarctic Peninsula

    National Research Council Canada - National Science Library

    Stilwell, Jeffrey D; Zinsmeister, William J

    1992-01-01

    Contents: The Antarctic research series: statement of objectives - Acknowledgements - Abstract - Introduction - Previous investigations - Stratigraphy - Age of the La Meseta Formation - Biostratigraphy - Depositional environments...

  17. 21 CFR 11.70 - Signature/record linking.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Signature/record linking. 11.70 Section 11.70 Food... RECORDS; ELECTRONIC SIGNATURES Electronic Records § 11.70 Signature/record linking. Electronic signatures and handwritten signatures executed to electronic records shall be linked to their respective...

  18. Changes in bird communities of Admiralty Bay, King George Island (West Antarctic: insights from monitoring data (1977–1996

    Directory of Open Access Journals (Sweden)

    Sierakowski Kazimierz

    2017-06-01

    Full Text Available The paper summarizes results of twenty years of seabird observations carried out between 1977 and 1996 on the western shore of Admiralty Bay (King George Island, South Shetlands, Antarctic. Changes in population size, distribution and phenology of the breeding species as well as the appearance of non-breeding species are reported. A total of 34 species of birds were observed, including 13 breeding species. Among the non-breeding species, four were observed to visit the site regularly, six rarely, and the remaining 11 were observed only occasionally. Among breeding populations, three Pygoscelis penguin species, the main krill consumers, were most numerous. The Adélie Penguin (P. adeliae dominated among the penguins nesting in the investigated areas, reaching 23,661 breeding pairs in 1978. Two other penguin species were less abundant with population sizes of approximately 7,200 breeding pairs for the Chinstrap Penguin (P. antarcticus and 3,100 breeding pairs for the Gentoo Penguin (P. papua in the same year. During the following two decades, breeding populations of pygoscelid species experienced a declining trend and their numbers were reduced by 68.0% for Chinstrap, 67.1% for Gentoo, and 33.9% for Adélie Penguins. The data reported here represent a unique reference basis and provide valuable information about indicator species, suitable for comparison with contemporary observations of bird populations in the Antarctic Peninsula region, a place of rapidly occurring climate changes and intensive harvesting of marine living resources.

  19. First recorded loss of an emperor penguin colony in the recent period of Antarctic regional warming: implications for other colonies.

    Directory of Open Access Journals (Sweden)

    Philip N Trathan

    Full Text Available In 1948, a small colony of emperor penguins Aptenodytes forsteri was discovered breeding on Emperor Island (67° 51' 52″ S, 68° 42' 20″ W, in the Dion Islands, close to the West Antarctic Peninsula (Stonehouse 1952. When discovered, the colony comprised approximately 150 breeding pairs; these numbers were maintained until 1970, after which time the colony showed a continuous decline. By 1999 there were fewer than 20 pairs, and in 2009 high-resolution aerial photography revealed no remaining trace of the colony. Here we relate the decline and loss of the Emperor Island colony to a well-documented rise in local mean annual air temperature and coincident decline in seasonal sea ice duration. The loss of this colony provides empirical support for recent studies (Barbraud & Weimerskirch 2001; Jenouvrier et al 2005, 2009; Ainley et al 2010; Barber-Meyer et al 2005 that have highlighted the vulnerability of emperor penguins to changes in sea ice duration and distribution. These studies suggest that continued climate change is likely to impact upon future breeding success and colony viability for this species. Furthermore, a recent circumpolar study by Fretwell & Trathan (2009 highlighted those Antarctic coastal regions where colonies appear most vulnerable to such changes. Here we examine which other colonies might be at risk, discussing various ecological factors, some previously unexplored, that may also contribute to future declines. The implications of this are important for future modelling work and for understanding which colonies actually are most vulnerable.

  20. Study of the active layer at the Spanish Antarctic station “Gabriel de Castilla”, Deception Island, Antarctica

    International Nuclear Information System (INIS)

    Pablo, M.A. de; Molina, A.; Recio, C.; Ramos, M.; Goyanes, G.; Ropero, M.A.

    2017-01-01

    The degradation of permanent frozen ground (permafrost) and the increase in the thickness of the active layer may be caused both by natural processes (such as global climate change) and by anthropic activity, which changes the natural environmental conditions that allow its existence, as has been widely reported to occur in the northern polar and subpolar regions. In the case of Antarctica, some scientific research stations are located in areas with permafrost, such as the Spanish Antarctic station “Gabriel de Castilla” on Deception Island. In the place where the station is located, an important increase in erosion has been observed in recent years, including the excavation of new gullies and the erosion of the coastal cliffs. In order to develop an initial analysis of the possible effects of the station on the permafrost degradation, ground temperature has been monitored since 2012 and the thickness and of the active layer and the temperature, both inside and beneath the station, have also been sporadically measured. Here we show the results and discuss how the station reduces the freezing of the ground during the winter when the station is closed and facilitates the warming of the ground during the living periods of the station in the Antarctic summer. Those initial results and conclusions make necessary to continue the study of the permafrost and the active layer in the station site by systematic monitoring of the ground temperature and the thickness of the active layer. [es