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Sample records for active west antarctic

  1. Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability

    USGS Publications Warehouse

    Blankenship, D.D.; Bell, R.E.; Hodge, S.M.; Brozena, J.M.; Behrendt, John C.; Finn, C.A.

    1993-01-01

    IT is widely understood that the collapse of the West Antarctic ice sheet (WAIS) would cause a global sea level rise of 6 m, yet there continues to be considerable debate about the detailed response of this ice sheet to climate change1-3. Because its bed is grounded well below sea level, the stability of the WAIS may depend on geologically controlled conditions at the base which are independent of climate. In particular, heat supplied to the base of the ice sheet could increase basal melting and thereby trigger ice streaming, by providing the water for a lubricating basal layer of till on which ice streams are thought to slide4,5. Ice streams act to protect the reservoir of slowly moving inland ice from exposure to oceanic degradation, thus enhancing ice-sheet stability. Here we present aerogeophysical evidence for active volcanism and associated elevated heat flow beneath the WAIS near the critical region where ice streaming begins. If this heat flow is indeed controlling ice-stream formation, then penetration of ocean waters inland of the thin hot crust of the active portion of the West Antarctic rift system could lead to the disappearance of ice streams, and possibly trigger a collapse of the inland ice reservoir.

  2. Aerogeophysical evidence for active volcanism beneath the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Blankenship, Donald D.; Bell, Robin E.; Hodge, Steven M.; Brozena, John M.; Behrendt, John C.

    1993-01-01

    Although it is widely understood that the collapse of the West Antarctic Ice Sheet (WAIS) would cause a global sea-level rise of 6 m, there continues to be considerable debate about the response of this ice sheet to climate change. The stability of the WAIS, which is characterized by a bed grounded well below sea level, may depend on geologically controlled conditions at the base, which are independent of climate. Ice streams moving up to 750 m/yr disperse material from the interior through to the oceans. As these ice streams tend to buffer the reservoir of slow-moving inland ice from exposure to oceanic degradation, understanding the ice-streaming process is important for evaluating WAIS stability. There is strong evidence that ice streams slide on a lubricating layer of water-saturated till. Development of this basal layer requires both water and easily eroded sediments. Active lithospheric extension may elevate regional heat flux, increase basal melting, and trigger ice streaming. If a geologically defined boundary with a sharp contrast in geothermal flux exists beneath the WAIS, ice streams may only be capable of operating as a buffer over a restricted region. Should ocean waters penetrate beyond this boundary, the ice-stream buffer would disappear, possibly triggering a collapse of the inland ice reservoir. Aerogeophysical evidence for active volcanism and elevated heat flux beneath the WAIS near the critical region where ice streaming begins is presented.

  3. Tectonomorphic evolution of Marie Byrd Land - Implications for Cenozoic rifting activity and onset of West Antarctic glaciation

    NASA Astrophysics Data System (ADS)

    Spiegel, Cornelia; Lindow, Julia; Kamp, Peter J. J.; Meisel, Ove; Mukasa, Samuel; Lisker, Frank; Kuhn, Gerhard; Gohl, Karsten

    2016-10-01

    The West Antarctic Rift System is one of the largest continental rifts on Earth. Because it is obscured by the West Antarctic Ice Sheet, its evolution is still poorly understood. Here we present the first low-temperature thermochronology data from eastern Marie Byrd Land, an area that stretches 1000 km along the rift system, in order to shed light on its development. Furthermore, we petrographically analysed glacially transported detritus deposited in the marine realm, offshore Marie Byrd Land, to augment the data available from the limited terrestrial exposures. Our data provide information about the subglacial geology, and the tectonic and morphologic history of the rift system. Dominant lithologies of coastal Marie Byrd Land are igneous rocks that intruded (presumably early Paleozoic) low-grade meta-sedimentary rocks. No evidence was found for un-metamorphosed sedimentary rocks exposed beneath the ice. According to the thermochronology data, rifting occurred in two episodes. The earlier occurred between 100 and 60 Ma and led to widespread tectonic denudation and block faulting over large areas of Marie Byrd Land. The later episode started during the Early Oligocene and was confined to western Pine Island Bay area. This Oligocene tectonic activity may be linked kinematically to previously described rift structures reaching into Bellingshausen Sea and beneath Pine Island Glacier, all assumed to be of Cenozoic age. However, our data provide the first direct evidence for Cenozoic tectonic activity along the rift system outside the Ross Sea area. Furthermore, we tentatively suggest that uplift of the Marie Byrd Land dome only started at 20 Ma; that is, nearly 10 Ma later than previously assumed. The Marie Byrd Land dome is the only extensive part of continental West Antarctica elevated above sea level. Since the formation of a continental ice sheet requires a significant area of emergent land, our data, although only based on few samples, imply that extensive

  4. Evidence for Subglacial Volcanic Activity Beneath the area of the Divide of the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.

    2013-12-01

    There is an increasing body of aeromagnetic, radar ice-sounding, heat flow, subglacial volcanic earthquakes, several exposed active and subglacial volcanoes and other lines of evidence for volcanic activity associated with the West Antarctic Rift System (WR) since the origin (~25 Ma) of the West Antarctic Ice Sheet (WAIS), which flows through it. Exposed late Cenozoic, alkaline volcanic rocks, 34 Ma to present concentrated in Marie Byrd Land (LeMasurier and Thomson, 1990), but also exposed along the rift shoulder on the Transantarctic Mountains flank of the WR, and >1 million cubic kilometers, of mostly subglacially erupted 'volcanic centers' beneath the WAIS inferred from aeromagnetic data, have been interpreted as evidence of a magmatic plume. About 18 high relief, (~600-2000 m) 'volcanic centers' presently beneath the WAIS surface, probably were erupted subaerially when the WAIS was absent, based on the 5-km orthogonally line spaced Central West Antarctica aerogeophysical survey. All would be above sea level after ice removal and isostatic adjustment. Nine of these high relief peaks are in the general area beneath the divide of the WAIS. This high bed relief topography was first interpreted in the 1980s as the volcanic 'Sinuous Ridge ' based on a widely spaced aeromagnetic -radar ice sounding survey (Jankowski et al,. 1983). A 70-km wide, circular ring of interpreted subglacial volcanic rocks was cited as evidence of a volcanic caldera underlying the ice sheet divide based on the CWA survey (Behrendt et al., 1998). A broad magnetic 'low' surrounding the caldera area possibly is evidence of a shallow Curie isotherm. High heat flow reported from temperature logging (Clow et al., 2012) in the WAISCORE and a thick volcanic ash layer in the core (Dunbar et al., 2012) are consistent with this interpretation. A 2 km-high subaerially erupted volcano (subglacial Mt Thiel, ~78.5 degrees S, 111 degrees W) ~ 100 km north from the WAISCORE could be the source of the ash

  5. The ARM West Antarctic Radiation Experiment (AWARE)

    NASA Astrophysics Data System (ADS)

    Lubin, Dan; Bromwich, David; Vogelmann, Andrew; Verlinde, Johannes; Russell, Lynn

    2016-04-01

    West Antarctica is one of the most rapidly warming regions on Earth, and its changing climate in both atmosphere and ocean is linked to loss of Antarctic ice mass and global sea level rise. The specific mechanisms for West Antarctic Ice Sheet (WAIS) warming are not fully understood, but are hypothesized to involve linkage between moisture from Southern Ocean storm tracks and the surface energy balance over the WAIS, and related teleconnections with subtropical and tropical meteorology. This present lack of understanding has motivated a climate science and cloud physics campaign jointly supported by the US National Science Foundation (NSF) and Department of Energy (DOE), called the Atmospheric Radiation Measurement Program (ARM) West Antarctic Radiation Experiment (AWARE). The DOE's second ARM Mobile Facility (AMF2) was deployed to McMurdo Station on Ross Island in November 2015 and will operate through December 2016. The AMF2 includes (1) cloud research radars, both scanning and zenith, operating in the Ka- and X-bands, (2) high spectral resolution and polarized micropulse lidars, and (3) a suite of shortwave and longwave broadband and spectral radiometers. A second suite of instruments is deployed at the WAIS Divide Ice Camp on the West Antarctic plateau during December 2015 and January 2016. The WAIS instrument suite provides (1) measurement of all surface energy balance components, (2) a polarized micropulse lidar and shortwave spectroradiometer, (3) microwave total water column measurement, and (4) four times daily rawinsonde launches which are the first from West Antarctica since 1967. There is a direct linkage between the WAIS instrument suite and the AMF2 at McMurdo, in that air masses originating in Southern Ocean storm tracks that are driven up over the WAIS often subsequently descend over the Ross Ice Shelf and arrive at Ross Island. Preliminary data are already illustrating the prevalence of mixed-phase clouds and their role in the surface energy balance

  6. Patterns of late Cenozoic volcanic and tectonic activity in the West Antarctic rift system revealed by aeromagnetic surveys

    USGS Publications Warehouse

    Behrendt, John C.; Saltus, R.; Damaske, D.; McCafferty, A.; Finn, C.A.; Blankenship, D.; Bell, R.E.

    1996-01-01

    Aeromagnetic surveys, spaced ???5 km, over widely separated areas of the largely ice- and sea-covered West Antarctic rift system, reveal similar patterns of 100- to 1700-nT, shallow-source magnetic anomalies interpreted as evidence of extensive late Cenozoic volcanism. We use the aeromagnetic data to extend the volcanic rift interpretation over West Antarctica starting with anomalies over (1) exposures of highly magnetic, late Cenozoic volcanic rocks several kilometers thick in the McMurdo-Ross Island area and elsewhere; continuing through (2) volcanoes and subvolcanic intrusions directly beneath the Ross Sea continental shelf defined by marine magnetic and seismic reflection data and aeromagnetic data and (3) volcanic structures interpreted beneath the Ross Ice Shelf partly controlled by seismic reflection determinations of seafloor depth to (4) an area of similar magnetic pattern over the West Antarctic Ice Sheet (400 km from the nearest exposed volcanic rock), where interpretations of late Cenozoic volcanic rocks at the base of the ice are controlled in part by radar ice sounding. North trending magnetic rift fabric in the Ross Sea-Ross Ice Shelf and Corridor Aerogeophysics of the Southeast Ross Transect Zone (CASERTZ) areas, revealed by the aeromagnetic surveys, is probably a reactivation of older rift trends (late Mesozoic?) and is superimposed on still older crosscutting structural trends revealed by magnetic terrace maps calculated from horizontal gradient of pseudogravity. Longwavelength (???100-km wide) magnetic terraces from sources within the subvolcanic basement cross the detailed survey areas. One of these extends across the Ross Sea survey from the front of the Transantarctic Mountains with an east-southeast trend crossing the north trending rift fabric. The Ross Sea-Ross Ice Shelf survey area is characterized by highly magnetic northern and southern zones which are separated by magnetically defined faults from a more moderately magnetic central zone

  7. Marine pelagic ecosystems: the west Antarctic Peninsula.

    PubMed

    Ducklow, Hugh W; Baker, Karen; Martinson, Douglas G; Quetin, Langdon B; Ross, Robin M; Smith, Raymond C; Stammerjohn, Sharon E; Vernet, Maria; Fraser, William

    2007-01-29

    The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba. Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 2 degrees C increase in the annual mean temperature and a 6 degrees C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.6 degrees C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in icedependent Adélie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate

  8. Marine pelagic ecosystems: the West Antarctic Peninsula

    PubMed Central

    Ducklow, Hugh W; Baker, Karen; Martinson, Douglas G; Quetin, Langdon B; Ross, Robin M; Smith, Raymond C; Stammerjohn, Sharon E; Vernet, Maria; Fraser, William

    2006-01-01

    The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba. Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 2°C increase in the annual mean temperature and a 6°C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.6°C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in ice-dependent Adélie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate/ecological gradients

  9. Holocene glacial activity in Barilari Bay, west Antarctic Peninsula, tracked by magnetic mineral assemblages: Linking ice, ocean, and atmosphere

    NASA Astrophysics Data System (ADS)

    Reilly, Brendan T.; Natter, Carl J.; Brachfeld, Stefanie A.

    2016-11-01

    We investigate the origin and fate of lithogenic sediments using magnetic mineral assemblages in Barilari Bay, west Antarctic Peninsula (AP) from sediment cores recovered during the Larsen Ice Shelf System, Antarctica (LARISSA) NBP10-01 cruise. To quantify and reconstruct Holocene changes in covarying magnetic mineral assemblages, we adopt an unsupervised mathematical unmixing strategy and apply it to measurements of magnetic susceptibility as a function of increasing temperature. Comparisons of the unmixed end-members with magnetic observations of northwestern AP bedrock and the spatial distribution of magnetic mineral assemblages within the fjord, allow us to identify source regions, including signatures for "inner bay," "outer bay," and "northwestern AP" sources. We find strong evidence that supports the establishment of a late Holocene ice shelf in the fjord coeval with the Little Ice Age. Additionally, we present new evidence for late Holocene sensitivity to conditions akin to positive mean Southern Annual Mode states for western AP glaciers at their advanced Neoglacial positions.

  10. Bacteria beneath the West Antarctic ice sheet.

    PubMed

    Lanoil, Brian; Skidmore, Mark; Priscu, John C; Han, Sukkyun; Foo, Wilson; Vogel, Stefan W; Tulaczyk, Slawek; Engelhardt, Hermann

    2009-03-01

    Subglacial environments, particularly those that lie beneath polar ice sheets, are beginning to be recognized as an important part of Earth's biosphere. However, except for indirect indications of microbial assemblages in subglacial Lake Vostok, Antarctica, no sub-ice sheet environments have been shown to support microbial ecosystems. Here we report 16S rRNA gene and isolate diversity in sediments collected from beneath the Kamb Ice Stream, West Antarctic Ice Sheet and stored for 15 months at 4 degrees C. This is the first report of microbes in samples from the sediment environment beneath the Antarctic Ice Sheet. The cells were abundant ( approximately 10(7) cells g(-1)) but displayed low diversity (only five phylotypes), likely as a result of enrichment during storage. Isolates were cold tolerant and the 16S rRNA gene diversity was a simplified version of that found in subglacial alpine and Arctic sediments and water. Although in situ cell abundance and the extent of wet sediments beneath the Antarctic ice sheet can only be roughly extrapolated on the basis of this sample, it is clear that the subglacial ecosystem contains a significant and previously unrecognized pool of microbial cells and associated organic carbon that could potentially have significant implications for global geochemical processes.

  11. West antarctic ice sheet collapse: Chimera or clear danger

    SciTech Connect

    Alley, R.B. ); MacAyeal, D.R. )

    1993-01-01

    The specter of a west antarctic collapse has been with us for 25 years. Recently, certain official assessments concerned primarily with the future response to projected global warming have concluded that Antarctica will not cause much sea-level rise within the planning horizon of a century or so. At the same time startling new results on ice sheet (in)stability have been emerging, pointing to less stability then previously believed. Some recent results are reviewed briefly: Heinrich layers in the North Atlantic show basally lubricated surges of the Laurentide ice sheet; the west antarctic ice sheet collapsed recently; the modern west antarctic ice sheet is changing rapidly locally; the bed of ice stream B is exceptionally well lubricated by water and water-saturated soft sediments; the modern ice sheet is thinning slowly on average; a model west antarctic ice sheet undergoes rapid collapses long after forcing and probably related to penetration of warmth to the bed. 23 refs.

  12. A microbial ecosystem beneath the West Antarctic ice sheet.

    PubMed

    Christner, Brent C; Priscu, John C; Achberger, Amanda M; Barbante, Carlo; Carter, Sasha P; Christianson, Knut; Michaud, Alexander B; Mikucki, Jill A; Mitchell, Andrew C; Skidmore, Mark L; Vick-Majors, Trista J

    2014-08-21

    Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes that can mobilize elements from the lithosphere and influence Southern Ocean geochemical and biological systems.

  13. West Antarctic Ice Sheet Initiative. Volume 2: Discipline Reviews

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert A. (Editor)

    1991-01-01

    Seven discipline review papers are presented on the state of the knowledge of West Antarctica and opinions on how that knowledge must be increased to predict the future behavior of this ice sheet and to assess its potential to collapse, rapidly raising the global sea level. These are the goals of the West Antarctic Ice Sheet Initiative (WAIS).

  14. Crustal and lithospheric structure of the west Antarctic Rift System from geophysical investigations: a review

    USGS Publications Warehouse

    Behrendt, John C.

    1999-01-01

    The active West Antarctic Rift System, which extends from the continental shelf of the Ross Sea, beneath the Ross Ice Shelf and the West Antarctic Ice Sheet, is comparable in size to the Basin and Range in North America, or the East African rift systems. Geophysical surveys (primarily marine seismic and aeromagnetic combined with radar ice sounding) have extended the information provided by sparse geologic exposures and a few drill holes over the ice and sea covered area. Rift basins developed in the early Cretaceous accompanied by the major extension of the region. Tectonic activity has continued episodically in the Cenozoic to the present, including major uplift of the Transantarctic Mountains. The West Antarctic ice sheet, and the late Cenozoic volcanic activity in the West Antarctic Rift System, through which it flows, have been coeval since at least Miocene time. The rift is characterized by sparse exposures of late Cenozoic alkaline volcanic rocks extending from northern Victoria Land throughout Marie Byrd Land. The aeromagnetic interpretations indicate the presence of > 5 x 105 km2 (> 106 km3) of probable late Cenozoic volcanic rocks (and associated subvolcanic intrusions) in the West Antarctic rift. This great volume with such limited exposures is explained by glacial removal of the associated late Cenozoic volcanic edifices (probably hyaloclastite debris) concomitantly with their subglacial eruption. Large offset seismic investigations in the Ross Sea and on the Ross Ice Shelf indicate a ~ 17-24-km-thick, extended continental crust. Gravity data suggest that this extended crust of similar thickness probably underlies the Ross Ice Shelf and Byrd Subglacial Basin. Various authors have estimated maximum late Cretaceous-present crustal extension in the West Antarctic rift area from 255-350 km based on balancing crustal thickness. Plate reconstruction allowed < 50 km of Tertiary extension. However, paleomagnetic measurements suggested about 1000 km of post

  15. Influence of West Antarctic Ice Sheet collapse on Antarctic surface climate

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    Climate model simulations are used to examine the impact of a collapse of the West Antarctic Ice Sheet (WAIS) on the surface climate of Antarctica. The lowered topography following WAIS collapse produces anomalous cyclonic circulation with increased flow of warm, maritime air toward the South Pole and cold-air advection from the East Antarctic plateau toward the Ross Sea and Marie Byrd Land, West Antarctica. Relative to the background climate, areas in East Antarctica that are adjacent to the WAIS warm, while substantial cooling (several °C) occurs over parts of West Antarctica. Anomalously low isotope-paleotemperature values at Mount Moulton, West Antarctica, compared with ice core records in East Antarctica, are consistent with collapse of the WAIS during the last interglacial period, Marine Isotope Stage 5e. More definitive evidence might be recoverable from an ice core record at Hercules Dome, East Antarctica, which would experience significant warming and positive oxygen isotope anomalies if the WAIS collapsed.

  16. Intermittent signature of ENSO in west-Antarctic precipitation

    NASA Astrophysics Data System (ADS)

    Genthon, Christophe; Cosme, Emmanuel

    2003-11-01

    Precipitation data from the new ERA40 reanalyses and from a 200-year simulation confirm a robust main mode of precipitation variability in west Antarctica. An intermittently strong ENSO signature is found in this mode. However, high correlation with ENSO indices appears infrequent. Thus, the high correlation found in ERA40, and previously in other chronologically realistic data, in the late 1980s and the 1990s may not be expected to last. Unlike previously suggested by others, the sign of the correlation between ENSO indices and west Antarctic precipitation, when significant, does not appear to change in time: Precipitation variability at the ENSO pace in the Bellingshausen-Weddell (Ross-Amunsden) region is consistently in phase (phase opposition, respectively) with the Southern Oscillation Index. This is consistent with a tropospheric wave train connecting the tropical Pacific and west Antarctic regions, which modulates in phase opposition the advection of air and moisture in the 2 regions.

  17. Tectonics and ice sheet dynamics of West Antarctic margins

    NASA Astrophysics Data System (ADS)

    Gohl, Karsten

    2010-05-01

    An understanding of the glacial history of the Amundsen Sea Embayment (ASE) and Pine Island Bay (PIB) is essential for proposing models on the future development of the West Antarctic Ice Sheet. This requires an understanding of the tectonic history and knowledge of tectonic features such as lineaments, ridges, sills and basins, because basement morphology and inherited erosional features control the flow direction of ice-sheets and the influx of Circum-Polar Deep Water (CDW). This is an attempt to reconstruct the tectonic history with the aim to search for basement features and crustal boundaries which may be correlated to the flow and dynamics of the ice-sheet. The Amundsen Sea Embayment of West Antarctica is in a prominent location for a series of tectonic and magmatic events from Paleozoic to Cenozoic times. Seismic, magnetic and gravity data from the embayment and PIB reveal the crustal thickness and significant tectonic features. NE-SW trending magnetic and gravity anomalies and the thin crust indicate a former rift zone which was active during or in the run-up to the breakup process between Chatham Rise and West Antarctica before or at 90 Ma. NW-SE trending gravity and magnetic anomalies, following a prolongation of Peacock Sound, indicate the extensional southern boundary to the Bellingshausen Plate which was active between 79 and 61 Ma. It is likely that the prominent Pine Island Trough follows a structural boundary between the crustal blocks of Ellsworth Land and Marie Byrd Land. Data are shown from the ASE and PIB which can be interpreted in context with the reconstruction of the ice advance and retreat history in this area. Differences in the behaviour of the ice-sheet are shown to exist for the western and eastern parts of PIB due to basement structures affecting the inflow of CDW.

  18. Effect of subglacial volcanism on changes in the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Behrendt, John C.

    1993-01-01

    Rapid changes in the West Antarctic Ice Sheet (WAIS) may affect future global sea-level changes. Alley and Whillans note that 'the water responsible for separating the glacier from its bed is produced by frictional dissipation and geothermal heat,' but assume that changes in geothermal flux would ordinarily be expected to have slower effects than glaciological parameters. I suggest that episodic subglacial volcanism and geothermal heating may have significantly greater effects on the WAIS than is generally appreciated. The WAIS flows through the active, largely asiesmic West Antarctic rift system (WS), which defines the sub-sea-level bed of the glacier. Various lines of evidence summarized in Behrendt et al. (1991) indicate high heat flow and shallow asthenosphere beneath the extended, weak lithosphere underlying the WS and the WAIS. Behrendt and Cooper suggest a possible synergistic relation between Cenozoic tectonism, episodic mountain uplift and volcanism in the West Antarctic rift system, and the waxing and waning of the Antarctic ice sheet beginning about earliest Oligocene time. A few active volcanoes and late-Cenozoic volcanic rocks are exposed throughout the WS along both flanks, and geophysical data suggest their presence beneath the WAIS. No part of the rift system can be considered inactive. I propose that subglacial volcanic eruptions and ice flow across areas of locally (episodically?) high heat flow--including volcanically active areas--should be considered possibly to have a forcing effect on the thermal regime resulting in increased melting at the base of the ice streams.

  19. The First Annual West Antarctic Ice Sheet (WAIS) Science Workshop

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert A. (Editor)

    1993-01-01

    A compilation of abstracts presented at the workshop are presented. The goal was to answer the question, what is the future behavior and potential for rapid collapse of the West Antarctic Ice Sheet (WAIS)? The workshop was organized into four sessions corresponding to the four objectives identified as necessary to reach the WAIS workshop goal: history, current behavior, internal dynamics, and environmental interactions. Presentations were organized by their relevance to each objective, rather than by discipline.

  20. Modeled Aeromagnetic Anomalies, Controlled By Radar Ice Sounding, As Evidence for Subglacial Volcanic Activity in the West Antarctic Rift System (WR) Beneath the Area of the Divide of the West Antarctic Ice Sheet (WAIS)

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.

    2014-12-01

    The Thwaites and Pine Island ice shelves, buttressing the WAIS, have passed the turning point as they are eaten away by warmer ocean waters (Joghin et al., 2014; Rignot et al., 2014). There is an increasing evidence (aeromagnetic, radar ice-sounding, high heat flow, subglacial volcanic seismicity, and several exposed and subglacial active volcanoes), for volcanic activity in the WR beneath the WAIS, which flows through it. The 5-km, orthogonally line spaced, central West Antarctica (CWA) aerogeophysical survey defined >400 high amplitude volcanic magnetic anomalies correlated with glacial bed topography. Modeled anomalies defined magnetic properties; interpreted volcanic edifices were mostly removed by the moving ice into which they were erupted. Very high apparent susceptibility contrasts (.001->.3 SI) are typical of measured properties from volcanic exposures in the WAIS area. About 90% of the magnetic sources have normal magnetization in the present field direction. Two explanations as to why the anomalies are not approximately 50% negative: (1) Volcanic activity resulting in these anomalies occurred in a predominantly normal field (unlikely). (2) Sources are a combination of induced and remanent magnetization resulting in anomalies of low amplitude (induced cancels remanent) and are not recognized because they are <100 nT (most probable). About 18 high relief, (~600-2000 m) "volcanic centers" beneath the WAIS surface, probably were erupted subaerially when the WAIS was absent; nine of these are in the general area beneath the divide of the WAIS. A 70-km wide, ring of interpreted subglacial volcanic rocks may define a volcanic caldera underlying thedivide (Behrendt et al., 1998). A 2 km-high subaerially erupted volcano (subglacial Mt Thiel, ~78o30'S, 111oW) ~ 100 km north of the WAISCORE, could be the source an ash layer observed in the core. Models by Tulaczyk and Hossainzadeh (2011) indicate >4mm/yr basal melting beneath the WAIS, supportive of high heat flow

  1. Geologic controls on the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Anandakrishnan, Sridhar

    1993-01-01

    The stability of the West Antarctic Ice Sheet is intertwined with its geologic history. The sub-ice geology and the possibility of active rifting and associated elevated heat-flux and volcanism might be determining factors in ice-sheet behavior. Seismic monitoring of natural events at the base of Ice Stream C reveals the presence of a young sedimentary basin beneath the ice stream. The sediments are presumed to be of glacio-marine origin, similar to those beneath Ice Stream B and in the Ross Sea. The young sediments are approximately 1/2 km thick at UpC camp, but thin abruptly southward to 100 m or less. We hypothesize the presence of a fault with a throw of 400 m to account for this (though we have not directly detected the fault), rather than invoking unrealistic basement dips. To extend these studies to critical inland regions, we suggest an expanded explosive-source seismic survey of the Byrd Subglacial Basin to determine the extent and character of the hypothesized rift basin. High-resolution seismic monitoring will detect layering in the sedimentary column, as well as possibly imaging faults directly.

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

    SciTech Connect

    Lubin, D; Bromwich, DH; Russell, LM; Verlinde, J; Vogelmann, AM

    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

  3. CASERTZ aeromagnetic data reveal late Cenozoic flood basalts (?) in the West Antarctic rift system

    USGS Publications Warehouse

    Behrendt, John C.

    1994-01-01

    The late Cenozoic volcanic and tectonic activity of the enigmatic West Antarctic rift system, the least understood of the great active continental rifts, has been suggested to be plume driven. In 1991-1992, as part of the CASERTZ (Corridor Aerogeophysics of the Southeast Ross Transect Zone) program, an ~25 000 km aeromagnetic survey over the ice-covered Byrd subglacial basin shows magnetic "texture' critical to interpretations of the underlying extended volcanic terrane. The aeromagnetic data reveal numerous semicircular anomalies ~100-1100 nT in amplitude, interpreted as having volcanic sources at the base of the ice sheet; they are concentrated along north-trending magnetic lineations interpreted as rift fabric. The CASERTZ aeromagnetic results, combined with >100 000 km of widely spaced aeromagnetic profiles, indicate at least 106 km3 of probable late Cenozoic volcanic rock (flood basalt?) in the West Antarctic rift beneath the ice sheet and Ross Ice Shelf. -from Authors

  4. Irregular oscillations of the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Macayeal, Douglas R.

    1993-01-01

    Model simulations of the West Antarctic ice sheet suggest that sporadic, perhaps chaotic, collapse (complete mobilization) of the ice sheet occurred throughout the past one million years. The irregular behavior is due to the slow equilibration time of the distribution of basal till, which lubricates ice-sheet motion. This nonlinear response means that predictions of future collapse of the ice sheet in response to global warming must take into account its past history, and in particular, whether the present basal till distribution predisposes the ice sheet towards rapid change.

  5. Tributaries of West Antarctic Ice Streams Revealed by RADARSAT Interferometry.

    PubMed

    Joughin; Gray; Bindschadler; Price; Morse; Hulbe; Mattar; Werner

    1999-10-08

    Interferometric RADARSAT data are used to map ice motion in the source areas of four West Antarctic ice streams. The data reveal that tributaries, coincident with subglacial valleys, provide a spatially extensive transition between slow inland flow and rapid ice stream flow and that adjacent ice streams draw from shared source regions. Two tributaries flow into the stagnant ice stream C, creating an extensive region that is thickening at an average rate of 0.49 meters per year. This is one of the largest rates of thickening ever reported in Antarctica.

  6. Radar studies of the West Antarctic ice streams

    NASA Technical Reports Server (NTRS)

    Jacobel, Robert W.

    1993-01-01

    A collaboration has carried out measurements of ice thickness at the mouth of Ice Streams D and E, West Antarctica, using a surface-based impulse radar. These studies were undertaken as a part of the continuing effort to understand the state of the West Antarctic Ice Sheet and its response to climate change. Thickness measurements will be used in the mass balance calculation currently in progress and to better understand features in the surface topography seen at low-angle sun illumination in the satellite imagery. Results show that the discharge areas of Ice Streams D and E are thickening by approximately 1 meter per year, and thus that these ice streams are likely losing mass. Aperiodic wavelike features in the surface topography are described, which pose interesting questions about migration of the grounding line and ice-stream dynamics.

  7. Obliquity-paced Pliocene West Antarctic ice sheet oscillations

    USGS Publications Warehouse

    Naish, T.; Powell, R.; Levy, R.; Wilson, G.; Scherer, R.; Talarico, F.; Krissek, L.; Niessen, F.; Pompilio, M.; Wilson, T.; Carter, L.; DeConto, R.; Huybers, P.; McKay, R.; Pollard, D.; Ross, J.; Winter, D.; Barrett, P.; Browne, G.; Cody, R.; Cowan, E.; Crampton, J.; Dunbar, G.; Dunbar, N.; Florindo, F.; Gebhardt, C.; Graham, I.; Hannah, M.; Hansaraj, D.; Harwood, D.; Helling, D.; Henrys, S.; Hinnov, L.; Kuhn, G.; Kyle, P.; Laufer, A.; Maffioli, P.; Magens, D.; Mandernack, K.; McIntosh, W.; Millan, C.; Morin, R.; Ohneiser, C.; Paulsen, T.; Persico, D.; Raine, I.; Reed, J.; Riesselman, C.; Sagnotti, L.; Schmitt, D.; Sjunneskog, C.; Strong, P.; Taviani, M.; Vogel, S.; Wilch, T.; Williams, T.

    2009-01-01

    Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch (???5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ???40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ???3??C warmer than today and atmospheric CO 2 concentration was as high as ???400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO2. ??2009 Macmillan Publishers Limited. All rights reserved.

  8. Obliquity-paced Pliocene West Antarctic ice sheet oscillations.

    PubMed

    Naish, T; Powell, R; Levy, R; Wilson, G; Scherer, R; Talarico, F; Krissek, L; Niessen, F; Pompilio, M; Wilson, T; Carter, L; DeConto, R; Huybers, P; McKay, R; Pollard, D; Ross, J; Winter, D; Barrett, P; Browne, G; Cody, R; Cowan, E; Crampton, J; Dunbar, G; Dunbar, N; Florindo, F; Gebhardt, C; Graham, I; Hannah, M; Hansaraj, D; Harwood, D; Helling, D; Henrys, S; Hinnov, L; Kuhn, G; Kyle, P; Läufer, A; Maffioli, P; Magens, D; Mandernack, K; McIntosh, W; Millan, C; Morin, R; Ohneiser, C; Paulsen, T; Persico, D; Raine, I; Reed, J; Riesselman, C; Sagnotti, L; Schmitt, D; Sjunneskog, C; Strong, P; Taviani, M; Vogel, S; Wilch, T; Williams, T

    2009-03-19

    Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch ( approximately 5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, approximately 40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to approximately 3 degrees C warmer than today and atmospheric CO(2) concentration was as high as approximately 400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO(2).

  9. Latest Word on Retreat of the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Bindschadler, R.

    2000-01-01

    The West Antarctic ice sheet during the Last Glacial Maximum (LGM) is estimated to have been three times its present volume and to have extended close to the edge of the continental shelf Holocene retreat of this ice sheet in the Ross Sea began between 11,000 and 12,000 years ago. This history implies an average contribution of this ice sheet to sea level of 0.9 mm/a. Evidence of dateable past grounding line positions in the Ross sector are broadly consistent with a linear retreat model. However, inferred rates of retreat for some of these grounding line positions are not consistent with a linear retreat model. More rapid retreat approximately 7600 years ago and possible near-stability in the Ross Sea sector at present suggest a slow rate of initial retreat followed by a more rapid-than-average retreat during the late Holocene, returning to a near-zero rate of retreat currently. This model is also consistent with the mid-Holocene high stand observations of eustatic sea level. Recent compilation of Antarctic bed elevations (BEDMAP) illustrates that the LGM and present grounding lines occur in the shallowest waters, further supporting the model of a middle phase of rapid retreat bracketed by an older and a more recent phase of modest retreat. Extension of these hypotheses into the future make subsequent behavior of the West Antarctic ice sheet more difficult to predict but suggest that if it loses its hold on the present shallow bed, the final retreat of the ice sheet could be very rapid.

  10. Where is the West Antarctic Rift System in the Amundsen Sea and Bellingshausen Sea sectors?

    NASA Astrophysics Data System (ADS)

    Gohl, Karsten; Kalberg, Thomas; Eagles, Graeme; Dziadek, Ricarda; Kaul, Norbert; Spiegel, Cornelia; Lindow, Julia

    2015-04-01

    The West Antarctic Rift System (WARS) is one of the largest continental rifts globally, but its lateral extent, distribution of local rifts, timing of rifting phases, and mantle processes are still largely enigmatic. It has been presumed that the rift and its crustal extensional processes have widely controlled the history and development of West Antarctic glaciation with an ice sheet of which most is presently based at sub-marine level and which is, therefore, likely to be highly sensitive to ocean warming. While the western domain of the WARS in the Ross Sea has been studied in some detail, only recently have various geophysical and geochemical/thermochronological analyses revealed indications for its eastern extent in the Amundsen Sea and Bellingshausen Sea sectors of the South Pacific realm. The current model, based on these studies and additional data, suggests that the WARS activity included tectonic translateral, transtensional and extensional processes from the Amundsen Sea Embayment to the Bellingshausen Sea region of the southern Antarctic Peninsula. We present the range of existing hypotheses regarding the extent of the eastern WARS as well as published and yet unpublished data that support a conceptual WARS model for the eastern West Antarctica with implications for glacial onset and developments.

  11. A Maturing Tephra Record in the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Dunbar, N. W.; Kurbatov, A.; McIntosh, W. C.

    2011-12-01

    Tephra layers found in many Antarctic ice cores range from sub-centimeter thick, visible layers to cryptotephra consisting of sparse, fine-grained (<10 micron) glass particles. Location of tephra particles has improved with advances in methods of detecting cryptotephra in ice cores. Identification of tephra layers traditionally relied on visible detection or association with sulfate aerosols, but is now supplemented by downhole optical logging (Bay et al., 2001). Improved analytical techniques for glass characterization, such as high quality quantitative electron microprobe analysis, and more complete information on source eruptions has facilitated identification of tephra horizons in ice cores. Two deep ice cores drilled in West Antarctica (Siple Dome and WAIS Divide) contain rich tephra records, with the former containing 37 tephra layers and the latter containing several hundred distinct, visible layers, many of which are likely to be tephra. Most of the tephra layers with strong correlations to sources are derived from Antarctic volcanoes, many from two large West Antarctic stratovolcanoes Mt. Berlin and Mt. Takahe, tephra from which have also been recognized in the marine record (Hillenbrand et al., 1988). A well-defined ash layer is found at a depth of between 190.37-190.39 m depth in the WAIS Divide core, containing 20 um ash shards that are chemically correlated to the the Pleaides volcanoes, in northern Victoria Land. This tephra layer correlates to one found in a Siple Dome (B) ice core (97.2 to 97.7 m depth) and in the Taylor Dome ice core (79.2 m depth). Deeper parts of the WAIS Divide ice core correspond to a time interval of abundant regional volcanism, represented by the large number of visible dust bands and cloudy layers in the core (A. Orsi, pers. comm., 2010). A distinct "visible brown layer" at a depth of 1586.363 m. (8.279 Ky BP preliminary age) is very likely to be from a major eruption of the West Antarctic volcano Mt. Takahe (8.2±5

  12. Geophysical studies of the West Antarctic Rift System

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.; Lemasurier, W. E.; Cooper, A. K.; Tessensohn, F.; TréHu, A.; Damaske, D.

    1991-12-01

    The West Antarctic rift system extends over a 3000 × 750 km, largely ice covered area from the Ross Sea to the base of the Antarctic Peninsula, comparable in area to the Basin and Range and the East African rift system. A spectacular rift shoulder scarp along which peaks reach 4-5 km maximum elevation marks one flank and extends from northern Victoria Land-Queen Maud Mountains to the Ellsworth-Whitmore-Horlick Mountains. The rift shoulder has maximum present physiographic relief of 5 km in the Ross Embayment and 7 km in the Ellsworth Mountains-Byrd Subglacial Basin area. The Transantarctic Mountains part of the rift shoulder (and probably the entire shoulder) has been interpreted as rising since about 60 Ma, at episodic rates of ˜1 km/m.y., most recently since mid-Pliocene time, rather than continuously at the mean rate of 100 m/m.y. The rift system is characterized by bimodal alkaline volcanic rocks ranging from at least Oligocene to the present. These are exposed asymmetrically along the rift flanks and at the south end of the Antarctic Peninsula. The trend of the Jurassic tholeiites (Ferrar dolerites, Kirkpatric basalts) marking the Jurassic Transantarctic rift is coincident with exposures of the late Cenozoic volcanic rocks along the section of the Transantarctic Mountains from northern Victoria Land to the Horlick Mountains. The Cenozoic rift shoulder diverges here from the Jurassic tholeiite trend, and the tholeiites are exposed continuously (including the Dufek intrusion) along the lower- elevation (1-2 km) section of Transantarctic Mountains to the Weddell Sea. Widely spaced aeromagnetic profiles in West Antarctica indicate the absence of Cenozoic volcanic rocks in the ice covered part of the Whitmore-Ellsworth-Mountain block and suggest their widespread occurrence beneath the western part of the ice sheet overlying the Byrd Subglacial Basin. A German Federal Institute for Geosciences and Natural Resources (BGR)-U.S. Geological Survey (USGS) aeromagnetic

  13. Subglacial volcanic features beneath the West Antarctic Ice Sheet interpreted from aeromagnetic and radar ice sounding

    USGS Publications Warehouse

    Behrendt, John C.; Blankenship, D.D.; Morse, D.L.; Finn, C.A.; Bell, R.E.

    2002-01-01

    The West Antarctic Ice Sheet (WAIS) flows through the volcanically active, late Cenozoic West Antarctic rift system. Active subglacial volcanism and a vast (>106 km3) extent of subglacial volcanic structures have been interpreted from aerogeophysical surveys over central West Antarctica in the past decade, combined with results from 1960s and 1970s aeromagnetic profiles over the WAIS. Modelling of magnetic anomalies constrained by radar ice sounding shows volcanic sources at the base of the ice throughout large areas, whose subglacially erupted hyaloclastite edifices have been eroded by moving ice, as in Iceland. The 1800 m-high divide of the WAIS is underlain by the 400 km-long volcanic Sinuous Ridge, which rises above sea level; most hyaloclastite edifices there have also been glacially removed, indicating migration of the ice divide through time. Northeast of the divide of the WAIS there is a 400-nT positive magnetic anomaly over the shallowest, most rugged bedrock topography (elevation +380 m above sea level), probably comprising subaerially erupted flows erupted when the Sinuous Ridge area was deglaciated. Uplift of the Sinuous Ridge may have forced the advance of the WAIS. Other aspects of the subglacial volcanism in Antarctica can be observed in Iceland and have a direct bearing on our understanding of the subglacial conditions of the WAIS and its dynamics.

  14. A recent sea-ice retreat west of the Antarctic Peninsula

    NASA Technical Reports Server (NTRS)

    Jacobs, Stan S.; Comiso, Joey C.

    1993-01-01

    Satellite passive microwave data show a record decrease in sea ice extent in the Bellingshausen Sea from mid-1988 through early 1991. The change coincides with more southerly surface winds, increased cyclonic activity and rising surface air temperatures, which reached historic highs along the west coast of the Antarctic Peninsula in 1989. Preceded by high ice cover in 1986-87, the retreat was most evident during summer in the formerly perennial sea-ice field over the continental shelf. Ocean heat storage probably contributed to the persistence and coastal propagation of this anomaly.

  15. A review of precipitation-related aspects of West Antarctic meteorology

    NASA Technical Reports Server (NTRS)

    Bromwich, David H.; Carleton, Andrew M.; Parish, Thomas R.

    1991-01-01

    An overview is presented of the factors associated with snowfall over the West Antarctic Ice Sheet. The flux of atmospheric moisture across the coast, the synoptic processes over the South Pacific Ocean, the large scale atmospheric controls, and numerical modeling of the West Antarctic environment are all discussed. Suggestions are made for research needed to substantially upgrade the status of knowledge in these closely interrelated topic areas.

  16. Accelerated West Antarctic ice mass loss continues to outpace East Antarctic gains

    NASA Astrophysics Data System (ADS)

    Harig, Christopher; Simons, Frederik J.

    2015-04-01

    While multiple data sources have confirmed that Antarctica is losing ice at an accelerating rate, different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy, spatio-temporal resolution, and coverage. Some scope remains for methodological improvements using a single data type. In this study we report our progress in increasing the accuracy and spatial resolution of time-variable gravimetry from the Gravity Recovery and Climate Experiment (GRACE). We determine the geographic pattern of ice mass change in Antarctica between January 2003 and June 2014, accounting for glacio-isostatic adjustment (GIA) using the IJ05_R2 model. Expressing the unknown signal in a sparse Slepian basis constructed by optimization to prevent leakage out of the regions of interest, we use robust signal processing and statistical estimation methods. Applying those to the latest time series of monthly GRACE solutions we map Antarctica's mass loss in space and time as well as can be recovered from satellite gravity alone. Ignoring GIA model uncertainty, over the period 2003-2014, West Antarctica has been losing ice mass at a rate of - 121 ± 8 Gt /yr and has experienced large acceleration of ice mass losses along the Amundsen Sea coast of - 18 ± 5 Gt /yr2, doubling the mass loss rate in the past six years. The Antarctic Peninsula shows slightly accelerating ice mass loss, with larger accelerated losses in the southern half of the Peninsula. Ice mass gains due to snowfall in Dronning Maud Land have continued to add about half the amount of West Antarctica's loss back onto the continent over the last decade. We estimate the overall mass losses from Antarctica since January 2003 at - 92 ± 10 Gt /yr.

  17. Melting West Antarctic ice-shelves: role of coastal warming versus changes in cavity geometries

    NASA Astrophysics Data System (ADS)

    Jourdain, Nicolas; Mathiot, Pierre; Durand, Gael; Le Sommer, Julien; Spence, Paul

    2015-04-01

    The mass loss of West Antarctic glaciers has accelerated over the last 15 years, most likely in response to ocean warming in Antarctic coastal waters. This oceanic warming in Antarctic coastal waters has recently been suggested to be caused by the positive trend of the Southern Annular Mode. But the mechanisms controlling he changes in melt rates underneath outlet glaciers are still poorly understood. For instance, despite recent developments in glacier modeling, melt rates are usually prescribed in glacier models. This strongly limits the ability of glacier models to predict the future evolution of West Antarctic glaciers. Several ocean models are now able to simulate ocean circulation beneath ice-shelves, therefore allowing a direct study of the mechanisms controlling the changes in melting rates underneath outlet glaciers. Building upon these developments, we here investigate the relative influence of ocean warming in coastal waters and changes in ice-shelves cavern geometries on melting rates underneath West Antarctic glaciers. To this purpose, we use a regional ocean/sea-ice model configuration based on NEMO, centered on the Admundsen sea, that explicitly represents flows in ice-shelves cavities. A series of sensitivity experiments is conducted with different cavern geometries and under different atmospheric forcing scenarios in order to identify the leading mechanism controlling the changes in melt rates underneath West Antarctic glaciers over the 21st century. Our results provide a first assessment on the importance of coupling glacier models to ocean models for predicting the future evolution of outlet glaciers.

  18. 76 FR 9849 - Comprehensive Environmental Evaluations for Antarctic Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-22

    .... SUPPLEMENTARY INFORMATION: Article 3 of Annex I to the Protocol on Environmental Protection to the Antarctic Treaty requires the preparation of a CEE for any proposed Antarctic activity likely to have more than a... Comprehensive Environmental Evaluations for Antarctic Activities SUMMARY: The Department of State gives...

  19. Cenozoic transtension along the Transantarctic Mountains-West Antarctic rift boundary, southern Victoria Land, Antarctica, Ohio

    NASA Astrophysics Data System (ADS)

    Wilson, Terry J.

    1995-04-01

    Brittle fault arrays mapped along the structural boundary between the Transantarctic Mountains and the West Antarctic rift system are oriented obliquely to the axis of the mountains and offshore rift basins. The north to northwest trending regional rift boundary is thus not controlled by continuous rift border faults. Instead, the rift margin trend must be imposed by inherited lithospheric weaknesses along the ancestral East Antarctic craton margin. Fault kinematic solutions indicate that a dextral transtensional regime characterized the rift boundary in the Cenozoic and that dominantly transcurrent motion occurred during the most recent faulting episode. The Transantarctic Mountains are considered to be a rift-flank uplift, yet no substantial isostatic uplift is expected in a transtensional setting, and the mechanism of large-magnitude Cenozoic uplift of the mountains remains problematical. Regional deformation patterns in Victoria Land and the Ross Sea can be explained by a transtensional model and are not compatible with large-magnitude crustal stretching within the West Antarctic rift system in the Cenozoic. The crustal thinning across the rift system more likely took place in the Mesozoic, when major West Antarctic crustal block motions occurred. The Cenozoic intracontinental deformation can be related to plate interaction resulting from the global Eocene plate reorganization, prior to the final separation between Antarctica and a narrow salient of the southeastern Australian margin. Displacement magnitude was probably minor, and thus early Tertiary east-west Antarctic motion is unlikely to account for discrepancies in global plate motion circuits.

  20. Possible Effects on the Stability of the West Antarctic Ice Sheet (WAIS) and Associated Sea-level Rise From Active-Recent Subglacial Volcanism Interpreted from Aeromagnetic and Radar Ice-sounding Observations

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.

    2009-12-01

    Aeromagnetic profiles (>10,000 km) acquired in the early 1960s over the West Antarctic Ice Sheet (WAIS) combined with coincident aeromagnetic and radar ice sounding in 1978-79 indicated numerous high-amplitude, shallow-source, magnetic anomalies over a very extensive area of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. These early aerogeophysical surveys defined this area as >500,000 km2. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice. Behrendt et al, (2005, 2008) interpreted these anomalies as indicating >1000 "volcanic centers". requiring high remanent normal (and at least 10% reversed) magnetizations in the present field direction. These data have shown that >80% of the anomaly sources at the bed of the WAIS, have been modified by the moving ice into which they were injected, requiring a younger age than the WAIS (about 25 Ma). Behrendt et al., (1994; 2007) conservatively estimated >1 x 106 km3 volume of volcanic sources to account for the area of the "volcanic center" anomalies. Although exposed volcanoes surrounding the WAIS extend in age to ~34 m.y., Mt Erebus, (<1 Ma) Mt. Melbourne, (<0.26 Ma), and Mt. Takahae (<0.1 Ma) are examples of exposed active volcanoes in the WAIS area. However, the great volume of volcanic centers is buried beneath the WAIS. If only a very small percentage of these >1000 volcanic, magnetic-anomaly sources are active today, or in the recent past, in the drainage area of the WAIS, subglacial volcanism may still have a significant effect on the dynamics of the WAIS. Interpreted active subglacial volcanism is revealed by aerogeophysical data reported by Blankenship et al., (1993, Mt. Casertz), and Corr and Vaughan

  1. Patterns of Volcanism Associated With Oligocene to Recent Dome Uplift, West Antarctic Rift System

    NASA Astrophysics Data System (ADS)

    Le Masurier, W. E.

    2005-12-01

    The Marie Byrd Land dome lies on the Pacific coast of the West Antarctic rift system. It is a structural dome defined by elevations of a low-relief erosion surface that is exposed in fault- block nunataks. The dome has roughly 3000 m of structural relief and is about 800 km in diameter.The growth of the dome has been closely associated with two rather unusual patterns of volcanic activity that provide keys to the timing and rate of uplift. (1) The ages of basaltic rocks that rest on the erosion surface become systematically older with increasing elevation of the surface, e.g. 6.27 Ma at 600 m elevation, 27 Ma at 2700 m, etc., suggesting that uplift began around 27 Ma and continued to 6 Ma at roughly 100m/m.y. (2) The oldest of 18 felsic shield volcanoes formed around 19 Ma at the dome crest. The remaining felsic volcanoes become systematically younger toward the distal flanks of the dome, along linear, fault-controlled, N-S and E-W chains. Late Pleistocene (active) volcanoes lie at the north, south, east, and west margins of the dome, suggesting that uplift proceeded systematically from 19 Ma to the present by centrifugal extension of relict fractures during uplift, accompanied by the rise of felsic magmas from crustal reservoirs. Teleseismic studies (Winberry and Anandakrishnan, 2004) show that the crust has been thinned over the dome crest, and that the dome is supported by low density mantle. Tomographic images near the dome (Sieminski, et al., 2003) show a low velocity column extending down to the transition zone. The Antarctic plate has been stationary at least since the Eocene. In the apparent absence of a mechanism driven by plate tectonics, it is reasonable to infer that mantle plume activity has produced these spatial and temporal patterns of volcanism focused around dome uplift, rather than the more familiar linear volcanic chains associated with moving plates.

  2. Rapid sea-level rise soon from West Antarctic ice sheet collapse?

    SciTech Connect

    Bentley, C.R.

    1997-02-21

    This article presents a commentary on the possibility of a global sea-level rise because of shrinkage of the west antarctic ice sheet (WAIS). The WAIS is the focus of attention because of general agreement among glaciologists that only a marine ice sheet is likely to undergo rapid change, and WAIS appears to be the most vulnerable. 14 refs., 1 fig.

  3. Quantitative West Antarctic Ice Sheet History of The Last 10 Ma

    NASA Astrophysics Data System (ADS)

    Moerz, T.; Hay, W. W.; Camerlenghi, A.; Brueckmann, W.

    settling modified by bottom-current activity. Using a special referenced moving window counting routine the population 1 data has been transformed into a regional Antarctic Peninsula ice volume indicator curve that shows good agreement for the past 10 Ma with the global Lear et al., 2000 ice-volume data. Grain size, opal content and other core parameters prove that the early Pliocene is a time of reduced global and Antarctic ice volume and sea-ice extent. Never before and after the last 10 Ma was palaeo productivity higher at the rise than during this time. This study concludes that during the early Pliocene West Antarctic ice-volume was reduced by 70%. During the late Miocene the ice-sheet was highly dynamic with 1 frequent advances and retreats. The upper Messinian to early late Pliocene was a time of repeated ice-sheet collapses. Starting at 3.2 Ma the ice-sheet became a permanent feature, occupying the shelf during most of the glacial half cycles. 2

  4. Impact of model resolution for on-shelf heat transport along the West Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Graham, Jennifer A.; Dinniman, Michael S.; Klinck, John M.

    2016-10-01

    The flux of warm deep water onto Antarctic continental shelves plays a vital role in determining water mass properties adjacent to the continent. A regional model, with two different grid resolutions, has been used to simulate ocean processes along the West Antarctic Peninsula. At both 4 km and 1.5 km resolution, the model reproduces the locations of warm intrusions, as shown through comparison with observations from instrumented seals. However, the 1.5 km simulation shows greater on-shelf heat transport, leading to improved representation of heat content on the shelf. This increased heat transport is associated with increased eddy activity, both at the shelf-break and in the deep ocean off-shore. Cross-shelf troughs are key locations of on-shelf heat transport. Comparison of two troughs, Belgica and Marguerite, shows differing responses to increased resolution. At higher resolution, there is an increased on-shelf volume transport at Belgica Trough, but not at Marguerite Trough. This is likely related to the differing structure of the shelf-break jet between these two locations. The increased heat flux at Marguerite Trough is attributed to increased heat content in the on-shelf transport. Increased eddy activity off-shelf may lead to greater cross-front heat transport, and therefore increased heat available above the continental slope. While these simulations differ in their magnitude of heat transport, both show similar patterns of variability. Variations in wind stress lead to variations in speed of the shelf-break jet, and therefore on-shelf heat transport. These results demonstrate the importance of model resolution for understanding cross-shelf transport around Antarctica.

  5. Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet.

    PubMed

    Schroeder, Dustin M; Blankenship, Donald D; Young, Duncan A; Quartini, Enrica

    2014-06-24

    Heterogeneous hydrologic, lithologic, and geologic basal boundary conditions can exert strong control on the evolution, stability, and sea level contribution of marine ice sheets. Geothermal flux is one of the most dynamically critical ice sheet boundary conditions but is extremely difficult to constrain at the scale required to understand and predict the behavior of rapidly changing glaciers. This lack of observational constraint on geothermal flux is particularly problematic for the glacier catchments of the West Antarctic Ice Sheet within the low topography of the West Antarctic Rift System where geothermal fluxes are expected to be high, heterogeneous, and possibly transient. We use airborne radar sounding data with a subglacial water routing model to estimate the distribution of basal melting and geothermal flux beneath Thwaites Glacier, West Antarctica. We show that the Thwaites Glacier catchment has a minimum average geothermal flux of ∼ 114 ± 10 mW/m(2) with areas of high flux exceeding 200 mW/m(2) consistent with hypothesized rift-associated magmatic migration and volcanism. These areas of highest geothermal flux include the westernmost tributary of Thwaites Glacier adjacent to the subaerial Mount Takahe volcano and the upper reaches of the central tributary near the West Antarctic Ice Sheet Divide ice core drilling site.

  6. Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet

    PubMed Central

    Schroeder, Dustin M.; Blankenship, Donald D.; Young, Duncan A.; Quartini, Enrica

    2014-01-01

    Heterogeneous hydrologic, lithologic, and geologic basal boundary conditions can exert strong control on the evolution, stability, and sea level contribution of marine ice sheets. Geothermal flux is one of the most dynamically critical ice sheet boundary conditions but is extremely difficult to constrain at the scale required to understand and predict the behavior of rapidly changing glaciers. This lack of observational constraint on geothermal flux is particularly problematic for the glacier catchments of the West Antarctic Ice Sheet within the low topography of the West Antarctic Rift System where geothermal fluxes are expected to be high, heterogeneous, and possibly transient. We use airborne radar sounding data with a subglacial water routing model to estimate the distribution of basal melting and geothermal flux beneath Thwaites Glacier, West Antarctica. We show that the Thwaites Glacier catchment has a minimum average geothermal flux of ∼114 ± 10 mW/m2 with areas of high flux exceeding 200 mW/m2 consistent with hypothesized rift-associated magmatic migration and volcanism. These areas of highest geothermal flux include the westernmost tributary of Thwaites Glacier adjacent to the subaerial Mount Takahe volcano and the upper reaches of the central tributary near the West Antarctic Ice Sheet Divide ice core drilling site. PMID:24927578

  7. From IGY to IPY: Volcanism Associated With the West Antarctic Rift System Interpreted From Geophysical Observations, and Possible Effects on the Stability of the West Antarctic Ice Sheet (WAIS).

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.

    2008-12-01

    Observations from a few oversnow and airborne magnetic profiles acquired over the West Antarctic Ice Sheet (WAIS) during the International Geophysical Year (1957-58) indicated numerous high amplitude, shallow source, magnetic anomalies over a very extensive area of the presently known West Antarctic rift system. Aeromagnetic surveys over the WAIS in the early 1960s and later combined with radar ice sounding in 1978- 79 defined an area >500,000 km2; these anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick moving ice. Behrendt et al, (1962, 1964, 1994, and 2005) and Jankowski et al. (1983) interpreted these anomalies as indicating "volcanic centers." Detailed aeromagnetic and radar ice sounding surveys since 1993 have shown that >80% of these anomaly sources have been modified by the moving ice into which they were injected requiring a younger age than the WAIS (~25 Ma). Behrendt et al., (1994; 2007) conservatively estimated >1 x 106 km3 volume of volcanic sources to account for the area of the "volcanic center" anomalies and suggested the presence of a large igneous province (LIP) if this volume was intruded within a time interval of 1-10 Ma. Active volcanism at a few widely spaced exposures of alkaline volcanic rocks associated with the West Antarctic rift, which extend in age to ~34 Ma in the WAIS area, and interpreted active subglacial volcanism revealed by aerogeophysical data (Blankenship et al., 1993; and Corr and Vaughan, 2008) have raised the question of possible volcanic effects on the regime of the WAIS. Vogel and Tulaczyk (2006) argued that subglacial volcanism may play a "crucial roll" in WAIS stability, but LeMasurier (2008) has discounted this as unlikely. In my presentation I will review the geophysical evidence acquired from the IGY to the IPY, and conclude that whether unlikely or not, future effects on the stability of the WAIS should not be ignored.

  8. The aeromagnetic method as a tool to identify Cenozoic magmatism in the West Antarctic Rift System beneath the West Antarctic Ice Sheet: a review; Thiel subglacial volcano as possible source of the ash layer in the WAISCOR

    USGS Publications Warehouse

    Behrendt, John C.

    2013-01-01

    The West Antarctic Ice Sheet (WAIS) flows through the volcanically active West Antarctic Rift System (WARS). The aeromagnetic method has been the most useful geophysical tool for identification of subglacial volcanic rocks, since 1959–64 surveys, particularly combined with 1978 radar ice-sounding. The unique 1991–97 Central West Antarctica (CWA) aerogeophysical survey covering 354,000 km2 over the WAIS, (5-km line-spaced, orthogonal lines of aeromagnetic, radar ice-sounding, and aerogravity measurements), still provides invaluable information on subglacial volcanic rocks, particularly combined with the older aeromagnetic profiles. These data indicate numerous 100–>1000 nT, 5–50-km width, shallow-source, magnetic anomalies over an area greater than 1.2 × 106 km2, mostly from subglacial volcanic sources. I interpreted the CWA anomalies as defining about 1000 “volcanic centers” requiring high remanent normal magnetizations in the present field direction. About 400 anomaly sources correlate with bed topography. At least 80% of these sources have less than 200 m relief at the WAIS bed. They appear modified by moving ice, requiring a younger age than the WAIS (about 25 Ma). Exposed volcanoes in the WARS are The present rapid changes resulting from global warming, could be accelerated by subglacial volcanism.

  9. Halogenating activities detected in Antarctic macroalgae

    SciTech Connect

    Laturnus, F.; Adams, F.C.; Gomez, I.; Mehrtens, G.

    1997-03-01

    Halogenating activities were determined in samples of 18 cultivated species of brown, red and green macroalgae from the Antarctic. Activities for the halogenating organic compounds with bromide, iodide and chloride were found. Investigated red algae (rhodophytes) showed higher brominating and iodinating activities compared to brown (phaeophytes) and green (chlorophytes) algae. The highest brominating and iodinating activities were measured in the red algae Plocamium cartilagineum (1.11 {+-} 0.01 U g{sup -1} wet algal weight and 0.18 U g{sup -1} wet algal weight, respectively) and Myriogramme mangini (3.62 {+-} 0.17 U g{sup -1} wet algal weight and 4.5 U g{sup -1} wet algal weight, respectively). Chlorinating activities were detected in the red alga Plocamium cartilagineum only (0.086 U g{sup -1} wet algal weight). 30 refs., 2 figs., 1 tab.

  10. The Importance of History for Predicting the Future of the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Bindschadler, R.

    2008-12-01

    The West Antarctic Ice Sheet (WAIS) initiative began in 1990, following on earlier studies of the 'Siple Coast' ice streams and the Ross Ice Shelf. The past nearly two decades of field and satellite research of the West Antarctic ice sheet have produced an astounding number of discoveries, not the least of which is the variability of the West Antarctic ice sheet on time scales from seconds (yes, seconds!) to many millennia. The shorter-time-scale variations, such as the recent acceleration and thinning of glaciers draining into the Amundsen Sea, have illustrated serious weaknesses in what were once regarded as excellent models of ice sheet dynamics. Repairing this modeling capability requires understanding and incorporating external and internal processes previously regarded as less important. Ice-sheet history remains the best means to test, tune and validate numerical models of ice sheets. Cenozoic-age behavior may seem too ancient to matter to a centennial-time-scale focus on the future, but it is precisely through a long history, that the variety of more extreme ice sheet configurations can be extracted. Such upper or lower bound estimates have served the WAIS community well over the years to help justify research needed to assess the probability of dramatic behavior. Now, with the necessity of model revisions central to the WAIS effort, time histories of ice sheet behavior over both short and long time scales will return to a position of extreme importance.

  11. Negative magnetic anomaly over Mt. Resnik, a subaerially erupted volcanic peak beneath the West Antarctic Ice Sheet

    USGS Publications Warehouse

    Behrendt, John C.; Finn, C.; Morse, D.L.; Blankenship, D.D.

    2006-01-01

    negative anomalies indicate volcanic activity during a period of magnetic reversal and therefore must also be at least 780 ka. The spatial extent and volume of volcanism can now be reassessed for the 1.2 ?? 106 km2 region of the WAIS characterized by magnetic anomalies defining interpreted volcanic centers associated with the West Antarctic rift system. The CWA covers an area of 3.54 ?? 105 km2; forty-four percent of that area exhibits short-wavelength, high-amplitude anomalies indicative of volcanic centers and subvolcanic intrusions. This equates to an area of 0.51 ?? 105 km2 and a volume of 106 km3 beneath the ice-covered West Antarctic rift system, of sufficient extent to be classified as a large igneous province interpreted to be of Oligocene to recent age.

  12. Where might we find evidence of a Last Interglacial West Antarctic Ice Sheet collapse in Antarctic ice core records?

    NASA Astrophysics Data System (ADS)

    Bradley, S. L.; Siddall, M.; Milne, G. A.; Masson-Delmotte, V.; Wolff, E.

    2012-05-01

    Abundant indirect evidence suggests that the West Antarctic Ice Sheet (WAIS) reduced in size during the Last Interglacial (LIG) compared to the Holocene. This study explores this possibility by comparing, for the first time, ice core stable isotope records for the LIG with output from a glacio-isostatic adjustment (GIA) model. The results show that ice core records from East Antarctica are remarkably insensitive to vertical movement of the solid land motion driven by a simulated hypothetical collapse of the WAIS. However, new and so far unexplored sites are identified which are sensitive to the isostatic signal associated with WAIS collapse and so ice core proxy data from these sites would be effective in testing this hypothesis further.

  13. Tectonics of the Antarctic-Scotia plate boundary near Elephant and Clarence Islands, West Antarctica

    NASA Astrophysics Data System (ADS)

    Klepeis, Keith A.; Lawver, Lawrence A.

    1996-09-01

    Over 5000 km of new bathymetric data collected from near the northern Antarctic Peninsula (60°S-63.5°S latitude, 53.5°W-63°W longitude) show the morphology of an irregular segment of the Antarctic-Scotia plate boundary and nearby Shetland microplate. The irregular plate boundary is formed by an oblique intersection (>70°) of the sinistral transpressional Shackleton fracture zone (SFZ) and the sinistral transtensional South Scotia Ridge transform (SSR) near Elephant (EI) and Clarence (CI) Islands. Mapped boundaries of the Shetland microplate include the South Shetland Trench and the volcanic rift axis of Bransfield Strait marginal basin. Bathymetric data, single-channel seismic reflection profiles, and Geosat/ERS 1 free air gravity data show a southeast trending fault zone on the northeast side of a prominent ridge in the SFZ. The fault zone is defined by scarps that affect ocean floor sediments, fault-bounded subbasins, rotated sedimentary layers, angular unconformities, linear gravity trends, and transtensional followed by contractional deformation. Southeast of a termination of the SFZ ridge at the South Shetland Trench, the fault zone subdivides into segments displaying steep scarps (up to 23°) and canyons on the northeast margin of the EI platform. These features become east-west trending nearer to the western SSR. South of the islands, southwest trending extensional or transtensional fault zones disrupt the Bransfield Strait volcanic rift axis. These data suggest that (1) recent (<4 Ma) changes in the configuration of the Antarctic plate near the Antarctic Peninsula caused a segment of the SFZ transform to adjust to a more stable, rectilinear geometry with the SSR transform, and (2) diffuse transtension resulting from current Antarctic-Scotia relative motion is dissecting the Shetland microplate near EI and CI and transferring slivers of the Scotia plate onto the Antarctic plate.

  14. The aeromagnetic method as a tool to identify Cenozoic magmatism in the West Antarctic Rift System beneath the West Antarctic Ice Sheet — A review; Thiel subglacial volcano as possible source of the ash layer in the WAISCORE

    NASA Astrophysics Data System (ADS)

    Behrendt, John C.

    2013-02-01

    The West Antarctic Ice Sheet (WAIS) flows through the volcanically active West Antarctic Rift System (WARS). The aeromagnetic method has been the most useful geophysical tool for identification of subglacial volcanic rocks, since 1959-64 surveys, particularly combined with 1978 radar ice-sounding. The unique 1991-97 Central West Antarctica (CWA) aerogeophysical survey covering 354,000 km2 over the WAIS, (5-km line-spaced, orthogonal lines of aeromagnetic, radar ice-sounding, and aerogravity measurements), still provides invaluable information on subglacial volcanic rocks, particularly combined with the older aeromagnetic profiles. These data indicate numerous 100->1000 nT, 5-50-km width, shallow-source, magnetic anomalies over an area greater than 1.2 × 106 km2, mostly from subglacial volcanic sources. I interpreted the CWA anomalies as defining about 1000 "volcanic centers" requiring high remanent normal magnetizations in the present field direction. About 400 anomaly sources correlate with bed topography. At least 80% of these sources have less than 200 m relief at the WAIS bed. They appear modified by moving ice, requiring a younger age than the WAIS (about 25 Ma). Exposed volcanoes in the WARS are < 34 Ma, but at least four are active. If a few buried volcanic centers are active, subglacial volcanism may well affect the WAIS regime. Aerogeophysical data (Blankenship et al., 1993, Mt. Casertz; Corr and Vaughan, 2008, near Hudson Mts.) indicated active subglacial volcanism. Magnetic data indicate a caldera and a surrounding "low" in the WAISCORE vicinity possibly the result of a shallow Curie isotherm. High heat flow reported from temperature logging in the WAISCORE (Conway et al., 2011; Clow, personal commun.) and a volcanic ash layer (Dunbar, 2012) are consistent with this interpretation. A subaerially erupted subglacial volcano, (Mt Thiel), about 100 km distant, may be the ash source. The present rapid changes resulting from global warming, could be

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  16. The diatom record from beneath the West Antarctic Ice Sheet and the global proxy perspective

    NASA Technical Reports Server (NTRS)

    Scherer, Reed P.

    1993-01-01

    Recent glaciological evaluation and modeling of the marine-based West Antarctic Ice Sheet (WAIS) support the possibility that the WAIS disintegrated during one or more Pleistocene interglacial period(s). The magnitude of sea level and oxygen isotope variation during certain late-Pleistocene interglacial periods is also consistent with the possibility of major retreat of the WAIS. Although oxygen isotopes from deep-sea sediments provide the best available proxy record for global ice volume (despite the ambiguities in the record), the source of ice volume changes must be hypothesized. Based on the intensity of interglacial isotopic shifts recorded in Southern Ocean marine sedimentary records, stage 11 (400,000 years ago) is the strongest candidate for WAIS collapse, but the records for stages 9, 7, and 5.5 are all consistent with the possibility of multiple late-Pleistocene collapses. Seismic reflection studies through the WAIS have revealed thick successions of strata with seismic characteristics comparable to upper Tertiary marine sediments. Small samples of glacial diamictons from beneath the ice sheet have been collected via hot-water drilled access holes. These sediments include mixed diatom assemblages of varying ages. Late-Miocene diatoms dominate many samples, probably reflecting marine deposition in West Antarctic basins prior to development of a dominantly glacial phase in West Antarctica. In addition to late-Miocene diatoms, samples from Upstream B (1988/89) contain rare post-Miocene diatoms, many of which imply deposition in the West Antarctic interior during one or more Pleistocene deglaciation periods. Age-diagnostic fossils in glacial sediments beneath ice sheets provide relatively coarse chronostratigraphic control, but they do contain direct evidence of regional deglaciation. Thus, sub-glacial till samples provide the evidence regarding the source of ice sheet variability seen in well-dated proxy records. Combined, these independent data sets can

  17. The impacts of local human activities on the Antarctic environment

    NASA Astrophysics Data System (ADS)

    Tin, T.; Fleming, Z. L.; Hughes, K. A.; Ainley, D. G.; Convey, P.; Moreno, C. A.; Pfeiffer, S.; Scott, J.; Snape, I.

    2009-04-01

    An overview of a recently published review of the scientific literature from the past decade on the impacts of human activities on the Antarctic environment is presented. An assessment of the cumulative effects of scientists and accompanying base construction, tourists and fishery activities in Antarctica is timely given a decade since the Protocol on Environmental Protection to the Antarctic Treaty came into force in 1998 and the increasing attention given to and human presence in Antarctica during this 2007-2009 IPY. A range of impacts has been identified at a variety of spatial and temporal scales. Chemical contamination and sewage disposal on the continent have been found to be long-lived, with contemporary sewage management practices at many coastal stations insufficient to prevent local contamination. Human activities, particularly construction and transport, have affected Antarctic flora and fauna and a small number of non-indigenous plant and animal species has become established on some of the Antarctic Peninsula and sub Antarctic islands. There is little indication of recovery of overexploited fish stocks, and ramifications of fishing activity on bycatch species and the ecosystem could also be far-reaching. The Antarctic Treaty System and its instruments, in particular the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the Environmental Protocol, provide a framework within which management of human activities take place. In order to ensure comprehensive protection of the Antarctic environment, including its intrinsic, wilderness and scientific values in the face of the continuing expansion of human activities in Antarctica, a more effective implementation of a wide range of measures is essential. These include effective environmental impact assessments, long-term monitoring, mitigation measures for non-indigenous species, ecosystem-based management of living resources, and increased regulation of National Antarctic

  18. Simultaneous solution for mass trends on the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Schoen, N.; Zammit-Mangion, A.; Rougier, J. C.; Flament, T.; Rémy, F.; Luthcke, S.; Bamber, J. L.

    2015-04-01

    The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last 2 decades for the West Antarctic Ice Sheet (WAIS) but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous error-bounded trend estimate of ice mass loss over the WAIS from 2003 to 2009 which is almost entirely data driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate which can be used to validate and test the models. In addition, spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of -76 ± 15 Gt yr-1 for the WAIS and Antarctic Peninsula, including the major Antarctic islands. The GIA estimate compares well with results obtained from recent forward models (IJ05-R2) and inverse methods (AGE-1). The Bayesian framework is sufficiently flexible that it can, eventually, be used for the whole of Antarctica, be adapted for other ice sheets and utilise data from other sources such as ice cores, accumulation radar data, and other measurements that contain information about any of the processes that are solved for.

  19. Simultaneous solution for mass trends on the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Schön, N.; Zammit-Mangion, A.; Bamber, J. L.; Rougier, J.; Flament, T.; Rémy, F.; Luthcke, S. B.

    2014-06-01

    The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last two decades in the West Antarctic Ice Sheet (WAIS), but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003-2009 which is almost entirely data-driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate, which can be used to validate and test the models. In addition, full spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of -76 ± 15 GT yr-1 for the WAIS and Antarctic Peninsula (AP), including the major Antarctic Islands. The GIA estimate compares very well with results obtained from recent forward models (IJ05-R2) and inversion methods (AGE-1). Due to its computational efficiency, the method is sufficiently scalable to include the whole of Antarctica, can be adapted for other ice sheets and can easily be adapted to assimilate data from other sources such as ice cores, accumulation radar data and other measurements that contain information about any of the processes that are solved for.

  20. Plate convergence west of Patagonia and the Antarctic Peninsula since 61 Ma

    NASA Astrophysics Data System (ADS)

    Eagles, Graeme; Scott, Benjamin G. C.

    2014-12-01

    A new plate kinematic model portrays plate motions immediately west and south of Drake Passage in the southeast Pacific Ocean. Overall intermediate-to-slow rate spreading generated oceanic lithosphere as the Phoenix plate diverged from the Antarctic plate. The model shows a history of Phoenix plate motion that is interpretable as having been affected by a northeast-increasing gradient in the slab pull force since chron 18 (39 Ma), during which time newer, less dense lithosphere was subducting in the southwest than in the northeast. The model allows first calculations of Phoenix-Farallon (Nazca) plate motion parameters in the south Pacific plate circuit. Using these parameters, it is possible to show that the simplest assumptions about the ridge's segmentation, length and migration are consistent with existing suggestions of its location from consideration of slab window-related volcanism at sites in South America around 50 and 20 Ma. The parameters thus define ridge locations that can be used to define which plates were subducting beneath South America and the Magallanes and Antarctic plates, and when. We consider the relationships between the plate convergence rate, obliquity and the history of magmatism on the Antarctic Peninsula and at the North Patagonian batholith, showing that magmatic pulses can be related to accelerations in the plate convergence rate. Between these settings, Phoenix-South American plate motion was almost parallel to the Fuegian trench. Here, magmatism in Paleocene to early Miocene times must be related to the presence of a slab subducted beneath the region by the less oblique collision further north. Later magmatism can be related to migration of the Phoenix-Farallon ridge and Phoenix-Farallon-Antarctic triple junction into the area south of the Fuegian margin, which brought it into slow low-obliquity convergence with first Farallon and then Antarctic plate lithosphere.

  1. Geological and Tectonic Evidence for the Formation and Extensional Collapse of the West Antarctic Plateau: Implications for the Formation of the West Antarctic Rift System and the Transantarctic Mountains

    NASA Astrophysics Data System (ADS)

    Fitzgerald, P. G.; Studinger, M.; Bialas, R. W.; Buck, W.

    2007-12-01

    The Transantarctic Mountains (TAM), the world's longest and highest non-contractional intracontinental mountain belt, define the western boundary of the West Antarctic rift system (WARS). The WARS is a broad region of extended continental lithosphere, ca. 750-1000 km wide, lying dominantly below sea-level. A new model (Bialas et al., 2007), proposes that a region of thickened continental crust and high-standing topography, the "West Antarctic Plateau", underwent extensional collapse to leave a remnant edge representing the proto-TAM. Tectonic and paleogeographic reconstructions indicate the plateau formed inboard of a continental arc along the paleo- Pacific margin of Antarctica, active throughout the Paleozoic until the late Mesozoic. This high-standing region was responsible for confining sediments (Beacon Supergroup) to elongate basins along the length of the TAM. Much of the present region of the WARS has been correlated with the Lachlan Fold belt of southeastern Australia. This belt formed from the Ordovician to Carboniferous during back-arc basin formation associated with slab roll- back with short periods of compression. Convergence along the paleo-Pacific margin, perhaps enhanced by subduction of more buoyant oceanic lithosphere as the Phoenix-Pacific ridge was obliquely subducted, resulted in crustal thickening and formation of high-standing terrain (the plateau). Extensional collapse of the plateau most likely began in the Jurassic during initial rifting between East and West Antarctica, but was mainly accomplished during distributed rifting in the Cretaceous (ca. 105-85) following subduction of the Phoenix-Pacific ridge and prior to the separation of New Zealand from Marie Byrd Land. Continued formation of the TAM continued in the Cenozoic concomitant with extension in the WARS that was localized along its western margin adjacent to the TAM. Glacial erosion in the Oligocene and early-Miocene enhanced peak height in the TAM. In this presentation we

  2. Tectonics of the West Antarctic rift system: new light on the history and dynamics of distributed intracontinental extension

    USGS Publications Warehouse

    Siddoway, C.S.

    2007-01-01

    The West Antarctic rift system (WARS) is the product of multiple stages of intracontinental deformation from Jurassic to Present. The Cretaceous rifting phase accomplished >100 percent extension across the Ross Sea and central West Antarctica, and is widely perceived as a product of pure shear extension orthogonal to the Transantarctic Mountains that led to breakup and opening of the Southern Ocean between West Antarctica and New Zealand. New structural, petrological, and geochronological data from Marie Byrd Land reveal aspects of the kinematics, thermal history, and chronology of the Cretaceous intracontinental extension phase that cannot be readily explained by a single progressive event. Elevated temperatures in "Lachlan-type" crust caused extensive crustal melting and mid-crustal flow within a dextral transcurrent strain environment, leading to rapid extension and locally to exhumation and rapid cooling of a migmatite dome and detachment footwall structures. Peak metamorphism and onset of crustal flow that brought about WARS extension between 105 Ma and 90 Ma is kinematically, temporally, and spatially linked to the active convergent margin system of East Gondwana. West Antarctica-New Zealand breakup is distinguished as a separate event at 83-70 Ma, from the standpoint of kinematics and thermal evolution

  3. Were West Antarctic Ice Sheet grounding events in the Ross Sea a consequence of East Antarctic Ice Sheet expansion during the middle Miocene?

    NASA Astrophysics Data System (ADS)

    Bart, Philip J.

    2003-11-01

    Seismic correlation of glacial unconformities from the Ross Sea outer continental shelf to chronostratigraphic control at DSDP sites 272 and 273 indicates that at least two West Antarctic Ice Sheet (WAIS) expansions occurred during the early part of the middle Miocene (i.e. well before completion of continental-scale expansion of the East Antarctic Ice Sheet (EAIS) inferred from δ 18O and eustatic shifts). Therefore, if the volume of the EAIS was indeed relatively low, and if the Ross Sea age model is valid, then these WAIS expansions/contractions were not a direct consequence of EAIS expansion over the Transantarctic Mountains onto West Antarctica. An in-situ development of the WAIS during the middle Miocene suggests that either West Antarctic land elevations were above sea level and/or that air and water temperatures were sufficiently cold to support a marine-based ice sheet. Additional chronostratigraphic and lithologic data are needed from Antarctic margins to test these speculations.

  4. Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans

    NASA Astrophysics Data System (ADS)

    Payne, Antony J.; Vieli, Andreas; Shepherd, Andrew P.; Wingham, Duncan J.; Rignot, Eric

    2004-12-01

    A growing body of observational data suggests that Pine Island Glacier (PIG) is changing on decadal or shorter timescales. These changes may have far-reaching consequences for the future of the West Antarctic ice sheet (WAIS) and global sea levels because of PIG's role as the ice sheet's primary drainage portal. We test the hypothesis that these changes are triggered by the adjoining ocean. Specifically, we employ an advanced numerical ice-flow model to simulate the effects of perturbations at the grounding line on PIG's dynamics. The speed at which these changes are propagated upstream implies a tight coupling between ice-sheet interior and surrounding ocean.

  5. The first geothermal heat flux measurement below the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Fisher, A. T.; Mankoff, K. D.; Tulaczyk, S. M.; Foley, N.; Hossainzadeh, S.

    2014-12-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow and mass balance of outlet glaciers and ice sheets. We measured directly the geothermal heat flux below the West Antarctic Ice Sheet (WAIS), under Subglacial Lake Whillans (SLW), as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. The one-dimensional, conductive heat flux is the product of thermal gradient and thermal conductivity. We developed and fielded a tool to determine the thermal gradient in lake sediments, after penetrating ~800 m of ice using a hot water drilling system. We used the needle-probe method to measure the thermal conductivity of sediments recovered from the bottom of the lake with a gravity-driven multi-corer. The thermal gradient was determined during two separate deployments of the geothermal tool, which penetrated ~1.1 m into the till below SLW, yielding essentially identical results: 0.21±0.07 °C/m. Fifteen sediment thermal conductivity measurements yield an average value of 1.36±0.12 W/m-K. The heat flux determined from these measurements is 285±85 W/m2. This value is somewhat higher than that estimated from the WAIS-Divide ice core site, 230 mW/m2, ~800 km away, and much higher than regional estimates based on magnetics and a global seismic model, generally ≤100 mW/m2. Elevated heat flux in this area could result from thermal perturbations associated with rifting, crustal thinning, or volcanic activity. Heat flux of this magnitude is likely to cause basal melt rate of a few cm/year. If this value is representative of conditions below this part of the WAIS, it might help to explain the occurrence of active subglacial lakes and fast-moving ice streams and the ice dynamics of WAIS more broadly.

  6. Ocean temperature thresholds for Last Interglacial West Antarctic Ice Sheet collapse

    NASA Astrophysics Data System (ADS)

    Sutter, Johannes; Gierz, Paul; Grosfeld, Klaus; Thoma, Malte; Lohmann, Gerrit

    2016-03-01

    The West Antarctic Ice Sheet (WAIS) is considered the major contributor to global sea level rise in the Last Interglacial (LIG) and potentially in the future. Exposed fossil reef terraces suggest sea levels in excess of 7 m in the last warm era, of which probably not much more than 2 m are considered to originate from melting of the Greenland Ice Sheet. We simulate the evolution of the Antarctic Ice Sheet during the LIG with a 3-D thermomechanical ice sheet model forced by an atmosphere-ocean general circulation model (AOGCM). Our results show that high LIG sea levels cannot be reproduced with the atmosphere-ocean forcing delivered by current AOGCMs. However, when taking reconstructed Southern Ocean temperature anomalies of several degrees, sensitivity studies indicate a Southern Ocean temperature anomaly threshold for total WAIS collapse of 2-3°C, accounting for a sea level rise of 3-4 m during the LIG. Potential future Antarctic Ice Sheet dynamics range from a moderate retreat to a complete collapse, depending on rate and amplitude of warming.

  7. Rifting, Volcanism, and the Geochemical Character of the Mantle Beneath the West Antarctic Rift System (Invited)

    NASA Astrophysics Data System (ADS)

    Mukasa, S. B.; Aviado, K. B.; Rilling-Hall, S.; Bryce, J. G.; Cabato, J.

    2013-12-01

    The West Antarctic Rift System (WARS) is one of the largest extensional alkali volcanic provinces on Earth, but the mechanisms responsible for generating the massive amounts of its associated magmatism remain controversial. The failure of both passive and active decompression melting models to adequately explain the observed lava volumes has prompted debate about the relative roles of thermal plume-related melting and ancient subduction-related flux melting. 40Ar/39Ar dating and geochemical analyses of the lavas, as well as volatile and trace-element determinations of olivine-hosted melt inclusions shed light on the relationship between rifting and volcanism, and also improve our understanding of the geochemical character of the mantle beneath the WARS. Results show that the magmatism post-dates the main phase of extension along the Terror Rift within the WARS, which supports a decompression-melting model without the benefit of a significant thermal anomaly. However, the observed large magma volumes seem to require a volatile-fluxed mantle, a notion supported by a long history of subduction (>500 Myr) along the paleo-Pacific margin of Gondwana. In fact, the legacy of that subduction may manifest itself in the high H2O concentrations of olivine-hosted melt inclusions (up to 3 wt% in preliminary results from ion probe measurements). The major oxide compositions of lavas in the WARS are best matched to experimental melts of garnet pyroxenite and carbonated peridotite sources. The Pb and Nd isotopic systems are decoupled from each other, suggesting removal of fluid-mobile elements from the mantle source possibly during the long history of subduction along this Gondwana margin. Extremely unradiogenic 187Os/188Os ranging to as low as 0.1081 × 0.0001 hints at the involvement of lithospheric components in generation of magmas in the WARS.

  8. Nature of the Mantle Sources and Bearing on Tectonic Evolution in the West Antarctic Rift System

    NASA Astrophysics Data System (ADS)

    Mukasa, S. B.; Rilling-Hall, S.; Marcano, M. C.; Wilson, T. J.; Lawver, L. A.; LeMasurier, W. E.

    2012-12-01

    We collected samples from subaerial lava flows and dredged some Neogene basanitic lavas from seven volcanic edifices in the Ross Sea, Antarctica - a part of the West Antarctic Rift System (WARS) and one of the world's largest alkaline magmatic provinces - for a study aimed at two principal objectives: (1) Geochemical interrogation of the most primitive magmatic rocks to try and understand the nature of the seismically abnormal mantle domain recently identified beneath the shoulder of the Transantarctic Mountains (TAM), the Ross Sea Embayment and Marie Byrd Land; and (2) Using 40Ar/39Ar geochronology to establish a temporal link between magmatism and tectonism, particularly in the Terror Rift. We have attempted to answer the questions of whether magmatism is due to a hot mantle or wet mantle, and whether rifting in the area triggered magmatic activity or vice versa. Results show that the area does not have an age-progressive hotspot track, and the magmatism post-dates the main phase of extension along the Terror Rift within the WARS, which supports a decompression-melting model without the benefit of a significant thermal anomaly. In fact, preliminary volatile measurements on olivine-hosted melt inclusions have yielded water concentrations in excess of 2 wt%, indicating that flux melting was an important complementary process to decompression melting. The major oxide compositions of lavas in the WARS are best matched to experimental melts of carbonated peridotite, though garnet pyroxenite can also be a minor source. The Pb and Nd isotopic systems are decoupled from each other, suggesting removal of fluid-mobile elements from the mantle source possibly during the long history of subduction along the Paleo-Pacific margin of Gondwana. Extremely unradiogenic 187Os/188Os ranging to as low as 0.1081 ± 0.0001 hints at the involvement of lithospheric components in generation of magmas in the WARS.

  9. West-Antarctic Ice Streams: Analog to Ice Flow in Channels on Mars

    NASA Technical Reports Server (NTRS)

    Lucchitta, B. K.

    1997-01-01

    Sounding of the sea floor in front of the Ross Ice Shelf in Antarctica recently revealed large persistent patterns of longitudinal megaflutes and drumlinoid forms, which are interpreted to have formed at the base of ice streams during the list glacial advance. The flutes bear remarkable resemblance to longitudinal grooves and highly elongated streamlined islands found on the floors of some large martian channels, called outflow channels. ln addition, other similarities exist between Antarctic ice streams and outflow channels. Ice streams are 30 to 80 km wide and hundreds of kilometers long, as are the martian channels. Ice stream beds are below sea level. Floors of many martian outflow channels lie below martian datum, which may have been close to or below past martian sea levels. The Antarctic ice stream bed gradient is flat and locally may go uphill, and surface slopes are exceptionally low. So are gradients of martian channels. The depth to the bed in ice streams is 1 to 1.5 km. At bankful stage, the depth of the fluid in outflow channels would have been 1 to 2 km. These similarities suggest that the martian outflow channels, whose origin is commonly attributed to gigantic catastrophic floods, were locally filled by ice that left a conspicuous morphologic imprint. Unlike the West-Antarctic-ice streams, which discharge ice from an ice sheet, ice in the martian channels came from water erupting from the ground. In the cold martian environment, this water, if of moderate volume, would eventually freeze. Thus it may have formed icings on springs, ice dams and jams on constrictions in the channel path, or frozen pools. Given sufficient thickness and downhill surface gradient, these ice masses would have moved; and given the right conditions, they could have moved like Antarctic ice streams.

  10. Will A Warmer West Antarctic Also Bring A Wetter Ice Sheet?

    NASA Astrophysics Data System (ADS)

    Reusch, D. B.; Karmosky, C. C.; Lampkin, D. J.; Schneider, D. P.

    2013-12-01

    CMIP5 GCMs generally agree that West Antarctica will not be exempted from the broader global trend of increasing future surface temperatures. We examine how an important climatic/geophysical parameter, surface melt occurrence, may be affected by related changes in regional meteorological forcings. We use the forecast model Polar WRF (PWRF) to develop relatively detailed (15 km) and computationally consistent meteorological data from diverse, lower-resolution global datasets (e.g., ERA Interim, CCSM4) for recent and future time slices. Contemporary (1987-2008) surface melting is assessed using satellite-based observations and standard tools for evaluating spatial and temporal variability. Synoptic drivers of melt are evaluated using ERA Interim-based PWRF with self-organizing maps (SOMs) to identify spatial patterns in variables associated with melt, e.g., temperature, winds and surface energy balance components. CMIP5 GCMs that have skill versus Antarctic observations are used with PWRF to develop contemporary (1990-1999) and future (e.g., 2091-2100) datasets. The former are further tested using climatologies (traditional and SOM-based) that are compared with results from ERA Interim-based PWRF. This examines how well the GCM-based dataset reproduces both average climate and its variability. It also explores how surface melt-related conditions in the GCM may differ from those identifed in ERA Interim. Skill tests versus warm season observations identified CCSM4, MRI-CGCM3 and GFDL-ESM2M as the 'best' Antarctic GCMs for the 1990s. CCSM4 January surface temperature compares very well with ERA Interim results in both the original and PWRF-driven datasets: bias is generally within ×2 °C over the continent. MRI-CGCM3 is notably warmer especially over areas of interest such as the Ross Ice Shelf (8-10 °C). Using the RCP 8.5 emissions scenario, CCSM4-driven PWRF shows continent-wide warming at mid-century (2050-2059), with the East Antarctic plateau reaching 5

  11. Glacial removal of late Cenozoic subglacially emplaced volcanic edifices by the West Antarctic ice sheet

    USGS Publications Warehouse

    Behrendt, John C.; Blankenship, D.D.; Damaske, D.; Cooper, A. K.

    1995-01-01

    Local maxima of the horizontal gradient of pseudogravity from closely spaced aeromagnetic surveys over the Ross Sea, northwestern Ross Ice Shelf, and the West Antarctic ice sheet, reveal a linear magnetic rift fabric and numerous subcircular, high-amplitude anomalies. Geophysical data indicate two or three youthful volcanic edifices at widely separated areas beneath the sea and ice cover in the West Antarctic rift system. In contrast, we suggest glacial removal of edifices of volcanic sources of many more anomalies. Magnetic models, controlled by marine seismic reflection and radar ice-sounding data, allow us to infer that glacial removal of the associated late Cenozoic volcanic edifices (probably debris, comprising pillow breccias, and hyaloclastites) has occurred essentially concomitantly with their subglacial eruption. "Removal' of unconsolidated volcanic debris erupted beneath the ice is probably a more appropriate term than "erosion', given its fragmented, ice-contact origin. The exposed volcanoes may have been protected from erosion by the surrounding ice sheet because of more competent rock or high elevation above the ice sheet. -from Authors

  12. Inability of stratospheric sulfate aerosol injections to preserve the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    McCusker, K. E.; Battisti, D. S.; Bitz, C. M.

    2015-06-01

    Injection of sulfate aerosols into the stratosphere has the potential to reduce the climate impacts of global warming, including sea level rise (SLR). However, changes in atmospheric and oceanic circulation that can significantly influence the rate of basal melting of Antarctic marine ice shelves and the associated SLR have not previously been considered. Here we use a fully coupled global climate model to investigate whether rapidly increasing stratospheric sulfate aerosol concentrations after a period of global warming could preserve Antarctic ice sheets by cooling subsurface ocean temperatures. We contrast this climate engineering method with an alternative strategy in which all greenhouse gases (GHG) are returned to preindustrial levels. We find that the rapid addition of a stratospheric aerosol layer does not effectively counteract surface and upper level atmospheric circulation changes caused by increasing GHGs, resulting in continued upwelling of warm water in proximity of ice shelves, especially in the vicinity of the already unstable Pine Island Glacier in West Antarctica. By contrast, removal of GHGs restores the circulation, yielding relatively cooler subsurface ocean temperatures to better preserve West Antarctica.

  13. Modelling West Antarctic ice sheet growth and collapse through the past five million years.

    PubMed

    Pollard, David; DeConto, Robert M

    2009-03-19

    The West Antarctic ice sheet (WAIS), with ice volume equivalent to approximately 5 m of sea level, has long been considered capable of past and future catastrophic collapse. Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat. Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms. Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around approximately 15 kyr ago before retreating to near-modern locations by approximately 3 kyr ago. Prior collapses during the warmth of the early Pliocene epoch and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments. Until now, however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea, indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at

  14. Question of Ages of Cenozoic Volcanic Centers Inferred Beneath the West Antarctic Ice Sheet (WAIS) in the West Antarctic Rift System (WR) from Coincident Aeromagnetic and Radar Ice Sounding Surveys

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.; Finn, C. A.; Blankenship, D. D.

    2007-12-01

    The recently acquired radar ice sounding surveys (Holt, et al., 2006) extending the 1990s Central West Antarctica (CWA) aerogeophysical survey to the Amundsen and Bellingshausen sea coasts allows us to revise a thought experiment reported by Behrendt et al., 1991 from very limited bed elevation data. Were the ice of the WAIS flowing through the WR to be compressed to the density of crustal rock, almost all of the area beneath the WAIS would be at or above sea level, much >1 km elevation. There are only about 10-20% of the very deep areas (such as the Bentley subglacial trench and the Byrd Subglacial Basin) filled with 3-4-km thick ice that would be well below sea level. The age of the 5-7-km high rift shoulder bounding the asymmetric WR from northern Victoria Land through the Horlick Mountains (where it diverges from the Transantarctic Mountains) to the Ellsworth Mountains has been reported as old as Cretaceous. Volcanic exposures associated with the West Antarctic rift system in the present WAIS area extend at least to 34 Ma and the West Antarctic ice sheet has flowed through the rift possibly as far back in time as 25 Ma. Active volcanism has been reported for the WR at only a few widely scattered locations, so speculations about present volcanic activity beneath the WAIS are quite uncertain, and it is probably quite rare. The Central West Antarctic aeromagnetic and radar ice sounding survey carried out in the 1990s revealed about 1000 "volcanic centers" characterized by 100-1000 nT shallow source magnetic anomalies, at least 400 of which have associated bed topography. About 80% of these show relief <200 m and have been interpreted as smoothed off as they were erupted (injected) into the moving WAIS. Several kilometer-thick highly magnetic sources are required to fit these anomalies requiring high remanent magnetizations in the present field direction. We interpreted these sources as subvolcanic intrusions which must be younger than about 100 Ma because the

  15. Feedback between magmatic, tectonic and glacial processes in the West Antarctic Rift System (Invited)

    NASA Astrophysics Data System (ADS)

    Rocchi, S.

    2010-12-01

    The western Ross Sea coast of the West Antarctic rift system (WARS) is littered with mid-Eocene to Present alkaline plutons, dike swarms and volcanoes. The mafic igneous products have OIB-HIMU signature, similar to basalts associated with long-lived hotspot tracks, pointing to the possible occurrence of one or more mantle plumes active during the Cenozoic or the Mesozoic. However, He and Pb isotope data suggest alternative views, with a rather shallow magma source not involving deep, undegassed mantle, and affected by a metasomatic episode as young as hundred(s) of million years, an order of magnitude less than typically invoked for mantle plume sources. A shallow rift-driving mechanism is supported also by the geometric relationships between magma emplacement and regional rift-related fault systems. Further, these faults were active coeval with magma emplacement, as demonstrated by the age of a fault-generated pseudotachylyte (34 Ma) and by apatite fission track thermochronology. In a wider perspective, these faults are in striking continuity with Southern Ocean fracture zones, and mantle tomography depicts a low-velocity anomaly of linear (not circular) shape overlapping the belt of these fracture zones. The lack of firm evidence for plume activity is thus at odds with a clear link between large-scale tectonic features and magma emplacement, supporting this three-stage model. (1) The WARS Late Cretaceous amagmatic extension led to metasomatism of the sublithospheric mantle, later rheologically incorporated into the lithosphere. (2) During Eocene-Oligocene times, craton-ward mantle flow under the thinned WARS heated up the mantle at the edge of the Antarctic lithosphere. In mid Eocene, the differential velocity across Southern Ocean fracture zones reactivated Paleozoic translithospheric discontinuities in northern Victoria Land as intraplate dextral strike-slip fault systems, promoting local mantle decompression melting and rise of magmas in plutons and dike

  16. Modelling the Isotopic Response to West Antarctic Ice Sheet Collapse and Sea Ice Retreat During the Last Interglacial

    NASA Astrophysics Data System (ADS)

    Holloway, M. D.

    2015-12-01

    Ice sheet changes can exert major control over spatial water isotope variations in Antarctic surface snow. Consequently a significant mass loss or gain of the West Antarctic Ice Sheet (WAIS) would be expected to cause changes in the water isotope record across Antarctic ice core sites. Analysis of sea level indicators for the last interglacial (LIG; 130,000 to 115,000 years ago) suggest a global sea level peak 6 to 9 m higher than present. Recent NEEM Greenland ice core results imply that Greenland likely provided a modest 2m contribution towards this global sea level rise. This implies that a WAIS contribution is necessary to explain the LIG sea level maxima. In addition, Antarctic ice core records suggest that Antarctic air temperatures during the LIG were up to 6 °C warmer than present. Climate models have been unable to recreate such warmth when only orbital and greenhouse gas forcing are considered. Thus changes to the Antarctic ice sheet and ocean circulation may be required to reconcile model simulations with ice core data. Here we model the isotopic response to differing WAIS deglaciation scenarios, freshwater hosing, and sea ice configurations using a fully coupled General Circulation Model (GCM) to help interpret Antarctic ice core records over the LIG.

  17. Melt generation in the West Antarctic Rift System: the volatile legacy of Gondwana subduction?

    NASA Astrophysics Data System (ADS)

    Aviado, K.; Rilling-Hall, S.; Mukasa, S. B.; Bryce, J. G.; Cabato, J.

    2013-12-01

    The West Antarctic Rift System (WARS) represents one of the largest extensional alkali volcanic provinces on Earth, yet the mechanisms responsible for driving rift-related magmatism remain controversial. The failure of both passive and active models of decompression melting to explain adequately the observed volume of volcanism has prompted debate about the relative roles of thermal plume-related melting and ancient subduction-related flux melting. The latter is supported by roughly 500 Ma of subduction along the paleo-Pacific margin of Gondwana, although both processes are capable of producing the broad seismic anomaly imaged beneath most of the Southern Ocean. Olivine-hosted melt inclusions from basanitic lavas provide a means to evaluate the volatile budget of the mantle responsible for active rifting beneath the WARS. We present H2O, CO2, F, S and Cl concentrations determined by SIMS and major oxide compositions by EMPA for olivine-hosted melt inclusions from lavas erupted in Northern Victoria Land (NVL) and Marie Byrd Land (MBL). The melt inclusions are largely basanitic in composition (4.05 - 17.09 wt % MgO, 37.86 - 45.89 wt % SiO2, and 1.20 - 5.30 wt % Na2O), and exhibit water contents ranging from 0.5 up to 3 wt % that are positively correlated with Cl and F. Coupling between Cl and H2O indicates metasomatic enrichment by subduction-related fluids produced during dehydration reactions; coupling between H2O and F, which is more highly retained in subducting slabs, may be related to partial melting of slab remnants [1]. Application of source lithology filters [2] to whole rock major oxide data shows that primitive lavas (MgO wt % >7) from the Terror Rift, considered the locus of on-going tectonomagmatic activity, have transitioned from a pyroxenite source to a volatilized peridotite source over the past ~4 Ma. Integrating the volatile data with the modeled characteristics of source lithologies suggests that partial melting of lithosphere modified by

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  19. Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin

    PubMed Central

    Feldmann, Johannes; Levermann, Anders

    2015-01-01

    The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades’ enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner–Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia. PMID:26578762

  20. Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin.

    PubMed

    Feldmann, Johannes; Levermann, Anders

    2015-11-17

    The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades' enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner-Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia.

  1. Winter and spring controls on the summer food web of the coastal West Antarctic Peninsula.

    PubMed

    Saba, Grace K; Fraser, William R; Saba, Vincent S; Iannuzzi, Richard A; Coleman, Kaycee E; Doney, Scott C; Ducklow, Hugh W; Martinson, Douglas G; Miles, Travis N; Patterson-Fraser, Donna L; Stammerjohn, Sharon E; Steinberg, Deborah K; Schofield, Oscar M

    2014-07-07

    Understanding the mechanisms by which climate variability affects multiple trophic levels in food webs is essential for determining ecosystem responses to climate change. Here we use over two decades of data collected by the Palmer Long Term Ecological Research program (PAL-LTER) to determine how large-scale climate and local physical forcing affect phytoplankton, zooplankton and an apex predator along the West Antarctic Peninsula (WAP). We show that positive anomalies in chlorophyll-a (chl-a) at Palmer Station, occurring every 4-6 years, are constrained by physical processes in the preceding winter/spring and a negative phase of the Southern Annular Mode (SAM). Favorable conditions for phytoplankton included increased winter ice extent and duration, reduced spring/summer winds, and increased water column stability via enhanced salinity-driven density gradients. Years of positive chl-a anomalies are associated with the initiation of a robust krill cohort the following summer, which is evident in Adélie penguin diets, thus demonstrating tight trophic coupling. Projected climate change in this region may have a significant, negative impact on phytoplankton biomass, krill recruitment and upper trophic level predators in this coastal Antarctic ecosystem.

  2. Macrofossil records of West Antarctic Ice Sheet retreat during the Holocene

    NASA Technical Reports Server (NTRS)

    Berkman, Paul Arthur

    1993-01-01

    Marine macrofossils in emerged beaches around Antarctica represent a geochemical framework for interpreting meltwater signatures associated with variations in the adjacent ice sheet margins during the last 10,000 years. In particular, mollusc species provide ideal experimental templates for assessing hydrochemical variations in Antarctic coastal marine environments because of their excellent preservation, high abundances, circumpolar distributions, and carbonate shells, which incorporate trace elements and stable isotopes. Modern samples of the bivalve Adamussium colbecki, which were collected across a depth gradient in the vicinity of a glacial meltwater stream in West McMurdo Sound, revealed shell trace element concentrations that were significantly higher above 10 meters because of their exposure to meltwater runoff. This meltwater signature also was reflected by the shell oxygen isotopic composition, which was in equilibrium with the ambient seawater, as demonstrated by the overlap between the predicted and actual O-(delta-18)sub w values. These modern samples provide analogs for interpreting the geochemical records in their fossils, which were based solely on molluscan fossils, complement the above geochemical data by suggesting that the rate of beach emergence fluctuated around Antarctica during the mid-Holocene. Paleoenvironmental analysis of macrofossils from emerged beaches represents a new direction in Antarctic research that can be used to assess changes in the margins of the ice sheets since the Last Glacial Maximum. The resolution of these analyses will be enhanced by collaborations that are developing with scientists who are conducting comparable studies in other coastal regions around the continent.

  3. High particle export over the continental shelf of the west Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Buesseler, Ken O.; McDonnell, Andrew M. P.; Schofield, Oscar M. E.; Steinberg, Deborah K.; Ducklow, Hugh W.

    2010-11-01

    Drifting cylindrical traps and the flux proxy 234Th indicate more than an order of magnitude higher sinking fluxes of particulate carbon and 234Th in January 2009 than measured by a time-series conical trap used regularly on the shelf of the west Antarctic Peninsula (WAP). The higher fluxes measured in this study have several implications for our understanding of the WAP ecosystem. Larger sinking fluxes result in a revised export efficiency of at least 10% (C flux/net primary production) and a requisite lower regeneration efficiency in surface waters. High fluxes also result in a large supply of sinking organic matter to support subsurface and benthic food webs on the continental shelf. These new findings call into question the magnitude of seasonal and interannual variability in particle flux and reaffirm the difficulty of using moored conical traps as a quantitative flux collector in shallow waters.

  4. West Antarctic Ice Sheet Initiative. Volume 1: Science and Implementation Plan

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert A. (Editor)

    1990-01-01

    The Science and Implementation Plan of the West Antarctic Ice Sheet Initiative (WAIS) is described. The goal of this initiative is the prediction of the future behavior of this ice sheet and an assessment of its potential to collapse, rapidly raising global sea level. The multidisciplinary nature of WAIS reflects the complexity of the polar ice sheet environment. The project builds upon past and current polar studies in many fields and meshes with future programs of both the U.S. and other countries. Important tasks in each discipline are described and a coordinated schedule by which the majority of these tasks can be accomplished in 5 years is presented. The companion report (Volume 2) contains seven discipline review papers on the state of knowledge of Antarctica and opinions on how that knowledge must be increased to attain the WAIS goal.

  5. Aspects of the evolution of the West Antarctic margin of Gondwanaland

    SciTech Connect

    Grunow, A.M.

    1989-01-01

    A combination of paleomagnetism, structural field mapping, microprobe analysis, microfabric analysis and {sup 40}Ar/{sup 39}Ar geochronology was used to elucidate the history of the West Antarctic crustal block and the evolution of subduction complexes along the Scotia Ridge. West Antarctica is composed of four crustal blocks whose relationship to East Antarctica and to each other throughout the Phanerozoic is not well known. These blocks are: the Ellsworth-Whitmore Mountains (EWM); the Antarctic Peninsula (AP); Thurston Island (TI); Marie Byrd Land (MBL). Paleomagnetic sampling and analysis were conducted on rocks from the EWM and TI blocks in the hope of constraining the motion of these blocks and the opening history of the Weddell Sea. The paleomagnetic results suggest that the AP, EWM, and TI blocks have moved relative to East Antarctica prior to the mid-Cretaceous and that the main opening of the Weddell Sea was between the Early and mid-Cretaceous. Detailed field mapping was conducted on the subduction complexes of the Scotia Metamorphic Complex (SMC) on Smith Island and Elephant Island (Antarctica). Polyphase ductile deformation characterizes the Smith Island and Elephant Island tectonites. Microprobe analyses indicate that the blue amphiboles from both areas are primary crossite. Pressure-temperature estimates for Smith Island blueschist metamorphism are {approximately}350 C at 6-7 kbars. The {sup 40}Ar/{sup 39}Ar geochronology indicates a complex thermal evolution for the SMC. The north to south increase in intensity of deformation and metamorphism on Elephant Island corresponds to decrease in {sup 40}Ar/{sup 39}Ar age. Uplift of the Smith Island blueschists occurred since 47 Ma while most of the uplift on Elephant Island occurred since {approximately}102 Ma.

  6. Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts.

    PubMed

    Bingham, Robert G; Ferraccioli, Fausto; King, Edward C; Larter, Robert D; Pritchard, Hamish D; Smith, Andrew M; Vaughan, David G

    2012-07-25

    Current ice loss from the West Antarctic Ice Sheet (WAIS) accounts for about ten per cent of observed global sea-level rise. Losses are dominated by dynamic thinning, in which forcings by oceanic or atmospheric perturbations to the ice margin lead to an accelerated thinning of ice along the coastline. Although central to improving projections of future ice-sheet contributions to global sea-level rise, the incorporation of dynamic thinning into models has been restricted by lack of knowledge of basal topography and subglacial geology so that the rate and ultimate extent of potential WAIS retreat remains difficult to quantify. Here we report the discovery of a subglacial basin under Ferrigno Ice Stream up to 1.5 kilometres deep that connects the ice-sheet interior to the Bellingshausen Sea margin, and whose existence profoundly affects ice loss. We use a suite of ice-penetrating radar, magnetic and gravity measurements to propose a rift origin for the basin in association with the wider development of the West Antarctic rift system. The Ferrigno rift, overdeepened by glacial erosion, is a conduit which fed a major palaeo-ice stream on the adjacent continental shelf during glacial maxima. The palaeo-ice stream, in turn, eroded the 'Belgica' trough, which today routes warm open-ocean water back to the ice front to reinforce dynamic thinning. We show that dynamic thinning from both the Bellingshausen and Amundsen Sea region is being steered back to the ice-sheet interior along rift basins. We conclude that rift basins that cut across the WAIS margin can rapidly transmit coastally perturbed change inland, thereby promoting ice-sheet instability.

  7. Sensitivity of ocean circulation and sea-ice conditions to loss of West Antarctic ice shelves and ice sheet

    NASA Astrophysics Data System (ADS)

    Bougamont, Marion; Hunke, Elizabeth C.; Tulaczyk, Slawek

    We use a global coupled ocean-sea ice model to test the hypothesis that the disintegration of the West Antarctic ice sheet (WAIS), or just its ice shelves, may modify ocean circulation and sea-ice conditions in the Southern Ocean. We compare the results of three model runs: (1) a control run with a standard (modern) configuration of landmask in West Antarctica, (2) a no-shelves run with West Antarctic ice shelves removed and (3) a no-WAIS run. In the latter two runs, up to a few million square kilometres of new sea surface area opens to sea-ice formation, causing the volume and extent of Antarctic sea-ice cover to increase compared with the control run. In general, near-surface waters are cooler around Antarctica in the no-shelves and no-WAIS model runs than in the control run, while warm intermediate and deep waters penetrate further south, increasing poleward heat transport. Varying regional responses to the imposed changes in landmask configuration are determined by the fact that Antarctic polynyas and fast ice develop in different parts of the model domain in each run. Model results suggest that changes in the extent of WAIS may modify oceanographic conditions in the Southern Ocean.

  8. Modelling mass loss and spatial uncertainty of the West Antarctic Ice Sheet: a data assimilation approach

    NASA Astrophysics Data System (ADS)

    Bamber, Jonathan L.; Schoen, Nana; Zammit-Mangion, Andrew; Rougier, Jonty; Luthcke, Scott; King, Matt

    2013-04-01

    loss trends for the West Antarctic Ice Sheet (WAIS) and the AP are estimated at -101 +- 31 Gt per year for 2003-2009, which compares well with other recent estimates for a similar period. The time-invariant will be extended to time evolving and finally to cover the whole of Antarctica. The approach is not limited to the GRACe epoch alone and will also be extended back in time to 1992, at the beginning of the ERS-1 epoch.

  9. Thermal Regime at the Base of the West-Antarctic Ice Stream Tributaries - is the Holocene Decay of the West Antarctic Ice Sheet Coming to an End?

    NASA Astrophysics Data System (ADS)

    Vogel, S. W.; Tulaczyk, S.; Joughin, I.

    2001-12-01

    The possible instability of the West-Antarctic Ice Sheet (WAIS) and its effects on global sea level was in the focus of Antarctic research for more then three decades, since Mercer (1968) proposed that the ice sheet collapsed during previous interglacials. Subsequent collection of field and remotely-sensed data has revealed, among other things, a complex structure in the WAIS drainage system and enabled us to better elucidate the basal processes that permit fast ice-stream motion under low driving stresses (e.g. Kamb, 2001). With high basal water pressures and a layer of weak, highly porous water saturated sediments playing a key role in facilitating the fast motion of ice in West-Antarctica, the spatial and temporal availability of basal water has to be incorporated into models simulating the present and future WAIS behavior. Borehole observations in the interior of the WAIS (Robin, 1983) and in the Siple Coast ice streams (Engelhardt and Kamb, 1987) revealed a wet ice sheet bed and the ice at the base of the ice sheet being at its pressure melting. However the recent discovery of an up to 25 m thick basal ice layer at Ice Stream C indicates that basal melting either does not persist along the entire ice stream tributaries or did not persisted in the past. Lacking direct observations from the ice stream tributaries we are currently using finite-difference and analytical models to assess their basal energy balance; heat conduction away from the bed, geothermal flux and shear heating. Taking into account the uncertainty in the estimation of the geothermal flux (50 to 80 mW*m\\^-2 ), the results of our calculations can be summarized as followed 1) the basal ice layer formed in the central part of the northern Ice Stream C tributary; 2) post Last Glacial Maximum conditions favor basal freezing in spite of higher surface temperatures; 3) the presence of a 12-25-m-thick basal ice layer request that either 3a) flow in the ice stream tributaries had stopped in the past

  10. Transect across the West Antarctic rift system in the Ross Sea, Antarctica

    USGS Publications Warehouse

    Trey, H.; Cooper, A. K.; Pellis, G.; Della, Vedova B.; Cochrane, G.; Brancolini, Giuliano; Makris, J.

    1999-01-01

    In 1994, the ACRUP (Antarctic Crustal Profile) project recorded a 670-km-long geophysical transect across the southern Ross Sea to study the velocity and density structure of the crust and uppermost mantle of the West Antarctic rift system. Ray-trace modeling of P- and S-waves recorded on 47 ocean bottom seismograph (OBS) records, with strong seismic arrivals from airgun shots to distances of up to 120 km, show that crustal velocities and geometries vary significantly along the transect. The three major sedimentary basins (early-rift grabens), the Victoria Land Basin, the Central Trough and the Eastern Basin are underlain by highly extended crust and shallow mantle (minimum depth of about 16 km). Beneath the adjacent basement highs, Coulman High and Central High, Moho deepens, and lies at a depth of 21 and 24 km, respectively. Crustal layers have P-wave velocities that range from 5.8 to 7.0 km/s and S-wave velocities from 3.6 to 4.2 km/s. A distinct reflection (PiP) is observed on numerous OBS from an intra-crustal boundary between the upper and lower crust at a depth of about 10 to 12 km. Local zones of high velocities and inferred high densities are observed and modeled in the crust under the axes of the three major sedimentary basins. These zones, which are also marked by positive gravity anomalies, may be places where mafic dikes and sills pervade the crust. We postulate that there has been differential crustal extension across the West Antarctic rift system, with greatest extension beneath the early-rift grabens. The large amount of crustal stretching below the major rift basins may reflect the existence of deep crustal suture zones which initiated in an early stage of the rifting, defined areas of crustal weakness and thereby enhanced stress focussing followed by intense crustal thinning in these areas. The ACRUP data are consistent with the prior concept that most extension and basin down-faulting occurred in the Ross Sea during late Mesozoic time, with

  11. Activity and bacterial diversity of snow around Russian Antarctic stations.

    PubMed

    Lopatina, Anna; Krylenkov, Vjacheslav; Severinov, Konstantin

    2013-11-01

    The diversity and temporal dynamics of bacterial communities in pristine snow around two Russian Antarctic stations was investigated. Taxonomic analysis of rDNA libraries revealed that snow communities were dominated by bacteria from a small number of operational taxonomic units (OTUs) that underwent dramatic swings in abundance between the 54th (2008-2009) and 55th (2009-2010) Russian Antarctic expeditions. Moreover, analysis of the 55th expedition samples indicated that there was very little, if any, correspondence in abundance of clones belonging to the same OTU present in rDNA and rRNA libraries. The latter result suggests that most rDNA clones originate from bacteria that are not alive and/or active and may have been deposited on the snow surface from the atmosphere. In contrast, clones most abundant in rRNA libraries (mostly belonging to Variovorax, Janthinobacterium, Pseudomonas, and Sphingomonas genera) may be considered as endogenous Antarctic snow inhabitants.

  12. Airborne gravity and other geophysical techniques for understanding the lithosphere beneath the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Bell, Robin E.; Blankenship, Donald D.; Hodge, Steven M.; Brozena, John M.; Behrendt, John C.

    1993-01-01

    As part of a program entitled Corridor Aerogeophysics of the Southeastern Ross Transect Zone (CASERTZ), an aerogeophysical platform was developed to study the interaction of geological and glaciological processes in West Antarctica. A de Havilland Twin Otter was equipped with an ice-penetrating radar, a proton precession magnetometer, an airborne gravity system, and a laser altimeter. The 60-MHz ice-penetrating radar can recover sub-ice topography with an accuracy of about 10 m through 3 km of comparatively warm West Antarctic ice, while the laser altimeter profiling of the ice surface is accurate to approximately 1 m. The magnetic field observations are accurate to several nT, and the gravity measurements are accurate to better than 3 mGal. The aircraft is navigated by a local radio transponder network, while differential positioning techniques based on the Global Positioning System (GPS) satellites are used for recovering high-resolution horizontal and vertical positions. Attitude information from an inertial navigation system is used to correct the laser altimetry and a digital pressure transducer is used to recover vertical positions and accelerations in the absence of satellite positioning. Continuous base-station observations are made for the differential GPS positioning and the removal of ionospheric noise from the airborne magnetometer measurements.

  13. Sub-Kilometer Scale Basal Roughness of the Siple Coast Ice Streams, West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Young, D. A.; Blankenship, D. D.; Peters, M. E.

    2006-12-01

    The anastomosing series of dynamic, basally lubricated ice streams found on the Siple Coast of West Antarctica play an important role in regulating the mass balance of the West Antarctic Ice Sheet (WAIS). Geological controls on lubrication, elucidated by gravity, magnetics and seismic data, have proven important in understanding the evolution of these features. An additional indicator of basal properties, the basal roughness of ice sheets, may be an indicator of crustal geology and glacial modification, as well as a controlling parameter on ice dynamics and subglacial hydrology. For the Siple Coast ice streams, Fourier analysis of > 5 kilometer morphology (Siegert et al. 2004) revealed a correlation between ice streams and low bed roughness. Coherent high resolution data allows analysis of along track roughness at tens of meters resolution (Peters et al. 2005), however these data are limited in coverage. We extend roughness estimates into to the hundreds-of-meters length scale, using both frequency domain and autocorrelation methods, using incoherent 60 MHz radio echo sounding data collected between 1991 and 1996 on a five kilometer grid. The data cover the Bentley Subglacial Trench, Bindschadler Ice Stream, Siple Dome and the onset region of Kamb Ice Stream. SAR-processed coherent sounding data collected in 2001 are used to confirm these methods. We test for confinement of ice stream rapid basal motion to distinct morphological provinces; assess the hypothesis that marine sediments blanket much of interior of the basal WAIS; and look for correlation between ice flow and textural anisotropy.

  14. Revised Eocene-Oligocene kinematics for the West Antarctic rift system

    NASA Astrophysics Data System (ADS)

    Granot, R.; Cande, S. C.; Stock, J. M.; Damaske, D.

    2013-01-01

    Abstract<p label="1">Past plate motion between East and <span class="hlt">West</span> Antarctica along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system had important regional and global implications. Although extensively studied, the kinematics of the rift during Eocene-Oligocene time still remains elusive. Based on a recent detailed aeromagnetic survey from the Adare and Northern Basins, located in the northwestern Ross Sea, we present the first well-constrained kinematic model with four rotations for Anomalies 12o, 13o, 16y, and 18o (26.5-40.13 Ma). These rotation poles form a cluster suggesting a stable sense of motion during that period of time. The poles are located close to the central part of the rift implying that the local motion varied from extension in the western Ross Sea sector (Adare Basin, Northern Basin, and Victoria Land Basin) to dextral transcurrent motion in the Ross Ice Shelf and to oblique convergence in the eastern end of the rift zone. The results confirm previous estimates of 95 km of extension in the Victoria Land Basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C13H..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C13H..04S"><span>A 19-year radar altimeter elevation change time-series of the East and <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sundal, A. V.; Shepherd, A.; Wingham, D.; Muir, A.; Mcmillan, M.; Galin, N.</p> <p>2012-12-01</p> <p>We present 19 years of continuous radar altimeter observations of the East and <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheets acquired by the ERS-1, ERS-2, and ENVISAT satellites between May 1992 and September 2010. Time-series of surface elevation change were developed at 39,375 crossing points of the satellite orbit ground tracks using the method of dual cycle crossovers (Zwally et al., 1989; Wingham et al., 1998). In total, 46.5 million individual measurements were included in the analysis, encompassing 74 and 76 % of the East and <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet, respectively. The satellites were cross-calibrated by calculating differences between elevation changes occurring during periods of mission overlap. We use the merged time-series to explore spatial and temporal patterns of elevation change and to characterise and quantify the signals of <span class="hlt">Antarctic</span> ice sheet imbalance. References: Wingham, D., Ridout, A., Scharroo, R., Arthern, R. & Shum, C.K. (1998): <span class="hlt">Antarctic</span> elevation change from 1992 to 1996. Science, 282, 456-458. Zwally, H. J., Brenner, A. C., Major, J. A., Bindschadler, R. A. & Marsh, J. G. (1989): Growth of Greenland ice-sheet - measurements. Science, 246, 1587-1589.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T13A2514Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T13A2514Q"><span>Understanding the thermal and tectonic evolution of Marie Byrd Land from a reanalysis of airborne geophysical data in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Quartini, E.; Powell, E. M.; Richter, T.; Damiani, T.; Burris, S. G.; Young, D. A.; Blankenship, D. D.</p> <p>2013-12-01</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS) is a region characterized by a significant topographic range, a complex tectonic history, and <span class="hlt">active</span> subglacial volcanism. Those elements exert a large influence on the stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet, which flows within the cradle-shaped rift system and is currently grounded well below sea level. This potentially unstable configuration is the motivation for gaining a better understanding of the ice sheet boundary conditions dictated by rift evolution and how they impact the ice flow. In this study we focus on characterizing the distribution of and transition between sedimentary basins and inferred geothermal heat flux from the flanks to the floor of the rift system. We do so through analysis of gravity data both for sources within the deep lithosphere and near surface targets in the crust. A compilation of gravity datasets over <span class="hlt">West</span> and Central Antarctica and the analysis thereof is presented. In particular we use gravity data collected during several airborne geophysical surveys: CASERTZ (1994-1997), SOAR/WMB (1997-1998), AGASEA (2004-2005), ICEBRIDGE (2008-2011), and GIMBLE (2012-2013). New processing and data reduction methodologies are applied to the older gravity surveys to improve the high frequency signal content and to make these surveys compatible with modern works (i.e. AGASEA, ICEBRIDGE, GIMBLE). The high frequency signal provides better resolution of small-scale features within survey blocks but long-wavelength integrity is retained by registering the airborne free-air disturbance within those blocks to the gravity disturbance derived from the GOCE global satellite gravity field. This allows for consistent long wavelength interpretation across the merged surveys and provides improved gravity analysis of the deep lithosphere while retaining the capacity to study smaller scale features. A crustal model for the area is produced using the Bouguer anomaly and spectral analyses of the Bouguer anomaly and free</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JGRB..11011103O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JGRB..11011103O"><span>Flow of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet on the continental margin of the Bellingshausen Sea at the Last Glacial Maximum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ó Cofaigh, Colm; Larter, Rob D.; Dowdeswell, Julian A.; Hillenbrand, Claus-Dieter; Pudsey, Carol J.; Evans, Jeffrey; Morris, Peter</p> <p>2005-11-01</p> <p>Geophysical data show that during the last glaciation the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) drained to the continental shelf edge of the Bellingshausen Sea through a cross-shelf bathymetric trough (Belgica Trough) as a grounded, fast flowing, ice stream. The drainage basin feeding this ice stream probably encompassed southwestern Palmer Land, parts of southern Alexander Island, and the Bryan Coast of Ellsworth Land, with an area exceeding 200,000 km2. On the inner continental shelf, streamlined bedrock and drumlins mapped by swath bathymetry show that the ice stream was fed by convergent ice flow draining from Eltanin Bay and bays to the east, as well as by ice draining the southern part of the <span class="hlt">Antarctic</span> Peninsula Ice Sheet through the Ronne Entrance. The presence of a paleoice stream in Belgica Trough is indicated by megascale glacial lineations formed in soft till and a trough mouth fan on the continental margin. Grounding zone wedges on the inner and midshelf record ice marginal stillstands during deglaciation and imply a staggered pattern of ice sheet retreat. These new data indicate an extensive WAIS at the Last Glacial Maximum (LGM) on the Bellingshausen Sea continental margin, which advanced to the shelf edge. In conjunction with ice sheet reconstructions from the <span class="hlt">Antarctic</span> Peninsula and Pine Island Bay, this implies a regionally extensive ice sheet configuration during the LGM along the <span class="hlt">Antarctic</span> Peninsula, Bellingshausen Sea, and Amundsen Sea margins, with fast flowing ice streams draining the WAIS and <span class="hlt">Antarctic</span> Peninsula Ice Sheet to the continental shelf edge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020983','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020983"><span>Aeromagnetic evidence for a volcanic caldera(?) complex beneath the divide of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Behrendt, John C.; Finn, C.A.; Blankenship, D.; Bell, R.E.</p> <p>1998-01-01</p> <p>A 1995-96 aeromagnetic survey over part of the Sinuous Ridge (SR) beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) divide shows a 70-km diameter circular pattern of 400-1200-nT anomalies suggesting one of the largest volcanic caldera(?) complexes on earth. Radar-ice-sounding (RIS) shows the northern part of this pattern overlies the SR, and extends south over the Bentley Subglacial Trench (BST). Modeled sources of all but one the caldera(?) anomalies are at the base of <1-2-km thick ice and their volcanic edifices have been glacially removed. The exception is a 700-m high, 15-km wide 'volcano' producing an 800-nT anomaly over the BST. 'Intrusion' of this 'volcano' beneath 3 km of ice probably resulted in pillow basalt rather than easily removed hyaloclastite erupted beneath thinner ice. The background area (-300 to -500-nT) surrounding the caldera(?) is possibly caused by a shallow Curie isotherm. We suggest uplift of the SR forced the advance of the WAIS.A 1995-96 aeromagnetic survey over part of the Sinuous Ridge (SR) beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) divide shows a 70-km diameter circular pattern of 400-1200-nT anomalies suggesting one of the largest volcanic caldera(?) complexes on earth. Radar-ice-sounding (RIS) shows the northern part of this pattern overlies the SR, and extends south over the Bentley Subglacial Trench (BST). Modeled sources of all but one the caldera(?) anomalies are at the base of < 1-2-km thick ice and their volcanic edifices have been glacially removed. The exception is a 700-m high, 15-km wide 'volcano' producing an 800-nT anomaly over the BST. 'Intrusion' of this 'volcano' beneath 3 km of ice probably resulted in pillow basalt rather than easily removed hyaloclastite erupted beneath thinner ice. The background area (-300 to -500-nT) surrounding the caldera(?) is possibly caused by a shallow Curie isotherm. We suggest uplift of the SR forced the advance of the WAIS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T12A..05Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T12A..05Y"><span>Geoologic controls on the architecture of the <span class="hlt">Antarctic</span> Ice Sheet's basal interface: New results from <span class="hlt">West</span> and East Antarctica from long range geophysics (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Young, D. A.; Blankenship, D. D.; Greenbaum, J. S.; Richter, T.; Aitken, A.; Siegert, M. J.; Roberts, J. L.</p> <p>2013-12-01</p> <p>The ice-rock interface underlying the <span class="hlt">Antarctic</span> Ice Sheet was shaped by interactions between underlying gondwanan geology and the overlying ice sheet. The ice sheet now preserves from sedimentary infill an incredibly rugged terrain which now plays a critical role in shaping subglacial hydrology, and thus shape ice sheet behavior. This terrain can by imaged through aerogeophysical means, in particular through ice penetrating radar, while airborne potential fields measurements provide insight into the geological framework that controlled erosion. Over the post IPY era, the density of airborne coverage is only now reaching the point where small scale structure can be identified and placed in context. Of particular importance is understanding the formation of focused erosional valleys, 30-50 km wide, representing now buried subglacial fjords. After initial data from the GIMBLE project in <span class="hlt">West</span> Antarctica, and five years of sustained long range ICECAP surveys over East Antarctica , we now have a better view of the diversity of these features. The local erosion of these valleys, often cutting through significant topographic barriers, irregularly samples the underlying geology, provided a complex story in the sediment to the <span class="hlt">Antarctic</span> margin. These valleys now provide the subglacial conduits for significant ice sheet catchments, in particular for subglacial water, including the inland catchments of DeVicq, Thwaites, and Pine Island Glaciers in <span class="hlt">West</span> Antarctica, and Denman Glacier, Totten Glacier, Byrd Glacier and Cook Ice Shelf in East Antarctica. We find that these features, now sometimes hundreds of kilometers inland of the modern grounding line, often nucleate on or are aligned with structure inherited from the assembly of the <span class="hlt">Antarctic</span> continent. While many of these features currently host <span class="hlt">active</span> outlet glaciers or their tributaries, some do not, implying avenues for ice sheet change. In <span class="hlt">West</span> Antarctica, we find a new deep connection between the coast and interior basin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMEP13A0920L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMEP13A0920L"><span>Multichannel Seismic Investigations of Sediment Drifts off <span class="hlt">West</span> Antarctica and the <span class="hlt">Antarctic</span> Peninsula: Preliminary Results from Research Cruise JR298</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Larter, R. D.; Graham, A. G. C.; Hernandez-Molina, J.; Channell, J. E. T.; Hillenbrand, C. D.; Hogan, K. A.; Uenzelmann-Neben, G.; Gohl, K.; Rebesco, M.; Hodell, D. A.</p> <p>2015-12-01</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) and <span class="hlt">Antarctic</span> Peninsula Ice Sheet (APIS) have exhibited significant changes over recent decades but there is still great uncertainty about how rapidly and how far they will retreat in a warmer climate. For example, it remains unclear whether or not the marine-based WAIS "collapsed" during the last interglacial period, resulting in a global sea-level rise contribution of more than 3 m. Previous studies, including Ocean Drilling Program (ODP) Leg 178, have shown that sediment drifts on the continental rise <span class="hlt">west</span> of the <span class="hlt">Antarctic</span> Peninsula contain a rich high-resolution archive of <span class="hlt">Antarctic</span> margin paleoceanography and APIS history that extends back to at least the Late Miocene. The potential of existing ODP cores from the drifts is, however, compromised by the fact that composite sections are incomplete and lack of precise chronological control. A new drilling proposal (732-Full2) has been scientifically approved and is with the JOIDES Resolution Facilities Board of the International Ocean Discovery Program for scheduling. The main aims of the proposal are to obtain continuous, high-resolution records from sites on sediment drifts off both the <span class="hlt">Antarctic</span> Peninsula and <span class="hlt">West</span> Antarctica (southern Bellingshausen Sea) and to achieve good chronological control on them using a range of techniques. We present preliminary results from a recent site survey investigation cruise on RRS James Clark Ross (JR298) that obtained high-resolution multichannel seismic reflection data over the proposed sites and adjacent working areas. The new data provide a basis for interpretation of (i) sedimentary processes that operated during the development of the drifts, and (ii) links between depositional systems on the continental rise, paleo-ice-sheet dynamics and paleoceanographic processes. Through further analyses of seismic and other geophysical data, in combination with marine sediment cores retrieved from the proposed sites, we aim to provide insight into</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GPC...119...56C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GPC...119...56C"><span>Dynamics of the late Plio-Pleistocene <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet documented in subglacial diamictites, AND-1B drill core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cowan, Ellen A.; Christoffersen, Poul; Powell, Ross D.; Talarico, Franco M.</p> <p>2014-08-01</p> <p>Geologic studies of sediment deposited by glaciers can provide crucial insights into the subglacial environment. We studied muddy diamictites in the <span class="hlt">ANtarctic</span> geological DRILLing (ANDRILL) AND-1B drill core, acquired from beneath the Ross Ice Shelf in McMurdo Sound, with the aim of identifying paleo-ice stream <span class="hlt">activity</span> in the Plio-Pleistocene. Glacial advances were identified from glacial surfaces of erosion (GSEs) and subglacial diamictites within three complete sequences were investigated using lithofacies associations, micromorphology, and quartz sand grain microtextures. Whereas conditions in the Late Pliocene resemble the modern Greenland Ice Sheet where fast flowing glaciers lubricated by surface meltwater terminate directly in the sea (interval 201-212 mbsl) conditions in the Late Pleistocene are similar to modern <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) ice streams (38-49 mbsl). We identify the latter from ductile deformation and high pore-water pressure, which resulted in pervasive rotation and formation of till pellets and low relief, rounded sand grains dominated by abrasion. In the transitional period during the Mid-Pleistocene (55-68 mbsf), a slow moving inland ice sheet deposited tills with brittle deformation, producing lineations and bi-masepic and unistrial plasma fabric, along with high relief, conchoidally fractured quartz grains. Changes in the provenance of gravel to cobble-size clasts support a distant source area of Byrd Glacier for fast-flowing paleo-ice streams and a proximal area between Darwin and Skelton Glaciers for the slow-moving inland ice sheet. This difference in till provenance documents a shift in direction of glacial flow at the core site, which indirectly reflects changes in the size and thickness of the WAIS. Hence, we found that fast ice streaming motion is a consequence of a thicker WAIS pushing flow lines to the <span class="hlt">west</span> and introducing clasts from the Byrd Glacier source area to the drill site. The detailed analysis of diamictites in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646773','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646773"><span>High geothermal heat flux measured below the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fisher, Andrew T.; Mankoff, Kenneth D.; Tulaczyk, Slawek M.; Tyler, Scott W.; Foley, Neil</p> <p>2015-01-01</p> <p>The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region. PMID:26601210</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26601210','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26601210"><span>High geothermal heat flux measured below the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fisher, Andrew T; Mankoff, Kenneth D; Tulaczyk, Slawek M; Tyler, Scott W; Foley, Neil</p> <p>2015-07-01</p> <p>The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m(2), significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m(2). The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C13B0547J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C13B0547J"><span>Siple Dome Ice Cores: Implications for <span class="hlt">West</span> <span class="hlt">Antarctic</span> Climate and ENSO Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, T.; White, J. W.</p> <p>2010-12-01</p> <p>Ice cores at Siple Dome, <span class="hlt">West</span> <span class="hlt">Antarctic</span> receive the majority of their precipitation from Pacific Ocean moisture sources. Pacific climate patterns, particularly the El Niño-Southern Oscillation, affect the local temperature, atmospheric circulation, and snow accumulation at Siple Dome, as well as isotopic signals (∂D and ∂18O). We examined isotopes, accumulation and borehole temperatures from a number of shallow ice cores distributed 60km across the Dome. The data reveal a strong microclimate heavily influenced by South Pacific climate and the location of the Amundsen Sea Low Pressure Area. The Dome Summit and Pacific Flank respond to La Niña conditions by warming, increasing isotope ratios and increased snowfall. The Inland Flank responds to El Niño conditions and cold interior air masses by cooling, decreasing isotope ratios and decreased snowfall. Spectral analysis of the ∂D record shows a distinct shift in ocean-atmosphere climate dynamics in the late 19th century, where scattered bi-decadal to decadal periodicities change to include more intensely grouped and decreasing periodicities as low as two years at the end of the 20th century. Similar changes are seen in South Pacific coral isotope records. Map of Siple Dome including local grid locations for the seven shallow cores B-H. Note the Pacific Ocean and Inland (South Pole) oriented cores. [Modified after Bertler et al., 2006].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16782601','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16782601"><span>The environment and evolution of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet: setting the stage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bindschadler, Robert</p> <p>2006-07-15</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet is the last ice sheet of the type cradled in a warm, marine geologic basin. Its perimeter stretches into the surrounding seas allowing warmer ocean waters to reach the undersides of its floating ice shelves and its relatively low surface elevation permits snow-carrying storms to extend well into its interior. This special environment has given rise to theories of impending collapse and for the past quarter-century has challenged researchers who seek a quantitative prediction of its future behaviour and the corresponding effect on sea level. Observations confirm changes on a variety of time scales from the quaternary to less than a minute. The dynamics of the ice sheet involve the complex interaction of ice that is warm at its base and cold along the margins of ice streams; subglacial till that is composed of a combination of marine sediment and eroded sedimentary rocks; and water that moves primarily between the ice and bed, but whose flow direction can differ from the direction of ice motion. The pressure of the water system is often sufficient to float the ice sheet locally and small changes in the amount of water in the till can cause it to rapidly switch from very weak to very stiff.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC13C0646H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC13C0646H"><span>The Global and Local Climatic Response to the Collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huybers, K. M.; Singh, H.; Steiger, N. J.; Frierson, D. M.; Steig, E. J.; Bitz, C. M.</p> <p>2014-12-01</p> <p>Glaciologists have suggested that a relatively small external forcing may compromise the stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080032486&hterms=west+antarctic+ice+shelf&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwest%2Bantarctic%2Bice%2Bshelf','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080032486&hterms=west+antarctic+ice+shelf&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwest%2Bantarctic%2Bice%2Bshelf"><span>Recent Ice Loss from the Fleming and Other Glaciers, Wordie Bay, <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, E.; Casassa, G.; Gogineni, S.; Kanagaratnam, P.; Krabill, W.; Pritchard, H.; Rivera, A.; Thomas, R.; Turner, J.; Vaughan, D.</p> <p>2005-01-01</p> <p>Satellite radar interferometry data from 1995 to 2004, and airborne ice thickness data from 2002, reveal that the glaciers flowing into former Wordie Ice Shelf, <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula, discharge 6.8 +/- 0.3 km(exp 3)/yr of ice, which is 84 +/- 30 percent larger than a snow accumulation of 3.7 +/- 0.8 km(exp 3)/yr over a 6,300 km(exp 2) drainage basin. Airborne and ICESat laser altimetry elevation data reveal glacier thinning at rates up to 2 m/yr. Fifty km from its ice front, Fleming Glacier flows 50 percent faster than it did in 1974 prior to the main collapse of Wordie Ice Shelf. We conclude that the glaciers accelerated following ice shelf removal, and have been thinning and losing mass to the ocean over the last decade. This and other observations suggest that the mass loss from the northern part of the Peninsula is not negligible at present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.5069C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.5069C"><span>Mixing and phytoplankton dynamics in a submarine canyon in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carvalho, Filipa; Kohut, Josh; Oliver, Matthew J.; Sherrell, Robert M.; Schofield, Oscar</p> <p>2016-07-01</p> <p>Bathymetric depressions (canyons) exist along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula shelf and have been linked with increased phytoplankton biomass and sustained penguin colonies. However, the physical mechanisms driving this enhanced biomass are not well understood. Using a Slocum glider data set with over 25,000 water column profiles, we evaluate the relationship between mixed layer depth (MLD, estimated using the depth of maximum buoyancy frequency) and phytoplankton vertical distribution. We use the glider deployments in the Palmer Deep region to examine seasonal and across canyon variability. Throughout the season, the ML becomes warmer and saltier, as a result of vertical mixing and advection. Shallow ML and increased stratification due to sea ice melt are linked to higher chlorophyll concentrations. Deeper mixed layers, resulting from increased wind forcing, show decreased chlorophyll, suggesting the importance of light in regulating phytoplankton productivity. Spatial variations were found in the canyon head region where local physical water column properties were associated with different biological responses, reinforcing the importance of local canyon circulation in regulating phytoplankton distribution in the region. While the mechanism initially hypothesized to produce the observed increases in phytoplankton over the canyons was the intrusion of warm, nutrient enriched modified Upper Circumpolar Deep Water (mUCDW), our analysis suggests that ML dynamics are key to increased primary production over submarine canyons in the WAP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55..323C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55..323C"><span>Upper ocean variability in <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula continental shelf waters as measured using instrumented seals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Costa, Daniel P.; Klinck, John M.; Hofmann, Eileen E.; Dinniman, Michael S.; Burns, Jennifer M.</p> <p>2008-02-01</p> <p>Temperature profile data for the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula (WAP) continental shelf waters, collected from freely ranging instrumented seals (crabeater, Lobodon carcinophagus and leopard, Hydrurga leptonyx), were used to demonstrate that these platforms can be used to supplement traditional oceanographic sampling methods to investigate the physical properties of the upper water column. The seal-derived profiles were combined with temperature profiles obtained from ship-based CTD measurements and from a numerical circulation model developed for the WAP to describe changes in temperature structure, heat content, and heat flux in the upper ocean waters of the WAP continental shelf. The seal-derived data documented the fall-to-winter transition of the surface waters and the shelf-wide presence of modified Circumpolar Deep Water (CDW) below 150-200 m on the WAP continental shelf. The heat content of the upper 200 m calculated from the seal-derived temperature profiles ranged between 1000 and 1500 MJ m -2; similar estimates were obtained from simulated temperature distributions. The seal-derived temperature measurements provided broader space and time resolution than was possible using any other currently available oceanographic sampling method. As such, the seal-derived measurements provided a valuable dataset for evaluation of temperature fields obtained from a numerical circulation model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3259932','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3259932"><span>A large population of king crabs in Palmer Deep on the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula shelf and potential invasive impacts</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Smith, Craig R.; Grange, Laura J.; Honig, David L.; Naudts, Lieven; Huber, Bruce; Guidi, Lionel; Domack, Eugene</p> <p>2012-01-01</p> <p>Lithodid crabs (and other skeleton-crushing predators) may have been excluded from cold <span class="hlt">Antarctic</span> continental shelf waters for more than 14 Myr. The <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula shelf is warming rapidly and has been hypothesized to be soon invaded by lithodids. A remotely operated vehicle survey in Palmer Deep, a basin 120 km onto the <span class="hlt">Antarctic</span> shelf, revealed a large, reproductive population of lithodids, providing the first evidence that king crabs have crossed the <span class="hlt">Antarctic</span> shelf. DNA sequencing and morphology indicate the lithodid is Neolithodes yaldwyni Ahyong & Dawson, previously reported only from Ross Sea waters. We estimate a N. yaldwyni population density of 10 600 km−2 and a population size of 1.55 × 106 in Palmer Deep, a density similar to lithodid populations of commercial interest around Alaska and South Georgia. The lithodid occurred at depths of more than 850 m and temperatures of more than 1.4°C in Palmer Deep, and was not found in extensive surveys of the colder shelf at depths of 430–725 m. Where N. yaldwyni occurred, crab traces were abundant, megafaunal diversity reduced and echinoderms absent, suggesting that the crabs have major ecological impacts. <span class="hlt">Antarctic</span> Peninsula shelf waters are warming at approximately 0.01°C yr−1; if N. yaldwyni is currently limited by cold temperatures, it could spread up onto the shelf (400–600 m depths) within 1–2 decades. The Palmer Deep N. yaldwyni population provides an important model for the potential invasive impacts of crushing predators on vulnerable <span class="hlt">Antarctic</span> shelf ecosystems. PMID:21900324</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21900324','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21900324"><span>A large population of king crabs in Palmer Deep on the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula shelf and potential invasive impacts.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Smith, Craig R; Grange, Laura J; Honig, David L; Naudts, Lieven; Huber, Bruce; Guidi, Lionel; Domack, Eugene</p> <p>2012-03-07</p> <p>Lithodid crabs (and other skeleton-crushing predators) may have been excluded from cold <span class="hlt">Antarctic</span> continental shelf waters for more than 14 Myr. The <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula shelf is warming rapidly and has been hypothesized to be soon invaded by lithodids. A remotely operated vehicle survey in Palmer Deep, a basin 120 km onto the <span class="hlt">Antarctic</span> shelf, revealed a large, reproductive population of lithodids, providing the first evidence that king crabs have crossed the <span class="hlt">Antarctic</span> shelf. DNA sequencing and morphology indicate the lithodid is Neolithodes yaldwyni Ahyong & Dawson, previously reported only from Ross Sea waters. We estimate a N. yaldwyni population density of 10 600 km(-2) and a population size of 1.55 × 10(6) in Palmer Deep, a density similar to lithodid populations of commercial interest around Alaska and South Georgia. The lithodid occurred at depths of more than 850 m and temperatures of more than 1.4°C in Palmer Deep, and was not found in extensive surveys of the colder shelf at depths of 430-725 m. Where N. yaldwyni occurred, crab traces were abundant, megafaunal diversity reduced and echinoderms absent, suggesting that the crabs have major ecological impacts. <span class="hlt">Antarctic</span> Peninsula shelf waters are warming at approximately 0.01°C yr(-1); if N. yaldwyni is currently limited by cold temperatures, it could spread up onto the shelf (400-600 m depths) within 1-2 decades. The Palmer Deep N. yaldwyni population provides an important model for the potential invasive impacts of crushing predators on vulnerable <span class="hlt">Antarctic</span> shelf ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.8722B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.8722B"><span>Geophysical glimpses into the Ferrigno Rift at the northwestern tip of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bingham, Robert; Ferraccioli, Fausto</p> <p>2014-05-01</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS) forms one of the largest continental rift systems on Earth. The WARS is of major significance as it forms the lithospheric cradle for the marine-based and potentially unstable <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS). Seismic refraction, reflection, aeromagnetic, gravity and drilling in the Ross Sea have revealed most of what we know about its structure, tectonic and magmatic patterns and sedimentary basins. Aerogeophysical research and passive seismic networks have considerably extended our knowledge of the WARS and its influence on the overlying WAIS in the Siple Coast and Amundsen Sea Embayment (ASE) regions. The Bellingshausen Sea Embayment region has however remained largely unexplored, and hence the possible extent of the WARS in this sector has remained poorly constrained. Here we use a combination of reconnaissance ground-based and airborne radar observations, airborne gravity, satellite gravity and aeromagnetic data to investigate the WARS in the Bellingshausen Sea Embayment, in the area of the Ferrigno Ice Stream (Bingham et al., 2012, Nature). This region is of high significance, as it one of the main sectors of the WAIS that is currently exhibiting rapid ice loss, thought to be driven primarily by oceanic warming. Assessing geological controls on subice topography and ice dynamics is therefore of prime importance in this part of the WAIS. Ground-based and airborne radar image a subglacial basin beneath the Ferrigno Ice Stream that is up to 1.5 kilometres deep and that connects the ice-sheet interior to the Bellingshausen Sea margin. We interpret this basin as a narrow, glacially overdeepened rift basin that formed at the northwestern tip of the WARS. Satellite gravity data cannot resolve such a narrow rift basin but indicate that the crust beneath the region is likely thinned, lending support to the hypothesis that this area is indeed part of the WARS. Widely-spaced aeromagnetic data image a linear low along the inferred</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712219S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712219S"><span>Oceanic an climatic consequences of a sudden large-scale <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet collapse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scarff, Katie; Green, Mattias; Schmittner, Andreas</p> <p>2015-04-01</p> <p>Atmospheric warming is progressing to the point where the <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002312','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002312"><span>Mass Balance of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice-Sheet from ICESat Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Robins, John; Saba, Jack L.; Yi, Donghui</p> <p>2011-01-01</p> <p>Mass balance estimates for 2003-2008 are derived from ICESat laser altimetry and compared with estimates for 1992-2002 derived from ERS radar altimetry. The net mass balance of 3 drainage systems (Pine Island, Thwaites/Smith, and the coast of Marie Bryd) for 2003-2008 is a loss of 100 Gt/yr, which increased from a loss of 70 Gt/yr for the earlier period. The DS including the Bindschadler and MacAyeal ice streams draining into the Ross Ice Shelf has a mass gain of 11 Gt/yr for 2003-2008, compared to an earlier loss of 70 Gt/yr. The DS including the Whillans and Kamb ice streams has a mass gain of 12 Gt/yr, including a significant thickening on the upper part of the Kamb DS, compared to a earlier gain of 6 Gt/yr (includes interpolation for a large portion of the DS). The other two DS discharging into the Ronne Ice Shelf and the northern Ellsworth Coast have a mass gain of 39 Gt/yr, compared to a gain of 4 Gt/yr for the earlier period. Overall, the increased losses of 30 Gt/yr in the Pine Island, Thwaites/Smith, and the coast of Marie Bryd DSs are exceeded by increased gains of 59 Gt/yr in the other 4 DS. Overall, the mass loss from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet has decreased to 38 Gt/yr from the earlier loss of 67 Gt/yr, reducing the contribution to sea level rise to 0.11 mm/yr from 0.19 mm/yr</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70016810','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70016810"><span>Evidence of rapid Cenozoic uplift of the shoulder escarpment of the Cenozoic <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system and a speculation on possible climate forcing</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Behrendt, John C.; Cooper, A.</p> <p>1991-01-01</p> <p>The Cenozoic <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system, characterized by Cenozoic bimodal alkalic volcanic rocks, extends over a largely ice-covered area, from the Ross Sea nearly to the Bellingshausen Sea. Various lines of evidence lead to the following interpretation: the transantarctic Mountains part of the rift shoulder (and probably the entire shoulder) has been rising since about 60 Ma, at episodic rates of ~1 km/m.y., most recently since mid-Pliocene Time, rather than continuously at the mean rate of 100 m/m.y. Uplift rates vary along the scarp, which is cut by transverse faults. It is speculated that this uplift may have climatically forced the advance of the <span class="hlt">Antarctic</span> ice sheet since the most recent warm period. A possible synergistic relation is suggested between episodic tectonism, mountain uplift, and volcanism in the Cenozoic <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system and waxing and waning of the <span class="hlt">Antarctic</span> ice sheet beginning about earliest Oligocene time. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V11B4717I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V11B4717I"><span>Phreatomagmatic eruptions under the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet: potential hazard for ice sheet stability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iverson, N. A.; Dunbar, N. W.; Lieb-Lappen, R.; Kim, E. J.; Golden, E. J.; Obbard, R. W.</p> <p>2014-12-01</p> <p>Volcanic tephra layers have been seen in most ice cores in Antarctica. These tephra layers are deposited almost instantaneously across wide areas of ice sheets, creating horizons that can provide "pinning points" to adjust ice time scales that may otherwise be lacking detailed chronology. A combination of traditional particle morphology characterization by SEM with new non-destructive X-ray micro-computed tomography (Micro-CT) has been used to analyze selected coarse grained tephra in the <span class="hlt">West</span> Antarctica Ice Sheet (WAIS) Divide WDC06A ice core. Micro-CT has the ability to image particles as small as 50µm in length (15µm resolution), quantifying both particle shape and size. The WDC06A contains hundreds of dusty layers of which 36 have so far been identified as primary tephra layers. Two of these tephra layers have been characterized as phreatomagmatic eruptions based on SEM imagery and are blocky and platy in nature, with rare magmatic particles. These layers are strikingly different in composition from the typical phonolitic and trachytic tephra produced from <span class="hlt">West</span> <span class="hlt">Antarctic</span> volcanoes. These two layers are coarser in grain size, with many particles (including feldspar crystals) exceeding 100µm in length. One tephra layer found at 3149.138m deep in the ice core is a coarse ~1mm thick basanitic tephra layer with a WDC06-7 ice core age of 45,381±2000yrs. The second layer is a ~1.3 cm thick zoned trachyandesite to trachydacite tephra found at 2569.205m deep with an ice core age 22,470±835yrs. Micro-CT analysis shows that WDC06A-3149.138 has normal grading with the largest particles at the bottom of the sample (~160μm). WDC06A-2569.205 has a bimodal distribution of particles with large particles at the top and bottom of the layer. These large particles are more spherical in shape at the base and become more irregular and finer grained higher in the layer, likely showing changes in eruption dynamics. The distinct chemistry as well as the blocky and large grain size</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......342S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......342S"><span>Investigating <span class="hlt">Antarctic</span> ice sheet subglacial processes beneath the Whillans Ice Plain, <span class="hlt">West</span> Antarctica, using satellite altimetry and GPS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siegfried, Matthew Ross</p> <p></p> <p>The <span class="hlt">Antarctic</span> ice sheet has an extensive basal water system that lubricates the ice-bed interface and enables the fast flow of ice streams and outlet glaciers, which account for a majority of <span class="hlt">Antarctic</span> ice discharge to the ocean. In the past decade, observational evidence has suggested that the subglacial hydrology of Antarctica can be non-steady, changing on sub-decadal timescales, but the effect of dynamic hydrology on ice flow remains uncertain. The Whillans Ice Plain (WIP), at the confluence of the Whillans and Mercer ice streams, <span class="hlt">West</span> Antarctica, has been studied for over 50 years and has been identified as a region with extensive <span class="hlt">active</span> subglacial hydrology. In this dissertation, we develop and implement methods using a combination of ground-based Global Positioning System (GPS) data and satellite-based radar and laser altimetry to observe the surface expression of water movement beneath WIP, quantify the dynamic ice-flow response to an evolving basal water system, and investigate processes driven by the interaction of WIP with ocean tides that may impact subglacial water flow near the grounding line. We find that the coupled subglacial-ice stream system can respond rapidly to basal perturbations on sub-annual timescales and in ways that are not captured by simple models. We demonstrate that the location where subglacial water enters the ocean is a complex interface that requires significant improvement to our measurement precision to better understand important time-varying processes. We also apply our method for observing dynamic ice-surface height changes to the inventory of known subglacial lakes in Antarctica to extend our observational record and assess variability of the subglacial hydrologic system in different physical settings. Through this continent-wide analysis of subglacial lakes, we suggest that our current knowledge of the characteristic spatial and temporal scales of hydrologic variability is still limited by our observational capacity. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.2216P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.2216P"><span>Tectonic <span class="hlt">activity</span> evolution of the Scotia-<span class="hlt">Antarctic</span> Plate boundary from mass transport deposit analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pérez, Lara F.; Bohoyo, Fernando; Hernández-Molina, F. Javier; Casas, David; Galindo-Zaldívar, Jesús; Ruano, Patricia; Maldonado, Andrés.</p> <p>2016-04-01</p> <p>The spatial distribution and temporal occurrence of mass transport deposits (MTDs) in the sedimentary infill of basins and submerged banks near the Scotia-<span class="hlt">Antarctic</span> plate boundary allowed us to decode the evolution of the tectonic <span class="hlt">activity</span> of the relevant structures in the region from the Oligocene to present day. The 1020 MTDs identified in the available data set of multichannel seismic reflection profiles in the region are subdivided according to the geographic and chronological distributions of these features. Their spatial distribution reveals a preferential location along the eastern margins of the eastern basins. This reflects local deformation due to the evolution of the Scotia-<span class="hlt">Antarctic</span> transcurrent plate boundary and the impact of oceanic spreading along the East Scotia Ridge (ESR). The vertical distribution of the MTDs in the sedimentary record evidences intensified regional tectonic deformation from the middle Miocene to Quaternary. Intensified deformation started at about 15 Ma, when the ESR progressively replaces the <span class="hlt">West</span> Scotia Ridge (WSR) as the main oceanic spreading center in the Scotia Sea. Coevally with the WSR demise at about 6.5 Ma, increased spreading rates of the ESR and numerous MTDs were formed. The high frequency of MTDs during the Pliocene, mainly along the western basins, is also related to greater tectonic <span class="hlt">activity</span> due to uplift of the Shackleton Fracture Zone by tectonic inversion and extinction of the <span class="hlt">Antarctic</span>-Phoenix Ridge and involved changes at late Pliocene. The presence of MTDs in the southern Scotia Sea basins is a relevant indicator of the interplay between sedimentary instability and regional tectonics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26064564','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26064564"><span>Seasonal dynamics of megafauna on the deep <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula shelf in response to variable phytodetrital influx.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sumida, P Y G; Smith, C R; Bernardino, A F; Polito, P S; Vieira, D R</p> <p>2014-11-01</p> <p>The deep <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP) shelf is characterized by intense deposition of phytodetritus during spring/summer months, while very little food material reaches the seafloor during winter. The response of the shelf benthic megafauna to this highly variable food supply is still poorly understood. In order to characterize the deposition of phytodetritus and the megabenthic community response, we deployed a seafloor time-lapse camera at approximately 590 m depth on the mid WAP shelf <span class="hlt">west</span> of Anvers Island for 15 months. Seafloor photographs were taken at intervals of 12 or 24 h nearly continuously from 9 December 1999 (austral winter) to 20 March 2001 (summer) and analysed for phytodetritus deposition and megafaunal dynamics. Seafloor images indicated a marked seasonal arrival of greenish phytodetritus, with large interannual and seasonal variability in the coverage of depositing phytodetrital particles. The surface-deposit-feeding elasipod holothurians Protelpidia murrayi and Peniagone vignoni dominated the epibenthic megafauna throughout the year, frequently constituting more than 80% of the megafaunal abundance, attaining total densities of up to 2.4 individuals m(-2). Elasipod abundances were significantly higher in summer than winter. During summer periods of high phytodetrital flux, Pr. murrayi produced faecal casts at higher rates, indicating intensified population-level feeding <span class="hlt">activity</span>. In March-June 2000, faecal casts lasted longest, suggesting lower horizontal bioturbation <span class="hlt">activity</span> during autumn-winter. Our data indicate that the Pr. murrayi population increases its feeding rates in response to increasing amounts and/or lability of organic matter on the sediment surface. Assuming that this species feeds on the top millimetre of the sediment, we estimate that, during periods of high phytodetrital flux, the Pr. murrayi population reworks one square metre of sediment surface in approximately 287 days. We suggest that Pr. murrayi is an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4448839','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4448839"><span>Seasonal dynamics of megafauna on the deep <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula shelf in response to variable phytodetrital influx</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sumida, P. Y. G.; Smith, C. R.; Bernardino, A. F.; Polito, P. S.; Vieira, D. R.</p> <p>2014-01-01</p> <p>The deep <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP) shelf is characterized by intense deposition of phytodetritus during spring/summer months, while very little food material reaches the seafloor during winter. The response of the shelf benthic megafauna to this highly variable food supply is still poorly understood. In order to characterize the deposition of phytodetritus and the megabenthic community response, we deployed a seafloor time-lapse camera at approximately 590 m depth on the mid WAP shelf <span class="hlt">west</span> of Anvers Island for 15 months. Seafloor photographs were taken at intervals of 12 or 24 h nearly continuously from 9 December 1999 (austral winter) to 20 March 2001 (summer) and analysed for phytodetritus deposition and megafaunal dynamics. Seafloor images indicated a marked seasonal arrival of greenish phytodetritus, with large interannual and seasonal variability in the coverage of depositing phytodetrital particles. The surface-deposit-feeding elasipod holothurians Protelpidia murrayi and Peniagone vignoni dominated the epibenthic megafauna throughout the year, frequently constituting more than 80% of the megafaunal abundance, attaining total densities of up to 2.4 individuals m−2. Elasipod abundances were significantly higher in summer than winter. During summer periods of high phytodetrital flux, Pr. murrayi produced faecal casts at higher rates, indicating intensified population-level feeding <span class="hlt">activity</span>. In March–June 2000, faecal casts lasted longest, suggesting lower horizontal bioturbation <span class="hlt">activity</span> during autumn–winter. Our data indicate that the Pr. murrayi population increases its feeding rates in response to increasing amounts and/or lability of organic matter on the sediment surface. Assuming that this species feeds on the top millimetre of the sediment, we estimate that, during periods of high phytodetrital flux, the Pr. murrayi population reworks one square metre of sediment surface in approximately 287 days. We suggest that Pr. murrayi is an</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.......145R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.......145R"><span>Geochronological and geochemical assessment of Cenozoic volcanism from the Terror Rift region of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rilling, Sarah E.</p> <p></p> <p>The work presented in this dissertation explains results from three different methods to determine the relation between tectonism and rift-related volcanism in the Terror Rift region of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS). Alkaline lavas from seven submarine features, Beaufort Island and Franklin Islands, and several locations near Mt Melbourne were dated by 40Ar/39Ar geochronology and analyzed for elemental and isotopic chemical signatures. Each chapter addresses a different aspect of the hypothesis that the presence of volatiles, primarily H2O or CO2, in the magma source has led to anomalously high volumes of magmatism after rift-related decompressional melting rather than requiring an <span class="hlt">active</span> mantle plume source. Chapter 2 provides the temporal framework, illustrating that the sampled features range in age from 6.7 Ma to 89 ka, post-dating the main Miocene age phase of Terror Rift extension. Chapter 3 illustrates the traditional enriched elemental and isotopic chemical signatures to support the overall homogeneity of these lavas and previously analyzed areas of the WARS. This chapter also provides a new model for the generation of the Pb isotopic signatures consistent with a history of metasomatism in the magma source. Chapter 4 provides an entirely new chemical dataset for the WARS. The first platinum group element (PGE) abundances and extremely unradiogenic Os isotopic signatures of Cenozoic lavas from Antarctica provide the strongest evidence of melting contributions from a lithospheric mantle source. The combined results from these three studies consistently support the original hypothesis of this dissertation. New evidence suggests that WARS related lavas are not related to a mantle plume(s) as previously proposed. Instead, they are generated by passive, decompressional melting of a source, likely a combination of the asthenospheric and lithospheric mantle, which has undergone previous melting events and metasomatism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP43C2290K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP43C2290K"><span>Late Oligocene glacimarine sedimentation of the central Ross Sea and implications for the evolution of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kraus, C.; Mckay, R. M.; Naish, T.; Levy, R. H.; Kulhanek, D. K.</p> <p>2015-12-01</p> <p>Today the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) is grounded mostly below sea level, making it sensitive to oceanic temperature and circulation changes. However, recent reconstructions of the Cenozoic bedrock topographic evolution of <span class="hlt">West</span> Antarctica have suggested that the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) may have first formed as a terrestrial ice sheet at the Eocene-Oligocene boundary (33 Ma), when there was up to 20% more land area in <span class="hlt">West</span> Antarctica. At some point during the Oligocene or Miocene (23 - 5 Ma) vast areas of <span class="hlt">West</span> Antarctica became an over-deepened marine-based continental shelf, as is observed today. The evolution of the WAIS through this transition is largely unconstrained, but as atmospheric CO2 fluctuated between 600 and 200 ppm over the past 34 Ma, determining the development of a marine-based WAIS is critical in the context of understanding the sensitivity of ice sheet systems to environmental change. Our research re-examines the sediment cores recovered from the central Ross Sea, a principal drainage area of the WAIS, at Deep Sea Drilling Project Site 270 (77°26.48'S, 178°30.19'W). These cores contain a glacimarine sequence of late Oligocene age (28 - 23.1 Ma). Sedimentological (visual core description, facies, grain size analysis), geochemical (x-ray fluorescence), geophysical (seismic) techniques, and physical properties (magnetic susceptibility) are used to construct a sedimentation model of this sequence, in order to track the late Oligocene evolution of the WAIS. The late Oligocene warming (25 - 23 Ma) is examined in detail because proximal <span class="hlt">Antarctic</span> geological records of ice sheet extent, proxy environmental data, and atmospheric CO2 appear to be at odds with the composite δ18O record of global temperature and ice volume at this time. Moreover, our research provides insights into the sensitivity of marine-based ice sheets, and supports the hypothesis that they are unstable above a CO2 threshold of 400 ppm. Our preliminary results also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006615','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006615"><span>Diagnostic modeling of dimethylsulfide production in coastal water <span class="hlt">west</span> of the <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hermann, Maria; Najjar, Raymond G.; Neeley, Aimee R.; Vila-Costa, Maria; Dacey, John W. H.; DiTullio, Giacomo, R.; Kieber, David J.; Kiene, Ronald P.; Matrai, Patricia A.; Simo, Rafel; Vernet, Maria</p> <p>2012-01-01</p> <p>The rate of gross biological dimethylsulfide (DMS) production at two coastal sites <span class="hlt">west</span> of the <span class="hlt">Antarctic</span> Peninsula, off Anvers Island, near Palmer Station, was estimated using a diagnostic approach that combined field measurements from 1 January 2006 through 1 March 2006 and a one-dimensional physical model of ocean mixing. The average DMS production rate in the upper water column (0-60 m) was estimated to be 3.1 +/- 0.6 nM/d at station B (closer to shore) and 2.7 +/- 0.6 nM/d1 at station E (further from shore). The estimated DMS replacement time was on the order of 1 d at both stations. DMS production was greater in the mixed layer than it was below the mixed layer. The average DMS production normalized to chlorophyll was 0.5 +/- nM/d)/(mg cubic m) at station B and 0.7 +/- 0.2 (nM/d)/(mg/cubic m3) at station E. When the diagnosed production rates were normalized to the observed concentrations of total dimethylsulfoniopropionate (DMSPt, the biogenic precursor of DMS), we found a remarkable similarity between our estimates at stations B and E (0.06 +/- 0.02 and 0.04 +/- 0.01 (nM DMS / d1)/(nM DMSP), respectively) and the results obtained in a previous study from a contrasting biogeochemical environment in the North Atlantic subtropical gyre (0.047 =/- 0.006 and 0.087 +/- 0.014 (nM DMS d1)/(nM DMSP) in a cyclonic and anticyclonic eddy, respectively).We propose that gross biological DMS production normalized to DMSPt might be relatively independent of the biogeochemical environment, and place our average estimate at 0.06 +/- 0.01 (nM DMS / d)/(nM DMSPt). The significance of this finding is that it can provide a means to use DMSPt measurements to extrapolate gross biological DMS production, which is extremely difficult to measure experimentally under realistic in situ conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013QSRv...65...26A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013QSRv...65...26A"><span>Controls on interior <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet Elevations: inferences from geologic constraints and ice sheet modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ackert, Robert P.; Putnam, Aaron E.; Mukhopadhyay, Sujoy; Pollard, David; DeConto, Robert M.; Kurz, Mark D.; Borns, Harold W.</p> <p>2013-04-01</p> <p>Knowledge of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) response to past sea level and climate forcing is necessary to predict its response to warmer temperatures in the future. The timing and extent of past interior WAIS elevation changes provides insight to WAIS behavior and constraints for ice sheet models. Constraints prior to the Last Glacial Maximum (LGM) however, are rare. Surface exposure ages of glacial erratics near the WAIS divide at Mt. Waesche in Marie Byrd Land, and at the Ohio Range in the Transantarctic Mountains, range from ∼10 ka to >500 ka without a dependence on elevation. The probability distribution functions (PDF) of the exposure ages at both locations, are remarkably similar. During the last glaciation, maximum interior ice elevations as recorded by moraines and erratics were reached between 10 ka and 12 ka. However, most exposure ages are older than the LGM and cluster around ∼40 ka and ∼80 ka. The peak in the exposure age distributions at ∼40 ka includes ages of alpine moraine boulders at Mercer Ridge in the Ohio Range. Comparison of the PDF of exposures ages from the Ohio Range and Mt. Waesche with the temperature record from the Fuji Dome ice core indicates that the youngest peak in the exposure age distributions corresponds to the abrupt warming during the Last Glacial termination. A prominent peak in the Ohio Range PDF corresponds to the penultimate termination (stage 5e). During the intervening glacial period, there is not a consistent relationship between the peaks in the PDF at each location and temperature. A combined ice sheet/ice shelf model with forcing scaled to marine δ18O predicts that interior WAIS elevations near the ice divide have varied ∼300 m over the Last Glacial cycle. Peaks in the PDF correspond to model highstands over the last 200 ka. In the simulated elevation history, maximum ice elevations at Ohio Range (+100 m) and Mt. Waesche (+60 m) occur at ∼10 ka, in agreement with observations from these sites</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B41E0107L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B41E0107L"><span>Developmental History of an Intriguing Peat-Forming Community Along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loisel, J.; Yu, Z.; Beilman, D.; Kaiser, K.</p> <p>2014-12-01</p> <p>Permafrost peatbanks along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP) have become valuable high-resolution archives for late-Holocene climatic conditions recently. We recently observed and studied a few water-saturated peatlands that had formed in rocky depressions near Vernadsky Station and in mainland Antarctica (~ 65°S, 64°W). Remarkably, we seem to be the very first ones to analyze these systems for environmental reconstructions. The similarity between these peatlands and fens from the lower latitudes is striking, and the rarity of these systems along the WAP is intriguing. We present a high-resolution, multi-proxy record of ecosystem development and paleoenvironmental conditions for Rasmussen peatland. The ecosystem is ~100 m2 in size and is characterized by a shallow water table depth at 7 cm below the surface. Surface vegetation is dominated by Calliergon spp., a wet-adapted moss found along the WAP. The studied moss deposit is 50 cm thick and has a high organic matter content (> 90% dry weight). Plant macrofossil analysis reveals that the peatland was initially a wet Sanionia spp. carpet and that a sharp transition to Calliergon spp. occurred about half way through the deposit. A distinct layer of highly decomposed organic matter was observed from 32 to 40 cm and could indicate a period of slowed peat formation, potentially due to dry conditions (enhanced peat decay) or perennial snow cover (limited plant growth). Biochemical decomposition indicators such as carbohydrate yields, acid:aldehyde ratios of lignin phenols, and hydroxyproline yields are being determined to better understand the extent of peat decay that has occurred at this site throughout its development, particularly to further address the nature of the observed stratigraphic changes. Preliminary results indicate that carbohydrate yields of the bottom half of the core are about 1/3 smaller than those of the top half, indicating substantial carbon loss due to decomposition. Overall, these peatlands</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3806K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3806K"><span>Potential of the solid-Earth response for limiting long-term <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet retreat</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konrad, Hannes; Sasgen, Ingo; Pollard, David; Klemann, Volker</p> <p>2016-04-01</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.198..414A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.198..414A"><span>Upper mantle seismic anisotropy beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System and surrounding region from shear wave splitting analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Accardo, Natalie J.; Wiens, Douglas A.; Hernandez, Stephen; Aster, Richard C.; Nyblade, Andrew; Huerta, Audrey; Anandakrishnan, Sridhar; Wilson, Terry; Heeszel, David S.; Dalziel, Ian W. D.</p> <p>2014-07-01</p> <p>We constrain azimuthal anisotropy in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS and PKS phases recorded at 37 broad-band seismometres deployed by the POLENET/ANET project. We use an eigenvalue technique to linearize the rotated and shifted shear wave horizontal particle motions and determine the fast direction and delay time for each arrival. High-quality measurements are stacked to determine the best fitting splitting parameters for each station. Overall, fast anisotropic directions are oriented at large angles to the direction of <span class="hlt">Antarctic</span> absolute plate motion in both hotspot and no-net-rotation frameworks, showing that the anisotropy does not result from shear due to plate motion over the mantle. Further, the <span class="hlt">West</span> <span class="hlt">Antarctic</span> directions are substantially different from those of East Antarctica, indicating that anisotropy across the continent reflects multiple mantle regimes. We suggest that the observed anisotropy along the central Transantarctic Mountains (TAM) and adjacent <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS), one of the largest zones of extended continental crust on Earth, results from asthenospheric mantle strain associated with the final pulse of western WARS extension in the late Miocene. Strong and consistent anisotropy throughout the WARS indicate fast axes subparallel to the inferred extension direction, a result unlike reports from the East African rift system and rifts within the Basin and Range, which show much greater variation. We contend that ductile shearing rather than magmatic intrusion may have been the controlling mechanism for accumulation and retention of such coherent, widespread anisotropic fabric. Splitting beneath the Marie Byrd Land Dome (MBL) is weaker than that observed elsewhere within the WARS, but shows a consistent fast direction, possibly representative of anisotropy that has been `frozen-in' to remnant thicker lithosphere. Fast directions observed inland from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP12B..02J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP12B..02J"><span>The Role of the Tropics in Last Glacial Abrupt Climate Change from a <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, T. R.; White, J. W. C.; Steig, E. J.; Cuffey, K. M.; Vaughn, B. H.; Morris, V. A.; Vasileios, G.; Markle, B. R.; Schoenemann, S. W.</p> <p>2014-12-01</p> <p>Debate exists as to whether last glacial abrupt climate changes in Greenland, and associated changes in Antarctica, had a high-latitude or tropical trigger. An ultra high-resolution water isotope record from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet Divide (WAIS Divide) Ice Core Project has been developed with three key water isotope parameters that offer insight into this debate: δD, δ18O, and deuterium excess (dxs). δD and δ18O are a proxy for local temperature and regional atmospheric circulation, while dxs is primarily a proxy for sea surface temperature at the ice core's moisture source(s) (relative humidity and wind speed also play a role). We build on past studies that show <span class="hlt">West</span> <span class="hlt">Antarctic</span> climate is modulated by El Niño Southern Oscillation (ENSO) teleconnection mechanisms, which originate in the equatorial Pacific Ocean, to infer how past ENSO changes may have influenced abrupt climate change. Using frequency analysis of the water isotope data, we can reconstruct the amplitude of ENSO-scale climate oscillations in the 2-15 year range within temporal windows as low as 100 years. Our analysis uses a back diffusion model that estimates initial amplitudes before decay in the firn column. We combine δD, δ18O, and dxs frequency analysis to evaluate how climate variability at WAIS Divide is influenced by tropical climate forcing. Our results should ultimately offer insight into the role of the tropics in abrupt climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2609S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2609S"><span>Combined ice core and climate-model evidence for the collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet during Marine Isotope Stage 5e.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steig, Eric J.; Huybers, Kathleen; Singh, Hansi A.; Steiger, Nathan J.; Frierson, Dargan M. W.; Popp, Trevor; White, James W. C.</p> <p>2015-04-01</p> <p>It has been speculated that collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> plateau towards the Ross Sea and coastal Marie Byrd Land. The result is anomalous warming in some areas of the East <span class="hlt">Antarctic</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014E%26PSL.408...66H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014E%26PSL.408...66H"><span>Imaging the <span class="hlt">Antarctic</span> mantle using adaptively parameterized P-wave tomography: Evidence for heterogeneous structure beneath <span class="hlt">West</span> Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hansen, Samantha E.; Graw, Jordan H.; Kenyon, Lindsey M.; Nyblade, Andrew A.; Wiens, Douglas A.; Aster, Richard C.; Huerta, Audrey D.; Anandakrishnan, Sridhar; Wilson, Terry</p> <p>2014-12-01</p> <p>Previously developed continental-scale surface wave models for Antarctica provide only broad interpretations of the mantle structure, and the best resolved features in recent regional-scale seismic models are restricted above ∼300-400 km depth. We have developed the first continental-scale P-wave velocity model beneath Antarctica using an adaptively parameterized tomography approach that includes data from many new seismic networks. Our model shows considerable, previously unrecognized mantle heterogeneity, especially beneath <span class="hlt">West</span> Antarctica. A pronounced slow velocity anomaly extends between Ross Island and Victoria Land, further grid south than previous studies indicate. However, at least for mantle depths ≥∼200 km, this anomaly does not extend grid north along the Transantarctic Mountains (TAMs) and beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System. The boundary between these slow velocities and fast velocities underlying East Antarctica is ∼100-150 km beneath the front of the TAMs, consistent with flexural uplift models. The lateral extent of the low velocity anomaly is best explained by focused, rift-related decompression melting. In <span class="hlt">West</span> Antarctica, Marie Byrd Land is underlain by a deep (∼800 km) low velocity anomaly. Synthetic tests illustrate that the low velocities also extend laterally below the transition zone, consistent with a mantle plume ponded below the 660 km discontinuity. The slow anomalies beneath Ross Island and Marie Byrd Land are separate features, highlighting the heterogeneous upper mantle of <span class="hlt">West</span> Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014E%26PSL.394...99R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014E%26PSL.394...99R"><span>Neodymium and hafnium boundary contributions to seawater along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> continental margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rickli, Jörg; Gutjahr, Marcus; Vance, Derek; Fischer-Gödde, Mario; Hillenbrand, Claus-Dieter; Kuhn, Gerhard</p> <p>2014-05-01</p> <p>Neodymium and hafnium isotopes and elemental concentrations (Sm, Nd, Hf, Zr) have been measured in three water column profiles south of the <span class="hlt">Antarctic</span> Circumpolar Current in, and to the east of the Ross Sea, in conjunction with five bottom water samples from the Amundsen Sea Embayment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21307939','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21307939"><span>Holocene Southern Ocean surface temperature variability <span class="hlt">west</span> of the <span class="hlt">Antarctic</span> Peninsula.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shevenell, A E; Ingalls, A E; Domack, E W; Kelly, C</p> <p>2011-02-10</p> <p>The disintegration of ice shelves, reduced sea-ice and glacier extent, and shifting ecological zones observed around Antarctica highlight the impact of recent atmospheric and oceanic warming on the cryosphere. Observations and models suggest that oceanic and atmospheric temperature variations at Antarctica's margins affect global cryosphere stability, ocean circulation, sea levels and carbon cycling. In particular, recent climate changes on the <span class="hlt">Antarctic</span> Peninsula have been dramatic, yet the Holocene climate variability of this region is largely unknown, limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms. Here we show that surface ocean temperatures at the continental margin of the western <span class="hlt">Antarctic</span> Peninsula cooled by 3-4 °C over the past 12,000 years, tracking the Holocene decline of local (65° S) spring insolation. Our results, based on TEX(86) sea surface temperature (SST) proxy evidence from a marine sediment core, indicate the importance of regional summer duration as a driver of <span class="hlt">Antarctic</span> seasonal sea-ice fluctuations. On millennial timescales, abrupt SST fluctuations of 2-4 °C coincide with globally recognized climate variability. Similarities between our SSTs, Southern Hemisphere westerly wind reconstructions and El Niño/Southern Oscillation variability indicate that present climate teleconnections between the tropical Pacific Ocean and the western <span class="hlt">Antarctic</span> Peninsula strengthened late in the Holocene epoch. We conclude that during the Holocene, Southern Ocean temperatures at the western <span class="hlt">Antarctic</span> Peninsula margin were tied to changes in the position of the westerlies, which have a critical role in global carbon cycling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5214585','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5214585"><span>High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Smith, Craig R.; Lindsay, Dhugal J.; Bentlage, Bastian; Youngbluth, Marsh J.</p> <p>2017-01-01</p> <p>Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in <span class="hlt">Antarctic</span> Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436–725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or <span class="hlt">Antarctic</span>. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15–25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems. PMID</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24312442','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24312442"><span>Megafaunal communities in rapidly warming fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula: hotspots of abundance and beta diversity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grange, Laura J; Smith, Craig R</p> <p>2013-01-01</p> <p>Glacio-marine fjords occur widely at high latitudes and have been extensively studied in the Arctic, where heavy meltwater inputs and sedimentation yield low benthic faunal abundance and biodiversity in inner-middle fjords. Fjord benthic ecosystems remain poorly studied in the subpolar <span class="hlt">Antarctic</span>, including those in extensive fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP). Here we test ecosystem predictions from Arctic fjords on three subpolar, glacio-marine fjords along the WAP. With seafloor photographic surveys we evaluate benthic megafaunal abundance, community structure, and species diversity, as well as the abundance of demersal nekton and macroalgal detritus, in soft-sediment basins of Andvord, Flandres and Barilari Bays at depths of 436-725 m. We then contrast these fjord sites with three open shelf stations of similar depths. Contrary to Arctic predictions, WAP fjord basins exhibited 3 to 38-fold greater benthic megafaunal abundance than the open shelf, and local species diversity and trophic complexity remained high from outer to inner fjord basins. Furthermore, WAP fjords contained distinct species composition, substantially contributing to beta and gamma diversity at 400-700 m depths along the WAP. The abundance of demersal nekton and macroalgal detritus was also substantially higher in WAP fjords compared to the open shelf. We conclude that WAP fjords are important hotspots of benthic abundance and biodiversity as a consequence of weak meltwater influences, low sedimentation disturbance, and high, varied food inputs. We postulate that WAP fjords differ markedly from their Arctic counterparts because they are in earlier stages of climate warming, and that rapid warming along the WAP will increase meltwater and sediment inputs, deleteriously impacting these biodiversity hotspots. Because WAP fjords also provide important habitat and foraging areas for <span class="hlt">Antarctic</span> krill and baleen whales, there is an urgent need to develop better understanding of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28052087','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28052087"><span>High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grange, Laura J; Smith, Craig R; Lindsay, Dhugal J; Bentlage, Bastian; Youngbluth, Marsh J</p> <p>2017-01-01</p> <p>Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in <span class="hlt">Antarctic</span> Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436-725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or <span class="hlt">Antarctic</span>. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15-25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817399G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817399G"><span>Feedbacks between ice and ocean dynamics at the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Filchner-Ronne Ice Shelf in future global warming scenarios</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goeller, Sebastian; Timmermann, Ralph</p> <p>2016-04-01</p> <p>The ice flow at the margins of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet is moderated by large ice shelves. Their buttressing effect substantially controls the mass balance of the WAIS and thus its contribution to sea level rise. The stability of these ice shelves results from the balance of mass gain by accumulation and ice flow from the adjacent ice sheet and mass loss by calving and basal melting due to the ocean heat flux. Recent results of ocean circulation models indicate that warm circumpolar water of the Southern Ocean may override the submarine slope front of the <span class="hlt">Antarctic</span> Continent and boost basal ice shelf melting. In particular, ocean simulations for several of the IPCC's future climate scenarios demonstrate the redirection of a warm coastal current into the Filchner Trough and underneath the Filchner-Ronne Ice Shelf within the next decades. In this study, we couple the finite elements ocean circulation model FESOM and the three-dimensional thermomechanical ice flow model RIMBAY to investigate the complex interactions between ocean and ice dynamics at the Filchner-Ronne Ice Shelf. We focus on the impact of a changing ice shelf cavity on ocean dynamics as well as the feedback of the resulting sub-shelf melting rates on the ice shelf geometry and implications for the dynamics of the adjacent marine-based Westantarctic Ice Sheet. Our simulations reveal the high sensitivity of grounding line migration to ice-ocean interactions within the Filchner-Ronne Ice Shelf and emphasize the importance of coupled model studies for realistic assessments of the <span class="hlt">Antarctic</span> mass balance in future global warming scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP43C2302S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP43C2302S"><span>Influence of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet and its collapse on the wind and precipitation regimes of the Ross Embayment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seles, D.; Kowalewski, D. E.</p> <p>2015-12-01</p> <p>Marine Isotope Stage 31 (MIS 31) is a key analogue for current warming trends yet the extent of the East <span class="hlt">Antarctic</span> Ice Sheet (EAIS) and the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) during this interglacial remains unresolved. Inconsistencies persist between offshore records (suggesting the instability of WAIS) and McMurdo Dry Valley (MDV) terrestrial datasets (indicating long-term ice sheet stability). Here we use a high-resolution regional scale climate model (RegCM3_Polar) to reconstruct paleoclimate during MIS 31 (warm orbit, 400 ppm CO2) and assess changes in precipitation and winds (including katabatic) with WAIS present versus WAIS absent. The MIS 31 scenario with WAIS present resulted in minimal changes in wind magnitude compared with current climate conditions. With WAIS absent, the model predicts a decrease in coastal and highland monthly mean average wind velocities. The greatest rates of snowfall remain along the coast but shift towards higher latitudes with the interior continent remaining dry when WAIS is removed. Focusing on the Ross Embayment, this decreased monthly mean wind velocity and shift of winds to the east indicate a greater influence of offshore winds from the Ross Sea, enabling the increase of precipitation southward along the Transantarctic Mountains (TAM) (i.e. MDV). The apparent decrease of katabatic winds with no WAIS implies that offshore winds may be responsible for bringing the warmer, wetter air into the TAM. The change in wind and precipitation in the Ross Embayment and specifically the MDV highlights the impact of WAIS on <span class="hlt">Antarctic</span> climate and its subsequent influence on the mass balance of peripheral EAIS domes (i.e. Taylor Dome). Modeling suggests that if WAIS was absent during MIS 31, we would expect (1) greater accumulation at such domes and (2) MDV terrestrial records that reflect a wetter climate, and (3) weaker winds suggesting possibly lower ablation/erosion rates compared to if WAIS was present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3848936','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3848936"><span>Megafaunal Communities in Rapidly Warming Fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula: Hotspots of Abundance and Beta Diversity</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Grange, Laura J.; Smith, Craig R.</p> <p>2013-01-01</p> <p>Glacio-marine fjords occur widely at high latitudes and have been extensively studied in the Arctic, where heavy meltwater inputs and sedimentation yield low benthic faunal abundance and biodiversity in inner-middle fjords. Fjord benthic ecosystems remain poorly studied in the subpolar <span class="hlt">Antarctic</span>, including those in extensive fjords along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP). Here we test ecosystem predictions from Arctic fjords on three subpolar, glacio-marine fjords along the WAP. With seafloor photographic surveys we evaluate benthic megafaunal abundance, community structure, and species diversity, as well as the abundance of demersal nekton and macroalgal detritus, in soft-sediment basins of Andvord, Flandres and Barilari Bays at depths of 436–725 m. We then contrast these fjord sites with three open shelf stations of similar depths. Contrary to Arctic predictions, WAP fjord basins exhibited 3 to 38-fold greater benthic megafaunal abundance than the open shelf, and local species diversity and trophic complexity remained high from outer to inner fjord basins. Furthermore, WAP fjords contained distinct species composition, substantially contributing to beta and gamma diversity at 400–700 m depths along the WAP. The abundance of demersal nekton and macroalgal detritus was also substantially higher in WAP fjords compared to the open shelf. We conclude that WAP fjords are important hotspots of benthic abundance and biodiversity as a consequence of weak meltwater influences, low sedimentation disturbance, and high, varied food inputs. We postulate that WAP fjords differ markedly from their Arctic counterparts because they are in earlier stages of climate warming, and that rapid warming along the WAP will increase meltwater and sediment inputs, deleteriously impacting these biodiversity hotspots. Because WAP fjords also provide important habitat and foraging areas for <span class="hlt">Antarctic</span> krill and baleen whales, there is an urgent need to develop better understanding of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810062P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810062P"><span>Comparison of glacial isostasy contribution to the sea level changes during the Holocene in <span class="hlt">West</span> and East <span class="hlt">Antarctic</span> regions.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poleshchuk, Ksenia; Verkulich, Sergey; Pushina, Zina</p> <p>2016-04-01</p> <p>Antarctica as geographically completed and tectonically compound continent is an interesting object for study of glacial isostatic adjustment (GIA) and sea level changes in the Holocene. The analysis of relative sea level curves is one of the most indicative approaches for glacio-isostasy estimation. The present study focuses on two different regions of <span class="hlt">Antarctic</span> margin which sea-level changes are well researched. We compare our relative sea-level curves for Bunger Oasis (East Antarctica) and King George Island (<span class="hlt">West</span> Antarctica) that were obtained from new geomorphological, paleogeographical and micropaleontological data. The results showed notable difference: the maximum relative water altitude had occurred between 8 000 - 6 000 yr BP and had reached 12 m a. s. l. in the Bunger Oasis and 18-20 m a. s. l. in King George Island. Furthermore, the research of other <span class="hlt">Antarctic</span> regions revealed significant differences in sea-level altitudes. Following analysis of constructed curves and computative GIA models allow us to estimate the possible extent of glacial isostatic adjustment. Besides, this observation has indicated the importance of deglaciation rates and local tectonic features. The reported study was funded by RFBR according to the research project No. 16-35-00346 mol_a.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890017427','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890017427"><span><span class="hlt">Antarctic</span> Meteorite Location Map Series</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schutt, John (Editor); Fessler, Brian (Editor); Cassidy, William (Editor)</p> <p>1989-01-01</p> <p>Antarctica has been a prolific source of meteorites since meteorite concentrations were discovered in 1969. The <span class="hlt">Antarctic</span> Search For Meteorites (ANSMET) project has been <span class="hlt">active</span> over much of the Trans-<span class="hlt">Antarctic</span> Mountain Range. The first ANSMET expedition (a joint U.S.-Japanese effort) discovered what turned out to be a significant concentration of meteorites at the Allan Hills in Victoria Land. Later reconnaissance in this region resulted in the discovery of meteorite concentrations on icefields to the <span class="hlt">west</span> of the Allan Hills, at Reckling Moraine, and Elephant Moraine. <span class="hlt">Antarctic</span> meteorite location maps (reduced versions) of the Allan Hills main, near western, middle western, and far western icefields and the Elephant Moraine icefield are presented. Other <span class="hlt">Antarctic</span> meteorite location maps for the specimens found by the ANSMET project are being prepared.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...710325H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...710325H"><span>Evidence for the stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet divide for 1.4 million years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hein, Andrew S.; Woodward, John; Marrero, Shasta M.; Dunning, Stuart A.; Steig, Eric J.; Freeman, Stewart P. H. T.; Stuart, Finlay M.; Winter, Kate; Westoby, Matthew J.; Sugden, David E.</p> <p>2016-02-01</p> <p>Past fluctuations of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level. However, the configuration and stability of the ice sheet during past interglacial periods remains uncertain. Here we present geomorphological evidence and multiple cosmogenic nuclide data from the southern Ellsworth Mountains to suggest that the divide of the WAIS has fluctuated only modestly in location and thickness for at least the last 1.4 million years. Fluctuations during glacial-interglacial cycles appear superimposed on a long-term trajectory of ice-surface lowering relative to the mountains. This implies that as a minimum, a regional ice sheet centred on the Ellsworth-Whitmore uplands may have survived Pleistocene warm periods. If so, it constrains the WAIS contribution to global sea level rise during interglacials to about 3.3 m above present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4742792','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4742792"><span>Evidence for the stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet divide for 1.4 million years</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hein, Andrew S.; Woodward, John; Marrero, Shasta M.; Dunning, Stuart A.; Steig, Eric J.; Freeman, Stewart P. H. T.; Stuart, Finlay M.; Winter, Kate; Westoby, Matthew J.; Sugden, David E.</p> <p>2016-01-01</p> <p>Past fluctuations of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level. However, the configuration and stability of the ice sheet during past interglacial periods remains uncertain. Here we present geomorphological evidence and multiple cosmogenic nuclide data from the southern Ellsworth Mountains to suggest that the divide of the WAIS has fluctuated only modestly in location and thickness for at least the last 1.4 million years. Fluctuations during glacial–interglacial cycles appear superimposed on a long-term trajectory of ice-surface lowering relative to the mountains. This implies that as a minimum, a regional ice sheet centred on the Ellsworth-Whitmore uplands may have survived Pleistocene warm periods. If so, it constrains the WAIS contribution to global sea level rise during interglacials to about 3.3 m above present. PMID:26838462</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=122272','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=122272"><span>Glacial meltwater dynamics in coastal waters <span class="hlt">west</span> of the <span class="hlt">Antarctic</span> peninsula</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dierssen, Heidi M.; Smith, Raymond C.; Vernet, Maria</p> <p>2002-01-01</p> <p>The annual advance and retreat of sea ice has been considered a major physical determinant of spatial and temporal changes in the structure of the <span class="hlt">Antarctic</span> coastal marine ecosystem. However, the role of glacial meltwater on the hydrography of the <span class="hlt">Antarctic</span> Peninsula ecosystem has been largely ignored, and the resulting biological effects have only been considered within a few kilometers from shore. Through several lines of evidence collected in conjunction with the Palmer Station Long-Term Ecological Research Project, we show that the freshening and warming of the coastal surface water over the summer months is influenced not solely by sea ice melt, as suggested by the literature, but largely by the influx of glacial meltwater. Moreover, the seasonal variability in the amount and extent of the glacial meltwater plume plays a critical role in the functioning of the biota by influencing the physical dynamics of the water (e.g., water column stratification, nearshore turbidity). From nearly a decade of observations (1991–1999), the presence of surface meltwater is correlated not only to phytoplankton blooms nearshore, but spatially over 100 km offshore. The amount of meltwater will also have important secondary effects on the ecosystem by influencing the timing of sea ice formation. Because air temperatures are statistically increasing along the <span class="hlt">Antarctic</span> Peninsula region, the presence of glacial meltwater is likely to become more prevalent in these surface waters and continue to play an ever-increasing role in driving this fragile ecosystem. PMID:11830636</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20556653','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20556653"><span>Antimycobacterial <span class="hlt">activity</span> in vitro of pigments isolated from <span class="hlt">Antarctic</span> bacteria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mojib, Nazia; Philpott, Rachel; Huang, Jonathan P; Niederweis, Michael; Bej, Asim K</p> <p>2010-11-01</p> <p>In this study, we describe the antimycobacterial <span class="hlt">activity</span> of two pigments, violacein, a purple violet pigment from Janthinobacterium sp. Ant5-2 (J-PVP), and flexirubin, a yellow-orange pigment from Flavobacterium sp. Ant342 (F-YOP). These pigments were isolated from bacterial strains found in the land-locked freshwater lakes of Schirmacher Oasis, East Antarctica. The minimum inhibitory concentrations (MICs) of these pigments for avirulent and virulent mycobacteria were determined by the microplate Alamar Blue Assay (MABA) and Nitrate Reductase Assay (NRA). Results indicated that the MICs of J-PVP and F-YOP were 8.6 and 3.6 μg/ml for avirulent Mycobacterium smegmatis mc²155; 5 and 2.6 μg/ml for avirulent Mycobacterium tuberculosis mc²6230; and 34.4 and 10.8 μg/ml for virulent M. tuberculosis H₃₇Rv, respectively. J-PVP exhibited a ~15 times lower MIC for Mycobacterium sp. than previously reported for violacein pigment from Chromobacterium violaceum, while the antimycobacterial effect of F-YOP remains undocumented. Our results indicate these pigments isolated from <span class="hlt">Antarctic</span> bacteria might be valuable lead compounds for new antimycobacterial drugs used for chemotherapy of tuberculosis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.432..254K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.432..254K"><span>Potential of the solid-Earth response for limiting long-term <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet retreat in a warming climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konrad, Hannes; Sasgen, Ingo; Pollard, David; Klemann, Volker</p> <p>2015-12-01</p> <p>We employ a coupled model for ice-sheet dynamics and Maxwell viscoelastic solid-Earth dynamics, including a gravitationally consistent description of sea level. With this model, we study the influence of the solid Earth on the future evolution of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS). Starting from steady-state conditions close to the present-day configuration of the <span class="hlt">Antarctic</span> Ice Sheet, we apply different atmospheric and oceanic forcings and solid-Earth rheologies in order to analyse the retreat of the WAIS. Climate forcing is the primary control on the occurrence of WAIS collapse. For moderate climate forcing and weak solid-Earth rheologies, however, we find that the relative sea level (RSL) fall associated with the viscoelastic solid-Earth response due to unloading by WAIS retreat limits the retreat to the Amundsen Sea embayment on time scales of several millennia, whereas stiffer Earth structures yield a collapse under these conditions. Under stronger climate forcing, weak Earth structures associated with the <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system produce a delay of up to 5000 years in comparison to stiffer, <span class="hlt">Antarctic</span>-average solid-Earth rheologies. Furthermore, we find that sea-level rise from an assumed fast deglaciation of the Greenland Ice Sheet induces WAIS collapse in the presence of higher asthenosphere viscosities in cases when the climatic forcing is too weak to force WAIS collapse alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GGG....16.4344A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GGG....16.4344A"><span>Submarine and subaerial lavas in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System: Temporal record of shifting magma source components from the lithosphere and asthenosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aviado, Kimberly B.; Rilling-Hall, Sarah; Bryce, Julia G.; Mukasa, Samuel B.</p> <p>2015-12-01</p> <p>The petrogenesis of Cenozoic alkaline magmas in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS) remains controversial, with competing models highlighting the roles of decompression melting due to passive rifting, <span class="hlt">active</span> plume upwelling in the asthenosphere, and flux melting of a lithospheric mantle metasomatized by subduction. In this study, seamounts sampled in the Terror Rift region of the Ross Sea provide the first geochemical information from submarine lavas in the Ross Embayment in order to evaluate melting models. Together with subaerial samples from Franklin Island, Beaufort Island, and Mt. Melbourne in Northern Victoria Land (NVL), these Ross Sea lavas exhibit ocean island basalt (OIB)-like trace element signatures and isotopic affinities for the C or FOZO mantle endmember. Major-oxide compositions are consistent with the presence of multiple recycled lithologies in the mantle source region(s), including pyroxenite and volatile-rich lithologies such as amphibole-bearing, metasomatized peridotite. We interpret these observations as evidence that ongoing tectonomagmatic <span class="hlt">activity</span> in the WARS is facilitated by melting of subduction-modified mantle generated during 550-100 Ma subduction along the paleo-Pacific margin of Gondwana. Following ingrowth of radiogenic daughter isotopes in high-µ (U/Pb) domains, Cenozoic extension triggered decompression melting of easily fusible, hydrated metasomes. This multistage magma generation model attempts to reconcile geochemical observations with increasing geophysical evidence that the broad seismic low-velocity anomaly imaged beneath <span class="hlt">West</span> Antarctica and most of the Southern Ocean may be in part a compositional structure inherited from previous <span class="hlt">active</span> margin tectonics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27545202','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27545202"><span>Mid-Holocene pulse of thinning in the Weddell Sea sector of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hein, Andrew S; Marrero, Shasta M; Woodward, John; Dunning, Stuart A; Winter, Kate; Westoby, Matthew J; Freeman, Stewart P H T; Shanks, Richard P; Sugden, David E</p> <p>2016-08-22</p> <p>Establishing the trajectory of thinning of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet (WAIS) since the last glacial maximum (LGM) is important for addressing questions concerning ice sheet (in)stability and changes in global sea level. Here we present detailed geomorphological and cosmogenic nuclide data from the southern Ellsworth Mountains in the heart of the Weddell Sea embayment that suggest the ice sheet, nourished by increased snowfall until the early Holocene, was close to its LGM thickness at 10 ka. A pulse of rapid thinning caused the ice elevation to fall ∼400 m to the present level at 6.5-3.5 ka, and could have contributed 1.4-2 m to global sea-level rise. These results imply that the Weddell Sea sector of the WAIS contributed little to late-glacial pulses in sea-level rise but was involved in mid-Holocene rises. The stepped decline is argued to reflect marine downdraw triggered by grounding line retreat into Hercules Inlet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4996935','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4996935"><span>Mid-Holocene pulse of thinning in the Weddell Sea sector of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hein, Andrew S.; Marrero, Shasta M.; Woodward, John; Dunning, Stuart A.; Winter, Kate; Westoby, Matthew J.; Freeman, Stewart P. H. T.; Shanks, Richard P.; Sugden, David E.</p> <p>2016-01-01</p> <p>Establishing the trajectory of thinning of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet (WAIS) since the last glacial maximum (LGM) is important for addressing questions concerning ice sheet (in)stability and changes in global sea level. Here we present detailed geomorphological and cosmogenic nuclide data from the southern Ellsworth Mountains in the heart of the Weddell Sea embayment that suggest the ice sheet, nourished by increased snowfall until the early Holocene, was close to its LGM thickness at 10 ka. A pulse of rapid thinning caused the ice elevation to fall ∼400 m to the present level at 6.5–3.5 ka, and could have contributed 1.4–2 m to global sea-level rise. These results imply that the Weddell Sea sector of the WAIS contributed little to late-glacial pulses in sea-level rise but was involved in mid-Holocene rises. The stepped decline is argued to reflect marine downdraw triggered by grounding line retreat into Hercules Inlet. PMID:27545202</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP54A..04F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP54A..04F"><span>Evidence for a substantial <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet contribution to meltwater pulses and abrupt global sea level rise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fogwill, C. J.; Turney, C. S.; Golledge, N. R.; Etheridge, D. M.; Rubino, M.; Thornton, D.; Woodward, J.; Winter, K.; van Ommen, T. D.; Moy, A. D.; Curran, M. A.; Rootes, C.; Rivera, A.; Millman, H.</p> <p>2015-12-01</p> <p>During the last deglaciation (21,000 to 7,000years ago) global sea level rise was punctuated by several abrupt meltwater spikes triggered by the retreat of ice sheets and glaciers world-wide. However, the debate regarding the relative timing, geographical source and the physical mechanisms driving these rapid increases in sea level has catalyzed debate critical to predicting future sea level rise and climate. Here we present a unique record of <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet elevation change derived from the Patriot Hills blue ice area, located close to the modern day grounding line of the Institute Ice Stream in the Weddell Sea Embayment. Combined isotopic signatures and gas volume analysis from the ice allows us to develop a record of local ice sheet palaeo-altitude that is assessed against independent regional high-resolution ice sheet modeling studies, allowing us to demonstrate that past ice sheet elevations across this sector of the WSE were considerably higher than those suggested by current terrestrial reconstructions. We argue that ice in the WSE had a significant influence on both pre and post LGM sea level rise including MWP-1A (~14.6 ka) and during MWP-1B (11.7-11.6 ka), reconciling past sea level rise and demonstrating for the first time that this sector of the WAIS made a significant and direct contribution to post LGM sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...712511H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...712511H"><span>Mid-Holocene pulse of thinning in the Weddell Sea sector of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hein, Andrew S.; Marrero, Shasta M.; Woodward, John; Dunning, Stuart A.; Winter, Kate; Westoby, Matthew J.; Freeman, Stewart P. H. T.; Shanks, Richard P.; Sugden, David E.</p> <p>2016-08-01</p> <p>Establishing the trajectory of thinning of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet (WAIS) since the last glacial maximum (LGM) is important for addressing questions concerning ice sheet (in)stability and changes in global sea level. Here we present detailed geomorphological and cosmogenic nuclide data from the southern Ellsworth Mountains in the heart of the Weddell Sea embayment that suggest the ice sheet, nourished by increased snowfall until the early Holocene, was close to its LGM thickness at 10 ka. A pulse of rapid thinning caused the ice elevation to fall ~400 m to the present level at 6.5-3.5 ka, and could have contributed 1.4-2 m to global sea-level rise. These results imply that the Weddell Sea sector of the WAIS contributed little to late-glacial pulses in sea-level rise but was involved in mid-Holocene rises. The stepped decline is argued to reflect marine downdraw triggered by grounding line retreat into Hercules Inlet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23189611','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23189611"><span>The rapid disintegration of projections: the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet and the intergovernmental panel on climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>O'Reilly, Jessica; Oreskes, Naomi; Oppenheimer, Michael</p> <p>2012-10-01</p> <p>How and why did the scientific consensus about sea level rise due to the disintegration of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS), expressed in the third Intergovernmental Panel on Climate Change (IPCC) assessment, disintegrate on the road to the fourth? Using ethnographic interviews and analysis of IPCC documents, we trace the abrupt disintegration of the WAIS consensus. First, we provide a brief historical overview of scientific assessments of the WAIS. Second, we provide a detailed case study of the decision not to provide a WAIS prediction in the Fourth Assessment Report. Third, we discuss the implications of this outcome for the general issue of scientists and policymakers working in assessment organizations to make projections. IPCC authors were less certain about potential WAIS futures than in previous assessment reports in part because of new information, but also because of the outcome of cultural processes within the IPCC, including how people were selected for and worked together within their writing groups. It became too difficult for IPCC assessors to project the range of possible futures for WAIS due to shifts in scientific knowledge as well as in the institutions that facilitated the interpretations of this knowledge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1327844-century-scale-simulations-response-west-antarctic-ice-sheet-warming-climate','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1327844-century-scale-simulations-response-west-antarctic-ice-sheet-warming-climate"><span>Century-scale simulations of the response of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet to a warming climate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Cornford, S. L.; Martin, D. F.; Payne, A. J.; ...</p> <p>2015-03-23</p> <p>We use the BISICLES adaptive mesh ice sheet model to carry out one, two, and three century simulations of the fast-flowing ice streams of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet. Each of the simulations begins with a geometry and velocity close to present day observations, and evolves according to variation in meteoric ice accumulation, ice shelf melting, and mesh resolution. Future changes in accumulation and melt rates range from no change, through anomalies computed by atmosphere and ocean models driven by the E1 and A1B emissions scenarios, to spatially uniform melt rates anomalies that remove most of the ice shelves overmore » a few centuries. We find that variation in the resulting ice dynamics is dominated by the choice of initial conditions, ice shelf melt rate and mesh resolution, although ice accumulation affects the net change in volume above flotation to a similar degree. Given sufficient melt rates, we compute grounding line retreat over hundreds of kilometers in every major ice stream, but the ocean models do not predict such melt rates outside of the Amundsen Sea Embayment until after 2100. Sensitivity to mesh resolution is spurious, and we find that sub-kilometer resolution is needed along most regions of the grounding line to avoid systematic under-estimates of the retreat rate, although resolution requirements are more stringent in some regions – for example the Amundsen Sea Embayment – than others – such as the Möller and Institute ice streams.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCry....9.1579C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCry....9.1579C"><span>Century-scale simulations of the response of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet to a warming climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cornford, S. L.; Martin, D. F.; Payne, A. J.; Ng, E. G.; Le Brocq, A. M.; Gladstone, R. M.; Edwards, T. L.; Shannon, S. R.; Agosta, C.; van den Broeke, M. R.; Hellmer, H. H.; Krinner, G.; Ligtenberg, S. R. M.; Timmermann, R.; Vaughan, D. G.</p> <p>2015-08-01</p> <p>We use the BISICLES adaptive mesh ice sheet model to carry out one, two, and three century simulations of the fast-flowing ice streams of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet, deploying sub-kilometer resolution around the grounding line since coarser resolution results in substantial underestimation of the response. Each of the simulations begins with a geometry and velocity close to present-day observations, and evolves according to variation in meteoric ice accumulation rates and oceanic ice shelf melt rates. Future changes in accumulation and melt rates range from no change, through anomalies computed by atmosphere and ocean models driven by the E1 and A1B emissions scenarios, to spatially uniform melt rate anomalies that remove most of the ice shelves over a few centuries. We find that variation in the resulting ice dynamics is dominated by the choice of initial conditions and ice shelf melt rate and mesh resolution, although ice accumulation affects the net change in volume above flotation to a similar degree. Given sufficient melt rates, we compute grounding line retreat over hundreds of kilometers in every major ice stream, but the ocean models do not predict such melt rates outside of the Amundsen Sea Embayment until after 2100. Within the Amundsen Sea Embayment the largest single source of variability is the onset of sustained retreat in Thwaites Glacier, which can triple the rate of eustatic sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C24A..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C24A..03K"><span>Seasonal climate information preserved within <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice cores and its relation to large-scale atmospheric circulation and regional sea ice variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Küttel, M.; Steig, E. J.; Ding, Q.; Battisti, D. S.</p> <p>2010-12-01</p> <p>Recent evidence suggests that <span class="hlt">West</span> Antarctica has been warming since at least the 1950s. With the instrumental record being limited to the mid-20th century, indirect information from stable isotopes (δ18O and δD, hereafter collectively δ) preserved within ice cores have commonly been used to place this warming into a long term context. Here, using a large number of δ records obtained during the International Trans-<span class="hlt">Antarctic</span> Scientific Expedition (ITASE), past variations in <span class="hlt">West</span> <span class="hlt">Antarctic</span> δ are not only investigated over time but also in space. This study therefore provides an important complement to longer records from single locations as e.g. the currently being processed <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet (WAIS) Divide ice core. Although snow accumulation rates at the ITASE sites in <span class="hlt">West</span> Antarctica are variable, they are generally high enough to allow studies on sub-annual scale over the last 50-100 years. Here, we show that variations in δ in this region are strongly related to the state of the large-scale atmospheric circulation as well as sea ice variations in the adjacent Southern Ocean, with important seasonal changes. While a strong relationship to sea ice changes in the Ross and Amundsen Sea as well as to the atmospheric circulation offshore is found during austral fall (MAM) and winter (JJA), only modest correlations are found during spring (SON) and summer (DJF). Interestingly, the correlations with the atmospheric circulation in the latter two seasons have the strongest signal over the <span class="hlt">Antarctic</span> continent, but not offshore - an important difference to MAM and JJA. These seasonal changes are in good agreement with the seasonally varying predominant circulation: meridional with more frequent storms in the Amundsen Sea during MAM and JJA and more zonal and stable during SON and DJF. The relationship to regional temperature is similarly seasonally variable with highest correlations found during MAM and JJA. Notably, the circulation pattern found to be strongest</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGeo...12.6761H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGeo...12.6761H"><span>Two decades of inorganic carbon dynamics along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hauri, C.; Doney, S. C.; Takahashi, T.; Erickson, M.; Jiang, G.; Ducklow, H. W.</p> <p>2015-11-01</p> <p>We present 20 years of seawater inorganic carbon measurements collected along the western shelf and slope of the <span class="hlt">Antarctic</span> Peninsula. Water column observations from summertime cruises and seasonal surface underway pCO2 measurements provide unique insights into the spatial, seasonal, and interannual variability in this dynamic system. Discrete measurements from depths > 2000 m align well with World Ocean Circulation Experiment observations across the time series and underline the consistency of the data set. Surface total alkalinity and dissolved inorganic carbon data showed large spatial gradients, with a concomitant wide range of Ωarag (< 1 up to 3.9). This spatial variability was mainly driven by increasing influence of biological productivity towards the southern end of the sampling grid and meltwater input along the coast towards the northern end. Large inorganic carbon drawdown through biological production in summer caused high near-shore Ωarag despite glacial and sea-ice meltwater input. In support of previous studies, we observed Redfield behavior of regional C / N nutrient utilization, while the C / P (80.5 ± 2.5) and N / P (11.7 ± 0.3) molar ratios were significantly lower than the Redfield elemental stoichiometric values. Seasonal salinity-based predictions of Ωarag suggest that surface waters remained mostly supersaturated with regard to aragonite throughout the study. However, more than 20 % of the predictions for winters and springs between 1999 and 2013 resulted in Ωarag < 1.2. Such low levels of Ωarag may have implications for important organisms such as pteropods. Even though we did not detect any statistically significant long-term trends, the combination of on-going ocean acidification and freshwater input may soon induce more unfavorable conditions than the ecosystem experiences today.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51C0733G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51C0733G"><span>Where is the evidence of past collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gutowski, G.</p> <p>2015-12-01</p> <p>Sea level rise estimates from the Last Interglacial period suggest collapse of part of the <span class="hlt">Antarctic</span> ice sheet. However, there is no direct evidence of this from the ice sheet itself. Englacial layers in ice sheets, sampled directly by ice core drilling and indirectly by ice-penetrating radar, reveal a significant amount about glacial change over time and may contain a signature of the last ice sheet collapse. We hypothesize there is evidence of ice sheet instability where the observed englacial record deviates from that expected for a steady state WAIS simulated using ice sheet models. However, discrepancies between modeled steady state and observed englacial layer geometry are confounded by uncertainties in model boundary conditions, observed layer ages, and model parameters. To know where the signal of collapse may be best preserved, we must account for the affect of these uncertainties on layer geometry. We present several tests quantifying the sensitivity of simulated layer geometry to changes in model boundary conditions. We look to areas where englacial geometry has low sensitivity to uncertain boundary conditions to provide the largest signal of ice sheet instability. Where simulated layer geometry is responding strongly to uncertain boundary conditions, we are unlikely to be able to discern a signal of past deglaciation. In the latter case, uncertainty in layer geometry may overwhelm the signal of past ice sheet collapse. We perform the simulations using the Variational Glacier Simulator (VarGlaS), an ice sheet model with the capacity to model the age of englacial isochrones (Figure 1). We use the latest boundary conditions for geothermal flux, basal topography, and surface mass balance to simulate the steady state behavior of englacial layers in the Thwaites Glacier catchment and the Marie Byrd Land dome. Ensembles of model runs sample the uncertainty in each of the boundary conditions, creating a distribution of simulated englacial layers which accounts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713239G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713239G"><span>The response of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet to ocean warming beneath the Filchner Ronne Ice Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goeller, Sebastian; Timmermann, Ralph; Thoma, Malte</p> <p>2015-04-01</p> <p>The ice flow at the margins of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) is moderated by large ice shelves. Their buttressing effect substantially controls the mass balance of the WAIS and thus its contribution to sea level rise. The stability of these ice shelves results from the balance of mass gain by accumulation and ice flow from the adjacent ice sheet and mass loss by calving and basal melting due to the ocean heat flux. Recent results of ocean circulation models indicate that warm circumpolar water of the Southern Ocean may override the submarine slope front of the <span class="hlt">Antarctic</span> Continent and boost basal ice shelf melting. In particular, ocean simulations for several of the IPCC's future climate scenarios demonstrate the redirection of a warm coastal current into the Filchner Trough and underneath the Filchner-Ronne Ice Shelf (FRIS) within the next decades. In this study, we couple the finite elements ocean circulation model FESOM and the three-dimensional thermomechanical ice flow model RIMBAY to investigate the sensitivity of the ice dynamics within the entire FRIS catchment to simulated future basal shelf melt rates. Our simulations indicate a high sensitivity of the ice dynamics for the Möller and the Institute Ice Stream but only very little response of other ice streams like Rutford, Foundation and Recovery Ice Stream to enhanced basal shelf melting. The grounding line between the Möller and Institute Ice Streams is located on a submarine ridge in front of a deep trough further inland. In this area, basal shelf melting causes a local thinning of the FRIS. The consequent initial retreat of the grounding line continues once it reaches the adjacent reverse-sloped bedrock. We state, that a possible 'point of no return' for a vast grounding line retreat along this steep reverse bedrock slope might have been crossed already even for simulated present-day melt rates, indicating that the WAIS is currently not in equlibrium. Furthermore, our simulations show an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23440504','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23440504"><span>Life form and water source interact to determine <span class="hlt">active</span> time and environment in cryptogams: an example from the maritime <span class="hlt">Antarctic</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schlensog, Mark; Green, T G Allan; Schroeter, Burkhard</p> <p>2013-09-01</p> <p>Antarctica, with its almost pristine conditions and relatively simple vegetation, offers excellent opportunities to investigate the influence of environmental factors on species performance, such information being crucial if the effects of possible climate change are to be understood. <span class="hlt">Antarctic</span> vegetation is mainly cryptogamic. Cryptogams are poikilohydric and are only metabolically and photosynthetically <span class="hlt">active</span> when hydrated. <span class="hlt">Activity</span> patterns of the main life forms present, bryophytes (10 species, ecto- and endohydric), lichens (5 species) and phanerogams (2 species), were monitored for 21 days using chlorophyll a fluorescence as an indicator of metabolic <span class="hlt">activity</span> and, therefore, of water regime at a mesic (hydration by meltwater) and a xeric (hydration by precipitation) site on Léonie Island/<span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (67°36'S). Length of <span class="hlt">activity</span> depended mainly on site and form of hydration. Plants at the mesic site that were hydrated by meltwater were <span class="hlt">active</span> for long periods, up to 100 % of the measurement period, whilst <span class="hlt">activity</span> was much shorter at the xeric site where hydration was entirely by precipitation. There were also differences due to life form, with phanerogams and mesic bryophytes being most <span class="hlt">active</span> and lichens generally much less so. The length of the <span class="hlt">active</span> period for lichens was longer than in continental Antarctica but shorter than in the more northern <span class="hlt">Antarctic</span> Peninsula. Light intensity when hydrated was positively related to the length of the <span class="hlt">active</span> period. High <span class="hlt">activity</span> species were strongly coupled to the incident light whilst low <span class="hlt">activity</span> species were <span class="hlt">active</span> under lower light levels and essentially uncoupled from incident light. Temperatures were little different between sites and also almost identical to temperatures, when <span class="hlt">active</span>, for lichens in continental and peninsular Antarctica. Gradients in vegetation cover and growth rates across Antarctica are, therefore, not likely to be due to differences in temperature but more likely to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55..523D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55..523D"><span>Pelagic fishes in the Marguerite Bay region of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula continental shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Donnelly, Joseph; Torres, Joseph J.</p> <p>2008-02-01</p> <p>Pelagic fishes in the Marguerite Bay region of the western <span class="hlt">Antarctic</span> Peninsula (WAP) continental margin were sampled using a 10-m 2 MOCNESS as part of the Southern Ocean Global Ocean Ecosystems Dynamics (SO GLOBEC) program. Sixty-two tows were completed during the course of four cruises conducted during the austral fall and winter, 22 each during the austral fall, and 9 each during the austral winter. Six thousand and sixty individuals of 34 species representing 13 families were collected in the fall, while 672 individuals of 22 species from 10 families were collected in the winter. Nearly all of the notothenioid specimens collected (families Artedraconidae, Bathydraconidae, Channichthyidae, and Nototheniidae) were either larvae or young juveniles (0-2 years). Conversely, except for the paralepidid Notolepis coatsi and the occasional juveniles of the bathylagid Bathylagus antarcticus, the gonostomatid Cyclothone kobayashii, or the myctophid Electrona antarctica, the non-notothenioid specimens collected were predominantly adults. In the fall, the nototheniids Pleuragramma antarcticum and Trematomus scotti, and the myctophid E. antarctica numerically dominated the overall assemblage, collectively accounting for 89.7% of the total catch. In the winter, E. antarctica, Cyclothone microdon, and B. antarcticus were the numerical dominants, each contributing 14-20% of the total. The pelagic fish community within the Marguerite Bay region of the WAP continental shelf is a variable mixture of mesopelagic and neritic fauna. At one extreme is an oceanic assemblage exhibiting high-diversity indices and characterized by the genera Electrona, Gymnoscopelus, Protomyctophum, Bathylagus, Cyclothone, and Notolepis. Minor components of this group include numerous less common mesopelagic genera (e.g., Paradiplospinus, Lampanyctus, Benthalbella, Borostomias) and the occasional larval/juvenile notothenioid. At the other extreme is a coastal assemblage with low-diversity indices dominated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5657215','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5657215"><span>Evidence of rapid Cenozoic uplift of the shoulder escarpment of the Cenozoic <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system and a speculation on possible climate forcing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Behrendt, J.C. ); Cooper, A. )</p> <p>1991-04-01</p> <p>The Cenzoic <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system, characterized by Cenozoic bimodal alkalic volcanic rocks, extends over a largely ice-covered area, from the Ross Sea nearly to the Bellingshausen Sea. It is bounded on one side by a spectacular 4-to 5-km-high rift-shoulder scarp (maximum bedrock relief 5 to 7 km) from northern Victoria Land-Queen Maud Mountains to the Ellsworth-Whitmore-Horlick Mountains. Jurassic tholeiites crop out with the late Cenozoic volcanic rocks along the section of the Transantarctic Mountains from northern Victoria Land to the Horlick Mountains. The Cenozoic rift shoulder diverges here from the Jurassic tholeiite trend, and the tholeiites are exposed discontinuously along the lower elevation (1-2 km) section of the Transantarctic Mountains to the Weddell Sea. Various lines of evidence, no one of which is independently conclusive, lead the authors (as others have also suggested) to interpret the following. The Transantarctic Mountains part of the rift shoulder (and probably the entire shoulder) has been rising since about 60 Ma, at episodic rates of {approximately}1 km/m.y., most recently since mid-Pliocene time, rather than continuously at the mean rate of 100m/m.y. Uplift rates vary along the scarp, which is cut by transverse faults. The authors speculate that this uplift may have climatically forced the advance of the <span class="hlt">Antarctic</span> ice sheet since the most recent warm period. They suggest a possible synergistic relation between episodic tectonism, mountain uplift, and volcanism in the Cenozoic <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system and waxing and waning of the <span class="hlt">Antarctic</span> ice sheet beginning about earliest Oligocene time.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.3995G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.3995G"><span>Subglacial hydrology indicates a major shift in dynamics of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ross Ice Streams within the next two centuries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goeller, S.; Helm, V.; Thoma, M.; Grosfeld, K.</p> <p>2015-07-01</p> <p>The mass export of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) is dominated by fast flowing ice streams. Understanding their dynamics is a key to estimate the future integrity of the WAIS and its contributions to global sea level rise. This study focuses on the Ross Ice Streams (RIS) at the Siple Coast. In this sector, observations reveal a high variability of ice stream pathways and velocities which is assumed to be driven by subglacial hydrology. We compute subglacial water pathways for the present-day ice sheet and verify this assumption by finding high correlations between areas of enhanced basal water flow and the locations of the RIS. Moreover, we reveal that the ice flow velocities of the individual ice streams are correlated with the sizes of the water catchment areas draining underneath. The future development of the subglacial hydraulic environment is estimated by applying ice surface elevation change rates observed by ICESat and CryoSat-2 to the present-day ice sheet geometry and thus assessing prognostic basal pressure conditions. Our simulations consistently indicate that a major hydraulic tributary of the Kamb and Whillans Ice Stream (KIS and WIS) will be redirected underneath the Bindschadler Ice Stream (BIS) within the next two centuries. The water catchment area feeding underneath the BIS is estimated to grow by about 50 % while the lower part of the stagnated KIS becomes increasingly separated from its upper hydraulic tributaries. We conclude, that this might be a continuation of the subglacial hydraulic processes which caused the past stagnation of the KIS. The simulated hydraulic rerouting is also capable to explain the observed deceleration of the WIS and indicates a possible future acceleration of the BIS accompanied by an increased ice drainage of the corresponding ice sheet interior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.T11A1232P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.T11A1232P"><span>Neogene-Quaternary Volcanic Alignments in the Transantarctic Mountains and <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System of Southern Victoria Land, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paulsen, T. S.; Wilson, T. J.</p> <p>2004-12-01</p> <p>Neogene-Quaternary volcanism in southern Victoria Land, Antarctica, produced the Erebus Volcanic Province, a suite of alkaline volcanic rocks that extend from the Transantarctic Mountains rift-flank uplift to offshore localities within the <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system. We are mapping volcanic vent patterns in the province to detect alignments indicative of stress/strain patterns during rift evolution. In the southern sector of the Erebus Volcanic Province in the Royal Society Range Block of the Transantarctic Mountains, mapping shows that elliptical scoria cones, fissures, dikes, and linear vent arrays define volcanic alignments that have a dominant NNE trend, with subsidiary WNW trends. Age data for the alignments suggest that this pattern persisted from 14.6 to 0.25 Ma. We are currently completing mapping along an east-<span class="hlt">west</span> transect crossing the rift margin, and results obtained so far within the rift region indicate a similar pattern of alignments. On the northern flank of Mount Morning, a large volcano just to the east of the Royal Society Range, elliptical scoria cones and linear vent arrays define volcanic alignments that have a dominant NE trend, with a subsidiary NNW trend. Available age data suggest that many of these cone alignments may be of Quaternary age. At Brown Peninsula, further east from the rift flank, cone alignments trend NNE and available ages range from 2 to 3 Ma. To the east of Brown Peninsula, cone alignments trend NW at Black Island, but are of uncertain age; age data on Black Island range from 11 to 3.4 Ma. At White Island, the farthest east into the rift, cone alignments trend NNE and available age data suggest volcanism as young as 0.2 Ma. Although some differences in cone alignment trends are apparent between the rift flank and the rift system across our transect, both regions appear to be dominated by NE trending alignments, which implies a WNW to NW minimum horizontal stress (Shmin) direction. This is oblique to the ENE Shmin Cape</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T13F..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T13F..08W"><span>The case for nearly continuous extension of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System, 105-25 Ma (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, D. S.; Luyendyk, B. P.</p> <p>2010-12-01</p> <p>It is a common perception that extension in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS) was a two-phase process, with a Cretaceous phase ending when the Campbell Plateau rifted from <span class="hlt">West</span> Antarctica (~80 Ma), and a mid-Cenozoic phase synchronous with sea floor spreading in the Adare trough (~45-25 Ma). Several lines of evidence indicate that significant extension probably occurred in the intervening 80-45 Ma interval. The strongest evidence comes from subsidence rates on the Central High and Coulman High structures in the central-western Ross Sea, where DSDP Site 270 and other areas with shallow basement have subsided 1 km or more since Oligocene time. With sediment load, these subsidence rates are reasonable for thermal subsidence resulting from extension with a stretching factor of about 2.0-2.5 at about 50-70 Ma, but are hard to reconcile with an extension age around 90 Ma. The seismic velocity structure of the WARS inferred from global surface-wave dispersion is similar to that of oceanic lithosphere of age 40-60 Ma [Ritzwoller et al., 2001 JGR]. Geometric relations of sea floor between Adare Trough and Iselen Bank, northwest Ross Sea, suggest sea floor spreading of about 130 km during early Cenozoic, before the Adare Trough spreading episode started. Numerous cooling ages in the Transantarctic Mountains in the range of 55-45 Ma [Fitzgerald, 1992 Tectonics; Miller et al., 2010 Tectonics] support the interpretation of significant extension prior to 45 Ma. Present crustal thickness of about 22 km near DSDP Site 270 [Trey et al., 1999 Tectonophysics] suggests a pre-extension crustal thickness exceeding 50 km. A simple overall interpretation follows that the WARS has a tectonic history similar to the Basin and Range of western North America: a thick-crust orogenic highland extended for many tens of million years. The main difference between the WARS and the Basin and Range is the post-tectonic cooling and subsidence in the WARS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4593H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4593H"><span><span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet retreat from Pine Island Bay during the Holocene: New insights into forcing mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hillenbrand, Claus-Dieter; Smith, James; Kuhn, Gerhard; Poole, Chris; Hodell, David; Elderfield, Harry; Kender, Sev; Williams, Mark; Peck, Victoria; Larter, Robert; Klages, Johann; Graham, Alastair; Forwick, Matthias; Gohl, Karsten</p> <p>2013-04-01</p> <p>The Amundsen Sea sector of the largely marine-based and therefore conditionally unstable <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) contains enough ice to raise global sea level by ca. 1.5 metres. At present, ice streams draining this sector into the Southern Ocean, especially glaciers flowing into Pine Island Bay in the eastern Amundsen Sea embayment, are undergoing considerable mass loss characterised by major thinning, flow acceleration and rapid grounding-line retreat. Sub-ice shelf melting by relatively warm Circumpolar Deep Water (CDW) upwelling onto the continental shelf is held responsible for these dynamical changes but atmospheric warming in <span class="hlt">West</span> Antarctica may also have contributed to them. In contrast to the modern situation, the long-term history of the Amundsen Sea sector and the mechanisms forcing its deglaciation during the Holocene are only poorly constrained. We will present new palaeoenvironmenal data obtained from marine sediment cores collected in Pine Island Bay. The cores targeted shallow sites on the inner continental shelf and successfully recovered sedimentary sequences bearing calcareous microfossils. Radiocarbon ages on these microfossils demonstrate that the grounding line of the WAIS retreated to within ~100 km of its modern position before ca. 10 kyr BP (thousand years before present), which is consistent with an early WAIS retreat from near-coastal locations in the western Amundsen Sea embayment. Currently, there is no evidence that the grounding line had retreated landward of its modern position during the Holocene. Therefore, the chronological constraints may imply that during the last 10 kyr any episodes of fast grounding-line retreat similar to those observed today were short-lived and rare. Preliminary geochemical data from benthic and planktonic foraminifera tests in the cores from Pine Island Bay reveals that intense CDW upwelling coincided with and may have forced the deglaciation of the inner continental shelf. Furthermore, we observe</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53C0785B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53C0785B"><span>A Prediction of Increase in Subglacial Volcanism Beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) as Future Deglaciation Caused by Ocean Circulation Proceeds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrendt, J. C.; LeMasurier, W. E.</p> <p>2015-12-01</p> <p>Many decades of aeromagnetic surveying (e.g. Behrendt, 1964; 2013; and others) over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice sheet (WAIS) have shown >1000 high amplitude, shallow source magnetic anomalies interpreted as as indicating subglacial volcanic centers of late Cenozoic age to presently <span class="hlt">active</span>. Similar anomalies exist over exposed volcanic rocks bordering the WAIS in places.Recent papers (e.g. Wouters et al., 2015; Paolo, et al.; 2015 and others) based on satellite altimetry have shown dramatic thinning and retreat of ice shelves, particularly those bordering the Amundsen and Bellingshausen Seas, caused by melting from circulation of warming sea water. Previous workers have shown that when ice shelves collapse, the ice streams previously dammed by them accelerate an order of magnitude higher velocity, and surface elevation decreases. GRACE satellite interpretations (e.g. Velicogna et al., and others) indicate mass loss of WAIS in recent years.The bed elevation beneath the WAIS deepens inland from the Amundsen and Bellingshausen coasts, although high relief volcanic topography is present in a number of areas beneath the ice.Crowley et a. (2015) have shown that glacial cycles may drive production of oceanic crust by lowering pressure in the mantle resulting in increased melting and magma production. Increased volcanism due to deglaciation in Iceland has apparently produced increased in volcanic <span class="hlt">activity</span> there. Deglaciation of the Norwegian continental shelf has resulted in faulting of the sea floor and similar faulting has been reported of the Ross Sea shelf following deglaciation there.I suggest here that as the WAIS collapses in the future resulting from climate change, an increase in volcanic <span class="hlt">activity</span> beneath the ice might be expected. This may provide a feedback mechanism for increase in ice melting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCC...6...71M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCC...6...71M"><span>Linear sea-level response to abrupt ocean warming of major <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mengel, M.; Feldmann, J.; Levermann, A.</p> <p>2016-01-01</p> <p>Antarctica's contribution to global sea-level rise has recently been increasing. Whether its ice discharge will become unstable and decouple from anthropogenic forcing or increase linearly with the warming of the surrounding ocean is of fundamental importance. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below <span class="hlt">West</span> Antarctica's Filchner-Ronne ice shelf within the next two centuries. The ice basin's retrograde bed slope would allow for an unstable ice-sheet retreat, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner-Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...814645S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...814645S"><span>Temporal controls on silicic acid utilisation along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swann, George E. A.; Pike, Jennifer; Leng, Melanie J.; Sloane, Hilary J.; Snelling, Andrea M.</p> <p>2017-03-01</p> <p>The impact of climatic change along the Antarctica Peninsula has been widely debated in light of atmospheric/oceanic warming and increases in glacial melt over the past half century. Particular concern exists over the impact of these changes on marine ecosystems, not only on primary producers but also on higher trophic levels. Here we present a record detailing of the historical controls on the biogeochemical cycling of silicic acid [Si(OH)4] on the <span class="hlt">west</span> Antarctica Peninsula margin, a region in which the modern phytoplankton environment is constrained by seasonal sea ice. We demonstrate that Si(OH)4 cycling through the Holocene alternates between being primarily regulated by sea ice or glacial discharge from the surrounding grounded ice sheet. With further climate-driven change and melting forecast for the twenty-first century, our findings document the potential for biogeochemical cycling and multi-trophic interactions along the peninsula to be increasingly regulated by glacial discharge, altering food-web interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860018355&hterms=team+working&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dteam%2Bworking','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860018355&hterms=team+working&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dteam%2Bworking"><span>Research <span class="hlt">activities</span> on <span class="hlt">Antarctic</span> middle atmosphere by JARE 25th team</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hirasawa, T.; Eiwasaka, Y. AFTANAKA, M. agfujii, r.0 typ; Eiwasaka, Y. AFTANAKA, M. agfujii, r.0 typ</p> <p>1985-01-01</p> <p>The <span class="hlt">Antarctic</span> Middle Atmosphere (AMA)-Japan research project was set about by the JARE (Japan <span class="hlt">Antarctic</span> Research Expedition) 23rd team in 1982, and since then the JARE-24th and JARE-25th teams have been continuing reseach on the <span class="hlt">Antarctic</span> Middle Atmosphere. Results gained by JARE-25th team members who are now working at Syowa Station (69.99 deg S, 39.35 deg E), Antarctica are presented. In their <span class="hlt">activities</span> satellite measurements (Exos-C) and rocket soundings are used. Three rockets of the S310 type were launched at Syowa Station (Geomagnetic Latitude = 69.9 deg S) for the purpose of directly observing the electron density, ionospheric temperature, auroral patterns and luminosity in situ. Vertical profiles of electron density and auroral emission 4278A measured by three rockets are compared.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........41F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........41F"><span>Physical properties of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) Divide deep core: Development, evolution, and interpretation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fegyveresi, John M.</p> <p></p> <p>The physical properties of the WAIS Divide deep ice core record meteorological conditions during and shortly after deposition, mean temperature during transformation to ice, deformation within the ice, and may retain information on past surface elevations. The WAIS Divide (WDC06A) core was recovered from <span class="hlt">West</span> Antarctica (79°28.058' S, 112°05.189' W, ˜1760 m elevation, ˜3450 m ice thickness) on the Ross Sea side of the ice-divide with the Amundsen Sea drainage. My observations of the core were supplemented by near-surface studies spanning five consecutive austral summer seasons (2008--2012). Near-surface processes including intense summertime solar heating produce distinct seasonal strata. Prominent "glazed" crusts form very near the surface during times of steep temperature gradients and subsequently develop polygonal cracks, allowing ventilation of deeper firn. The near-surface seasonal contrasts persist to, and beyond the bubble-trapping depth, where they have a weak effect on total trapped air. A new record of total air content also shows that impurities may affect this important parameter, complicating interpretation of past elevation changes. Paleoclimatic interpretation of the number-density of bubbles is extended successfully here through the "brittle ice" zone, providing a record of surface temperature spanning ˜5500 years. This new record reveals relatively stable values through the first half of the interval, with a very-slight warming early, followed by a slight cooling over the most recent two millennia. Bubbles were found to be preferentially elongated parallel to the basal planes of enclosing grains, with less overall elongation of bubbles in grains with lower resolved shear stresses on their basal planes, as expected if grain deformation occurs primarily on basal planes and proportional to the stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGP34A..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGP34A..04B"><span>Unique Aeromagnetic-radar Ice-sounding Survey over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet Allows Three Dimensional Definition of Sources of Magnetic Anomalies Caused by Subglacial Volcanic Sources at the Bed of the Ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrendt, J. C.; Casertz; Soar Teams</p> <p>2011-12-01</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) flows through the volcanically <span class="hlt">active</span> <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS). The aeromagnetic method has proven the most useful geophysical tool for studying subglacial volcanic rocks beneath the WAIS since early surveys in the 1950s. The Central <span class="hlt">West</span> Antarctica (CWA) aerogeophysical survey covering ~354,000 km2 (about the area of Nevada and California combined) over the WAIS, consisting of a 5-km line-spaced, orthogonal set of aeromagnetic, radar ice-sounding and aerogravity measurements, is a unique <span class="hlt">Antarctic</span> data set. This 1990-97 survey (CASERTZ and SOAR), still provides invaluable information on subglacial volcanic rocks, particularly when combined with widely spaced older aeromagnetic flight lines over a much greater area. These combined survey data indicate numerous high-amplitude (100->1000 nT), 5-50 km width, shallow-source, magnetic anomalies over a very extensive area (>1.2 x 106 km2) mostly resulting from subglacial volcanic eruptions. I interpreted the anomalies sampled in the CWA survey as defining ~1000 "volcanic centers" requiring high remanent normal magnetizations in the present field direction. About 400 of these anomaly sources (conservatively selected) are correlated with bed topography. The tops of >80% of these anomaly sources have <200 m relief at the bed of the WAIS. They appear modified by moving ice, requiring a younger age than the WAIS (~25 Ma). The 5 km by 5 km orthogonal flight line survey obviated aliasing of the magnetic and radar ice sounding data, because it is approximately equivalent to the flight elevation above the ice (1 km) surface plus the ice thickness (2-3 km); it reveals the magnetic anomalies and the tops of volcanic sources at its bed in three dimensions. Models (2 1/2 D) fit to a number of the magnetic anomalies, whose sources are at the bed of the ice sheet are constrained by topography measured by the radar ice sounding. Volcanoes in the WARS are <34 Ma, but at least four are <span class="hlt">active</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25636910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25636910"><span>Complete genome of Bacillus sp. Pc3 isolated from the <span class="hlt">Antarctic</span> seawater with antimicrobial <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guo, Wenbin; Cui, Pengfei; Chen, Xinhua</p> <p>2015-04-01</p> <p>Bacillus sp. Pc3 was isolated from the <span class="hlt">Antarctic</span> seawater with strong antifungal <span class="hlt">activity</span> against several plant pathogenic fungi. Here, we report the complete sequence of the 3.9-Mbp genome of this strain. The genome sequence may provide fundamental molecular information on elucidating the metabolic pathway of antimicrobial compounds in this strain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT.......148P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT.......148P"><span>Modeling the <span class="hlt">West</span> <span class="hlt">Antarctic</span> and Greenland ice sheets: New dynamic, thermodynamic, and isostatic insights</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parizek, Byron R.</p> <p></p> <p>Numerical simulations indicate that the apparent long-term persistence and short-term variability of the Ross ice streams in <span class="hlt">West</span> Antarctica are tied to regional thermal conditions and local basal lubrication. Modelling results suggest that the flux of latent heat in a throughgoing hydrologic system fed by melt beneath thick inland ice maintains the lubrication of the ice streams despite their tendency to freeze to the bed, and would allow additional thinning and grounding-line retreat. However, the efficiency of basal water distribution may be a constraint on the system. Because local thermal deficits promote basal freeze-on (especially on topographic highs), observed short-term variability is likely to persist. Furthermore, simulations indicate that the ice streams have experienced only small deglacial thickness changes and are thinning more rapidly than their beds are rising isostatically. Thickness changes of O (100)m are modelled at the modern grounding line through the last glacial cycle. Coupled ice and bedrock models indicate isostatic rebound is raising the ice sheet at the modern grounding line faster than the rising sea level is submerging it. While, in and of itself, this could potentially lead to a grounding-line re-advance, ice flow is modelled to respond to recent changes in temperature, accumulation rate, and basal processes more rapidly than it does to bedrock-elevation and/or sea-level fluctuations. Future projections of the Greenland ice sheet indicate a faster contribution to sea-level rise in a warming world than previously believed, based on numerical modelling using a parameterization of recent results showing surface-meltwater lubrication of Greenland ice flow (Zwally et al., 2002). Numerous simulations were conducted to test a wide range of parameter space linking surface melt with a new sliding law based on Zwally et al. data under different global warming scenarios. Comparisons to reconstructions generated with a traditional sliding</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18072250','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18072250"><span>Characterization of <span class="hlt">Antarctic</span> psychrotrophic bacteria with antibacterial <span class="hlt">activities</span> against terrestrial microorganisms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lo Giudice, Angelina; Bruni, Vivia; Michaud, Luigi</p> <p>2007-12-01</p> <p>Five-hundreds and eighty bacterial strains, isolated from various <span class="hlt">Antarctic</span> marine sources and locations, were screened for antimicrobial <span class="hlt">activity</span> against terrestrial microorganisms. Twenty-two <span class="hlt">Antarctic</span> isolates (3.8%), mainly retrieved from the water column at Terra Nova Bay (Ross Sea), expressed antagonistic <span class="hlt">activity</span> against one to three indicator organisms. Escherichia coli and Proteus mirabilis resulted as the more susceptible, followed by Micrococcus luteus and Bacillus subtilis. None of the isolates inhibited the growth of Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella enterica and the eukaryotic fungus Candida albicans. <span class="hlt">Active</span> <span class="hlt">Antarctic</span> isolates, identified by 16S rDNA sequencing and phenotypically characterized by classical methods, were phylogenetically affiliated to the Actinobacteria (16 strains) and the gamma-Proteobacteria (6 strains). Inhibition patterns, as well as phenotypic characteristics, highly vary for different isolates, even though they were affiliated to the same genus or closely related to the identical microorganism retrieved from the database, suggesting that these features were more likely strain-rather than species-specific.Results obtained from the present study confirm previous observations and highlight the potentiality of <span class="hlt">Antarctic</span> marine bacteria as novel source of antibacterial substances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9445471','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9445471"><span>Changes in the <span class="hlt">west</span> <span class="hlt">antarctic</span> ice sheet since 1963 from declassified satellite photography</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bindschadler; Vornberger</p> <p>1998-01-30</p> <p>Comparison of declassified satellite photography taken in 1963 with more recent satellite imagery reveals that large changes have occurred in the region where an <span class="hlt">active</span> ice stream enters the Ross Ice Shelf. Ice stream B has widened by 4 kilometers, at a rate much faster than suggested by models, and has decreased in speed by 50 percent. The ice ridge between ice streams B and C has eroded 14 kilometers. These changes, along with changes in the crevassing around Crary Ice Rise, imply that this region's velocity field shifted during this century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PEPI..141..167K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PEPI..141..167K"><span>Rayleigh-wave group velocity distribution in the <span class="hlt">Antarctic</span> region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kobayashi, Reiji; Zhao, Dapeng</p> <p>2004-03-01</p> <p>We determined 2D group velocity distribution of Rayleigh waves at periods of 20-150 s in the <span class="hlt">Antarctic</span> region using a tomographic inversion technique. The data are recorded by both permanent networks and temporary arrays. In East Antarctica the velocities are high at periods of 90-150 s, suggesting that the root of East Antarctica is very deep. The velocities in <span class="hlt">West</span> Antarctica are low at all periods, which may be related to the volcanic <span class="hlt">activity</span> and the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System. Low velocity anomalies appear at periods of 40-140 s along the Southeastern Indian Ridge and the western part of the Pacific <span class="hlt">Antarctic</span> Ridge. The velocities are only slightly low around the Atlantic Indian Ridge, Southwestern Indian Ridge, and the eastern part of the Pacific <span class="hlt">Antarctic</span> Ridge, where the spreading rates are small. Around two hotspots, the Mount Erebus and Balleny Islands, the velocity is low at periods of 50-150 s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23549284','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23549284"><span>Biological <span class="hlt">activities</span> of ethanolic extracts from deep-sea <span class="hlt">Antarctic</span> marine sponges.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Turk, Tom; Ambrožič Avguštin, Jerneja; Batista, Urška; Strugar, Gašper; Kosmina, Rok; Čivović, Sandra; Janussen, Dorte; Kauferstein, Silke; Mebs, Dietrich; Sepčić, Kristina</p> <p>2013-04-02</p> <p>We report on the screening of ethanolic extracts from 33 deep-sea <span class="hlt">Antarctic</span> marine sponges for different biological <span class="hlt">activities</span>. We monitored hemolysis, inhibition of acetylcholinesterase, cytotoxicity towards normal and transformed cells and growth inhibition of laboratory, commensal and clinically and ecologically relevant bacteria. The most prominent <span class="hlt">activities</span> were associated with the extracts from sponges belonging to the genus Latrunculia, which show all of these <span class="hlt">activities</span>. While most of these <span class="hlt">activities</span> are associated to already known secondary metabolites, the extremely strong acetylcholinesterase inhibitory potential appears to be related to a compound unknown to date. Extracts from Tetilla leptoderma, Bathydorus cf. spinosus, Xestospongia sp., Rossella sp., Rossella cf. racovitzae and Halichondria osculum were hemolytic, with the last two also showing moderate cytotoxic potential. The antibacterial tests showed significantly greater <span class="hlt">activities</span> of the extracts of these <span class="hlt">Antarctic</span> sponges towards ecologically relevant bacteria from sea water and from Arctic ice. This indicates their ecological relevance for inhibition of bacterial microfouling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3705393','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3705393"><span>Biological <span class="hlt">Activities</span> of Ethanolic Extracts from Deep-Sea <span class="hlt">Antarctic</span> Marine Sponges</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Turk, Tom; Ambrožič Avguštin, Jerneja; Batista, Urška; Strugar, Gašper; Kosmina, Rok; Čivović, Sandra; Janussen, Dorte; Kauferstein, Silke; Mebs, Dietrich; Sepčić, Kristina</p> <p>2013-01-01</p> <p>We report on the screening of ethanolic extracts from 33 deep-sea <span class="hlt">Antarctic</span> marine sponges for different biological <span class="hlt">activities</span>. We monitored hemolysis, inhibition of acetylcholinesterase, cytotoxicity towards normal and transformed cells and growth inhibition of laboratory, commensal and clinically and ecologically relevant bacteria. The most prominent <span class="hlt">activities</span> were associated with the extracts from sponges belonging to the genus Latrunculia, which show all of these <span class="hlt">activities</span>. While most of these <span class="hlt">activities</span> are associated to already known secondary metabolites, the extremely strong acetylcholinesterase inhibitory potential appears to be related to a compound unknown to date. Extracts from Tetilla leptoderma, Bathydorus cf. spinosus, Xestospongia sp., Rossella sp., Rossella cf. racovitzae and Halichondria osculum were hemolytic, with the last two also showing moderate cytotoxic potential. The antibacterial tests showed significantly greater <span class="hlt">activities</span> of the extracts of these <span class="hlt">Antarctic</span> sponges towards ecologically relevant bacteria from sea water and from Arctic ice. This indicates their ecological relevance for inhibition of bacterial microfouling. PMID:23549284</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7269K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7269K"><span>Revealing potential past collapses of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet - Upcoming drilling in the Amundsen Sea Embayment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuhn, Gerhard; Gohl, Karsten; Uenzelmann-Neben, Gabriele; Bickert, Torsten; Schulz, Michael; Larter, Robert D.; Hillenbrand, Claus-Dieter</p> <p>2014-05-01</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice-Sheet (WAIS) is likely to have been subject to very dynamic changes during its history as most of its base is grounded below modern sea-level, making it particularly sensitive to climate changes. Its collapse would result in global sea-level rise of 3-5 m. The reconstruction and quantification of possible partial or full collapses of the WAIS in the past can provide important constraints for ice-sheet models, used for projecting its future behaviour and resulting sea-level rise. Large uncertainties exist regarding the chronology, extent, rates as well as spatial and temporal variability of past advances and retreats of the WAIS across the continental shelves. By using the seafloor drilling device MeBo during an RV Polarstern cruise scheduled for early 2015, a series of sediment cores will be drilled on the Amundsen Sea Embayment (ASE) shelf, where seismic data show glacially-derived sequences covered by only a thin veneer of postglacial deposits in some areas. From analyses of seismic data, we infer that interglacial sediments can be sampled which may have been deposited under seasonally open water conditions and thus contain datable microfossil-bearing material. A shallow basin near the Pine Island Glacier front will be one of the prime targets for the drilling. The near-horizontal seismic reflection horizons may represent a sequence of continuously deposited, mainly terrigenous material, including ice-rafted debris, meltwater deposits and hemipelagic sediments deposited rapidly during the Holocene or a series of unconformities caused by erosion resulting from grounding line oscillations through many glacial cycles. Subglacial bedforms imaged in multibeam bathymetric data indicate fast glacial flow over some shelf areas of the ASE, where seismic profiles show acoustic basement near the seafloor. It is unknown, whether fast ice-flow in these areas was facilitated by water-lubricated sliding over bedrock or presence of a thin layer of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.C11B..06A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.C11B..06A"><span>Extent of <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet During the LGM, Timing of Retreat and Potential Contribution to MWP Ia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, J.; Lowe, A.; Mosola, A.; Oakes, L.</p> <p>2005-12-01</p> <p>An extensive marine geological data set has been acquired from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> continental shelf, including all of the major troughs that occur seaward of major drainage outlets. Swath bathymetry records show a progression of geomorphic features on the continental shelf that range from subglacial meltwater features to drumlin fields to mega-scale glacial lineations in an offshore direction. There is evidence for catastrophic outbursts of meltwater beneath the ice sheet within Pine Island Bay and Marguerite Bay. Mega-scale glacial lineations comprised of soft, deformation till indicate that the ancestral WAIS was drained through ice streams that, in the case of the eastern Ross Sea, extended over a thousand kilometers to the continental shelf edge. Hence, over-extension of ice streams and subglacial meltwater outbursts may have contributed to ice sheet instability and retreat. The largest drainage system occurs in the eastern Ross Sea and southern Weddell Sea. Severe sea ice conditions have limited data acquisition in the southern Weddell Sea, but a detailed study has been conducted in the eastern Ross Sea. There, the ice sheet appears to have retreated rapidly from the continental shelf, but the distribution of grounding zone wedges suggests a somewhat diachronous retreat for different ice streams. Our efforts to constrain the timing of ice sheet retreat from the shelf focused on dating the oldest glaciomarine sediments resting on till. Unfortunately, no carbonate was recovered from cores in the eastern Ross Sea, so the timing of retreat of this portion of the ice sheet is based on TOC dates, and uncertainty about reservoir effects limits our ability to constrain the retreat history. What is implied by the combined data is that the ice sheet appears to have retreated rapidly from the shelf soon after the LGM. In western Marie Byrd Land, the ice sheet retreated from the continental shelf prior to 13 Ka. In Pine Island Bay, retreat occurred in two stages. The ice</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP51D1160B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP51D1160B"><span>Constraints on the last deglaciation of the Ross Sea Sector of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) from 10Be dating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bill, N. S.; Clark, P. U.; Kurz, M. D.; Marcott, S. A.; Caffee, M. W.</p> <p>2014-12-01</p> <p>We present new 10Be surface exposure ages from glacial erratic boulders from several locations in McMurdo Sound in order to constrain the deglacial history of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet. Previous model and field data indicate that the present day Ross Ice Shelf was a grounded ice sheet, with the grounding line extending to near the continental shelf edge during the Last Glacial Maximum (LGM). However, the timing and rate of the last deglaciation of the Ross Sea Sector of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet remain uncertain. We sampled granitic and basaltic erratic boulders for dating with the cosmogenic nuclides 10Be and 3He; in situ 14C dating will be used to assess complex burial histories. The 10Be ages on erratics near or at the upper limit of Ross Sea Drift that do not appear to have inheritance range from 17 to 26 ka. 10Be ages from erratics below the limit of the (LGM) Ross Sea Drift suggest final deglaciation by ~11 ka. New 10Be ages from more highly weathered glacial deposits above the Ross Sea drift near Blue Glacier suggest an age range of 141 to 171 ka.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25232675','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25232675"><span>Antimicrobial <span class="hlt">activity</span> of <span class="hlt">Antarctic</span> bryozoans: an ecological perspective with potential for clinical applications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Figuerola, Blanca; Sala-Comorera, Laura; Angulo-Preckler, Carlos; Vázquez, Jennifer; Jesús Montes, M; García-Aljaro, Cristina; Mercadé, Elena; Blanch, Anicet R; Avila, Conxita</p> <p>2014-10-01</p> <p>The antimicrobial <span class="hlt">activity</span> of <span class="hlt">Antarctic</span> bryozoans and the ecological functions of the chemical compounds involved remain largely unknown. To determine the significant ecological and applied antimicrobial effects, 16 ether and 16 butanol extracts obtained from 13 different bryozoan species were tested against six <span class="hlt">Antarctic</span> (including Psychrobacter luti, Shewanella livingstonensis and 4 new isolated strains) and two bacterial strains from culture collections (Escherichia coli and Bacillus cereus). Results from the bioassays reveal that all ether extracts exhibited antimicrobial <span class="hlt">activity</span> against some bacteria. Only one butanol extract produced inhibition, indicating that antimicrobial compounds are mainly lipophilic. Ether extracts of the genus Camptoplites inhibited the majority of bacterial strains, thus indicating a broad-spectrum of antimicrobial <span class="hlt">activity</span>. Moreover, most ether extracts presented <span class="hlt">activities</span> against bacterial strains from culture collections, suggesting the potential use of these extracts as antimicrobial drugs against pathogenic bacteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25680110','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25680110"><span>Antifouling <span class="hlt">activity</span> in some benthic <span class="hlt">Antarctic</span> invertebrates by "in situ" experiments at Deception Island, Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Angulo-Preckler, Carlos; Cid, Cristina; Oliva, Francesc; Avila, Conxita</p> <p>2015-04-01</p> <p>Competition for space is a remarkable ecological force, comparable to predation, producing a strong selective pressure on benthic invertebrates. Some invertebrates, thus, possess antimicrobial compounds to reduce surface bacterial growth. Antimicrobial inhibition is the first step in avoiding being overgrown by other organisms, which may have a negative impact in feeding, respiration, reproduction … The in situ inhibition of bacterial biofilm was used here as an indicator of antifouling <span class="hlt">activity</span> by testing hydrophilic extracts of twelve <span class="hlt">Antarctic</span> invertebrates. Using two different approaches (genetics and confocal techniques) different levels of <span class="hlt">activity</span> were found in the tested organisms. In fact, differences within body parts of the studied organisms were determined, in agreement with the Optimal Defense Theory. Eight out of 15 extracts tested had negative effects on fouling after 28 days submerged in <span class="hlt">Antarctic</span> waters. Thus, although chemical defenses may be quite species-specific in their ecological roles, these results suggest that different chemical strategies exist to deal with space competition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUSM.C42A..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUSM.C42A..02B"><span>Coring to the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet bed with a new Deep Ice Sheet Coring (DISC) drill</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bentley, C. R.; Taylor, K. C.; Shturmakov, A. J.; Mason, W. P.; Emmel, G. R.; Lebar, D. A.</p> <p>2005-05-01</p> <p>As a contribution to IPY 2007-2008, the U.S. ice core research community, supported by the National Science Foundation, plans to core through the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet (WAIS) at the ice-flow divide between the Ross Sea and Amundsen Sea drainage systems. The aim is to develop a unique series of interrelated climatic, ice-dynamic, and biologic records focused on understanding interactions among global earth systems. There will be approximately 15 separate but synergistic projects to analyze the ice and interpret the records. The most significant expected outcome of the WAIS Divide program will be climate records for the last ~40,000 years with an annually resolved chronology (through layer counting), comparable to the records from central Greenland. The data will also extend, at lower temporal resolution, to approximately 100,000 BP. These records will permit comparison of environmental conditions between the northern and southern hemispheres, and study of greenhouse gas concentrations in the paleoatmosphere, with unprecedented detail. To accomplish the coring, an innovative new Deep Ice Sheet Coring (DISC) drill is being built at the University of Wisconsin. The modular design of the bore-hole assembly (sonde) provides high flexibility for producing a 122 mm diameter ice core to depths of 4,000 m with maximum core lengths of 4 m. The DISC drill has a rotating outer barrel that can be used with or without an inner barrel designed to improve core recovery in brittle ice. Separate and independent motors for the drill and pump allow cutter speeds from 0 to 150 rpm and pump rates from 0 to 140 gpm. The high pumping rate should alleviate problems drilling in warm ice near the bed; it also helps make tripping speeds several times faster than with the old US drill. Other innovations include vibration and acoustic sensors for monitoring the drilling process, a segmented core barrel to avoid the formerly persistent problem of bent core barrels, and a high-speed data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C11B0677P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C11B0677P"><span>Control of the width of <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice streams by internal melting in the ice sheet near the margins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perol, T.; Rice, J. R.</p> <p>2011-12-01</p> <p>Could the 40 to 80 km widths of <span class="hlt">West</span> <span class="hlt">Antarctic</span> (Ross Shelf) ice streams be controlled by onset of melting within the ice sheet at the stream margins? The streams are driven by gravity which is resisted by basal drag, inferred to be small, and by shear stress at the lateral margins, assuming longitudinal stress gradients are unimportant [Whilans & van der Veen, JG'93]. Lateral shear stress in the sheet scales with the difference between gravitational stress and basal drag, and increases linearly with the lateral distance X from the center of a stream. With increasing X, that lateral shear stress times the creep strain rate it induces becomes a significant heat source within the ice sheet (proportional to X4 using Glen's law), and must ultimately induce internal melting. We study this possibility using data for a set of 5 ice stream profiles (A, WNar, C, D, E) of Joughin et al. [JGR'02]. They used measured lateral shear strain rates at the margins, and a depth-averaged values of the Glen's law creep parameter, based on a 1-D conduction-advection heat transfer analysis, without internal heating, to estimate the lateral drag. We find that when we incorporate the product of their drag stress and strain rate as a source in a conductive heat transfer model, the predicted margin temperatures are in excess of melting over some depth range for all five profiles. This supports the possibility that internal melting within the ice sheet is indeed related to why the margins are where they are. Next, we reformulated the 1-D vertical heat flux problem allowing some lower depth range of the of ice sheet to be partially melted ice at the melting temperature, with the rest of the sheet frozen and undergoing conductive heat transfer. The sheet was subjected to a uniform lateral shear rate, allowing the Glen's law parameter and local shear stress to be different for the two zones. The predicted fraction of the thickness that is molten, if any, depends on the lateral shear strain rate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6784H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6784H"><span>The German <span class="hlt">Antarctic</span> Receiving Station GARS O'Higgins: Remote sensing as core for a broader range of <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Höppner, Kathrin; Diedrich, Erhard; Klügel, Thomas; Metzig, Robert</p> <p>2014-05-01</p> <p>Since 1991 the German <span class="hlt">Antarctic</span> Station GARS O'Higgins is operated by the German Aerospace Center (DLR) in cooperation with the Federal Agency for Cartography and Geodesy (BKG). The station is located about 30 km <span class="hlt">west</span> of the northern tip of the <span class="hlt">Antarctic</span> Peninsula in the direct vicinity of the Chilean <span class="hlt">Antarctic</span> Base General Bernardo O'Higgins. The most important scientific instrument of the station is the 9-m antenna system which is used for the reception of satellite data, telecommanding of satellites and also for geodetic radiotelescope measurements. The antenna has been designed for use in extreme <span class="hlt">Antarctic</span> conditions. With this antenna system a wide range of Earth observation data of European and German satellite missions (ERS-1/-2, TerraSAR-X, TanDEM-X) are recorded since 1991. These data provide important insights into the climate and environmental changes at the <span class="hlt">Antarctic</span> Peninsula since 20 years now. Since the beginning of 2010 the station is operational and manned year-around in a 7/24 schedule. Future plans envisage a development towards an observatory for environmentally relevant research. That means that the portfolio of the station will be expanded including the development of the infrastructure, in particular the construction and operation of new scientific instruments that will be focused on long-term measurements. The paper presents an introduction to the GARS O'Higgins station, the current state and future plans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009QSRv...28.1147H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009QSRv...28.1147H"><span>Record of a Mid-Pleistocene depositional anomaly in <span class="hlt">West</span> <span class="hlt">Antarctic</span> continental margin sediments: an indicator for ice-sheet collapse?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hillenbrand, C.-D.; Kuhn, G.; Frederichs, T.</p> <p>2009-06-01</p> <p>Modern global warming is likely to cause future melting of Earth's polar ice sheets that may result in dramatic sea-level rise. A possible collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) alone, which is considered highly vulnerable as it is mainly based below sea level, may raise global sea level by up to 5-6 m. Despite the importance of the WAIS for changes in global sea level, its response to the glacial-interglacial cycles of the Quaternary is poorly constrained. Moreover, the geological evidence for the disintegration of the WAIS at some time within the last ca. 750 kyr, possibly during Marine Isotope Stage (MIS) 11 (424-374 ka), is ambiguous. Here we present physical properties, palaeomagnetic, geochemical and clay mineralogical data from a glaciomarine sedimentary sequence that was recovered from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> continental margin in the Amundsen Sea and spans more than the last 1 Myr. Within the sedimentary sequence, proxies for biological productivity (such as biogenic opal and the barium/aluminum ratio) and the supply of lithogenic detritus from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> hinterland (such as ice-rafted debris and clay minerals) exhibit cyclic fluctuations in accordance with the glacial-interglacial cycles of the Quaternary. A prominent depositional anomaly spans MIS 15-MIS 13 (621-478 ka). The proxies for biological productivity and lithogenic sediment supply indicate that this interval has the characteristics of a single, prolonged interglacial period. Even though no proxy suggests environmental conditions much different from today, we conclude that, if the WAIS collapsed during the last 800 kyr, then MIS 15-MIS 13 was the most likely time period. Apparently, the duration rather than the strength of interglacial conditions was the crucial factor for the WAIS drawdown. A comparison with various marine and terrestrial climate archives from around the world corroborates that unusual environmental conditions prevailed throughout MIS 15-MIS 13. Some of these</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T21D2197B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T21D2197B"><span>Geophysical evidence of a Large Igneous Province (LIP) in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS), and its potential influence on the stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrendt, J. C.</p> <p>2010-12-01</p> <p>The WAIS flows through the volcanically <span class="hlt">active</span> WARS. The inland rift shoulder ranges from 4-5 km elevation, (5-7 km relief, the greatest in the world); it is coincident with the Transantarctic Mountains from northern Victoria land bordering the Ross Sea, south along the <span class="hlt">west</span> and south side of the Ross Ice Shelf to the Horlick Mountains. It forms the boundary between East and <span class="hlt">West</span> Antarctica in this area, but diverges to the Ellsworth Mountains and forms the inland boundary of the WAIS and WARS there. Throughout the WARS shoulder to the Horlick Mountains, exposures of mostly late Cenozoic alkaline volcanic rocks are reported, as is the case in the coastal Marie Byrd Land area on the Southern Ocean aide of the WARS. The Transantarctic Mountains, continue at a much lower elevation (2000-750 m) to form the boundary between East and <span class="hlt">West</span> Antarctica in the Filchner Ice Shelf area. Aeromagnetic and radar ice-sounding surveys over the WAIS indicated numerous high-amplitude (100->1000 nT),5-50-km width, shallow-source, magnetic anomalies over a very extensive area (>500,000 km2 ) that has been interpreted as evidence of mostly subglacial volcanic eruptions (“volcanic centers”). Behrendt et al, (2005, 2008) interpreted these anomalies as >1000 "volcanic centers" requiring high remanent normal (and at least 10% reversed) magnetizations in the present field direction. These data were interpreted to show that >80% of the anomaly sources at the bed of the WAIS, were modified by the moving ice, requiring a younger age than the WAIS (~25 Ma). Several <span class="hlt">active</span> volcanoes have shown evidence of eruption through the WAIS and several other <span class="hlt">active</span> volcanoes are present beneath the WAIS. Although exposed volcanoes surrounding the WAIS extend in age to ~34 Ma., Mt Erebus (<1 Ma), Mt. Melbourne (<0.26 Ma), and Mt. Takahe (<0.1 Ma) are examples of <span class="hlt">active</span> volcanoes in the WAIS area. However, most "volcanic centers" are buried beneath the WAIS. If only a very small percentage of these >1000</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP43C2298T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP43C2298T"><span>The Stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet During the Last Interglacial (127-110 ka): A New Record From the Patriot Hills</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turney, C. S.; Fogwill, C. J.; Etheridge, D. M.; Bird, M. I.; Rubino, M.; Thornton, D.; Munksgaard, N.; Cooper, A.; Millman, H.; Rootes, C.; Rivera, A.; Baker, A.; Weyrich, L.</p> <p>2015-12-01</p> <p>The Last Interglacial (LIG; ca. 127 - 110 ka) is increasingly being investigated as a possible analogue for future climate change. Quantified estimates of LIG temperatures suggest global mean temperatures were approximately 2˚C warmer than the pre-industrial period, similar to the RCP2.6 scenario for the end of the twenty-first century. Importantly this period is associated with a global sea level between 6.6 and 9.4 m higher than present day, of which a significant component most probably derived from Antarctica. However, the contribution from the marine-based <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) remains highly uncertain. To investigate the stability of the WAIS we report new results from the Patriot Hills blue ice area, located close to the modern day grounding line of the Institute Ice Stream in the Weddell Sea Embayment. A multi proxy study of the ice (including water stable isotopes and atmospheric gas concentrations) provides a unique record of changing WAIS extent over the last glacial-interglacial cycle. We present evidence for the presence of LIG ice at Patriot Hills and discuss the implications for <span class="hlt">Antarctic</span> ice sheet stability and global sea level rise during super-interglacials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.C51A0078J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.C51A0078J"><span>Crustal thinning and low Lithospheric Rigidity Revealed Beneath the Catchment of Pine Island Glacier: Implications for the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, T. A.; Ferraccioli, F.; Holt, J. W.; Diehl, T. M.; Corr, H. F.; Blankenship, D. D.; Vaughan, D. G.</p> <p>2007-12-01</p> <p>Within the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) glaciers flowing into the Amundsen Sea Embayment (ASE) are known to be presently thinning and retreating fast, leading to accelerated global sea level rise. Crustal structures may provide critical, but largely unconstrained, geological boundary conditions for enhanced ice flow over this highly dynamic "collapse prone" sector of the WAIS. During the 2004-05 field season an integrated aerogeophysical survey was conducted over the catchment of Pine Island Glacier, as part of a joint US-UK exploration effort over the ASE. Here we examine 30,000- line km of airborne gravity data, which provide new insights on crustal properties and tectonic structure of a segment of the underlying <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System (WARS). Modern continental rifts are often associated with thinned crust, high heat flow, and low lithospheric rigidity. Knowledge of the lithospheric rigidity is important when estimating the amount of long-term sea-level rise associated with deglaciation processes. Comparison between the observed gravity data and isostatic compensation models suggests that the lithospheric rigidity is regionally low beneath the catchment of Pine Island Glacier. Our estimated value of equivalent elastic thickness (Te) 0-10 km is significantly lower compared to previous estimates beneath the better studied Ross Sea segment of the WARS (~30km). Modelling of the Bouguer and terrain de-correlated gravity anomalies reveals several segments of highly thinned continental crust beneath Pine Island Glacier, the Byrd Subglacial Basin and the Bentley Subglacial Trench. Crustal thinning may increase regional heat-flow, and hence increase the availability of water at the base of the ice sheet, which has implications for the long-term stability of the WAIS. Additionally we image thick subglacial sedimentary basins, which may further enhance fast glacial flow in the ASE region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4329630','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4329630"><span>Photoprotective and toxicological <span class="hlt">activities</span> of extracts from the <span class="hlt">Antarctic</span> moss Sanionia uncinata</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fernandes, Andréia da Silva; Alencar, Alexandre Santos; Evangelista, Heitor; Mazzei, José Luiz; Felzenszwalb, Israel</p> <p>2015-01-01</p> <p>Background: The <span class="hlt">Antarctic</span> moss Sanionia uncinata (Hedw.) Loeske has shown high ultraviolet (UV)-absorbers content after exposition to high levels of UV-B radiation and can be an important source of antioxidants. Objective: The aim was to investigate photoprotection and mutagenicity by the aqueous extract (AE) and hydroethanolic extract (HE) from the <span class="hlt">Antarctic</span> moss S. uncinata. Materials and Methods: Photoprotective <span class="hlt">activities</span> were determined through survival curves of Escherichia coli strains, after UV irradiation in an aqueous solution of thymine and in vitro sun protection factor (SPF). The Salmonella/microsome assays were applied to assess the mutagenicity. Results: Both extracts induced photoprotection against UV-C radiation. The AE showed a higher protection than the hydroethanolic one against UV-induced thymine dimerization. The SPFs were low in both extracts. In association to benzophenone-3 a significant increase in the SPF was detected for the AE, and a significant decrease was induced by the HE. No mutagenicity was found in the both extracts. Furthermore, it was observed absence of cytotoxicity. Conclusion: Water-extractable compounds seem to contribute on photoprotection of this <span class="hlt">Antarctic</span> moss. PMID:25709208</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACP....13.3237H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACP....13.3237H"><span>Semi-empirical models for chlorine <span class="hlt">activation</span> and ozone depletion in the <span class="hlt">Antarctic</span> stratosphere: proof of concept</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huck, P. E.; Bodeker, G. E.; Kremser, S.; McDonald, A. J.; Rex, M.; Struthers, H.</p> <p>2013-03-01</p> <p>Two semi-empirical models were developed for the <span class="hlt">Antarctic</span> stratosphere to relate the shift of species within total chlorine (Cly = HCl + ClONO2 + HOCl + 2 × Cl2 + 2×Cl2O2 + ClO + Cl) into the <span class="hlt">active</span> forms (here: ClOx = 2×Cl2O2 + ClO), and to relate the rate of ozone destruction to ClOx. These two models provide a fast and computationally inexpensive way to describe the inter- and intra-annual evolution of ClOx and ozone mass deficit (OMD) in the <span class="hlt">Antarctic</span> spring. The models are based on the underlying physics/chemistry of the system and capture the key chemical and physical processes in the <span class="hlt">Antarctic</span> stratosphere that determine the interaction between climate change and <span class="hlt">Antarctic</span> ozone depletion. They were developed considering bulk effects of chemical mechanisms for the duration of the <span class="hlt">Antarctic</span> vortex period and quantities averaged over the vortex area. The model equations were regressed against observations of daytime ClO and OMD providing a set of empirical fit coefficients. Both semi-empirical models are able to explain much of the intra- and inter-annual variability observed in daily ClOx and OMD time series. This proof-of-concept paper outlines the semi-empirical approach to describing the evolution of <span class="hlt">Antarctic</span> chlorine <span class="hlt">activation</span> and ozone depletion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11539461','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11539461"><span>Biologically <span class="hlt">active</span> substances produced by <span class="hlt">antarctic</span> cryptoendolithic fungi.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ocampo-Friedmann, R; Friedmann, E I</p> <p>1993-01-01</p> <p>Researchers report results of laboratory studies of over 200 microbial strains of fungi, algae, cyanobacteria, and heterotrophic bacteria collected in the Ross Desert region of Antarctica. All of the 35 fungal strains produced substances that inhibited the growth of cyanobacteria and algae. The inhibitory effect of the biologically <span class="hlt">active</span> substance was evident in crushed cell extract but less in spent broth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004GPC....42..177B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004GPC....42..177B"><span>Shallow-source aeromagnetic anomalies observed over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet compared with coincident bed topography from radar ice sounding—new evidence for glacial "removal" of subglacially erupted late Cenozoic rift-related volcanic edifices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrendt, John C.; Blankenship, Donald D.; Morse, David L.; Bell, Robin E.</p> <p>2004-07-01</p> <p>Aeromagnetic and radar ice sounding results from the 1991-1997 Central <span class="hlt">West</span> Antarctica (CWA) aerogeophysical survey over part of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) and subglacial area of the volcanically <span class="hlt">active</span> <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system have enabled detailed examination of specific anomaly sources. These anomalies, previously interpreted as caused by late Cenozoic subglacial volcanic centers, are compared to newly available glacial bed-elevation data from the radar ice sounding compilation of the entire area of the aeromagnetic survey to test this hypothesis in detail. We examined about 1000 shallow-source magnetic anomalies for bedrock topographic expression. Using very conservative criteria, we found over 400 specific anomalies which correlate with bed topography directly beneath each anomaly. We interpret these anomalies as indicative of the relative abundance of volcanic anomalies having shallow magnetic sources. Of course, deeper source magnetic anomalies are present, but these have longer wavelengths, lower gradients and mostly lower amplitudes from those caused by the highly magnetic late Cenozoic volcanic centers. The great bulk of these >400 (40-1200-nT) anomaly sources at the base of the ice have low bed relief (60-600 m, with about 80%<200 m). We interpret this relief as an indication of residual topography after glacial removal of volcanic edifices comprising hyaloclastite, pillow breccia and other volcanic debris erupted into the moving ice during volcanism since the initiation of the WAIS >10 million years ago. Eighteen of the anomalies examined, about half concentrated in the area of the WAIS divide, have high-topographic expression (as great as 400 m above sea level) and high bed relief (up to 1500 m). All of these high-topography anomaly sources at the base of the ice would isostatically rebound to elevations above sea level were the ice removed. We interpret these 18 anomaly sources as evidence of subaerial eruption of volcanoes whose topography</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026963','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026963"><span>Shallow-source aeromagnetic anomalies observed over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet compared with coincident bed topography from radar ice sounding - New evidence for glacial "removal" of subglacially erupted late Cenozoic rift-related volcanic edifices</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Behrendt, John C.; Blankenship, D.D.; Morse, D.L.; Bell, R.E.</p> <p>2004-01-01</p> <p>Aeromagnetic and radar ice sounding results from the 1991-1997 Central <span class="hlt">West</span> Antarctica (CWA) aerogeophysical survey over part of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) and subglacial area of the volcanically <span class="hlt">active</span> <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system have enabled detailed examination of specific anomaly sources. These anomalies, previously interpreted as caused by late Cenozoic subglacial volcanic centers, are compared to newly available glacial bed-elevation data from the radar ice sounding compilation of the entire area of the aeromagnetic survey to test this hypothesis in detail. We examined about 1000 shallow-source magnetic anomalies for bedrock topographic expression. Using very conservative criteria, we found over 400 specific anomalies which correlate with bed topography directly beneath each anomaly. We interpret these anomalies as indicative of the relative abundance of volcanic anomalies having shallow magnetic sources. Of course, deeper source magnetic anomalies are present, but these have longer wavelengths, lower gradients and mostly lower amplitudes from those caused by the highly magnetic late Cenozoic volcanic centers. The great bulk of these >400 (40-1200-nT) anomaly sources at the base of the ice have low bed relief (60-600 m, with about 80%10 million years ago. Eighteen of the anomalies examined, about half concentrated in the area of the WAIS divide, have high-topographic expression (as great as 400 m above sea level) and high bed relief (up to 1500 m). All of these high-topography anomaly sources at the base of the ice would isostatically rebound to elevations above sea level were the ice removed. We interpret these 18 anomaly sources as evidence of subaerial eruption of volcanoes whose topography was protected from erosion by competent volcanic flows similar to prominent volcanic peaks that are exposed above the surface of the WAIS. Further, we infer these volcanoes as possibly erupted at a time when the WAIS was absent. In contrast, at the other extreme</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26172960','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26172960"><span>Continuous <span class="hlt">activity</span> and no cycling of clock genes in the <span class="hlt">Antarctic</span> midge during the polar summer.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kobelkova, Alena; Goto, Shin G; Peyton, Justin T; Ikeno, Tomoko; Lee, Richard E; Denlinger, David L</p> <p>2015-10-01</p> <p>The extreme seasonal shifts of day length in polar regions, ranging from constant light in the summer to constant darkness in the winter, pose an intriguing environment for probing <span class="hlt">activity</span> rhythms and the functioning of circadian clocks. Here, we monitor locomotor <span class="hlt">activity</span> during the summer on the <span class="hlt">Antarctic</span> Peninsula and under laboratory conditions, as well as the accompanying patterns of clock gene expression in the <span class="hlt">Antarctic</span> midge, the only insect endemic to Antarctica. Larvae and adults are most <span class="hlt">active</span> during the warmest portion of the day, but at a constant temperature they remain continuously <span class="hlt">active</span> regardless of the photoregime, and <span class="hlt">activity</span> also persists in constant darkness. The canonical clock genes period, timeless, Clock, and vrille are expressed in the head but we detected no cycling of expression in either the field or under diverse photoregimes in the laboratory. The timekeeping function of the clock has possibly been lost, enabling the midge to opportunistically exploit the unpredictable availability of permissive thermal conditions for growth, development, and reproduction during the short summer in Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10393820','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10393820"><span>Na+/K+-ATPase <span class="hlt">activity</span> during early development and growth of an <span class="hlt">Antarctic</span> sea urchin.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leong, P K; Manahan, D T</p> <p>1999-08-01</p> <p>In <span class="hlt">Antarctic</span> environments, the physiological bases for long larval life spans under natural conditions of limited food availability are not understood. The Na+ pump is likely to be involved with hypometabolic regulation in such cold environments. Changes in the <span class="hlt">activity</span> and metabolic importance of Na+/K+-ATPase were measured in embryos of the <span class="hlt">Antarctic</span> sea urchin Sterechinus neumayeri and in larvae reared under different feeding conditions. The rate of increase of total Na+/K+-ATPase <span class="hlt">activity</span> was 3.9 times faster in fed than in unfed larvae. During development and growth, there was an increase in the percentage of total, potential Na+/K+-ATPase <span class="hlt">activity</span> that was physiologically utilized. In early (10-day-old) gastrulae, 17 % was utilized in vivo, increasing to 77 % in six-arm pluteus (48-day-old) larvae. The metabolic importance of in vivo Na+/K+-ATPase <span class="hlt">activity</span> also increased during development, accounting for 12 % of metabolic rate at day 10 and 84 % at day 48. When compared at the same enzyme assay temperature (15 degrees C), the protein-specific total Na+/K+-ATPase <span class="hlt">activities</span> for late embryonic (prism) and early larval (pluteus) stages of S. neumayeri were 2.6 times lower than those for comparable developmental stages of two temperate sea urchin species (Strongylocentrotus purpuratus and Lytechinus pictus).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.V13D0570B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.V13D0570B"><span>Negative Magnetic Anomalies Observed in the Central <span class="hlt">West</span> Antarctica (CWA) Aerogeophysical Survey Over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS), Whose Sources are Volcanic Centers (e.g. Mt Resnik) at the Base of the ice >780 Ka</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrendt, J. C.; Finn, C. A.; Morse, D. L.; Blankenship, D. D.</p> <p>2005-12-01</p> <p>Analysis of a block of coincident aeromagnetic and radar ice-sounding data (from the CWA aerogeophysical survey) over the WAIS reveals ~1000 50->1000-nT, shallow -source, ``volcanic" magnetic anomalies, interpreted as caused by late Cenozoic alkaline magmatism associated with the <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system (WR). About 400 of these anomalies (conservatively selected) have topographic expression at the bed of the WAIS; >80% of these topographic features have <200 m bed relief. There are ~100 short-wavelength, steep-gradient, negative magnetic anomalies observed in the CWA survey, or ~10% of the ~1000 ``volcanic" anomalies. These negative anomalies indicate volcanic <span class="hlt">activity</span> during a time of magnetic field reversal from normal to reversed polarity at least as old as 780 Ka (the Brunes-Matuyama reversal). The sources of ~18 of the anomalies, half concentrated in the area of the WAIS divide, have high bed-elevation (above sea level after ice removal and glacial rebound), very magnetic topography of high bed relief, up to 2 km. Five of these peaks have associated negative magnetic anomalies. One of the high topographic features, Mt. Resnik, marked by a complex negative anomaly, is a conical peak 300 m below the surface of the WAIS, and has ~2 km topographic relief. We interpret a magnetic model fit to this anomaly as comprising reversely magnetized (in the present field direction), 0.5-2.5-km thick volcanic flows at the summit overlying normally magnetized flows. Published models (1996) reported for the Hut Point anomaly, at Ross Island, Antarctica, a similar anomaly to Mt. Resnik, also required both normal and reversed magnetizations correlated with drill holes into dated volcanic flows (also part of the late Cenozoic WR) crossing the Brunhes-Matuyama boundary (780 Ka). Because of their form similar to exposed volcanoes in the WAIS area with edifices primarily comprising subaerially-erupted, very magnetic volcanic flows, which have resisted glacial erosion, Behrendt et</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP11B1783E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP11B1783E"><span>An unusual early Holocene diatom event north of the Getz Ice Shelf (Amundsen Sea): Implications for <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet development</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esper, O.; Gersonde, R.; Hillenbrand, C.; Kuhn, G.; Smith, J.</p> <p>2011-12-01</p> <p>Modern global change affects not only the polar north but also, and to increasing extent, the southern high latitudes, especially the <span class="hlt">Antarctic</span> regions covered by the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS). Consequently, knowledge of the mechanisms controlling past WAIS dynamics and WAIS behaviour at the last deglaciation is critical to predict its development in a future warming world. Geological and palaeobiological information from major drainage areas of the WAIS, like the Amundsen Sea Embayment, shed light on the history of the WAIS glaciers. Sediment records obtained from a deep inner shelf basin north of Getz Ice Shelf document a deglacial warming in three phases. Above a glacial diamicton and a sediment package barren of microfossils that document sediment deposition by grounded ice and below an ice shelf or perennial sea ice cover (possibly fast ice), respectively, a sediment section with diatom assemblages dominated by sea ice taxa indicates ice shelf retreat and seasonal ice-free conditions. This conclusion is supported by diatom-based summer temperature reconstructions. The early retreat was followed by a phase, when exceptional diatom ooze was deposited around 12,500 cal. years B.P. [1]. Microscopical inspection of this ooze revealed excellent preservation of diatom frustules of the species Corethron pennatum together with vegetative Chaetoceros, thus an assemblage usually not preserved in the sedimentary record. Sediments succeeding this section contain diatom assemblages indicating rather constant Holocene cold water conditions with seasonal sea ice. The deposition of the diatom ooze can be related to changes in hydrographic conditions including strong advection of nutrients. However, sediment focussing in the partly steep inner shelf basins cannot be excluded as a factor enhancing the thickness of the ooze deposits. It is not only the presence of the diatom ooze but also the exceptional preservation and the species composition of the diatom assemblage</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C31A0579K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C31A0579K"><span>LGM-extent of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet offshore from the Hobbs Coast, based on paleo-ice stream bed observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klages, J.; Kuhn, G.; Hillenbrand, C.; Graham, A. G.; Smith, J.; Larter, R. D.; Gohl, K.</p> <p>2012-12-01</p> <p>Paleo-ice stream beds that are exposed today on the <span class="hlt">West</span> <span class="hlt">Antarctic</span> continental shelf provide unique archives of conditions at the base of the past ice sheet, that are difficult to assess beneath its modern, extant counterpart. During the last decade, several of these paleo-ice stream beds have been studied in detail to reconstruct the extent of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) at the Last Glacial Maximum (LGM), the patterns of ice drainage, and the timing of grounding-line retreat during the last deglaciation. However, despite significant advances, such information still remains poorly constrained in numerous drainage sectors of the WAIS. In particular, the maximum extent of ice at the LGM remains ambiguous for key drainage basins of the ice sheet. Whether the WAIS extended to the shelf break around the continent, or advanced only partially across its sea bed, is a crucial piece of information required for reconstructing and modeling patterns of ice-sheet change from past to present. Here we present marine geological and geophysical data that we collected on R/V "Polarstern" expedition ANT-XXVI/3 in early 2010 to investigate the extent, flow, and retreat of the WAIS, from an especially poorly studied part of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf, offshore from the Hobbs Coast in the western Amundsen Sea. Here, a landward deepening paleo-ice stream trough is incised into the shelf. The seafloor within the western-central part of the trough is characterized by a large trough-wide grounding zone wedge, ~70 m thick and ~17 km long, which overlies a high of seaward dipping sedimentary strata. The back-slope of the GZW is characterized by highly elongate streamlined bedforms suggesting fast paleo-ice flow towards NW. The crest of the wedge has been cross-cutted by iceberg keels. In contrast, the outer shelf seafloor offshore the GZW is predominantly smooth and featureless, although there is some evidence locally for iceberg scouring. A radiocarbon age from calcareous microfossils</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChJOL..34.1064Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChJOL..34.1064Y"><span><span class="hlt">Activation</span> of macrophages by an exopolysaccharide isolated from <span class="hlt">Antarctic</span> Psychrobacter sp. B-3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Leiye; Sun, Guojie; Wei, Jingfang; Wang, Yingze; Du, Chao; Li, Jiang</p> <p>2016-09-01</p> <p>An exopolysaccharide (EPS) was isolated and purified from an <span class="hlt">Antarctic</span> psychrophilic bacterium B-3, identified as Psychrobacter sp., and the <span class="hlt">activation</span> of RAW264.7 cells by B-3 EPS was investigated. The results show that B-3 EPS, over a certain concentration range, promoted cell viability, nitric oxide production, tumor necrosis factor (TNF)α secretion, and phagocytic ability. Furthermore, TAK-242, an inhibitor of the toll-like receptor 4 (TLR4) significantly reduced nitric oxide production by these cells after stimulation with B-3 EPS. Moreover, B-3 EPS induced p65 phosphorylation and IκBα degradation in these cells. In conclusion, B-3 EPS might have <span class="hlt">activated</span> RAW264.7 cells by combining with TLR4 on cell surface and triggering <span class="hlt">activation</span> of NF-κB signaling pathways, implying that this EPS could <span class="hlt">activate</span> macrophages and regulate initial immune response.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2007/1047/srp/srp052/of2007-1047srp052.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2007/1047/srp/srp052/of2007-1047srp052.pdf"><span>Regional seismic stratigraphic correlations of the Ross Sea: Implications for the tectonic history of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Decesari, Robert C.; Sorlien, Christopher C.; Luyendyk, Bruce P.; Wilson, Douglas S.; Bartek, Louis; Diebold, John; Hopkins, Sarah E.</p> <p>2007-01-01</p> <p>Using existing and new seismic reflection data, new and updated correlations of late Oligocene-early Miocene RSS-2 strata were made between the southern parts of Ross Sea basins. Previous studies documented Cretaceous extension across much of Ross Sea. We interpret that Cenozoic extension also occurred across Ross Sea. Subsidence during and following this extension deepened existing basins and may have initiated basins in the <span class="hlt">west</span>, subsiding ridges between basins below sea level during the late Oligocene. Pre-Oligocene strata record cessation of L. Cretaceous extension in easternmost Ross Sea. Successively younger Cenozoic extension occurred from east to <span class="hlt">west</span> across the rest of Ross Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C33A0656M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C33A0656M"><span>Could a new ice core offer an insight into the stability of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet during the last interglacial?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mulvaney, R.; Hindmarsh, R. C.</p> <p>2013-12-01</p> <p>Vaughan et al., in their 2011 paper 'Potential Seaways across <span class="hlt">West</span> Antarctica' (Geochem. Geophys. Geosyst., 12, Q10004, doi:10.1029/2011GC003688), offer the intriguing prospect that substantial ice loss from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet during the previous interglacial period might have resulted in the opening of a seaway between the Weddell Sea and the Amundsen Sea. One of their potential seaways passes between the south western corner of the present Ronne Ice Shelf and the Pine Island Bay, through what is currently the course of the Rutford Ice Stream, between the Ellsworth Mountains and the Fletcher Promontory. To investigate whether this seaway could have existed (and to recover a paleoclimate and ice sheet history from the Weddell Sea), a team from the British <span class="hlt">Antarctic</span> Survey and the Laboratoire de Glaciologie et Géophysique de l'Environnement drilled an ice core from a close to a topographic dome in the ice surface on the Fletcher Promontory in January 2012, reaching the bedrock at 654.3m depth from the surface. The site was selected to penetrate directly through the centre of a Raymond cupola observed in internal radar reflections from the ice sheet, with the intention that this would ensure we obtained the oldest ice available from the Fletcher Promontory. The basal ice sheet temperature measured was -18°C, implying the oldest ice would not have melted away from the base, while the configuration of the Raymond cupola in the radar horizons suggested stability in the ice dome topography during the majority of the Holocene. Our hypothesis is that chemical analysis of the ice core will reveal whether the site was ever relatively close to open sea water or ice shelf in the Rutford channel 20 km distant, rather than the current 700 km distance to sea ice/open water in either the Weddell Sea or the Amundsen Sea. While we do not yet have the chemistry data to test this hypothesis, in this poster we will discuss whether there is in reality any potential local</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GMD.....9.1697P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GMD.....9.1697P"><span>Large ensemble modeling of the last deglacial retreat of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet: comparison of simple and advanced statistical techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pollard, David; Chang, Won; Haran, Murali; Applegate, Patrick; DeConto, Robert</p> <p>2016-05-01</p> <p>A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet over the last ˜ 20 000 yr. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation-age data and uplift rates, with an aggregate score computed for each run that measures overall model-data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov chain Monte Carlo. The analyses provide sea-level-rise envelopes with well-defined parametric uncertainty bounds, but the simple averaging method only provides robust results with full-factorial parameter sampling in the large ensemble. Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree well with the more advanced techniques. Best-fit parameter ranges confirm earlier values expected from prior model tuning, including large basal sliding coefficients on modern ocean beds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23274977','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23274977"><span>Effects of nutritional input and diesel contamination on soil enzyme <span class="hlt">activities</span> and microbial communities in <span class="hlt">Antarctic</span> soils.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Han, Jiwon; Jung, Jaejoon; Hyun, Seunghun; Park, Hyun; Park, Woojun</p> <p>2012-12-01</p> <p>Pollution of <span class="hlt">Antarctic</span> soils may be attributable to increased nutritional input and diesel contamination via anthropogenic <span class="hlt">activities</span>. To investigate the effect of these environmental changes on the <span class="hlt">Antarctic</span> terrestrial ecosystem, soil enzyme <span class="hlt">activities</span> and microbial communities in 3 types of <span class="hlt">Antarctic</span> soils were evaluated. The <span class="hlt">activities</span> of alkaline phosphomonoesterase and dehydrogenase were dramatically increased, whereas the <span class="hlt">activities</span> of β-glucosidase, urease, arylsulfatase, and fluorescein diacetate hydrolysis were negligible. Alkaline phosphomonoesterase and dehydrogenase <span class="hlt">activities</span> in the 3 types of soils increased 3- to 10-fold in response to nutritional input, but did not increase in the presence of diesel contamination. Consistent with the enzymatic <span class="hlt">activity</span> data, increased copy numbers of the phoA gene, encoding an alkaline phosphomonoesterase, and the 16S rRNA gene were verified using quantitative real-time polymerase chain reaction. Interestingly, dehydrogenase <span class="hlt">activity</span> and 16S rRNA gene copy number increased slightly after 30 days, even under diesel contamination, probably because of adaptation of the bacterial population. Intact <span class="hlt">Antarctic</span> soils showed a predominance of Actinobacteria phylum (mostly Pseudonorcarida species) and other phyla such as Proteobacteria, Chloroflexi, Planctomycetes, Firmicutes, and Verrucomicrobia were present in successively lower proportions. Nutrient addition might act as a selective pressure on the bacterial community, resulting in the prevalence of Actinobacteria phylum (mostly Arthrobacter species). Soils contaminated by diesel showed a predominance of Proteobacteria phylum (mostly Phyllobacterium species), and other phyla such as Actinobacteria, Bacteroidetes, Planctomycetes, and Gemmatimonadetes were present in successively lower proportions. Our data reveal that nutritional input has a dramatic impact on bacterial communities in <span class="hlt">Antarctic</span> soils and that diesel contamination is likely toxic to enzymes in this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020048709&hterms=ciencia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dciencia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020048709&hterms=ciencia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dciencia"><span><span class="hlt">Antarctic</span> Polar Descent and Planetary Wave <span class="hlt">Activity</span> Observed in ISAMS CO from April to July 1992</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allen, D. R.; Stanford, J. L.; Nakamura, N.; Lopez-Valverde, M. A.; Lopez-Puertas, M.; Taylor, F. W.; Remedios, J. J.</p> <p>2000-01-01</p> <p><span class="hlt">Antarctic</span> polar descent and planetary wave <span class="hlt">activity</span> in the upper stratosphere and lower mesosphere are observed in ISAMS CO data from April to July 1992. CO-derived mean April-to-May upper stratosphere descent rates of 15 K/day (0.25 km/day) at 60 S and 20 K/day (0.33 km/day) at 80 S are compared with descent rates from diabatic trajectory analyses. At 60 S there is excellent agreement, while at 80 S the trajectory-derived descent is significantly larger in early April. Zonal wavenumber 1 enhancement of CO is observed on 9 and 28 May, coincident with enhanced wave 1 in UKMO geopotential height. The 9 May event extends from 40 to 70 km and shows westward phase tilt with height, while the 28 May event extends from 40 to 50 km and shows virtually no phase tilt with height.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10724159','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10724159"><span>Cenozoic motion between East and <span class="hlt">West</span> Antarctica</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cande; Stock; Muller; Ishihara</p> <p>2000-03-09</p> <p>The <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system is the result of late Mesozoic and Cenozoic extension between East and <span class="hlt">West</span> Antarctica, and represents one of the largest <span class="hlt">active</span> continental rift systems on Earth. But the timing and magnitude of the plate motions leading to the development of this rift system remain poorly known, because of a lack of magnetic anomaly and fracture zone constraints on seafloor spreading. Here we report on magnetic data, gravity data and swath bathymetry collected in several areas of the south Tasman Sea and northern Ross Sea. These results enable us to calculate mid-Cenozoic rotation parameters for East and <span class="hlt">West</span> Antarctica. These rotations show that there was roughly 180 km of separation in the western Ross Sea embayment in Eocene and Oligocene time. This episode of extension provides a tectonic setting for several significant Cenozoic tectonic events in the Ross Sea embayment including the uplift of the Transantarctic Mountains and the deposition of large thicknesses of Oligocene sediments. Inclusion of this East-<span class="hlt">West</span> <span class="hlt">Antarctic</span> motion in the plate circuit linking the Australia, <span class="hlt">Antarctic</span> and Pacific plates removes a puzzling gap between the Lord Howe rise and Campbell plateau found in previous early Tertiary reconstructions of the New Zealand region. Determination of this East-<span class="hlt">West</span> <span class="hlt">Antarctic</span> motion also resolves a long standing controversy regarding the contribution of deformation in this region to the global plate circuit linking the Pacific to the rest of the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1511521W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1511521W"><span>Response of marine sedimentation to upper Holocene climate variability in Maxwell Bay, King George Island, <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wittenberg, Nina; Hass, Christian; Kuhn, Gerhard</p> <p>2013-04-01</p> <p>The Western <span class="hlt">Antarctic</span> Peninsula experiences a temperature increase that is higher than in other parts of Antarctica. Within the last 50 years the tidewater glaciers in the tributary fjords of Maxwell Bay (King George Island) have retreated landwards with increasing speed. Meltwaters mobilize fine-grained sediments and transport those in plumes out of the coves into Maxwell Bay. Our hypothesis is that meltwater sediments characterize warmer climate periods of the Holocene. Marine sediment cores recovered along a profile of the eastern slope of Maxwell Bay were studied. The cores were taken in high-accumulation areas at the entrances of Collins Harbor, Marian and Potter coves. We measured the grain-size distribution in 1-cm steps in each core with a Laser diffraction particle analyzer (range 0.04-2500 µm) in order to resolve shifts in grain size compositions in very high resolution. We undertook different approaches for reliable age determination of the sediments. Since marine biogenic carbonate suitable for radiocarbon age determination is sparse, radiocarbon dating of the extracted humic acid fraction of the bulk sediment was included. Unfortunately, these age determinations turned out to be not reliable, likely because they are overprinted by an unknown older radiocarbon source. Preliminary results suggest that the cores cover approximately the last 2000 years. The magnetic susceptibility (MS) parameter fluctuates throughout the cores. It is negatively correlated to the amount of total organic carbon (TOC) and biogenic opal, suggesting dilution of the MS signal through higher input of organic material. Together with the bathymetry data, sub-bottom profiles reveal information on the interior of the topography and the geometry of the deposited sediments. The profiles obtained in Potter Cove show almost no sediment penetration suggesting either a very thin sediment cover and/or highly reworked unsorted sediments. The sub-bottom profiles from Maxwell Bay penetrate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012E%26PSL.337..243M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012E%26PSL.337..243M"><span>Miocene to recent ice elevation variations from the interior of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet: Constraints from geologic observations, cosmogenic nuclides and ice sheet modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mukhopadhyay, Sujoy; Ackert, Robert P.; Pope, Allen E.; Pollard, David; DeConto, Robert M.</p> <p>2012-07-01</p> <p>Observations of long-term <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) behavior can be used to test and constrain dynamic ice sheet models. Long-term observational constraints are however, rare. Here we present the first constraints on long-term (Miocene-Holocene) WAIS elevation from the interior of the ice sheet near the WAIS divide. We use geologic observations and measurements of cosmogenic 21Ne and 10Be in bedrock surfaces to constrain WAIS elevation variations to <160 m above the present-day ice levels since 7 Ma, and <110 m above present-day ice levels since 5.4 Ma. The cosmogenic nuclide data indicate that bedrock surfaces 35 m above the present-day ice levels had near continuous exposure over the past 3.5 Ma, requiring average interior WAIS elevations to have been similar to, or lower than present, since the beginning of the Pliocene warm period. We use a continental ice sheet model to simulate the history of ice cover at our sampling sites and thereby compute the expected concentration of the cosmogenic nuclides. The ice sheet model indicates that during the past 5 Ma interior WAIS elevations of >65 m above present-day ice levels at the Ohio Range occur only rarely during brief ice sheet highstands, consistent with the observed cosmogenic nuclide data. Furthermore, the model's prediction that highstand elevations have increased on average since the Pliocene is in good agreement with the cosmogenic nuclide data that indicate the highest ice elevation over the past 5 Ma was reached during the highstand at 11 ka. Since the simulated cosmogenic nuclide concentrations derived from the model's ice elevation history are in good agreement with our measurements, we suggest that the model's prediction of more frequent collapsed-WAIS states and smaller WAIS volumes during the Pliocene are also correct.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUSM.U42A..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUSM.U42A..07P"><span>New Insights into <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet History Based on Ground Penetrating Radar Linking Stratigraphy With Surface-Exposure Dated Geomorphology in Lower Taylor Valley, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prentice, M. L.; Arcone, S.; Ackert, R.</p> <p>2002-05-01</p> <p>A most extensive record of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) during the last glacial cycle is found in lower Taylor Valley. We gained new insights into the drift stratigraphy using ground-penetrating radar (GPR) and surface-exposure dating in selected locations there. Evidence for the following two hypotheses will be presented. The WAIS achieved Last Glacial Maximum size between the LGM and the penultimate glaciation based on the exposure ages of boulders mantling moraines that GPR indicates are stratigraphically older than late Wisconsin drift. The drift record is on Hjorth Hill. Exposure ages range between 29 and 85 kya. The Taylor lobe of the WAIS dammed a valley-wide glacial lake, Glacial Lake Washburn between 21,200 and 8,340 14C yr BP. How and when the Taylor Lobe disintegrated are debated. We collected GPR profiles at both 100 and 400 MHz on transverse ridges that could date the recession of the Taylor Lobe. We calibrated GPR to sediment stratigraphy, primarily using 10 drill holes in eastern Taylor Valley. Ridge GPR consistently shows multiple superposed sediment packets each with internal sub-parallel reflections that resemble the stratification of migrating current ripples. We interpret the reflectors as foreset (megaripple) bedding. We think that the scalloped-shaped surfaces represent erosion indicative of a shift in current regime. Cross profiles show the festoon-shaped packets of cross-bedded units that characterize undulatory to lunate ripples. We interpret the ridges as form-discordant composite mega- and giant-current ripples. The boulders on the ripples are glacial erratics and attest to the close presence of glacial ice. The environment of deposition, ice-contact supraglacial, was characterized by high meltwater outflow from streams running off the glacier. Therefore, ridge chronology directly dates recession of the Taylor Valley lobe to about 17,000 - 13,000 14C yrs BP. Climate warming was involved in ice disintegration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C43B0544P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C43B0544P"><span>Neogene deformation in the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift in the McMurdo Sound region from studies of the ANDRILL and Cape Roberts drill cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paulsen, T. S.; Wilson, T. J.; Jarrard, R. D.; Millan, C.; Saddler, D.; Läufer, A.; Pierdominici, S.</p> <p>2010-12-01</p> <p>Seismic studies indicate that the <span class="hlt">West</span> <span class="hlt">Antarctic</span> rift system records at least two distinct periods of Cenozoic rifting (Paleogene and Neogene) within the western Ross Sea. Natural fracture data from ANDRILL and Cape Roberts drill cores are revealing a picture of the geodynamic patterns associated with these rifting episodes. Kinematic indicators along faults recovered in drill cores document dominant normal faulting, although reverse and strike-slip faults are also present. Ongoing studies of mechanically twinned calcite in veins recovered in the drill cores yield predominantly vertical shortening strains with horizontal extension, consistent with a normal fault regime. In the Cape Roberts Project drill core, faults of inferred Oligocene age document a dominant NNE maximum horizontal stress associated with Paleogene rifting within the Victoria Land Basin. The NNE maximum horizontal stress at Cape Roberts is at an oblique angle to Transantarctic Mountain front, and consistent with previous interpretations invoking Cenozoic dextral transtensional shear along the boundary. In the ANDRILL SMS (AND-2A) drill core, faults and veins presumably associated with Neogene rifting document a dominant NNW to NE faulting of an expanded Lower Miocene section, although subsidiary WNW faulting is also present within the upper sections of oriented core. In the ANDRILL MIS (AND-1B) drill core, natural fractures are consistently present through the core below c. 450 mbsf, the estimated depth of the ‘B-clino’ seismic reflector. This is consistent with the presence of seismically-detectable faults below this horizon, which record the major faulting episode associated with Neogene rifting in the Terror Rift. Sedimentary intrusions and steep veins folded by compaction indicate that deformation occurred prior to complete lithification of the strata, suggesting that deformation was at least in part coeval with deposition. Faults and associated veins intersected in the AND-1B drill core</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V51A1664L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V51A1664L"><span>The Peralkaline Rhyolite Spectrum in Marie Byrd Land Volcanoes, <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift, and the Case for Polybaric Fractionation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lemasurier, W. E.; Choi, S.; Mukasa, S. B.; Rogers, N. W.</p> <p>2009-12-01</p> <p>The Marie Byrd Land (MBL) volcanic province is associated with the rise of a large tectonomagmatic dome, over the past 25-30 m.y. Since 14-15 Ma, five volcanoes have produced pantellerites and three others have produced comendites. Together they display a range in SiO2, Al2O3, FeOt, and peralkalinity that is comparable with the full range of compositions in Pantelleria and the Kenyan and Ethiopian dome provinces. The comendite volcanoes occur on the east flank of the MBL dome, adjacent to volcanoes characterized by highly undersaturated phonolites (20-30% ne). The pantellerite volcanoes, with one exception, occur on the <span class="hlt">west</span> flank, associated with less undersaturated phonolites (6-11% ne). These seem to represent two fairly distinct sub-provinces with perhaps slightly different plumbing systems. Isotopic and trace element data, maintenance of isotopic equilibrium throughout the basalt-felsic spectrum, and the results of major and trace element modeling, all exclude crustal contamination and point to fractional crystallization as the controlling process in the origins of the felsic rocks. The availability of basalts in several stages of evolution, plus a variety of mugearites, benmoreites, and trachytes, have allowed us to model the evolution of felsic rocks in several stages. The best results, together with trace element and petrographic data, and supported by experimental work, suggest that polybaric fractionation in a multi-tiered plumbing system provides the most reasonable explanation of field, petrographic and geochemical characteristics. A plumbing system that favors prolonged kaersutite fractionation at the base of the crust for comendites (east flank) vs. one that favors comparatively short residency and little kaersutite fractionation at the base of the crust for pantellerites (<span class="hlt">west</span> flank), seems to provide the best explanation for the differences in SiO2 and FeOt, and the wide spatial separation of these two rhyolite species. The models suggest further</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23779196','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23779196"><span>A gene encoding a new cold-<span class="hlt">active</span> lipase from an <span class="hlt">Antarctic</span> isolate of Penicillium expansum.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mohammed, Suja; Te'o, Junior; Nevalainen, Helena</p> <p>2013-08-01</p> <p>Cold-<span class="hlt">active</span> lipases are of significant interest as biocatalysts in industrial processes. We have identified a lipase that displayed <span class="hlt">activity</span> towards long carbon-chain-p-nitrophenyl substrates (C12-C18) at 25 °C from the culture supernatant of an <span class="hlt">Antarctic</span> Penicillium expansum strain assigned P. expansum SM3. Zymography revealed a protein band of around 30 kDa with <span class="hlt">activity</span> towards olive oil. DNA fragments of a lipase gene designated as lipPE were isolated from the genomic DNA of P. expansum SM3 by genomic walking PCR. Subsequently, the complete genomic lipPE gene was amplified using gene-specific primers designed from the 5'- and 3'-regions. Reverse transcription PCR was used to amplify the lipPE cDNA. The deduced amino acid sequence consisted of 285 residues that included a predicted signal peptide. Three peptides identified by LC/MS/MS analysis of the proteins in the culture supernatant of P. expansum were also present in the deduced amino acid sequence of the lipPE gene suggesting that this gene encoded the lipase identified by initial zymogram <span class="hlt">activity</span> analysis. Full analysis of the nucleotide and the deduced amino acid sequences indicated that the lipPE gene encodes a novel P. expansum lipase. The lipPE gene was expressed in E. coli for further characterization of the enzyme with a view of assessing its suitability for industrial applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25965896','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25965896"><span>Benzo(a)pyrene Metabolism and EROD and GST Biotransformation <span class="hlt">Activity</span> in the Liver of Red- and White-Blooded <span class="hlt">Antarctic</span> Fish.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Strobel, Anneli; Burkhardt-Holm, Patricia; Schmid, Peter; Segner, Helmut</p> <p>2015-07-07</p> <p>Climate change and anthropogenic pollution are of increasing concern in remote areas such as Antarctica. The evolutionary adaptation of <span class="hlt">Antarctic</span> notothenioid fish to the cold and stable Southern Ocean led to a low plasticity of their physiological functions, what may limit their capacity to deal with altered temperature regimes and pollution in the <span class="hlt">Antarctic</span> environment. Using a biochemical approach, we aimed to assess the hepatic biotransformation capacities of <span class="hlt">Antarctic</span> fish species by determining (i) the <span class="hlt">activities</span> of ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST), and (ii) the metabolic clearance of benzo(a)pyrene by hepatic S9 supernatants. In addition, we determined the thermal sensitivity of the xenobiotic biotransformation enzymes. We investigated the xenobiotic metabolism of the red-blooded Gobionotothen gibberifrons and Notothenia rossii, the hemoglobin-less Chaenocephalus aceratus and Champsocephalus gunnari, and the rainbow trout Oncorhynchus mykiss as a reference. Our results revealed similar metabolic enzyme <span class="hlt">activities</span> and metabolic clearance rates between red- and white-blooded <span class="hlt">Antarctic</span> fish, but significantly lower rates in comparison to rainbow trout. Therefore, bioaccumulation factors for metabolizable lipophilic contaminants may be higher in <span class="hlt">Antarctic</span> than in temperate fish. Likewise, the thermal adaptive capacities and flexibilities of the EROD and GST <span class="hlt">activities</span> in <span class="hlt">Antarctic</span> fish were significantly lower than in rainbow trout. As a consequence, increasing water temperatures in the Southern Ocean will additionally compromise the already low detoxification capacities of <span class="hlt">Antarctic</span> fish.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12686207','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12686207"><span>Ice binding, recrystallization inhibition, and cryoprotective properties of ice-<span class="hlt">active</span> substances associated with <span class="hlt">Antarctic</span> sea ice diatoms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Raymond, James A; Knight, Charles A</p> <p>2003-04-01</p> <p>Extracellular macromolecules associated with <span class="hlt">Antarctic</span> sea ice diatoms were previously shown to have ice-binding <span class="hlt">activities</span>. The function of these ice-<span class="hlt">active</span> substances (IASs) has not been identified. Here we show that two of the IASs have a strong ability to inhibit the recrystallization of ice, possibly signifying a cryoprotectant function. To test this possibility, two species of marine diatom (one <span class="hlt">Antarctic</span> and one temperate) were subjected to a single freeze-thaw cycle (approximately 20h at -4 or -5 degrees C) in the presence or absence of IAS. Viability, based on a double staining technique, was 15-29% higher in the presence of IAS. Etching of single crystal ice hemispheres grown from dilute IAS solutions indicated that the IASs bind to specific faces of ice and are incorporated into the ice lattice. Together, these results suggest that the IASs acts as a cryoprotectant, probably through some ice-binding mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23843974','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23843974"><span><span class="hlt">Antarctic</span> crabs: invasion or endurance?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Griffiths, Huw J; Whittle, Rowan J; Roberts, Stephen J; Belchier, Mark; Linse, Katrin</p> <p>2013-01-01</p> <p>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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span>. 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 <span class="hlt">Antarctic</span> distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> slope. We conclude there is no evidence for a modern-day "crab invasion". We recommend a repeated targeted lithodid sampling program along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf to fully test the validity of the "invasion hypothesis".</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3700924','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3700924"><span><span class="hlt">Antarctic</span> Crabs: Invasion or Endurance?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Griffiths, Huw J.; Whittle, Rowan J.; Roberts, Stephen J.; Belchier, Mark; Linse, Katrin</p> <p>2013-01-01</p> <p>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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span>. 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 <span class="hlt">Antarctic</span> distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> slope. We conclude there is no evidence for a modern-day “crab invasion”. We recommend a repeated targeted lithodid sampling program along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf to fully test the validity of the </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24509705','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24509705"><span>Diversity patterns, ecology and biological <span class="hlt">activities</span> of fungal communities associated with the endemic macroalgae across the <span class="hlt">Antarctic</span> peninsula.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Furbino, Laura E; Godinho, Valéria M; Santiago, Iara F; Pellizari, Franciane M; Alves, Tânia M A; Zani, Carlos L; Junior, Policarpo A S; Romanha, Alvaro J; Carvalho, Amanda G O; Gil, Laura H V G; Rosa, Carlos A; Minnis, Andrew M; Rosa, Luiz H</p> <p>2014-05-01</p> <p>We surveyed diversity patterns and engaged in bioprospecting for bioactive compounds of fungi associated with the endemic macroalgae, Monostroma hariotii and Pyropia endiviifolia, in Antarctica. A total of 239 fungal isolates were obtained, which were identified to represent 48 taxa and 18 genera using molecular methods. The fungal communities consisted of endemic, indigenous and cold-adapted cosmopolitan taxa, which displayed high diversity and richness, but low dominance indices. The extracts of endemic and cold-adapted fungi displayed biological <span class="hlt">activities</span> and may represent sources of promising prototype molecules to develop drugs. Our results suggest that macroalgae along the marine <span class="hlt">Antarctic</span> Peninsula provide additional niches where fungal taxa can survive and coexist with their host in the extreme conditions. We hypothesise that the dynamics of richness and dominance among endemic, indigenous and cold-adapted cosmopolitan fungal taxa might be used to understand and model the influence of climate change on the maritime <span class="hlt">Antarctic</span> mycota.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..568H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..568H"><span>Thermal regime of <span class="hlt">active</span> layer at two lithologically contrasting sites on James Ross Island, <span class="hlt">Antarctic</span> Peninsula.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hrbáček, Filip; Nývlt, Daniel; Láska, Kamil</p> <p>2016-04-01</p> <p><span class="hlt">Antarctic</span> Peninsula region (AP) represents one of the most rapidly warming parts of our planet in the last 50 years. Despite increasing research <span class="hlt">activities</span> along both western and eastern sides of AP in last decades, there is still a lot of gaps in our knowledge relating to permafrost, <span class="hlt">active</span> layer and its thermal and physical properties. This study brings new results of <span class="hlt">active</span> layer monitoring on James Ross Island, which is the largest island in northern AP. Its northern part, Ulu Peninsula, is the largest ice-free area (more than 200 km2) in the region. Due its large area, we focused this study on sites located in different lithologies, which would affect local thermal regime of <span class="hlt">active</span> layer. Study site (1) at Abernethy Flats area (41 m a.s.l.) lies ~7 km from northern coast. Lithologically is formed by disintegrated Cretaceous calcareous sandstones and siltstones of the Santa Marta Formation. Study site (2) is located at the northern slopes of Berry Hill (56 m a.s.l.), about 0.4 km from northern coastline. Lithology is composed of muddy to intermediate diamictites, tuffaceous siltstones to fine grained sandstones of the Mendel Formation. Data of air temperature at 2 meters above ground and the <span class="hlt">active</span> layer temperatures at 75 cm deep profiles were obtained from both sites in period 1 January 2012 to 31 December 2014. Small differences were found when comparing mean air temperatures and <span class="hlt">active</span> temperatures at 5 and 75 cm depth in the period 2012-2014. While the mean air temperatures varied between -7.7 °C and -7.0 °C, the mean ground temperatures fluctuated between -6.6 °C and -6.1 °C at 5 cm and -6.9 °C and -6.0 °C at 75 cm at Abernethy Flats and Berry Hill slopes respectively. Even though ground temperature differences along the profiles weren't pronounced during thawing seasons, the maximum <span class="hlt">active</span> layer thickness was significantly larger at Berry Hill slopes (80 to 82 cm) than at Abernethy Flats (52 to 64 cm). We assume this differences are affected by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10194383','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10194383"><span>Thermodynamic stability of a cold-<span class="hlt">active</span> alpha-amylase from the <span class="hlt">Antarctic</span> bacterium Alteromonas haloplanctis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feller, G; d'Amico, D; Gerday, C</p> <p>1999-04-06</p> <p>The thermal stability of the cold-<span class="hlt">active</span> alpha-amylase (AHA) secreted by the <span class="hlt">Antarctic</span> bacterium Alteromonas haloplanctis has been investigated by intrinsic fluorescence, circular dichroism, and differential scanning calorimetry. It was found that this heat-labile enzyme is the largest known multidomain protein exhibiting a reversible two-state unfolding, as demonstrated by the recovery of DeltaHcal values after consecutive calorimetric transitions, a DeltaHcal/DeltaHeff ratio close to unity, and the independence of unfolding thermodynamic parameters of scan rates. By contrast, the mesophilic alpha-amylases investigated here (from porcine pancreas, human salivary glands, yellow meal beetle, Bacillus amyloliquefaciens, and Bacillus licheniformis) unfold irreversibly according to a non-two-state mechanism. Unlike mesophilic alpha-amylases, the melting point of AHA is independent of calcium and chloride binding while the allosteric and structural functions of these ions are conserved. The thermostability of AHA at optimal conditions is characterized by a Tm of 43.7 degrees C, a DeltaHcal of 238 kcal mol-1, and a DeltaCp of 8.47 kcal mol-1 K-1. These values were used to calculate the Gibbs free energy of unfolding over a wide range of temperatures. This stability curve shows that (a) the specific DeltaGmax of AHA [22 cal (mol of residue)-1] is 4 times lower than that of mesophilic alpha-amylases, (b) group hydration plays a crucial role in the enzyme flexibility at low temperatures, (c) the temperature of cold unfolding closely corresponds to the lower limit of bacterial growth, and (d) the recombinant heat-labile enzyme can be expressed in mesophilic hosts at moderate temperatures. It is also argued that the cold-<span class="hlt">active</span> alpha-amylase has evolved toward the lowest possible conformational stability of its native state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26982437','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26982437"><span><span class="hlt">Antarctic</span> Entomology.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chown, Steven L; Convey, Peter</p> <p>2016-01-01</p> <p>The <span class="hlt">Antarctic</span> region comprises the continent, the Maritime <span class="hlt">Antarctic</span>, the sub-<span class="hlt">Antarctic</span> islands, and the southern cold temperate islands. Continental Antarctica is devoid of insects, but elsewhere diversity varies from 2 to more than 200 species, of which flies and beetles constitute the majority. Much is known about the drivers of this diversity at local and regional scales; current climate and glacial history play important roles. Investigations of responses to low temperatures, dry conditions, and varying salinity have spanned the ecological to the genomic, revealing new insights into how insects respond to stressful conditions. Biological invasions are common across much of the region and are expected to increase as climates become warmer. The drivers of invasion are reasonably well understood, although less is known about the impacts of invasion. <span class="hlt">Antarctic</span> entomology has advanced considerably over the past 50 years, but key areas, such as interspecific interactions, remain underexplored.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Fishes&id=EJ347993','ERIC'); return false;" href="http://eric.ed.gov/?q=Fishes&id=EJ347993"><span><span class="hlt">Antarctic</span> Fishes.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Eastman, Joseph T.; DeVries, Arthur L.</p> <p>1986-01-01</p> <p>Explains the adaptations to <span class="hlt">Antarctic</span> waters that Notothenioidei, a group of advanced bony fishes, have exhibited. Discusses the fishes' mechanisms of production of antifreeze properties and their capacities for neutral buoyancy in water. (ML)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMOS43B1240M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMOS43B1240M"><span>Seeking the True <span class="hlt">Antarctic</span> Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miller, R. G.</p> <p>2007-12-01</p> <p>With World Ocean warming a corrected name use is recommend with a universal adoption of the name, "<span class="hlt">Antarctic</span> Ocean. This one large body of circumpolar water lies adjacent to - and south of - the <span class="hlt">Antarctic</span> Convergence, on its northern perimeter, and is bordered to the south by the shoreline of the <span class="hlt">Antarctic</span> continent. The <span class="hlt">Antarctic</span> Ocean has a distinct water mass, with a true perimeter, and with a homogeneity, comprizing a unique environment for a specialized flora and fauna. It is recognized generally by its surface waters, ranging from 3.5 - 4.5 degrees Celsius (summer) and one degree C (winter).While its northern boundary, ' The <span class="hlt">Antarctic</span> Convergence', has a water quality and thermal difference, this polar front is continuous and circumpolar, and it abuts -- and streams along with -- the ultimate southern extremities of the Atlantic, Pacific and Indian Ocean waters. Parameters, characteristics and dynamics of water exchange are considered, here, with some water exchanges, with Intermediate and <span class="hlt">Antarctic</span> Bottom water noted. It maintains its own forceful '<span class="hlt">West</span> Wind Drift', a current driven and emboldened by Earth's Geostrophic <span class="hlt">West</span> Wind. Features defining the <span class="hlt">Antarctic</span> Ocean: (1)Washing all shores of the continent named Antarctica; it is .the only ocean reaching this <span class="hlt">Antarctic</span> Continent.; (2) it is one of Earth's two Polar (and coldest) oceans, the other, named Arctic Ocean, of which it is the opposite (the Anti); (3) its distinctive cold waters of the <span class="hlt">Antarctic</span> Ocean and its peripheral seas, floating ice tongues, the frigid stamp of Antarctica's continental glaciers and ice fields; (4) the <span class="hlt">Antarctic</span> Continent is the source of continual replenishment from her ice cap and melt-water derived from the great mountains, valleys and the massive polar dome of ice. Further, in the literature the present usage, 'Southern Ocean', by some authors, confuses the true <span class="hlt">Antarctic</span> environmental waters (i.e. south of - and within the South Polar Front - Convergence) with southern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21235167','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21235167"><span>Response of bacteria in the deep-sea sediments and the <span class="hlt">Antarctic</span> soils to carbohydrates: effects on ectoenzyme <span class="hlt">activity</span> and bacterial community.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zeng, Xiang; Xiao, Xiang; Wang, Fengping</p> <p>2010-01-01</p> <p>The response of bacteria to various carbohydrates in the deep-sea sediments and the <span class="hlt">Antarctic</span> soils was investigated using cellulose, chitin, and olive oil. It was found that the carbohydrates significantly increased the corresponding specific ectoenzyme <span class="hlt">activity</span> (beta-glucosidase, beta-N-acetylglucosaminidase, lipase) in the samples from deep-sea sediments. In the case of <span class="hlt">Antarctic</span> soil samples, the cellulose or olive oil amendments had minor or no effect on beta-glucosidase or lipase <span class="hlt">activity</span>, except the chitin which stimulated beta-N-acetylglucosaminidase production. The responses of the bacteria in the deep-sea sediment sample WP02-3 and the <span class="hlt">Antarctic</span> soil sample CC-TY2 towards the chitin amendment were further analyzed. Chitin amendments were shown to stimulate the ectoenzyme <span class="hlt">activity</span> in all the tested sediments and the soils. The bacterial response before and after the carbohydrates amendments were compared by denaturing gradient gel electrophoresis and quantitative competitive polymerase chain reaction. Significant changes were found in the structure and density of the bacterial community in the deep sea sediments as compared to the <span class="hlt">Antarctic</span> soil sample, where the effects were relatively lower. There was no change in the bacterial population in both studied samples in response to carbohydrates amendments. These data indicate that the bacterial communities in the oligotrophic deep-sea sediments are more dynamic than that in the <span class="hlt">Antarctic</span> soils as they respond to the nutrient sources efficiently by regulation of ectoenzyme <span class="hlt">activity</span> and/or changing community structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5305699','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5305699"><span>Carbon dioxide effects research and assessment program. Environmental and societal consequences of a possible CO/sub 2/-induced climate change: volume II, part I. Response of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet to CO/sub 2/-induced climatic warming</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bentley, C.</p> <p>1982-04-01</p> <p>The paper proposes a research plan to deal with the question of what the response of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet would be to a rise in global temperatures caused by an anthropogenic CO/sub 2/ buildup in the atmosphere. The plan is designed to answer the following questions: (1) how fast is the ice mass changing now, and why; (2) how will the boundary conditions that affect the ice sheet respond to an atmospheric temperature change and how are those boundary conditions changing now; (3) what will be the response of the ice sheet to changes in boundary conditions; and (4) what can be learned by analogy with what has happened in the past. (ACR)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19369080','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19369080"><span>Effects of detergents on the <span class="hlt">West</span> Nile virus protease <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ezgimen, Manolya D; Mueller, Niklaus H; Teramoto, Tadahisa; Padmanabhan, R</p> <p>2009-05-01</p> <p>Detergents such as Triton X-100 are often used in drug discovery research to weed out small molecule promiscuous and non-specific inhibitors which act by aggregation in solution and undesirable precipitation in aqueous assay buffers. We evaluated the effects of commonly used detergents, Triton X-100, Tween-20, Nonidet-40 (NP-40), Brij-35, and CHAPS, on the enzymatic <span class="hlt">activity</span> of <span class="hlt">West</span> Nile virus (WNV) protease. Unexpectedly, Triton X-100, Tween-20, and NP-40 showed an enhancement of in vitro WNV protease <span class="hlt">activity</span> from 2 to 2.5-fold depending on the detergent and its concentration. On the other hand, Brij-35, at 0.001% enhanced the protease <span class="hlt">activity</span> by 1.5-fold and CHAPS had the least enhancing effect. The kinetic analysis showed that the increase in protease <span class="hlt">activity</span> by Triton X-100 was dose-dependent. Furthermore, at Triton X-100 and Tween-20 concentrations higher than 0.001%, the inhibition of compound B, one of the lead compounds against WNV protease identified in a high throughput screen (IC(50) value of 5.7+/-2.5 microM), was reversed. However, in the presence of CHAPS, compound B still showed good inhibition of WNV protease. Our results, taken together, indicate that nonionic detergents, Triton X-100, Tween, and NP-40 are unsuitable for the purpose of discrimination of true versus promiscuous inhibitors of WNV protease in high throughput assays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982AmSci..70..156C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982AmSci..70..156C"><span><span class="hlt">Antarctic</span> meteorites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cassidy, W. A.; Rancitelli, L. A.</p> <p>1982-04-01</p> <p>An abundance of meteorites has been discovered on two sites in the <span class="hlt">Antarctic</span> which may assist in the study of the origins of meteorites and the history of the solar system. Characteristics particular to those meteorites discovered in this region are explained. These specimens, being well preserved due to the climate, have implications in the study of the cosmic ray flux through time, the meteoroid complex in space, and cosmic ray exposure ages. Implications for the study of the <span class="hlt">Antarctic</span>, particularly the ice flow, are also discussed. Further discoveries of meteorites in this region are anticipated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11812052','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11812052"><span>Semipurification and ice recrystallization inhibition <span class="hlt">activity</span> of ice-<span class="hlt">active</span> substances associated with <span class="hlt">Antarctic</span> photosynthetic organisms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Raymond, J A; Fritsen, C H</p> <p>2001-08-01</p> <p>Ice-<span class="hlt">active</span> substances (IASs), i.e., macromolecular substances that modify the shape of growing ice crystals, were previously found to be associated with various terrestrial and aquatic photosynthetic organisms from Antarctica, but their chemical nature and function are unknown. In this study, we used the ice-binding properties of the IASs to semipurify IASs from a cyanobacterial mat, a eukaryotic green alga (Prasiola sp.), and a moss (Bryum sp.) and examined the ice recrystallization inhibition (RI) <span class="hlt">activities</span> of the semipure materials. The semipure materials contain both protein and carbohydrate in which the carbohydrate accounted for 73, 52, and 37%, respectively, of the total carbohydrate + protein. The IASs had RI <span class="hlt">activity</span> at concentrations of 1.4, 0.05, and 0.01 microg ml-1, respectively. RI <span class="hlt">activity</span> was greatly reduced by heat treatment, suggesting that the IASs inhibit recrystallization through a specific interaction with ice. These results raise the possibility that the IASs increase freezing tolerance of their respective organisms by preventing the recrystallization of ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMED22A..08A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMED22A..08A"><span>Field Training <span class="hlt">Activities</span> for Hydrologic Science in <span class="hlt">West</span> Java, Indonesia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agustina, C.; Fajri, P. N.; Fathoni, F.; Gusti, T. P.; Harifa, A. C.; Hendra, Y.; Hertanti, D. R.; Lusiana, N.; Rohmat, F. I.; Agouridis, C.; Fryar, A. E.; Milewski, A.; Pandjaitan, N.; Santoso, R.; Suharyanto, A.</p> <p>2013-12-01</p> <p>In hydrologic science and engineering, one challenge is establishing a common framework for discussion among workers from different disciplines. As part of the 'Building Opportunity Out of Science and Technology: Helping Hydrologic Outreach (BOOST H2O)' project, which is supported by the U.S. Department of State, nine current or recent graduate students from four Indonesian universities participated in a week of training <span class="hlt">activities</span> during June 2013. Students had backgrounds in agricultural engineering, civil and environmental engineering, water resources engineering, natural resources management, and soil science. Professors leading the training, which was based at Bogor Agricultural University (IPB) in <span class="hlt">west</span> Java, included an agricultural engineer, civil engineers, and geologists. <span class="hlt">Activities</span> in surface-water hydrology included geomorphic assessment of streams (measuring slope, cross-section, and bed-clast size) and gauging stream flow (wading with top-setting rods and a current meter for a large stream, and using a bucket and stopwatch for a small stream). Groundwater-hydrology <span class="hlt">activities</span> included measuring depth to water in wells, conducting a pumping test with an observation well, and performing vertical electrical soundings to infer hydrostratigraphy. Students also performed relatively simple water-quality measurements (temperature, electrical conductivity, pH, and alkalinity) in streams, wells, and springs. The group analyzed data with commercially-available software such as AQTESOLV for well hydraulics, freeware such as the U.S. Geological Survey alkalinity calculator, and Excel spreadsheets. Results were discussed in the context of landscape position, lithology, and land use.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16038407','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16038407"><span>Temperature differentially affects adenosine triphosphatase <span class="hlt">activity</span> in Hsc70 orthologs from <span class="hlt">Antarctic</span> and New Zealand notothenioid fishes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Place, Sean P; Hofmann, Gretchen E</p> <p>2005-01-01</p> <p>To test the temperature sensitivity of molecular chaperones in poikilothermic animals, we purified the molecular chaperone Hsc70 from 2 closely related notothenioid fishes--the <span class="hlt">Antarctic</span> species Trematomus bernacchii and the temperate New Zealand species Notothenia angustata--and characterized the effect of temperature on Hsc70 adenosine triphosphatase (ATPase) <span class="hlt">activity</span>. Hsc70 ATPase <span class="hlt">activity</span> was measured using [alpha-32P]-adenosine triphosphate (ATP)-based in vitro assays followed by separation of adenylates by thin-layer chromatography. For both species, a significant increase in Hsc70 ATPase <span class="hlt">activity</span> was observed across a range of temperatures that was ecologically relevant for each respective species. Hsc70 from T bernacchii hydrolyzed 2-fold more ATP than did N angustata Hsc70 at 0 degrees C, suggesting that the <span class="hlt">Antarctic</span> molecular chaperone may be adapted to function more efficiently at extreme cold temperatures. In addition, Q10 measurements indicate differential temperature sensitivity of the ATPase <span class="hlt">activity</span> of Hsc70 from these differentially adapted fish that correlates with the temperature niche inhabited by each species. Hsc70 from T bernacchii was relatively temperature insensitive, as indicated by Q10 values calculated near 1.0 across each temperature range measured. In the case of Hsc70 purified from N angustata, Q10 values indicated thermal sensitivity across the temperature range of 0 degrees C to 10 degrees C, with a Q10 of 2.714. However, Hsc70 from both T bernacchii and N angustata exhibited unusually high thermal stabilities with ATPase <span class="hlt">activity</span> at temperatures that far exceeded temperatures encountered by these fish in nature. Overall, as evidenced by in vitro ATP hydrolysis, Hsc70 from T bernacchii and N angustata displayed biochemical characteristics that were supportive of molecular chaperone function at ecologically relevant temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/fs/2001/0051/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/fs/2001/0051/report.pdf"><span>United States <span class="hlt">Antarctic</span> Resource Center (USARC)</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>,</p> <p>2001-01-01</p> <p>The U.S. <span class="hlt">Antarctic</span> Resource Center (USARC) is our Nation?s depository for <span class="hlt">Antarctic</span> maps, charts, geodetic ground control, satellite images, aerial photographs, publications, slides, and video tapes. These resources are items produced by <span class="hlt">Antarctic</span> Treaty nations in support of their <span class="hlt">activities</span> in Antarctica and provided to the USARC in compliance with a standing resolution of the treaty providing for exchange of information. The U.S. Geological Survey (USGS) maintains these materials through an interagency cooperative agreement with the National Science Foundation (NSF), which also supports the USGS <span class="hlt">Antarctic</span> Mapping Program. The USARC develops and maintains the <span class="hlt">Antarctic</span> Web site (usarc.usgs.gov) and its supporting data bases, as well as providing access to other online digital data bases, such as the Atlas of <span class="hlt">Antarctic</span> Resources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6463795','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6463795"><span>Numerical model of circumpolar <span class="hlt">Antarctic</span> ice shelves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Johnson, R.C.</p> <p>1985-01-01</p> <p>Extensive floating ice shelves in the <span class="hlt">Antarctic</span> have been proposed to explain the discrepancies between Pleistocene high sea levels shown by dated coral reefs and coeval low sea levels inferred from glacial ice volumes calculated from oxygen isotope ratios in deep sea cores. A numerical model using the floating shelf creep analysis of Weertman (1957) has provided a plausible basis for the acceptance of such shelves. Shelf outer limits were set at 55/sup 0/S in East Antarctica and 58/sup 0/S in <span class="hlt">West</span> Antarctica, based in part on diatom-deficient deep sea sediments deposited prior to the Holocene. Precipitation varied from 10 gm cm/sup -2/yr/sup -1/ at 75/sup 0/S to 80 gm cm/sup -2/yr/sup -1/ at 55/sup 0/S. Mean air temperatures varied from -35/sup 0/C at the 75/sup 0/S coast to -17/sup 0/C at the outer limits. Isotope ratios were those of present <span class="hlt">Antarctic</span> precipitation at corresponding model shelf temperatures. In the calculation, a steady state is assumed. Integration begins at the coast with summation over successive years as creep and continental ice discharge move the integration element to the outer limits. The oceanic oxygen isotope ratio change required by the discrepancies in the record is 0.40 to 0.50 ppmil. Using the flow law constant of 4.2 and a creep <span class="hlt">activation</span> energy of 134 kjoules mol/sup -1/, the resulting change is 0.44 ppmil. Difference results reflect the uncertainties associated with the critical creep constants used in the modeling. Nevertheless, the results suggest that a quantity of <span class="hlt">Antarctic</span> shelf ice comparable to ice volumes in major Northern glacial areas existed at times during the Pleistocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3509122','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3509122"><span>Solution Structures, Dynamics, and Ice Growth Inhibitory <span class="hlt">Activity</span> of Peptide Fragments Derived from an <span class="hlt">Antarctic</span> Yeast Protein</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Asmawi, Azren A.; Rahman, Mohd Basyaruddin A.; Murad, Abdul Munir A.; Mahadi, Nor M.; Basri, Mahiran; Rahman, Raja Noor Zaliha A.; Salleh, Abu B.; Chatterjee, Subhrangsu; Tejo, Bimo A.; Bhunia, Anirban</p> <p>2012-01-01</p> <p>Exotic functions of antifreeze proteins (AFP) and antifreeze glycopeptides (AFGP) have recently been attracted with much interest to develop them as commercial products. AFPs and AFGPs inhibit ice crystal growth by lowering the water freezing point without changing the water melting point. Our group isolated the <span class="hlt">Antarctic</span> yeast Glaciozyma antarctica that expresses antifreeze protein to assist it in its survival mechanism at sub-zero temperatures. The protein is unique and novel, indicated by its low sequence homology compared to those of other AFPs. We explore the structure-function relationship of G. antarctica AFP using various approaches ranging from protein structure prediction, peptide design and antifreeze <span class="hlt">activity</span> assays, nuclear magnetic resonance (NMR) studies and molecular dynamics simulation. The predicted secondary structure of G. antarctica AFP shows several α-helices, assumed to be responsible for its antifreeze <span class="hlt">activity</span>. We designed several peptide fragments derived from the amino acid sequences of α-helical regions of the parent AFP and they also showed substantial antifreeze <span class="hlt">activities</span>, below that of the original AFP. The relationship between peptide structure and <span class="hlt">activity</span> was explored by NMR spectroscopy and molecular dynamics simulation. NMR results show that the antifreeze <span class="hlt">activity</span> of the peptides correlates with their helicity and geometrical straightforwardness. Furthermore, molecular dynamics simulation also suggests that the <span class="hlt">activity</span> of the designed peptides can be explained in terms of the structural rigidity/flexibility, i.e., the most <span class="hlt">active</span> peptide demonstrates higher structural stability, lower flexibility than that of the other peptides with lower <span class="hlt">activities</span>, and of lower rigidity. This report represents the first detailed report of downsizing a yeast AFP into its peptide fragments with measurable antifreeze <span class="hlt">activities</span>. PMID:23209600</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2447445','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2447445"><span><span class="hlt">Antarctic</span> Genomics</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clarke, Andrew; Cockell, Charles S.; Convey, Peter; Detrich III, H. William; Fraser, Keiron P. P.; Johnston, Ian A.; Methe, Barbara A.; Murray, Alison E.; Peck, Lloyd S.; Römisch, Karin; Rogers, Alex D.</p> <p>2004-01-01</p> <p>With the development of genomic science and its battery of technologies, polar biology stands on the threshold of a revolution, one that will enable the investigation of important questions of unprecedented scope and with extraordinary depth and precision. The exotic organisms of polar ecosystems are ideal candidates for genomic analysis. Through such analyses, it will be possible to learn not only the novel features that enable polar organisms to survive, and indeed thrive, in their extreme environments, but also fundamental biological principles that are common to most, if not all, organisms. This article aims to review recent developments in <span class="hlt">Antarctic</span> genomics and to demonstrate the global context of such studies. PMID:18629155</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005EOSTr..86..293S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005EOSTr..86..293S"><span><span class="hlt">Antarctic</span> science</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Summerhayes, Colin</p> <p></p> <p>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-<span class="hlt">Antarctic</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21673897','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21673897"><span>Screening of microorganisms producing cold-<span class="hlt">active</span> oxidoreductases to be applied in enantioselective alcohol oxidation. An <span class="hlt">Antarctic</span> survey.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Araújo, Lidiane S; Kagohara, Edna; Garcia, Thaís P; Pellizari, Vivian H; Andrade, Leandro H</p> <p>2011-01-01</p> <p>Several microorganisms were isolated from soil/sediment samples of <span class="hlt">Antarctic</span> Peninsula. The enrichment technique using (RS)-1-(phenyl)ethanol as a carbon source allowed us to isolate 232 psychrophile/psychrotroph microorganisms. We also evaluated the enzyme <span class="hlt">activity</span> (oxidoreductases) for enantioselective oxidation reactions, by using derivatives of (RS)-1-(phenyl)ethanol as substrates. Among the studied microorganisms, 15 psychrophile/psychrotroph strains contain oxidoreductases that catalyze the (S)-enantiomer oxidation from racemic alcohols to their corresponding ketones. Among the identified microorganisms, Flavobacterium sp. and Arthrobacter sp. showed excellent enzymatic <span class="hlt">activity</span>. These new bacteria strains were selected for optimization study, in which the (RS)-1-(4-methyl-phenyl)ethanol oxidation was evaluated in several reaction conditions. From these studies, it was observed that Flavobacterium sp. has an excellent enzymatic <span class="hlt">activity</span> at 10 °C and Arthrobacter sp. at 15 and 25 °C. We have also determined the growth curves of these bacteria, and both strains showed optimum growth at 25 °C, indicating that these bacteria are psychrotroph.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC42B..06B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC42B..06B"><span>Robust Decision Making and Scenario Based Engineering Hazard Analysis Regarding the Potential Abrupt Sea-Level Rise from a Collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet: An Overview Paper</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berner, D. E.</p> <p>2012-12-01</p> <p>Recently scientific researchers have made significant advances in better understanding the risks of abrupt sea-level rise, SLR, but they have not adequately conveyed this understanding to decision makers who need to have sufficient information to decide what actions to take. The state-of-the-art in SLR projection is currently not sufficient to provide fully probabilistic risk functions to decision makers. Nevertheless, using the tools of Robust Decision Making, RDM, and Scenario Based Engineering Hazard Analysis, SBEHA, this article will present sufficient information to characterize a Maximum Credible Event, MCE, for abrupt SLR this century to allow decision makers to better understand the risks and timing that they are facing from the potential collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet, WAIS, coupled together with other concurrent dynamic ice mass loss events. The article presents an overview of published research related topics including: paleo-evidence regarding abrupt SLR; radiative forcing scenarios; both RDM and SBEHA methodologies; and direct cause and effect evidence of an MCE scenario for the potential partial, or full, collapse of the WAIS the century. Findings of the article are presented in the form of summary graphs of projected relative sea-level rise, RSLR, and probability density functions, PDFs, for California.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992EOSTr..73..194S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992EOSTr..73..194S"><span><span class="hlt">Antarctic</span> science preserve polluted</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simarski, Lynn Teo</p> <p></p> <p>Geophysicists are alarmed at the electromagnetic pollution of a research site in the <span class="hlt">Antarctic</span> specifically set aside to study the ionosphere and magnetosphere. A private New Zealand communications company called Telecom recently constructed a satellite ground station within the boundaries of this Site of Special Scientific Interest (SSSI), protected since the mid-1970s. The placement of a commercial facility within this site sets an ominous precedent not only for the sanctity of other SSSIs, but also for Specially Protected Areas—preserves not even open to scientific research, such as certain penguin rookeries.The roughly rectangular, one-by-one-half mile site, located at Arrival Heights not far from McMurdo Station, is one of a number of areas protected under the <span class="hlt">Antarctic</span> treaty for designated scientific <span class="hlt">activities</span>. Many sites are set aside for geological or biological research, but this is the only one specifically for physical science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950004548&hterms=Koeberl&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D10%26Ntt%3DKoeberl','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950004548&hterms=Koeberl&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D10%26Ntt%3DKoeberl"><span><span class="hlt">Antarctic</span> micrometeorites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kurat, G.; Koeberl, C.; Presper, T.; Brandstaetter, F.; Maurette, Michel</p> <p>1994-01-01</p> <p>Micrometeoroids in the size range 50-500 micron dominate the flux onto the Earth. Contrary to theoretical predictions, many of them survive atmospheric entry almost unchanged. Such micrometeorites can be collected from the <span class="hlt">Antarctic</span> ice sheet where they account for a surprisingly large proportion of the total dust content of the ice. Early studies of this important class of extraterrestrial material have revealed that some <span class="hlt">Antarctic</span> micrometeorites are similar to CM chondrites in chemical bulk composition and mineral composition, and a few seem to resemble CI chondrites. However, none of the micrometeorites investigated so far match CM or CI chondrites exactly, nor is there a match between average bulk micrometeorite composition and that of any other chondrite class. Also, the micrometeorite mineral chemistry is different from that of carbonaceous chondrites. Several elements are depleted in micrometeorites as compared to carbonaceous chondrites and some are enriched. The question arises whether these differences are pristine or if some of them are of secondary origin. On the basis of our data we will attempt to answer these questions, some of which have been addressed by us before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3499239','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3499239"><span>Diversity and extracellular enzymatic <span class="hlt">activities</span> of yeasts isolated from King George Island, the sub-<span class="hlt">Antarctic</span> region</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2012-01-01</p> <p>Background Antarctica has been successfully colonized by microorganisms despite presenting adverse conditions for life such as low temperatures, high solar radiation, low nutrient availability and dryness. Although these “cold-loving” microorganisms are recognized as primarily responsible for nutrient and organic matter recycling/mineralization, the yeasts, in particular, remain poorly characterized and understood. The aim of this work was to study the yeast microbiota in soil and water samples collected on King George Island. Results A high number of yeast isolates was obtained from 34 soil and 14 water samples. Molecular analyses based on rDNA sequences revealed 22 yeast species belonging to 12 genera, with Mrakia and Cryptococcus genera containing the highest species diversity. The species Sporidiobolus salmonicolor was by far the most ubiquitous, being identified in 24 isolates from 13 different samples. Most of the yeasts were psychrotolerant and ranged widely in their ability to assimilate carbon sources (consuming from 1 to 27 of the 29 carbon sources tested). All species displayed at least 1 of the 8 extracellular enzyme <span class="hlt">activities</span> tested. Lipase, amylase and esterase <span class="hlt">activity</span> dominated, while chitinase and xylanase were less common. Two yeasts identified as Leuconeurospora sp. and Dioszegia fristingensis displayed 6 enzyme <span class="hlt">activities</span>. Conclusions A high diversity of yeasts was isolated in this work including undescribed species and species not previously isolated from the <span class="hlt">Antarctic</span> region, including Wickerhamomyces anomalus, which has not been isolated from cold regions in general. The diversity of extracellular enzyme <span class="hlt">activities</span>, and hence the variety of compounds that the yeasts may degrade or transform, suggests an important nutrient recycling role of microorganisms in this region. These yeasts are of potential use in industrial applications requiring high enzyme <span class="hlt">activities</span> at low temperatures. PMID:23131126</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22243336','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22243336"><span>Influence of organic matter content and human <span class="hlt">activities</span> on the occurrence of organic pollutants in <span class="hlt">antarctic</span> soils, lichens, grass, and mosses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cabrerizo, Ana; Dachs, Jordi; Barceló, Damià; Jones, Kevin C</p> <p>2012-02-07</p> <p>Banned pesticides such as HCB and p,p'-DDE, and other legacy and ongoing pollutants such as PCBs and PAHs, were measured in different vegetation types and soil samples collected at selected areas from <span class="hlt">Antarctic</span> Peninsula (Deception and Livingstone Islands, Southern Shetlands). Two <span class="hlt">Antarctic</span> expeditions (in 2005 and 2009) were carried out to assess POPs levels at remote areas, and close to current and abandoned <span class="hlt">Antarctic</span> research settlements, to assess potential sources of pollutants. Overall, the patterns in lichens, mosses, and grass were dominated by low molecular PCB congeners and PAHs and the presence of HCB and p,p'-DDE rather than heavier compounds, suggesting the importance of long-range atmospheric transport of POPs as the main vector for the introduction of these chemicals to Antarctica. Statistically significant correlations (p-level < 0.05) between concentrations in vegetation of PCBs, p,p'-DDE, and the more volatile PAHs with lipid content were found with r(2) of 0.22-0.52 for PCBs, 0.42 for p,p'-DDE, and 0.44-0.72 for the more volatile PAHs. Thus, lipid content is an important factor controlling POPs in <span class="hlt">Antarctic</span> lichens, mosses, and grass. A strong significant dependence of HCB (r(2) = 0.83), p,p'-DDE (r(2) = 0.60), and PCBs (r(2) = 0.36-0.47) concentrations in soil on its organic carbon content was also observed, indicating the important role of soil organic matter (SOM) in the retention of PCBs and OCPs in Polar Regions, where SOM content is low. Penguin colonies enhance the SOM content in some areas which is reflected in higher concentrations of all POPs, especially of persistent compounds such as p,p'-DDE. Higher concentrations of PCBs and PAHs found at the currently <span class="hlt">active</span> Byers Camp (in an <span class="hlt">Antarctic</span> Specially Protected Area) were explained by higher SOM content, thus indicating that <span class="hlt">Antarctic</span> regulations are being successfully fulfilled in this small research area. On the other hand, PAHs in soils proximate to current Juan Carlos I research</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18765160','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18765160"><span>Environmental contamination in <span class="hlt">Antarctic</span> ecosystems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bargagli, R</p> <p>2008-08-01</p> <p>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-<span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> environment are transported from other continents in the Southern Hemisphere. At present, levels of most contaminants in <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> environment. Although the Protocol on Environmental Protection to the <span class="hlt">Antarctic</span> Treaty provides strict guidelines for the protection of the <span class="hlt">Antarctic</span> environment and establishes obligations for all human <span class="hlt">activity</span> in the continent and the Southern Ocean, global warming, population growth and industrial development in countries of the Southern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23945585','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23945585"><span>Onset of deglacial warming in <span class="hlt">West</span> Antarctica driven by local orbital forcing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2013-08-22</p> <p>The cause of warming in the Southern Hemisphere during the most recent deglaciation remains a matter of debate. Hypotheses for a Northern Hemisphere trigger, through oceanic redistributions of heat, are based in part on the abrupt onset of warming seen in East <span class="hlt">Antarctic</span> ice cores and dated to 18,000 years ago, which is several thousand years after high-latitude Northern Hemisphere summer insolation intensity began increasing from its minimum, approximately 24,000 years ago. An alternative explanation is that local solar insolation changes cause the Southern Hemisphere to warm independently. Here we present results from a new, annually resolved ice-core record from <span class="hlt">West</span> Antarctica that reconciles these two views. The records show that 18,000 years ago snow accumulation in <span class="hlt">West</span> Antarctica began increasing, coincident with increasing carbon dioxide concentrations, warming in East Antarctica and cooling in the Northern Hemisphere associated with an abrupt decrease in Atlantic meridional overturning circulation. However, significant warming in <span class="hlt">West</span> Antarctica began at least 2,000 years earlier. Circum-<span class="hlt">Antarctic</span> sea-ice decline, driven by increasing local insolation, is the likely cause of this warming. The marine-influenced <span class="hlt">West</span> <span class="hlt">Antarctic</span> records suggest a more <span class="hlt">active</span> role for the Southern Ocean in the onset of deglaciation than is inferred from ice cores in the East <span class="hlt">Antarctic</span> interior, which are largely isolated from sea-ice changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70048748','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70048748"><span>Onset of deglacial warming in <span class="hlt">West</span> Antarctica driven by local orbital forcing</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>WAIS Divide Project Members,; Steig, Eric J.; Markle, Bradley R.; Schoenemann, Spruce W.; Ding, Qinghua; Taylor, Kendrick C.; McConnell, Joseph R.; Brook, Edward J.; Sowers, Todd; White, James W. C.; Alley, Richard B.; Chen, Hai; Clow, Gary D.; Cole-Dai, Jihong; Conway, Howard; Fitzpatrick, Joan J.; Hargreaves, Geoffrey; ,</p> <p>2013-01-01</p> <p>The cause of warming in the Southern Hemisphere during the most recent deglaciation remains a matter of debate. Hypotheses for a Northern Hemisphere trigger, through oceanic redistributions of heat, are based in part on the abrupt onset of warming seen in East <span class="hlt">Antarctic</span> ice cores and dated to 18,000 years ago, which is several thousand years after high-latitude Northern Hemisphere summer insolation intensity began increasing from its minimum, approximately 24,000 years ago. An alternative explanation is that local solar insolation changes cause the Southern Hemisphere to warm independently. Here we present results from a new, annually resolved ice-core record from <span class="hlt">West</span> Antarctica that reconciles these two views. The records show that 18,000 years ago snow accumulation in <span class="hlt">West</span> Antarctica began increasing, coincident with increasing carbon dioxide concentrations, warming in East Antarctica and cooling in the Northern Hemisphere associated with an abrupt decrease in Atlantic meridional overturning circulation. However, significant warming in <span class="hlt">West</span> Antarctica began at least 2,000 years earlier. Circum-<span class="hlt">Antarctic</span> sea-ice decline, driven by increasing local insolation, is the likely cause of this warming. The marine-influenced <span class="hlt">West</span> <span class="hlt">Antarctic</span> records suggest a more <span class="hlt">active</span> role for the Southern Ocean in the onset of deglaciation than is inferred from ice cores in the East <span class="hlt">Antarctic</span> interior, which are largely isolated from sea-ice changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21706933','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21706933"><span>Dusk to dawn <span class="hlt">activity</span> patterns of anopheline mosquitoes in <span class="hlt">West</span> Timor and Java, Indonesia.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ndoen, Ermi; Wild, Clyde; Dale, Pat; Sipe, Neil; Dale, Mike</p> <p>2011-05-01</p> <p>Malaria is a serious health issue in Indonesia. We investigated the dusk to dawn anopheline mosquito <span class="hlt">activity</span> patterns, host-seeking and resting locations in coastal plain, hilly and highland areas in <span class="hlt">West</span> Timor and Java. Adult mosquitoes were captured landing on humans or resting in houses or animal barns. Data analyzed were: mosquito night-time <span class="hlt">activities</span>; period of peak <span class="hlt">activity</span>; night-time <span class="hlt">activity</span> in specific periods of time and for mosquito resting locations. Eleven species were recorded; data were sparse for some species therefore detailed analyses were performed for four species only. In Java Anopheles vagus was common, with a bimodal pattern of high <span class="hlt">activity</span>. In <span class="hlt">West</span> Timor, its <span class="hlt">activity</span> peaked around midnight. Other species with peak <span class="hlt">activity</span> around the middle of the night were An. barbirostris and An. subpictus. Most species showed no biting and resting preference for indoors or outdoors, although An. barbirostris preferred indoors in <span class="hlt">West</span> Timor, but outdoors in Java. An. aconitus and An. annularis preferred resting in human dwellings; An. subpictus and An. vagus preferred resting in animal barns. An. barbirostris preferred resting in human dwellings in <span class="hlt">West</span> Timor and in animal barns in Java. The information is useful for planning the mosquito control aspect of malaria management. For example, where mosquito species have peak <span class="hlt">activity</span> at night indoors, bednets and indoor residual spraying should reduce malaria risk, but where mosquitoes are most <span class="hlt">active</span> outdoors, other options may be more effective.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25435506','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25435506"><span>Identification of lipase encoding genes from <span class="hlt">Antarctic</span> seawater bacteria using degenerate primers: expression of a cold-<span class="hlt">active</span> lipase with high specific <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Parra, Loreto P; Espina, Giannina; Devia, Javier; Salazar, Oriana; Andrews, Barbara; Asenjo, Juan A</p> <p>2015-01-01</p> <p>Cold-<span class="hlt">active</span> enzymes are valuable catalysts showing high <span class="hlt">activity</span> at low and moderate temperatures and low thermostability. Among cold-<span class="hlt">active</span> enzymes, lipases offer a great potential in detergent, cosmetic, biofuel and food or feed industries. In this paper we describe the identification of novel lipase coding genes and the expression of a lipase with high <span class="hlt">activity</span> at low temperatures. The genomic DNA from <span class="hlt">Antarctic</span> seawater bacteria showing lipolytic <span class="hlt">activity</span> at 4°C was used to amplify five DNA fragments that partially encode novel lipases using specifically designed COnsensus-DEgenerate Hybrid Oligonucleotide Primers (CODEHOP). All the fragments were found to have a high identity with an α/β-hydrolase domain-containing protein identified by the sequencing of the complete genome of Shewanella frigidimarina NCIMB 400. The complete sequence of one of the lipase-coding gene fragments, lipE13, was obtained by genome walking. Considering that the other fragments had a high identity to the putative lipase from S. frigidimarina NCIMB 400, the complete lipase genes were amplified using oligonucleotide primers designed based on the 5' and 3' regions of the coding sequence of the related protein. This strategy allowed the amplification of 3 lipase-encoding genes of which one was expressed in the periplasm using the Escherichia coli BL21(DE3)/pET-22b(+) expression system. The recombinant protein was obtained with <span class="hlt">activity</span> toward p-nitrophenyl caproate showing a high specific <span class="hlt">activity</span> between 15 and 25°C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55.2068V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55.2068V"><span>Primary production within the sea-ice zone <span class="hlt">west</span> of the <span class="hlt">Antarctic</span> Peninsula: I—Sea ice, summer mixed layer, and irradiance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vernet, Maria; Martinson, Douglas; Iannuzzi, Richard; Stammerjohn, Sharon; Kozlowski, Wendy; Sines, Karie; Smith, Ray; Garibotti, Irene</p> <p>2008-09-01</p> <p>In shelf waters of the western <span class="hlt">Antarctic</span> Peninsula (wAP), with abundant macro- and micronutrients, water-column stability has been suggested as the main factor controlling primary production; freshwater input from sea-ice melting stabilizes the upper water column by forming a shallow summer mixed layer. Retreating sea ice in the spring and summer thus defines the area of influence, the sea-ice zone (SIZ) and the marginal ice zone (MIZ). A 12-year time series (1995-2006) was analyzed to address two main questions: (1) what are the spatial and temporal patterns in primary production; and (2) to what extent and in what ways is primary production related to sea-ice dynamics. Data were collected on cruises performed during January of each year, at the height of the growth season, within the region bounded by 64°S and 64°W to the north and 68°S and 66°W to the south. Average daily integrated primary production varied by an order of magnitude, from ˜250 to ˜1100 mg C m -2 d -1, with an average cruise primary production of 745 mg C m -2 d -1. A strong onshore-offshore gradient was evident along the shelf with higher production observed inshore. Inter-annual regional production varied by a factor of 7: maximum rates were measured in 2006 (1788 mg C m -2 d -1) and minimum in 1999 (248 mg C m -2 d -1). The results support the hypothesis that primary production in the wAP shelf is related to sea-ice dynamics. To first order, shallower summer mixed-layer depths in the shelf correlated with late sea retreat and primary production. Principal component analysis showed that high primary production in January was associated with enhanced shelf production toward the coast and in the south, explaining 63% of the variability in space and time. This first mode captured the inter-annual variability in regional production. Temporal variability in primary production (time series of anomalies defined for each location) showed spatial dependence: higher primary production correlated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26601753','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26601753"><span>Bacterial diversity is strongly associated with historical penguin <span class="hlt">activity</span> in an <span class="hlt">Antarctic</span> lake sediment profile.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhu, Renbin; Shi, Yu; Ma, Dawei; Wang, Can; Xu, Hua; Chu, Haiyan</p> <p>2015-11-25</p> <p>Current penguin <span class="hlt">activity</span> in Antarctica affects the geochemistry of sediments and their microbial communities; the effects of historical penguin <span class="hlt">activity</span> are less well understood. Here, bacterial diversity in ornithogenic sediment was investigated using high-throughput pyrosequencing. The relative abundances of dominant phyla were controlled by the amount of historical penguin guano deposition. Significant positive correlations were found between both the bacterial richness and diversity, and the relative penguin number (p < 0.01); this indicated that historical penguin <span class="hlt">activity</span> drove the vertical distribution of the bacterial communities. The lowest relative abundances of individual phyla corresponded to lowest number of penguin population at 1,800-2,300 yr BP during a drier and colder period; the opposite was observed during a moister and warmer climate (1,400-1,800 yr BP). This study shows that changes in the climate over millennia affected penguin populations and the outcomes of these changes affect the sediment bacterial community today.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B11H0133M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B11H0133M"><span>Higher Temperature and Hydrogen Availability Stimulated the Methanogenic <span class="hlt">Activity</span> in East <span class="hlt">Antarctic</span> Subglacial Sediment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, H.</p> <p>2014-12-01</p> <p>Subglacial ecosystem has been recognized as an environment with considerable methanogenic <span class="hlt">activity</span>, and therefore is of significant impact on global methane budget and climate change. Although the methanogens have been discovered at a few subglacial environments, the methanogenic <span class="hlt">activity</span> there is yet insufficiently studied, especially on the effects of environmental parameters, due to technical difficulties on sampling and cultivation. Here, in this study, we attempt to access the methanogenic <span class="hlt">activity</span> and community structure in response to temperature and substrate availability. An integrated approach including in vitro cultivation and molecular techniques were employed. A subglacial sediment from Larsemann Hills, East Antarctica was incubated at different temperatures (1, 4, 12 oC) supplied with H2+CO2 or sodium acetate to estimate the methanogenic <span class="hlt">activity</span>. The McrA gene which is a specific marker for methanogens was amplified with primer ME and ML to construct phylogenetic trees. This functional gene was also quantified by Q-PCR before and after the incubation to estimate the increase of methanogens. After 8 months a highest methanogenesis rate of 226 pmol/ day/ gram sediment was observed at 12 oC with H2 supplying, which was 2 times higher than that with acetate supplying, clearly suggesting that H2 is a preferable substrate than acetate. The methanogenesis rate without supplying extra substrate showed positive temperature dependence with rate of 23.3, 24.8, 131 pmol/day/gram sediment at 1 oC, 4 oC, and 12 oC, respectively. The McrA copy number was increased more than 300 times and 50 times with H2 and acetate supplying respectively after the incubation. 94% and 67% of the mcrA gene sequences were classed into methanomicrobiales which were hydrogen-trophic methanogens in the two clone libraries with primer ML and ME respectively. This finding suggests the potential effect of methanogenesis under glacier on the climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25770668','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25770668"><span>Variation in blood serum antifreeze <span class="hlt">activity</span> of <span class="hlt">Antarctic</span> Trematomus fishes across habitat temperature and depth.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fields, Lauren G; DeVries, Arthur L</p> <p>2015-07-01</p> <p>High latitude waters in the Southern Ocean can be near their freezing point and remain ice-covered throughout the year whereas lower latitude Southern Ocean waters have seasonal ice coverage and comparatively large (6 °C) annual temperature changes. The genus Trematomus (suborder Notothenioidei) is regarded primarily as a high latitude group because of its abundance there, they also inhabit the warmer regions in smaller numbers. Freeze avoidance in the notothenioids is linked to the presence of two antifreeze proteins (AFPs); the antifreeze glycoproteins (AFGPs) and antifreeze potentiating protein (AFPP), both of which adsorb to internal ice crystals inhibiting growth. Both high and low latitude trematomids possess sufficient AFP to lower their blood freezing point below that of seawater (-1.9 °C). We investigated the contributions of AFGPs and AFPP to the blood freezing point depression to determine how they varied with depth, water temperature, and the presence of ice. High latitude trematomids had lower blood freezing points than those inhabiting lower latitude waters indicating differences in their freeze avoidance capacities. Lower freezing points were associated with higher levels of antifreeze <span class="hlt">activity</span> due to higher levels of both AFGP and AFPP. Populations of Trematomus hansoni and Trematomus bernacchii from shallow depths appear more freeze avoidant than populations inhabiting deep, ice-free water based on their lower freezing points and higher antifreeze <span class="hlt">activities</span>. Gel electrophoresis of the trichloroacetic acid-soluble AFGPs indicates that only high molecular weight isoforms, which contribute more to AFGP <span class="hlt">activity</span>, vary across species as well as between individuals of a species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title33-vol3/pdf/CFR-2010-title33-vol3-sec334-762.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title33-vol3/pdf/CFR-2010-title33-vol3-sec334-762.pdf"><span>33 CFR 334.762 - Naval Support <span class="hlt">Activity</span> Panama City; North Bay and <span class="hlt">West</span> Bay; restricted areas.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-07-01</p> <p>... City; North Bay and <span class="hlt">West</span> Bay; restricted areas. 334.762 Section 334.762 Navigation and Navigable Waters... REGULATIONS § 334.762 Naval Support <span class="hlt">Activity</span> Panama City; North Bay and <span class="hlt">West</span> Bay; restricted areas. (a) The..., Naval Support <span class="hlt">Activity</span>, Panama City Florida, and such agencies as he/she may designate....</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED238768.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED238768.pdf"><span>The Mountain <span class="hlt">West</span> and the World: International Connections and Alternative Futures. A Handbook of 15 <span class="hlt">Activities</span> for Secondary Classrooms.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Smith, Gary R.; Bienstock, Eric M.</p> <p></p> <p><span class="hlt">Activities</span> to supplement secondary school global or future studies courses in the 10 state Mountain <span class="hlt">West</span> region are presented in this teacher handbook. Material is divided into 3 sections. Section 1, an introduction to international connectedness, contains 7 <span class="hlt">activities</span> focusing on the Mountain <span class="hlt">West</span>'s interdependence with the rest of the world. A…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4645823','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4645823"><span>Determinants of <span class="hlt">active</span> pulmonary tuberculosis in Ambo Hospital, <span class="hlt">West</span> Ethiopia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mengiste, Bezatu; Mesfin, Frehiwot; Godana, Wanzahun</p> <p>2015-01-01</p> <p>Objectives The aim of this study was to determine factors associated with <span class="hlt">active</span> pulmonary tuberculosis seen in cases in Ambo Hospital, Ethiopia. Design A facility-based prospective case-control study. Setting Patients attending Ambo Hospital from 01 December 2011 to 29 March 2012. Participants The sample included 312 adult patients attending Ambo Hospital. The main outcome measure was presence of <span class="hlt">active</span> pulmonary tuberculosis (TB). Explanatory measures Age, gender, occupation, educational status, marital status, place of residence, patient history of TB, family history of TB, human immunodeficiency virus (HIV) infection, smoking, alcohol intake, khat chewing, body mass index (BMI), employment, diabetes, history of asthma, previous history of worm infestation, history of hospitalisation, number of adults living in the household (HH), person per room, housing condition. Results A total of 312 study participants, including 104 <span class="hlt">active</span> pulmonary tuberculosis (PTB) cases (cases) and 208 non-<span class="hlt">active</span> PTB cases (controls), were recruited for the present study. Having one or more family member with a history of TB (OR = 4.4; 95% CI: 1.50–12.90), marital status (OR = 7.6; 95% CI: 2.2–12.6), male gender (OR = 3.2; 95% CI: 1.4–7), rural residence (OR = 3.3; P = 0.012), being a current or past smoker (OR = 2.8; 95% CI: 1.1–7.2), BMI < 18.5 (OR = 2.1; 95% CI: 1.03–4.2), HIV infection (OR = 8.8; 95% CI: 2.4–23.8) and a history of worm infestation (OR = 6.4; 95% CI: 2.6–15.4) remained significant independent host-related factors for <span class="hlt">active</span> PTB. Conclusion Patients who came from a compound with more than two HHs were more likely to develop <span class="hlt">active</span> PTB than those who came from a compound with only one HH. Those who lived in houses with no windows were more likely to develop <span class="hlt">active</span> PTB than those who lived in houses with one or more windows, had a family history of TB, lived in rural areas. Sex of the patient was a predicting factor. Not being the owner of the house was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880033433&hterms=Chlorine+Dioxide&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DChlorine%2BDioxide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880033433&hterms=Chlorine+Dioxide&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DChlorine%2BDioxide"><span><span class="hlt">Antarctic</span> stratospheric chemistry of chlorine nitrate, hydrogen chloride, and ice - Release of <span class="hlt">active</span> chlorine</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Molina, Mario J.; Tso, Tai-Ly; Molina, Luisa T.; Wang, Frank C.-Y.</p> <p>1987-01-01</p> <p>The reaction rate between atmospheric hydrogen chloride (HCl) and chlorine nitrate (ClONO2) is greatly enhanced in the presence of ice particles; HCl dissolves readily into ice, and the collisional reaction probability for ClONO2 on the surface of ice with HCl in the mole fraction range from about 0.003 to 0.010 is in the range from about 0.05 to 0.1 for temperatures near 200 K. Chlorine is released into the gas phase on a time scale of at most a few milliseconds, whereas nitric acid (HNO3), the other product, remains in the condensed phase. This reaction could play an important role in explaining the observed depletion of ozone over Antarctica; it releases photolytically <span class="hlt">active</span> chlorine from its most abundant reservoir species, and it promotes the formation of HNO3 and thus removes nitrogen dioxide from the gas phase. Hence it establishes the necessary conditions for the efficient catalytic destruction of ozone by halogenated free radicals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26108852','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26108852"><span>The changing form of <span class="hlt">Antarctic</span> biodiversity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chown, Steven L; Clarke, Andrew; Fraser, Ceridwen I; Cary, S Craig; Moon, Katherine L; McGeoch, Melodie A</p> <p>2015-06-25</p> <p><span class="hlt">Antarctic</span> 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 <span class="hlt">activities</span> and global environmental change nonetheless pose challenges to the current and future understanding of <span class="hlt">Antarctic</span> biodiversity. Life in the <span class="hlt">Antarctic</span> and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.7851B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.7851B"><span>First Year Observations of <span class="hlt">Antarctic</span> Circumpolar Current Variability and Internal Wave <span class="hlt">Activity</span> from the DIMES Mooring Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brearley, J. A.; Sheen, K. L.; Naveira-Garabato, A. C.</p> <p>2012-04-01</p> <p>A key component of DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean) is the deployment of a two-year cross-shaped mooring array in the <span class="hlt">Antarctic</span> Circumpolar Current to the east of Drake Passage close to 57°W. Motivation for the cluster arises from the need to understand how eddies dissipate in the Southern Ocean, and specifically how much energy is extracted from the mesoscale by breaking internal waves, which in turn leads to turbulent mixing. The location of the mooring cluster was chosen to fulfil these objectives, being situated in a region of pronounced finestructure with high eddy kinetic energy and rough topography. The array, comprising 34 current meters and Microcats and a downward-looking ADCP, was first deployed in December 2009 and serviced in December 2010. Time series of current meter results from the most heavily-instrumented 'C' mooring indicate that a strong (up to 80 cms-1) surface-intensified north-eastward directed ACC occupies the region for most of the year, with over 85% of the variability in current speed being accounted for by equivalent barotropic fluctuations. A strong mean poleward heat flux is observed at the site, which compares favourably in magnitude with literature results from other ACC locations. Interestingly, four episodes of mid-depth (~2000 m) current speed maxima, each of a few days duration, were found during the 360-day time series, a situation also observed by the lowered ADCP during mooring servicing in December 2010. Early results indicate that these episodes, which coincide with time minima in stratification close to 2000 m, could profoundly influence the nature of eddy-internal wave interactions at these times. Quantification of the energy budget at the mooring cluster has been a key priority. When compared with previous moorings located in Drake Passage (Bryden, 1977), a near threefold-increase in mean eddy kinetic energy (EKE) is observed despite a small reduction in the mean kinetic energy</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011DSRII..58.1407M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011DSRII..58.1407M"><span>Marine bacterioplankton biomass, <span class="hlt">activity</span> and community structure in the vicinity of <span class="hlt">Antarctic</span> icebergs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murray, Alison E.; Peng, Vivian; Tyler, Charlotte; Wagh, Protima</p> <p>2011-06-01</p> <p>We studied marine bacterioplankton in the Scotia Sea in June 2008 and in the northwest Weddell Sea in March to mid April 2009 in waters proximal to three free-drifting icebergs (SS-1, A-43k, and C-18a), in a region with a high density of smaller icebergs (iceberg alley), and at stations that were upstream of the iceberg trajectories designated as far-field reference sites that were between 16-75 km away. Hydrographic parameters were used to define water masses in which comparisons between bacterioplankton-associated characteristics (abundance, leucine incorporation into protein, aminopeptidase <span class="hlt">activities</span> and community structure) within and between water masses could be made. Early winter Scotia Sea bacterioplankton had low levels of cells and low heterotrophic production rates in the upper 50 m. Influences of the icebergs on bacterioplankton at this time of year were minimal, if not deleterious, as we found lower levels of heterotrophic production near A-43k in comparison to stations >16 km away. Additionally, the results point to small but significant differences in cell abundance, heterotrophic production, and community structure between the two icebergs studied. These icebergs differed greatly in size and the findings suggest that the larger iceberg had a greater effect. In the NW Weddell Sea in March-mid April bacterioplankton were twice as abundant and had heterotrophic productions rates that were 8-fold higher than what we determined in the Scotia Sea, though levels were still quite low, which is typical for autumn. We did not detect direct iceberg-related influences on the bacterioplankton characteristics studied here. Clues to understanding bacterioplankton responses may lie in the details of community structure, as there were some significant differences in community structure in the winter water and underlying upper circumpolar deep-water masses between stations occupied close to C-18a and at stations 18 km away (i.e. Polaribacter and Pelagibacter</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.1758H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.1758H"><span>Upper mantle structure of central and <span class="hlt">West</span> Antarctica from array analysis of Rayleigh wave phase velocities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heeszel, David S.; Wiens, Douglas A.; Anandakrishnan, Sridhar; Aster, Richard C.; Dalziel, Ian W. D.; Huerta, Audrey D.; Nyblade, Andrew A.; Wilson, Terry J.; Winberry, J. Paul</p> <p>2016-03-01</p> <p>The seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history of the continent and for understanding solid Earth interactions with the ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments to image the upper mantle structure of central and <span class="hlt">West</span> Antarctica. Phase velocity maps are determined using a two-plane wave tomography method and are inverted for shear velocity using a Monte Carlo approach to estimate three-dimensional velocity structure. Results illuminate the structural dichotomy between the East <span class="hlt">Antarctic</span> Craton and <span class="hlt">West</span> Antarctica, with <span class="hlt">West</span> Antarctica showing thinner crust and slower upper mantle velocity. <span class="hlt">West</span> Antarctica is characterized by a 70-100 km thick lithosphere, underlain by a low-velocity zone to depths of at least 200 km. The slowest anomalies are beneath Ross Island and the Marie Byrd Land dome and are interpreted as upper mantle thermal anomalies possibly due to mantle plumes. The central Transantarctic Mountains are marked by an uppermost mantle slow-velocity anomaly, suggesting that the topography is thermally supported. The presence of thin, higher-velocity lithosphere to depths of about 70 km beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System limits estimates of the regionally averaged heat flow to less than 90 mW/m2. The Ellsworth-Whitmore block is underlain by mantle with velocities that are intermediate between those of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift System and the East <span class="hlt">Antarctic</span> Craton. We interpret this province as Precambrian continental lithosphere that has been altered by Phanerozoic tectonic and magmatic <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988ocea...31...47M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988ocea...31...47M"><span>The <span class="hlt">Antarctic</span> ozone hole</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molina, Mario J.</p> <p></p> <p>Observations of <span class="hlt">Antarctic</span> ozone levels and the discovery of a hole in the <span class="hlt">Antarctic</span> region are examined. The effects of chlorofluorocarbons (CFCs) on the level of stratospheric ozone are analyzed. Three cycles explaining the cause of ozone depletion in the poles are proposed. A comparison of field data and proposed depletion cycles reveals that the chemical origin of the ozone hole is due to CFCs. The potential global effects of the <span class="hlt">Antarctic</span> ozone hole are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813231J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813231J"><span>In-situ measurements of chlorine <span class="hlt">activation</span>, nitric acid redistribution and ozone depletion in the <span class="hlt">Antarctic</span> lower vortex aboard the German research aircraft HALO during TACTS/ESMVal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jurkat, Tina; Voigt, Christiane; Kaufmann, Stefan; Schlage, Romy; Gottschaldt, Klaus-Dirk; Ziereis, Helmut; Hoor, Peter; Bozem, Heiko; Müller, Stefan; Zahn, Andreas; Schlager, Hans; Oelhaf, Hermann; Sinnhuber, Björn-Martin; Dörnbrack, Andreas</p> <p>2016-04-01</p> <p>In-situ measurements of stratospheric chlorine compounds are rare and exhibit the potential to gain insight into small scale mixing processes where stratospheric air masses of different origin and history interact. In addition, the relationship with chemically stable trace gases helps to identify regions that have been modified by chemical processing on polar stratospheric clouds. To this end, in-situ measurements of ClONO2, HCl, HNO3, NOy, N2O and O3 have been performed in the <span class="hlt">Antarctic</span> Polar Vortex in September 2012 aboard the German research aircraft HALO (High Altitude and Long Rang research aircraft) during the TACTS/ESMVal (Transport and Composition in the UTLS/Earth System Model Validation) mission. With take-off and landing in Capetown, HALO sampled vortex air with latitudes down to 65°S, at altitudes between 8 and 14.3 km and potential temperatures between 340 and 390 K. Before intering the vortex at 350 K potential temperature, HALO additionally sampled mid-latitude stratospheric air. The trace gas distributions at the edge of the <span class="hlt">Antarctic</span> polar vortex show distinct signatures of processed upper stratospheric vortex air and chemically different lower stratospheric / upper tropospheric air. Diabatic descend of the vortex transports processed air into the lower stratosphere. Here small scale filaments of only a few kilometers extension form at the lower vortex boundary due to shear stress, ultimately leading to transport and irreversible mixing. Comparison of trace gas relationships with those at the beginning of the polar winter reveals substantial chlorine <span class="hlt">activation</span>, ozone depletion de- and renitrification with high resolution. Furthermore, the measurements are compared to the chemistry climate models EMAC and supported by ECMWF analysis. Finally, we compare the <span class="hlt">Antarctic</span> measurements with new measurements of ClONO2, HCl and HNO3 aboard HALO obtained during the Arctic mission POLSTRACC (POLar STratosphere in a Changing Climate) based in Kiruna (Sveden</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title33-vol3/pdf/CFR-2013-title33-vol3-sec334-762.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title33-vol3/pdf/CFR-2013-title33-vol3-sec334-762.pdf"><span>33 CFR 334.762 - Naval Support <span class="hlt">Activity</span> Panama City; North Bay and <span class="hlt">West</span> Bay; restricted areas.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-07-01</p> <p>... City; North Bay and <span class="hlt">West</span> Bay; restricted areas. 334.762 Section 334.762 Navigation and Navigable Waters CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS § 334.762 Naval Support <span class="hlt">Activity</span> Panama City; North Bay and <span class="hlt">West</span> Bay; restricted areas. (a)...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title33-vol3/pdf/CFR-2012-title33-vol3-sec334-762.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title33-vol3/pdf/CFR-2012-title33-vol3-sec334-762.pdf"><span>33 CFR 334.762 - Naval Support <span class="hlt">Activity</span> Panama City; North Bay and <span class="hlt">West</span> Bay; restricted areas.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-07-01</p> <p>... City; North Bay and <span class="hlt">West</span> Bay; restricted areas. 334.762 Section 334.762 Navigation and Navigable Waters CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS § 334.762 Naval Support <span class="hlt">Activity</span> Panama City; North Bay and <span class="hlt">West</span> Bay; restricted areas. (a)...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26667917','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26667917"><span><span class="hlt">Antarctic</span> subglacial lake exploration: first results and future plans.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Siegert, Martin J; Priscu, John C; Alekhina, Irina A; Wadham, Jemma L; Lyons, W Berry</p> <p>2016-01-28</p> <p>After more than a decade of planning, three attempts were made in 2012-2013 to access, measure in situ properties and directly sample subglacial <span class="hlt">Antarctic</span> lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically <span class="hlt">active</span> lake at the coastal margin of <span class="hlt">West</span> Antarctica, obtaining samples that would later be used to prove the existence of microbial life and <span class="hlt">active</span> biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about <span class="hlt">Antarctic</span> subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PrOce..96...93L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PrOce..96...93L"><span>Population dynamics of Salpa thompsoni near the <span class="hlt">Antarctic</span> Peninsula: Growth rates and interannual variations in reproductive <span class="hlt">activity</span> (1993-2009)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loeb, V. J.; Santora, J. A.</p> <p>2012-04-01</p> <p>The salp Salpa thompsoni has exhibited increased abundance in high latitude portions of the Southern Ocean in recent decades and is now frequently the numerically dominant zooplankton taxon in the <span class="hlt">Antarctic</span> Peninsula region. The abundance increase of this species in high latitude waters is believed related to ocean warming. Due to its continuous filter feeding and production of dense rapidly sinking fecal pellets S. thompsoni is considered to be an important link in the export of particulate carbon from the surface waters. Hence basic information on the life history of this component of the <span class="hlt">Antarctic</span> marine ecosystem is essential for assessing its impact given continued climate warming. Here we cover various aspects of the life history of S. thompsoni collected in the north <span class="hlt">Antarctic</span> Peninsula during annual austral summer surveys of the US <span class="hlt">Antarctic</span> Marine Living Resources (AMLR) Program between 1993 and 2009. We focus on seasonal and interannual variations in the size composition and abundance of the aggregate (sexual) and solitary (asexual) stages. This information is valuable for refining components of Southern Ocean food web models that explicitly deal with size-structured and life history information on zooplankton. Intraseasonal changes in length-frequency distribution of both stages are used to estimate their growth rates. These average 0.40 mm day-1 for aggregates and 0.23 mm day-1 for solitaries; together these represent ∼7 week and ∼7.5 month generation times, respectively, and a 9 month life cycle (i.e., onset of aggregate production year 1 to aggregate production year 2). Based on the maximum lengths typically found during January-March, the life spans of the aggregate and solitary stages can reach at least ∼5 and ∼15 months, respectively. Length-frequency distributions each year reflect interannual differences in timing of the initiation and peak reproductive output. Interannual differences in the abundance of total salps and proportions of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tectp.585....3G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tectp.585....3G"><span>Air and shipborne magnetic surveys of the <span class="hlt">Antarctic</span> into the 21st century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Golynsky, A.; Bell, R.; Blankenship, D.; Damaske, D.; Ferraccioli, F.; Finn, C.; Golynsky, D.; Ivanov, S.; Jokat, W.; Masolov, V.; Riedel, S.; von Frese, R.; Young, D.</p> <p>2013-02-01</p> <p>The <span class="hlt">Antarctic</span> geomagnetics' community remains very <span class="hlt">active</span> in crustal anomaly mapping. More than 1.5 million line-km of new air- and shipborne data have been acquired over the past decade by the international community in Antarctica. These new data together with surveys that previously were not in the public domain significantly upgrade the ADMAP compilation. Aeromagnetic flights over East Antarctica have been concentrated in the Transantarctic Mountains, the Prince Charles Mountains - Lambert Glacier area, and western Dronning Maud Land (DML) — Coats Land. Additionally, surveys were conducted over Lake Vostok and the western part of Marie Byrd Land by the US Support Office for Aerogeophysical Research projects and over the Amundsen Sea Embayment during the austral summer of 2004/2005 by a collaborative US/UK aerogeophysical campaign. New aeromagnetic data over the Gamburtsev Subglacial Mountains (120,000 line-km), acquired within the IPY Antarctica's Gamburtsev Province project reveal fundamental geologic features beneath the East <span class="hlt">Antarctic</span> Ice sheet critical to understanding Precambrian continental growth processes. Roughly 100,000 line-km of magnetic data obtained within the International Collaboration for Exploration of the Cryosphere through Aerogeophysical Profiling promises to shed light on subglacial lithology and identify crustal boundaries for the central <span class="hlt">Antarctic</span> Plate. Since the 1996/97 season, the Alfred Wegener Institute has collected 90,000 km of aeromagnetic data along a 1200 km long segment of the East <span class="hlt">Antarctic</span> coast over western DML. Recent cruises by Australian, German, Japanese, Russian, British, and American researchers have contributed to long-standing studies of the <span class="hlt">Antarctic</span> continental margin. Along the continental margin of East Antarctica <span class="hlt">west</span> of Maud Rise to the George V Coast of Victoria Land, the Russian Polar Marine Geological Research Expedition and Geoscience Australia obtained 80,000 and 20,000 line-km, respectively, of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Antarctic+AND+climate&id=EJ321613','ERIC'); return false;" href="http://eric.ed.gov/?q=Antarctic+AND+climate&id=EJ321613"><span>The <span class="hlt">Antarctic</span> Ice.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Radok, Uwe</p> <p>1985-01-01</p> <p>The International <span class="hlt">Antarctic</span> Glaciological Project has collected information on the East <span class="hlt">Antarctic</span> ice sheet since 1969. Analysis of ice cores revealed climatic history, and radar soundings helped map bedrock of the continent. Computer models of the ice sheet and its changes over time will aid in predicting the future. (DH)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991anc..book......','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991anc..book......"><span><span class="hlt">Antarctic</span> news clips, 1991</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p></p> <p>1991-08-01</p> <p>Published stories are presented that sample a year's news coverage of Antarctica. The intent is to provide the U.S. <span class="hlt">Antarctic</span> 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; <span class="hlt">antarctic</span> treaty issues; and tourism</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Ozone+AND+layer&pg=4&id=EJ364056','ERIC'); return false;" href="http://eric.ed.gov/?q=Ozone+AND+layer&pg=4&id=EJ364056"><span>The <span class="hlt">Antarctic</span> Ozone Hole.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Stolarski, Richard S.</p> <p>1988-01-01</p> <p>Discusses the Airborne <span class="hlt">Antarctic</span> Ozone Experiment (1987) and the findings of the British <span class="hlt">Antarctic</span> Survey (1985). Proposes two theories for the appearance of the hole in the ozone layer over Antarctica which appears each spring; air pollution and natural atmospheric shifts. Illustrates the mechanics of both. Supports worldwide chlorofluorocarbon…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012QSRv...49...52N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012QSRv...49...52N"><span>A 16,000-yr tephra framework for the <span class="hlt">Antarctic</span> ice sheet: a contribution from the new Talos Dome core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Narcisi, Biancamaria; Petit, Jean Robert; Delmonte, Barbara; Scarchilli, Claudio; Stenni, Barbara</p> <p>2012-08-01</p> <p>A detailed tephra record for the last 16,000 years of the TALDICE ice core drilled at Talos Dome (East Antarctica, Pacific/Ross Sea sector) is documented. Traces of 26 different explosive volcanic eruptions, dated by ice core chronology and framed within the climate (δ18O) record for the core, have been identified. Glass major element composition and grain size data indicate that all prominent tephra layers derive from <span class="hlt">Antarctic</span> volcanic <span class="hlt">activity</span> and likely originated in proximal volcanoes of the Melbourne Volcanic Province (Northern Victoria Land). Two other <span class="hlt">Antarctic</span> horizons may have originated from the more distant volcanoes of Mount Berlin (Marie Byrd Land, <span class="hlt">West</span> Antarctica) and Mount Erebus (Ross Island, Southern Victoria Land). Moreover, based on glass-shard geochemistry and a 20-year analysis of atmospheric back trajectories suggesting ash transport from South America to the drilling site by the circumpolar westerly circulation, a few faint microtephra horizons are attributed to Andean volcanic <span class="hlt">activity</span>. Two of these tephras are interpreted to be related to known Holocene explosive eruptions from the volcanoes of Mount Hudson and Mount Burney. Finally, by comparing compositional features in conjunction with age data, three TALDICE tephras have been successfully correlated with volcanic layers in other ice records of the <span class="hlt">Antarctic</span> ice sheet. Altogether, our results expand the <span class="hlt">Antarctic</span> tephrostratigraphic framework and add value to the prospects for continental-scale correlations between ice cores and Southern Hemisphere sediment archives.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JAtS...58.3477M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JAtS...58.3477M"><span>Impact of Sea Surface Temperature Anomalies on the Atlantic Tropical Storm <span class="hlt">Activity</span> and <span class="hlt">West</span> African Rainfall.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mo, Kingtse; Bell, Gerald D.; Thiaw, Wassila M.</p> <p>2001-11-01</p> <p>The association between rainfall over the Sahel and Sudan region and tropical storm <span class="hlt">activity</span> in the Atlantic is examined using the NCEP NCAR reanalysis and sea surface temperature anomalies (SSTAs) from 1949 to 1998. Evidence indicates that both are influenced by global SSTAs. The SSTA modes generating favorable atmospheric conditions for tropical storms to develop are also in favor of a wet rainfall season in the Sahel and Sudan region. The easterly waves over <span class="hlt">West</span> Africa become tropical storms only if the atmospheric conditions over the Atlantic are favorable. These conditions are responses to SSTAs.In addition to ENSO, a multidecadal trend mode also plays a role. The positive phase of the trend mode features positive loadings in the North Pacific and the North Atlantic, and negative loadings over the three southern oceans. The positive (negative) phases of both modes are associated with increased (reduced) Atlantic tropical storm <span class="hlt">activity</span>, and with wet (dry) <span class="hlt">West</span> African monsoon seasons. The SSTAs over the tropical South Atlantic (S-ATL) are related to the rainfall dipole over <span class="hlt">West</span> Africa, but the influence on tropical storms is not large. Warm (cold) SSTAs over the tropical North Atlantic enhance (suppress) the occurrence of tropical storms, but have little influence on rainfall over <span class="hlt">West</span> Africa.The most prominent circulation features associated with the positive phases of SSTA modes are enhanced upper-level 200-hPa easterly winds and reduced vertical wind shear in the main development region of the tropical Atlantic, which are well-known features of <span class="hlt">active</span> Atlantic tropical storm seasons. The associated low-level flow shows enhanced anomalous westerly winds across the Atlantic to Africa. That allows more moisture transport into Africa and, therefore, more rainfall.<HR ALIGN="center" WIDTH="30%"></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28280714','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28280714"><span>Anti-Biofilm <span class="hlt">Activity</span> of a Long-Chain Fatty Aldehyde from <span class="hlt">Antarctic</span> Pseudoalteromonas haloplanktis TAC125 against Staphylococcus epidermidis Biofilm.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Casillo, Angela; Papa, Rosanna; Ricciardelli, Annarita; Sannino, Filomena; Ziaco, Marcello; Tilotta, Marco; Selan, Laura; Marino, Gennaro; Corsaro, Maria M; Tutino, Maria L; Artini, Marco; Parrilli, Ermenegilda</p> <p>2017-01-01</p> <p>Staphylococcus epidermidis is a harmless human skin colonizer responsible for ~20% of orthopedic device-related infections due to its capability to form biofilm. Nowadays there is an interest in the development of anti-biofilm molecules. Marine bacteria represent a still underexploited source of biodiversity able to synthesize a broad range of bioactive compounds, including anti-biofilm molecules. Previous results have demonstrated that the culture supernatant of <span class="hlt">Antarctic</span> marine bacterium Pseudoalteromonas haloplanktis TAC125 impairs the formation of S. epidermidis biofilm. Further, evidence supports the hydrophobic nature of the <span class="hlt">active</span> molecule, which has been suggested to act as a signal molecule. In this paper we describe an efficient <span class="hlt">activity</span>-guided purification protocol which allowed us to purify this anti-biofilm molecule and structurally characterize it by NMR and mass spectrometry analyses. Our results demonstrate that the anti-biofilm molecule is pentadecanal, a long-chain fatty aldehyde, whose anti-S. epidermidis biofilm <span class="hlt">activity</span> has been assessed using both static and dynamic biofilm assays. The specificity of its action on S. epidermidis biofilm has been demonstrated by testing chemical analogs of pentadecanal differing either in the length of the aliphatic chain or in their functional group properties. Further, indications of the mode of action of pentadecanal have been collected by studying the bioluminescence of a Vibrio harveyi reporter strain for the detection of autoinducer AI-2 like <span class="hlt">activities</span>. The data collected suggest that pentadecanal acts as an AI-2 signal. Moreover, the aldehyde metabolic role and synthesis in the <span class="hlt">Antarctic</span> source strain has been investigated. To the best of our knowledge, this is the first report on the identification of an anti-biofilm molecule form from cold-adapted bacteria and on the action of a long-chain fatty aldehyde acting as an anti-biofilm molecule against S. epidermidis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5322152','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5322152"><span>Anti-Biofilm <span class="hlt">Activity</span> of a Long-Chain Fatty Aldehyde from <span class="hlt">Antarctic</span> Pseudoalteromonas haloplanktis TAC125 against Staphylococcus epidermidis Biofilm</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Casillo, Angela; Papa, Rosanna; Ricciardelli, Annarita; Sannino, Filomena; Ziaco, Marcello; Tilotta, Marco; Selan, Laura; Marino, Gennaro; Corsaro, Maria M.; Tutino, Maria L.; Artini, Marco; Parrilli, Ermenegilda</p> <p>2017-01-01</p> <p>Staphylococcus epidermidis is a harmless human skin colonizer responsible for ~20% of orthopedic device-related infections due to its capability to form biofilm. Nowadays there is an interest in the development of anti-biofilm molecules. Marine bacteria represent a still underexploited source of biodiversity able to synthesize a broad range of bioactive compounds, including anti-biofilm molecules. Previous results have demonstrated that the culture supernatant of <span class="hlt">Antarctic</span> marine bacterium Pseudoalteromonas haloplanktis TAC125 impairs the formation of S. epidermidis biofilm. Further, evidence supports the hydrophobic nature of the <span class="hlt">active</span> molecule, which has been suggested to act as a signal molecule. In this paper we describe an efficient <span class="hlt">activity</span>-guided purification protocol which allowed us to purify this anti-biofilm molecule and structurally characterize it by NMR and mass spectrometry analyses. Our results demonstrate that the anti-biofilm molecule is pentadecanal, a long-chain fatty aldehyde, whose anti-S. epidermidis biofilm <span class="hlt">activity</span> has been assessed using both static and dynamic biofilm assays. The specificity of its action on S. epidermidis biofilm has been demonstrated by testing chemical analogs of pentadecanal differing either in the length of the aliphatic chain or in their functional group properties. Further, indications of the mode of action of pentadecanal have been collected by studying the bioluminescence of a Vibrio harveyi reporter strain for the detection of autoinducer AI-2 like <span class="hlt">activities</span>. The data collected suggest that pentadecanal acts as an AI-2 signal. Moreover, the aldehyde metabolic role and synthesis in the <span class="hlt">Antarctic</span> source strain has been investigated. To the best of our knowledge, this is the first report on the identification of an anti-biofilm molecule form from cold-adapted bacteria and on the action of a long-chain fatty aldehyde acting as an anti-biofilm molecule against S. epidermidis. PMID:28280714</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997amc..book.....K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997amc..book.....K"><span><span class="hlt">Antarctic</span> Meteorology and Climatology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>King, J. C.; Turner, J.</p> <p>1997-07-01</p> <p>This book is a comprehensive survey of the climatology and meteorology of Antarctica. The first section of the book reviews the methods by which we can observe the <span class="hlt">Antarctic</span> atmosphere and presents a synthesis of climatological measurements. In the second section, the authors consider the processes that maintain the observed climate, from large-scale atmospheric circulation to small-scale processes. The final section reviews our current knowledge of the variability of <span class="hlt">Antarctic</span> climate and the possible effects of "greenhouse" warming. The authors stress links among the <span class="hlt">Antarctic</span> atmosphere, other elements of the <span class="hlt">Antarctic</span> climate system (oceans, sea ice and ice sheets), and the global climate system. This volume will be of greatest interest to meteorologists and climatologists with a specialized interest in Antarctica, but it will also appeal to researchers in <span class="hlt">Antarctic</span> glaciology, oceanography and biology. Graduates and undergraduates studying physical geography, and the earth, atmospheric and environmental sciences will find much useful background material in the book.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3140504','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3140504"><span>Characterisation of the Nematode Community of a Low-<span class="hlt">Activity</span> Cold Seep in the Recently Ice-Shelf Free Larsen B Area, Eastern <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hauquier, Freija; Ingels, Jeroen; Gutt, Julian; Raes, Maarten; Vanreusel, Ann</p> <p>2011-01-01</p> <p>Background Recent climate-induced ice-shelf disintegration in the Larsen A (1995) and B (2002) areas along the Eastern <span class="hlt">Antarctic</span> Peninsula formed a unique opportunity to assess sub-ice-shelf benthic community structure and led to the discovery of unexplored habitats, including a low-<span class="hlt">activity</span> methane seep beneath the former Larsen B ice shelf. Since both limited particle sedimentation under previously permanent ice coverage and reduced cold-seep <span class="hlt">activity</span> are likely to influence benthic meiofauna communities, we characterised the nematode assemblage of this low-<span class="hlt">activity</span> cold seep and compared it with other, now seasonally ice-free, Larsen A and B stations and other <span class="hlt">Antarctic</span> shelf areas (Weddell Sea and Drake Passage), as well as cold-seep ecosystems world-wide. Principal Findings The nematode community at the Larsen B seep site differed significantly from other <span class="hlt">Antarctic</span> sites in terms of dominant genera, diversity and abundance. Densities in the seep samples were high (>2000 individuals per 10 cm2) and showed below-surface maxima at a sediment depth of 2–3 cm in three out of four replicates. All samples were dominated by one species of the family Monhysteridae, which was identified as a Halomonhystera species that comprised between 80 and 86% of the total community. The combination of high densities, deeper density maxima and dominance of one species is shared by many cold-seep ecosystems world-wide and suggested a possible dependence upon a chemosynthetic food source. Yet stable 13C isotopic signals (ranging between −21.97±0.86‰ and −24.85±1.89‰) were indicative of a phytoplankton-derived food source. Conclusion The recent ice-shelf collapse and enhanced food input from surface phytoplankton blooms were responsible for the shift from oligotrophic pre-collapse conditions to a phytodetritus-based community with high densities and low diversity. The parthenogenetic reproduction of the highly dominant Halomonhystera species is rather unusual for marine</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011GMS...192...27P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GMS...192...27P"><span><span class="hlt">Antarctic</span> subglacial lake discharges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pattyn, Frank</p> <p></p> <p><span class="hlt">Antarctic</span> subglacial lakes were long time supposed to be relatively closed and stable environments with long residence times and slow circulations. This view has recently been challenged with evidence of <span class="hlt">active</span> subglacial lake discharge underneath the <span class="hlt">Antarctic</span> ice sheet. Satellite altimetry observations witnessed rapid changes in surface elevation across subglacial lakes over periods ranging from several months to more than a year, which were interpreted as subglacial lake discharge and subsequent lake filling, and which seem to be a common and widespread feature. Such discharges are comparable to jökulhlaups and can be modeled that way using the Nye-Röthlisberger theory. Considering the ice at the base of the ice sheet at pressure melting point, subglacial conduits are sustainable over periods of more than a year and over distances of several hundreds of kilometers. Coupling of an ice sheet model to a subglacial lake system demonstrated that small changes in surface slope are sufficient to start and sustain episodic subglacial drainage events on decadal time scales. Therefore, lake discharge may well be a common feature of the subglacial hydrological system, influencing the behavior of large ice sheets, especially when subglacial lakes are perched at or near the onset of large outlet glaciers and ice streams. While most of the observed discharge events are relatively small (101-102 m3 s-1), evidence for larger subglacial discharges is found in ice free areas bordering Antarctica, and witnessing subglacial floods of more than 106 m3 s-1 that occurred during the middle Miocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715438Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715438Z"><span>Controls and variability of solute and sedimentary fluxes in <span class="hlt">Antarctic</span> and sub-<span class="hlt">Antarctic</span> Environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwolinski, Zbigniew</p> <p>2015-04-01</p> <p>The currently prepared SEDIBUD Book on "Source-to-Sink Fluxes in Undisturbed Cold Environments" (edited by Achim A. Beylich, John C. Dixon and Zbigniew Zwolinski and published by Cambridge University Press) is summarizing and synthesizing the achievements of the International Association of Geomorphologists` (I.A.G./A.I.G.) Working Group SEDIBUD (Sediment Budgets in Cold Environments), which has been <span class="hlt">active</span> since 2005 (http://www.geomorph.org/wg/wgsb.html). The book comprises five parts. One of them is part about sub-<span class="hlt">Antarctic</span> and <span class="hlt">Antarctic</span> Environments. This part "Sub-<span class="hlt">Antarctic</span> and <span class="hlt">Antarctic</span> Environments" describes two different environments, namely oceanic and continental ones. Each part contains results of research on environmental drivers and rates of contemporary solute and sedimentary fluxes in selected sites. Apart from describing the environmental conditions of the whole continent of Antarctica and sub-<span class="hlt">Antarctic</span> islands (Zb.Zwolinski, M.Kejna, A.N.Lastochkin, A.Zhirov, S.Boltramovich) this part of the book characterizes terrestrial polar oases free from multi-year ice and snow covers (Zb.Zwolinski). The detailed results of geoecological and sedimentological research come from different parts of Antarctica. <span class="hlt">Antarctic</span> continental shelf (E.Isla) is an example of sub-<span class="hlt">Antarctic</span> oceanic environment. South Shetlands, especially King George Island (Zb.Zwolinski, M.Kejna, G.Rachlewicz, I.Sobota, J.Szpikowski), is an example of sub-<span class="hlt">Antarctic</span> terrestrial environment. <span class="hlt">Antarctic</span> Peninsula (G.Vieira, M.Francelino, J.C.Fernandes) and surroundings of McMurdo Dry Valleys (W.B.Lyons, K.A.Welch, J.Levy, A.Fountain, D.McKnight) are examples of <span class="hlt">Antarctic</span> continental environments. The key goals of the <span class="hlt">Antarctic</span> and sub-<span class="hlt">Antarctic</span> book chapters are following: (i) identify the main environmental drivers and rates of contemporary solute and sedimentary fluxes, and (ii) model possible effects of projected climate change on solute and sedimentary fluxes in cold climate environments</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032356','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032356"><span>Nocturnal <span class="hlt">activity</span> patterns of northern myotis (Myotis septentrionalis) during the maternity season in <span class="hlt">West</span> Virginia (USA)</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Johnson, J.B.; Edwards, J.W.; Ford, W.M.</p> <p>2011-01-01</p> <p>Nocturnal <span class="hlt">activity</span> patterns of northern myotis (Myotis septentrionalis) at diurnal roost trees remain largely uninvestigated. For example, the influence of reproductive status, weather, and roost tree and surrounding habitat characteristics on timing of emergence, intra-night <span class="hlt">activity</span>, and entrance at their roost trees is poorly known. We examined nocturnal <span class="hlt">activity</span> patterns of northern myotis maternity colonies during pregnancy and lactation at diurnal roost trees situated in areas that were and were not subjected to recent prescribed fires at the Fernow Experimental Forest, <span class="hlt">West</span> Virginia from 2007 to 2009. According to exit counts and acoustic data, northern myotis colony sizes were similar between reproductive periods and roost tree settings. However, intra-night <span class="hlt">activity</span> patterns differed slightly between reproductive periods and roost trees in burned and non-burned areas. Weather variables poorly explained variation in <span class="hlt">activity</span> patterns during pregnancy, but precipitation and temperature were negatively associated with <span class="hlt">activity</span> patterns during lactation. ?? Museum and Institute of Zoology PAS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985JGR....9012901D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985JGR....9012901D"><span>Volcanic deposits in <span class="hlt">Antarctic</span> snow and ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delmas, Robert J.; Legrand, Michel; Aristarain, Alberto J.; Zanolini, FrançOise</p> <p>1985-12-01</p> <p>Major volcanic eruptions are able to spread large amounts of sulfuric acid all over the world. Acid layers of volcanic origin were detected for the first time a few years ago by Hammer in Greenland ice. The present paper deals with volcanic deposits in the <span class="hlt">Antarctic</span>. The different methods that can be used to find volcanic acid deposits in snow and ice cores are compared: electrical conductivity, sulfate, and acidity measurements. Numerous snow and ice samples collected at several <span class="hlt">Antarctic</span> locations were analyzed. The results reveal that the two major volcanic events recorded by H2SO4, fallout in <span class="hlt">Antarctic</span> ice over the last century are the eruptions of Krakatoa (1883) and Agung (1963), both located at equatorial latitudes in the southern hemisphere. The volcanic signals are found to be particularly well defined at central <span class="hlt">Antarctic</span> locations apparently in relation to the low snow accumulation rates in these areas. It is demonstrated that volcanic sulfuric acid in snow is not even partially neutralized by ammonia. The possible influence of <span class="hlt">Antarctic</span> volcanic <span class="hlt">activity</span> on snow chemistry is also discussed, using the three recent eruptions of the Deception Island volcano as examples. Only one of them seems to have had a significant effect on the chemistry of snow at a location 200 km from this volcano. It is concluded that <span class="hlt">Antarctic</span> volcanic ice records are less complicated than Greenland records because of the limited number of volcanos in the southern hemisphere and the apparently higher signal to background ratio for acidity in Antarctica than in Greenland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25814064','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25814064"><span>Ice sheets. Volume loss from <span class="hlt">Antarctic</span> ice shelves is accelerating.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Paolo, Fernando S; Fricker, Helen A; Padman, Laurie</p> <p>2015-04-17</p> <p>The floating ice shelves surrounding the <span class="hlt">Antarctic</span> Ice Sheet restrain the grounded ice-sheet flow. Thinning of an ice shelf reduces this effect, leading to an increase in ice discharge to the ocean. Using 18 years of continuous satellite radar altimeter observations, we have computed decadal-scale changes in ice-shelf thickness around the <span class="hlt">Antarctic</span> continent. Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 cubic kilometers per year for 1994-2003 to rapid loss of 310 ± 74 cubic kilometers per year for 2003-2012. <span class="hlt">West</span> <span class="hlt">Antarctic</span> losses increased by ~70% in the past decade, and earlier volume gain by East <span class="hlt">Antarctic</span> ice shelves ceased. In the Amundsen and Bellingshausen regions, some ice shelves have lost up to 18% of their thickness in less than two decades.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3205705','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3205705"><span>Characterization of Serum Phospholipase A2 <span class="hlt">Activity</span> in Three Diverse Species of <span class="hlt">West</span> African Crocodiles</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Merchant, Mark; Juneau, Kate; Gemillion, Jared; Falconi, Rodolfo; Doucet, Aaron; Shirley, Matthew H.</p> <p>2011-01-01</p> <p>Secretory phospholipase A2, an enzyme that exhibits substantial immunological <span class="hlt">activity</span>, was measured in the serum of three species of diverse <span class="hlt">West</span> African crocodiles. Incubation of different volumes of crocodile serum with bacteria labeled with a fluorescent fatty acid in the sn-2 position of membrane lipids resulted in a volume-dependent liberation of fluorescent probe. Serum from the Nile crocodile (Crocodylus niloticus) exhibited slightly higher <span class="hlt">activity</span> than that of the slender-snouted crocodile (Mecistops cataphractus) and the African dwarf crocodile (Osteolaemus tetraspis). Product formation was inhibited by BPB, a specific PLA2 inhibitor, confirming that the <span class="hlt">activity</span> was a direct result of the presence of serum PLA2. Kinetic analysis showed that C. niloticus serum produced product more rapidly than M. cataphractus or O. tetraspis. Serum from all three species exhibited temperature-dependent PLA2 <span class="hlt">activities</span> but with slightly different thermal profiles. All three crocodilian species showed high levels of <span class="hlt">activity</span> against eight different species of bacteria. PMID:22110960</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51D..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51D..02S"><span>The influence of <span class="hlt">Antarctic</span> ice sheet topography change on <span class="hlt">Antarctic</span> climate -- a positive feedback.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steig, E. J.</p> <p>2015-12-01</p> <p>The potential for climate change to result in changes to the <span class="hlt">Antarctic</span> ice sheet -- including the possibility of a full collapse of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Shet (WAIS) is well known. Less well known is that the collapse of the ice sheet, if it occured, would have significant impcts on regional climate. We use climate model simulations to quantify the impact of topographic changes on the surface climate of Antarctica. As a general rule, lowered topography produces anomalous cyclonic circulation owing to fundamental atmospheric dynamical constraints. In the case of WAIS collapse, this causes increased flow of warm, maritime air toward the South Pole and cold-air advection from the East <span class="hlt">Antarctic</span> plateau toward the Ross Sea and Marie Byrd Land, <span class="hlt">West</span> Antarctica. This resulting pattern The result is cooling in some areas and warming in others, a pattern that is similar to that observed from ice core paleotemperature data for the last interglacial period, suggesting that WAIS collapse occurred at that time. We find that magnitude of the response is roughly linear with the magnitude of the imposed elevation change. The regional response over <span class="hlt">West</span> Antarctica is large enough that it probably needs to be taken into account in modeling future changes to the ice sheet. Of particular interest is that lowering of the WAIS topography results in anomalous westerlies along the Amundsen Sea coastline. Anomalous westerlies in this region today are in large part responsible for the for intrusion of circumpolar deepwater onto the continental shelf, and the observed rapid thinning of <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice shelves. A positive feedback may thus exist in which lowering of the WAIS surface from climate forcing may enhance that forcing, leading to further elevation lowering and ice sheet mass loss.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..730M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..730M"><span>Non-extensivity and complexity in the earthquake <span class="hlt">activity</span> at the <span class="hlt">West</span> Corinth rift (Greece)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michas, Georgios; Vallianatos, Filippos; Sammonds, Peter</p> <p>2013-04-01</p> <p>Earthquakes exhibit complex phenomenology that is revealed from the fractal structure in space, time and magnitude. For that reason other tools rather than the simple Poissonian statistics seem more appropriate to describe the statistical properties of the phenomenon. Here we use Non-Extensive Statistical Physics [NESP] to investigate the inter-event time distribution of the earthquake <span class="hlt">activity</span> at the <span class="hlt">west</span> Corinth rift (central Greece). This area is one of the most seismotectonically <span class="hlt">active</span> areas in Europe, with an important continental N-S extension and high seismicity rates. NESP concept refers to the non-additive Tsallis entropy Sq that includes Boltzmann-Gibbs entropy as a particular case. This concept has been successfully used for the analysis of a variety of complex dynamic systems including earthquakes, where fractality and long-range interactions are important. The analysis indicates that the cumulative inter-event time distribution can be successfully described with NESP, implying the complexity that characterizes the temporal occurrences of earthquakes. Further on, we use the Tsallis entropy (Sq) and the Fischer Information Measure (FIM) to investigate the complexity that characterizes the inter-event time distribution through different time windows along the evolution of the seismic <span class="hlt">activity</span> at the <span class="hlt">West</span> Corinth rift. The results of this analysis reveal a different level of organization and clusterization of the seismic <span class="hlt">activity</span> in time. Acknowledgments. GM wish to acknowledge the partial support of the Greek State Scholarships Foundation (IKY).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17900765','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17900765"><span>Assessment of alpha <span class="hlt">activity</span> of building materials commonly used in <span class="hlt">West</span> Bengal, India.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ghosh, Dipak; Deb, Argha; Bera, Sukumar; Sengupta, Rosalima; Patra, Kanchan Kumar</p> <p>2008-02-01</p> <p>This paper, reports for the first time, an extensive study of alpha <span class="hlt">activity</span> of all widely used building materials (plaster of Paris, stone chips, marble, white cement, mosaic stone, limestone, sand, granite, cement brick, asbestos, red brick, cement tile, ceramic tile and ceramics) in <span class="hlt">West</span> Bengal, India. The alpha <span class="hlt">activities</span> have been measured using Solid State Nuclear Track Detector (SSNTD), a very sensitive detector for alpha particles. The samples were collected from local markets of Kolkata. The measured average alpha <span class="hlt">activities</span> ranged from 22.7+/-2.5 to 590.6+/-16.8Bqkg(-1). The alpha <span class="hlt">activity</span> of ceramic tiles was highest and provides additional data to estimate the effect of environmental radiation exposure on human health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5648359','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5648359"><span>Alaska dominates exploration and development <span class="hlt">activity</span> on U. S. <span class="hlt">West</span> Coast</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Williams, B.</p> <p>1991-04-08</p> <p>Alaska's accelerating exploration and development <span class="hlt">activity</span> is setting the pace for the U.S. <span class="hlt">West</span> Coast. Continued wildcatting in the Chukchi Sea and Beaufort Sea--albeit hamstrung by permitting problems--significant new development projects on the North Slope, and the most ambitious lease sale schedule in years highlight Alaskan action in 1991. California highlights include expansion of massive steamflood projects in San Joaquin Valley giant heavy oil fields and start-up of the long-delayed Point Arguello project. There is little of note in the Pacific Northwest outside extension of the Mist gas complex in Oregon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9110969','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9110969"><span><span class="hlt">Antarctic</span> Tectonics: Constraints From an ERS-1 Satellite Marine Gravity Field</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McAdoo; Laxon</p> <p>1997-04-25</p> <p>A high-resolution gravity field of poorly charted and ice-covered ocean near <span class="hlt">West</span> Antarctica, from the Ross Sea east to the Weddell Sea, has been derived with the use of satellite altimetry, including ERS-1 geodetic phase, wave-form data. This gravity field reveals regional tectonic fabric, such as gravity lineations, which are the expression of fracture zones left by early (65 to 83 million years ago) Pacific-<span class="hlt">Antarctic</span> sea-floor spreading that separated the Campbell Plateau and New Zealand continent from <span class="hlt">West</span> Antarctica. These lineations constrain plate motion history and confirm the hypothesis that Antarctica behaved as two distinct plates, separated from each other by an extensional Bellingshausen plate boundary <span class="hlt">active</span> in the Amundsen Sea before about 61 million years ago.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://dx.doi.org/10.1111/j.1948-7134.2010.00055.x','USGSPUBS'); return false;" href="http://dx.doi.org/10.1111/j.1948-7134.2010.00055.x"><span>The use of early summer mosquito surveillance to predict late summer <span class="hlt">West</span> Nile virus <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ginsberg, Howard S.; Rochlin, Ilia; Campbell, Scott R.</p> <p>2010-01-01</p> <p>Utility of early-season mosquito surveillance to predict <span class="hlt">West</span> Nile virus <span class="hlt">activity</span> in late summer was assessed in Suffolk County, NY. Dry ice-baited CDC miniature light traps paired with gravid traps were set weekly. Maximum-likelihood estimates of WNV positivity, minimum infection rates, and % positive pools were generally well correlated. However, positivity in gravid traps was not correlated with positivity in CDC light traps. The best early-season predictors of WNV <span class="hlt">activity</span> in late summer (estimated using maximum-likelihood estimates of Culex positivity in August and September) were early date of first positive pool, low numbers of mosquitoes in July, and low numbers of mosquito species in July. These results suggest that early-season entomological samples can be used to predict WNV <span class="hlt">activity</span> later in the summer, when most human cases are acquired. Additional research is needed to establish which surveillance variables are most predictive and to characterize the reliability of the predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHyd..544..363S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHyd..544..363S"><span>Groundwater storage inferred from earthquake <span class="hlt">activities</span> around East Asia and <span class="hlt">West</span> Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shih, David Ching-Fang</p> <p>2017-01-01</p> <p>Groundwater is a necessary and indispensable resource in the gradual depletion of the amount in the world. Groundwater storage is an important indicator to evaluate the capability of volume of water can be released from the aquifer. This research highlights a new assessment to infer the storage of aquifer using earthquakes <span class="hlt">activated</span> around East Asia and the ring of fire at <span class="hlt">West</span> Pacific Ocean. Ten significant seismic events are used to evaluate the groundwater storage at an observation station. By analyzing the spectra of groundwater level and seismogram, it is evident that the period varied in 7-25 s of Rayleigh waves significantly dominate propagation from the epicenter of earthquakes to the observation station. The storage coefficient is then shown in the order of 10-4-10-3. The major innovation of this study suggests that to concretely deduce the groundwater storage by earthquake <span class="hlt">activity</span> has become feasible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5363705','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5363705"><span>Inventory of non-federally funded marine pollution research, development, and monitoring <span class="hlt">activities</span>: <span class="hlt">West</span> Coast region</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Canton, G.M.; Opresko, D.M.; Weaver, R.S.</p> <p>1987-12-01</p> <p>Knowledge of current marine pollution research and monitoring programs is an important factor in planning and guiding future national efforts to control such pollution. To supplement these reports on Federal <span class="hlt">activities</span>, NMPPO published a series of reports in 1980 on non-federally funded marine pollution research and monitoring <span class="hlt">activities</span> in various regions. The following document presents an update of one of these reports. It presents an inventory of the non-federally funded research and monitoring projects for the <span class="hlt">West</span> Coast region of the United States. It is one in a series of four updates that will collectively provide an updated inventory of non-federally funded projects for all the coastal regions of the United States.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.1480D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.1480D"><span>Long-term explosive degassing and debris flow <span class="hlt">activity</span> at <span class="hlt">West</span> Mata submarine volcano</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dziak, R. P.; Bohnenstiehl, D. R.; Baker, E. T.; Matsumoto, H.; Caplan-Auerbach, J.; Embley, R. W.; Merle, S. G.; Walker, S. L.; Lau, T.-K.; Chadwick, W. W.</p> <p>2015-03-01</p> <p><span class="hlt">West</span> Mata is a 1200 m deep submarine volcano where explosive boninite eruptions were observed in 2009. The acoustic signatures from the volcano's summit eruptive vents Hades and Prometheus were recorded with an in situ (~25 m range) hydrophone during ROV dives in May 2009 and with local (~5 km range) moored hydrophones between December 2009 and August 2011. The sensors recorded low frequency (1-40 Hz), short duration explosions consistent with magma bubble bursts from Hades, and broadband, 1-5 min duration signals associated with episodes of fragmentation degassing from Prometheus. Long-term eruptive degassing signals, recorded through May 2010, preceded a several month period of declining <span class="hlt">activity</span>. Degassing episodes were not recorded acoustically after early 2011, although quieter effusive eruption <span class="hlt">activity</span> may have continued. Synchronous optical measurements of turbidity made between December 2009 and April 2010 indicate that turbidity maxima resulted from occasional south flank slope failures triggered by the collapse of accumulated debris during eruption intervals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.C42A..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.C42A..05S"><span>Satellites reveal <span class="hlt">Antarctic</span> mass imbalance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shepherd, A.</p> <p>2004-05-01</p> <p>Satellite radar observations have revealed a widespread mass imbalance in western Antarctica and rapid thinning of ice shelves at the <span class="hlt">Antarctic</span> Peninsula. The former shows grounded ice retreat in a region previously considered unstable to such events, and the latter illuminates an ongoing debate as to the mechanism through which ice shelves have disintegrated over the past decade. Both measurements inform us as to the present state of balance of the cryosphere and its interactions with the southern oceans. Since 1992, the Amundsen Sea sector of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet has lost 39 cubic kilometers of its volume each year due to an imbalance between snow accumulation and ice discharge. A flow disturbance is responsible for removing the majority of that ice from the trunks of the Pine Island, Thwaites and Smith glacier drainage systems, raising global sea level by over 1 mm during the past decade alone. The coincidence of rapid ice thinning at the Amundsen Coast and warm circumpolar deep water intrusion in Pine Island Bay, coupled with a ~ 50 cubic kilometre annual freshening of the Ross Sea Gyre downstream, makes ocean melting an attractive proposition for the origin of the regional disturbance. At the same time, the Larsen Ice Shelf surface has lowered by up to 0.27 m per year, in tandem with a period of atmospheric warming and ice shelf collapse. The lowering cannot be explained by increased summer melt-water production alone, and must reflect a loss of basal ice through melting. Ocean temperature measurements close to the ice shelf barrier support this conclusion, making enhanced basal ice melting a likely factor linking the regional climate warming and the successive disintegration of sections of the Larsen Ice Shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21360992','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21360992"><span>[Effects of simulated warming on soil enzyme <span class="hlt">activities</span> in two subalpine coniferous forests in <span class="hlt">west</span> Sichuan].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Zhen-feng; Tang, Zheng; Wan, Chuan; Xiong, Pei; Cao, Gang; Liu, Qing</p> <p>2010-11-01</p> <p>With open top chamber (OTC), this paper studied the effects of simulated warming on the <span class="hlt">activities</span> of soil invertase, urease, catalase, polyphenol oxidase in two contrasting subalpine coniferous forests (a dragon spruce plantation and a natural conifer forest) in <span class="hlt">west</span> Sichuan. The dynamic changes of soil temperature and soil moisture were monitored synchronously. In the whole growth season, simulated warming enhanced the daily mean temperature at soil depth 5 cm by 0.61 degrees C in the plantation, and by 0.55 degrees C in the natural forest. Conversely, the volumetric moisture at soil depth 10 cm was declined by 4.10% and 2.55%, respectively. Simulated warming also increased soil invertase, urease, catalase, and polyphenol oxidase <span class="hlt">activities</span>. The interactive effect of warming and forest type was significant on soil urease and catalase, but not significant on soil invertase and polyphenol oxidase. The warming effect on soil catalase depended, to some extent, on season change. In all treatments, the soil enzyme <span class="hlt">activities</span> in the natural forest were significantly higher than those in the plantation. The seasonal changes of test soil enzyme <span class="hlt">activities</span> were highly correlated with soil temperature, but less correlated with soil moisture. This study indicated that warming could enhance soil enzyme <span class="hlt">activities</span>, and the effect had definite correlations with forest type, enzyme category, and season change. The soil enzyme <span class="hlt">activities</span> in the subalpine coniferous forests were mainly controlled by soil temperature rather than soil moisture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21982595','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21982595"><span><span class="hlt">West</span> Nile virus infection does not induce PKR <span class="hlt">activation</span> in rodent cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Elbahesh, H; Scherbik, S V; Brinton, M A</p> <p>2011-12-05</p> <p>dsRNA-<span class="hlt">activated</span> protein kinase (PKR) is <span class="hlt">activated</span> by viral dsRNAs and phosphorylates eIF2a reducing translation of host and viral mRNA. Although infection with a chimeric <span class="hlt">West</span> Nile virus (WNV) efficiently induced PKR and eIF2a phosphorylation, infections with natural lineage 1 or 2 strains did not. Investigation of the mechanism of suppression showed that among the cellular PKR inhibitor proteins tested, only Nck, known to interact with inactive PKR, colocalized and co-immunoprecipitated with PKR in WNV-infected cells and PKR phosphorylation did not increase in infected Nck1,2-/- cells. Several WNV stem-loop RNAs efficiently <span class="hlt">activated</span> PKR in vitro but not in infected cells. WNV infection did not interfere with intracellular PKR <span class="hlt">activation</span> by poly(I:C) and similar virus yields were produced by control and PKR-/- cells. The results indicate that PKR phosphorylation is not <span class="hlt">actively</span> suppressed in WNV-infected cells but that PKR is not <span class="hlt">activated</span> by the viral dsRNA in infected cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AtmEn.118..135B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AtmEn.118..135B"><span>Sugars in <span class="hlt">Antarctic</span> aerosol</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barbaro, Elena; Kirchgeorg, Torben; Zangrando, Roberta; Vecchiato, Marco; Piazza, Rossano; Barbante, Carlo; Gambaro, Andrea</p> <p>2015-10-01</p> <p>The processes and transformations occurring in the <span class="hlt">Antarctic</span> aerosol during atmospheric transport were described using selected sugars as source tracers. Monosaccharides (arabinose, fructose, galactose, glucose, mannose, ribose, xylose), disaccharides (sucrose, lactose, maltose, lactulose), alcohol-sugars (erythritol, mannitol, ribitol, sorbitol, xylitol, maltitol, galactitol) and anhydrosugars (levoglucosan, mannosan and galactosan) were measured in the <span class="hlt">Antarctic</span> aerosol collected during four different sampling campaigns. For quantification, a sensitive high-pressure anion exchange chromatography was coupled with a single quadrupole mass spectrometer. The method was validated, showing good accuracy and low method quantification limits. This study describes the first determination of sugars in the <span class="hlt">Antarctic</span> aerosol. The total mean concentration of sugars in the aerosol collected at the "Mario Zucchelli" coastal station was 140 pg m-3; as for the aerosol collected over the <span class="hlt">Antarctic</span> plateau during two consecutive sampling campaigns, the concentration amounted to 440 and 438 pg m-3. The study of particle-size distribution allowed us to identify the natural emission from spores or from sea-spray as the main sources of sugars in the coastal area. The enrichment of sugars in the fine fraction of the aerosol collected on the <span class="hlt">Antarctic</span> plateau is due to the degradation of particles during long-range atmospheric transport. The composition of sugars in the coarse fraction was also investigated in the aerosol collected during the oceanographic cruise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C11D..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C11D..03P"><span><span class="hlt">Antarctic</span> Peninsula Tidewater Glacier Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pettit, E. C.; Scambos, T. A.; Haran, T. M.; Wellner, J. S.; Domack, E. W.; Vernet, M.</p> <p>2015-12-01</p> <p>The northern <span class="hlt">Antarctic</span> Peninsula (nAP, north of 66°S) is a north-south trending mountain range extending transverse across the prevailing westerly winds of the Southern Ocean resulting in an extreme <span class="hlt">west</span>-to-east precipitation gradient. Snowfall on the <span class="hlt">west</span> side of the AP is one to two orders of magnitude higher than the east side. This gradient drives short, steep, fast-flowing glaciers into narrow fjords on the <span class="hlt">west</span> side, while longer lower-sloping glaciers flow down the east side into broader fjord valleys. This pattern in ice dynamics affects ice-ocean interaction on timescales of decades to centuries, and shapes the subglacial topography and submarine bathymetry on timescales of glacial cycles. In our study, we calculate ice flux for the western and eastern nAP using a drainage model that incorporates the modern ice surface topography, the RACMO-2 precipitation estimate, and recent estimates of ice thinning. Our results, coupled with observed rates of ice velocity from InSAR (I. Joughin, personal communication) and Landsat 8 -derived flow rates (this study), provide an estimate of ice thickness and fjord depth in grounded-ice areas for the largest outlet glaciers. East-side glaciers either still terminate in or have recently terminated in ice shelves. Sedimentary evidence from the inner fjords of the western glaciers indicates they had ice shelves during LIA time, and may still have transient floating ice tongues (tabular berg calvings are observed). Although direct oceanographic evidence is limited, the high accumulation rate and rapid ice flux implies cold basal ice for the western nAP glaciers and therefore weak subglacial discharge relative to eastern nAP glaciers and or other tidewater fjord systems such as in Alaska. Finally, despite lower accumulation rates on the east side, the large elongate drainage basins result in a greater ice flux funneled through fewer deeper glaciers. Due to the relation between ice flux and erosion, these east-side glaciers</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28371192','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28371192"><span>Reconsidering connectivity in the sub-<span class="hlt">Antarctic</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moon, Katherine L; Chown, Steven L; Fraser, Ceridwen I</p> <p>2017-03-29</p> <p>Extreme and remote environments provide useful settings to test ideas about the ecological and evolutionary drivers of biological diversity. In the sub-<span class="hlt">Antarctic</span>, 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-<span class="hlt">Antarctic</span> landmasses. Here, we reconsider connectivity in the sub-<span class="hlt">Antarctic</span> 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 <span class="hlt">active</span> dispersers and more sedentary species. Overall, connectivity patterns in the sub-<span class="hlt">Antarctic</span> 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-<span class="hlt">Antarctic</span>, 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 <span class="hlt">activity</span> and changes to wind and ocean circulation, may alter sub-<span class="hlt">Antarctic</span> biodiversity patterns in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27713727','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27713727"><span>Microbial Community Structure of Subglacial Lake Whillans, <span class="hlt">West</span> Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Achberger, Amanda M; Christner, Brent C; Michaud, Alexander B; Priscu, John C; Skidmore, Mark L; Vick-Majors, Trista J</p> <p>2016-01-01</p> <p>Subglacial Lake Whillans (SLW) is located beneath ∼800 m of ice on the Whillans Ice Stream in <span class="hlt">West</span> Antarctica and was sampled in January of 2013, providing the first opportunity to directly examine water and sediments from an <span class="hlt">Antarctic</span> subglacial lake. To minimize the introduction of surface contaminants to SLW during its exploration, an access borehole was created using a microbiologically clean hot water drill designed to reduce the number and viability of microorganisms in the drilling water. Analysis of 16S rRNA genes (rDNA) amplified from samples of the drilling and borehole water allowed an evaluation of the efficacy of this approach and enabled a confident assessment of the SLW ecosystem inhabitants. Based on an analysis of 16S rDNA and rRNA (i.e., reverse-transcribed rRNA molecules) data, the SLW community was found to be bacterially dominated and compositionally distinct from the assemblages identified in the drill system. The abundance of bacteria (e.g., Candidatus Nitrotoga, Sideroxydans, Thiobacillus, and Albidiferax) and archaea (Candidatus Nitrosoarchaeum) related to chemolithoautotrophs was consistent with the oxidation of reduced iron, sulfur, and nitrogen compounds having important roles as pathways for primary production in this permanently dark ecosystem. Further, the prevalence of Methylobacter in surficial lake sediments combined with the detection of methanogenic taxa in the deepest sediment horizons analyzed (34-36 cm) supported the hypothesis that methane cycling occurs beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet. Large ratios of rRNA to rDNA were observed for several operational taxonomic units abundant in the water column and sediments (e.g., Albidiferax, Methylobacter, Candidatus Nitrotoga, Sideroxydans, and Smithella), suggesting a potentially <span class="hlt">active</span> role for these taxa in the SLW ecosystem. Our findings are consistent with chemosynthetic microorganisms serving as the ecological foundation in this dark subsurface environment, providing new</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5032586','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5032586"><span>Microbial Community Structure of Subglacial Lake Whillans, <span class="hlt">West</span> Antarctica</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Achberger, Amanda M.; Christner, Brent C.; Michaud, Alexander B.; Priscu, John C.; Skidmore, Mark L.; Vick-Majors, Trista J.; Adkins, W.</p> <p>2016-01-01</p> <p>Subglacial Lake Whillans (SLW) is located beneath ∼800 m of ice on the Whillans Ice Stream in <span class="hlt">West</span> Antarctica and was sampled in January of 2013, providing the first opportunity to directly examine water and sediments from an <span class="hlt">Antarctic</span> subglacial lake. To minimize the introduction of surface contaminants to SLW during its exploration, an access borehole was created using a microbiologically clean hot water drill designed to reduce the number and viability of microorganisms in the drilling water. Analysis of 16S rRNA genes (rDNA) amplified from samples of the drilling and borehole water allowed an evaluation of the efficacy of this approach and enabled a confident assessment of the SLW ecosystem inhabitants. Based on an analysis of 16S rDNA and rRNA (i.e., reverse-transcribed rRNA molecules) data, the SLW community was found to be bacterially dominated and compositionally distinct from the assemblages identified in the drill system. The abundance of bacteria (e.g., Candidatus Nitrotoga, Sideroxydans, Thiobacillus, and Albidiferax) and archaea (Candidatus Nitrosoarchaeum) related to chemolithoautotrophs was consistent with the oxidation of reduced iron, sulfur, and nitrogen compounds having important roles as pathways for primary production in this permanently dark ecosystem. Further, the prevalence of Methylobacter in surficial lake sediments combined with the detection of methanogenic taxa in the deepest sediment horizons analyzed (34–36 cm) supported the hypothesis that methane cycling occurs beneath the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet. Large ratios of rRNA to rDNA were observed for several operational taxonomic units abundant in the water column and sediments (e.g., Albidiferax, Methylobacter, Candidatus Nitrotoga, Sideroxydans, and Smithella), suggesting a potentially <span class="hlt">active</span> role for these taxa in the SLW ecosystem. Our findings are consistent with chemosynthetic microorganisms serving as the ecological foundation in this dark subsurface environment, providing new</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6528716','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6528716"><span><span class="hlt">Antarctic</span> terrestrial ecosystems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Walton, D.W.H.</p> <p>1987-01-01</p> <p>The Maritime and Continental <span class="hlt">Antarctic</span> terrestrial ecosystems are considered in the context of environmental impacts - habitat destruction, alien introductions, and pollution. Four types of pollution are considered: nutrients, radionuclides, inert materials, and noxious chemicals. Their ability to recover from perturbation is discussed in the light of present scientific knowledge, and the methods used to control impacts are reviewed. It is concluded that techniques of waste disposal are still inadequate, adequate training in environmental and conservation principles for <span class="hlt">Antarctic</span> personnel in many countries is lacking, and scientific investigations may be a much more serious threat than tourism to the integrity of these ecosystems. Some priorities crucial to future management are suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26ES...56a2005S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26ES...56a2005S"><span>Coulomb stress analysis of <span class="hlt">West</span> Halmahera earthquake mw=7.2 to mount Soputan and Gamalama volcanic <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sinaga, G. H. D.; Zarlis, M.; Sitepu, M.; Prasetyo, R. A.; Simanullang, A.</p> <p>2017-02-01</p> <p><span class="hlt">West</span> Halmahera is the convergency of three plates, namely the Philippines plate, the Eurasian plate, and the Pasific plate. The location of the <span class="hlt">West</span> Halmahera is located in the thress plates, so the Western Halmahera potentially earthquake-prone areas. Some events increased <span class="hlt">activity</span> of Mount Soputan and Mount Gamalama preceded by a massive earthquake. This research was conducted in the BMKG Region I Medan. This research uses Coulomb Stress Model. Coulomb Stress Model was used to show increasing and decreasing stress consequence from earthquake in the area of <span class="hlt">West</span> Halmahera. Data such as the earthquake magnitude, earthquake depth, and Focal Mechanism required as input models. The data obtained from BMKG, Global CMT, and PVMBG. The result of data analyzed show an increase in the coulomb stress distribution at Mount Soputan 0.023 bar and 0.007 bar in mountain Gamalama. This stress followed by increased volcanic <span class="hlt">activity</span> of the mount Soputan and mount Gamalama with freatic eruption type.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4685969','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4685969"><span><span class="hlt">Antarctic</span> subglacial lake exploration: first results and future plans</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Siegert, Martin J.; Priscu, John C.; Wadham, Jemma L.; Lyons, W. Berry</p> <p>2016-01-01</p> <p>After more than a decade of planning, three attempts were made in 2012–2013 to access, measure in situ properties and directly sample subglacial <span class="hlt">Antarctic</span> lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically <span class="hlt">active</span> lake at the coastal margin of <span class="hlt">West</span> Antarctica, obtaining samples that would later be used to prove the existence of microbial life and <span class="hlt">active</span> biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about <span class="hlt">Antarctic</span> subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future. PMID:26667917</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS53C1056K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS53C1056K"><span>Geophysical Characteristics of the Australian-<span class="hlt">Antarctic</span> Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, S. S.; Lin, J.; Park, S. H.; Choi, H.; Lee, S. M.</p> <p>2014-12-01</p> <p>Between 2011 and 2013, the Korea Polar Research Institute (KOPRI) conducted three consecutive geologic surveys at the little explored eastern ends of the Australian-<span class="hlt">Antarctic</span> Ridge (AAR) to characterize the tectonics, geochemistry, and hydrothermal <span class="hlt">activity</span> of this intermediate spreading system. Using the Korean icebreaker R/V Araon, the multi-disciplinary research team collected bathymetry, gravity, magnetics, and rock and water column samples. In addition, Miniature Autonomous Plume Recorders (MAPRs) were deployed at wax-core rock sampling sites to detect the presence of <span class="hlt">active</span> hydrothermal vents. Here we present a detailed analysis of a 300-km-long supersegment of the AAR to quantify the spatial variations in ridge morphology and robust axial and off-axis volcanisms. The ridge axis morphology alternates between rift valleys and axial highs within relatively short ridge segments. To obtain a geological proxy for regional variations in magma supply, we calculated residual mantle Bouguer gravity anomalies (RMBA), gravity-derived crustal thickness, and residual topography for seven sub-segments. The results of the analyses revealed that the southern flank of the AAR is associated with shallower seafloor, more negative RMBA, thicker crust, and/or less dense mantle than the conjugate northern flank. Furthermore, this north-south asymmetry becomes more prominent toward the KR1 supersegment of the AAR. The axial topography of the KR1 supersegment exhibits a sharp transition from axial highs at the western end to rift valleys at the eastern end, with regions of axial highs being associated with more magma supply as indicated by more negative RMBA. We also compare and contrast the characteristics of the AAR supersegment with that of other ridges of intermediate spreading rates, including the Juan de Fuca Ridge, Galápagos Spreading Center, and Southeast Indian Ridge <span class="hlt">west</span> of the Australian-<span class="hlt">Antarctic</span> Discordance, to investigate the influence of ridge-hotspot interaction on</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25856255','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25856255"><span>Ebola <span class="hlt">active</span> monitoring system for travelers returning from <span class="hlt">West</span> Africa—Georgia, 2014-2015.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Parham, Mary; Edison, Laura; Soetebier, Karl; Feldpausch, Amanda; Kunkes, Audrey; Smith, Wendy; Guffey, Taylor; Fetherolf, Romana; Sanlis, Kathryn; Gabel, Julie; Cowell, Alex; Drenzek, Cherie</p> <p>2015-04-10</p> <p>The Ebola virus disease (Ebola) epidemic in <span class="hlt">West</span> Africa has so far produced approximately 25,000 cases, more than 40 times the number in any previously documented Ebola outbreak. Because of the risk for imported disease from infected travelers, in October 2014 CDC recommended that all travelers to the United States from Ebola-affected countries receive enhanced entry screening and postarrival <span class="hlt">active</span> monitoring for Ebola signs or symptoms until 21 days after their departure from an Ebola-affected country. The state of Georgia began its <span class="hlt">active</span> monitoring program on October 25, 2014. The Georgia Department of Public Health (DPH) modified its existing, web-based electronic notifiable disease reporting system to create an Ebola <span class="hlt">Active</span> Monitoring System (EAMS). DPH staff members developed EAMS from conceptualization to implementation in 6 days. In accordance with CDC recommendations, "low (but not zero) risk" travelers are required to report their daily health status to DPH, and the EAMS dashboard enables DPH epidemiologists to track symptoms and compliance with <span class="hlt">active</span> monitoring. Through March 31, 2015, DPH monitored 1,070 travelers, and 699 (65%) used their EAMS traveler login instead of telephone or e-mail to report their health status. Medical evaluations were performed on 30 travelers, of whom three were tested for Ebola. EAMS has enabled two epidemiologists to monitor approximately 100 travelers daily, and to rapidly respond to travelers reporting signs and symptoms of potential Ebola virus infection. Similar electronic tracking systems might be useful for other jurisdictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2086L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2086L"><span>Synchronicity between ice retreat and phytoplankton bloom in circum-<span class="hlt">Antarctic</span> polynyas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Yun; Ji, Rubao; Jenouvrier, Stephanie; Jin, Meibing; Stroeve, Julienne</p> <p>2016-03-01</p> <p>Phytoplankton in <span class="hlt">Antarctic</span> coastal polynyas has a temporally short yet spatially variant growth window constrained by ice cover and day length. Using 18-year satellite measurements (1997-2015) of sea ice and chlorophyll concentrations, we assessed the synchronicity between the spring phytoplankton bloom and light availability, taking into account the ice cover and the incident solar irradiance, for 50 circum-<span class="hlt">Antarctic</span> coastal polynyas. The synchronicity was strong (i.e., earlier ice-adjusted light onset leads to earlier bloom and vice versa) in most of the western <span class="hlt">Antarctic</span> polynyas but weak in a majority of the eastern <span class="hlt">Antarctic</span> polynyas. The <span class="hlt">west</span>-east asymmetry is related to sea ice production rate: the formation of many eastern <span class="hlt">Antarctic</span> polynyas is associated with strong katabatic wind and high sea ice production rate, leading to stronger water column mixing that could damp phytoplankton blooms and weaken the synchronicity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1794C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1794C"><span>Evidence for an extensive <span class="hlt">Antarctic</span> Ice Sheet by 37 Ma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carter, Andrew; Riley, Teal; Hillenbrand, Claus-Dieter; Rittner, Martin</p> <p>2016-04-01</p> <p>We present observational evidence that both the East and <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheets had expanded to the coast by 37 Ma, predating, by at least 3 Myr, a major drop in atmospheric CO2 at the Eocene-Oligocene boundary widely considered responsible for <span class="hlt">Antarctic</span> Ice Sheet expansion. Our evidence comes from the provenance (geochronology, thermochronometry, mineralogy) of iceberg-rafted debris identified in Late Eocene marine sediments from (ODP) Leg 113 Site 696 in the NW Weddell Sea. The existence of an significant <span class="hlt">Antarctic</span> Ice Sheet in a Late Eocene high pCO2 world calls into question the role of atmospheric CO2 concentrations as the dominant mechanism for ice sheet expansion and whether topography and ocean circulation only play a secondary role.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5201157','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5201157"><span>An Evaluability Assessment of the <span class="hlt">West</span> Virginia Physical <span class="hlt">Activity</span> Plan, 2015: Lessons Learned for Other State Physical <span class="hlt">Activity</span> Plans</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shawley, Samantha; Owens, Sherry; Dyer, Angela; Bulger, Sean M.; Jones, Dina L.; Jones, Emily M.; Murphy, Emily; Olfert, Melissa D.; Elliott, Eloise</p> <p>2016-01-01</p> <p>Background The US National Physical <span class="hlt">Activity</span> Plan (NPAP) was released in 2009 as a national strategic plan to increase physical <span class="hlt">activity</span> (PA). The NPAP emphasized implementing state and local PA programs. Dissemination of information about NPAP has been limited, however. Community Context <span class="hlt">West</span> Virginia is a predominantly rural state with high rates of chronic diseases associated with physical inactivity. In 2015 an evaluability assessment (EA) of the <span class="hlt">West</span> Virginia Physical <span class="hlt">Activity</span> Plan (WVPAP) was conducted, and community stakeholders were invited to participate in updating the plan. Methods A good EA seeks stakeholder input, assists in identifying program areas that need improvement, and ensures that a full evaluation will produce useful information. Data for this EA were collected via national stakeholder interviews, document reviews, discussions among workgroups consisting of state and local stakeholders, and surveys to determine how well the WVPAP had been implemented. Outcome The EA highlighted the need for WVPAP leaders to 1) establish a specific entity to implement local PA plans, 2) create sector-specific logic models to simplify the WVPAP for local stakeholders, 3) evaluate the PA plan’s implementation frequently from the outset, 4) use quick and efficient engagement techniques with stakeholders when working with them to select strategies, tactics, and measurable outcomes, and 5) understand the elements necessary to implement, manage, and evaluate a good PA plan. Interpretation An EA process is recommended for other leaders of PA plans. Our project highlights the stakeholders’ desire to simplify the WVPAP so that it can be set up as a locally driven process that engages communities in implementation. PMID:28033092</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28348211','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28348211"><span>Evolution of the early <span class="hlt">Antarctic</span> ice ages.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liebrand, Diederik; de Bakker, Anouk T M; Beddow, Helen M; Wilson, Paul A; Bohaty, Steven M; Ruessink, Gerben; Pälike, Heiko; Batenburg, Sietske J; Hilgen, Frederik J; Hodell, David A; Huck, Claire E; Kroon, Dick; Raffi, Isabella; Saes, Mischa J M; van Dijk, Arnold E; Lourens, Lucas J</p> <p>2017-03-27</p> <p>Understanding the stability of the early <span class="hlt">Antarctic</span> ice cap in the geological past is of societal interest because present-day atmospheric CO2 concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution deep-sea oxygen isotope (δ(18)O) record from the South Atlantic Ocean spanning an interval between 30.1 My and 17.1 My ago. The record displays major oscillations in deep-sea temperature and <span class="hlt">Antarctic</span> ice volume in response to the ∼110-ky eccentricity modulation of precession. Conservative minimum ice volume estimates show that waxing and waning of at least ∼85 to 110% of the volume of the present East <span class="hlt">Antarctic</span> Ice Sheet is required to explain many of the ∼110-ky cycles. <span class="hlt">Antarctic</span> ice sheets were typically largest during repeated glacial cycles of the mid-Oligocene (∼28.0 My to ∼26.3 My ago) and across the Oligocene-Miocene Transition (∼23.0 My ago). However, the high-amplitude glacial-interglacial cycles of the mid-Oligocene are highly symmetrical, indicating a more direct response to eccentricity modulation of precession than their Early Miocene counterparts, which are distinctly asymmetrical-indicative of prolonged ice buildup and delayed, but rapid, glacial terminations. We hypothesize that the long-term transition to a warmer climate state with sawtooth-shaped glacial cycles in the Early Miocene was brought about by subsidence and glacial erosion in <span class="hlt">West</span> Antarctica during the Late Oligocene and/or a change in the variability of atmospheric CO2 levels on astronomical time scales that is not yet captured in existing proxy reconstructions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P51F..03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P51F..03M"><span><span class="hlt">Antarctic</span> analogs for Enceladus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murray, A. E.; Andersen, D. T.; McKay, C. P.</p> <p>2014-12-01</p> <p>Enceladus is a new world for Astrobiology. The Cassini discovery of the icy plume emanating from the South Polar region indicates an <span class="hlt">active</span> world, where detection of water, organics, sodium, and nano-particle silica in the plume strongly suggests that the source is a subsurface salty ocean reservoir. Recent gravity data from Cassini confirms the presence of a regional sea extending north to 50°S. An ocean habitat under a thick ice cover is perhaps a recurring theme in the Outer Solar System, but what makes Enceladus unique is that the plume jetting out into space is carrying samples of this ocean. Therefore, through the study of Enceladus' plumes we can gain new insights not only of a possible habitable world in the Solar Systems, but also about the formation and evolution of other icy-satellites. Cassini has been able to fly through this plume - effectively sampling the ocean. It is time to plan for future missions that do more detailed analyses, possibly return samples back to Earth and search for evidence of life. To help prepare for such missions, the need for earth-based analog environments is essential for logistical, methodological (life detection) and theoretical development. We have undertaken studies of two terrestrial environments that are close analogs to Enceladus' ocean: Lake Vida and Lake Untersee - two ice-sealed <span class="hlt">Antarctic</span> lakes that represent physical, chemical and possibly biological analogs for Enceladus. By studying the diverse biology and physical and chemical constraints to life in these two unique lakes we will begin to understand the potential habitability of Enceladus and other icy moons, including possible sources of nutrients and energy, which together with liquid water are the key ingredients for life. Analog research such as this will also enable us to develop and test new strategies to search for evidence of life on Enceladus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.C13A..06F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.C13A..06F"><span>Mapping <span class="hlt">Antarctic</span> Megadunes and Other Accumulation-related Features on the East <span class="hlt">Antarctic</span> Plateau</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fahnestock, M. A.; Shuman, C.; Scambos, T.; Albert, M.; Haran, T.; Courville, Z.; Bauer, R.</p> <p>2005-12-01</p> <p>Using both field observations and continent-wide remote sensing data sets, we characterize accumulation-related features on the Plateau, including the extent, variability, and likely formation processes of megadunes. A new 125-meter MODIS-based Mosaic of Antarctica (MOA), coupled with SAR imagery from the Radarsat <span class="hlt">Antarctic</span> Mapping Mission (RAMP; Jezek,1999) elevation profiles from ICESat, and compilations of mean accumulation (e.g., Vaughan et al., 1999; Davis et al., 2005) form the basis for the remote sensing analysis. Field measurements from ground penetrating radar, automatic weather stations, surface photos, snowpits, and shallow cores in two field seasons (November-December 2002 and January 2004) provide in situ and subsurface information on dune structure and a context for interpretation of fused remote sensing measurements. <span class="hlt">Antarctic</span> megadunes are linear stripe accumulations of fine-grained, wind-packed snow, forming 2 - 8 meter high, 1-2km wide ridges separated by 2-6 km of near-zero-accumulation `glaze' regions. Glaze surfaces overlie extremely metamorphosed firn, characterized by very coarse recrystallized grains and poorly expressed layering; remote sensing indicates that this type of firn is spatially dominant in a number of areas on the Plateau. Megadunes occur in high-altitude (2000-3500m ASL) low-accumulation (<5cm water-equivalent/year) regions of the East <span class="hlt">Antarctic</span> plateau, away from ridge crests and dome summits. They comprise a total area of 1.2 million km2, or roughly 20% of the East <span class="hlt">Antarctic</span> surface (higher than earlier estimates) but are absent (in the present climate) from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> or Greeland Ice Sheet surfaces. Ground-penetrating radar profiles coupled with simple models of snow accumulation reveal that the accumulation rate and the surface profile shape in the windward direction are intimately related for megadunes; this relationship is extended to all megadune areas by a comparison of ICESat profiles, the RAMP backscatter</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994PalOc...9.1017M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994PalOc...9.1017M"><span>A 600,000-year record of <span class="hlt">Antarctic</span> Bottom Water <span class="hlt">activity</span> inferred from sediment textures and structures in a sediment core from the Southern Brazil Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Massé, Laurent; FaugèRes, Jean-Claude; Bernat, Michel; Pujos, Annick; MéZerais, Marie-Laure</p> <p>1994-12-01</p> <p>At the northern exit of the Vema Channel, in the Southern Brazil Basin, deep currents linked with <span class="hlt">Antarctic</span> Bottom Water flow (AABW, below 4200 m) have formed contouritic accumulations along the continental rise. Lithologic and textural investigations were carried out on a Kullenberg core in order to establish a chronology of late Pleistocene-Holocene fluctuations in AABW flow. The core, spanning the last 600,000 years, was recovered from a field of sediment waves. The deposits consist of fine grained muds. Carbonate contents are very low because deposition takes place near the present-day carbonate compensation depth. The core stratigraphic framework is based on calcareous nannofossil and excess 230Th analyses. Two main types of facies can be identified: (1) yellowish brown muds, with frequent manganese enrichments forming dark laminae, and (2) homogeneous gray-green muds. Two indicators of paleocurrent <span class="hlt">activity</span> have been considered: (1) erosional sediment features that give evidence for high amplitude and short-term current events, and (2) grain size fluctuations (percentage of panicles greater than 10 µm), indicating low amplitude and long-term variations. Two periods can be defined. The first one (circa 600 to circa 350 kyr B.P.) is characterized by an instability in current <span class="hlt">activity</span>, with strong flow events recorded as erosional surfaces. Long-term fluctuations reveal the existence of several episodes of increased velocity occurring approximately every 50 kyr. The second period (350 kyr B.P. to present) is marked by globally weaker current <span class="hlt">activity</span> and long-term fluctuations of lower amplitude and longer duration. Maximum velocities occur preferentially during periods of climatic cooling. These fluctuations might be correlated with the 100 kyr eccentricity cycle of the Earth's orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.207.1286G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.207.1286G"><span>Resistivity image beneath an area of <span class="hlt">active</span> methane seeps in the <span class="hlt">west</span> Svalbard continental slope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goswami, Bedanta K.; Weitemeyer, Karen A.; Minshull, Timothy A.; Sinha, Martin C.; Westbrook, Graham K.; Marín-Moreno, Héctor</p> <p>2016-11-01</p> <p>The Arctic continental margin contains large amounts of methane in the form of methane hydrates. The <span class="hlt">west</span> Svalbard continental slope is an area where <span class="hlt">active</span> methane seeps have been reported near the landward limit of the hydrate stability zone. The presence of bottom simulating reflectors (BSRs) on seismic reflection data in water depths greater than 600 m suggests the presence of free gas beneath gas hydrates in the area. Resistivity obtained from marine controlled source electromagnetic (CSEM) data provides a useful complement to seismic methods for detecting shallow hydrate and gas as they are more resistive than surrounding water saturated sediments. We acquired two CSEM lines in the <span class="hlt">west</span> Svalbard continental slope, extending from the edge of the continental shelf (250 m water depth) to water depths of around 800 m. High resistivities (5-12 Ωm) observed above the BSR support the presence of gas hydrate in water depths greater than 600 m. High resistivities (3-4 Ωm) at 390-600 m water depth also suggest possible hydrate occurrence within the gas hydrate stability zone (GHSZ) of the continental slope. In addition, high resistivities (4-8 Ωm) landward of the GHSZ are coincident with high-amplitude reflectors and low velocities reported in seismic data that indicate the likely presence of free gas. Pore space saturation estimates using a connectivity equation suggest 20-50 per cent hydrate within the lower slope sediments and less than 12 per cent within the upper slope sediments. A free gas zone beneath the GHSZ (10-20 per cent gas saturation) is connected to the high free gas saturated (10-45 per cent) area at the edge of the continental shelf, where most of the seeps are observed. This evidence supports the presence of lateral free gas migration beneath the GHSZ towards the continental shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6391J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6391J"><span>Cenozoic uplift on the <span class="hlt">West</span> Greenland margin: <span class="hlt">active</span> sedimentary basins in quiet Archean terranes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jess, Scott; Stephenson, Randell; Brown, Roderick</p> <p>2016-04-01</p> <p>The North Atlantic is believed by some authors to have experienced tectonically induced uplift within the Cenozoic. Examination of evidence, onshore and offshore, has been interpreted to imply the presence of kilometre scale uplift across the margins of the Barents Sea, North Sea, Baffin Bay and Greenland Sea. Development of topography on the <span class="hlt">West</span> Greenland margin (Baffin Bay), in particular, has been subject to much discussion and dispute. A series of low temperature thermochronological (AFT and AHe) studies onshore and interpretation of seismic architecture offshore have suggested uplift of the entire margin totalling ~3km. However, challenges to this work and recent analysis on the opposing margin (Baffin Island) have raised questions about the validity of this interpretation. The present work reviews and remodels the thermochronological data from onshore <span class="hlt">West</span> Greenland with the aim of re-evaluating our understanding of the margin's history. New concepts within the discipline, such as effect of radiation damage on Helium diffusivity, contemporary modelling approaches and denudational mapping are all utilised to investigate alternative interpretations to this margins complex post rift evolution. In contrast to earlier studies our new approach indicates slow protracted cooling across much of the region; however, reworked sedimentary samples taken from the Cretaceous Nuussuaq Basin display periods of rapid reheating and cooling. These new models suggest the Nuussuaq Basin experienced a tectonically <span class="hlt">active</span> Cenozoic, while the surrounding Archean basement remained quiet. Faults located within the basin appear to have been reactivated during the Palaeocene and Eocene, a period of well-documented inversion events throughout the North Atlantic, and may have resulted in subaerial kilometre scale uplift. This interpretation of the margin's evolution has wider implications for the treatment of low temperature thermochronological data and the geological history of the North</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ffcd.confE.150L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ffcd.confE.150L"><span>Diagnosing <span class="hlt">Antarctic</span> Fog</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lazzara, M. A.</p> <p>2010-07-01</p> <p>Fog affects aviation and other logistical operations in the <span class="hlt">Antarctic</span>; nevertheless limited studies have been conducted to understand fog behavior in this part of the world. A study has been conducted in the Ross Island region of Antarctica, the location of McMurdo Station and Scott Base - the main stations of the United States and New Zealand <span class="hlt">Antarctic</span> programs, respectively. Using tools such as multi-channel satellites observations and supported by in situ radiosonde and ground-based automatic weather station observations, combined with back trajectory and mesoscale numerical models, discover that austral summer fog events are "advective" in temperament. The diagnosis finds a primary source region from the southeast over the Ross Ice Shelf (over 72% of the cases studied) while a minority of cases point toward a secondary fog source region to the north along the Scott Coast of the Ross Sea with influences from the East <span class="hlt">Antarctic</span> Plateau. Part of this examination confirms existing anecdotes from forecasters and weather observers, while refuting others about fog and its behavior in this environment. This effort marks the beginning of our understanding of <span class="hlt">Antarctic</span> fog behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA111957','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA111957"><span><span class="hlt">Antarctic</span> Atmospheric Infrasound.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1981-11-30</p> <p>A summary is given of the project chronology and the reports describing our research in <span class="hlt">Antarctic</span> Atmospheric infrasound. Analysis of selected infrasonic signals is discussed and a list is given of all infrasonic waves received on the digital system with correlation coefficient greater than 0.6. (Author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23619351','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23619351"><span>Bioactive volatile organic compounds from <span class="hlt">Antarctic</span> (sponges) bacteria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Papaleo, Maria Cristiana; Romoli, Riccardo; Bartolucci, Gianluca; Maida, Isabel; Perrin, Elena; Fondi, Marco; Orlandini, Valerio; Mengoni, Alessio; Emiliani, Giovanni; Tutino, Maria Luisa; Parrilli, Ermenegilda; de Pascale, Donatella; Michaud, Luigi; Lo Giudice, Angelina; Fani, Renato</p> <p>2013-09-25</p> <p><span class="hlt">Antarctic</span> bacteria represent a reservoir of unexplored biodiversity, which, in turn, might be correlated to the synthesis of still undescribed bioactive molecules, such as antibiotics. In this work we have further characterized a panel of four marine <span class="hlt">Antarctic</span> bacteria able to inhibit the growth of human opportunistic multiresistant pathogenic bacteria belonging to the Burkholderia cepacia complex (responsible for the 'cepacia' syndrome in Cystic Fibrosis patients) through the production of a set of microbial Volatile Organic Compounds (mVOCs). A list of 30 different mVOCs synthesized under aerobic conditions by <span class="hlt">Antarctic</span> bacteria was identified by GC-SPME analysis. Cross-streaking experiments suggested that <span class="hlt">Antarctic</span> bacteria might also synthesize non-volatile molecules able to enhance the anti-Burkholderia <span class="hlt">activity</span>. The biosynthesis of such a mixture of mVOCs was very probably influenced by both the presence/absence of oxygen and the composition of media used to grow the <span class="hlt">Antarctic</span> strains. The antimicrobial <span class="hlt">activity</span> exhibited by <span class="hlt">Antarctic</span> strains also appeared to be more related to their taxonomical position rather than to the sampling site. Different Bcc bacteria were differently sensitive to the '<span class="hlt">Antarctic</span>' mVOCs and this was apparently related neither to the taxonomical position of the different strains nor to their source. The genome sequence of three new <span class="hlt">Antarctic</span> strains was determined revealing that only P. atlantica TB41 possesses some genes belonging to the nrps-pks cluster. The comparative genomic analysis performed on the genome of the four strains also revealed the presence of a few genes belonging to the core genome and involved in the secondary metabolites biosynthesis. Data obtained suggest that the antimicrobial <span class="hlt">activity</span> exhibited by <span class="hlt">Antarctic</span> bacteria might rely on a (complex) mixture of mVOCs whose relative concentration may vary depending on the growth conditions. Besides, it is also possible that the biosynthesis of these compounds might occur</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.7864W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.7864W"><span>Unveiling the <span class="hlt">Antarctic</span> subglacial landscape.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Warner, Roland; Roberts, Jason</p> <p>2010-05-01</p> <p> 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 <span class="hlt">Antarctic</span> 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. <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/325651','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/325651"><span>Addendum to the performance assessment analysis for low-level waste disposal in the 200 <span class="hlt">west</span> area <span class="hlt">active</span> burial grounds</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wood, M.I., Westinghouse Hanford</p> <p>1996-12-20</p> <p>An addendum was completed to the performance assessment (PA) analysis for the <span class="hlt">active</span> 200 <span class="hlt">West</span> Area low-level solid waste burial grounds. The addendum includes supplemental information developed during the review of the PA analysis, an ALARA analysis, a comparison of PA results with the Hanford Groundwater Protection Strategy, and a justification for the assumption of 500 year deterrence to the inadvertent intruder.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SolED...6..869A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SolED...6..869A"><span>Microbial biomass and basal respiration in Sub-<span class="hlt">Antarctic</span> and <span class="hlt">Antarctic</span> soils in the areas of some Russian polar stations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abakumov, E.; Mukhametova, N.</p> <p>2014-03-01</p> <p>Antarctica is the unique place for pedological investigations. Soils of Antarctica have been studied intensively during the last century. <span class="hlt">Antarctic</span> logistic provides the possibility to scientists access the terrestrial landscapes mainly in the places of polar stations. That is why the main and most detailed pedological investigations were conducted in Mc Murdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann hills and Schirmacher Oasis. Investigations were conducted during the 53rd and 55th Russian <span class="hlt">Antarctic</span> expeditions on the base of soil pits and samples collected in Sub-<span class="hlt">Antarctic</span> and <span class="hlt">Antarctic</span> regions. Soils of diverse <span class="hlt">Antarctic</span> landscapes were studied with aim to assess the microbial biomass level, basal respiration rates and metabolic <span class="hlt">activity</span> of microbial communities. The investigation conducted shows that soils of <span class="hlt">Antarctic</span> are quite different in profile organization and carbon content. In general, Sub-<span class="hlt">Antarctic</span> soils are characterized by more developed humus (sod) organo-mineral horizons as well as the upper organic layer. The most developed organic layers were revealed in peat soils of King-George Island, where its thickness reach even 80 cm. These soils as well as soils under guano are characterized by the highest amount of total organic carbon (TOC) 7.22-33.70%. Coastal and continental soils of <span class="hlt">Antarctic</span> are presented by less developed Leptosols, Gleysols, Regolith and rare Ornhitosol with TOC levels about 0.37-4.67%. The metabolic ratios and basal respiration were higher in Sub-<span class="hlt">Antarctic</span> soils than in <span class="hlt">Antarctic</span> ones which can be interpreted as result of higher amounts of fresh organic remnants in organic and organo-mineral horizons. Also the soils of King-George island have higher portion of microbial biomass (max 1.54 mg g-1) than coastal (max 0.26 mg g-1) and continental (max 0.22 mg g-1) <span class="hlt">Antarctic</span> soils. Sub-<span class="hlt">Antarctic</span> soils mainly differ from <span class="hlt">Antarctic</span> ones in increased organic layers thickness and total organic carbon content</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5125649','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5125649"><span>Macro-Scale Patterns in Upwelling/Downwelling <span class="hlt">Activity</span> at North American <span class="hlt">West</span> Coast</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Saldívar-Lucio, Romeo; Di Lorenzo, Emanuele; Nakamura, Miguel; Villalobos, Héctor; Lluch-Cota, Daniel; Del Monte-Luna, Pablo</p> <p>2016-01-01</p> <p>The seasonal and interannual variability of vertical transport (upwelling/downwelling) has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling <span class="hlt">activity</span> along the North American <span class="hlt">west</span> coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar <span class="hlt">activity</span>. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress). The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region. PMID:27893826</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27893826','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27893826"><span>Macro-Scale Patterns in Upwelling/Downwelling <span class="hlt">Activity</span> at North American <span class="hlt">West</span> Coast.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saldívar-Lucio, Romeo; Di Lorenzo, Emanuele; Nakamura, Miguel; Villalobos, Héctor; Lluch-Cota, Daniel; Del Monte-Luna, Pablo</p> <p>2016-01-01</p> <p>The seasonal and interannual variability of vertical transport (upwelling/downwelling) has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling <span class="hlt">activity</span> along the North American <span class="hlt">west</span> coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar <span class="hlt">activity</span>. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress). The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP54A..06T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP54A..06T"><span>Climatic Drivers of Past <span class="hlt">Antarctic</span> Ice Sheet Evolution Add Nonlinearly</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tigchelaar, M.; Timmermann, A.; Pollard, D.; Friedrich, T.; Heinemann, M.</p> <p>2015-12-01</p> <p>The <span class="hlt">Antarctic</span> ice sheet has varied substantially in shape and volume in the past, with evidence for strong regional differences in evolution history. Recent observations of change in the <span class="hlt">Antarctic</span> environment indicate that different regions respond differently to ongoing changes in global climate -- over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet strong increases in sub-shelf melt rates indicate a sensitivity to changes in ocean temperature and circulation, while in East Antarctica the mass balance is increasingly positive due to an increase in accumulation in response to rising temperatures. Modeling the long term evolution of the <span class="hlt">Antarctic</span> ice sheet can help address questions about its regional sensitivity to external forcing. We have conducted experiments with an established ice sheet model over the last eight glacial cycles using spatially and temporally varying climate forcing from an EMIC. These simulations indicate a glacial-interglacial amplitude of ~11m SLE. Using a series of sensitivity experiments we address the dominant climatic forcing of this evolution. While sea level changes are the main driver of grounding line movement, they alone are not sufficient to explain the full glacial amplitude. Local insolation changes contribute to the initiation of terminations, while accumulation and sub-shelf melt changes feed back positively and negatively respectively onto the ice sheet evolution. This implies that climatic drivers add nonlinearly and the full spectrum of climate forcing needs to be considered when evaluating the sensitivity of the <span class="hlt">Antarctic</span> ice sheet to past and future climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S51B2346M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S51B2346M"><span>Reflection seismic investigation of the geodynamically <span class="hlt">active</span> <span class="hlt">West</span> -Bohemia/Vogtland region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mullick, N.; Buske, S.; Shapiro, S. A.; Wigger, P.</p> <p>2013-12-01</p> <p>The <span class="hlt">West</span> Bohemia-Vogtland region in central Europe attracts much scientific interest due to recurrent earthquake swarms and continuous exhalation of CO2 dominated fluid from the subsurface. Seismological and geochemical studies reveal (1) significant upper mantle derived content of the emitted fluid, (2) an updoming of the MOHO below that area (3) possible existence of a magmatic fluid reservoir in the upper mantle and (4) fluid <span class="hlt">activity</span> as a possible trigger for the swarm earthquakes. In this study the subsurface structure beneath the region is investigated by reprocessing the deep reflection seismic profile 9HR, which runs almost directly across the swarm area. The migrated image confirms the upwelling of the MOHO known from receiver function studies. Directly below one of the major gas escape centres, channel like fault structures are observed which seem to have their roots at the MOHO. They may represent deep reaching degassing channels that allow direct transport of mantle-derived fluid. The middle and lower crust appears highly fractured below the swarm area. This may result in mantle fluid ascending through the crust and then getting blocked in the crust. Such blockage could result in building up of an over-pressured fluid zone at the bottom of near surface rocks. After a critical state is reached, the over-pressured fluid may have sufficient energy to force its way above into near surface rocks and to trigger seismicity. Since the swarm seismicity is found to be restricted along a plane only, such intrusion might have taken place along a semi-permeable zone that extends from the fractured lower crust into the near surface rocks. A comparison of the spatio-temporal evolution of the recent swarms in the years 2000 and 2008 with the subsurface reflectivity shows that in both cases the swarm <span class="hlt">activity</span> initiates at the upper edge of a highly diffuse reflectivity zone, moves upward, bends at a bright spot above and finally stops after travelling a few kilometers</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..278M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..278M"><span>Reflection seismic investigation of the geodynamically <span class="hlt">active</span> <span class="hlt">West</span>-Bohemia/Vogtland region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mullick, Nirjhar; Buske, Stefan</p> <p>2013-04-01</p> <p>The <span class="hlt">West</span> Bohemia-Vogtland region in central Europe attracts much scientific interest due to recurrent earthquake swarms and continuous exhalation of CO2 dominated fluid from the subsurface. Seismological and geochemical studies reveal 1) significant upper mantle derived content of the emitted fluid, 2) an updoming of the MOHO below that area 3) possible existence of a magmatic fluid reservoir in the upper mantle and 4) fluid <span class="hlt">activity</span> as a possible trigger for the swarm earthquakes. In this study the subsurface structure beneath the region is investigated by reprocessing the deep reflection seismic profile 9HR, which runs almost directly across the swarm area. The migrated image confirms the upwelling of the MOHO known from receiver function studies. Directly below one of the major gas escape centres, channel like fault structures are observed which seem to have their roots at the MOHO. They may represent deep reaching degassing channels that allow direct transport of mantle-derived fluid. The middle and lower crust appears highly fractured below the swarm area. This may result in mantle fluid ascending through the crust and then getting blocked in the crust. Such blockage could result in building up of an over-pressured fluid zone at the bottom of near surface rocks. After a critical state is reached, the over-pressured fluid may have sufficient energy to force its way above into near surface rocks and to trigger seismicity. Since the swarm seismicity is found to be restricted along a plane only, such intrusion might have taken place along a semi-permeable zone that extends from the fractured lower crust into the near surface rocks. A comparison of the spatio-temporal evolution of the recent swarms in the years 2000 and 2008 with the subsurface reflectivity shows that in both cases the swarm <span class="hlt">activity</span> initiates at the upper edge of a highly diffuse reflectivity zone, moves upward, bends at a bright spot above and finally stops after travelling a few kilometers along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5921100','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5921100"><span>Differences between <span class="hlt">Antarctic</span> and non-<span class="hlt">Antarctic</span> meteorites: An assessment</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Koeberl, C. ); Cassidy, W.A. )</p> <p>1991-01-01</p> <p>The discovery of a statistically significant number of meteorites in Antarctica over the past 20 years has posed many questions. One of the most intriguing suggestions that came up during the study of the <span class="hlt">Antarctic</span> samples was that there might be a difference between the parent populations of <span class="hlt">Antarctic</span> and non-<span class="hlt">Antarctic</span> samples was that there might be a difference between the parent populations of <span class="hlt">Antarctic</span> and non-<span class="hlt">Antarctic</span> meteorites. This interpretation was put forward after the detection of a significant difference in the abundances of volatile and mobile trace elements in H, L, and C chondrites and achondrites. Other major differences include the occurrence of previously rare or unknown meteorites, different meteorite-type frequencies, petrographic characteristics, oxygen isotopic compositions, and smaller average masses. Not all differences between the <span class="hlt">Antarctic</span> and non-<span class="hlt">Antarctic</span> meteorite populations can be explained by weathering, pairing, or different collection procedures. Variable trace element abundances and distinct differences in the thermal history and thermoluminescence characteristics have to be interpreted as being pre-terrestrial in origin. Such differences imply the existence of meteoroid streams, whose existence poses problems in the framework of our current knowledge of celestial mechanics. In this paper we summarize the contributions in this series and provide a review of the current state of the question for the reality and cause of differences between <span class="hlt">Antarctic</span> and non-<span class="hlt">Antarctic</span> meteorites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6755H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6755H"><span>Modelling the Isotopic Response to <span class="hlt">Antarctic</span> Ice Sheet Change During the Last Interglacial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holloway, Max; Sime, Louise; Singarayer, Joy; Tindall, Julia; Valdes, Paul</p> <p>2015-04-01</p> <p>Ice sheet changes can exert major control over spatial water isotope variations in <span class="hlt">Antarctic</span> surface snow. Consequently a significant mass loss or gain of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) would be expected to cause changes in the water isotope record across <span class="hlt">Antarctic</span> ice core sites. Analysis of sea level indicators for the last interglacial (LIG), around 125 to 128 ka, suggest a global sea level peak 6 to 9 m higher than present. Recent NEEM Greenland ice core results imply that Greenland likely provided a modest ~2m contribution towards this global sea level rise. This implies that a WAIS contribution is necessary to explain the LIG sea level maxima. In addition, <span class="hlt">Antarctic</span> ice core records suggest that <span class="hlt">Antarctic</span> air temperatures during the LIG were up to 6°C warmer than present. Climate models have been unable to recreate such warmth when only orbital and greenhouse gas forcing are considered. Thus changes to the <span class="hlt">Antarctic</span> ice sheet and ocean circulation may be required to reconcile model simulations with ice core data. Here we model the isotopic response to differing WAIS deglaciation scenarios, freshwater hosing, and sea ice configurations using a fully coupled General Circulation Model (GCM) to help interpret <span class="hlt">Antarctic</span> ice core records over the LIG. This approach can help isolate the contribution of individual processes and feedbacks to final isotopic signals recorded in <span class="hlt">Antarctic</span> ice cores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP22B..04I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP22B..04I"><span>Climate sensitivity of the <span class="hlt">Antarctic</span> ventilation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ito, T.; Lynch-Stieglitz, J.</p> <p>2014-12-01</p> <p>Simple box models of ocean-atmosphere carbon cycle predict that <span class="hlt">Antarctic</span> ventilation can regulate the steady-state atmospheric CO2 through its control over the biological carbon storage in the deep ocean. A weakened upwelling would lead to a more complete nutrient utilization at the surface and an increased retention of biogenic carbon in the deep ocean. We perform a suite of numerical sensitivity experiments using a coupled seaice and global ocean circulation model to better understand what regulates the <span class="hlt">Antarctic</span> ventilation and its link to glacial climate. The model is first spun up with a modern climatological surface forcing, which exhibits a multi-decadal oscillation, where the Southern Ocean is heated from below through the influx of warm and salty North Atlantic Deep Water, and the accumulation of heat induces intermittent convective overturning. Through the sensitivity experiments, we explore and illustrate the rich and complex behavior of the <span class="hlt">Antarctic</span> ventilation and its response to the northern sinking, the surface wind stress, and the global mean temperature. When the northern sinking is weakened by a freshwater perturbation, the intermittent convection events are suppressed as the heat source is reduced. When the atmospheric temperature is lowered uniformly, the <span class="hlt">Antarctic</span> seaice extent increases and the southern overturning weakens on centennial timescales. However, the convective overturning rebounds on the millennial timescale if the northern sinking is <span class="hlt">active</span>. We will discuss implications of our results to the deep ventilation of the Southern Ocean and its impact on the ocean carbon storage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.G41A..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.G41A..07W"><span>GPS Measurement of Neotectonic Motions in the <span class="hlt">Antarctic</span> Interior</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Willis, M. J.; Wilson, T. J.; James, T.</p> <p>2004-12-01</p> <p>Campaign GPS measurements made between 1996 and 2004 are used to describe the crustal velocity field in southern Victoria Land, Antarctica. The GPS network stretches along the Transantarctic Mountains from the region of the David Glacier near 75° S to the Byrd Glacier region at 81.5° S and encompasses volcanic islands within the adjacent <span class="hlt">West</span> <span class="hlt">Antarctic</span> Rift. It is composed of 32 sites, six of which have been upgraded to run continuously. The continuous stations have been installed to separate long term secular trends in vertical motion from short period seasonal signals. The array was designed to record intraplate neotectonic motions associated with Glacial Isostatic Adjustment (GIA) and possible neotectonic motions between East and <span class="hlt">West</span> Antarctica. There is conflicting evidence on the degree of contemporary neotectonic <span class="hlt">activity</span> in the study area. Seismic reflection profiles document faults cutting through the sedimentary column and reaching the seafloor in the north-south trending Terror Rift in the western Ross Sea, yet seismicity has yet to be detected in this region. GIA models predict that uplift in the region will have a secular motion of between 0 and 4mm per year. This uplift will be associated with a small amount of horizontal motion. GPS records an average horizontal motion of the westernmost sites in our network of 14.4mm/yr towards 149° east. When this average motion is removed from the motion of all the network sites, to approximate an East <span class="hlt">Antarctic</span> cratonic reference frame, a significant residual motion of coastal and offshore sites is observed. This residual motion is between 1 and 3 mm/yr towards the east-northeast, perpendicular to the trend of the Transantarctic Mountains and the Terror Rift. This motion may be accommodated by faults that occur onshore in the frontal zone of the Transantarctic Mountains and/or by faults within the Terror Rift. Reasonable models of crustal response to GIA with a laterally homogeneous Earth and the D91 ice sheet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2007/1047/srp/srp070/of2007-1047srp070.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2007/1047/srp/srp070/of2007-1047srp070.pdf"><span>Permafrost and <span class="hlt">active</span> layer monitoring in the maritime <span class="hlt">Antarctic</span>: Preliminary results from CALM sites on Livingston and Deception Islands</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ramos, M.; Vieira, G.; Blanco, J.J.; Hauck, C.; Hidalgo, M.A.; Tome, D.; Nevers, M.; Trindade, A.</p> <p>2007-01-01</p> <p>This paper describes results obtained from scientific work and experiments performed on Livingston and Deception Islands. Located in the South Shetland Archipelago, these islands have been some of the most sensitive regions over the last 50 years with respect to climate change with a Mean Annual Air Temperature (MAAT) close to -2 ºC. Three Circumpolar <span class="hlt">Active</span> Layer Monitoring (CALM) sites were installed to record the thermal regime and the behaviour of the <span class="hlt">active</span> layer in different places with similar climate, but with different soil composition, porosity, and water content. The study’s ultimate aim is to document the influence of climate change on permafrost degradation. Preliminary results, obtained in 2006, on maximum <span class="hlt">active</span>-layer thickness (around 40 cm in the CALM of Deception Island), <span class="hlt">active</span> layer temperature evolution, snow thickness, and air temperatures permit early characterization of energy exchange mechanisms between the ground and the atmosphere in the CALM-S sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4885691','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4885691"><span>Analysis of Culex and Aedes mosquitoes in southwestern Nigeria revealed no <span class="hlt">West</span> Nile virus <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sule, Waidi Folorunso; Oluwayelu, Daniel Oladimeji</p> <p>2016-01-01</p> <p>Introduction Amplification and transmission of <span class="hlt">West</span> Nile virus (WNV) by mosquitoes are driven by presence and number of viraemic/susceptible avian hosts. Methods In order to predict risk of WNV infection to humans, we collected mosquitoes from horse stables in Lagos and Ibadan, southwestern Nigeria. The mosquitoes were sorted and tested in pools with real-time RT-PCR to detect WNV (or flavivirus) RNA using WNV-specific primers and probes, as well as, pan-flavivirus-specific primers in two-step real-time RT-PCR. Minimum infection rate (MIR) was used to estimate mosquito infection rate. Results Only two genera of mosquitoes were caught (Culex, 98.9% and Aedes, 1.0%) totalling 4,112 females. None of the 424 mosquito pools tested was positive for WNV RNA; consequently the MIR was zero. Sequencing and BLAST analysis of amplicons detected in pan-flavivirus primer-mediated RT-PCR gave a consensus sequence of 28S rRNA of Culex quinquefasciatus suggesting integration of flaviviral RNA into mosquito genome. Conclusion While the latter finding requires further investigation, we conclude there was little or no risk of human infection with WNV in the study areas during sampling. There was predominance of Culex mosquito, a competent WNV vector, around horse stables in the study areas. However, mosquito surveillance needs to continue for prompt detection of WNV <span class="hlt">activity</span> in mosquitoes. PMID:27279943</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4658406','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4658406"><span>Larvicidal <span class="hlt">Activity</span> of Nerium oleander against Larvae <span class="hlt">West</span> Nile Vector Mosquito Culex pipiens (Diptera: Culicidae)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>El-Akhal, Fouad; Guemmouh, Raja; Ez Zoubi, Yassine; El Ouali Lalami, Abdelhakim</p> <p>2015-01-01</p> <p>Background. Outbreaks of the <span class="hlt">West</span> Nile virus infection were reported in Morocco in 1996, 2003, and 2010. Culex pipiens was strongly suspected as the vector responsible for transmission. In the North center of Morocco, this species has developed resistance to synthetic insecticides. There is an urgent need to find alternatives to the insecticides as natural biocides. Objective. In this work, the insecticidal <span class="hlt">activity</span> of the extract of the local plant Nerium oleander, which has never been tested before in the North center of Morocco, was studied on larval stages 3 and 4 of Culex pipiens. Methods. Biological tests were realized according to a methodology inspired from standard World Health Organization protocol. The mortality values were determined after 24 h of exposure and LC50 and LC90 values were calculated. Results. The extract had toxic effects on the larvae of culicid mosquitoes. The ethanolic extract of Nerium oleander applied against the larvae of Culex pipiens has given the lethal concentrations LC50 and LC90 in the order of 57.57 mg/mL and 166.35 mg/mL, respectively. Conclusion. This investigation indicates that N. oleander could serve as a potential larvicidal, effective natural biocide against mosquito larvae, particularly Culex pipiens. PMID:26640701</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040120030&hterms=Protozoa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DProtozoa','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040120030&hterms=Protozoa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DProtozoa"><span>Viruses in <span class="hlt">Antarctic</span> lakes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kepner, R. L. Jr; Wharton, R. A. Jr; Suttle, C. A.; Wharton RA, J. r. (Principal Investigator)</p> <p>1998-01-01</p> <p>Water samples collected from four perennially ice-covered <span class="hlt">Antarctic</span> lakes during the austral summer of 1996-1997 contained high densities of extracellular viruses. Many of these viruses were found to be morphologically similar to double-stranded DNA viruses that are known to infect algae and protozoa. These constitute the first observations of viruses in perennially ice-covered polar lakes. The abundance of planktonic viruses and data suggesting substantial production potential (relative to bacteria] secondary and photosynthetic primary production) indicate that viral lysis may be a major factor in the regulation of microbial populations in these extreme environments. Furthermore, we suggest that <span class="hlt">Antarctic</span> lakes may be a reservoir of previously undescribed viruses that possess novel biological and biochemical characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000040793','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000040793"><span><span class="hlt">Antarctic</span> Meteorite Newsletter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lindstrom, Marilyn</p> <p>2000-01-01</p> <p>This newsletter contains something for everyone! It lists classifications of about 440 meteorites mostly from the 1997 and 1998 ANSMET (<span class="hlt">Antarctic</span> 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).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000013618&hterms=photochemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dphotochemistry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000013618&hterms=photochemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dphotochemistry"><span><span class="hlt">Antarctic</span> Photochemistry: Uncertainty Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stewart, Richard W.; McConnell, Joseph R.</p> <p>1999-01-01</p> <p>Understanding the photochemistry of the <span class="hlt">Antarctic</span> region is important for several reasons. Analysis of ice cores provides historical information on several species such as hydrogen peroxide and sulfur-bearing compounds. The former can potentially provide information on the history of oxidants in the troposphere and the latter may shed light on DMS-climate relationships. Extracting such information requires that we be able to model the photochemistry of the <span class="hlt">Antarctic</span> troposphere and relate atmospheric concentrations to deposition rates and sequestration in the polar ice. This paper deals with one aspect of the uncertainty inherent in photochemical models of the high latitude troposphere: that arising from imprecision in the kinetic data used in the calculations. Such uncertainties in <span class="hlt">Antarctic</span> models tend to be larger than those in models of mid to low latitude clean air. One reason is the lower temperatures which result in increased imprecision in kinetic data, assumed to be best characterized at 298K. Another is the inclusion of a DMS oxidation scheme in the present model. Many of the rates in this scheme are less precisely known than are rates in the standard chemistry used in many stratospheric and tropospheric models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18664106','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18664106"><span>[Helminths of <span class="hlt">Antarctic</span> fishes].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rocka, Anna</p> <p>2008-01-01</p> <p><span class="hlt">Antarctic</span> fishes are represented by sharks, skates (Chondrichthyes) and bony fishes (Teleostei). Teleosts play an important role in the completion of life cycles of many helminth species. They serve as either definitive or intermediate and paratenic hosts. Chondrichthyes are definitive hosts only. Seventy three helminth species occur as the adult stage in fishes: Digenea (45), Cestoda (14), Nematoda (6), Acanthocephala (8), Also, 11 larval stages of Cestoda (7) and Nematoda (4) are known, together with 7 species of Acanthocephala in the cystacanth stage. One digenean species, Otodistomum cestoides, matures in skates. Among cestodes maturing in fishes only one, Parabothriocephalus johnstoni, occurs in a bony fish, Macrourus whitsoni. <span class="hlt">Antarctic</span> Chondrichthyes are not infected with nematodes and acanthocephalans. Cestode larvae from teleosts belong to Tetraphyllidea (parasites of skates), and Tetrabothriidae and Diphyllobothriidae (parasites of birds and mammals). Larval nematodes represent Anisakidae, parasites of fishes, birds and mammals. Acanthocephalan cystacanths mature in pinnipeds and birds. The majority of parasites maturing in <span class="hlt">Antarctic</span> fishes are endemics. Only 4 digenean and one nematode species, Hysterothylacium aduncum, are cosmopolitan. All acanthocephalans, almost all digeneans, the majority of cestodes and some nematodes occur mainly or exclusively in benthic fishes. Specificity of the majority of helminths utilizing teleosts as intermediate and/or paratenic hosts is low. Among parasites using fishes as definitive hosts, all Cestoda, most Digenea and Nematoda, and almost all Acanthocephala have a range of hosts restricted to one order or even to 1-2 host species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019356','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019356"><span>Thermoluminescence and <span class="hlt">Antarctic</span> meteorites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sears, D. W. G.; Hasan, F. A.</p> <p>1986-01-01</p> <p>The level of natural thermoluminescence (TL) in meteorites is the result of competition between build-up, due to exposure to cosmic radiation, and thermal decay. <span class="hlt">Antarctic</span> meteorites tend to have lower natural TL than non-<span class="hlt">Antarctic</span> meteorites because of their generally larger terrestrial ages. However, since a few observed falls have low TL due to a recent heating event, such as passage within approximately 0.7 astronomical units of the Sun, this could also be the case for some <span class="hlt">Antarctic</span> meteorites. Dose rate variations due to shielding, heating during atmospheric passage, and anomalous fading also cause natural TL variations, but the effects are either relatively small, occur infrequently, or can be experimentally circumvented. The TL sensitivity of meteorites reflects the abundance and nature of the feldspar. Thus intense shock, which destroys feldspar, causes the TL sensitivity to decrease by 1 to 2 orders of magnitude, while metamorphism, which generates feldspar through the devitrification of glass, causes TL sensitivity to increase by a factor of approximately 10000. The TL-metamorphism relationship is particularly strong for the lowest levels of metamorphism. The order-disorder transformation in feldspar also affect the TL emission characteristics and thus TL provides a means of paleothermometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22072308','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22072308"><span>Leishmanicidal and antitumoral <span class="hlt">activities</span> of endophytic fungi associated with the <span class="hlt">Antarctic</span> angiosperms Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Santiago, Iara F; Alves, Tânia M A; Rabello, Ana; Sales Junior, Policarpo A; Romanha, Alvaro J; Zani, Carlos L; Rosa, Carlos A; Rosa, Luiz H</p> <p>2012-01-01</p> <p>A total of 564 isolates of endophytic fungi were recovered from the plants Deschampsia antarctica and Colobanthus quitensis collected from Antarctica. The isolates were screened against parasites Leishmania amazonensis and Trypanosoma cruzi and against the human tumour cell lines. Of the 313 fungal isolates obtained from D. antarctica and 251 from C. quitensis, 25 displayed biological <span class="hlt">activity</span>. Nineteen extracts displayed leishmanicidal <span class="hlt">activity</span>, and six inhibited the growth of at least one tumour cell line. These fungi belong to 19 taxa of the genera Alternaria, Antarctomyces, Cadophora, Davidiella, Helgardia, Herpotrichia, Microdochium, Oculimacula, Phaeosphaeria and one unidentified fungus. Extracts of 12 fungal isolates inhibited the proliferation of L. amazonesis at a low IC(50) of between 0.2 and 12.5 μg ml(-1). The fungus Phaeosphaeria herpotrichoides displayed only leishmanicidal <span class="hlt">activity</span> with an IC(50) of 0.2 μg ml(-1), which is equivalent to the inhibitory value of amphotericin B. The extract of Microdochium phragmitis displayed specific cytotoxic <span class="hlt">activity</span> against the UACC-62 cell line with an IC(50) value of 12.5 μg ml(-1). Our results indicate that the unique angiosperms living in Antarctica shelter an interesting bioactive fungal community that is able to produce antiprotozoal and antitumoral molecules. These molecules may be used to develop new leishmanicidal and anticancer drugs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70016071','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70016071"><span>Recent uplift and hydrothermal <span class="hlt">activity</span> at Tangkuban Parahu volcano, <span class="hlt">west</span> Java, Indonesia</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dvorak, J.; Matahelumual, J.; Okamura, A.T.; Said, H.; Casadevall, T.J.; Mulyadi, D.</p> <p>1990-01-01</p> <p>Tangkuban Parahu is an <span class="hlt">active</span> stratovolcano located 17 km north of the city of Bandung in the province <span class="hlt">west</span> Java, Indonesia. All historical eruptive <span class="hlt">activity</span> at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal <span class="hlt">activity</span>, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased hydrothermal and earthquake <span class="hlt">activity</span> occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40-50 microradians per year. After the 1983 phreatic <span class="hlt">activity</span>, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m3 per year; from 1983 to 1986 it averaged about 0.4 million m3 per year. Possible causes for this uplift are increased pressure within a very</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRF..122..153A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRF..122..153A"><span>Links between atmosphere, ocean, and cryosphere from two decades of microseism observations on the <span class="hlt">Antarctic</span> Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anthony, Robert E.; Aster, Richard C.; McGrath, Daniel</p> <p>2017-01-01</p> <p>The lack of landmasses, climatological low pressure, and strong circumpolar westerly winds between the latitudes of 50°S to 65°S produce exceptional storm-driven wave conditions in the Southern Ocean. This combination makes the <span class="hlt">Antarctic</span> Peninsula one of Earth's most notable regions of high-amplitude wave <span class="hlt">activity</span> and thus, ocean-swell-driven microseism noise in both the primary (direct wave-coastal region interactions) and secondary (direct ocean floor forcing due to interacting wave trains) period bands. Microseism observations are examined across 23 years (1993-2015) from Palmer Station (PMSA), on the <span class="hlt">west</span> coast of the <span class="hlt">Antarctic</span> Peninsula, and from East Falkland Island (EFI). These records provide a spatially integrative measure of both Southern Ocean wave amplitudes and the interactions between ocean waves and the solid Earth in the presence of sea ice, which can reduce wave coupling with the continental shelf. We utilize a spatiotemporal correlation-based approach to illuminate how the distribution of sea ice influences seasonal microseism power. We characterize primary and secondary microseism power due to variations in sea ice and find that primary microseism energy is both more sensitive to sea ice and more capable of propagating across ocean basins than secondary microseism energy. During positive phases of the Southern Annular Mode, sea ice is reduced in the Bellingshausen Sea and overall storm <span class="hlt">activity</span> in the Drake Passage increases, thus strongly increasing microseism power levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.3433K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.3433K"><span>Stratospheric variability of wave <span class="hlt">activity</span> and parameters in equatorial coastal and tropical sites during the <span class="hlt">West</span> African monsoon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kafando, P.; Chane-Ming, F.; Petitdidier, M.</p> <p>2016-12-01</p> <p>Recent numerical studies in stratospheric dynamics and its variability as well as climate, have highlighted the need of more observational analyses to improve simulation of the <span class="hlt">West</span> African monsoon (WAM). In this paper, <span class="hlt">activity</span> and spectral characteristics of short-scale vertical waves (wavelengths <4 km) are analysed in equatorial coastal and tropical lower stratosphere during the WAM. A first detailed description of such waves over <span class="hlt">West</span> Africa is derived from high-resolution vertical profiles of temperature and horizontal wind obtained during Intensive Observation Period of the African Monsoon Multidisciplinary Analyses (AMMA) Campaign 2006. Monthly variation of wave energy density is revealed to trace the progression of the inter-tropical convergence zone (ITCZ) over <span class="hlt">West</span> Africa. Mesoscale inertia gravity-waves structures with vertical and horizontal wavelengths of 1.5-2.5 and 400-1100 km respectively and intrinsic frequencies of 1.1-2.2 f or periods <2 days are observed in the tropical LS with intense <span class="hlt">activity</span> during July and August when the WAM is installed over the tropical <span class="hlt">West</span> Africa. Over equatorial region, gravity waves with intrinsic frequencies of 1.4-4 f or periods <5.2 days, vertical wavelength of 2.1 km and long horizontal wavelengths of 1300 km are intense during the WAM coastal phase. From July to October, gravity waves with intrinsic frequencies of 1.2-3.8 f or periods <6 days, vertical wavelength of 2.1 km and horizontal wavelengths of 1650 km are less intense during the WAM Sahelian phase of the WAM, March-June. Unlike potential energy density, kinetic energy density is observed to be a good proxy for the <span class="hlt">activity</span> of short-scale vertical waves during the WAM because quasi-inertial waves are dominant. Long-term wave <span class="hlt">activity</span> variation from January 2001 to December 2009, highlights strong year-to-year variation superimposed on convective <span class="hlt">activity</span> and quasi-biennial oscillation-like variations especially above tropical stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27004109','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27004109"><span>Screening of microorganisms from <span class="hlt">Antarctic</span> surface water and cytotoxicity metabolites from <span class="hlt">Antarctic</span> microorganisms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zheng, Lanhong; Yang, Kangli; Liu, Jia; Sun, Mi; Zhu, Jiancheng; Lv, Mei; Kang, Daole; Wang, Wei; Xing, Mengxin; Li, Zhao</p> <p>2016-03-01</p> <p>The <span class="hlt">Antarctic</span> is a potentially important library of microbial resources and new bioactive substances. In this study, microorganisms were isolated from surface water samples collected from different sites of the <span class="hlt">Antarctic</span>. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay-based cytotoxicity-tracking method was used to identify <span class="hlt">Antarctic</span> marine microorganism resources for antitumor lead compounds. The results showed that a total of 129 <span class="hlt">Antarctic</span> microorganism strains were isolated. Twelve strains showed potent cytotoxic <span class="hlt">activities</span>, among which a Gram-negative, rod-shaped bacterium, designated as N11-8 was further studied. Phylogenetic analysis based on 16S rRNA gene sequence showed that N11-8 belongs to the genus Bacillus. Fermented <span class="hlt">active</span> products of N11-8 with molecular weights of 1-30 kDa had higher inhibitory effects on different cancaer cells, such as BEL-7402 human hepatocellular carcinoma cells, U251 human glioma cells, RKO human colon carcinoma cells, A549 human lung carcinoma cells, and MCF-7 human breast carcinoma cells. However, they displayed lower cytotoxicity against HFL1 human normal fibroblast lung cells. However, they displayed lower cytotoxicity against HFL1 human normal fibroblast lung cells. Microscopic observations showed that the fermented <span class="hlt">active</span> products have inhibitory <span class="hlt">activity</span> on BEL-7402 cells similar to that of mitomycin C. Further studies indicated that the fermented <span class="hlt">active</span> products have high pH and high thermal stability. In conclusion, most strains isolated in this study may be developed as promising sources for the discovery of antitumor bioactive substances. The fermented <span class="hlt">active</span> products of <span class="hlt">Antarctic</span> marine Bacillus sp. N11- 8 are expected to be applied in the prevention and treatment of cancer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6507L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6507L"><span>The Microphysics of <span class="hlt">Antarctic</span> Clouds - Part one Observations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lachlan-Cope, Tom; Listowski, Constantino; O'Shea, Sebastian; Bower, Keith</p> <p>2016-04-01</p> <p>During the <span class="hlt">Antarctic</span> summer of 2010 and 2011 in-situ measurements of clouds were made over the <span class="hlt">Antarctic</span> Peninsula and in 2015 similar measurements were made over the eastern Weddell Sea using the British <span class="hlt">Antarctic</span> Surveys instrumented Twin Otter aircraft. This paper contrasts the clouds found on either side of the <span class="hlt">Antarctic</span> Peninsula with the clouds over the eastern Weddell Sea, paying particular attention to the total number of ice and water particles found in the clouds. The differences found between the clouds are considered in relation to the sources of cloud condensation nuclei and ice nuclei that are expected to be <span class="hlt">active</span> in the different cases. In particular it was found that the number of ice nuclei was very low over the Weddell Sea when compared to other regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACP....15.7537L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACP....15.7537L"><span>The role of blowing snow in the <span class="hlt">activation</span> of bromine over first-year <span class="hlt">Antarctic</span> sea ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lieb-Lappen, R. M.; Obbard, R. W.</p> <p>2015-07-01</p> <p>It is well known that during polar springtime halide sea salt ions, in particular Br-, are photochemically <span class="hlt">activated</span> into reactive halogen species (e.g., Br and BrO), where they break down tropospheric ozone. This research investigated the role of blowing snow in transporting salts from the sea ice/snow surface into reactive bromine species in the air. At two different locations over first-year ice in the Ross Sea, Antarctica, collection baskets captured blowing snow at different heights. In addition, sea ice cores and surface snow samples were collected throughout the month-long campaign. Over this time, sea ice and surface snow Br- / Cl- mass ratios remained constant and equivalent to seawater, and only in lofted snow did bromide become depleted relative to chloride. This suggests that replenishment of bromide in the snowpack occurs faster than bromine <span class="hlt">activation</span> in mid-strength wind conditions (approximately 10 m s-1) or that blowing snow represents only a small portion of the surface snowpack. Additionally, lofted snow was found to be depleted in sulfate and enriched in nitrate relative to surface snow.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACPD...1511985L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACPD...1511985L"><span>The role of blowing snow in the <span class="hlt">activation</span> of bromine over first-year <span class="hlt">Antarctic</span> sea ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lieb-Lappen, R. M.; Obbard, R. W.</p> <p>2015-04-01</p> <p>It is well known that during polar springtime halide sea salt ions, in particular Br-, are photochemically <span class="hlt">activated</span> into reactive halogen species (e.g. Br and BrO), where they break down tropospheric ozone. This research investigated the role of blowing snow in transporting salts from the sea ice/snow surface into reactive bromine species in the air. At two different locations over first-year ice in the Ross Sea, Antarctica, collection baskets captured blowing snow at different heights. In addition, sea ice cores and surface snow samples were collected throughout the month-long campaign. Over this time, sea ice and surface snow Cl-/Br- mass ratios remained constant and equivalent to seawater, and only in lofted snow did bromide become depleted relative to chloride. This suggests that replenishment of bromide in the snowpack occurs faster than bromine <span class="hlt">activation</span> in mid-strength wind conditions (approximately 10 m s-1). Additionally, lofted snow was found to be depleted in sulfate and enriched in nitrate relative to surface snow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1692993','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1692993"><span>Survival mechanisms in <span class="hlt">Antarctic</span> lakes.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Laybourn-Parry, Johanna</p> <p>2002-01-01</p> <p>In <span class="hlt">Antarctic</span> lakes, organisms are confronted by continuous low temperatures as well as a poor light climate and nutrient limitation. Such extreme environments support truncated food webs with no fish, few metazoans and a dominance of microbial plankton. The key to success lies in entering the short <span class="hlt">Antarctic</span> summer with <span class="hlt">actively</span> growing populations. In many cases, the most successful organisms continue to function throughout the year. The few crustacean zooplankton remain <span class="hlt">active</span> in the winter months, surviving on endogenous energy reserves and, in some cases, continuing development. Among the Protozoa, mixotrophy is an important nutritional strategy. In the extreme lakes of the McMurdo Dry Valleys, planktonic cryptophytes are forced to sustain a mixotrophic strategy and cannot survive by photosynthesis alone. The dependence on ingesting bacteria varies seasonally and with depth in the water column. In the Vestfold Hills, Pyramimonas, which dominates the plankton of some of the saline lakes, also resorts to mixotrophy, but does become entirely photosynthetic at mid-summer. Mixotrophic ciliates are also common and the entirely photosynthetic ciliate Mesodinium rubrum has a widespread distribution in the saline lakes of the Vestfold Hills, where it attains high concentrations. Bacteria continue to grow all year, showing cycles that appear to be related to the availability of dissolved organic carbon. In saline lakes, bacteria experience sub-zero temperatures for long periods of the year and have developed biochemical adaptations that include anti-freeze proteins, changes in the concentrations of polyunsaturated fatty acids in their membranes and suites of low-temperature enzymes. PMID:12171649</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6357B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6357B"><span>A new 10Be record recovered from an <span class="hlt">Antarctic</span> ice core: validity and limitations to record the solar <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baroni, Mélanie; Bard, Edouard; Aster Team</p> <p>2015-04-01</p> <p>Cosmogenic nuclides provide the only possibility to document solar <span class="hlt">activity</span> over millennia. Carbon-14 (14C) and beryllium-10 (10Be) records are retrieved from tree rings and ice cores, respectively. Recently, 14C records have also proven to be reliable to detect two large Solar Proton Events (SPE) (Miyake et al., Nature, 2012, Miyake et al., Nat. Commun., 2013) that occurred in 774-775 A.D. and in 993-994 A.D.. The origin of these events is still under debate but it opens new perspectives for the interpretation of 10Be ice core records. We present a new 10Be record from an ice core from Dome C (Antarctica) covering the last millennium. The chronology of this new ice core has been established by matching volcanic events on the WAIS Divide ice core (WDC06A) that is the best dated record in Antarctica over the Holocene (Sigl et al., JGR, 2013, Sigl et al., Nat. Clim. Change, 2014). The five minima of solar <span class="hlt">activity</span> (Oort, Wolf, Spörer, Maunder and Dalton) are detected and characterized by a 10Be concentration increase of ca. 20% above average in agreement with previous studies of ice cores drilled at South Pole and Dome Fuji in Antarctica (Bard et al., EPSL, 1997; Horiuchi et al., Quat. Geochrono., 2008) and at NGRIP and Dye3 in Greenland (Berggren et al., GRL, 2009). The high resolution, on the order of a year, allows the detection of the 11-year solar cycle. Sulfate concentration, a proxy for volcanic eruptions, has also been measured in the very same samples, allowing a precise comparison of both 10Be and sulfate profiles. We confirm the systematic relationship between stratospheric eruptions and 10Be concentration increases, first evidenced by observations of the stratospheric volcanic eruptions of Agung in 1963 and Pinatubo in 1991 (Baroni et al., GCA, 2011). This relationship is due to an increase in 10Be deposition linked to the role played by the sedimentation of volcanic aerosols. In the light of these new elements, we will discuss the limitations and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8088V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8088V"><span>Carbon-dioxide flow measurement in geodynamically <span class="hlt">active</span> area of <span class="hlt">West</span> Bohemia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vlcek, Josef; Fischer, Tomas; Heinicke, Jens</p> <p>2016-04-01</p> <p>Geodynamically <span class="hlt">active</span> area of <span class="hlt">West</span> Bohemia is interesting not only due to its earthquake swarms occurrence but also due to degassing flux of magmatic origin occurring in natural moffettes and mineral springs. While monitoring of earthquakes is done by a standard local seismic network, monitoring of amount of CO2 is at its initial stage. Despite lack of data, the 2014 earthquake swarm showed also very interesting increase in CO2 flow. This correlation with seismicity motivated us to develop robust and reliable methods of CO2 flow measurement, which would be sufficient to create denser monitoring network. Standard usage of gas-flowmeter for the purpose of gas flow measurement is dependent on the weather and device conditions, which makes the measurement instable in time and unreliable. Although gas-flowmeter is also accompanied with measurement of the gas pressure in the well to check flow rate value, reliability of this method is still low. This problematic behavior of the flow measurement was the reason to test new methods to measure CO2 amount - the first is based on measuring the density water with bubbles in the well by differential pressure gauge. The second one utilizes electric conductivity measurement to determine the density of bubbles in the water-gas mixture. Advantage of these methods is that their probes are directly in the well or moffette, where the concentration is measured. This approach is free of the influence of moving parts and assures the independence of measurements of environmental conditions. In this paper we show examples of obtained data series from selected sites and compare the trend of the curves, the mutual relations of the measured quantities and the influence of environmental conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019339','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019339"><span>International Workshop on <span class="hlt">Antarctic</span> Meteorites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Annexstad, J. O.; Schultz, L.; Waenke, H.</p> <p>1986-01-01</p> <p>Topics addressed include: meteorite concentration mechanisms; meteorites and the <span class="hlt">Antarctic</span> ice sheet; iron meteorites; iodine overabundance in meteorites; entrainment, transport, and concentration of meteorites in polar ice sheets; weathering of stony meteorites; cosmic ray records; radiocarbon dating; element distribution and noble gas isotopic abundances in lunar meteorites; thermoanalytical characterization; trace elements; thermoluminescence; parent sources; and meteorite ablation and fusion spherules in <span class="hlt">Antarctic</span> ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T13A2509V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T13A2509V"><span><span class="hlt">Antarctic</span> Crustal Thickness from Gravity Inversion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vaughan, A. P.; Kusznir, N. J.; Ferraccioli, F.; Jordan, T. A.</p> <p>2013-12-01</p> <p>Using gravity anomaly inversion, we have produced the first comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/β) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction. The continental lithosphere thinning distribution, used to define the initial thermal model temperature perturbation is derived from the gravity inversion and uses no a priori isochron information; as a consequence the gravity inversion method provides a prediction of ocean-continent transition location, which is independent of ocean isochron information. The gravity anomaly contribution from ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the most recent Bedmap2 ice thickness and bedrock topography compilation south of 60 degrees south (Fretwell et al., 2013) and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica penetrated by narrow continental rifts that feature relatively thinner crust. The East <span class="hlt">Antarctic</span> Rift System (EARS) is a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. Intermediate crustal thickness with an inferred linear rift fabric is predicted under Coates Land. An extensive region of either thick oceanic crust or highly thinned continental crust is predicted offshore Oates Land and north Victoria Land, and also off <span class="hlt">West</span> Antarctica</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014E%26PSL.403..166R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014E%26PSL.403..166R"><span>First evidence of widespread <span class="hlt">active</span> methane seepage in the Southern Ocean, off the sub-<span class="hlt">Antarctic</span> island of South Georgia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Römer, M.; Torres, M.; Kasten, S.; Kuhn, G.; Graham, A. G. C.; Mau, S.; Little, C. T. S.; Linse, K.; Pape, T.; Geprägs, P.; Fischer, D.; Wintersteller, P.; Marcon, Y.; Rethemeyer, J.; Bohrmann, G.</p> <p>2014-10-01</p> <p>An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an <span class="hlt">active</span> area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25908601','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25908601"><span>Exposure age and ice-sheet model constraints on Pliocene East <span class="hlt">Antarctic</span> ice sheet dynamics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki</p> <p>2015-04-24</p> <p>The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East <span class="hlt">Antarctic</span> Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from <span class="hlt">West</span> Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea ice cover and inhibited <span class="hlt">active</span> moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4421805','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4421805"><span>Exposure age and ice-sheet model constraints on Pliocene East <span class="hlt">Antarctic</span> ice sheet dynamics</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki</p> <p>2015-01-01</p> <p>The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East <span class="hlt">Antarctic</span> Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from <span class="hlt">West</span> Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea ice cover and inhibited <span class="hlt">active</span> moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas. PMID:25908601</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.458...49C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.458...49C"><span>Widespread <span class="hlt">Antarctic</span> glaciation during the Late Eocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carter, Andrew; Riley, Teal R.; Hillenbrand, Claus-Dieter; Rittner, Martin</p> <p>2017-01-01</p> <p>Marine sedimentary rocks drilled on the southeastern margin of the South Orkney microcontinent in Antarctica (Ocean Drilling Program Leg 113 Site 696) were deposited between ∼36.5 Ma to 33.6 Ma, across the Eocene-Oligocene climate transition. The recovered rocks contain abundant grains exhibiting mechanical features diagnostic of iceberg-rafted debris. Sand provenance based on a multi-proxy approach that included petrographic analysis of over 275,000 grains, detrital zircon geochronology and apatite thermochronometry rule out local sources (<span class="hlt">Antarctic</span> Peninsula or the South Orkney Islands) for the material. Instead the ice-transported grains show a clear provenance from the southern Weddell Sea region, extending from the Ellsworth-Whitmore Mountains of <span class="hlt">West</span> Antarctica to the coastal region of Dronning Maud Land in East Antarctica. This study provides the first evidence for a continuity of widespread glacier calving along the coastline of the southern Weddell Sea embayment at least 2.5 million yrs before the prominent oxygen isotope event at 34-33.5 Ma that is considered to mark the onset of widespread glaciation of the <span class="hlt">Antarctic</span> continent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/549160','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/549160"><span>Sudden sea-level change from melting <span class="hlt">Antarctic</span> ice: How likely?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bentley, C.R.</p> <p>1995-12-31</p> <p>There has been concern that the <span class="hlt">West</span> <span class="hlt">Antarctic</span> marine ice sheet could collapse catastrophically, leading to a 5-meter rise in sea level in a single century. However, that idea was based on a modeled instability at the grounding line that reflected a discontinuity between the mathematical models used for the grounded and floating parts of the ice sheet, respectively. Improved knowledge about ice streams, the <span class="hlt">active</span> portions of the marine ice sheet, reveals that in the Ross Sea sector, at least, there is in reality a broad, gradual transition zone, rather than a discontinuity, between the inland ice and the ice shelf. Consequently, there probably is no instability; total disappearance of the ice sheet would take a millenium or more. The resulting average contribution to sea-level rise thus would be only a few millimeters per year, comparable to the present rate of rise (from all sources). Furthermore, dynamic response to present-day climate change would not even begin in less than a century. It is still uncertain whether the <span class="hlt">Antarctic</span> ice sheet is making a positive or negative contribution to sea-level rise now. Whichever the case, however, during the next century or two the effect of climatic warming almost surely will be to increase the mass input to the ice sheet, thus yielding a negative contribution to sea-level rise of the order of a millimeter per year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26667909','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26667909"><span>Advances in modelling subglacial lakes and their interaction with the <span class="hlt">Antarctic</span> ice sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pattyn, Frank; Carter, Sasha P; Thoma, Malte</p> <p>2016-01-28</p> <p>Subglacial lakes have long been considered hydraulically isolated water bodies underneath ice sheets. This view changed radically with the advent of repeat-pass satellite altimetry and the discovery of multiple lake discharges and water infill, associated with water transfer over distances of more than 200 km. The presence of subglacial lakes also influences ice dynamics, leading to glacier acceleration. Furthermore, subglacial melting under the <span class="hlt">Antarctic</span> ice sheet is more widespread than previously thought, and subglacial melt rates may explain the availability for water storage in subglacial lakes and water transport. Modelling of subglacial water discharge in subglacial lakes essentially follows hydraulics of subglacial channels on a hard bed, where ice sheet surface slope is a major control on triggering subglacial lake discharge. Recent evidence also points to the development of channels in deformable sediment in <span class="hlt">West</span> Antarctica, with significant water exchanges between till and ice. Most <span class="hlt">active</span> lakes drain over short time scales and respond rapidly to upstream variations. Several <span class="hlt">Antarctic</span> subglacial lakes exhibit complex interactions with the ice sheet due to water circulation. Subglacial lakes can therefore-from a modelling point of view-be seen as confined small oceans underneath an imbedded ice shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006DSRII..53..985L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006DSRII..53..985L"><span>Biodiversity and biogeography of <span class="hlt">Antarctic</span> and sub-<span class="hlt">Antarctic</span> mollusca</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Linse, Katrin; Griffiths, Huw J.; Barnes, David K. A.; Clarke, Andrew</p> <p>2006-04-01</p> <p>For many decades molluscan data have been critical to the establishment of the concept of a global-scale increase in species richness from the poles to the equator. Low polar diversity is key to this latitudinal cline in diversity. Here we investigate richness patterns in the two largest classes of molluscs at both local and regional scales throughout the Southern Ocean. We show that biodiversity is very patchy in the Southern Ocean (at the 1000-km scale) and test the validity of historical biogeographic sub-regions and provinces. We used multivariate analysis of biodiversity patterns at species, genus and family levels to define richness hotspots within the Southern Ocean and transition areas. This process identified the following distinct sub-regions in the Southern Ocean: <span class="hlt">Antarctic</span> Peninsula, Weddell Sea, East Antarctic—Dronning Maud Land, East Antarctic—Enderby Land, East Antarctic—Wilkes Land, Ross Sea, and the independent Scotia arc and sub <span class="hlt">Antarctic</span> islands. Patterns of endemism were very different between the bivalves and gastropods. On the basis of distributional ranges and radiation centres of evolutionarily successful families and genera we define three biogeographic provinces in the Southern Ocean: (1) the continental high <span class="hlt">Antarctic</span> province excluding the <span class="hlt">Antarctic</span> Peninsula, (2) the Scotia Sea province including the <span class="hlt">Antarctic</span> Peninsula, and (3) the sub <span class="hlt">Antarctic</span> province comprising the islands in the vicinity of the <span class="hlt">Antarctic</span> Circumpolar Current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.9913J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.9913J"><span>Trends of perchlorate in <span class="hlt">Antarctic</span> snow: Implications for atmospheric production and preservation in snow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Su; Cox, Thomas S.; Cole-Dai, Jihong; Peterson, Kari M.; Shi, Guitao</p> <p>2016-09-01</p> <p>Perchlorate concentration ranges from a few to a few hundred ng kg-1 in surface and shallow-depth snow at three <span class="hlt">Antarctic</span> locations (South Pole, Dome A, and central <span class="hlt">West</span> Antarctica), with significant spatial variations dependent on snow accumulation rate and/or atmospheric production rate. An obvious trend of increasing perchlorate since the 1970s is seen in South Pole snow. The trend is possibly the result of stratospheric chlorine levels elevated by anthropogenic chlorine emissions; this is supported by the timing of a similar trend at Dome A. Alternatively, the trend may stem from postdepositional loss of snowpack perchlorate or a combination of both. The possible impact of stratospheric chlorine is consistent with evidence of perchlorate production in the stratosphere. Additionally, perchlorate concentration appears to be directly affected by the springtime <span class="hlt">Antarctic</span> ozone hole. Therefore, perchlorate variations in <span class="hlt">Antarctic</span> snow are likely linked to stratospheric chemistry and ozone over the <span class="hlt">Antarctic</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920045032&hterms=west+antarctic+ice+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwest%2Bantarctic%2Bice%2Bshelf','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920045032&hterms=west+antarctic+ice+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwest%2Bantarctic%2Bice%2Bshelf"><span>AVHRR imagery reveals <span class="hlt">Antarctic</span> ice dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bindschadler, Robert A.; Vornberger, Patricia L.</p> <p>1990-01-01</p> <p>A portion of AVHRR data taken on December 5, 1987 at 06:15 GMT over a part of Antarctica is used here to show that many of the most significant dynamic features of ice sheets can be identified by a careful examination of AVHRR imagery. The relatively low resolution of this instrument makes it ideal for obtaining a broad view of the ice sheets, while its wide swath allows coverage of areas beyond the reach of high-resolution imagers either currently in orbit or planned. An interpretation is given of the present data, which cover the area of ice streams that drain the interior of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet into the Ross Ice Shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5516467','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5516467"><span>AVHRR imagery reveals <span class="hlt">Antarctic</span> ice dynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bindschadler, R.A.; Vornberger, P.L. STX Corp., Lanham, MD )</p> <p>1990-06-01</p> <p>A portion of AVHRR data taken on December 5, 1987 at 06:15 GMT over a part of Antarctica is used here to show that many of the most significant dynamic features of ice sheets can be identified by a careful examination of AVHRR imagery. The relatively low resolution of this instrument makes it ideal for obtaining a broad view of the ice sheets, while its wide swath allows coverage of areas beyond the reach of high-resolution imagers either currently in orbit or planned. An interpretation is given of the present data, which cover the area of ice streams that drain the interior of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet into the Ross Ice Shelf. 21 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SolE....5..705A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SolE....5..705A"><span>Microbial biomass and basal respiration of selected Sub-<span class="hlt">Antarctic</span> and <span class="hlt">Antarctic</span> soils in the areas of some Russian polar stations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abakumov, E.; Mukhametova, N.</p> <p>2014-07-01</p> <p>Antarctica is a unique place for soil, biological, and ecological investigations. Soils of Antarctica have been studied intensively during the last century, when different national <span class="hlt">Antarctic</span> expeditions visited the sixth continent with the aim of investigating nature and the environment. <span class="hlt">Antarctic</span> investigations are comprised of field surveys mainly in the terrestrial landscapes, where the polar stations of different countries are situated. That is why the main and most detailed soil surveys were conducted in the McMurdo Valleys, Transantarctic Mountains, South Shetland Islands, Larsemann Hills and the Schirmacher Oasis. Our investigations were conducted during the 53rd and 55th Russian <span class="hlt">Antarctic</span> expeditions in the base of soil pits, and samples were collected in Sub-<span class="hlt">Antarctic</span> and <span class="hlt">Antarctic</span> regions. Sub-<span class="hlt">Antarctic</span> or maritime landscapes are considered to be very different from <span class="hlt">Antarctic</span> landscapes due to differing climatic and geogenic conditions. Soils of diverse zonal landscapes were studied with the aim of assessing the microbial biomass level, basal respiration rates and metabolic <span class="hlt">activity</span> of microbial communities. This investigation shows that <span class="hlt">Antarctic</span> soils are quite diverse in profile organization and carbon content. In general, Sub-<span class="hlt">Antarctic</span> soils are characterized by more developed humus (sod) organo-mineral horizons as well as by an upper organic layer. The most developed organic layers were revealed in peat soils of King George Island, where its thickness reach, in some cases, was 80 cm. These soils as well as soils formed under guano are characterized by the highest amount of total organic carbon (TOC), between 7.22 and 33.70%. Coastal and continental <span class="hlt">Antarctic</span> soils exhibit less developed Leptosols, Gleysols, Regolith and rare Ornhitosol, with TOC levels between 0.37 and 4.67%. The metabolic ratios and basal respiration were higher in Sub-<span class="hlt">Antarctic</span> soils than in <span class="hlt">Antarctic</span> ones, which can be interpreted as a result of higher amounts of fresh organic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=calculus&id=EJ1116175','ERIC'); return false;" href="http://eric.ed.gov/?q=calculus&id=EJ1116175"><span>An <span class="hlt">Active</span> Classroom: The Emerging Scholars Program at <span class="hlt">West</span> Virginia University</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Deshler, Jessica M.; Miller, David; Pascal, Matthew</p> <p>2016-01-01</p> <p>In an effort to support the success of minority students and to incorporate inquiry-based learning (IBL) into the calculus sequence of courses at <span class="hlt">West</span> Virginia University, a modified version of the Emerging Scholars Program (ESP) was implemented in the fall of 2009. Since then, approximately 100 students have taken ESP Calculus I, with many of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15318160','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15318160"><span><span class="hlt">West</span> Nile virus <span class="hlt">activity</span>--United States, August 11-17, 2004.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2004-08-20</p> <p>During August 11-17, a total of 194 cases of human <span class="hlt">West</span> Nile virus (WNV) illness were reported from 17 states (Alabama, Arizona, California, Colorado, Florida, Illinois, Louisiana, Maryland, Minnesota, Mississippi, Missouri, New Mexico, Ohio, South Dakota, Texas, Utah, and Virginia).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15483530','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15483530"><span><span class="hlt">West</span> Nile virus <span class="hlt">activity</span>--United States, October 6-12, 2004.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2004-10-15</p> <p>During October 6-12, a total of 86 cases of human <span class="hlt">West</span> Nile virus (WNV) illness were reported from 18 states (Arizona, Florida, Illinois, Kansas, Louisiana, Michigan, Minnesota, Missouri, Nevada, New Jersey, New Mexico, North Dakota, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas, and Utah).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15457147','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15457147"><span><span class="hlt">West</span> Nile virus <span class="hlt">activity</span>--United States, September 22-28, 2004.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2004-10-01</p> <p>During September 22-28, a total of 180 cases of human <span class="hlt">West</span> Nile virus (WNV) illness were reported in the District of Columbia (DC) and 24 states (Alabama, Arizona, California, Georgia, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, Ohio, Pennsylvania, Texas, Utah, Wisconsin, and Wyoming).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15385920','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15385920"><span><span class="hlt">West</span> Nile virus <span class="hlt">activity</span>--United States, September 15-21, 2004.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2004-09-24</p> <p>During September 15-21, a total of 218 cases of human <span class="hlt">West</span> Nile virus (WNV) illness were reported from 21 states (Arizona, California, Florida, Illinois, Indiana, Kansas, Maryland, Michigan, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah, Wisconsin, and Wyoming).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15514584','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15514584"><span><span class="hlt">West</span> Nile virus <span class="hlt">activity</span>--United States, October 20-26, 2004.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2004-10-29</p> <p>During October 20-26, a total of 80 cases of human <span class="hlt">West</span> Nile virus (WNV) illness were reported from 16 states (Arizona, California, Florida, Iowa, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Montana, Nebraska, New York, Ohio, South Dakota, Texas, and Utah).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2007/1047/srp/srp101/of2007-1047srp101.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2007/1047/srp/srp101/of2007-1047srp101.pdf"><span>Thermochronologic constraints on the tectonic evolution of the western <span class="hlt">Antarctic</span> Peninsula in late Mesozoic and Cenozoic times</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brix, M.R.; Faundez, V.; Hervé, F.; Solari, M.; Fernandez, J.; Carter, A.; Stöckhert, B.</p> <p>2007-01-01</p> <p><span class="hlt">West</span> of the <span class="hlt">Antarctic</span> Peninsula, oceanic lithosphere of the Phoenix plate has been subducted below the <span class="hlt">Antarctic</span> plate. Subduction has ceased successively from south to north over the last 65 Myr. An influence of this evolution on the segmentation of the crust in the <span class="hlt">Antarctic</span> plate is disputed. Opposing scenarios consider effects of ridge crest – trench interactions with the subduction zone or differences in slip along a basal detachment in the overriding plate. Fission track (FT) analyses on apatites and zircons may detect thermochronologic patterns to test these hypotheses. While existing data concentrate on accretionary processes in Palmer Land, new data extend information to the northern part of the <span class="hlt">Antarctic</span> Peninsula. Zircons from different geological units over wide areas of the <span class="hlt">Antarctic</span> Peninsula yield fission track ages between 90 and 80 Ma, indicating a uniform regional cooling episode. Apatite FT ages obtained so far show considerable regional variability</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013495','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013495"><span>Mass Gains of the <span class="hlt">Antarctic</span> Ice Sheet Exceed Losses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David</p> <p>2012-01-01</p> <p>During 2003 to 2008, the mass gain of the <span class="hlt">Antarctic</span> ice sheet from snow accumulation exceeded the mass loss from ice discharge by 49 Gt/yr (2.5% of input), as derived from ICESat laser measurements of elevation change. The net gain (86 Gt/yr) over the <span class="hlt">West</span> <span class="hlt">Antarctic</span> (WA) and East <span class="hlt">Antarctic</span> ice sheets (WA and EA) is essentially unchanged from revised results for 1992 to 2001 from ERS radar altimetry. Imbalances in individual drainage systems (DS) are large (-68% to +103% of input), as are temporal changes (-39% to +44%). The recent 90 Gt/yr loss from three DS (Pine Island, Thwaites-Smith, and Marie-Bryd Coast) of WA exceeds the earlier 61 Gt/yr loss, consistent with reports of accelerating ice flow and dynamic thinning. Similarly, the recent 24 Gt/yr loss from three DS in the <span class="hlt">Antarctic</span> Peninsula (AP) is consistent with glacier accelerations following breakup of the Larsen B and other ice shelves. In contrast, net increases in the five other DS of WA and AP and three of the 16 DS in East Antarctica (EA) exceed the increased losses. Alternate interpretations of the mass changes driven by accumulation variations are given using results from atmospheric-model re-analysis and a parameterization based on 5% change in accumulation per degree of observed surface temperature change. A slow increase in snowfall with climate waRMing, consistent with model predictions, may be offsetting increased dynamic losses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5782301','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5782301"><span>Plate tectonic evolution of circum-<span class="hlt">Antarctic</span> passive margins</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Scotese, C.R.; Lawver, L.A.; Sclater, J.G.; Mayes, C.L.; Norton, I.; Royer, J.</p> <p>1987-05-01</p> <p>Passive margins that formed during the Late Jurassic and Cretaceous account for approximately 80% of the 15,000-km circumference of Antarctica. There are no passive margins younger than Late Cretaceous. Approximately 28% of these margins are Late Jurassic in age, 24% are Early Cretaceous in age, and the remaining 48% formed during the Late Cretaceous. The tectonic style of the rifting events that formed these margins varies considerably along the perimeter of Antarctica. In several areas the initiation of sea-floor spreading was preceded by a long period of extension and predrift stretching (Wilkes Land). Along other portions of the margin, rifting proceeded rapidly with little evidence for a lengthy phase of pre-drift extension (Queen Maud Land). Though extension is the dominant tectonic style, there is evidence for large-scale strike-slip movement associated with the early phases of continental breakup along the coasts of Crown Princess Martha Land and Victoria Land. Except for a short segment of the margin between the <span class="hlt">West</span> <span class="hlt">Antarctic</span> peninsula and Marie Byrdland, the <span class="hlt">Antarctic</span> passive margins have not been affected by subsequent subduction-related compressive deformation. This presentation will review the plate tectonic evolution of the Circum-<span class="hlt">Antarctic</span> passive margins during five time intervals: Early Jurassic, Late Jurassic, Early Cretaceous, mid-Cretaceous, and latest Cretaceous. A map illustrating the relative amounts of extension along the margin of Antarctica will be presented, and a computer animation illustrating the breakup of Gondwana from an <span class="hlt">Antarctic</span> perspective will be shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4588704','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4588704"><span>Emerging spatial patterns in <span class="hlt">Antarctic</span> prokaryotes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chong, Chun-Wie; Pearce, David A.; Convey, Peter</p> <p>2015-01-01</p> <p>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 <span class="hlt">activity</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> prokaryote diversity patterns, drawing analogy with those of eukaryote groups where appropriate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26601273','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26601273"><span>Combustion of available fossil fuel resources sufficient to eliminate the <span class="hlt">Antarctic</span> Ice Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Winkelmann, Ricarda; Levermann, Anders; Ridgwell, Andy; Caldeira, Ken</p> <p>2015-09-01</p> <p>The <span class="hlt">Antarctic</span> Ice Sheet stores water equivalent to 58 m in global sea-level rise. We show in simulations using the Parallel Ice Sheet Model that burning the currently attainable fossil fuel resources is sufficient to eliminate the ice sheet. With cumulative fossil fuel emissions of 10,000 gigatonnes of carbon (GtC), Antarctica is projected to become almost ice-free with an average contribution to sea-level rise exceeding 3 m per century during the first millennium. Consistent with recent observations and simulations, the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet becomes unstable with 600 to 800 GtC of additional carbon emissions. Beyond this additional carbon release, the destabilization of ice basins in both <span class="hlt">West</span> and East Antarctica results in a threshold increase in global sea level. Unabated carbon emissions thus threaten the <span class="hlt">Antarctic</span> Ice Sheet in its entirety with associated sea-level rise that far exceeds that of all other possible sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4494391','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4494391"><span>GeoBioScience: Red Wood Ants as Bioindicators for <span class="hlt">Active</span> Tectonic Fault Systems in the <span class="hlt">West</span> Eifel (Germany)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Berberich, Gabriele; Schreiber, Ulrich</p> <p>2013-01-01</p> <p>Simple Summary In a 1.140 km² study area of the volcanic <span class="hlt">West</span> Eifel, approx. 3,000 Red Wood Ant (RWA; Formica rufa-group) mounds had been identified and correlated with tectonically <span class="hlt">active</span> gas-permeable faults, mostly strike-slip faults. Linear alignment of RWA mounds and soil gas anomalies distinctly indicate the course of these faults, while clusters of mounds indicate crosscut zones of fault systems, which can be correlated with voids caused by crustal block rotation. This demonstrates that RWA are bioindicators for identifying <span class="hlt">active</span> fault systems and useful where information on the <span class="hlt">active</span> regime is incomplete or the resolution by technical means is insufficient. Abstract In a 1.140 km² study area of the volcanic <span class="hlt">West</span> Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and <span class="hlt">active</span> tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO2, Helium, Radon and H2S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H2S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and <span class="hlt">active</span> tectonics in the <span class="hlt">West</span> Eifel</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16782602','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16782602"><span>Geological and geomorphological insights into <span class="hlt">Antarctic</span> ice sheet evolution.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sugden, David E; Bentley, Michael J; O Cofaigh, Colm</p> <p>2006-07-15</p> <p>Technical advances in the study of ice-free parts of Antarctica can provide quantitative records that are useful for constraining and refining models of ice sheet evolution and behaviour. Such records improve our understanding of system trajectory, influence the questions we ask about system stability and help to define the ice-sheet processes that are relevant on different time-scales. Here, we illustrate the contribution of cosmogenic isotope analysis of exposed bedrock surfaces and marine geophysical surveying to the understanding of <span class="hlt">Antarctic</span> ice sheet evolution on a range of time-scales. In the Dry Valleys of East Antarctica, 3He dating of subglacial flood deposits that are now exposed on mountain summits provide evidence of an expanded and thicker Mid-Miocene ice sheet. The survival of surface boulders for approximately 14Myr, the oldest yet measured, demonstrates exceptionally low rates of subsequent erosion and points to the persistence and stability of the dry polar desert climate since that time. Increasingly, there are constraints on <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet fluctuations during Quaternary glacial cycles. In the Sarnoff Mountains of Marie Byrd Land in <span class="hlt">West</span> Antarctica, 10Be and 26Al cosmogenic isotope analysis of glacial erratics and bedrock reveal steady thinning of the ice sheet from 10400 years ago to the present, probably as a result of grounding line retreat. In the <span class="hlt">Antarctic</span> Peninsula, offshore analysis reveals an extensive ice sheet at the last glacial maximum. Based on radiocarbon dating, deglaciation began by 17000cal yr BP and was complete by 9500cal yr BP. Deglaciation of the <span class="hlt">west</span> and east sides of the <span class="hlt">Antarctic</span> Peninsula ice sheet occurred at different times and rates, but was largely complete by the Early Holocene. At that time ice shelves were less extensive on the <span class="hlt">west</span> side of the <span class="hlt">Antarctic</span> Peninsula than they are today. The message from the past is that individual glacier drainage basins in Antarctica respond in different and distinctive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020039046','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020039046"><span>RADARSAT: The <span class="hlt">Antarctic</span> Mapping Project</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jezek, Kenneth C.; Lindstrom, E. (Technical Monitor)</p> <p>2002-01-01</p> <p>The first <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span>, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26081896','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26081896"><span>Metazoan Parasites of <span class="hlt">Antarctic</span> Fishes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oğuz, Mehmet Cemal; Tepe, Yahya; Belk, Mark C; Heckmann, Richard A; Aslan, Burçak; Gürgen, Meryem; Bray, Rodney A; Akgül, Ülker</p> <p>2015-06-01</p> <p>To date, there have been nearly 100 papers published on metazoan parasites of <span class="hlt">Antarctic</span> fishes, but there has not yet been any compilation of a species list of fish parasites for this large geographic area. Herein, we provide a list of all documented occurrences of monogenean, cestode, digenean, acanthocephalan, nematode, and hirudinean parasites of <span class="hlt">Antarctic</span> fishes. The list includes nearly 250 parasite species found in 142 species of host fishes. It is likely that there are more species of fish parasites, which are yet to be documented from <span class="hlt">Antarctic</span> waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16915222','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16915222"><span><span class="hlt">West</span> Nile virus <span class="hlt">activity</span>--United States, January 1-August 15, 2006.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2006-08-18</p> <p>This report summarizes <span class="hlt">West</span> Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, August 15, 2006. A total of 26 states had reported 388 cases of human WNV illness to CDC. A total of 214 (56%) cases for which such data were available occurred in males; median age of patients was 49 years (range: 2-91 years). Dates of illness onset ranged from January 6 to August 10; a total of 13 cases were fatal. A total of 68 presumptive <span class="hlt">West</span> Nile viremic blood donors (PVDs) have been reported to ArboNET during 2006. Of these, 20 were reported from Nebraska; 18 were reported from Texas; five were reported from California; four were reported from Utah; three each were reported from Oklahoma and South Dakota; two each were reported from Idaho, Iowa, Kentucky, and Mississippi; and one each was reported from Arizona, Colorado, Minnesota, Nevada, North Dakota, Wisconsin, and Wyoming. Of the 68 PVDs, 10 persons (median age: 43 years [range: 18-59 years]) subsequently had <span class="hlt">West</span> Nile fever.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900031872&hterms=largest+crystals&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dlargest%2Bcrystals','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900031872&hterms=largest+crystals&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dlargest%2Bcrystals"><span><span class="hlt">Antarctic</span> stratospheric ice crystals</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goodman, J.; Toon, O. B.; Pueschel, R. F.; Snetsinger, K. G.; Verma, S.</p> <p>1989-01-01</p> <p>Ice crystals were replicated over the Palmer Peninsula at approximately 72 deg S on six occasions during the 1987 Airboirne <span class="hlt">Antarctic</span> Ozone Experiment. The sampling altitude was between 12.5 and 18.5 km (45-65 thousand ft pressure altitude) with the temperature between 190 and 201 K. The atmosphere was subsaturated with respect to ice in all cases. The collected crystals were predominantly solid and hollow columns. The largest crystals were sampled at lower altitudes where the potential temperature was below 400 K. While the crystals were larger than anticipated, their low concentration results in a total surface area that is less than one tenth of the total aerosol surface area. The large ice crystals may play an important role in the observed stratospheric dehydration processes through sedimentation. Evidence of scavenging of submicron particles further suggests that the ice crystals may be effective in the removal of stratospheric chemicals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP32B..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP32B..03S"><span>Climate in <span class="hlt">West</span> Antarctica over the last century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steig, E. J.; White, J. W.; Ding, Q.</p> <p>2011-12-01</p> <p>There have been significant changes in atmospheric circulation over <span class="hlt">West</span> Antarctica in the last few decades. These changes have been linked to ozone depletion in the stratosphere, greenhouse gases in the troposphere, and rising temperatures in the equatorial Pacific. The circulation changes have resulted in sea ice declines and increased temperatures on the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet, and may also explain recent oceanographic changes linked to ice shelf thinning (Steig et al, 2011). It remains an open question whether these are exceptional changes to <span class="hlt">Antarctic</span> climate, or fall within the range of unforced variability. Instrumental climate records are too short and too sparse in the <span class="hlt">Antarctic</span> to address this question. Ice core records obtained from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS) and <span class="hlt">Antarctic</span> Peninsula provide an opportunity to extend the observational record of <span class="hlt">West</span> <span class="hlt">Antarctic</span> climate into the past. We present δ18O records from the WAIS Divide site in central <span class="hlt">West</span> Antarctica, along with both new and previously published data from shallow records from the U.S. "ITASE" program in <span class="hlt">West</span> Antarctica (Steig et al., 2005; Schneider et al., 2006) and British <span class="hlt">Antarctic</span> Survey records from the Peninsula (Thomas et al., 2009). The <span class="hlt">West</span> <span class="hlt">Antarctic</span> δ18O records are highly correlated with temperature -- explaining about 80% of the decadal variance -- and capture unequivocally the warming trend of the last few decades across most of <span class="hlt">West</span> Antarctica. Centennial variations are also captured, with the same scaling (about 0.8%/°C) (Fegyveresi et al., 2011). The covariance of δ18O and temperature occurs because both are increased under conditions of anomalously strong meridional flow. The δ18O signal is further amplified by the presence of open water near the <span class="hlt">Antarctic</span> coastline, due to reduced sea ice divergence from the same northerly flow. Extremes in δ18O are frequently associated with strong El Niño events. The response is particularly strong when warming occurs in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26394097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26394097"><span><span class="hlt">Antarctic</span> sea ice losses drive gains in benthic carbon drawdown.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barnes, D K A</p> <p>2015-09-21</p> <p>Climate forcing of sea-ice losses from the Arctic and <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">West</span> <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AtmEn.122..393Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AtmEn.122..393Z"><span>The <span class="hlt">Antarctic</span> ozone depletion caused by Erebus volcano gas emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zuev, V. V.; Zueva, N. E.; Savelieva, E. S.; Gerasimov, V. V.</p> <p>2015-12-01</p> <p>Heterogeneous chemical reactions releasing photochemically <span class="hlt">active</span> molecular chlorine play a key role in <span class="hlt">Antarctic</span> stratospheric ozone destruction, resulting in the <span class="hlt">Antarctic</span> ozone hole. Hydrogen chloride (HCl) is one of the principal components in these reactions on the surfaces of polar stratospheric clouds (PSCs). PSCs form during polar nights at extremely low temperatures (lower than -78 °C) mainly on sulfuric acid (H2SO4) aerosols, acting as condensation nuclei and formed from sulfur dioxide (SO2). However, the cause of HCl and H2SO4 high concentrations in the <span class="hlt">Antarctic</span> stratosphere, leading to considerable springtime ozone depletion, is still not clear. Based on the NCEP/NCAR reanalysis data over the last 35 years and by using the NOAA HYSPLIT trajectory model, we show that Erebus volcano gas emissions (including HCl and SO2) can reach the <span class="hlt">Antarctic</span> stratosphere via high-latitude cyclones with the annual average probability Pbarann. of at least ∼0.235 (23.5%). Depending on Erebus <span class="hlt">activity</span>, this corresponds to additional annual stratospheric HCl mass of 1.0-14.3 kilotons (kt) and SO2 mass of 1.4-19.7 kt. Thus, Erebus volcano is the natural and powerful source of additional stratospheric HCl and SO2, and hence, the cause of the <span class="hlt">Antarctic</span> ozone depletion, together with man-made chlorofluorocarbons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.C51A0935S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.C51A0935S"><span>The <span class="hlt">Antarctic</span> Master Directory -- a resource for <span class="hlt">Antarctic</span> Scientists</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scharfen, G.; Bauer, R.</p> <p>2002-12-01</p> <p>Under the auspices of the <span class="hlt">Antarctic</span> Treaty, a group of nations conducting <span class="hlt">Antarctic</span> scientific research have created the <span class="hlt">Antarctic</span> Master Directory (AMD), a resource for <span class="hlt">Antarctic</span> scientists. The AMD is a Web-based, searchable directory containing data descriptions (metadata in the form of DIF entries) of <span class="hlt">Antarctic</span> scientific data, and is a node of the International Directory Network/Global Change Master Directory (IDN/GCMD). The data descriptions in the AMD, essentially a data catalog of <span class="hlt">Antarctic</span> scientific data, include information about what data were collected, where they were collected, when they were collected, who the scientists are, who the point of contact is, and information about the format of the data and what documentation and bibliographic information exists. As part of the AMD effort, the National Science Foundation Office of Polar Programs (OPP) funds the National Snow and Ice Data Center to operate the U.S. <span class="hlt">Antarctic</span> Data Coordination Center (USADCC), the US focal point for the AMD. The USADCC assists PIs as they meet the requirements of the OPP "Guidelines and Award Conditions for Scientific Data", which identify the conditions for awards and responsibilities of PIs regarding the archival of data, and submission of metadata, resulting from their NSF OPP grants. The USADCC offers access to free, easy-to-use online tools that PIs can use to create the data descriptions that the NSF policy data requires. We provide advice to PIs on how to meet the data policy requirements, and can answer specific questions on related issues. Scientists can access data set descriptions submitted to the AMD, by thousands of scientists around the world, from the USADCC web pages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A51V..06O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A51V..06O"><span>Insights on <span class="hlt">Antarctic</span> climate variability from paleo-temperature proxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orsi, A. J.; Landais, A.; Stenni, B.; Severinghaus, J. P.</p> <p>2015-12-01</p> <p>Few direct meteorological observations exist in Antarctica, which limits our understanding of the modes of climate variability in this region. In particular, atmospheric reanalyses do not produce a coherent picture of the known warming trend since 1979. Here we analyze a suite of paleo-temperature proxies to gain insight into both the recent temperature trend and the multi-decadal climate variability in Antarctica over the last 1000 years. We present temperature records from two sites in Antarctica: WAIS Divide (79°S, 112°W, 1766 m a.s.l), and Talos Dome (72°S, 159°E, 2315 m a.s.l), reconstructed from the combination of inert gas isotopes from the ice core and borehole temperature measurements. Borehole temperature provides an absolute estimate of long-term trends, while noble gases track decadal to centennial scale changes. In addition, we use water isotopes to infer information about circulation changes. We find a strong warming trend in <span class="hlt">West</span> Antarctica over the last 50 years (+0.23°C/decade), which is accelerating (+0.8°C/decade since 1980). The longer temperature record shows that such a trend has analogs happening about every 200 years. However, the study of other climate proxies suggests that the recent trend is due to a different mechanism than the previous events. We also find a long term cooling trend over the last 1000 years, which is stronger in East Antarctica (Talos Dome) than in <span class="hlt">West</span> Antarctica (WAIS-Divide). At WAIS Divide, we find that "Little Ice Age" cold period of 1400-1800 was 0.52°C colder than the last century. Overall, both records are consistent with the idea that the solar minima and persistent volcanic <span class="hlt">activity</span> of the Little Ice Age (1400-1850 A.D.) had a significant impact on the surface temperature in Antarctica. The feedbacks amplifying the forcing were likely stronger on the East <span class="hlt">Antarctic</span> plateau than on the more marine-influenced <span class="hlt">West</span> Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9876197','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9876197"><span>Health aspects of <span class="hlt">Antarctic</span> tourism.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prociv, P</p> <p>1998-12-01</p> <p>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 <span class="hlt">Antarctic</span> 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 <span class="hlt">activities</span> along the northern coast of Siberia (and from <span class="hlt">Antarctic</span> 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</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26487413','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26487413"><span>GeoBioScience: Red Wood Ants as Bioindicators for <span class="hlt">Active</span> Tectonic Fault Systems in the <span class="hlt">West</span> Eifel (Germany).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berberich, Gabriele; Schreiber, Ulrich</p> <p>2013-05-17</p> <p>In a 1.140 km² study area of the volcanic <span class="hlt">West</span> Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and <span class="hlt">active</span> tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and <span class="hlt">active</span> tectonics in the <span class="hlt">West</span> Eifel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15938749','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15938749"><span>Prospects for surviving climate change in <span class="hlt">Antarctic</span> aquatic species.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Peck, Lloyd S</p> <p>2005-06-06</p> <p>Maritime <span class="hlt">Antarctic</span> freshwater habitats are amongst the fastest changing environments on Earth. Temperatures have risen around 1 degrees C and ice cover has dramatically decreased in 15 years. Few animal species inhabit these sites, but the fairy shrimp Branchinecta gaini typifies those that do. This species survives up to 25 degrees C daily temperature fluctuations in summer and passes winter as eggs at temperatures down to -25 degrees C. Its annual temperature envelope is, therefore around 50 degrees C. This is typical of <span class="hlt">Antarctic</span> terrestrial species, which exhibit great physiological flexibility in coping with temperature fluctuations. The rapidly changing conditions in the Maritime <span class="hlt">Antarctic</span> are enhancing fitness in these species by increasing the time available for feeding, growth and reproduction, as well as increasing productivity in lakes. The future problem these animals face is via displacement by alien species from lower latitudes. Such invasions are now well documented from sub-<span class="hlt">Antarctic</span> sites. In contrast the marine <span class="hlt">Antarctic</span> environment has very stable temperatures. However, seasonality is intense with very short summers and long winter periods of low to no algal productivity. Marine animals grow slowly, have long generation times, low metabolic rates and low levels of <span class="hlt">activity</span>. They also die at temperatures between +5 degrees C and +10 degrees C. Failure of oxygen supply mechanisms and loss of aerobic scope defines upper temperature limits. As temperature rises, their ability to perform work declines rapidly before lethal limits are reached, such that 50% of populations of clams and limpets cannot perform essential <span class="hlt">activities</span> at 2-3 degrees C, and all scallops are incapable of swimming at 2 degrees C. Currently there is little evidence of temperature change in <span class="hlt">Antarctic</span> marine sites. Models predict average global sea temperatures will rise by around 2 degrees C by 2100. Such a rise would take many <span class="hlt">Antarctic</span> marine animals beyond their survival limits</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7047G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7047G"><span>The role of glacial and tectonic genesis in forming of the <span class="hlt">Antarctic</span> Peninsula's shelf topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greku, Rudolf; Greku, Tatyana</p> <p>2015-04-01</p> <p>The influence of endogenous and exogenous factors on the topography of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf is shown. 1. The gravity tomography models [Atlas…] show that the non-geotectonic depressions about 300 m of depth extends to the south from the Bransfield Rift along the western and eastern shelves of the <span class="hlt">Antarctic</span> Peninsula (AP) up to 69 °S. This is due to the glacial tectonic, which was caused by lithostatic pressure of ice mass and the corresponding deviatoric stress (as а horizontal stretching) in a period of an intense glaciation. Ice mass increases towards the south, therefore the deviatoric stretch and the width of the shelves increases also. 2. Besides such external factors, deep tomography data were taken into account. Results of tomographic modelling show the structure of the AP along its crest and along several cross sections. The AP body, as a single structure, is submerged into the lithospheres of the Pacific Ocean and the Weddell Sea to the depth of 150 km. Some layers of its deepened part are displaced concerning the AP's crest axis. The largest of these shifts are observed up to 50 km from the axis to the east at the latitude of 63°S at the depths of 6-7 km, then a shift up to 100 km to the <span class="hlt">west</span> at 66°S at the depth of 9 km and at 67°S to the east up to 150 km at the depth of 13 km. 3. After breakup of the ice shelf to the <span class="hlt">west</span> of the AP, the outflow of ice weight from the main ice board on the Peninsula increased. The consumption of the ice is evaluated now by the discharge of glaciers. Informative data for that are the satellite radar altimetry and interferometry. Several pairs of the ERS1/2 images of 1995-2008 were processed for the area of the Vernadsky Ukrainian <span class="hlt">Antarctic</span> Station. These 100km x 100km images show 4 glaciers (Deloncle, Girard, Waddington and Collins) along transverse faults. The Collins glacier is the most <span class="hlt">active</span> one. It starts at the crest of the Bruce Plateau АР at the height of 1450 m. Three smaller glaciers provide an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18697932','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18697932"><span>Ice cores record significant 1940s <span class="hlt">Antarctic</span> warmth related to tropical climate variability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schneider, David P; Steig, Eric J</p> <p>2008-08-26</p> <p>Although the 20th Century warming of global climate is well known, climate change in the high-latitude Southern Hemisphere (SH), especially in the first half of the century, remains poorly documented. We present a composite of water stable isotope data from high-resolution ice cores from the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet. This record, representative of <span class="hlt">West</span> <span class="hlt">Antarctic</span> surface temperature, shows extreme positive anomalies in the 1936-45 decade that are significant in the context of the background 20th Century warming trend. We interpret these anomalies--previously undocumented in the high-latitude SH--as indicative of strong teleconnections in part driven by the major 1939-42 El Niño. These anomalies are coherent with tropical sea-surface temperature, mean SH air temperature, and North Pacific sea-level pressure, underscoring the sensitivity of <span class="hlt">West</span> Antarctica's climate, and potentially its ice sheet, to large-scale changes in the global climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP34A..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP34A..01A"><span><span class="hlt">Antarctic</span> Miocene Climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ashworth, A. C.; Lewis, A. R.</p> <p>2013-12-01</p> <p>Fossils from <span class="hlt">Antarctic</span> Miocene terrestrial deposits, coupled with stratigraphic, geochemical and paleontological data from marine boreholes, provide new insights into the climatic history of the continent. During the Miocene, ice caps coalesced to form ice sheets and vegetated surfaces gave way to barren expanses. The cryospheric changes especially have global climatic implications. The fossil data consists of diatoms, pollen and spores, and macroscopic remains of plants, ostracods, insects, molluscs and a fish. Plant fossils include wood and leaves of Nothofagus (southern beech), seeds of several vascular plants, including Ranunculus (buttercup), Hippuris (mare's-tail) and Myriophyllum (watermilfoil), megaspores of Isoetes (quillwort), and moss species. The insect chitin consists of larval head capsules of Chironomidae (midges) and exoskeletal parts of Coleoptera (beetles). The molluscs include freshwater gastropods and bivalves. The majority of these taxa are likely descendants of taxa that had survived on the continent from the Paleogene or earlier. Even though early Miocene glaciations may have been large, the climate was never cold enough to cause the extinction of the biota, which probably survived in coastal refugia. Early Miocene (c. 20 Ma) macrofossils from the McMurdo Dry Valleys (77°S) support palynological interpretations from the Cape Roberts and ANDRILL marine records that the upland vegetation was a shrub tundra. Mean summer temperature (MST) in the uplands was c. 6°C and possibly higher at the coast. The climate was wet, supporting mires and lakes. By the mid-Miocene, even though the climate continued to be wet. MST was c. 4°C which was too cold to support Nothofagus and most vascular plant species. Stratigraphic evidence indicates that the time between the Early and Mid-Miocene was a time of repeated ice advances and retreats of small glaciers originating from ice caps. At c. 14 Ma there appears to have been a modal shift in climate to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011DSRII..58..128N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011DSRII..58..128N"><span>Revealing archaeal diversity patterns and methane fluxes in Admiralty Bay, King George Island, and their association to Brazilian <span class="hlt">Antarctic</span> Station <span class="hlt">activities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakayama, C. R.; Kuhn, E.; Araújo, A. C. V.; Alvalá, P. C.; Ferreira, W. J.; Vazoller, R. F.; Pellizari, V. H.</p> <p>2011-03-01</p> <p>The study of <span class="hlt">Antarctic</span> archaeal communities adds information on the biogeography of this group and helps understanding the dynamics of biogenic methane production in such extreme habitats. Molecular methods were combined to methane flux determinations in Martel Inlet, Admiralty Bay, to assess archaeal diversity, to obtain information about contribution of the area to atmospheric methane budget and to detect possible interferences of the <span class="hlt">Antarctic</span> Brazilian Station Comandante Ferraz (EACF) wastewater discharge on local archaeal communities and methane emissions. Methane fluxes in Martel Inlet ranged from 3.2 to 117.9 μmol CH 4 m -2 d -1, with an average of 51.3±8.5 μmol CH 4 m -2 d -1 and a median of 57.6 μmol CH 4 m -2d -1. However, three negative fluxes averaging -11.3 μmol CH 4 m -2 d -1 were detected in MacKellar Inlet, indicating that Admiralty Bay can be either a source or sink of atmospheric methane. Denaturing gradient gel electrophoresis (DGGE) showed that archaeal communities at EACF varied with depth and formed a group separated from the reference sites. Granulometric analysis indicated that differences observed may be mostly related to sediment type. However, an influence of wastewater input could not be discarded, since higher methane fluxes were found at CF site, suggesting stimulation of local methanogenesis. DGGE profile of the wastewater sample grouped separated from all other samples, suggesting that methanogenesis stimulation may be due to changes in environmental conditions rather than to the input of allochtonous species from the wastewater. 16S ribosomal DNA clone libraries analysis showed that all wastewater sequences were related to known methanogenic groups belonging to the hydrogenotrophic genera Methanobacterium and Methanobrevibacter and the aceticlastic genus Methanosaeta. EACF and Botany Point sediment clone libraries retrieved only groups of uncultivated Archaea, with predominance of Crenarchaeota representatives (MCG, MG1, MBG</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006DSRII..53.1115E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006DSRII..53.1115E"><span>Cardiovascular control in <span class="hlt">Antarctic</span> fish</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Egginton, Stuart; Campbell, Hamish; Davison, William</p> <p>2006-04-01</p> <p>The capacity for synthesis and plasma levels of stress hormones in species with a range of <span class="hlt">activity</span> patterns suggest that depressed catecholamine synthesis is typical of notothenioid fishes regardless of life style, although they are able to release extensive stores under conditions of extreme trauma. Cortisol does not appear to be an important primary stress hormone in these species. In general, vascular reactivity shows a modest α and β adrenergic tonus, but with greater potency for cholinergic and serotonergic vasoconstrictor agonists, although a dominance of vasodilatation over vasoconstriction is observed in one species. Vasomotor control mechanisms appear to be primarily a consequence of evolutionary lineage rather than low environmental temperature, but the pattern may be modified according to functional demand. These and other data confirm the cardiovascular system is dominated by cholinergic control: the heart apparently lacks adrenergic innervation, but receives inhibitory parasympathetic input that regulates heart rate (HR) by setting a resting vagal tonus. Oxygen consumption (MO 2) determined at rest and varied via specific dynamic action, in intact fish and fish that had undergone bilateral sectioning of the vagus nerve, show that HR is a good predictor of MO 2, and that the major influence on HR is the degree of vagal tone—these fish work by removing the brake rather than applying the accelerator. However, whether these traits actually represent adaptation to the <span class="hlt">Antarctic</span> environment or merely represent ancestral characteristics and their relative phylogenetic position is at present unclear.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.1109G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.1109G"><span>East-<span class="hlt">west</span> type precursor <span class="hlt">activity</span> prior to the auroral onset: Ground-based and THEMIS observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Golovchanskaya, I. V.; Kornilov, I. A.; Kornilova, T. A.</p> <p>2015-02-01</p> <p>Using ground-based optical observations, we study an auroral breakup event, focusing on the wave-like signatures of the east-<span class="hlt">west</span> (E-W) type auroral <span class="hlt">activities</span> which appear before breakup. By conjunction with the Time History of Events and Macroscale Interactions during Substorms (THEMIS) P2 and P5 measurements, it is shown that the underlying wave mode can be identified as the ballooning mode. Considering the similarity of the wave-like characteristics derived from ground-based auroral and THEMIS spacecraft observations, we argue that the E-W <span class="hlt">activities</span> under study may be related to ballooning waves propagating in the plasma sheet. The implications for mechanisms of substorm triggering are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23027947','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23027947"><span>Secreted Vago restricts <span class="hlt">West</span> Nile virus infection in Culex mosquito cells by <span class="hlt">activating</span> the Jak-STAT pathway.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Paradkar, Prasad N; Trinidad, Lee; Voysey, Rhonda; Duchemin, Jean-Bernard; Walker, Peter J</p> <p>2012-11-13</p> <p>Although <span class="hlt">West</span> Nile virus (WNV) and other arthropod-borne viruses are a major public health problem, the mechanisms of antiviral immunity in mosquitoes are poorly understood. Dicer-2, responsible for the RNAi-mediated response through the C-terminal RNase-III domain, also contains an N-terminal DExD/H-box helicase domain similar to mammalian RIG-I/MDA5 which, in Drosophila, was found to be required for <span class="hlt">activation</span> of an antiviral gene, Vago. Here we show that the Culex orthologue of Vago (CxVago) is up-regulated in response to WNV infection in a Dicer-2-dependent manner. Further, our data show that CxVago is a secreted peptide that restricts WNV infection by <span class="hlt">activation</span> of the Jak-STAT pathway. Thus, Vago appears to function as an IFN-like antiviral cytokine in mosquitoes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.1467T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.1467T"><span>Geoethical Approach to <span class="hlt">Antarctic</span> Subglacial Lakes Exploration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talalay, Pavel; Markov, Alexey; Sysoev, Mikhail</p> <p>2014-05-01</p> <p><span class="hlt">Antarctic</span> subglacial aquatic environment have become of great interest to the science community because they may provide unique information about microbial evolution, the past climate of the Earth, and the formation of the <span class="hlt">Antarctic</span> ice sheet. Nowadays it is generally recognized that a vast network of lakes, rivers, and streams exists thousands of meters beneath <span class="hlt">Antarctic</span> Ice Sheets. Up to date only four boreholes accessed subglacial aquatic system but three of them were filled with high-toxic drilling fluid, and the subglacial water was contaminated. Two recent exploration programs proposed by UK and USA science communities anticipated direct access down to the lakes Ellsworth and Whillans, respectively, in the 2012/2013 <span class="hlt">Antarctic</span> season. A team of British scientists and engineers engaged in the first attempt to drill into Lake Ellsworth but failed. US research team has successfully drilled through 800 m of <span class="hlt">Antarctic</span> ice to reach a subglacial lake Whillans and retrieve water and sediment samples. Both <span class="hlt">activities</span> used hot-water drilling technology to access lakes. Hot water is considered by the world science community as the most clean drilling fluid medium from the present point of view but it cannot solve environmental problems in total because hot-water even when heated to 90 °C, filtered to 0.2 μm, and UV treated at the surface could pick up microorganisms from near-surface snow and circulate them in great volume through the borehole. Another negative impact of hot-water circulation medium is thermal pollution of subglacial water. The new approach to <span class="hlt">Antarctic</span> subglacial lakes exploration is presented by sampling technology with recoverable autonomous sonde which is equipped by two hot-points with heating elements located on the bottom and top sides of the sonde. All down-hole sonde components will be sterilized by combination of chemical wash, HPV and UV sterilization prior using. At the beginning of the summer season sonde is installed on the surface of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.6823K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.6823K"><span><span class="hlt">Antarctic</span> mass balance changes from GRACE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kallenberg, B.; Tregoning, P.</p> <p>2012-04-01</p> <p>The <span class="hlt">Antarctic</span> ice sheet contains ~30 million km3 of ice and constitutes a significant component of the global water balance with enough freshwater to raise global sea level by ~60 m. Altimetry measurements and climate models suggest variable behaviour across the <span class="hlt">Antarctic</span> ice sheet, with thickening occurring in a vast area of East Antarctica and substantial thinning in <span class="hlt">West</span> Antarctica caused by increased temperature gradients in the surrounding ocean. However, the rate at which the polar ice cap is melting is still poorly constrained. To calculate the mass loss of an ice sheet it is necessary to separate present day mass balance changes from glacial isostatic adjustment (GIA), the response of the Earth's crust to mass loss, wherefore it is essential to undertake sufficient geological and geomorphological sampling. As there is only a limited possibility for this in Antarctica, all models (i.e. geological, hydrological as well as atmospheric) are very poorly constrained. Therefore, space-geodetic observations play an important role in detecting changes in mass and spatial variations in the Earth's gravity field. The Gravity Recovery And Climate Experiment (GRACE) observed spatial variations in the Earth's gravity field over the past ten years. The satellite detects mass variations in the Earth system including geophysical, hydrological and atmospheric shifts. GRACE itself is not able to separate the GIA from mass balance changes and, due to the insufficient geological and geomorphological database, it is not possible to model the GIA effect accurately for Antarctica. However, the results from GRACE can be compared with other scientific results, coming from other geodetic observations such as satellite altimetry and GPS or by the use of geological observations. In our contribution we compare the GRACE data with recorded precipitation patterns and mass anomalies over East Antarctica to separate the observed GRACE signal into its two components: GIA as a result of mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EurSS..43..297A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EurSS..43..297A"><span>Particle-size distribution in soils of <span class="hlt">West</span> Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abakumov, E. V.</p> <p>2010-03-01</p> <p>The particle-size distribution in soils sampled near Russian polar stations in <span class="hlt">West</span> Antarctica has been studied. It is shown that the soils of the Subantarctic zone (the Bellingshausen Station on King George Island) are characterized by a higher content of silt and clay in the fine earth fraction and by a higher content of the fine earth fraction in comparison with the soils of the proper <span class="hlt">Antarctic</span> tundra barrens near the Lenin-gradskaya Station and the <span class="hlt">Antarctic</span> cold desert near the Russkaya Station. In the latter soils, the content of rock fragments is higher than that in the soils of the <span class="hlt">Antarctic</span> tundra barrens. In the soils of the tundra barrens, a considerable accumulation of fine earth may take place in large cavities (hollows) on the stony bedrock surface. Desert pavements are formed in both types of <span class="hlt">Antarctic</span> landscapes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991EOSTr..72..474B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991EOSTr..72..474B"><span><span class="hlt">Antarctic</span> radiation exposure doubles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blue, Charles</p> <p></p> <p>New data reveal that the <span class="hlt">Antarctic</span> Peninsula received twice its normal maximum dose of hazardous solar ultraviolet radiation in December 1990. The prolonged persistence of the ozone hole over Antarctica caused an increased exposure of radiation, according to a paper published in the October issue of Geophysical Research Letters.John Frederick and Amy D. Alberts of the University of Chicago calculated the amount of ultraviolet solar spectral radiation from data collected at Palmer Station, Antarctica. During the spring of 1990 the largest observed values for ultraviolet radiation were approximately double the values expected, based on previous years. “The measurements from Palmer Station are consistent with similar data from McMurdo Sound, where a factor of three [ultraviolet radiation] enhancement was recorded, according to work by Knut Stamnes and colleagues at the University of Alaska,” Frederick said. “The radiation levels observed over Palmer Station in December 1990 may be the largest experienced in this region of the world since the development of the Earth's ozone layer,” he added.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007EAS....25..265H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007EAS....25..265H"><span>Towers for <span class="hlt">Antarctic</span> Telescopes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammerschlag, R. H.; Bettonvil, F. C. M.; Jägers, A. P. L.; Nielsen, G.</p> <p></p> <p>To take advantage of the exceptional seeing above the boundary layer on <span class="hlt">Antarctic</span> sites, a high-resolution telescope must be mounted on a support tower. An open transparent tower of framework minimizes the upward temperature-disturbed airflow. A typical minimum height is 30m. The tower platform has to be extremely stable against wind-induced rotational motions, which have to be less than fractions of an arc second, unusually small from a mechanical engineering viewpoint. In a traditional structure, structural deflections result in angular deflections of the telescope platform, which introduce tip and tilt motions in the telescope. However, a structure that is designed to deflect with parallel motion relative to the horizontal plane will undergo solely translation deflections in the telescope platform and thus will not degrade the image. The use of a parallel motion structure has been effectively demonstrated in the design of the 15-m tower for the Dutch Open Telescope (DOT) on La Palma. Special framework geometries are developed, which make it possible to construct high towers in stories having platforms with extreme stability against wind-induced tilt. These geometric solutions lead to constructions, being no more massive than a normal steel framework carrying the same load. Consequently, these lightweight towers are well suited to difficult sites as on Antarctica. A geometry with 4 stories has been worked out.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5164693','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5164693"><span>(Environmental impact statement on the US <span class="hlt">Antarctic</span> program)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reed, R.M.; Railsback, S.F.; McLean, R.B.</p> <p>1989-12-22</p> <p>Three staff members from Oak Ridge National Laboratory (ORNL) participated in a site visit to US <span class="hlt">Antarctic</span> Program (USAP) facilities at McMurdo Station, Amundsen-Scott South Pole Station, and remote field and support sites. Interviews were conducted with National Science Foundation, Navy, and ITT/<span class="hlt">Antarctic</span> Services staff responsible for environmental management functions. The ORNL team visited all facilities at McMurdo Station, three remote field camps, a Navy refueling facility, South Pole Station, and Scott Base (a New Zealand installation). In general, the team found that environmental impacts of the USAP are minor for the <span class="hlt">Antarctic</span> continent as a whole. Improvements for the handling and disposal of solid wastes and the discharge of wastewaters that have been initiated should help minimize environmental impacts of USAP <span class="hlt">activities</span>. The information collected during the site visit will be used in a draft supplemental environmental impact statement on the USAP to be published for public review in June 1990.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22914090','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22914090"><span>Recent <span class="hlt">Antarctic</span> Peninsula warming relative to Holocene climate and ice-shelf history.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mulvaney, Robert; Abram, Nerilie J; Hindmarsh, Richard C A; Arrowsmith, Carol; Fleet, Louise; Triest, Jack; Sime, Louise C; Alemany, Olivier; Foord, Susan</p> <p>2012-09-06</p> <p>Rapid warming over the past 50 years on the <span class="hlt">Antarctic</span> Peninsula is associated with the collapse of a number of ice shelves and accelerating glacier mass loss. In contrast, warming has been comparatively modest over <span class="hlt">West</span> Antarctica and significant changes have not been observed over most of East Antarctica, suggesting that the ice-core palaeoclimate records available from these areas may not be representative of the climate history of the <span class="hlt">Antarctic</span> Peninsula. Here we show that the <span class="hlt">Antarctic</span> Peninsula experienced an early-Holocene warm period followed by stable temperatures, from about 9,200 to 2,500 years ago, that were similar to modern-day levels. Our temperature estimates are based on an ice-core record of deuterium variations from James Ross Island, off the northeastern tip of the <span class="hlt">Antarctic</span> Peninsula. We find that the late-Holocene development of ice shelves near James Ross Island was coincident with pronounced cooling from 2,500 to 600 years ago. This cooling was part of a millennial-scale climate excursion with opposing anomalies on the eastern and western sides of the <span class="hlt">Antarctic</span> Peninsula. Although warming of the northeastern <span class="hlt">Antarctic</span> Peninsula began around 600 years ago, the high rate of warming over the past century is unusual (but not unprecedented) in the context of natural climate variability over the past two millennia. The connection shown here between past temperature and ice-shelf stability suggests that warming for several centuries rendered ice shelves on the northeastern <span class="hlt">Antarctic</span> Peninsula vulnerable to collapse. Continued warming to temperatures that now exceed the stable conditions of most of the Holocene epoch is likely to cause ice-shelf instability to encroach farther southward along the <span class="hlt">Antarctic</span> Peninsula.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15293950','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15293950"><span>Extracellular proteases from eight psychrotolerant <span class="hlt">Antarctic</span> strains.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vazquez, Susana C; Coria, Silvia H; MacCormack, Walter P</p> <p>2004-01-01</p> <p>Extracellular proteases from 8 <span class="hlt">Antarctic</span> psychrotolerant Pseudomonas sp. strains were purified and characterised. All of them are neutral metalloproteases, have an apparent molecular mass of 45kDa, optimal <span class="hlt">activity</span> at 40 degrees C and pH 7-9, retaining significant <span class="hlt">activity</span> at pH 5-11. With the exception of P96-18, which is less stable, all retain more than 50% <span class="hlt">activity</span> after 3 h of incubation at pH 5-9 and show low thermal stability (their half-life times range from 20 to 60 min at 40 degrees C and less than 5 min at 50 degrees C). These proteases can be used in commercial processes carried out at neutral pH and moderate temperatures, and are of special interest for their application in mixtures of enzymes where final thermal selective inactivation is needed. Results also highlight the relevance of <span class="hlt">Antarctic</span> biotopes for the isolation of protease-producing enzymes <span class="hlt">active</span> at low temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25477461','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25477461"><span>Multidecadal warming of <span class="hlt">Antarctic</span> waters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schmidtko, Sunke; Heywood, Karen J; Thompson, Andrew F; Aoki, Shigeru</p> <p>2014-12-05</p> <p>Decadal trends in the properties of seawater adjacent to Antarctica are poorly known, and the mechanisms responsible for such changes are uncertain. <span class="hlt">Antarctic</span> ice sheet mass loss is largely driven by ice shelf basal melt, which is influenced by ocean-ice interactions and has been correlated with <span class="hlt">Antarctic</span> Continental Shelf Bottom Water (ASBW) temperature. We document the spatial distribution of long-term large-scale trends in temperature, salinity, and core depth over the <span class="hlt">Antarctic</span> continental shelf and slope. Warming at the seabed in the Bellingshausen and Amundsen seas is linked to increased heat content and to a shoaling of the mid-depth temperature maximum over the continental slope, allowing warmer, saltier water greater access to the shelf in recent years. Regions of ASBW warming are those exhibiting increased ice shelf melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24868857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24868857"><span>Occurrence of a taurine derivative in an <span class="hlt">antarctic</span> glass sponge.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carbone, Marianna; Núñez-Pons, Laura; Ciavatta, M Letizia; Castelluccio, Francesco; Avila, Conxita; Gavagnin, Margherita</p> <p>2014-04-01</p> <p>The n-butanol extract of an <span class="hlt">Antarctic</span> hexactinellid sponge, Anoxycalyx (Scolymastra) joubini, was found to contain a taurine-conjugated anthranilic acid, never reported so far either as a natural product or by synthesis. The compound was inactive against human cancer cells in an in vitro growth inhibitory test, and also showed no antibacterial <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950053174&hterms=holocene&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dholocene','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950053174&hterms=holocene&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dholocene"><span>Present-day <span class="hlt">Antarctic</span> ice mass changes and crustal motion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>James, Thomas S.; Ivins, Erik R.</p> <p>1995-01-01</p> <p>The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of <span class="hlt">Antarctic</span> ice sheet mass balance are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak <span class="hlt">Antarctic</span> vertical velocities of the ICE-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene <span class="hlt">Antarctic</span> deglaciation history protrayed in ICE-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(exp 21) Pa(dot)s, then a vast geographical region in <span class="hlt">West</span> Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean mass exchange is large enough to account for a substantial portion of the observed secular polar motion (omega m(arrow dot)) and time-varying zonal gravity field.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990100907&hterms=holocene&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dholocene','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990100907&hterms=holocene&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dholocene"><span>Present-day <span class="hlt">Antarctic</span> Ice Mass Changes and Crustal Motion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>James, Thomas S.; Ivins, Erik R.</p> <p>1995-01-01</p> <p>The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of <span class="hlt">Antarctic</span> ice sheet mass balance are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak <span class="hlt">Antarctic</span> vertical velocities of the ICE-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene <span class="hlt">Antarctic</span> deglaciation history portrayed in ICE-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(exp 21) pa s, then a vast geographical region in <span class="hlt">West</span> Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean mass exchange is large enough to account for a substantial portion of the observed secular polar motion ((Omega)m(bar)) and time-varying zonal gravity field J(sub 1).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27073166','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27073166"><span>Endocrine disrupting <span class="hlt">activities</span> of surface water associated with a <span class="hlt">West</span> Virginia oil and gas industry wastewater disposal site.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kassotis, Christopher D; Iwanowicz, Luke R; Akob, Denise M; Cozzarelli, Isabelle M; Mumford, Adam C; Orem, William H; Nagel, Susan C</p> <p>2016-07-01</p> <p>Currently, >95% of end disposal of hydraulic fracturing wastewater from unconventional oil and gas operations in the US occurs via injection wells. Key data gaps exist in understanding the potential impact of underground injection on surface water quality and environmental health. The goal of this study was to assess endocrine disrupting <span class="hlt">activity</span> in surface water at a <span class="hlt">West</span> Virginia injection well disposal site. Water samples were collected from a background site in the area and upstream, on, and downstream of the disposal facility. Samples were solid-phase extracted, and extracts assessed for agonist and antagonist hormonal <span class="hlt">activities</span> for five hormone receptors in mammalian and yeast reporter gene assays. Compared to reference water extracts upstream and distal to the disposal well, samples collected adjacent and downstream exhibited considerably higher antagonist <span class="hlt">activity</span> for the estrogen, androgen, progesterone, glucocorticoid and thyroid hormone receptors. In contrast, low levels of agonist <span class="hlt">activity</span> were measured in upstream/distal sites, and were inhibited or absent at downstream sites with significant antagonism. Concurrent analyses by partner laboratories (published separately) describe the analytical and geochemical profiling of the water; elevated conductivity as well as high sodium, chloride, strontium, and barium concentrations indicate impacts due to handling of unconventional oil and gas wastewater. Notably, antagonist <span class="hlt">activities</span> in downstream samples were at equivalent authentic standard concentrations known to disrupt reproduction and/or development in aquatic animals. Given the widespread use of injection wells for end-disposal of hydraulic fracturing wastewater, these data raise concerns for human and animal health nearby.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70173847','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70173847"><span>Endocrine disrupting <span class="hlt">activities</span> of surface water associated with a <span class="hlt">West</span> Virginia oil and gas industry wastewater disposal site</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kassotis, Christopher D.; Iwanowicz, Luke R.; Akob, Denise M.; Cozzarelli, Isabelle M.; Mumford, Adam; Orem, William H.; Nagel, Susan C.</p> <p>2016-01-01</p> <p>Currently, >95% of end disposal of hydraulic fracturing wastewater from unconventional oil and gas operations in the US occurs via injection wells. Key data gaps exist in understanding the potential impact of underground injection on surface water quality and environmental health. The goal of this study was to assess endocrine disrupting <span class="hlt">activity</span> in surface water at a <span class="hlt">West</span> Virginia injection well disposal site. Water samples were collected from a background site in the area and upstream, on, and downstream of the disposal facility. Samples were solid-phase extracted, and extracts assessed for agonist and antagonist hormonal <span class="hlt">activities</span> for five hormone receptors in mammalian and yeast reporter gene assays. Compared to reference water extracts upstream and distal to the disposal well, samples collected adjacent and downstream exhibited considerably higher antagonist <span class="hlt">activity</span> for the estrogen, androgen, progesterone, glucocorticoid and thyroid hormone receptors. In contrast, low levels of agonist <span class="hlt">activity</span> were measured in upstream/distal sites, and were inhibited or absent at downstream sites with significant antagonism. Concurrent analyses by partner laboratories (published separately) describe the analytical and geochemical profiling of the water; elevated conductivity as well as high sodium, chloride, strontium, and barium concentrations indicate impacts due to handling of unconventional oil and gas wastewater. Notably, antagonist <span class="hlt">activities</span> in downstream samples were at equivalent authentic standard concentrations known to disrupt reproduction and/or development in aquatic animals. Given the widespread use of injection wells for end-disposal of hydraulic fracturing wastewater, these data raise concerns for human and animal health nearby.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=GL-2002-002527&hterms=Ozone+layer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOzone%2Blayer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=GL-2002-002527&hterms=Ozone+layer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOzone%2Blayer"><span><span class="hlt">Antarctic</span> Ozone Hole, 2000</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>Each spring the ozone layer over Antarctica nearly disappears, forming a 'hole' over the entire continent. The hole is created by the interaction of some man-made chemicals-freon, for example-with Antarctica's unique weather patterns and extremely cold temperatures. Ozone in the stratosphere absorbs ultraviolet radiation from the sun, thereby protecting living things. Since the ozone hole was discovered many of the chemicals that destroy ozone have been banned, but they will remain in the atmosphere for decades. In 2000, the ozone hole grew quicker than usual and exceptionally large. By the first week in September the hole was the largest ever-11.4 million square miles. The top image shows the average total column ozone values over Antarctica for September 2000. (Total column ozone is the amount of ozone from the ground to the top of the atmosphere. A relatively typical measurement of 300 Dobson Units is equivalent to a layer of ozone 0.12 inches thick on the Earth's surface. Levels below 220 Dobson Units are considered to be significant ozone depletion.) The record-breaking hole is likely the result of lower than average ozone levels during the <span class="hlt">Antarctic</span> fall and winter, and exceptionally cold temperatures. In October, however (bottom image), the hole shrank dramatically, much more quickly than usual. By the end of October, the hole was only one-third of it's previous size. In a typical year, the ozone hole does not collapse until the end of November. NASA scientists were surprised by this early shrinking and speculate it is related to the region's weather. Global ozone levels are measured by the Total Ozone Mapping Spectrometer (TOMS). For more information about ozone, read the Earth Observatory's ozone fact sheet, view global ozone data and see these ozone images. Images by Greg Shirah, NASA GSFC Scientific Visualization Studio.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23300621','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23300621"><span>Increased feeding and nutrient excretion of adult <span class="hlt">Antarctic</span> krill, Euphausia superba, exposed to enhanced carbon dioxide (CO₂).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saba, Grace K; Schofield, Oscar; Torres, Joseph J; Ombres, Erica H; Steinberg, Deborah K</p> <p>2012-01-01</p> <p>Ocean acidification has a wide-ranging potential for impacting the physiology and metabolism of zooplankton. Sufficiently elevated CO(2) concentrations can alter internal acid-base balance, compromising homeostatic regulation and disrupting internal systems ranging from oxygen transport to ion balance. We assessed feeding and nutrient excretion rates in natural populations of the keystone species Euphausia superba (<span class="hlt">Antarctic</span> krill) by conducting a CO(2) perturbation experiment at ambient and elevated atmospheric CO(2) levels in January 2011 along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP). Under elevated CO(2) conditions (∼672 ppm), ingestion rates of krill averaged 78 µg C individual(-1) d(-1) and were 3.5 times higher than krill ingestion rates at ambient, present day CO(2) concentrations. Additionally, rates of ammonium, phosphate, and dissolved organic carbon (DOC) excretion by krill were 1.5, 1.5, and 3.0 times higher, respectively, in the high CO(2) treatment than at ambient CO(2) concentrations. Excretion of urea, however, was ∼17% lower in the high CO(2) treatment, suggesting differences in catabolic processes of krill between treatments. <span class="hlt">Activities</span> of key metabolic enzymes, malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), were consistently higher in the high CO(2) treatment. The observed shifts in metabolism are consistent with increased physiological costs associated with regulating internal acid-base equilibria. This represents an additional stress that may hamper growth and reproduction, which would negatively impact an already declining krill population along the WAP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3530562','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3530562"><span>Increased Feeding and Nutrient Excretion of Adult <span class="hlt">Antarctic</span> Krill, Euphausia superba, Exposed to Enhanced Carbon Dioxide (CO2)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Saba, Grace K.; Schofield, Oscar; Torres, Joseph J.; Ombres, Erica H.; Steinberg, Deborah K.</p> <p>2012-01-01</p> <p>Ocean acidification has a wide-ranging potential for impacting the physiology and metabolism of zooplankton. Sufficiently elevated CO2 concentrations can alter internal acid-base balance, compromising homeostatic regulation and disrupting internal systems ranging from oxygen transport to ion balance. We assessed feeding and nutrient excretion rates in natural populations of the keystone species Euphausia superba (<span class="hlt">Antarctic</span> krill) by conducting a CO2 perturbation experiment at ambient and elevated atmospheric CO2 levels in January 2011 along the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP). Under elevated CO2 conditions (∼672 ppm), ingestion rates of krill averaged 78 µg C individual−1 d−1 and were 3.5 times higher than krill ingestion rates at ambient, present day CO2 concentrations. Additionally, rates of ammonium, phosphate, and dissolved organic carbon (DOC) excretion by krill were 1.5, 1.5, and 3.0 times higher, respectively, in the high CO2 treatment than at ambient CO2 concentrations. Excretion of urea, however, was ∼17% lower in the high CO2 treatment, suggesting differences in catabolic processes of krill between treatments. <span class="hlt">Activities</span> of key metabolic enzymes, malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), were consistently higher in the high CO2 treatment. The observed shifts in metabolism are consistent with increased physiological costs associated with regulating internal acid-base equilibria. This represents an additional stress that may hamper growth and reproduction, which would negatively impact an already declining krill population along the WAP. PMID:23300621</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27231011','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27231011"><span>Occupational and Environmental Health Risks Associated with Informal Sector <span class="hlt">Activities</span>-Selected Case Studies from <span class="hlt">West</span> Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Basu, Niladri; Ayelo, Paul Ahoumènou; Djogbénou, Luc S; Kedoté, Marius; Lawin, Herve; Tohon, Honesty; Oloruntoba, Elizabeth O; Adebisi, Nurudeen A; Cazabon, Danielle; Fobil, Julius; Robins, Thomas; Fayomi, Benjamin</p> <p>2016-08-01</p> <p>Most in the Economic Community of <span class="hlt">West</span> African States region are employed in the informal sector. While the informal sector plays a significant role in the region's economy, policymakers and the scientific community have long neglected it. To better understand informal-sector work conditions, the goal here is to bring together researchers to exchange findings and catalyze dialogue. The article showcases research studies on several economic systems, namely agriculture, resource extraction, transportation, and trade/commerce. Site-specific cases are provided concerning occupational health risks within artisanal and small-scale gold mining, aggregate mining, gasoline trade, farming and pesticide applications, and electronic waste recycling. These cases emphasize the vastness of the informal sector and that the majority of work <span class="hlt">activities</span> across the region remain poorly documented, and thus no data or knowledge is available to help improve conditions and formulate policies and programs to promote and ensure decent work conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.G33A..10C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.G33A..10C"><span><span class="hlt">Antarctic</span> VLNDEF Network for Regional Deformation Control in Absolute Reference Frame: Problems and Possible Solution.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capra, A.; Gandolfi, S.; Mancini, F.; Negusini, M.; Vittuari, L.</p> <p>2004-05-01</p> <p>VLNDEF (Victoria Land Network for DEFormationn control) Geodetic Program addresses the crustal deformation control of the Northern Victoria Land (Antarctica) by means of geodetic GPS measurements. The project is within the <span class="hlt">activity</span> of GIANT (Geodetic Infrastructure of Antarctica) SCAR Program and was established within the actions of ANTEC (<span class="hlt">ANTarctic</span> NeoTECtonics) Group of Specialists. During 1999-2000 and 2000-2001 Italian expeditions a network of 27 stations was established and completely surveyed over an area extending from the southernmost points at 70 degrees latitude south to the Oates Coast region at 76°S, corresponding to a wideness of 700 km along the south-north and 300 km in the <span class="hlt">west</span> to east directions. The average distance between stations is about of 70-80 km. During the field <span class="hlt">activities</span> in the 2002-03 expedition the whole network was surveyed. During those expeditions long time sessions of connection between VLNDEF and TAMDEF networks performed. TAMDEF is a USA NSF program for crustal deformation control on southern Victoria Land. The dataset has been processed using different package such as Bernese and Gipsy in order to compare solutions and fix the better approach for the transition between reference frame. The first solution was initially constrained in the ITRF97 solution using the TNB1 GPS permanent station coordinate provided by the SCAR GPS Epoch solution. The approach to crustal deformation determination is relevant in terms of relative regional deformation, among the network stations, and the absolute deformation study, through the connection to international reference frame. Particularly important is the study of for VLNDEF in order to integrated evaluation with other continental and regional networks, as SCAR GPS Epoch and TAMDEF.Some aspects related to the data processing in the <span class="hlt">Antarctic</span> region and the use of the ITRF2000 as reference frame will be discussed in the paper in addition to the analysis of the deformation in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22363756','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22363756"><span>Mitochondrial function in <span class="hlt">Antarctic</span> nototheniids with ND6 translocation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mark, Felix C; Lucassen, Magnus; Strobel, Anneli; Barrera-Oro, Esteban; Koschnick, Nils; Zane, Lorenzo; Patarnello, Tomaso; Pörtner, Hans O; Papetti, Chiara</p> <p>2012-01-01</p> <p>Fish of the suborder Notothenioidei have successfully radiated into the Southern Ocean and today comprise the dominant fish sub-order in <span class="hlt">Antarctic</span> waters in terms of biomass and species abundance. During evolution in the cold and stable <span class="hlt">Antarctic</span> climate, the <span class="hlt">Antarctic</span> lineage of notothenioids developed several unique physiological adaptations, which make them extremely vulnerable to the rapid warming of <span class="hlt">Antarctic</span> waters currently observed. Only recently, a further phenomenon exclusive to notothenioid fish was reported: the translocation of the mitochondrial gene encoding the NADH Dehydrogenase subunit 6 (ND6), an indispensable part of complex I in the mitochondrial electron transport system.This study investigated the potential physiological consequences of ND6 translocation for the function and thermal sensitivity of the electron transport system in isolated liver mitochondria of the two nototheniid species Notothenia coriiceps and Notothenia rossii, with special attention to the contributions of complex I (NADH DH) and complex II (Succinate DH) to oxidative phosphorylation. Furthermore, enzymatic <span class="hlt">activities</span> of NADH:Cytochrome c Oxidoreductase and Cytochrome C Oxidase were measured in membrane-enriched tissue extracts.During acute thermal challenge (0-15°C), capacities of mitochondrial respiration and enzymatic function in the liver could only be increased until 9°C. Mitochondrial complex I (NADH Dehydrogenase) was fully functional but displayed a higher thermal sensitivity than the other complexes of the electron transport system, which may specifically result from its unique amino acid composition, revealing a lower degree of stability in notothenioids in general. We interpret the translocation of ND6 as functionally neutral but the change in amino acid sequence as adaptive and supportive of cold stenothermy in <span class="hlt">Antarctic</span> nototheniids. From these findings, an enhanced sensitivity to ocean warming can be deduced for <span class="hlt">Antarctic</span> notothenioid fish.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6747620','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6747620"><span>Cenozoic evolution of the <span class="hlt">Antarctic</span> Peninsula continental margin</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Anderson, J.B. )</p> <p>1990-05-01</p> <p>Cenozoic evolution of the <span class="hlt">Antarctic</span> Peninsula continental margin has involved a series of ridge (Aluk Ridge)-trench collisions between the Pacific and <span class="hlt">Antarctic</span> plates. Subduction occurred episodically between segments of the Pacific plate that are bounded by major fracture zones. The age of ridge-trench collisions decreases from south to north along the margin. The very northern part of the margin, between the Hero and Shackleton fracture zones, has the last surviving Aluk-<span class="hlt">Antarctic</span> spreading ridge segments and the only remaining trench topography. The sedimentary cover on the northern margin is relatively thin generally less than 1.5 km, thus providing a unique setting in which to examine margin evolution using high resolution seismic methods. Over 5,000 km of high resolution (water gun) seismic profiles were acquired from the <span class="hlt">Antarctic</span> Peninsula margin during four cruises to the region. The margin is divided into discrete fracture-zone-bounded segments; each segment displays different styles of development. Highly tectonized <span class="hlt">active</span> margin sequences have been buried beneath a seaward-thickening sediment wedge that represents the passive stage of margin development Ice caps, which have existed in the <span class="hlt">Antarctic</span> Peninsula region since at least the late Oligocene, have advanced onto the continental shelf on numerous occasions, eroding hundreds of meters into the shelf and depositing a thick sequence of deposits characterized by till tongues and glacial troughs. Glacial erosion has been the main factor responsible for overdeepening of the shelf; isostasy is of secondary importance. As the shelf was lowered by glacial erosion, it was able to accommodate thicker and more unstable marine ice sheets. The shelf also became a vast reservoir for cold, saline shelf water, one of the key ingredients of <span class="hlt">Antarctic</span> bottom water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19020556','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19020556"><span>Environmental microarray analyses of <span class="hlt">Antarctic</span> soil microbial communities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yergeau, Etienne; Schoondermark-Stolk, Sung A; Brodie, Eoin L; Déjean, Sébastien; DeSantis, Todd Z; Gonçalves, Olivier; Piceno, Yvette M; Andersen, Gary L; Kowalchuk, George A</p> <p>2009-03-01</p> <p><span class="hlt">Antarctic</span> ecosystems are fascinating in their limited trophic complexity, with decomposition and nutrient cycling functions being dominated by microbial <span class="hlt">activities</span>. Not only are <span class="hlt">Antarctic</span> habitats exposed to extreme environmental conditions, the <span class="hlt">Antarctic</span> Peninsula is also experiencing unequalled effects of global warming. Owing to their uniqueness and the potential impact of global warming on these pristine systems, there is considerable interest in determining the structure and function of microbial communities in the <span class="hlt">Antarctic</span>. We therefore utilized a recently designed 16S rRNA gene microarray, the PhyloChip, which targets 8741 bacterial and archaeal taxa, to interrogate microbial communities inhabiting densely vegetated and bare fell-field soils along a latitudinal gradient ranging from 51 degrees S (Falkland Islands) to 72 degrees S (Coal Nunatak). Results indicated a clear decrease in diversity with increasing latitude, with the two southernmost sites harboring the most distinct Bacterial and Archaeal communities. The microarray approach proved more sensitive in detecting the breadth of microbial diversity than polymerase chain reaction-based bacterial 16S rRNA gene libraries of modest size ( approximately 190 clones per library). Furthermore, the relative signal intensities summed for phyla and families on the PhyloChip were significantly correlated with the relative occurrence of these taxa in clone libraries. PhyloChip data were also compared with functional gene microarray data obtained earlier, highlighting numerous significant relationships and providing evidence for a strong link between community composition and functional gene distribution in <span class="hlt">Antarctic</span> soils. Integration of these PhyloChip data with other complementary methods provides an unprecedented understanding of the microbial diversity and community structure of terrestrial <span class="hlt">Antarctic</span> habitats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3283701','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3283701"><span>Mitochondrial Function in <span class="hlt">Antarctic</span> Nototheniids with ND6 Translocation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mark, Felix C.; Lucassen, Magnus; Strobel, Anneli; Barrera-Oro, Esteban; Koschnick, Nils; Zane, Lorenzo; Patarnello, Tomaso; Pörtner, Hans O.; Papetti, Chiara</p> <p>2012-01-01</p> <p>Fish of the suborder Notothenioidei have successfully radiated into the Southern Ocean and today comprise the dominant fish sub-order in <span class="hlt">Antarctic</span> waters in terms of biomass and species abundance. During evolution in the cold and stable <span class="hlt">Antarctic</span> climate, the <span class="hlt">Antarctic</span> lineage of notothenioids developed several unique physiological adaptations, which make them extremely vulnerable to the rapid warming of <span class="hlt">Antarctic</span> waters currently observed. Only recently, a further phenomenon exclusive to notothenioid fish was reported: the translocation of the mitochondrial gene encoding the NADH Dehydrogenase subunit 6 (ND6), an indispensable part of complex I in the mitochondrial electron transport system. This study investigated the potential physiological consequences of ND6 translocation for the function and thermal sensitivity of the electron transport system in isolated liver mitochondria of the two nototheniid species Notothenia coriiceps and Notothenia rossii, with special attention to the contributions of complex I (NADH DH) and complex II (Succinate DH) to oxidative phosphorylation. Furthermore, enzymatic <span class="hlt">activities</span> of NADH∶Cytochrome c Oxidoreductase and Cytochrome C Oxidase were measured in membrane-enriched tissue extracts. During acute thermal challenge (0–15°C), capacities of mitochondrial respiration and enzymatic function in the liver could only be increased until 9°C. Mitochondrial complex I (NADH Dehydrogenase) was fully functional but displayed a higher thermal sensitivity than the other complexes of the electron transport system, which may specifically result from its unique amino acid composition, revealing a lower degree of stability in notothenioids in general. We interpret the translocation of ND6 as functionally neutral but the change in amino acid sequence as adaptive and supportive of cold stenothermy in <span class="hlt">Antarctic</span> nototheniids. From these findings, an enhanced sensitivity to ocean warming can be deduced for <span class="hlt">Antarctic</span> notothenioid fish. PMID</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004Geo....32..909S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004Geo....32..909S"><span>Relationship between <span class="hlt">Antarctic</span> sea ice and southwest African climate during the late Quaternary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stuut, Jan-Berend W.; Crosta, Xavier; van der Borg, Klaas; Schneider, Ralph</p> <p>2004-10-01</p> <p>Here we compare late Quaternary southwest African climate records from the <span class="hlt">west</span> coast of southern Africa (published winter rainfall and trade wind intensity records from a core off the coast of Namibia) to records of <span class="hlt">Antarctic</span> sea-ice extent. This comparison reveals coherent changes between <span class="hlt">Antarctic</span> sea-ice extent and the southwest African winter rain region since 45 k.y. B.P., with enhanced winter rainfall and trade-wind vigor during periods of increased sea-ice presence. We propose an oceanic and atmospheric coupling between <span class="hlt">Antarctic</span> sea ice and the winter rainfall zone of southwest Africa that may lead to increased desertification in the region if global warming persists.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...712577W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...712577W"><span>The suppression of <span class="hlt">Antarctic</span> bottom water formation by melting ice shelves in Prydz Bay</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, G. D.; Herraiz-Borreguero, L.; Roquet, F.; Tamura, T.; Ohshima, K. I.; Fukamachi, Y.; Fraser, A. D.; Gao, L.; Chen, H.; McMahon, C. R.; Harcourt, R.; Hindell, M.</p> <p>2016-08-01</p> <p>A fourth production region for the globally important <span class="hlt">Antarctic</span> bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011-2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65-34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and <span class="hlt">West</span> Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of <span class="hlt">Antarctic</span> bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of <span class="hlt">Antarctic</span> bottom water formation in a warming climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27552365','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27552365"><span>The suppression of <span class="hlt">Antarctic</span> bottom water formation by melting ice shelves in Prydz Bay.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Williams, G D; Herraiz-Borreguero, L; Roquet, F; Tamura, T; Ohshima, K I; Fukamachi, Y; Fraser, A D; Gao, L; Chen, H; McMahon, C R; Harcourt, R; Hindell, M</p> <p>2016-08-23</p> <p>A fourth production region for the globally important <span class="hlt">Antarctic</span> bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011-2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65-34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and <span class="hlt">West</span> Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of <span class="hlt">Antarctic</span> bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of <span class="hlt">Antarctic</span> bottom water formation in a warming climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4996980','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4996980"><span>The suppression of <span class="hlt">Antarctic</span> bottom water formation by melting ice shelves in Prydz Bay</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Williams, G. D.; Herraiz-Borreguero, L.; Roquet, F.; Tamura, T.; Ohshima, K. I.; Fukamachi, Y.; Fraser, A. D.; Gao, L.; Chen, H.; McMahon, C. R.; Harcourt, R.; Hindell, M.</p> <p>2016-01-01</p> <p>A fourth production region for the globally important <span class="hlt">Antarctic</span> bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011–2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65–34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and <span class="hlt">West</span> Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of <span class="hlt">Antarctic</span> bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of <span class="hlt">Antarctic</span> bottom water formation in a warming climate. PMID:27552365</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4990695','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4990695"><span><span class="hlt">Antarctic</span> last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Holloway, Max D.; Sime, Louise C.; Singarayer, Joy S.; Tindall, Julia C.; Bunch, Pete; Valdes, Paul J.</p> <p>2016-01-01</p> <p>Several studies have suggested that sea-level rise during the last interglacial implies retreat of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak <span class="hlt">Antarctic</span> temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of <span class="hlt">Antarctic</span> sea ice extent to climate warming. PMID:27526639</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27526639','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27526639"><span><span class="hlt">Antarctic</span> last interglacial isotope peak in response to sea ice retreat not ice-sheet collapse.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Holloway, Max D; Sime, Louise C; Singarayer, Joy S; Tindall, Julia C; Bunch, Pete; Valdes, Paul J</p> <p>2016-08-16</p> <p>Several studies have suggested that sea-level rise during the last interglacial implies retreat of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS). The prevalent hypothesis is that the retreat coincided with the peak <span class="hlt">Antarctic</span> temperature and stable water isotope values from 128,000 years ago (128 ka); very early in the last interglacial. Here, by analysing climate model simulations of last interglacial WAIS loss featuring water isotopes, we show instead that the isotopic response to WAIS loss is in opposition to the isotopic evidence at 128 ka. Instead, a reduction in winter sea ice area of 65±7% fully explains the 128 ka ice core evidence. Our finding of a marked retreat of the sea ice at 128 ka demonstrates the sensitivity of <span class="hlt">Antarctic</span> sea ice extent to climate warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4619065','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4619065"><span>Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East <span class="hlt">Antarctic</span> Adélie Penguin Populations</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Southwell, Colin; Emmerson, Louise; McKinlay, John; Newbery, Kym; Takahashi, Akinori; Kato, Akiko; Barbraud, Christophe; DeLord, Karine; Weimerskirch, Henri</p> <p>2015-01-01</p> <p>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 <span class="hlt">Antarctic</span> seabirds in the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula and western Ross Sea, have demonstrated that physical changes in <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> Adélie penguin breeding populations. We show that, in contrast to the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula and western Ross Sea where breeding populations have decreased or shown variable trends over the last 30 years, East <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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. PMID:26488299</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26488299','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26488299"><span>Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East <span class="hlt">Antarctic</span> Adélie Penguin Populations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Southwell, Colin; Emmerson, Louise; McKinlay, John; Newbery, Kym; Takahashi, Akinori; Kato, Akiko; Barbraud, Christophe; DeLord, Karine; Weimerskirch, Henri</p> <p>2015-01-01</p> <p>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 <span class="hlt">Antarctic</span> seabirds in the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula and western Ross Sea, have demonstrated that physical changes in <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> Adélie penguin breeding populations. We show that, in contrast to the <span class="hlt">west</span> <span class="hlt">Antarctic</span> Peninsula and western Ross Sea where breeding populations have decreased or shown variable trends over the last 30 years, East <span class="hlt">Antarctic</span> 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 <span class="hlt">Antarctic</span> 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.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C11D..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C11D..02B"><span><span class="hlt">Antarctic</span> Sea Ice Patterns and Its Relationship with Climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barreira, S.</p> <p>2015-12-01</p> <p><span class="hlt">Antarctic</span> sea ice concentration fields show a strong seasonal and interannual variation closely tied to changes in climate patterns. The Ross, Amundsen, Bellingshausen, and Weddell Seas during Summer-Autumn and the Southern Ocean regions north of these areas during Winter-Spring have the greatest sea ice variability. Principal components analysis in T- mode, Varimax-rotated applied on <span class="hlt">Antarctic</span> monthly sea ice concentration anomaly (SICA) fields for 1979-2015 (NASA Team algorithm data sets available at nsidc.org) revealed the main spatial characteristics of <span class="hlt">Antarctic</span> sea ice patterns and their relationship with atmospheric circulation. This analysis yielded five patterns of sea ice for winter-spring and three patterns for summer-autumn, each of which has a positive and negative phase. To understand the links between the SICA patterns and climate, we extracted the mean pressure and temperature fields for the months with high loadings (positive or negative) of the sea ice patterns. The first pattern of winter-spring sea ice concentration is a dipole structure between the Drake Passage and northern regions of the Bellingshausen and Weddell Seas and, the South Atlantic Ocean. The negative phase shows a strong negative SICA over the Atlantic basin. This pattern can be associated with to the atmospheric structures related to a positive SAM index and a wave-3 arrangement around the continent. That is, a strong negative pressure anomaly centered over the Bellingshausen Sea accompanied by three positive pressure anomalies in middle-latitudes. For summer-autumn, the first pattern shows two strong positive SICA areas, in the eastern Weddell Sea and the northwestern Ross Sea. A negative SICA covers the Amundsen-Bellingshausen Seas and northwest of the <span class="hlt">Antarctic</span> Peninsula. This pattern, frequently seen in summers since 2008, is associated with cool conditions over the Weddell Sea but warmer temperatures and high surface air pressure <span class="hlt">west</span>, north and northwest of the Peninsula.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP52A..08D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP52A..08D"><span>Pliocene retreat of Greenland and <span class="hlt">Antarctic</span> Ice Sheet margins (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deconto, R. M.; Pollard, D.</p> <p>2013-12-01</p> <p>The middle Pliocene epoch (~3 million years ago) is often considered an analogue for future global climatic conditions, because global mean temperatures were comparable to projections of future climate at the end of this century. Importantly, some estimates of mid-Pliocene sea level are >20 m higher than today, implying the potential for significant retreat of the East <span class="hlt">Antarctic</span> Ice Sheet (EAIS), in addition to the loss of the Greenland and <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheets (WAIS). Here, we use a hybrid ice sheet-shelf model with freely migrating grounding lines coupled to a high-resolution regional climate model to test the potential for both <span class="hlt">West</span> and East <span class="hlt">Antarctic</span> Ice Sheet retreat during the warm Pliocene and in long-term future scenarios with elevated CO2. In these simulations we apply new treatments of i) ice shelf calving (accounting for the effects of divergent ice flow and surface melt water on crevassing), ii) ice-cliff mechanics at the grounding line, iii) improved sub-glacial bathymetry using BEDMAP2, and iv) a range of plausible ocean warming scenarios based on offline ocean modeling. In warm Pliocene simulations, the combination of improved bathymetric detail and more physically based model treatments of floating and grounded calving fronts substantially increases the rates and magnitudes of ice sheet retreat into over-deepened subglacial basins in both in <span class="hlt">West</span> and East Antarctica. These new results imply the EAIS margin did indeed contribute to elevated (and orbitally paced) Pliocene sea levels, with Antarctica contributing up to ~20m equivalent sea level during the warmest intervals. In long-term (10^3-4-yr) future simulations using the same model physics, we find these new mechanisms produce a much more sensitive and vulnerable ice sheet than previously considered, with the potential for substantial future retreat of both WAIS and parts of the East <span class="hlt">Antarctic</span> margin in response to the combined effects of increased surface melt on ice shelf surfaces and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.A53B1164S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.A53B1164S"><span>Methane isotope records from <span class="hlt">Antarctic</span> firn air</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sowers, T. A.; Battle, M.</p> <p>2007-12-01</p> <p>The earth's climate is directly influenced by changes in the atmospheric loading of trace "greenhouse" gases. Methane is an important greenhouse gas whose atmospheric concentration has doubled over the last century as a result of various anthropogenic <span class="hlt">activities</span>. Understanding the methane cycle in the recent past is a compelling scientific problem because increasing methane levels in the modern atmosphere will contribute to predicted future warming. The only source of air that allows us to study the long-term cycles of these gases is found in the trapped gases in ice cores and the interstitial pore spaces in firn from the central portions of Greenland and Antarctica. Firn air samples, retrieved from the South Pole in 1995 and 2001, were analyzed for δ13CH4. In December of 2005, another suite of firn air samples was recovered from the new US deep coring site located along the <span class="hlt">west</span> <span class="hlt">Antarctic</span> divide (WAIS D) which were analyzed for both δ13C and δ D of CH4. In general, replicate flasks were sampled from each depth from two separate drillings each year. The precision of the δ13C and δ D analyses is generally better than ± 0.2‰ and 2‰, respectively, with surface values in good agreement with NOAA (INSTAAR) biweekly flask measurements from South Pole. In all cases, δ13C and δD values decrease gradually with depth below the convective zone. However, these isotopes and CH4 mixing ratios decline sharply below the "lock-in" depth. The measured firn air profiles are primarily the result of three factors. First, tropospheric changes drive compositional changes in the near-surface convective layer that are subsequently mixed downward due to bulk air-movement within the shallow firn. Secondly, gases are mixed below the convective zone solely by molecular diffusion, leading to the gradual downward propagation of the compositional changes in the convective layer. Finally, differential gravitational settling causes the heavier atmospheric constituents (both elemental</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008EAS....33..233C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008EAS....33..233C"><span>Principles of the <span class="hlt">Antarctic</span> Treaty</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Candidi, M.</p> <p></p> <p>The operation of any base or expedition to Antarctica is regulated by the mutual agreement among nations in the “<span class="hlt">Antarctic</span> Treaty”. This treaty deals with the major aspects of life in Antarctica and its main principles and provisions are described in what follows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCC...7...11S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCC...7...11S"><span>Glaciology: Vulnerable <span class="hlt">Antarctic</span> ice shelves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siegert, Martin</p> <p>2017-01-01</p> <p>The decay of floating ice shelves around Antarctica speeds up ice flow from the continent and contributes to increased sea-level rise. Now, meltwater attributed to warm winds has been discovered on an East <span class="hlt">Antarctic</span> ice shelf, suggesting greater vulnerability than previously thought.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......223S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......223S"><span>Ocean Heat Delivery Mechanisms Beneath <span class="hlt">Antarctic</span> Ice Shelves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stern, Alon</p> <p></p> <p>Ocean currents around Antarctica are responsible for transporting heat under the <span class="hlt">Antarctic</span> ice shelves and exporting cold melt-water out into the open ocean. These ocean currents are important for the determining the melt rates beneath the Antarctica ice shelves. This thesis explores the three modes of melting beneath <span class="hlt">Antarctic</span> ice shelves using laboratory experiments, analysis of field observations, and both of complex and simple numerical models. In Chapter 1, we construct a laboratory experiment to simulate the density driven circulation under an idealized <span class="hlt">Antarctic</span> ice shelf (mode 1). Results confirm that the ice front can act as a dynamic barrier that partially inhibits fluid from entering or exiting the ice shelf cavity, away from two wall-trapped boundary currents. The strength of the dynamic barrier is sensitive to changes in the ice shelf geometry and changes in the buoyancy fluxes which drive the flow. Chapter 2 explores how instabilities in topographically steered jets could be responsible for the exchange of warm Circumpolar Deep Water across the continental shelf break in <span class="hlt">West</span> Antarctica (mode 2). Results show that the majority of mixing occurs in discrete mixing events which coincide with the shelf break jet becoming baroclinically unstable. The largest instability events display a intermittent low frequency variability with instabilities occurring up to 50 years apart. Chapter 3 uses observational data to study the summer intrusion of surface waters below McMurdo Ice Shelf (mode 3). A six month temperature record collected below the ice shelf in 2011-2012 shows the temporal and spatial structure of the summertime warm water signal that penetrates beneath the ice shelf. A Ross Sea numerical model demonstrates a seasonal warm water pathway leading from the <span class="hlt">west</span> side of the Ross Sea Polynya (RSP) towards McMurdo Sound.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70018690','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70018690"><span>Satellite imagery of the onset of streaming flow of ice streams C and D, <span class="hlt">West</span> Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hodge, S.M.; Doppelhammer, S.K.</p> <p>1996-01-01</p> <p>Five overlapping Landsat multispectral scanner satellite images of the interior of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet were enhanced with principal component analysis, high-pass filtering, and linear contrast stretching and merged into a mosaic by aligning surface features in the overlap areas. The mosaic was registered to geodetic coordinates, to an accuracy of about 1 km, using the five scene centers as control points. The onset of streaming flow of two tributaries of ice stream C and one tributary of ice stream D is visible in the mosaic. The onset appears to occur within a relatively short distance, less than the width of the ice stream, typically at a subglacial topographic feature such as a step or ridge. The ice streams extend farther up into the interior than previously mapped. Ice stream D starts about 150 km from the ice divide, at an altitude of about 1500 m, approximately halfway up the convex-upward dome shape of the interior ice sheet. Ice stream D is relatively much longer than ice stream C, possibly because ice stream D is currently <span class="hlt">active</span> whereas ice stream C is currently inactive. The grounded portion of the <span class="hlt">West</span> <span class="hlt">Antarctic</span> ice sheet is perhaps best conceptualized as an ice sheet in which ice streams are embedded over most of its area, with slow moving ice converging into fast moving ice streams in a widely distributed pattern, much like that of streams and rivers in a hydrologic basin. A relic margin appears to parallel most of the south margin of the tributary of ice stream D, separated from the <span class="hlt">active</span> shear margin by about 10 km or less for a distance of over 200 km. This means there is now evidence for recent changes having occurred in three of the five major ice streams which drain most of <span class="hlt">West</span> Antarctica (B, C, and D), two of which (B and D) are currently <span class="hlt">active</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55.2438P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55.2438P"><span>14C as a tracer of labile organic matter in <span class="hlt">Antarctic</span> benthic food webs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Purinton, Brett L.; DeMaster, David J.; Thomas, Carrie J.; Smith, Craig R.</p> <p>2008-11-01</p> <p>14C measurements were made on surface plankton, particle-trap material, surface sediment, benthic invertebrate gut contents, and body tissue samples to assess the effectiveness of this radioisotope as a tracer of labile organic carbon in <span class="hlt">Antarctic</span> benthic food webs. Samples were collected on five cruises to the <span class="hlt">West</span> <span class="hlt">Antarctic</span> Peninsula (WAP) shelf between November 1999 and March 2001 as part of the Food for Benthos on the <span class="hlt">ANtarctic</span> Continental-Shelf (FOODBANCS) Project. The 14C contents of the body tissues from a variety of deposit feeders (-126±13 per mil) were substantially enriched relative to the surface sediment (-234±13 per mil) and statistically similar to the organic matter collected in plankton tows (-135±10 per mil), indicating that recently produced marine plankton are the primary source of nutrition for these deposit feeders on the <span class="hlt">West</span> <span class="hlt">Antarctic</span> shelf. Selective ingestion was the primary feeding strategy used by echiuran worms and certain holothurians (i.e. Peniagone vignoni) for incorporating labile organic carbon into their tissues as demonstrated by the large differences (105±13 per mil) between surface sediment and gut content 14C <span class="hlt">activities</span>. In contrast, digestive and/or assimilatory selection was the predominant strategy used by an irregular urchin ( Amphipneustes lorioli) and several other holothurians ( Protelpidia murrayi, Bathyplotes fuscivinculum and the head-down conveyor belt feeder, Molpadia musculus), as demonstrated by large differences (42±7 per mil) between the 14C <span class="hlt">activities</span> of their foregut or whole-gut organic contents and their body tissues. Despite large fluctuations in carbon export from the euphotic zone, benthic feeding strategies remained essentially constant over the 15-month sampling period. No seasonal variation was evident in either the 14C abundance of the deposit-feeder body tissues, or in the 14C abundance of their gut contents. The mean 14C abundance in the body tissues of the two sub-surface deposit feeders ( A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2585N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2585N"><span>Paleoclimate perspectives on <span class="hlt">Antarctic</span> ice sheet sensitivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naish, Timothy</p> <p>2015-04-01</p> <p>Near- and long-term future projections of global mean sea level rise (SLR) are hampered by a lack of understanding of the potential dynamic contribution of the polar ice sheets, and in particular the <span class="hlt">Antarctic</span> ice sheets. With the completion of the Intergovernmental Panel on Climate Change's Assessment Report a major challenge continues to be placing an upper bound in sea-level projections for 2100 and beyond. The so-called "deterministic" approach which sums observed- and model-projected trends in the known contributions (e.g. ice sheet and glacier surface mass balance, ocean thermal expansion and ground water storage changes) implies a "likely" upper bound of +100cm by 2080-2100. The "semi-empirical" approach which scales past observed sea-level change to mean surface temperature, and uses this relationship to scale future temperature scenarios, predicts a significantly higher upper bound of up to ~2m by 2100. The discrepancy between the two approaches may in part reflect the poorly understood contribution of ice dynamics - that is the rate of flow of ice sheets into the ocean. An ensemble of <span class="hlt">Antarctic</span> ice sheet models produces highly divergent results for future sea-level projections, primarily because of uncertainties around the mass changes in the East <span class="hlt">Antarctic</span> Ice Sheet with some models showing increased precipitation driving a positive mass balance overall, even with loss of the marine-based <span class="hlt">West</span> <span class="hlt">Antarctic</span> Ice Sheet (WAIS). Current best estimates suggest a 10-20cm dynamic ice sheet contribution by 2100 to global SLR. Of concern is that marine based ice sheets are highly sensitive to increases in ocean temperature at their margins and rapid disintegration may ensue if the ice sheets grounding lines retreat into deep sub-glacial basins. Recent studies show the highest rates of ice sheet thinning and retreat are occurring at locations around the WAIS where the surface ocean has warmed, and that some WAIS loss may now be irreversible. Geological records allow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6899559','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6899559"><span>Middle proterozoic tectonic <span class="hlt">activity</span> in <span class="hlt">west</span> Texas and eastern New Mexico and analysis of gravity and magnetic anomalies</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Adams, D.C.; Keller, G.R. )</p> <p>1994-03-01</p> <p>The Precambrian history of <span class="hlt">west</span> Texas and eastern New Mexico is complex, consisting of four events: Early Proterozoic orogenic <span class="hlt">activity</span> (16309-1800 Ma), formation of the western granite-rhyolite province (WGRP) (1340-1410 Ma), Grenville age tectonics (1116-1232 Ma), and middle Proterozoic extension possibly related to mid-continent rifting (1086-1109 Ma). Pre-Grenville tectonics, Grenville tectonics, and mid-continent rifting are represented in this area by the Abilene gravity minimum (AGM) and bimodal igneous rocks, which are probably younger. We have used gravity modeling and the comparison of gravity and magnetic anomalies with rock types reported from wells penetrating Precambrian basement to study the AGM and middle Proterozoic extension in this area. The AGM is an east-northeast-trending, 600 km long, gravity low, which extends from the Texas-Oklahoma border through the central basin platform (CBP) to the Delaware basin. This feature appears to predate formation of the mafic body in the CBP (1163 Ma) and is most likely related to Pre-Grenville tectonics, possibly representing a continental margin arc batholith. Evidence of middle Proterozoic extension is found in the form of igneous bodies in the CBP, the Van Horn uplift, the Franklin Mountains, and the Sacramento Mountains. Analysis of gravity and magnetic anomalies shows that paired gravity and magnetic highs are related to mafic intrusions in the upper crust. Mapping of middle Proterozoic igneous rocks and the paired anomalies outlines a 530 km diameter area of distributed east-<span class="hlt">west</span>-oriented extension. The Debaca-Swisher terrain of shallow marine and clastic sedimentary rocks is age correlative with middle Proterozoic extension. These rocks may represent the lithology of possible Proterozoic exploration targets. Proterozoic structures were reactivated during the Paleozoic, affecting both the structure and deposition in the Permian basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2010-10-13/pdf/2010-25644.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2010-10-13/pdf/2010-25644.pdf"><span>75 FR 62891 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2010-10-13</p> <p>... Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541) AGENCY: National Science Foundation. ACTION: Notice of Permit Applications Received under the <span class="hlt">Antarctic</span>... publish notice of permit applications received to conduct <span class="hlt">activities</span> regulated under the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2011-09-19/pdf/2011-23852.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2011-09-19/pdf/2011-23852.pdf"><span>76 FR 58049 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2011-09-19</p> <p>... Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541) AGENCY: National Science Foundation. ACTION: Notice of Permit Applications Received under the <span class="hlt">Antarctic</span>... publish notice of permit applications received to conduct <span class="hlt">activities</span> regulated under the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2011-09-22/pdf/2011-24358.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2011-09-22/pdf/2011-24358.pdf"><span>76 FR 58843 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2011-09-22</p> <p>... Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541) AGENCY: National Science Foundation ACTION: Notice of Permit Applications Received under the <span class="hlt">Antarctic</span>... publish a notice of permit applications received ] to conduct <span class="hlt">activities</span> regulated under the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2011-05-24/pdf/2011-12664.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2011-05-24/pdf/2011-12664.pdf"><span>76 FR 30203 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2011-05-24</p> <p>... Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541) AGENCY: National Science Foundation. ACTION: Notice of Permit Modification Received under the <span class="hlt">Antarctic</span>... publish a notice of requests to modify permits issued to conduct <span class="hlt">activities</span> regulated under the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2013-02-07/pdf/2013-02690.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2013-02-07/pdf/2013-02690.pdf"><span>78 FR 9072 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2013-02-07</p> <p>... Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541) AGENCY: National Science Foundation. ACTION: Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span>... publish a notice of permit applications received to conduct <span class="hlt">activities</span> regulated under the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2010-12-03/pdf/2010-30337.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2010-12-03/pdf/2010-30337.pdf"><span>75 FR 75501 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2010-12-03</p> <p>... Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541) AGENCY: National Science Foundation ACTION: Notice of permit applications received under the <span class="hlt">Antarctic</span>... publish notice of permit applications received to conduct <span class="hlt">activities</span> regulated under the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2013-12-19/pdf/2013-30210.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2013-12-19/pdf/2013-30210.pdf"><span>78 FR 76862 - Notice of Permit Applications Received Under the <span class="hlt">Antarctic</span> Conservation Act of 1978 (Pub. L. 95-541)</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2013-12-19</p> <p>...The National Science Foundation (NSF) is required to publish a notice of permit applications received to conduct <span class="hlt">activities</span> regulated under the <span class="hlt">Antarctic</span> Conservation Act of 1978. NSF has published regulations under the <span class="hlt">Antarctic</span> Conservation Act at Title 45 Part 670 of the Code of Federal Regulations. This is the required notice of permit applications...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMDI51B2628K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMDI51B2628K"><span>Geophysical Investigation of Australian-<span class="hlt">Antarctic</span> Ridge Using High-Resolution Gravity and Bathymetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, S. S.; Lin, J.; Park, S. H.; Choi, H.</p> <p>2015-12-01</p> <p>Much of the Australian-<span class="hlt">Antarctic</span> Ridge (AAR) has been remained uncharted until 2011 because of its remoteness and harsh weather conditions. From 2011, the multidisciplinary ridge program initiated by the Korea Polar Research Institute (KOPRI) surveyed the little-explored eastern ends of the AAR to characterize the tectonics, geochemistry, and hydrothermal <span class="hlt">activity</span> of this intermediate spreading system. In this study, we present a detailed analysis of a 300-km-long supersegment of the AAR to quantify the spatial variations in ridge morphology and axial and off-axis volcanisms as constrained by high-resolution shipboard bathymetry and gravity. The ridge axis morphology alternates between rift valleys and axial highs within relatively short ridge segments. To obtain a geological proxy for regional variations in magma supply, we calculated residual mantle Bouguer gravity anomalies (RMBA), gravity-derived crustal thickness, and residual topography for neighboring seven sub-segments. The results of the analyses revealed that the southern flank of the AAR is associated with shallower seafloor, more negative RMBA, thicker crust, and/or less dense mantle in comparison to the conjugate northern flank. Furthermore, this north-south asymmetry becomes more prominent toward the KR1 supersegment of the AAR. The axial topography of the KR1 supersegment exhibits a sharp transition from axial highs at the western end to rift valleys at the eastern end, with regions of axial highs being associated with more robust magma supply as indicated by more negative RMBA. We also compare and contrast the characteristics of the AAR supersegment with that of other ridges of intermediate spreading rates, including the Juan de Fuca Ridge, Galápagos Spreading Center, and Southeast Indian Ridge <span class="hlt">west</span> of the Australian-<span class="hlt">Antarctic</span> Discordance, to investigate the influence of ridge-hotspot interaction on ridge magma supply and tectonics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5805L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5805L"><span>Intensification of the <span class="hlt">Antarctic</span> hydrological cycle in a future warming climate: a study with CESM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lenaerts, Jan; Vizcaino, Miren; Fyke, Jeremy; van Kampenhout, Leo; van den Broeke, Michiel</p> <p>2015-04-01</p> <p>The <span class="hlt">Antarctic</span> ice sheet is currently losing mass through enhanced ice calving in <span class="hlt">West</span> Antarctica. The strong interannual and seasonal variability of <span class="hlt">Antarctic</span> ice sheet mass, however, is controlled by its surface mass balance (SMB), mainly solid precipitation. In the coming centuries, a future warming climate is expected to lead to enhanced precipitation in the <span class="hlt">Antarctic</span>, partially compensating for dynamic ice sheet loss. Here we present the climate and SMB of Antarctica as simulated by the fully coupled Community Earth System Model (CESM). It has a resolution of ~1 degree and a multilayered snow model, and is run for 350 years (1850-2200) and two climate change scenarios (RCP2.6 and RCP8.5). We show that CESM realistically simulates the contemporary climate and SMB of the ice sheet. The model shows no significant trend in <span class="hlt">Antarctic</span> SMB from 1850 to present-day, although interannual variability is large. In both future scenarios, SMB increases linearly with <span class="hlt">Antarctic</span> near-surface temperature, but also exhibits stronger extremes. In East Antarctica, months with anomalously (return period of 10 years) high SMB are projected to occur much (5-30 times, depending on scenario) more often at the end of the 21st century than nowadays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5029513','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5029513"><span>Extremophiles in an <span class="hlt">Antarctic</span> Marine Ecosystem</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dickinson, Iain; Goodall-Copestake, William; Thorne, Michael A.S.; Schlitt, Thomas; Ávila-Jiménez, Maria L.; Pearce, David A.</p> <p>2016-01-01</p> <p>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 <span class="hlt">Antarctic</span> Circumpolar Current in the Southern Ocean, to explore the potential of metagenomic approaches as a tool for bioprospecting in the search for novel functional <span class="hlt">activity</span> 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 <span class="hlt">Antarctic</span> 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. PMID:27681902</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19090255','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19090255"><span>Antibacterial <span class="hlt">activity</span> and chemical constitutions of essential oils of Thymus persicus and Thymus eriocalyx from <span class="hlt">west</span> of Iran.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Talei, Gholam Reza; Meshkatalsadat, Mohammad Hadi</p> <p>2007-11-01</p> <p>The essential oils of Thymus persicus and Thymus eriocalyx were collected in Lorestan province, <span class="hlt">west</span> of Iran and were examined by GC/MS and bacteriological tests. Twenty seven compounds representing 92.095% of T. persicus and 99.77% of Thymus eriocalyx essential oils were identified. The major constituents of T. persicus were thymol (10.71%), carvacrol (25.71%), gamma-terpinene (5.63%), alpha-pinene (1.14%), beta-pinene (1.02%), limonene (11.65%) trans-sabinene hydrate (7.78%) and 1-borneol (4.07%) and the major compounds of T. eriocalyx. were 1, 8-cinole (3.07%), L-linalool (1.01%), thymol (66.34%), caryophyllene oxide (2.96%) and carvacrol (7.5%). The oils also were examined for antibacterial <span class="hlt">activities</span> against 6 standard bacteria by the broth microdilution and disc diffusion methods. They exhibited significant antibacterial <span class="hlt">activities</span> against Staphylococcus aureus (MIC =1 : 235, MBC =1:20), Escherichia coli (MIC = 1:320, MBC =1:80) and Pseudomonas aeroginosa (MIC = MBC = 1:1280). The results were compared with control antibiotics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/ds/535/a/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/ds/535/a/"><span>USGS field <span class="hlt">activity</span> 08FSH01 on the <span class="hlt">west</span> Florida shelf, Gulf of Mexico, in August 2008</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Robbins, Lisa L.; Knorr, Paul O.; Liu, Xuewu; Byrne, Robert H.; Raabe, Ellen A.</p> <p>2009-01-01</p> <p>From August 11 to 15, 2008, a cruise led by the U.S. Geological Survey (USGS) collected air and sea surface partial pressure of carbon dioxide (pCO2), pH, dissolved inorganic carbon (DIC), and total alkalinity (TA) data on the <span class="hlt">west</span> Florida shelf. Approximately 1,600 data points were collected underway over a 650-kilometer (km) trackline using the Multiparameter Inorganic Carbon Analyzer (MICA). The collection of data extended from Crystal River southward to Marco Island, Florida (~400 km), and westward up to 160 km off the Florida coast. Discrete water samples from approximately 40 locations were also taken at specific localities to corroborate underway data measurements. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field <span class="hlt">activity</span>. For example, 08FSH01 tells us the data were collected in 2008 for the Response of Florida Shelf (FSH) Ecosystems to Climate Change project, and the data were collected during the first field <span class="hlt">activity</span> for that study in that calendar year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/ds/535/b/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/ds/535/b/"><span>USGS field <span class="hlt">activity</span> 09FSH01 on the <span class="hlt">west</span> Florida shelf, Gulf of Mexico, in February 2009</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publicatio