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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FIG. 1 Map of a portion of the West Antarctic ice sheet17 with the ice sheet and ice shelves lightly shaded. The South Pole is marked by a box in the upper right corner and the surface elevations are shown with 500-m contours. The approximate regions of exposed bedrock are darkly shaded while the ...
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-01-25
    Description: 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.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center, The First Annual West Antarctic Ice Sheet (WAIS) Science Workshop; p 27
    Format: text
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  • 3
    Publication Date: 2019-01-25
    Description: 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.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center, The First Annual West Antarctic Ice Sheet (WAIS) Science Workshop; p 26
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Water plays a crucial role in ice-sheet stability and the onset of ice streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence ice-sheet dynamics are unknown, however, and large subglacial ...
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The subglacial Lake Vostok may be a unique reservoir of genetic material and it may contain organisms with distinct adaptations, but it has yet to be explored directly. The lake and the overlying ice sheet are closely linked, as the ice-sheet thickness drives the lake circulation, while melting ...
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  • 6
    Publication Date: 2017-10-17
    Description: Gravity anomalies provide a tool to study crustal structure, effective elastic thickness, and isostatic and tectonic processes. Over the last 10 years major airborne gravity surveys were flown by the international community over several Antarctic frontiers. The longer-wavelength Antarctic gravity anomaly field is increasingly better resolved with satellite-gravity. These recent airborne and satellite gravity datasets provide novel perspectives on Antarctic crustal structure and geodynamic evolution. We review results from some of these surveys over the Gamburtsev Subglacial Mountains, Dronning Maud Land, the Wilkes Subglacial Basin, the Transantarctic Mountains and the West Antarctic Rift System and present gravity modelling outputs of crustal thickness for these regions. We contrast these gravity results with a seismically-derived estimation of Antarctic crustal thickness (Baranov and Morelli, 2013, Tectonophys). Anomalously thick East Antarctic crust lies beneath the Gamburtsev Mountains and parts of Dronning Maud Land (50-58 km). Crustal thickening may stem from the collision of a mosaic of East Antarctic crustal provinces in Meso to Neoproterozoic times (Ferraccioli et al., 2011, Nature), or during younger Edicaran to early Cambrian “Pan-African age” orogenic events. The preservation of such thick crust provides significant support for the high bedrock topography in East Antarctica. Additional flexural uplift along the flanks of the Permian to Cretaceous East Antarctic Rift System helps explain the enigmatic Gamburtsev Mountains. Lithospheric flexure along the flank of the West Antarctic Rift System (WARS) may explain the Transantarctic Mountains (TAM), the longest and highest non-compressional mountain range on Earth. Whether the Wilkes Subglacial Basin also developed in response to lithospheric flexure is debated. Our gravity models image thicker crust beneath the Transantarctic Mountains (TAM) (ca 40 km thick), compared to the relatively thinner crust (30-35 km) beneath the Wilkes Subglacial Basin (Jordan et al., 2013 Tectonophys); this is difficult to reconcile with previous flexural model predictions. Three geodynamic processes could explain the thicker crust beneath the TAM: i) Cambrian-Ordovician subduction and accretion along the East Antarctic craton margin; ii) formation of a Paleozoic to Mesozoic plateau in West Antarctica that collapsed leaving behind a region of thicker crust; iii) extensive Jurassic magmatic underplating related to Gondwana break-up. Gravity modelling helps trace the WARS beneath the West Antarctic Ice Sheet (WAIS). The interior Ross Sea Embayment features 25-28 km-thick crust, while parts of the Amundsen Sea Embayment (ASE) are underlain by 19-23 km-thick crust. Narrow Cenozoic rifts may be interspersed with regions of more distributed Cretaceous extension, explaining the anomalously thin crust and lower Te values beneath the ASE. Major contrasts within the WARS are relevant also for the WAIS as these likely exert a key influence on geothermal heat flux variations, which in turn influence basal melting and ice motion.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 7
    Publication Date: 2017-10-17
    Description: The Antarctic Digital Magnetic Anomaly Project completed the first international magnetic anomaly compilation of the Antarctic region south of 60
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 8
    Publication Date: 2019-07-13
    Description: Meltwater stored in ponds and crevasses can weaken and fracture ice shelves, triggering their rapid disintegration. This ice-shelf collapse results in an increased flux of ice from adjacent glaciers and ice streams, thereby raising sea level globally. However, surface rivers forming on ice shelves could potentially export stored meltwater and prevent its destructive effects. Here we present evidence for persistent active drainage networks-interconnected streams, ponds and rivers-on the Nansen Ice Shelf in Antarctica that export a large fraction of the ice shelf's meltwater into the ocean. We find that active drainage has exported water off the ice surface through waterfalls and dolines for more than a century. The surface river terminates in a 130-metre-wide waterfall that can export the entire annual surface melt over the course of seven days. During warmer melt seasons, these drainage networks adapt to changing environmental conditions by remaining active for longer and exporting more water. Similar networks are present on the ice shelf in front of Petermann Glacier, Greenland, but other systems, such as on the Larsen C and Amery Ice Shelves, retain surface water at present. The underlying reasons for export versus retention remain unclear. Nonetheless our results suggest that, in a future warming climate, surface rivers could export melt off the large ice shelves surrounding Antarctica-contrary to present Antarctic ice-sheet models, which assume that meltwater is stored on the ice surface where it triggers ice-shelf disintegration.
    Keywords: Meteorology and Climatology; Numerical Analysis; Earth Resources and Remote Sensing
    Type: GSFC-E-DAA-TN42703 , Nature (ISSN 0028-0836) (e-ISSN 1476-4687); 544; 7650; 344-348
    Format: text
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  • 9
    Publication Date: 2019-07-13
    Description: Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-core records. Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (〈 or = 200 sq km) with reduced surface accumulation. Estimates of Antarctic surface mass balance rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net mass input in wind-scour zones. Here we combine airborne radar observations of unconformable stratigraphic layers with lidar-derived surface roughness measurements to identify extensive wind-scour zones over Dome A, in the interior of East Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that approx. 2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow mass input is overestimated by 11-36.5 Gt /yr in present surface-mass-balance calculations.
    Keywords: Geophysics; Meteorology and Climatology
    Type: GSFC-E-DAA-TN7511 , Nature Geoscience; 6; 367-371
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  • 10
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    In:  Earth and Planetary Science Letters ; Year: 2009 ; Volume: 288 ; Pages: 194-203
    Publication Date: 2015-07-29
    Keywords: ddc:550
    Type: http://purl.org/escidoc/metadata/ves/publication-types/article
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