Abstract
<p> <p id="x-x-sp0040"> Our understanding of the response of the Antarctic ice sheet to climate and ocean changes requires the improvement of current ice-atmosphere-ocean models and the accurate determination of boundary conditions such as ice thickness and extent at key time intervals, so that satellite gravity observations and isostatic models can be adjusted. However, large portions of the Antarctic margin remain understudied or lack suitable data. One key area where data are lacking, is the Sabrina Coast portion of the East Antarctic Ice Sheet (EAIS) margin where the Totten Glacier, which has the largest ice discharge in East Antarctica, is accelerating, thinning and loosing mass at high rates. In this work, we present the results of the first geological and geophysical marine survey to the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/continental-shelf" title="Learn more about Continental Shelf from ScienceDirect's AI-generated Topic Pages"> continental shelf </a> offshore of the Dalton Ice Tongue and Moscow University ice shelf, east of the Totten Glacier. The data presented include multibeam <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/swath-bathymetry" title="Learn more about Swath Bathymetry from ScienceDirect's AI-generated Topic Pages"> swath bathymetry </a> and multichannel seismic, focusing on the sea floor morphology and sedimentary section above a regional angular <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/unconformity" title="Learn more about Unconformity from ScienceDirect's AI-generated Topic Pages"> unconformity </a> separating pre- and post-Miocene glacial <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/strata" title="Learn more about Strata from ScienceDirect's AI-generated Topic Pages"> strata </a> . Sea floor scouring and <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/iceberg" title="Learn more about Iceberg from ScienceDirect's AI-generated Topic Pages"> iceberg </a> keel marks on the outer shelf, associated with gullies on the upper slope indicate that ice expanded in the past and grounded ~5 km from the shelf edge at ~450–500 mbsl, extending ~155 km north of the current Moscow University Ice Shelf. A nearly 1000 m deep area in the inner-middle shelf, oriented NW with paleo-ice flow direction indicated by mega scale glacial <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lineation" title="Learn more about Lineation from ScienceDirect's AI-generated Topic Pages"> lineations </a> (MSGL) and <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/glacial-drift" title="Learn more about Glacial Drift from ScienceDirect's AI-generated Topic Pages"> drumlins </a> , is interpreted as a cross shelf glacial trough. A series of geomorphic associations on the north-eastern side of the glacial trough includes glacial lobes, grounding zone wedges (GZW), glacial lineations and transverse ridges, which indicates slower ice, grounding line stabilization and collapse. These geomorphic associations are organized in 4 four sets representing different past ice-flow configurations reflecting changes in ice flow direction, grounding line position, location of fast and slow ice areas, and retreat pattern. Some of the geomorphic features identified are compatible with the presence of an organized subglacial <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/runoff" title="Learn more about Runoff from ScienceDirect's AI-generated Topic Pages"> drainage </a> , and others are with rapid grounding line collapse. A well-preserved series of GZWs occurring at different water depths implies they were formed during different glacial stages or cycles. The inferred diminishing ice thickness for consecutives GZWs indicates that the margin of the Antarctic ice sheet evolved to a less extensive coverage of the continental shelf through successive glacial stages or cycles. <p id="x-x-sp0045"> The identification of different ice flow configurations, evidence of subglacial water and past <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ice-margin" title="Learn more about Ice Margin from ScienceDirect's AI-generated Topic Pages"> ice margin </a> collapse indicates a dynamic ice sheet margin with varying glacial conditions and retreat modes. We observe that some of the described morphological associations are similar to those found in the Amundsen sea sector of the West Antarctic Ice Sheet (WAIS) where they are associated with ice sheet and ice stream collapse. Although further studies are needed to assess the precise timing and rates of the glacial processes involved, we conclude that there is enough evidence to support the hypothesis that the EAIS margin can behave as dynamically as the WAIS margin, especially during glacial retreat and icesheet margin collapse. </p> </p></p>
Original language | American English |
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Journal | Geomorphology |
Volume | 317 |
DOIs | |
State | Published - Sep 1 2018 |
Keywords
- East Antarctic Ice Sheet
- Glacial geomorphology
- Mega scale glacial lineations
- Grounding zone wedges
Disciplines
- Life Sciences