Glacial Geomorphology of the Eastern Antarctic Peninsula Shelf



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During the last glacial maximum, grounded ice from the expanded Antarctic Peninsula Ice Sheet extended across the continental shelf. Grounded and flowing ice carved a distinctive array of glacial geomorphic features into the seafloor, which were gradually exposed as the ice pulled back. The recent disintegration of the northern parts of the Larsen Ice Shelf (Larsen A and B) have permitted acquisition of marine geophysical data in previously unmapped areas. A Korea Polar Research Institute (KOPRI) cruise, completed in 2013, collected new multibeam swath bathymetry data and 3.5 kHz CHIRP sub-bottom profiles within the Larsen A and B embayments, and adjacent to the current Larsen C Ice Shelf. This new multibeam dataset has been merged with pre-existing datasets from the U.S. and British Antarctic programs to permit the mapping and interpretation of ice flow across the eastern Antarctic Peninsula shelf. CHIRP profiles were analyzed to determine shallow seafloor lithology, and to correlate with mapped geomorphic features. The evolving ice-flow path and dynamic ice sheet geometry of the eastern Antarctic Peninsula has been reconstructed, with particular focus paid to newly surveyed areas that shed light on the dynamics of a marine-terminating glacial geomorphic environment, where ice shelves play a major role in grounding line stability. I have noted three major paleo-ice streams, previously identified by several studies, to flow isochronously, with no major flow deactivations throughout ice sheet retreat. Transient flow directions were mapped across the Seal Nunataks, indicating a flow reorientation reflective of result of the changing ice sheet geometry as retreat neared the coastline. Drumlins within the eastern Antarctic Peninsula are wider and longer than in other glacial environments. Mega scale glacial lineations are noted to fall slightly above the geometric averages of width and length. These measured flow indicators reveal comparatively high elongation ratios (<20), indicating rapid ice flow. Glacial moraines are conspicuously absent in the study area. Ice sheet grounding lines since the last glacial maximum have been reconstructed from 20 to 10 ka, in time slices of 1 ka. Evidence of previous ice shelf collapses are noted near the shelf break, further illustrating the critical, protective effect that ice shelves impart to marine terminating glacial environments.



Glacial geomorphology, Multibeam, Antarctic Peninsula