East Antarctic ice sheet retreat as a response to meltwater pulse 1A.

We develop an empirical model of East Antarctic Ice Sheet (EAIS) retreat during the last termination in Mac.Robertson Land. Exposure dating, marine cores and swath bathymetry indicate retreat from the continental shelf and ice sheet drawdown in coastal mountains began ~13 ka. Calving re-entrant bays formed during initial retreat and persisted for 100's years in Iceberg Alley and 10's years at Neilson Basin. Exposure dates in Framnes Mountains within the same drainage basin as Iceberg Alley indicate ~350 m of ice thinning was complete by ~7 ka. EAIS retreat at many sites on the Antarctic perimeter (including these three) immediately post-dated Meltwater Pulse 1A (MWP1A). Rather than being a source of MWP1A, our data support a hypothesis that rapid eustatic sea level rise during this time unhinged the ice-sheet margin from its stability point at the shelf edge. Thereafter, the rate of EAIS retreat depended on trough geometry, akin to the present-day response of fiord glaciers, until retreat ceased when sea level stabilised. Our findings reinforce a concern that marine-based portions of Antarctic Ice Sheets are vulnerable to collapse if sea level rise approaches the rates (~4m/century) achieved during MWP1A, as a consequence of melting ice in Greenland and elsewhere.Scientific Committee on Antarctic Researc