Deglacial and Holocene sea ice variability along the East Antarctic continental margin

The sensitivity of the East Antarctic Ice Sheet (EAIS) to the advection of relatively warm circumpolar deep water and changes in sea-ice cover, both affecting the stability of ice-shelf fronts, remains poorly constrained for the past deglacial period. Accordingly, projections of how (rapidly) the EAIS will respond to ongoing climate warming lack solid information to quantitatively evaluate the ice-ocean feedback mechanisms that drive ice-sheet disintegration. Here, we investigate the biomarker inventory (highly branched isoprenoids, phytosterols, GDGTs) of two sediment cores recently collected from the Nielsen Basin on the Mac. Robertson Shelf, East Antarctica, to evaluate if and how sea-ice variability was related to local ice-sheet dynamics and the occurrence of polynyas. Sediment core PS128_39-1, retrieved from a sedimentary basin on the mid shelf, reveals a reduced sea ice cover permitting higher phytoplankton productivity during the deglacial and an expanded sea-ice cover limiting the marine productivity during the Holocene. Sediment core PS128_41-1, obtained from a grounding zone wedge from the outer basin, also records a higher deglacial phytoplankton productivity, but a less expanded sea-ice cover and rather polynya-like conditions throughout the Holocene. Further analyses are pending and, together with refined age models and sedimentological analyses, will allow to robustly track the retreat behavior of the EAIS on the Mac. Robertson Shelf and associated oceanic drivers.