Deglaciation and future stability of the Coats Land ice margin, Antarctica

The East Antarctic Ice Sheet discharges into the Weddell Sea via the Coats Land ice margin. We have used geophysical data to determine the changing ice sheet configuration in this region through its last advance and retreat, and identify constraints on its future stability. Methods included high-resolution multibeam-bathymetry, sub-bottom profiles, seismic-reflection profiles, sediment core analysis and satellite altimetry. These provide evidence that Coats Land glaciers and ice streams merged with the palaeo-Filchner Ice Stream during the last ice advance. Retreat of this ice stream from 12.8 to 8.4 cal kyr BP resulted in its progressive southwards decoupling from Coats Land glaciers. Moraines and grounding-zone wedges document the subsequent retreat and thinning of these glaciers, loss of contact with the bed, and the formation of ice shelves, which re-advanced to pinning points on topographic highs at the distal end of their troughs. Once detached from the bed, the ice shelves were predisposed to rapid retreat back to coastal grounding lines due to reverse-bed slopes, the absence of further pinning points, and potentially to the loss of structural integrity propagating from the grounding line. These processes explain why there are no large ice shelves from 75.5-77° S.