Low Post-Glacial Rebound Rates in the Weddell Sea Due to Late Holocene Ice-Sheet Readvance

Friday, 19 December 2014
Richard C A Hindmarsh1, Sarah Bradley2, Pippa L Whitehouse3, Michael Bentley3 and Matt A King4, (1)NERC British Antarctic Survey, Cambridge, CB3, United Kingdom, (2)Utrecht University, Utrecht, Netherlands, (3)University of Durham, Durham, DH1, United Kingdom, (4)University of Tasmania, Hobart, Australia
Many ice-sheet reconstructions assume monotonic Holocene retreat for the West Antarctic Ice Sheet, but an increasing number of glaciological observations infer that some portions of the ice sheet may be readvancing, following retreat behind the present-day margin. A readvance in the Weddell Sea region can reconcile two outstanding problems: (i) the present-day widespread occurrence of seemingly stable ice streams grounded on beds that deepen inland; and (ii) the inability of models of glacial isostatic adjustment to match present-day uplift rates. By combining a suite of ice loading histories that include a readvance with a model of glacial isostatic adjustment we report substantial improvements to predictions of present-day uplift rates, reconciling problematic observations of land sinking. We suggest retreat behind present grounding lines occurred when the bed was lower, and isostatic recovery has since led to shallowing, ice sheet re-grounding and readvance. Some sections of the West Antarctic Ice Sheet may be advancing unstably.