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Christian Schoof

Earth and Ocean Sciences
University of British Columbia

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Much of the public discussion about the contribution of ice sheets to future sea level change focuses on 'melting icecaps'. Melting does however not play a significant part in the mass budget of the Antarctic ice sheet - this is at least true for the grounded part of the ice sheet, which is not directly in contact with ocean waters - and this will largely remain the case under projected temperature increases. So how can Antarctica contribute to changing sea levels? The main mass loss mechanism from the Antarctic ice sheet is calving of icebergs, or more precisely: outflow of ice from the grounded ice sheet into floating ice shelves, from where calving occurs. This last distinction is crucial: mass loss from floating ice shelves is sea-level neutral while mass loss from a grounded ice sheet is not. I will describe what controls the rate of mass loss from a marine ice sheet and explore how changes in material properties, accumulation rates and sea levels can drive hysteresis in an ice sheet resting on an overdeepened bed below sea level, as in West Antarctica. This hysteresis mechanism can in principle account for the retreat of the West Antarctic ice sheet following the last glacial maximum, driven not by surface melting but by sea level rise due to the melting of ice sheets in the northern hemisphere. Time permitting, I will also discuss the effect of confined ice shelves and ocean warming on a marine ice sheet, focusing on the role of ice shelves in stabilizing the grounded ice sheet.