The link between climate warming and break-up of ice shelves in the Antarctic Peninsula

A review of in situ and remote-sensing data covering the ice shelves of the Antarctic Peninsula provides a series of characteristics closely associate d with rapid shelf retreat: deeply embayed ice fronts; calving of myriad sm all elongate bergs: in punctuated events; increasing flow speed; and the pr esence of melt ponds on the ice-shelf surface in the vicinity of the break- ups. As climate has warmed in the Antarctic Peninsula region, melt-season d uration and the extent of pending have increased. Most break-up events have occurred during longer melt seasons, suggesting that meltwater itself; not just warming, is responsible. Regions that show melting without pond forma tion are relatively unchanged. Melt ponds thus appear to be a robust harbin ger of ice-shelf retreat. We use these observations to guide a model of ice -shelf flow and the effects of meltwater. Crevasses present in a region of surface pending will likely fill to the brim with water. We hypothesize (bu ilding on Weertman (1973), Hughes (1983) and Van der Veen (1998)) that crev asse propagation by meltwater is the main mechanism by which ice shelves we aken and retreat. A thermodynamic finite-element model is used to evaluate ice flow and the strain field, and simple extensions of this model are used to investigate crack propagation by meltwater. The model results support t he hypothesis.