The role of Pine Island Glacier ice shelf basal channels in deep-water upwelling, polynyas and ocean circulation in Pine Island Bay, Antarctica

Several hundred visible and thermal infrared satellite images of Antarctica's southeast Amundsen Sea from 1986 to 2011, combined with aerial observations in 2009, show a strong inverse relation between prominent curvilinear surface depressions and the underlying basal morphology of the outer Pine Island Glacier ice shelf. Shipboard measurements near the calving front reveal positive temperature, salinity and current anomalies indicative of melt-laden, deep-water outflows near and above the larger channel termini. These buoyant plumes rise to the surface and are expressed as small polynyas in the sea ice and thermal signatures in the open water. The warm upwellings also trace the cyclonic surface circulation in Pine Island Bay. The satellite coverage suggests changing modes of ocean/ ice interactions, dominated by leads along the ice shelf through 1999, fast ice and polynyas from 2000 to 2007, and larger areas of open water since 2008.