West Antarctic Ice Shelf- Ocean Bathymetry Interactions

DESCRIPTION: This study included extensive ocean, ice shelf and seafloor measurements on NB Palmer cruises to the Bellingshausen and Amundsen Seas. Pine Island Ice Shelf was found to be melting much faster in early 2009 than when previously visited in 1994, based on calculations from CTD-O profiles along its calving front. Its glacier was discovered to have lifted off a transverse ridge, facilitating the rapid melting of thicker ice in a newly formed upstream cavity. A large, deep cyclonic gyre was documented in Pine Island Bay, and ice shelf cavity outflows were related to basal channels in the ice, small winter coastal polynyas and summer temperatures at the sea surface. Temporal variability of ocean forcing, revealed in part by bottom moored instruments, was shown to account for 2-4x changes in the melt rates of the Pine Island and Getz ice shelves, with coastward heat transport through a shelf break depression exceeding transports via episodic events. Past glacial scouring of troughs in the seafloor were inferred to have set the stage for present-day rapid melting by creating channels that now funnel warm deep water between the shelf break and ice shelf grounding zones. Increased ice shelf melting in the Amundsen Sea has contributed to downstream freshening in the Ross Sea. About half of all circumpolar ice shelf melting was shown to be coming from ten southeast Pacific ice shelves exposed to warm deep water, thereby contributing to global sea level rise via reduced buttressing of their grounded ice streams.