Getz Ice Shelf melting response to changes in ocean forcing

The large and complex Getz Ice Shelf extends along nearly half of the West Antarctic coastline in the Amundsen Sea, and is exposed to a more variable ocean environment than most other Pacific sector ice shelves. Ocean temperature, salinity and dissolved oxygen profiles acquired near its sub-ice cavity openings are used here to estimate seawater transports and meltwater fractions. More complete coverage during 2000 and 2007 brackets most of the variability observed from 1994 to 2011, and yearlong records near one ice front support the use of summer profiles to determine annual basal melt rates. We find area average rates of 1.1 and 4.1 m/yr, higher in 2007 when a larger volume of warmer deep water occupied the adjacent continental shelf, and the ocean circulation was stronger. Results are consistent with changes in thermocline depths relative to ice shelf draft and mass transports onto the adjacent continental shelf. We also calculate steady state and actual melting of 2.5 and 4.6 m/yr in 2007-2008 from satellite measurements of ice flux, modeled accumulation, and thinning from 2003-2008. This implies a positive mass balance in 2000, but negative in 2007, when the Getz was producing more meltwater than any of the larger, slower-melting or smaller, faster-melting ice shelves.