Glacial Meltwater in the Southeast Amundsen Sea: A timeseries from 1994–2020

Abstract. Ice sheet mass loss from Antarctica is greatest in the Amundsen Sea sector, where ‘warm’ deep seawater melts and thins the bases of ice shelves hundreds of meters below the sea surface. We use nearly 1000 paired salinity and oxygen isotope analyses of seawater samples collected on seven expeditions from 1994 to 2020 to produce a time series of glacial meltwater inventory on the Southeast Amundsen Sea continental shelf. Water column salinity-ẟ¹⁸O yield freshwater endmember ẟ¹⁸O values from −30.2 ‰ to −28.4 ‰, demonstrating that regional freshwater content is dominated by deep glacial melt. The meltwater fractions display temporal variability in basal melting, with 800 m water column meltwater inventories from 7.7 m to 9.2 m. This result corroborates recent studies suggesting interannual variability in basal melt rates of West Antarctic ice shelves and is consistent with the Amundsen region’s influence on ocean salinity and density downstream in the Ross Sea.