Widespread thinning of the Amudsen Sea sector of West Antarctica

We present a synergistic analysis of interferometric synthetic-aperture radar (InSAR) observations of ice flow at the grounding line and satellite radar altimetry (SRA) observations of elevation change to determine the present evolution of the Amundsen Sea sector of West Antarctica. InSAR reveals that the grounding line of large glaciers is retreating rapidly, which indicates thinning; and that several major glaciers are accelerating, hence increasing their contribution to sea level rise with time. The calculated mass budget of the two largest ice streams, Pine Island and Thwaites glaciers, is certainly negative, but even larger imbalances are calculated for smaller glaciers such as Smith, Kohler, DeVicq and Land. SRA observations confirm that the elevation of this sector of the ice sheets is decreasing with time, with thinning larger nearer to the coast and propagating hundreds of km inland. The combination of mass budget and elevation change suggest that this sector of Antarctica is losing enough mass to raise global sea level by 0.2 mm/yr. In addition, SRA reveals that large sectors of ice shelves are thinning rapidly, up to 4 m/yr on Dotson ice shelf. Melting of the ice shelves does not raise sea level, but the ice shelves may exert some control on the ice discharge from the glaciers. If the ice shelves buttress the glaciers, the contribution to sea level rise of this sector of Antarctica may be larger in the future.