West and East Antarctic ice sheet mass losses for different Ross Ice Shelf basal melt rate scenarios

Mass loss from the Antarctic Ice Sheet is increasing, accelerating Antarctica's contribution to global sea level rise. Most mass loss is attributed to the dynamic response of grounded ice resulting from ocean-driven thinning, or atmospherically-driven collapse, of the ice shelves that provide a back-stress to their parent glaciers and ice streams. The most rapid recent mass loss is observed in the Amundsen Sea, where small ice shelves are being thinned by melting driven by warm Circumpolar Deep Water. In contrast, the water currently coming into contact with the large Ross Ice Shelf is generally cold, resulting in weak melting and a mass balance that is close to steady state. However, the ice sheet catchments buttressed by Ross Ice Shelf represent the highest potential contribution to future sea level rise, with a total sea level rise potential of 13.8 m, of which more than 80% is in the East Antarctic Ice Sheet catchments that drain through narrow valleys in the Transantarctic Mountains (TAM).

A decrease in the extent or thickness of Ross Ice Shelf could significantly reduce its buttressing effect on the grounded ice flow. We investigate how changes in Ross Ice Shelf basal melt rate patterns, in response to changes in the Ross Sea ocean and sea ice states, can affect the dynamics of the ice shelf and the adjacent grounded ice in both East and West Antarctic catchment basins. We consider several scenarios for variability in basal melting, informed by recent improvements in satellite estimates, improved understanding of ocean heat flow under the ice shelf, and projected future Ross Sea state from CMIP5 climate models. The melting scenarios are used as a forcing in the Finite Element ice sheet model, "Elmer/Ice". In the present study, we evaluate changes in ice thickness and velocity. We confirm a previous finding that West Antarctic grounded ice loss through the Siple Coast and Marie Byrd Land marine-based ice streams can increase when accelerated basal melting thins the East Antarctic side of Ross Ice Shelf. We then identify mechanisms by which ice loss through the major TAM glaciers could increase. Our findings identify the potential for future ice sheet mass loss from this sector of Antarctica, given changes in basal melting driven by plausible changes in Ross Sea ocean and sea ice states.