Towards better simulations of ice/ocean coupling in the Amundsen Sea Sector, West Antarctica, using a coupled ice-sheet ocean model

Abstract:

In the Amundsen Sea, warm Circumpolar Deep Water
intrudes onto the continental shelf and flows into ice shelf
cavities of the West Antarctic Ice Sheet (WAIS), resulting in
high basal melt rates. Thinning of WAIS can have a large impact
on ice sheet dynamics, sea-level rise, and local and global ocean
circulation. Recent observations of rapid changes in Pine Island
Glacier have motivated many model studies. However, it
still remains difficult to simulate the evolution of glaciers in
West Antarctica accurately. Part of the difficulty stems from
poorly known boundary conditions, e.g., ocean bathymetry,
bedrock, surface atmosphere, and lateral ocean. Another set of
difficulties stems from assumptions and approximations used in
the ocean and ice sheet models. Many ocean models investigate
basal melting of ice shelves assuming constant ice shelf cavity
shape, while many ice sheet models investigate the evolution of
ice sheet using parametrized melt rate or melt rate obtained from
ocean model separately. However, several recent studies show that
glacier retreat is sensitive to basal melt and, in turn, basal
melt is sensitive to ice shelf cavity shape. To simulate the
evolution of ice shelves in West Antarctica in a more realistic
set up, we use the ISSM ice sheet model coupled to the MITgcm
ocean, sea ice, and ice shelf cavity model. We also incorporate
oceanographic observations as well as refined geometries of
glaciers and sea floor for more realistic boundary conditions. We
simulate the evolution of glaciers in Amundsen Sea (i.e., Pine
Island, Thwaites, and Getz Glaciers), and discuss its
sensitivities to ocean parameters, ice sheet and ice shelf
parameters, and bedrock topography.