Toward dynamic ice sheet-ocean coupling in the Energy Exascale Earth System Model (E3SM)

Xylar Asay-Davis1, Darin Scott Comeau2, Darren Engwirda3, Matthew J Hoffman4, Mark R Petersen2, Stephen F Price2, Phillip J. Wolfram Jr2 and Jonathan D Wolfe2, (1)Los Alamos National Laboratory, Fluid Dynamics and Solid Mechanics Group, Los Alamos, United States, (2)Los Alamos National Laboratory, Los Alamos, NM, United States, (3)NASA GISS, New York City, United States, (4)Los Alamos National Laboratory, Fluid Dynamics and Solid Mechanics, Los Alamos, NM, United States
The US Department of Energy (DOE) has developed the Energy Exascale Earth System Model (E3SM) with a focus, in part, on projecting and better understanding sea-level rise in a future climate. A critical part of that work is the interactions of ice sheets, particularly the Antarctic Ice Sheet (AIS), with the ocean. There are strong indications that mass loss from the AIS is primarily driven by dynamical changes in the surrounding ocean that have brought warmer waters in contact with the ice. A full understanding of contributions of the AIS to sea-level changes requires simulating feedbacks between the ice-sheet geometry, the ocean dynamics in cavities below ice shelves, and the surrounding climate. Ocean models have not been developed with dynamic boundaries in mind, so numerical techniques are needed to handle these dynamical boundaries. Here, we present new developments in E3SM to enable dynamic boundaries, including:

  • a thin-film approach to wetting and drying as the ice sheet retreats or advances,
  • high-order treatment of pressure gradients in the ocean component, allowing for large changes in ocean geometry in ice-shelf cavities,
  • dynamic masking of the interface between the ice sheet and other climate components (land, atmosphere, sea ice and ocean),
  • calculating melt fluxes in the coupler (rather than directly in the ocean component)

We compare E3SM results of the MISOMIP1 coupled ice sheet-ocean experiments against those from a previous DOE model, POPSICLES, that used different ice and ocean components and cruder coupling techniques.