A ‘Geometric’ Downscaling Method for Coupling Dynamical Ice Sheet Models to GEOS-5

Friday, 19 December 2014
Bin Zhao1, Richard I Cullather2, Sophie Nowicki3 and Max Suarez1, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)NASA/GSFC Code 610.1, Greenbelt, MD, United States, (3)NASA GSFC, Greenbelt, MD, United States
Plausible projection of future sea level rises requires coupled AOCGMs to include a dynamic ice sheet model (ISM) component. Getting the right forcing on the ice sheet models plays a critical role in the coupling process. The issue is further complicated by the mismatch between the grids used by atmosphere and ice sheet. Typically surface mass balance (SMB) and temperature fields are downscaled from the coarse atmospheric grid to the fine ice grid. We present one technique employed to couple NASA Goddard GEOS5 AGCM to JPL Ice Sheet System Model (ISSM). The Greenland ice surface from ISSM is explicitly embedded in the GEOS5 AGCM grid with a ‘tile’ representation. Atmospheric forcing fields are interpolated and further adjusted to account for elevation differences and fed into a SMB model operating on ice surface tiles. The coupling is done in such a way that mass and energy are conserved. The proposed method is independent of the underlying ice grid and can be used to couple any ISM. Comparison of resultant downscaled SMB fields from a suite of AGCM resolutions will be discussed.