Requirements for Energy-Conserving Two-Way Coupling of a GCM and Ice Model

Friday, 19 December 2014
Robert Fischer1, Sophie Nowicki2, Maxwell Kelley1 and Gavin A Schmidt1, (1)NASA/GISS, New York, NY, United States, (2)NASA GSFC, Greenbelt, MD, United States
Many questions still surround how ice sheets respond to climate forcing and how those changes will affect sea level, regional and global climate. Past studies with one-way coupling have yielded useful insight into the future of present-day ice sheets. More recently, studies have used two-way coupling that conserves mass but not energy, in order to better understand possible future equilibrium states of the ice sheets and climate system.
Two-way coupling that preserves mass and energy is seen a prerequisite to effective modeling of ice sheet that probably play a significant role in many events in the paleo record: Dansgaard–Oeschger events, Heinrich events, the Younger Dryas. It may also be used to estimate errors inherent in two-way coupled strategies that do not conserve energy.
The need for energy conservation puts constraints on the GCM, the ice model, and the design of the coupler. Details of these requirements are presented as they are being implemented in the coupling of GISS ModelE with the PISM and ISSM ice sheet models, via the Glint2 coupler.