Evaluation of albedo and elevation feedbacks on Greenland complete deglaciation in a CMIP model: comparison of coupled and uncoupled simulations

We present here a multi-century simulation of future Greenland ice sheet evolution under 4xCO2 forcing with the Community Earth System Model version 2 bi-directionally coupled to the Community Earth Sheet Model version 2 (CESM2-CISM2). We examine the evolution of global climate, ice sheet topography and flow, as well as the individual components of the surface mass and energy balance. We compare results with a simulation with uni-directional coupling, where the atmosphere and land components see a prescribed pre-industrial ice sheet topography, and the ocean sees prescribed pre-industrial freshwater fluxes corresponding to the initial CESM2-CISM2 state in the two-way coupled baseline simulation. We find that albedo feedback causes the solar flux to be the primary energy contributor to total melt of the ice sheet. Changes in ice sheet elevation reduce the input of snowfall to the ice sheet due to enhanced rain over snow partition of precipitation. Changes in elevation cause more than doubling of melt rates after the ice sheet area has decreased by more than 50%.