Role of elevation feedbacks and ice sheet-climate interactions on future Greenland ice sheet melt

By comparing the one- and two-way coupled simulations, we find significant changes in atmospheric blocking, precipitation and cloud formation over Greenland as the GrIS topography evolves, acting as negative feedbacks on mass loss. We also attribute part of the overestimation of mass loss in the one-way coupled simulation to an overestimation of melt in the ablation area caused by the use of a uniform temperature lapse rate to reflect the elevation differences between the atmospheric and ice sheet grids.

Furthermore, we investigate ice sheet–climate interactions in a simulation branched in year 350 from our two-way coupled simulation in which we annually reduce atmospheric CO2 by 5 % until PI concentrations are reached. During the 350-year 4×CO2 forcing period, the ice sheet loses a total mass of 1.1 m sea level equivalent, and part of its margins retreat landward. When the PI CO2 concentration is restored, melt decreases rapidly, leading to a small positive surface mass balance.

Combined with the strongly reduced ice discharge resulting from the widespread retreat of the ice sheet margin, this halts GrIS mass loss despite a remaining global warming of 2 K. The GrIS, Arctic and North Atlantic strongly interact, causing a complex transitional phase towards a colder climate during the century following the CO2 reduction. Elevated atmospheric temperatures, larger ocean heat transport and deteriorated state of the snowpack, compared to the initial pre-industrial state, result in limited regrowth of the ice sheet under reintroduced PI CO2 conditions.