A Factor Two Difference in 21st-Century Greenland Ice Sheet Surface Mass
Balance Projections from Three Regional Climate Models for a Strong
Warming Scenario (SSP5-8.5)
Abstract
The Arctic is warming rapidly, significantly reducing the Greenland ice
sheet (GrIS) surface mass balance (SMB) and raising its contribution to
global sea-level rise. Since these trends are expected to continue, it
is essential to explore the GrIS SMB response to projected climate
warming. We compare projections from three polar regional climate
models, RACMO, MAR, and HIRHAM, forced by the Community Earth System
Model CESM2 under a high-end warming scenario (SSP5-8.5, 1970-2099). We
reveal different modeled SMB by 2100, including a twofold larger annual
surface mass loss in MAR (-1735 Gt/yr) and HIRHAM (-1698 Gt/yr) relative
to RACMO (-964 Gt/yr). Discrepancies primarily stem from differences in
projected runoff, triggering melt-albedo positive feedback and
subsequent modelled ablation zone expansion. In addition, we find
different responses of modeled meltwater production to similar
atmospheric warming. Our analysis suggests clear avenues for model
developments to further improve SMB projections and contribution to
sea-level rise.