Differing high-resolution Greenland ice sheet and peripheral ice caps surface mass balance since 1940

In the last decades, the Greenland ice sheet (GrIS) and its peripheral ice caps (GICs) have been rapidly losing mass through increased solid ice discharge and declining surface mass balance (SMB), i.e., the difference between precipitation accumulation and ablation from sublimation and surface runoff. Capturing SMB and its components at the local scale, notably across rapidly melting glaciers and ice caps, is therefore essential to accurately quantify Greenland’s contribution to global sea-level rise.

Here we compare long-term SMB reconstructions from two ERA5-forced regional climate models at ~5 km (MARv3.14 and RACMO2.3p2), further statistically downscaled to 500 m spatial resolution (1940-2024). These products are evaluated using in-situ measurements covering accumulation and ablation zones, as well as remotely sensed mass change records, showing good agreement. While the two models align Greenland-wide in terms of integrated SMB, individual components differ suggesting error compensation. MAR generally experiences both higher inland precipitation accumulation and larger surface runoff in marginal ablation zones than RACMO2, yielding approximately equivalent integrated SMB estimates. We examine these differences at the GrIS and GICs scale and further explore our products’ sensitivity to spatial resolution using corresponding downscaled SMB at 1 km.