Evaluating Surface Mass Balance spatiotemporal variability in a regional climate model over Greenland using an ice sheet model and GRACE

The Surface Mass Balance (SMB) of the Greenland Ice Sheet (GIS) is an important contributor to changes in sea level, now, and in the future. Both modeling and observational studies have revealed accelerating loss of mass over Greenland, of which approximately 50% has been attributed to changes in SMB, with the other 50% coming from increases in glacial discharge. Regional Climate Model (RCM) estimates of SMB change are currently among the best means of obtaining estimates of SMB timeseries. Measurements of SMB over the GIS are sparse, limiting the ability to validate SMB estimates. Several studies have compared ice-sheet wide changes in mass measured by the Gravity Recovery and Climate Experiment (GRACE), satellite-derived ice discharge measurements, and RCM results, to reveal a general agreement in ice-sheet wide mass changes over the past decade, but no detailed analysis of the spatiotemporal variability of simulated SMB estimates has been conducted using these datasets. Here we make use of a high resolution gridded 50 km GRACE Mascon solution at a monthly temporal resolution, satellite-derived discharge estimates, and sub-annual estimates of mass change from the Ice Sheet System Model (ISSM), to evaluate spatiotemporal variability in SMB simulated by the Modèle Atmosphérique Régionale (MAR), a regional climate model applied over the GIS. We reveal spatial biases in MAR SMB, but find a general agreement for GIS-wide SMB fluctuations. A lag in the seasonal cycle of mass loss potentially reveals a water storage cycle in ablation zone areas.