Enhanced MOIDS-derived ice physical properties within CoLM revealing bare ice-snow-albedo feedback over Greenland

Abstract. Under global warming, the Greenland Ice Sheet (GrIS) is experiencing unprecedented mass loss. A key factor closely associated with this loss is the change of snow and ice albedo, which is directly influenced by the firn metamorphism. To investigate the impact of bare ice microstructure changes on the regional warming of the GrIS ablation zone, SNICAR-ADv4 (Snow, Ice and Aerosol Radiation model Adding-Doubling Version 4), a physically based radiative transfer model, is incorporated in Common Land Model version 2024 (CoLM2024). It allows the land surface model represent the ice albedo with changes in ice properties rather than using a constant ice albedo value. Meanwhile, quality control was performed on the bare ice physical property dataset input into CoLM, with multiple MODIS products combined. Using SNICAR-ADv4 reduced the overestimation of shortwave broadband albedo by 60 %, with a bias of only 0.053. Further sensitivity experiments indicate that the albedo in the bare ice region is reduced by 0.032 during the summer due to the bare ice metamorphism, producing a 2-m temperature forcing of 0.071 °C and a snow cover change of -0.011. The contraction of snow cover exposes more bare ice and will further decrease albedo and increase the ground's absorption of solar radiation, suggesting a feedback mechanism involving bare ice, snow, and albedo. This highlights the indispensable role of bare ice physical properties in the bare ice-snow-albedo feedback for amplifying melt, and more significant feedback is expected to be produced by land-atmosphere coupling model.