Enhanced MODIS-derived ice physical properties within the Common Land Model (CoLM) revealing bare-ice–snow albedo feedback over Greenland

Under global warming, the Greenland Ice Sheet (GrIS) is experiencing unprecedented mass loss. One key contributing factor is the change in snow and ice albedo, which is closely related to 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 Radiative Model Adding–Doubling version 4), a physically based radiative transfer model, is incorporated in the Common Land Model version 2024 (CoLM2024). It allows the land surface model to represent the ice albedo with changes in ice properties rather than using a constant ice albedo value. Quality control was conducted on the bare-ice physical property dataset input into CoLM, with multiple MODIS products combined to ensure accuracy. The application of SNICAR-ADv4 reduced the overestimation of shortwave broadband albedo by 38 %, with a bias of 0.053. Further sensitivity experiments indicate that the summer albedo in the bare-ice region is reduced by 0.032 due to the bare-ice metamorphism, producing a 2 m temperature forcing of 0.071 °C, a snow cover change of −0.011, and a snow water equivalent forcing of −1.345 mm. These changes lead to increased bare-ice exposure, further reducing albedo and enhancing solar radiation absorption by the surface, thereby reinforcing a positive feedback mechanism, which we term the bare-ice–snow albedo feedback. This highlights the critical role of bare-ice physical properties in amplifying melt through the bare-ice–snow albedo feedback, with stronger feedbacks expected in a fully coupled land–atmosphere model.