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Realistic representation of bare-ice albedo: Effects on Greenland surface mass balance in the Energy Exascale Earth System Model (E3SM)

Presentation Date
Thursday, December 14, 2023 at 2:10pm - Thursday, December 14, 2023 at 6:30pm
MC - Poster Hall A-C - South



Surface melt from the Greenland Ice Sheet (GrIS) is a large contributor to sea level rise. Melt on the surface of the ice sheet is partially controlled by the surface albedo, with significant variability in the albedo of bare ice. Recent work has shown that the GrIS ablation zone is expanding and darkening due to increased bare ice exposure and more accumulation of light-absorbing constituents on the ice. Earth system models do not accurately describe ice albedo variability and often prescribe bare ice albedo as a constant value, resulting in uncertainties in the associated meltwater production. We have improved the physical representation of bare ice by incorporating a new radiative transfer scheme in E3SM. We utilize the methods employed in the Snow, Ice, and Aerosol Radiative transfer Adding-Doubling model version 4 (SNICAR-ADv4), combined with MODIS reflectance and albedo products, to simulate realistic spatially and temporally varying GrIS bare ice albedo from 2000-2021.By the end of the 21-year simulation, the constant albedo scheme results in a net overestimation in albedo in regions with exposed bare ice with an average deviation of 0.049 from the MODIS albedo. The SNICAR-ADv4 enabled simulations accurately reproduce the MODIS broadband albedo with an average deviation of 0.0003 from MODIS albedo. The inclusion of the SNICAR-ADv4 albedo scheme increases the average melt on the GrIS surface by 7 Gt/year from 2000-2022. The importance of bare ice albedo will likely increase as more ice is exposed due to rapid polar warming. To capture this effect, we’ve also developed a climatology of bare ice properties that allows E3SM to be run with SNICAR-ADv4 for any time period, assuming the MODIS era bare ice albedo is representative of the climatological albedo.
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