How well do the regional atmospheric and oceanic models describe the Antarctic sea ice albedo?

Abstract

We assessed how well regional climate models (HCLIM, MAR, RACMO), ocean models (MetROMS-UHel, NEMO), and ERA5 reanalysis simulate Antarctic sea ice albedo, snow, and ice thickness, using in situ data from field campaigns (ISPOL, Weddell Sea, in December 2004, and Marsden, McMurdo Sound, in November 2022) and satellite observations. The simulations performed were obtained with albedo parameterisations that greatly differed in complexity. While simple albedo parameterisations performed well in specific conditions applying ad hoc tuning (for instance, RACMO reproducing the Marsden albedo time series the most accurately), they struggled in simulating key processes. The most advanced albedo scheme applied in MetROMS-UHel produced the best overall results (including the diurnal albedo variability) when compared with ISPOL albedo time series and the observed albedo distribution from CLARA-A3 satellite products. In drier sea ice regions like the Ross Sea, the key issues affecting the accuracy of albedo models are the treatment of fractional snow cover and the snow albedo dependence on snow depth. Higher-resolution models do not necessarily outperform lower-resolution models if small-scale spatial variations in sea ice concentration, snow patchiness, and blowing snow are not accounted for. We believe that integrating the most sophisticated albedo schemes into regional climate or ocean models represents a major step forward in accurately simulating surface energy processes. Moreover, high-resolution topography and sea ice concentrations would be crucial to simulate complex coastal areas such as the Marsden campaign site.