Contribution of blowing snow sublimation to the surface mass balance of Antarctica

Abstract. Blowing snow sublimation is an important boundary layer process in polar regions and is the major ablation term in the surface mass balance (SMB) of the Antarctic ice sheet. In this study, we update the blowing snow model in the Regional Atmospheric Climate Model (RACMO), version 2.3p3, to include, among other things, the effect of blowing snow sublimation in the prognostic equations for temperature and water vapour. These updates are necessary to remove undesired numerical artefacts in this version's modelled blowing snow transport fluxes. Specifically, instead of a uniformly discretised ice particle radius distribution used in the previous version of the model which limited the maximum ice particle radius to ≤ 50 μm,  we use a non-uniformly discretised ice particle radii to include all relevant ranges of radii between 2 to 300 μm without any additional computational overhead. The updated model results are compared against the meteorological observations from site D47 in Adélie Land, East Antarctica. The updates alleviate the numerical artefacts observed in the previous model results and successfully predict the power-law variation of the blowing snow fluxes with wind speed while improving the prediction of the magnitude of the blowing snow fluxes. Furthermore, we obtain an average blowing snow layer depth of 230 ± 116 m at the observation site D47, which matches well with the typical values obtained from the satellite observations. A qualitative comparison of the blowing snow frequency from updated RACMO with CALIPSO satellite observations shows that RACMO successfully predicts the blowing snow frequency. For the period 2000–2010, compared to the previous model version, the contribution of integrated blowing snow sublimation is increased by 30 %, with a yearly mean of 176 ± 4 Gt yr^-1. It contributes to a 1.2 % reduction in the integrated SMB of the Antarctic ice sheet compared to the previous model results. In addition, we observe significant changes in the sublimation in coastal and lower escarpment zone, indicating the these improvements to the climatology of blowing snow in Antarctica.