Modeling the Effects of Wind Redistribution on the Snow Mass Budget of Polar Sea Ice

Abstract

A two-dimensional numerical model of blowing snow specifically designed for sea ice environments is presented. This new model is used to quantify the snow mass lost because of blowing snow into leads, blowing snow sublimation, and the effects of snow redistribution in the presence of surface irregularities (e.g., pressure ridges and snowdrifts) and on the conductive heat flux through the ice. Results show that the percentage of blowing snow lost into open waters (i.e., the lead trap efficiency) ranges between 60% and 100%. The lead trap efficiency increases with fetch over open waters, decreases as the upwind fetch over sea ice expands, and diminishes as wind speeds and friction velocities are enhanced. Its dependence on air temperature and relative humidity, however, is relatively small. Results from the time evolution of a snowdrift show that considerable snow cover heterogeneity arises because of interactions between winds and the surface; however, the corresponding increase in the conductive heat flux through the ice remains small (an increase of approximately 0.13% for a typical snowdrift distribution over a 1-km fetch). Results show that the snow mass lost into leads (Ql) depends strongly on the number of leads (for a fixed total open water fraction), suggesting that the lead distribution also needs to be considered in a parameterization of Ql in terms of meteorological conditions and surface characteristics. The results of this study provide some basic information on the small-scale processes influencing blowing snow over sea ice; these can then be used to evaluate the precise role that blowing snow plays in the surface energy and mass balances of large-scale models.