Effects of snow depth forcing on Southern Ocean sea ice simulations

Abstract

The aim of this study is to investigate the competing effects of a snow layer's insulation and snow‐ice formation on thermodynamic sea ice thickness growth in response to changes in precipitation. Using optimal interpolation to assimilate Special Sensor Microwave/Imager satellite‐derived snow depths into a dynamic‐thermodynamic sea ice model, we create a daily assimilated snow depth product for the years 1992–2003. The assimilated snow depths are used to adjust National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis precipitation rates which subsequently force the model's snow depths and freshwater input. These adjusted precipitation rates are used to create a best estimate snow depth climatology. This climatology provides the basis for a series of sensitivity experiments. Precipitation rates are varied from 0.0 to a doubling of the present day precipitation. Initially, sea ice volume decreases with increasing precipitation rate multiplying factor (PRMF) because of the insulation effects of a deeper snow layer. The turning point at which the insulation effect becomes balanced by the snow to ice conversion effect ranges from PRMF = 0.50 to PRMF = 0.75, depending upon the snow thermal conductivity and density. This suggests that with present‐day precipitation rates the snow effect on Southern Ocean sea ice is dominated by snow‐ice formation rather than the snow's insulation.