Using snow physical properties to constrain the ICEPACK sea ice model at McMurdo Sound, Antarctica

Snow on sea ice exerts strong controls on Antarctic sea ice thermodynamics and mass balance by modulating both radiative and conductive transfers in the surface energy budget. The high albedo of snow reduces absorbed shortwave radiation, while its relatively low but variable thermal conductivity insulates the ice, altering internal ice temperature gradients, growth rates and thus the timing and magnitude of basal heat flux to the ocean. Snow properties exhibit large spatial and temporal variability and assuming fixed snow-thermal parameters in models can bias conductive fluxes and the surface energy balance. For Antarctica in particular, thicker, storm-fed snowpacks modify vertical heat transfer. In this study we examine the influence of snow on Antarctic sea ice through the thermodynamics observed by three SIMBA bouys, which measure temperature at high spatial and temporal resolution through the snow and sea ice column. The three buoys were placed in locations with varying snow thickness (14cm, 2cm, 0cm). Using measurements of snow physical properties (thermal conductivity, surface temperature and roughness, snow grain radius, and albedo) to constrain the column physics model ICEPACK we examine the thermodynamics of the three sites. The results clearly indicate the influence of even very thin snow cover on sea ice, which makes internal sea ice temperatures much colder. The SIMBA bouy at the deeper snow site was maintained over two melt seasons and winter, and using this long time series shows that the model is most sensitive to variations in the key parameters of thermal conductivity and snow grain radius. These findings provide observationally grounded constraints on snow/ice thermodynamics that can improve sea ice models used in climate projections.