The effect of snow on Antarctic sea ice simulations in a coupled atmosphere sea ice model

The effect of a snow cover on sea ice accretion and ablation is estimated b ased on the 'zero-layer' version sea ice model of Semtner, and is examined using a coupled atmosphere-sea ice model including feedbacks and ice dynami cs effects. When snow is disregarded in the coupled model the averaged Anta rctic sea ice becomes thicker. When only half of the snowfall predicted by the atmospheric model is allowed to land on the ice surface sea ice gets th icker in most of the Weddell and Ross Seas but thinner in East Antarctic in winter, with the average slightly thicker. When twice as much snowfall as predicted by the atmospheric model is assumed to land on the ice surface se a ice also gets much thicker due to the large increase of snow-ice formatio n. These results indicate the importance of the correct simulation of the s now cover over sea ice and snow-ice formation in the Antarctic. Our results also illustrate the complex feedback effects of the snow cover in global c limate models. In this study we have also tested the use of a mean value of 0.16 Wm(-1) K-1 instead of 0.31 for the thermal conductivity of snow in th e coupled model, based on the most recent observations in the eastern Antar ctic and Bellingshausen and Amundsen Seas, and have found that the sea ice distribution changes greatly, with the ice becoming much thinner by about 0 .2 m in the Antarctic and about 0.4 m in the Arctic on average. This implie s that the magnitude of the thermal conductivity of snow is of considerable importance for the simulation of the sea ice distribution. An appropriate value of the thermal conductivity of snow is as crucial as the depth of the snow layer and the snowfall rate in a sea ice model. The coupled climate m odels require accurate values of the effective thermal conductivity of snow from observations for validating the simulated sea ice distribution under the present climate conditions.