The impact of the addition of snow and its thermal properties on sea ice and leads and the subsequence effect of climate are examined in this study. The results show that the thermal properties of snow introduce competing effects on climate. The first effect is that the snow acts as an insulator, keeping the ice warm and thus thin. The second effect is that snow has a lower volumetric specific heat and volumetric heat of fusion than ice, causing it to cool, warm, and melt more easily than ice. This produces longer periods of ice free conditions during the summer and thus a warmer climate. The third effect is that snow has a higher albedo than ice. This causes a reduction in the absorbed solar energy by the entire Earth-atmosphere system and results in a cooling of the climate. The results described here indicate that the albedo effect is dominant, so that the addition of snow cools the climate. These results show that snow on sea ice is a very important factor in shapping polar climate and that significant changes in the thickness and/or extent of the snow cover could have important implications for understanding changes in our climate. ¿ American Geophysical Union 1991