A coupled climate‐sea ice model that includes land‐sea resolution in the atmosphere, a mixed layer ocean, and a ground layer is used to investigate the impact of sea ice and leads within the ice pack on climate. Results show that a feedback process between the ocean and atmosphere exists, called the lead‐temperature feedback, such that changes in the winter minimum lead fraction can cause large changes in the simulated annual zonally averaged surface air temperature in the north polar regions. Compared to a control case where the minimum lead fraction is 1.1%, these changes in temperature range from a decrease of about 1.0°K, when leads are eliminated, to an increase of 1.0°K, when the winter minimum lead fraction is increased to 4.3%. Seasonally, this temperature change ranges up to 2.0°K. An examination of the surface energy fluxes shows that the changes in the sensible heat flux, in response to changes in the lead fraction, contribute the most to these temperature changes. The absorbed solar radiation is also affected by the changes in the winter minimum lead fraction; however, the small changes in lead area during the winter and the period of open ocean during the summer reduce its impact. The increase in the sensible heat flux to the atmosphere, along with the changes in the other fluxes, in response to increases in winter minimum lead fraction, forms the positive lead‐temperature feedback between larger lead area and warming. This feedback process has major implications for both polar and global climate.

Infrared (IR) active gases, principally water vapor (H 2 O), carbon dioxide (CO 2), and ozone (O 3), naturally present in the Earth's atmosphere, absorb thermal IR radiation emitted by the Earth's surface and atmosphere. The atmosphere is warmed by this mechanism and, in turn, emits IR radiation, with a significant portion of this energy acting to warm the surface and the lower atmosphere. As a consequence the average surface air temperature of the Earth is about 30° C higher than it would be without atmospheric absorption and reradiation of IR energy [

The impact of the addition of snow and its thermal properties on sea ice and leads and the subsequent effect on 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 shaping 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.

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