VARIATIONS IN SNOW ON SEA-ICE - A MECHANISM FOR PRODUCING CLIMATE VARIATIONS

Studies of the impact of increases in greenhouse gases on the climate system indicate that in addition to increases in temperature there will be changes in the precipitation rate, possibly both in the mean and in the extremes. While the magnitude of the changes in the precipitation rate are not well known, it is important to access the impact of the possible changes in precipitation rate and to identify the mechanisms by which these changes affect climate. In this study the impact of various precipitation rates, and thus snowfall rates, on sea ice thickness, its subsequent effect on climate, and how this effect occurs is examined. The results show that the general effect of a thin layer of snow on the sea ice surface is to thin the sea ice. When the snow is thick enough in the poleward most zone to survive the summer season, the sea ice thickens. In addition, snow cools the climate system, and this cooling increases as the snow thickens. The cooling is caused by two factors. The first is the increase in the surface albedo for an increasingly snow-covered surface, which causes a decrease in the absorbed solar radiation by the entire system. The second is the decrease in the turbulent energy transfer from the ocean to the atmosphere, which is the result of the increased insulation of the surface from the relatively warm ocean as the snow thickens and sea ice becomes more extensive through the year. Thus as the snow thickens, the climate cools.