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 wil l be changes in the precipitation rate, possibly both in the mean and in the extremes. While the magnitude of the changes in the precipitati on rate are not well known, it is important to access the impact of th e possible changes in precipitation rate and to identify the mechanism s by which these changes affect climate. In this study the impact of v arious precipitation rates, and thus snowfall rates, on sea ice thickn ess, its subsequent effect on climate, and how this effect occurs is e xamined. The results show that the general effect of a thin layer of s now on the sea ice surface is to thin the sea ice. When the snow is th ick enough in the poleward most zone to survive the summer season, the sea ice thickens. In addition, snow cools the climate system, and thi s cooling increases as the snow thickens. The cooling is caused by two factors. The first is the increase in the surface albedo for an incre asingly snow-covered surface, which causes a decrease in the absorbed solar radiation by the entire system. The second is the decrease in th e turbulent energy transfer from the ocean to the atmosphere, which is the result of the increased insulation of the surface from the relati vely warm ocean as the snow thickens and sea ice becomes more extensiv e through the year. Thus as the snow thickens, the climate cools.