Climatic Warming, Glaciers and Sea Level

Abstract

The modern concensus outside of the glaciological community is that “greenhouse” gases, released by human activity, will cause an unprecedented temperature rise over the next 100 years and thereby cause a socially-threatening rise of sea level. With respect to ice the concept is simple: warmer means less. The relationship between glaciers and climate is much more complex than this. Warmer also means more vapour transport and there is ample evidence from both theory and ice-core data that snow accumulation rates in both Greenland and Antarctica were lower during the last glacial period. The problem is whether the increased accumulation rates will be exceeded by increased melting of ice in the ablation areas. Antarctica could play a dominant role because of its size and very low temperatures. Only a small percent of Antarctica will increase its meltwater run-off into the ocean. Furthermore, its dynamic response time is so large that the calving rate will not change over a 200-year period. Most of the increased melt will be absorbed in the firn and the question is how much the snow accumulation rate will increase over the major part of the continent.In the northern hemisphere one has to consider the way in which the warming will manifest itself seasonally. Most of the “forecasts” indicate that most of the warming will occur in the winter rather than the summer. In this case one has to consider the balance between greatly increased winter snowfall rates and only slightly increased summer melt rates. In this respect a review of the snow accumulation and ice melt rates from different glaciers and ice caps in the Canadian Arctic Islands is pertinent. Over the past 20 to 30 years we see no sign of a trend of either side of the balance equation (accumulation, melt). Is this the effect of high noise levels or is there simply no trend?Finally, we review the ground-ice potential in terms of sea-level change. Ground ice may not form a large part of the world's ice reserves but it covers a large area. Both increased snowfall rates in winter, and summer warming will move to increase the thickness of the active layer. This will result in run-off to the oceans.Global circulation models might be modified to determine a “best guess” of future sea-level change. To do this they must incorporate all of the parameters considered in this paper.