Regional impacts of climate change in the Arctic and Antarctic

Abstract

Regional assessments of impacts due to global climate change are a high priority in the international programs on global-change research. In the polar regions, climate models indicate an amplifications of global greenhouse warming, but there are large differences between the results of various models, and uncertainties about the magnitude and timing of the expected changes. Also, the observed high-latitude climate trends over the past few decades are much more regional and patchy than predicted by the models. As a first step in assessing possible climate impacts, model results are compared with observations of changes in temperature, precipitation, sea-ice extent, the permafrost regime and other cryospheric parameters. While considerable uncertainties remain in the long-term prediction of change, there is some agreement between model results and observed trends by season on shorter time-scales. The warming observed over the land masses of the Arctic over the past few decades is matched by corresponding observed decreases in snow cover and glacier mass balances, by thawing of the permafrost, and to a lesser degree by reductions in sea-ice extent. In Antarctica, warming in the Antarctic Peninsula and Ross Sea regions is associated with large decreases in ice-shelf areas and reduced ice thicknesses on the lakes in the McMurdo Dry Valleys. Major future impacts due to global greenhouse warming are likely to include permafrost thawing on land and its consequences for ecosystems and humans; changes in the productivity of marine ecosystems in the Arctic and Southern Oceans; economic impacts on fisheries, petroleum and other human activities; and social impacts on northern indigenous populations. Some of these impacts will have positive ramifications, but most are likelyto be detrimental. While uncertainties exist about the future, climate change in the polar regions during the past few decades can be shown to have had major impacts already which will become much more pronounced if present trends continue.