The Arctic as the Hotbed of Climate Change

While it had long been expected that the Arctic's floating sea ice cover would be especially sensitive to global warming, the observed rate of ice loss over the past 30 years has outstripped nearly all expectations. Over the period of modern satellite observations, September sea ice extent has declined at a rate of 10%/decade. The summer of 2007 saw a dramatic loss of sea ice, an event that shattered all previous records. Widespread coverage of young thin ice this past spring has set the stage for a similar event in summer 2008. The Arctic Ocean may well be on the verge of rapid transition towards nearly ice free summer conditions. There are growing impacts of this ice loss. More open water in summer is contributing to increased wave action and coastal erosion. Marine mammals such as the polar bear that depend on sea ice are at increasing risk. Sea ice loss is contributing to amplified warming at the surface and in the lower troposphere, which may accelerate Arctic change. These potential impacts include accelerated permafrost degradation in surrounding land areas, and enhanced melting of Arctic glaciers and the Greenland ice sheet. This talk summarizes our current understanding of the processes of Arctic sea ice loss, observed impacts on the Arctic environment, and the outlook for coming decades.