Arctic warming at an accelerating rate and could be ice-free by 2013
The Arctic has always experienced cooling and warming, but the current melt defies any historical comparison. It is dramatic, abrupt, and directly correlated with industrial emissions of greenhouse gases. In Alaska and western Canada, average winter temperatures have increased by as much as seven degrees Fahrenheit in the past 60 years. The results of global warming in the Arctic are far more dramatic than elsewhere due to the sharper angle at which the sun's rays strike the polar region during summer and because the retreating sea ice is turning into open water, which absorbs far more solar radiation. This dynamic is creating a vicious melting cycle known as the ice-albedo feedback loop.
Each new summer breaks the previous year's record. Between 2004 and 2005, the Arctic lost 14 percent of its perennial ice -- the dense, thick ice that is the main obstacle to shipping. In the last 23 years, 41 percent of this hard, multiyear ice has vanished. The decomposition of this ice means that the Arctic will become like the Baltic Sea, covered by only a thin layer of seasonal ice in the winter and therefore fully navigable year-round. A few years ago, leading supercomputer climate models predicted that there would be an ice-free Arctic during the summer by the end of the century. But given the current pace of retreat, trans-Arctic voyages could conceivably be possible within the next five to ten years. The most advanced models presented at the 2007 meeting of the American Geophysical Union anticipated an ice-free Arctic in the summer as early as 2013.