The rapidly shrinking sea ice cover and ice-albedo feedback effects

Among the most dramatic changes on the Earth’s surface that may be associated with anthropogenic climate change is the rapid decline in the Arctic perennial sea ice cover. In 2007, the perennial ice declined precipitously with its area being 37% lower than climatological average and 28% lower than the previous low established in 2005. In 2008, the perennial ice recovered somewhat because of colder global temperatures but by only about 6% of average value. The trend in the ice area covered by perennial ice is now -12.5% per decade which compared to a previous report of -9% per decade indicates an accelerated decline. Studies of the multiyear ice cover as detected by satellite sensor in winter indicate an even more drastic change. The multiyear ice as detected in winter represents ice that has generally survived two summers and regarded as thicker ice types. Analysis of the thicker multiyear ice types indicates a more rapid decline of 15.5 % per decade. This implies a thinning in the Arctic ice cover as well. Much of the decline occurred in the western region of the Arctic Basin (i.e., Chukchi and Beaufort Seas) where the open water area has been increasing by about 35% per decade. The decline in the sea ice cover causes an increase in low albedo ice free ocean regions that absorb a lot more solar energy than ice covered regions. This causes further decline in the ice cover in a process called ice-albedo feedback. The impact of such process is a warmer mixed layer of the Arctic Ocean. This is consistent with results from analysis of satellite sea surface temperature (SST) data in the region which indicates a warming of 0.52 +/- 0.23 degrees Celsius per decade during the months of August from 1979 to 2008. Results of sensitivity analysis that includes the use of a simple thermodynamic model to assess the net effect of ice-albedo feedback compared to contributions from other factors will be presented.