Has the Arctic Perennial Ice Cover Reached the Tipping Point?

Analysis of satellite data from 1979 to the present has indicated that the Arctic perennial ice cover has been declining at a rapid rate of about 10 percent per decade. The yearly fluctuation was relatively large during the first 20 years but in the last decade, the extent and area of the perennial ice cover have been persistently low. The coverage was a record low in 2002, followed by a slight recovery in 2003 and 2004, another record low in 2005 and a mild recovery in 2006. During the summer of 2007, however, the rate of decline was phenomenal. The extent and area of the ice cover as of 4 September 2007 were 4.5 and 3.9 million square km, respectively, which are considerably less (by 18 to 22 percent) than those of 2005, the corresponding values of which are 5.5 and 5.0 million square km. The large decline suggests that the tipping point for the perennial ice has been reached and a recovery is no longer possible in the foreseeable future. Such hypothesis is supported by studies of the impact of ice-albedo feedback using satellite observed (and in situ) changes in SST (sea surface temperature) in conjunction with a thermodynamic model.