The almost complete melting of Greenland’s ice sheet surface on July 11-12 2012 was caused by climate processes not projected by models. That’s according to an international team led by Edward Hanna from the University of Sheffield, UK that has looked at what might have driven the melt. “The models used to predict future climate change are clearly deficient in simulating some of the recent jet stream changes that we have shown to be responsible for enhanced warming and ice melt over Greenland,” Edward told me. And the world needs to pay attention when Greenland defrosts, as the water it produces is a major part of sea level rise.
Having long studied the Greenland ice sheet, or GrIS, Edward was perhaps one of the people least amazed by 2012’s events. “Last year’s record melt was a bit of a surprise, but perhaps not so startling in retrospect, given strong recent warming of the ice sheet area since the early-mid 1990s,” he said. With other scientists he has also found a clear change since 2007 in early summer Arctic wind patterns relative to previous decades that has led to warm Greenland summers. In particular, jet stream patterns of winds weaving north and south in drunken circles around the pole have changed to drive warm winds over Greenland. That study also linked these changes to cool, wet summers in the UK since 2007, whose unusual wetness in 2012 is seemingly the other face of the GrIS melt coin. Read the rest of this entry »