Some new insight into how the Greenland Ice Sheet is melting in response to climate change, from the City College of New York: Research from CCNY's Cryospheric Processes Laboratory has discovered that extreme melting of the ice sheet can continue even when the region doesn't experience record-high temperatures -- all that is required is warmer temperatures.
CCNY's data found that melting of the Greenland Ice Sheet in 2011 was the third greatest since 1979, with only 2010 and 2007 showing more melting. Overall, June to August 2011 saw melting which was "well above" average for 1979-2010. In terms of the amount of snow gained versus melted over the past year, the mass balance, 2011's melting tied the record set in 2010.
As for why this is happening, the research shows that temperature and albedo led the way:
"Albedo" describes the amount of solar energy absorbed by the surface... A white blanket of snow reflects much of the sun's energy and thus has a high albedo. Bare ice, being darker and absorbing more light and energy, has a lower albedo. [...] Absorbing more energy from the sun also means that darker patches warm up faster, just like the blacktop of a road in the summer. The more they warm, the faster they melt. [...] A year that follows one with record high temperatures can have more dark ice just below the surface, ready to warm and melt as soon as temperatures begin to rise. This also explains why more ice sheet melting can occur even though temperatures did not break records.
Prof. Marco Tedesco explains that falling snow slows the process by covering darker ice with a more reflective layer, but snowfall this year was not enough to compensate for past melting.
Here's the original research: Year 2011 Greenland melting remains well above the (1979-2010) average; close-to-record mass loss