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Cause of Last Year's Record Surface Melt on Greenland

June 21, 2013; 9:31 AM ET

The record surface melting that took place on the Greenland Ice Sheet back on July 11, 2012 was mostly caused by highly unusual atmospheric circulation and jet stream changes, according to a University of Sheffield research team led by professor Edward Hanna.

The team also determined that ocean temperatures and the lack of Arctic sea ice cover were relatively unimportant factors in causing the extra Greenland melt, according to the University of Sheffield News.

Hanna and his team used computer model simulation, weather station observations and satellite data to confirm this extreme event in which 90 percent of the Greenland Ice Sheet surface experienced some melting. The previous record was much lower at 52 percent back in 2010.

Key excerpts from the University of Sheffield report......

"Our research found that a ‘heat dome' of warm southerly winds over the ice sheet led to widespread surface melting. These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models. According to our current understanding, the unusual atmospheric circulation and consequent warm conditions of summer 2012 do not appear to be climatically representative of future ‘average' summers predicted later this century.

"Taken together, our present results strongly suggest that the main forcing of the extreme GrIS surface melt in July 2012 was atmospheric, linked with changes in the summer North Atlantic Oscillation (NAO), Greenland Blocking Index (GBI, a high pressure system centred over Greenland) and polar jet stream which favoured southerly warm air advection along the western coast.

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