Cryosphere 9, 2163–2181 (2015)

Credit: © JOHN GILBEY / ALAMY STOCK PHOTO

The Greenland ice sheet, the largest Northern Hemisphere store of fresh water, is at risk as temperatures increase. Surface melt and the subsequent runoff into the ocean will cause sea level to rise. However, the amount of melt that actually leaves the ice sheet is unknown, as it can filter through the porous compacted snow on the surface and refreeze — at least until that space is filled.

Charalapos Charalampidis of the Geological Survey of Denmark and Greenland, Copenhagen, and co-workers use in situ measurements from the Kagerlussauq region of West Greenland to investigate changes in the glacier volume (known as surface mass balance, SMB) and meltwater runoff for 2009–2013. Data from 7 automatic weather stations and 9 SMB stakes reveals that although both 2010 and 2012 were 'warm' years, 2012 experienced a greater SMB loss and melt runoff. Meltwater on the ice surface also lowered the reflectivity, resulting in the absorption of 28% more solar energy than average. The authors explain the higher runoff in 2012 as a result of limited storage available in the surface snow, because of low snowfall in the region and the space having previously been filled.