High temperatures and extensive melting across the Greenland ice sheet (GIS) in summer 2012 had a lasting impact on weather conditions across the ice sheet well into the winter season. Temperatures were 2˚C to 3.5˚C warmer than the 1981-2010 average for coastal areas of GIS during the 2012 winter. The combination of pre-existing meltwater and anomalously high air temperatures resulted in a number of unusual events for the 2012-2013 winter.

In mid-December, liquid water was detected via passive microwave satellite data at up to 5 m depth in the snow cover of GIS. This meltwater was a remnant of the intense melt events of summer 2012. Buried and insulated by snowfall, the liquid water had not completely frozen, and was contributing to the warming of the uppermost layers of snow. Before an algorithm/product recalibration at the National Snow and Ice Data Center (NSIDC), these snow temperatures appeared on satellite data as melt events. However, air temperatures in the area were not high enough to induce melting. Local automatic weather station (AWS) data indicated only one instance of air temperatures above 0˚C from early December through mid-March. Annual algorithm recalibrations are necessary, but recalibration so early in the year is exceptional.

Additionally, snowfall over some eastern parts of GIS was exceptionally low in winter 2012 and spring 2013. The stark lack of snow cover is likely a consequence of above-average temperatures, caused in part by a negative North Atlantic Oscillation (NAO). The resulting increased area of dark ice with a lowered albedo should contribute to severe melt events on GIS once again this summer.

Brown contours indicate less than average precipitation. Blue contours indicate unusually “wet” snow areas.
True-color image from NASA’s MODIS product of southern Greenland. White areas indicate snow cover, while the dark grey color indicates dark ice or bare ground.

Additional Information:

Meltfactor.org

NSIDC