Thinner than the 2.3-kilometer-thick center, the outer edges of the Greenland ice sheet develop melt zones like the one shown here during the warm summer months.
Although 2005 overall saw a new record, the extent of June melting in 2005 was unexceptional. The same held true for 2006, when this picture was taken.
The 2011 Greenland melt season was up to 30 days longer than the 1979–2010 average. This color-coded map shows where melt season lasted more or less than average.
On Greenland, tens of thousands of years of snowfall have settled and solidified into a massive sheet of ice. Each summer, snow retreats briefly at low elevations, and a narrow strip of rocky coastline emerges. While some seasonal thawing is typical on Greenland, more dramatic changes are probably in store for the Greenland Ice Sheet in coming decades and centuries.