Greenland Ice Sheet Melting No Faster than Last Century
The ice sheet, 2-3 km (6,600-9,800 feet) thick, consists of layers of compressed snow built up over at least hundreds of thousands of years. Melting takes place only during Greenland’s late spring and summer, the meltwater running over the ice sheet surface into the ocean, as well as funneling its way down through thick glaciers, helping speed up their flow toward the sea.
In addition to summer melting, the sheet loses ice at its edges from calving or breaking off of icebergs, and from submarine melting by warm seawater. Apart from these losses, a small amount of ice is gained over the long winter from the accumulation of compacted snow at high altitudes in the island’s interior. The net result of all these processes at the end of summer melt in August is illustrated in the adjacent figure, based on NASA satellite data.
The following figure depicts the daily variation, over the past year, of the estimated surface mass balance of the Greenland ice sheet – which includes gains from snowfall and losses from melt runoff, but not sheet edge losses – as well as the mean daily variation for the period from 1981 to 2010. The loss of ice during the summer months of June, July and August is clearly visible, though the summer loss was smaller in 2021 than in many years. An unusual, record-setting gain can also be seen in May 2021.
