Dangling below the Arctic Circle, the ice sheet on Greenland is a vestige of the last ice age. Other ice sheets at its latitude have long since dwindled away, but the Greenland Ice Sheet persists, preserved largely because of its own tremendous size. But change is creeping over the ice sheet: glaciers on its edges are sliding into the Atlantic at an accelerating rate and pools of water puddle on the surface of the ice as the summer melt lengthens. Piece by piece, evidence has accumulated to show that the ice sheet is shrinking.
One such piece of evidence comes from the Defense Meteorological Satellites Program (DMSP-F13) Special Sensor Microwave/Imager (SSM/I), which records microwave energy emitted from the Earth’s surface. Because wet snow and dry snow look different in the microwave frequencies, measurements from the SSM/I tell scientists where and when the ice sheet is melting. Made from SSM/I data, this image compares the number of days melting occurred on the Greenland Ice Sheet in 2005 to the annual average number of melting days since 1988. Greenland is nearly entirely ringed in red and orange, showing that the summer melt season was much longer than average in 2005. Some regions, depicted in dark red, experienced up to 20 more melt days than average. No part of the ice sheet melted less than average.