In the past, the bright surface of the Greenland Ice Sheet reflected well over half of the sunlight that fell on it. This reflectiveness helped keep the ice sheet stable, as less absorbed sunlight meant less heating and melting. In the past decade, however, satellites have observed a decrease in Greenland’s reflectiveness. This darker surface now absorbs more sunlight, which accelerates melting.
The map above shows the difference between the amount of sunlight Greenland reflected in the summer of 2011 versus the average percent it reflected between 2000 to 2006. Virtually the entire ice sheet shows some change, with some areas reflecting close to 20 percent less light than a decade ago. The map is based on observations from the Moderate Resolution Imaging Spectroradiometer
(MODIS) instruments on NASA’s
Terra and
Aqua satellites. It was produced as part of the National Oceanic and Atmospheric Administration’s
Arctic Report Card.
Climate scientists have long expected that Earth’s polar regions will become less reflective as global temperatures rise. Rising temperatures melt snow and ice, and the uncovered terrain—water, vegetation, bare ground—is darker and absorbs more sunlight. The loss of reflectiveness then
amplifies the initial warming.
