Thomas Mote and colleagues measure meltwater runoff from the ice sheet margin in Greenland. Courtesy of Thomas Mote/University of Georgia.
THE LOSS OF ARCTIC SEA ICE may be driving conditions that favor more rapid melting of surface ice in Greenland, creating a positive feedback, according to a recent study in the Journal of Climate. The findings come as Arctic sea ice levels hit new lows.
A team of atmospheric and climate scientists analyzed existing data and compared it to independent simulations of atmospheric conditions and sea ice levels. Lower levels of sea ice in the Arctic were linked to increased melting of Greenland’s surface ice.
The researchers found that as Arctic sea ice melts, releasing more moisture into the region, it creates high-pressure systems that push warm, moist air down across the Greenland ice sheet. The warm air melts surface ice there in a kind of climate domino effect.
“This year’s low sea ice extent and high Greenland ice sheet surface melt we have seen so far are correlated,” study co-author Jiping Liu told me. “If this year’s Arctic sea ice is at record low levels, we may see higher percentages of surface melting than previously observed.”
The Greenland ice sheet is melting at a record pace. Below, the map on the left shows (in red) the areas where melting occurred on June 12. The graph on the right shows the abnormally high – and early – percentage of Greenland surface ice melt in 2016 (red line) compared to the monthly average from 1981-2010 (blue line).
These findings match an analysis of satellite data that found that the Greenland and Antarctic ice sheets are dumping ice into the oceans at a record pace of 500 million cubic tons this year.
This spring and summer in Greenland has been warm, with temperatures climbing above freezing early. And the ice sheet’s “melt season” started nearly two months early. If the researchers’ findings in the Journal of Climate study are correct, both events may be linked to the record-setting declines in Arctic sea ice.
“Temperature variations over Greenland can be influenced by variations of the North Atlantic Oscillation (NAO),” said Dr. Liu. “We have seen moderate negative NAO this late spring and early summer, which may also contribute to this year’s early and rapid surface melting.”
“It is imperative for climate models to realistically simulate the positive feedback between the decreasing Arctic sea ice and expanding surface melt over the Greenland ice sheet,” he said.