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Climate scientists find surprising reason for faster Arctic meltdown

In this June 15, 2014 file photo, a polar bear dries off after taking a swim in the Chukchi Sea in Alaska. Scientists say polar ice is melting faster than expected as climate change propels tropical storms further north. (Brian Battaile/U.S. Geological Survey via AP, File)

Relatively few tropical storms ever make it as far north as Greenland, the ice-covered island that straddles the Arctic Circle east of Canada. But the ones that do appear to be inflicting serious damage — and not just to Greenland.

A study published Monday shows that warm, tropical air masses are accelerating the melting of Greenland’s ice sheets, exacerbating a problem that already is contributing to rising sea levels around the globe.
The Greenland Ice Sheet currently covers more than 650,000 square miles, an area three times the size of Texas. Previous studies have documented rapid melting on the periphery of the ice sheet, which is losing mass at a rate 30 percent faster than in the late 1970s.

But the new research shows that tropical systems that hit Greenland in the autumn months cause a sharp spike in thawing. Unusually warm topical air and rainfall melt the surface ice and speed up the movement of glaciers at a time when the Arctic is normally turning colder, according to the new study in the journal Nature GeoScience.

[Why the Earth’s past has scientists so worried about sea level rise.]

“Adding warm water at that time of year causes a lot of melting over a large area,” said Samuel H. Doyle, a glaciologist at Aberyswyth University in Wales and one of 16 scientists who contributed to the study.

The researchers discovered the phenomenon while studying the Greenland Ice Sheet’s response to a week of warm, wet weather that arrived in Greenland with a tropical system in late August 2011. The storm brought “extreme surface runoff” and a “widespread acceleration in ice flow” that extended nearly 90 miles into Greenland’s interior. The scientists compared their data with historical weather patterns and were able to link similar increases in melting to previous bouts of tropical weather.

The findings are important because melting ice in Greenland is currently one of the biggest single contributors to rising sea levels around the globe. If all of Greenland’s ice melts, sea levels will rise by as much as 20 feet, enough to swamp major coastal cities around the world, scientists say.

“The worry is that, with climate change, the predictions are for warmer, wetter weather in the future,” Doyle said.