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.
“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.