Melt along the southern edge of Greenland's ice sheet is now moving up its northwest coast, a new study shows.
"The ice mass loss has been very dramatic" since 2005, John Wahr, study co-author and a University of Colorado at Boulder physics professor, said in a statement.
The team, led by Denmark's National Space Institute, compared data from a NASA climate satellite known as GRACE with GPS measurements from the coastal edges of the ice sheet.
"These changes on the Greenland ice sheet are happening fast, and we are definitely losing more ice mass than we had anticipated," added co-author Isabella Velicogna of the University of California-Irvine, who is also a scientist at NASA's Jet Propulsion Laboratory.
"We also are seeing this ice mass loss trend in Antarctica, a sign that warming temperatures really are having an effect on ice in Earth's cold regions," she said.
Air temperatures over Greenland have increased by about 4 degrees Fahrenheit in the last decade. Parts of Antarctica have seen similar increases.
GRACE's resolution is not precise enough to pinpoint the ice loss source, the researchers said, but the fact that it is along the coast suggests glaciers there are flowing faster into the sea.
"Our speculation is that some of the big glaciers in this region are sliding downhill faster and dumping more ice in the ocean," Wahr said.
A 2009 study found that the Greenland ice sheet shed roughly 385 cubic miles of ice over the previous seven years. The mass loss is equivalent to about .02 inches of global sea-level rise per year.
"If this activity in northwest Greenland continues and really accelerates some of the major glaciers in the area — like the Humboldt Glacier and the Peterman Glacier — Greenland's total ice loss could easily be increased by an additional 50 to 100 cubic kilometers (12 to 24 cubic miles) within a few years," said lead author Shfaqat Abbas Khan.
Greenland's massive ice sheet holds about 20 percent of the world's ice. A complete melt, which no one expects, would raise sea levels by 21 feet.
The study, funded by NASA and the National Science Foundation, will appear in the peer-reviewed Geophysical Research Letters.
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