Experts say Greenland's ice loss has quadrupled since 2003.
The new research, published in the Proceedings of the National Academy of Sciences, showed that the largest loss of ice since early 2003 to mid-2013 was in southwest Greenland, an area previously not seen as a vital factor in rising sea levels. They are often free from large glaciers.
"We know we have a big problem with high snow levels in some of the big glaciers," said Michael Beavis, lead author of the study and professor of geophysics at Ohio State University.
"But now we realize that there is a second serious problem, with large amounts of ice coming out of the ice, and increasingly, like rivers flowing into the sea," he said.
The melting of the surface glacier, which researchers attributed to global warming, will become a major contributor to rising sea levels in the future.
"The only thing we can do is adapt and mitigate global warming," Bevis said. "We are watching the ice sheet reaching a turning point."
The ice sheet contains enough ice to raise global sea levels by 7 meters.