Greenland's ice is melting so quickly that the land underneath is rising at an accelerated pace, U.S. researchers find.

"It's been known for several years that climate change is contributing to the melting of Greenland's ice sheet," said Tim Dixon, professor of geophysics at the University of Miami Rosenstiel School of Marine and Atmospheric Science (RSMAS).

"What's surprising, and a bit worrisome, is that the ice is melting so fast that we can actually see the land uplift in response," he said in a paper published Tuesday on the online edition of Nature Geoscience.

"Even more surprising, the rise seems to be accelerating, implying that melting is accelerating."

Using specialized global positioning system (GPS) receivers stationed on the rocky shores of Greenland, the scientists looked at data from 1995 onward. The raw GPS data were analyzed for high accuracy position information, as well as the vertical velocity and acceleration of each GPS site.

The measurements are restricted to places where rock is exposed, limiting the study to coastal areas. However, previous data indicate that ice in Greenland's interior is in approximate balance: yearly losses from ice melting and flowing toward the coast are balanced by new snow accumulation, which gradually turns to ice.

Most ice loss occurs at the warmer coast, by melting and iceberg calving and where the GPS data are most sensitive to changes. In western Greenland, the uplift seems to have started in the late 1990s.

"During ice ages and in times of ice accumulation, the ice suppresses the land," explained Shimon Wdowinski, research associate professor at RSMAS, and co-author of the study.

"When the ice melts, the land rebounds upwards," he said. "Our study is consistent with a number of global warming indicators, confirming that ice melt and sea level rise are real and becoming significant."

Melting of Greenland's ice contributes to global sea level rise. If the acceleration of uplift and the implied acceleration of melting continue, Greenland could soon become the largest contributor to global sea level rise, said Yan Jiang, Ph.D. candidate at RSMAS and co-author of the study.

"Greenland's ice melt is very important because it has a big impact on global sea level rise," Jiang said. "We hope that our work reaches the general public and that this information is considered by policy makers."