New studies suggest global warming is having very real impacts on ice in the Earth’s cold regions
By Bob Berwyn
SUMMIT COUNTY — Scientists from Denmark and the University of Colorado say the rate of ice-loss in Greenland is accelerating and moving up the northwest coast of the North Atlantic island.
The researchers made their findings by comparing data from satellites to readings from long-term monitoring stations on bedrock on the edges of the ice sheet.
About 80 percent of Greenland is covered with ice, holding about 20 percent of the world’s ice, or the equivalent of a 21-foot rise in sea level should it all melt. Air temperatures over the Greenland ice sheet have increased by about 4 degrees since 1991, which most scientists attribute to a build-up of greenhouse gases in the atmosphere.
The researchers were able to measure monthly average crustal uplift by using the satellite and ground-based data. As the ice melts, the ground underneath springs back after having been pushed down by the weight of the ice for millennia. In some places, the uplift has been dramatic. Near the Thule Air Base on Greenland’s northwest coast, the crust rose by roughly 1.5 inches in just four years, from October 2005 to August 2009.
The data is not detailed enough to pinpoint the source of the ice loss, but the researchers said their study suggests that the flows of Greenland’s outlet glaciers are speeding up.
“The ice mass loss has been very dramatic along the northwest coast of Greenland,” said CU-Boulder physics Professor and study co-author John Wahr, also a fellow at CU-Boulder’s Cooperative Institute for Research in Environmental Sciences. “This is a phenomenon that was undocumented before this study,” said Wahr. “Our speculation is that some of the big glaciers in this region are sliding downhill faster and dumping more ice in the ocean.”
An earlier study showed that in just seven years, between 2002 and 2009, the Greenland ice sheet shed roughly 385 cubic miles of ice. The mass loss is equivalent to about 0.5 millimeters of global sea-level rise per year.
A 2006 study by Wahr and Velicogna using data from the same the satellite showed that Greenland lost roughly 164 cubic miles of ice from April 2004 to April 2006 — more than the volume of water in Lake Erie.
“These changes on the Greenland ice sheet are happening fast, and we are definitely losing more ice mass than we had anticipated,” said Isabella Velicogna of the University of California-Irvine, who also is 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.”
“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 Khan.
The study was funded by NASA and the National Science Foundation.