There is evidence that the ice covering much of Greenland is melting at an increasing rate and is on track to disappear entirely if temperatures rise 2 degrees Celsius, leading to a sea level rise of as much as one meter across the planet by the end of the 21st century, researchers said during a recent briefing for the congressional Select Committee on Energy Independence and Climate Change.
At the briefing arranged by committee Chairman Edward Markey (D-Mass.), speakers said that the understanding of the melting of ice that sits atop land masses has grown since the release of the Intergovernmental Panel on Climate Change's last synthesis assessment report in 2007. The increased understanding has led scientists to predict that the climate-change-related sea level rise will be larger than the IPCC suggested.
The briefing was held five days after scientists reported that a 100-square-mile ice sheet broke off from Greenland . "This giant ice island is more than four times the size of Manhattan . It is the largest piece of Arctic ice to break free in nearly half a century," Markey said.
Robert Bindschadler, a senior research scientist at the National Aeronautics and Space Administration, said the melting of ice sheets would likely speed up over time. A range of factors contributes to the ice melt, including rising ocean temperatures, and the breakage of the ice shelf would only serve to speed up the melting, he said.
"Glaciers always speed up when ice shelves break off in front of them, so that's an expected consequence. And, of course, that's going to increase the drainage of the Greenland ice sheet and contribute to rising sea level," he said.
Including melting ice sheets in estimates of future sea level rise — something that the 2007 IPCC report did not do for lack of data — indicates that sea levels could rise by a meter or more by the end of the century, Bindschadler said. Such a rise would affect "hundreds of millions" of people, he said.
Richard Alley, a professor of geosciences and earth and environmental systems at Pennsylvania State University, said that warming above 2 degrees could eventually lead to the disappearance of Greenland's entire ice sheet, which in turn would lead to even more dramatic sea level rise.
"We don't believe that you can lose an ice sheet in mere decades.… It would be at least centuries to melt a whole ice sheet. But what we do find … is it's easier to get rid of an ice sheet than it is to grow it back," Alley said. But actions taken over upcoming decades might set an irreversible path for a disappearing ice sheet.
