Scientists use GPS as ice measuring tool

Global positioning systems tracking changes in Greenland ice loss show a surprising link between ice and the atmosphere above it, U.S. scientists say. GPS systems can detect many consequences of climate change, including ice loss, the uplift of bedrock, changes in air pressure -- and perhaps even sea level rise, a team led by Earth scientists at Ohio State University reported. GPS can measure such changes because Earth compresses or expands like a spring depending on the weight above it, allowing scientists to use GPS on the Greenland surface to turn it into a giant bathroom scale to weigh the ice atop it. Measurements revealed Greenland sank by about a quarter of an inch over the winter of 2010, and while the researchers determined that half of the sinking was due to the weight of accumulating ice, surprising, the other half was actually due to high air pressure above the ice. GPS has been used in this manner before but could only detect changes over a period of several years, the researchers said. "Within the next year or so, we should be able to process the GPS data within a month of its being collected," OSU earth scientists Micheal Bevis said, "and then we can monitor abrupt changes in ice mass only a month or two after they occur." "It surprises most meteorologists that there is such a strong seasonal signal in surface pressure in Greenland. But it amazes almost everyone to learn that seasonal changes in air mass push on the bedrock just as strongly as seasonal changes in ice mass. It is highly counter-intuitive, but true!" Bevis said.