Satellites study Greenland ice shrinkage

AUSTIN, Texas, Oct. 7 (UPI) -- U.S. and Dutch scientists say they've developed a method of accurately determining the precise extent of Greenland's shrinking ice cap.

Researchers from the U.S. Center for Space Research in Austin, Texas, and the Delft University of Technology in the Netherlands say they estimate Greenland is accountable for a half-millimeter rise in the global sea level per year.

The research is based on data from the German-American GRACE (Gravity Recovery and Climate Experiment) satellites. Those are two satellites that have been orbiting the Earth behind each other since mid-2002.

The scientists said deviations in the Earth's gravitational field cause fluctuations in the distance between the satellites, which is measured to a precision of 1 millionth of a meter. Since gravity is directly related to mass, the data can be used to plot changes in the planet's water balance, such as the disappearance of the ice caps. The researchers said the data are ideal for measuring areas such as Greenland, where extreme weather conditions make local measurements very difficult.

The findings are reported in the journal Geophysical Research Letters.