Sep 24, 2009 4:19 PM by MSNBC
The most detailed satellite information available shows that ice sheets in Greenland and western Antarctica are shrinking faster than scientists thought and in some places are already in runaway melt mode, a new study found.
"Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized," researchers wrote in the paper published online Wednesday in the peer-reviewed journal Nature.
Using 50 million laser readings from a NASA satellite, scientists for the first time calculated changes in the height of the vulnerable but massive ice sheets and found them especially worse at their edges. That's where warmer water eats away from below. In some parts of Antarctica, ice sheets have been losing 30 feet a year in thickness since 2003, according to the study.
Some of those areas are about a mile thick, so they've still got plenty of ice to burn through. But the drop in thickness is speeding up. In parts of Antarctica, the yearly rate of thinning from 2003 to 2007 is 50 percent higher than it was from 1995 to 2003.
These new measurements confirm what some of the more pessimistic scientists thought: The melting along the crucial edges of the two major ice sheets is accelerating and is in a self-feeding loop. The more the ice melts, the more water surrounds and eats away at the remaining ice.