Increasingly Rapid Greenhouse Effect?

ByABC News
February 16, 2006, 11:31 AM

Feb. 16, 2006 — -- The hulking southern glaciers of Greenland are melting rapidly -- at a rate quicker than previously thought.

In only five years, the amount of freshwater the melting glaciers have dumped into the Atlantic has nearly doubled, which has caused many scientists to conclude that current projections of how fast sea levels will rise have been too low.

The melting glaciers, moving quickly across the ocean, may account for about 17 percent of the estimated one-10th of an inch annual rise in sea levels, according to a study released today by Eric Rignot, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and his co-author, Pannir Kanagaratnam, of the University of Kansas.

An increase in surface air temperatures appears to be causing the glaciers to flow faster -- at up to 8 to 9 miles a year at their fastest clip. They have also been dumping increased volumes of ice into the Atlantic.

"The behavior of the glaciers that dump ice into the sea is the most important aspect of understanding how an ice sheet will evolve in a changing climate," Rignot told The Associated Press. "It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes."

That stepped-up flow accounted for about two-thirds of the net 54 cubic miles of ice Greenland lost in 2005. That compares with 22 cubic miles lost in 1996, Rignot said.

Details of the study were presented Thursday at the annual meeting of the American Association for the Advancement of Science. The study appears Friday in the journal Science.

The increased rise in sea level could have possible runaway effects that could produce a dramatic rise in sea levels, potentially making storm damage far worse, by the time today's toddlers reach middle age, some scientists predict.

Scientists also worry about the effect all this fresh-melt water will have on the Atlantic's Gulf Stream "conveyor belt" currents. These currents have long kept the northeastern United States, Britain and northwestern Europe relatively warm for their northern latitudes by transporting heat up from the tropics. Too much freshwater slows these currents, said scientists.