Global Warming: The Greenland Factor

From BusinessWeek

So how fast is Greenland melting? To figure that out scientists have been clocking the speed at which ice sheets are sliding to the sea, and have shown that the speed has increased. New research published Apr. 17 in the online journal Science Express explains how this actually occurs. Here's what happens: Big lakes of meltwater form on the surface of the ice in the summer. The pressure from the water then creates cracks in the ice sheet that go all the way down to bedrock, more than half a mile below. The water then gushes down through the ice in a cataclysmic flow rivaling Niagara Falls.

Down at the bedrock, the water actually lifts up the massive ice sheet and acts like grease, doubling the speed of the glaciers' journey over the bedrock to the sea. 'It matters,' says Richard Alley, professor of geosciences at Pennsylvania State University, and an ice-sheet expert: 'It is not 'run for the hills, we are doomed,' but this tells us that loss of the Greenland ice could happen in centuries, not millennia.'