Beginning in 1991, every summer NASA has measured the ice sheets of Greenland. Past data indicates significant thinning of ice along the coast. Meanwhile some ice sheets have thickened in Greenland's interior. Overall, there's much less ice on Greenland's surface than there was 100 years ago.
This summer's NASA expedition to Greenland has returned with fresh data. Now the analysis begins. One piece of equipment used is an ice-penetrating radar that can find bedrock up to 2 miles below the ice surface. NASA estimates an average drop of 9 inches in the height of Greenland's glaciers would result in a 0.12-inch rise in global sea levels.