Changes in the speed that ice travels in more than 200 outlet
glaciers indicates that Greenland’s contribution to rising sea
level in the 21st century might be significantly less than the
upper limits some scientists thought possible, a new study
shows. “So far, on average we’re seeing about a 30 percent
speedup in 10 years,” said Twila Moon, a University of
Washington doctoral student in Earth and space sciences and lead
author of a paper documenting the observations published May 4
in Science. The faster the glaciers move, the more ice and
meltwater they release into the ocean. In a previous study,
scientists trying to understand the contribution of melting ice
to rising sea level in a warming world considered a scenario in
which the Greenland glaciers would double their velocity between
2000 and 2010 and then stabilize at the higher speed, and
another scenario in which the speeds would increase tenfold and
then stabilize. At the lower rate, Greenland ice would
contribute about four inches to rising sea lev