More Greenland Ice Melting Faster

Sensitive Global Positioning System and other satellite-borne sensors have detected the accelerating northwestern migration of ice loss the length of coastal Greenland since 2005.

Scientists have known for some time that the great ice sheet was losing mass over southeastern portions of Greenland, but a new analysis describes "an on-going northward migration of increasing mass loss" along the western coast from the southern tip to the far north.

The Greenland ice sheet is a vast reservoir, two miles deep in places, containing enough water to fill the Gulf of Mexico -- and to raise sea level 21 feet if it were all to melt.

The new analysis, by an international team led by Shfaqat Abbas Khan of the National Space Institute of Denmark, is published this week in the American Geophysical Union journal Geophysical Research Letters.  The image, courtesy of AGU, shows the averaged rate of mass loss, measured in centimeters of ice thickness, between February 2003 and June 2009.

(Click on the image and watch a video, courtesy of the University of Colorado-Boulder, that shows the evolution of the melting pattern since January 2003.)

The researchers compared two sets of data -- measurements of "crustal uplift" along the coast detected at three long-term GPS sites on coastal bedrock, and direct measurements from the orbiting twin Gravity Recovery and Climate Experiment (GRACE) satellites that detect subtle changes in Earth's gravity field caused by regional changes in the planet's mass.

"When we look at the monthly values from GRACE, the ice mass loss has been very dramatic along the northwest coast of Greenland," said co-author John Wahr, a physicist at University of Colorado-Boulder. "This is a phenomenon that was undocumented before this study. Our speculation is that some of the big glaciers in this region are sliding downhill faster and dumping more ice in the ocean."

Another co-author, geophysicist Isabella Velicogna of NASA's Jet Propulsion Laboratory, said the combination of the GPS and GRACE data "gives us a very powerful tool that improves our resolution and allows us to better understand the changes that are occurring."