First there was ‘unprecedented melting’ in 2005, then came the new Greenland melting record of 2010 – again to be broken this year, during the hot July of 2012, NASA images show.

Image shows extreme melting event on July 12 2012. Light pink is ice sheet area ‘where at least one satellite’ witnessed evidence of thawing, dark pink where multiple satellites spotted ice melting. Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory.

Never before in the 30-year satellite record has such extensive ice sheet melting been witnessed from space. On average no more than half of the ice sheet surface used to experience surface thawing at the peak of the boreal summer.

This extreme melt event coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland, NASA states.

The ridge was one of a series that has dominated Greenland’s weather since the end of May. “Each successive ridge has been stronger than the previous one,” said Thomas Mote, a climatologist at the University of Georgia. This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later. In that period ice sheet surface melting increased from 40 to 97 percent. By July 16, the ridge of warm air had begun to dissipate.

Although the surface of the Greenland ice sheet can react rapidly to day-to-day weather changes, the melting of the volume of ice below is actually an inert process – driven by climatic changes instead of single meteorological events. But here the news is even worse than any hot summer can be. In fact, the Greenland ice sheet is already gone – we learned from a Nature Climate Change publication last spring.

© Rolf Schuttenhelm | www.bitsofscience.org