Wunderground.com - 4/26/13, Dr. Jeff Masters
Figure 1. Over the course of several years, turbulent water overflow from a large melt lake carved this 60-foot-deep (18.3 meter-deep) canyon in Greenland's Ice Sheet (note people near left edge for scale). Image credit: Ian Joughin, University of Washington
2012: Unprecedented melting in Greenland
Watching the weather events of 2012 over Greenland made all seasoned climate watchers a little queasy. The vast ice sheet on the island holds enough water to raise global sea levels by 7.36 meters (24.15 feet) were it all to melt, and the ice melt season of 2012 gave notice that an epic melting of the Greenland Ice Sheet may be underway. According to NOAA's 2012 Arctic Report Card, the duration of melting at the surface of the ice sheet in summer 2012 was the longest since satellite observations began in 1979, and the total amount of summer melting was nearly double the previous record, set in 2010 (satellite records of melting go back to 1979.) A rare, near-ice sheet-wide surface melt event melted 97% of the surface of Greenland's ice sheet on July 11 - 12. While a similar melt event at the summit occurred 1889, but the 1889 event has no basis in the instrumental record from coastal Greenland. It's instead likely that 2012 was Greenland's warmest summer in at least 863 years, since the medieval warm period (see http://www.meltfactor.org/blog/?p=677 and http://www.meltfactor.org/blog/?p=725). It would not be a surprise if this sort of summer began occurring regularly, since the ice sheet reached its darkest value on record in 2012. The darkened surface was due to below average summer snow, soot particles from pollution and forest fires, and record melting. A darker ice sheet absorbs more solar energy, in a vicious cycle that raises temperatures, melts more ice, and further darkens the ice sheet. The amount of melting that was caused by soot from forest fires is important to know, since global warming is likely to increase the amount of forest fires in coming decades. However, the amount of forest fire soot landing on the Greenland Ice Sheet is almost completely unknown, which is why Dr. Box is determined to find out, via the Dark Snow Project.
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