Melting in Greenland sets new record before end of melting season

Map of the 2012 anomaly of the number of melting days with respect to the 1980 – 1999 average (e.g., red color indicates areas where melting lasted up to 50 days above the 1980 – 1999 mean). Updated through August 8, 2012. Via
A supraglacial lake – that is, a lake occurring at the surface of a glacier – in the Kangerlussuaq area of Greenland in 2012. By early August 2012, Greenland melting had exceeded the previous record, set in 2010 later in the melting season.

Scientists are now calling 2012 a “Goliath” year for Greenland melting. Earlier this summer, NASA reported that, by July 12, 2012, 97% of Greenland’s surface was experiencing thaw (that’s in contrast to only 55% of surface thaw as the maximum seen by satellites in the past three decades). By early August, the story had progressed further. On August 15, Earth scientist Marco Tedesco of the Cryosphere Processes Laboratory at City College of New York reported at his website that:

… the cumulative melting index over the entire Greenland ice sheet (defined as the number of days when melting occurs times the area subject to melting) on August 8 exceeded the record value recently set in 2010 for the whole melting season (which usually ends around the beginning or mid September).

In other words, by August 8, 2012, Greenland had experienced more melting than in the entire melting season of 2010, which previously held the record for the greatest amount of Greenland melting in one year.

The map above, right, shows that the extensive melting occurring all over Greenland, especially at high elevations. There, melting in Greenland lasted up to 50-60 days longer than the average this year. In other words, some of the areas at high elevations in south Greenland are generally subject to a few days of melting (if it happens at all). In 2012, they underwent melting for more than 2 months (so far).

Melting was extreme also in the west, northwest and northeast regions, Tedesco reported. Along the southwest coast melting does not appear to have been extreme.

At his website, Tedesco also explained how is this new record for Greenland melting is different from the one that happened in mid-July of 2012. He said:

The extreme melting detected at high elevations in mid-July (covering ~ 97 % of the Greenland ice sheet) generated liquid water that refroze after a few days, changing the physical properties of the snowpack but very likely not contributing to the meltwater that run offs from the ice and can potentially contribute to sea level rise. The event was exceptional in the sense that it is a rare event (imagine a postcard of Rio de Janeiro under a thin layer of snow !) …

The record set by the overall melting has implications on the meltwater that goes into the ocean … Also, the increased melting at higher elevations might remove the seasonal snow and expose more bare ice. The removal of bare ice (which is darker and the absorb more solar radiation and it is therefore more prone to melting than snow), is actually contributing to the net mass loss of Greenland. Seasonal snow is indeed part of the annual cycle (water from the ocean goes into the atmosphere which turns into cloud and it is released as snow which melts again and goes back to the ocean) where ice has been sitting there for decades or hundreds (and more) of years and it is therefore adding new ‘material’ to the cycle (e.g., the ocean).

You can read Ted Tedesco’s blog for yourself here: 2012 The Goliath melting year

Bottom line: By August 8, 2012, Greenland had experienced more melting than in the entire melting season of 2010, which previously held the record for the greatest amount of Greenland melting in one year.

August 30, 2012

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