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Friday, January 21, 2011

Marco Tedesco: Greenland ice melt sets a record — and could set the stage for sea level rise

Greenland ice melt sets a record — and could set the stage for sea level rise

by Reuters, January 21, 2011
Photo credit: M. Tedesco (camp by the side of a supraglacial stream leaving a supraglacial lake, Greenland, 2010)
Greenland’s ice sheet melted at a record rate in 2010, and this could be a major contributor to sea level rise in coming decades.
The ice in Greenland melted so much last year that it formed rivers and lakes on top of the vast series of glaciers that covers much of the big Arctic island, with waterfalls flowing through cracks and holes toward the bottom of the ice sheet. Take a look at  video from Marco Tedesco of City College of New York, who is leading a project to study what factors affect ice sheet melting. The photo at left shows a camp by the side of a stream flowing from a lake — all of it on top of the ice sheet.
“This past melt season was exceptional, with melting in some areas stretching up to 50 days longer than average,” Tedesco said in a statement.  “Melting in 2010 started exceptionally early at the end of April and ended quite late in mid- September.”
Summer 2010 temperatures in Greenland were up to 5.4 °F (3 °C) above average, and there was reduced snowfall, Tedesco and his co-authors noted in an article in the current edition of Environmental Research Letters. Nuuk, Greenland’s capital, had the warmest spring and summer since records began there in 1873. Average summer temperatures vary widely, but in coastal areas hover around freezing.
This is in tune with studies released in the last week by the U.S. National Oceanic and Atmospheric Administration and the World Meteorological Organization finding 2010 was tied with 2005 and 1998 for the warmest year since modern global temperature record-keeping began in 1880.
With less snow cover, more bare ice was exposed to the sun, and because bare ice is darker than snow, it absorbs more solar radiation. So the more ice is uncovered, the more warming sunlight it absorbs and the more vulnerable it is to melting. Tedesco said other factors being examined include the impacts of lakes on the glacial surface, dust and soot deposited over the ice sheet.
The study was sponsored by World Wildlife Fund, NASA and the National Science Foundation.
“Sea level rise is expected to top 3 feet by 2100, largely due to melting from ice sheets,” World Wildlife Fund climate specialist Martin Sommerkorn said in a statement. An international assessment of Arctic conditions released in October found warmer air, less sea ice and melting glaciers, and said the region around the North Pole is unlikely to return to its formerly colder conditions any time soon.

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