January 21, 2011

Greenland Lost Record Amounts Of Ice In 2010

Scientists reported on Friday that Greenland's icesheet shed a record amount of melted snow and ice in 2010.

The study found that the 2010 runoff was twice the average annual loss in Greenland over the previous three decades, surpassing a record set in 2007.

According to the paper, ice melt has now topped this benchmark every year since 1996.

Greenland's icesheet could drive up ocean levels by about 23 feet if it melted, drowning coastal cities around the world.

No credible projections today include a doomsday scenario for the coming centuries.  However, recent research suggest that Greenland will contribute more to rising seas than predicted only a few years ago.

Lead researcher Marco Tedesco, who heads the Cryosphere Processes Laboratory at the City College of New York, estimates that runoff in 2010 was 530 gigatons, compared to an average of 274 gigatons for the period 1958-2009.

"The process is far from being linear, and it is not possible to simply draw a line" into the future, Tedesco told the AFP news agency.

However, he said in an email exchange with AFP that over the last 30 years "there has been an increase in runoff."

Researchers have thrown up different figures for how much Greenland is shedding its icy mantle, which is up to 1.7 miles thick in places.

They found that climate change is largely to blame and temperatures in the Arctic region have risen at two or three times the global average over the last 40 years.

Summer temperatures in 2010 were 5.4 degrees Fahrenheit above average.

"The capital, Nuuk, had the warmest spring and summer since records began in 1873," Tedesco noted.

The U.N.'s World Meteorological Organization (WMO) said on Thursday that the year was also the warmest ever recorded, as was the decade it brought to a close.

The new study, which was published in the U.S.-based journal Environmental Research Letters, focused on surface melt, runoff and the number of days when bare ice, free of snow, is exposed to the Sun's radiative force.

In 2010, "melting in some areas stretched up to 50 days longer than average," Tedesco said.

The study showed that land area where melting has been observed has been increasing at a rate of about 6,500 square miles per year.

Not only does melting snow and ice flow directly into the sea, they also form torrential under-ice streams that lubricate the passage of glaciers toward the ocean.

Tedesco said that in assessing the icesheet's total mass low, melt is only part of the picture.

"Our calculations do not account for losses due to calving" -- the splitting of large chunks of glacier ice into the sea -- "and ice dynamics, which are as big if not bigger than those due to surface melting," he said.

He said they did not factor in cyclical contributions to the icesheet from snowfall.

Current estimates of the Greenland icesheet's net mass loss vary between 130 and 250 gigatons per year.

Antarctica is the world's biggest source of land ice after Greenland, but is considered more resistant to any doomsday collapse.

Experts say today that Greenland could contribute as much as 20 inches to average global sea levels by century's end.

This would double the predictions for overall sea-level rise in the U.N. climate panel's landmark 2007 report, which factored in glacial runoff and the thermal expansion of the sea, but not the loss of mass from Greenland.

A 3.25 feet increase in the global watermark would devastate many island nations, and wreak havoc in heavily-populated delta regions across the planet.


Image Caption: Detail of a supraglacial lake from the above picture. Note the streams feeding the lake and the darker area at the bottom. This could be cryoconite, a dark mixture of soot, sediments and organic matter. Credit: Marco Tedesco


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