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2007-08-17 09:44:34
By Timothy GardnerThu Aug 16, 4:49 PM ET
The extent of Arctic sea ice will likely have melted to a record low this
September partially due to man-made greenhouse gas emissions, researchers at
the University of Colorado said on Thursday.
There is a 92 percent chance that Arctic sea ice extent in September will melt
to its lowest level at least since the 1970s, when satellite measuring efforts
began, the researchers said. They had predicted a 33 percent chance of a record
low in April, but changed the forecast after a rapid disintegration of sea ice
during July.
Such high levels of ice melting could have wide implications in coming years
such as changes in temperature and rain patterns across much of the United
States.
"Similar to the way the El Nino pattern affects weather in the United States,
more ice melt could change rain patterns and temperature patterns in the middle
of the United States, which could have economic impacts on farmers," Sheldon
Drobot, who leads Arctic ice forecasting at CU-Boulder's aerospace engineering
department, said in an interview.
It could also open the Northwest Passage along the northern coast of North
America and connect the Atlantic and Pacific Oceans to shipping by as early as
2020 or 2025, he said. That could be a cheaper option for many shippers than
the Panama Canal.
Whatever the effects, a rise in heat-trapping emissions such as carbon dioxide
is partially responsible, the university said.
"There is an element of human activity in the cause of this melt," said Drobot.
"Natural variations can't explain everything."
High levels of greenhouse emissions from smokestacks and tailpipes have
combined with natural fluctuations, such as an increase in cloud-free days over
the Arctic this summer, to spur the melt, he said.
Arctic sea ice researchers pay particular attention to the months of September
and March because they generally mark the annual minimum and maximum sea ice
extent, respectively. Sea ice extent, the area of an ocean covered by at least
15 percent ice, has been declining at least since the late 1970s.
The CU-Boulder department used satellite data from the U.S. Department of
Defense and temperature records from the National Oceanic and Atmospheric
Administration for the ice forecasts, which it has been producing for five
years.
The record low September minimum for sea ice, set in 2005, is 2.15 million
square miles. For 2007, the highest probability minimum extent is 1.96 million
square miles , and there is a 25 percent chance the low will fall to 1.88
million square miles, Drobot said.
The melt itself can act as a feedback loop and cause ever more melting, because
water has a darker surface than snow. "Water acts like a sponge sucking up a
lot more solar energy," Drobot said.