Arctic Ice Melting at Record Rate
By Cat Lazaroff
WASHINGTON, DC, December 9, 2002 (ENS) - More ice melted from the surface of the Greenland Ice Sheet this year than ever before recorded, report scientists from the University of Colorado. The same team found that the extent of Arctic sea ice reached the lowest level in the satellite record in 2002, offering further evidence that climate change is already altering the Arctic.
"Since the season also was characterized by very stormy conditions, we believe these two factors contributed to extensive melt and break up of the icepack," said UC research associate Mark Serreze.
The 2002 sea ice record is the most recent evidence of a downward trend in Arctic sea ice in the decades since satellite monitoring began, said Serreze, a researcher at CIRES' National Snow and Ice Data Center (NSIDC), and lead author on a report about sea ice extent and area in the Arctic.
"It is likely that sea ice extent will continue to decline over the 21st century as the climate warms," Serreze added. "With these trends, we may see an approximate 20 percent reduction in the annual mean sea ice by 2050, and by then we might be approaching no ice at all during the summer months."
The report was released on Saturday at the annual fall meeting of the American Geophysical Union, just one week after an announcement by the National Aeronautics and Space Administration (NASA) that sea ice is melting about nine percent faster than prior research had indicated, and could vanish entirely by the end of this century.
"This trend of disappearing arctic sea ice is one example of the environmental damage that can be linked to carbon dioxide emissions," said Morgan. "When we have the means to reduce CO2 emissions and prevent further damage, inaction is irresponsible. National leaders must act now to implement energy efficiency measures and increase the use of renewable energy sources, like wind and solar, before it's too late."
The burning of coal and other fuels emits carbon dioxide (CO2) and other gases that blanket the earth, trap in heat and cause global warming. According to the Intergovernmental Panel on Climate Change (IPCC), climate change in the polar region is expected to be the greatest of anywhere on Earth.
The new reports from NASA and the University of Colorado suggest that sea ice is retreating even faster than suggested by the WWF report in May. Satellite monitoring by NSIDC led to the discovery of the record sea ice retreat, said UC research associate Julienne Stroeve.
"We saw an unusually pronounced loss of ice in the Beaufort, Chukchi, East Siberian and Laptev Seas," Stroeve said, noting the ice extent in September 2002 was about two million square miles compared to the long term average of about 2.4 million square miles.
Preliminary measurements from the Greenland Ice Sheet show the melt extent of 265,000 square miles, a new record, underscoring the unusual warming there and surpassing the maximum melt extent from the past 24 years by more than nine percent, said CIRES climatologist Konrad Steffen.
Steffen's analyses with graduate student Russel Huff show a higher melting trend since 1979 that appears to have been interrupted just once, in 1991, when the Philippines' Mt. Pinatubo erupted.
The melting ice could lead to even faster warming, said NSIDC's Scambos. Both sea ice and glacier ice cool Earth, reflecting about 80 percent of springtime solar radiation and 40 percent to 50 percent during summer snowmelt.
In winter, ice cover slows heat loss from warmer ocean water to the cold atmosphere. Without large sea ice masses at the poles to moderate the global energy balance, warming escalates, Scambos explained.
CU scientists estimate that a change in the Greenland climate toward warmer conditions would lead to an increase in the rate of sea level rise, due largely to the response of the large ice sheet and not so much to the surface melting.
Melt water has also been shown to affect the rate of ice flow off Greenland directly, penetrating the ice sheet and causing the glaciers to accelerate in speed as they slide over a thin film of melt water.
The melting of sea ice, along with runoff from the Greenland Ice Sheet, could impact deep water convection in the North Atlantic, altering global ocean circulation and climate, said the UC's Serreze.
"In other studies, changes in the North Atlantic circulation have been implicated in starting and stopping Northern Hemisphere ice ages," he added.