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.

sea ice

Sea ice beneath midnight sun in June, in the Bering Sea off St. Matthew Island in Alaska. (Photo WWF-Canon/Kevin Schafer)
Researchers from the University of Colorado (UC) based Cooperative Institute for Research in Environmental Sciences (CIRES), say the accelerated melting appears to be linked to shifts in Northern Hemisphere atmospheric circulation patterns. The study also found temperatures during the summer of 2002 were warmer than usual over much of the Arctic Ocean.

"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.

graphic

Satellite data show the area of the Arctic Ocean covered by sea ice in September 2002. Lower than average concentrations of ice floes appear in blue and higher concentrations in yellow. The lavender line indicates a more typical ice extent, the median for 1988-2000. The white circle at the North Pole is the area not imaged by the satellite sensor. (Graphic courtesy NSIDC)
UC researcher James Maslanik, a coauthor of the study, noted that the 2002 minimum sea ice record in the Arctic is the lowest since the early 1950s and could be the lowest in several centuries.

"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.

melting ice

Bull Seal Bay with melting sea ice in June, St. Matthew Island, Alaska. (Photo WWF-Canon/Kevin Schafer)
The new findings underscore the urgency of steps to reduce human contributions to global warming, said Jennifer Morgan, director of the climate change program at the World Wildlife Fund (WWF).

"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.

polar bears

Polar bears spend much of their lives hunting for seals from sea ice. (Photo Steve Morello, courtesy WWF)
In a report issued earlier this year, WWF described ongoing polar bear research showing how these Arctic mammals depend on annual accumulations of sea ice to hunt seals, a major protion of their diet. In that report, WWF described how as temperatures in the Arctic become warmer - and are remaining warmer for longer periods - the ice free season lengthens, threatening the survival of polar bears and other Arctic wildlife.

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.

seal pup

Many harp seals give birth to pups like this one on floating sea ice. (Photo Steve Morello, courtesy WWF)
"We had a hunch it was setting up to be a record year in August," said Ted Scambos of NSIDC, who has been working in Earth's polar regions. "What we saw really surprised us. Not only was sea ice retreating in nearly every sector, but the interior ice was unusually thin and spread out."

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.

seal

A harp seal pokes its head up through melting sea ice. (Photo Steve Morello, courtesy WWF)
Steffen and Huff found the northern and northeastern portion experienced extreme melting reaching as high as 6,560 feet in elevation, where temperatures are normally too cold for melting to occur. Mount Gunnbjornsfjeld, rising 3,700 meters (12,139 feet) in southeast Greenland, is the highest point in the country.

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.

walrus

Walrus use their tusks to haul themselves onto floating ice, where they can rest, molt, give birth and raise their young. (Photo Steve Morello, courtesy WWF)
"For every degree (F) increase in the mean annual temperature near Greenland, the rate of sea level rise increases by about 10 percent," Steffen said. The oceans are now rising by a little more than half an inch per decade.

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.