The historic loss of sea ice seen in the Arctic in recent years is tied to widespread warming in the polar region that is increasing at a rate of more than 2 degrees per decade, according to a NASA satellite study released Thursday.
Last year, the summer ice that normally clogs Arctic seas was at historically low levels. This summer, the ice remained at near record lows, and the Arctic's largest ice shelf cracked apart.
Researchers have suspected the loss of ice was due to warmer temperatures but had only spotty measurements on which to base their conclusions.
The new study, which will be published Nov. 1 in the Journal of Climate, used a polar-orbiting satellite from the National Oceanic and Atmospheric Administration to measure surface temperatures throughout the Arctic.
The study found temperatures over sea ice have been gradually rising over the last 100 years. But in the last 20 years, the temperatures have been rising eight times faster.
"The Arctic is in the process of being transformed," said Josefino Comiso, the researcher at NASA's Goddard Space Flight Center in Greenbelt, Md., who conducted the study.
In another study last year, Comiso reported that the Arctic's usually thick, year-round sea ice was disappearing at a rate of 9% per decade.
Earlier reports from submarine data showed that Arctic ice in the 1990s was about 3 feet thinner than it had been decades before.
The new satellite data revealed that Arctic warming is not consistent. Although the area near Alaska and western Canada has warmed, the area around Greenland has cooled slightly. Still, the warming has created much more open water in the Arctic in recent years.
The new study is one of a number of reports -- from scientists, Inuit natives, boat captains and Cold War submarine records -- suggesting that the Arctic is changing in dramatic ways. But because much of the area is inaccessible, it has been difficult for scientists to get a large-scale picture of the changes, said Waleed Abdalati, who oversees NASA's polar-monitoring efforts.
Because the changes are so sudden and are likely to have a global impact on weather and crops, NASA is turning considerable satellite resources toward the Earth's polar regions. "With satellite data, we can study the whole area in glorious detail," Comiso said.
Interest in the region is becoming widespread among other government agencies as well.
