Satellites Show Arctic Literally on Thin Ice
Arctic sea ice works like an air conditioner for the global climate system. Ice naturally cools air and water masses, plays a key role in ocean circulation, and reflects solar radiation back into space. In recent years, Arctic sea ice has been declining at a surprising rate.
Scientists who track Arctic sea ice cover from space announced today that this winter had the fifth lowest maximum ice extent on record. The six lowest maximum events since satellite monitoring began in 1979 have all occurred in the past six years (2004-2009).
Until recently, the majority of Arctic sea ice survived at least one summer and often several. But things have changed dramatically, according to a team of
According to researchers from the National Snow and Ice Data Center in
“Ice extent is an important measure of the health of the Arctic, but it only gives us a two-dimensional view of the ice cover,” said
The Arctic ice cap grows each winter as the sun sets for several months and intense cold sets in. Some of that ice is naturally pushed out of the Arctic by winds, while much of it melts in place during summer. The thicker, older ice that survives one or more summers is more likely to persist through the next summer.
Sea ice thickness has been hard to measure directly, so scientists have typically used estimates of ice age to approximate its thickness. But last year a team of researchers led by
Using two years of data from NASA’s Ice, Cloud, and land Elevation Satellite (ICESat), Kwok’s team estimated thickness and volume of the Arctic Ocean ice cover for 2005 and 2006. They found that the average winter volume of Arctic sea ice contained enough water to fill
The older, thicker sea ice is declining and is being replaced with newer, thinner ice that is more vulnerable to summer melt, according to Kwok. His team found that seasonal sea ice averages about 6 feet in thickness, while ice that had lasted through more than one summer averages about 9 feet, though it can grow much thicker in some locations near the coast.
Kwok is currently working to extend the ICESat estimate further, from 2003 to 2008, to see how the recent decline in the area covered by sea ice is mirrored in changes in its volume.
“With these new data on both the area and thickness of Arctic sea ice, we will be able to better understand the sensitivity and vulnerability of the ice cover to changes in climate,” Kwok said.
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