Satellites Show Arctic Literally on Thin Ice

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Steve Cole 202-358-0918
NASA Headquarters, Washington
Stephen.e.cole@nasa.gov

Jane Beitler 303-492-1497
National Snow and Ice Data Center, Boulder, Colo.
jbeitler@nsidc.org

NEWS RELEASE: 2009-062 April 6, 2009

Satellites Show Arctic Literally on Thin Ice

PASADENA, Calif. – The latest Arctic sea ice data from NASA and the National Snow and Ice
Data Center show that the decade-long trend of shrinking sea ice cover is continuing. New evidence
from satellite observations also shows that the ice cap is thinning as well.

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 University of Colorado, Boulder, scientists
led by Charles Fowler. Thin seasonal ice -- ice that melts and re-freezes every year -- makes up about
70 percent of the Arctic sea ice in wintertime, up from 40 to 50 percent in the 1980s and 1990s.
Thicker ice, which survives two or more years, now comprises just 10 percent of wintertime ice cover,
down from 30 to 40 percent.

According to researchers from the National Snow and Ice Data Center in Boulder, Colo., the
maximum sea ice extent for 2008-09, reached on Feb. 28, was 15.2 million square kilometers (5.85
million square miles). That is 720,000 square kilometers (278,000 square miles) less than the average
extent for 1979 to 2000.

"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 Walter Meier, research scientist at the center and the University of
Colorado, Boulder. "Thickness is important, especially in the winter, because it is the best overall
indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it grows more
vulnerable to melting in the summer."

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 Ron Kwok of NASA's Jet
Propulsion Laboratory in Pasadena, Calif., produced the first map of sea ice thickness over the entire
Arctic basin.

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 Lake Michigan and
Lake Superior combined.

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
1.7 meters (6 feet) in thickness, while ice that had lasted through more than one summer averages
about 3 meters (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.

For more information about Arctic sea ice, visit:
http://www.nasa.gov/topics/earth/features/arctic_thinice.html and
http://nsidc.org/arcticseaicenews .

For more information about NASA and agency programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

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