[meteorite-list] NASA Selects Material for Orion Spacecraft Heat Shield

[Ron Baalke]

April 06, 2009

Steve Cole 
Headquarters, Washington 
202-358-0918 
stephen.e.cole at nasa.gov 

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

RELEASE: 09-079

SATELLITES SHOW ARCTIC LITERALLY ON THIN ICE

WASHINGTON -- 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 5.85 million square miles. That is 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 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. 

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 
	
-end-