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NASA Leads Study Of Unprecedented Arctic Ozone Loss



Oct. 2, 2011

Steve Cole 
Headquarters, Washington 
202-358-0918 
stephen.e.cole@xxxxxxxx 

Alan Buis 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-0474 
alan.d.buis@xxxxxxxxxxxx 
RELEASE: 11-329

NASA LEADS STUDY OF UNPRECEDENTED ARCTIC OZONE LOSS

WASHINGTON -- A NASA-led study has documented an unprecedented 
depletion of Earth's protective ozone layer above the Arctic last 
winter and spring caused by an unusually prolonged period of 
extremely low temperatures in the stratosphere. 

The study, published online Sunday in the journal Nature, finds the 
amount of ozone destroyed in the Arctic in 2011 was comparable to 
that seen in some years in the Antarctic, where an ozone "hole" has 
formed each spring since the mid 1980s. The stratospheric ozone 
layer, extending from about 10 to 20 miles (15 to 35 kilometers) 
above the surface, protects life on Earth from the sun's harmful 
ultraviolet rays. 

The Antarctic ozone hole forms when extremely cold conditions, common 
in the winter Antarctic stratosphere, trigger reactions that convert 
atmospheric chlorine from human-produced chemicals into forms that 
destroy ozone. The same ozone-loss processes occur each winter in the 
Arctic. However, the generally warmer stratospheric conditions there 
limit the area affected and the time frame during which the chemical 
reactions occur, resulting in far less ozone loss in most years in 
the Arctic than in the Antarctic. 

To investigate the 2011 Arctic ozone loss, scientists from 19 
institutions in nine countries (United States, Germany, The 
Netherlands, Canada, Russia, Finland, Denmark, Japan and Spain) 
analyzed a comprehensive set of measurements. 

These included daily global observations of trace gases and clouds 
from NASA's Aura and CALIPSO spacecraft; ozone measured by 
instrumented balloons; meteorological data and atmospheric models. 
The scientists found that at some altitudes, the cold period in the 
Arctic lasted more than 30 days longer in 2011 than in any previously 
studied Arctic winter, leading to the unprecedented ozone loss. 
Further studies are needed to determine what factors caused the cold 
period to last so long. 

"Day-to-day temperatures in the 2010-11 Arctic winter did not reach 
lower values than in previous cold Arctic winters," said lead author 
Gloria Manney of NASA's Jet Propulsion Laboratory in Pasadena, 
Calif., and the New Mexico Institute of Mining and Technology in 
Socorro. "The difference from previous winters is that temperatures 
were low enough to produce ozone-destroying forms of chlorine for a 
much longer time. This implies that if winter Arctic stratospheric 
temperatures drop just slightly in the future, for example as a 
result of climate change, then severe Arctic ozone loss may occur 
more frequently." 

The 2011 Arctic ozone loss occurred over an area considerably smaller 
than that of the Antarctic ozone holes. This is because the Arctic 
polar vortex, a persistent large-scale cyclone within which the ozone 
loss takes place, was about 40 percent smaller than a typical 
Antarctic vortex. While smaller and shorter-lived than its Antarctic 
counterpart, the Arctic polar vortex is more mobile, often moving 
over densely populated northern regions. Decreases in overhead ozone 
lead to increases in surface ultraviolet radiation, which are known 
to have adverse effects on humans and other life forms. 

Although the total amount of Arctic ozone measured was much more than 
twice that typically seen in an Antarctic spring, the amount 
destroyed was comparable to that in some previous Antarctic ozone 
holes. This is because ozone levels at the beginning of Arctic winter 
are typically much greater than those at the beginning of Antarctic 
winter. 

Manney said that without the 1989 Montreal Protocol, an international 
treaty limiting production of ozone-depleting substances, chlorine 
levels already would be so high that an Arctic ozone hole would form 
every spring. The long atmospheric lifetimes of ozone-depleting 
chemicals already in the atmosphere mean that Antarctic ozone holes, 
and the possibility of future severe Arctic ozone loss, will continue 
for decades. 

"Our ability to quantify polar ozone loss and associated processes 
will be reduced in the future when NASA's Aura and CALIPSO 
spacecraft, whose trace gas and cloud measurements were central to 
this study, reach the end of their operational lifetimes," Manney 
said. "It is imperative that this capability be maintained if we are 
to reliably predict future ozone loss in a changing climate." 

For more information on NASA's Aura mission, visit: 


http://www.nasa.gov/aura 


For more information on NASA's CALIPSO mission, visit: 


http://www.nasa.gov/calipso 

	
-end-



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