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NASA
Leads Study Of Unprecedented Arctic Ozone Loss
Ozone in Earth's
stratosphere at an altitude of approximately 12 miles (20 kilometers) in
mid-March 2011, near the peak of the 2011 Arctic ozone loss. Right: chlorine
monoxide - the primary agent of chemical ozone destruction in the cold polar
lower stratosphere - for the same day and altitude. Image credit: NASA/JPL-Caltech
Oct. 2, 2011 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."
Other institutions participating in
the study included Alfred Wegener Institute for Polar and Marine Research,
Potsdam, Germany; NASA Langley Research Center, Hampton, Va.; Royal Netherlands
Meteorological Institute, De Bilt, The Netherlands; Delft University of
Technology, 2600 GA Delft, The Netherlands; Science Systems and Applications,
Inc., Greenbelt, Md., and Hampton, Va.; Science and Technology Corporation,
Lanham, Md.; Environment Canada, Toronto, Ontario, Canada; Central Aerological
Observatory, Russia; NOAA Earth System Research Laboratory, Boulder, Colo.;
Arctic Research Center, Finnish Meteorological Institute, Finland; Danish
Climate Center, Danish Meteorological Institute, Denmark; Eindhoven University
of Technology, Eindhoven, The Netherlands; Arctic and Antarctic Research
Institute, St. Petersburg, Russia; National Institute for Environmental Studies,
Japan; National Institute for Aerospace Technology, Spain; and University of
Toronto, Ontario, Canada.
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
Alan Buis
818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov
Steve Cole 202-358-0918
Headquarters, Washington
Stephen.e.cole@nasa.gov
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