Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0474
alan.d.buis@jpl.nasa.gov
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:
For more information on NASA's CALIPSO mission, visit:
-end-
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