Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov
Patrick Lynch
Goddard Space Flight Center, Greenbelt, Md.
301-286-3854/757-897-2047
patrick.lynch@nasa.gov
RELEASE: 11-357
NASA, NOAA DATA SHOW SIGNIFICANT ANTARCTIC OZONE HOLE REMAINS
WASHINGTON -- The Antarctic ozone hole, which yawns wide every
Southern Hemisphere spring, reached its annual peak on Sept. 12. It
stretched to 10.05 million square miles, the ninth largest ozone hole
on record. Above the South Pole, the ozone hole reached its deepest
point of the season on Oct. 9, tying this year for the 10th lowest in
this 26-year record.
NASA and the National Oceanic and Atmospheric Administration (NOAA)
use balloon-borne instruments, ground-based instruments and
satellites to monitor the annual Antarctic ozone hole, global levels
of ozone in the stratosphere and the manmade chemicals that
contribute to ozone depletion.
"The colder than average temperatures in the stratosphere this year
caused a larger than average ozone hole," said Paul Newman, chief
scientist for atmospheres at NASA's Goddard Space Flight Center in
Greenbelt, Md. "Even though it was relatively large, the area of this
year's ozone hole was within the range we'd expect given the levels
of manmade ozone-depleting chemicals that continue to persist in the
atmosphere."
The ozone layer helps protect the planet's surface from harmful
ultraviolet radiation. Ozone depletion results in more incoming
radiation that can hit the surface, elevating the risk of skin cancer
and other harmful effects.
"The manmade chemicals known to destroy ozone are slowly declining
because of international action, but there are still large amounts of
these chemicals doing damage," said James Butler, director of NOAA's
Global Monitoring Division in Boulder, Colo.
In the Antarctic spring (August and September) the sun begins rising
again after several months of darkness and polar-circling winds keep
cold air trapped above the continent. Sunlight-sparked reactions
involving ice clouds and manmade chemicals begin eating away at the
ozone. Most years, the conditions for ozone depletion ease before
early December when the seasonal hole closes.
Levels of most ozone-depleting chemicals in the atmosphere have been
gradually declining as the result of the 1987 Montreal Protocol, an
international treaty to protect the ozone layer. That international
treaty caused the phase-out of ozone-depleting chemicals, which had
been used widely in refrigeration, as solvents and in aerosol spray
cans.
However, most of those chemicals remain in the atmosphere for decades.
Global atmospheric computer models predict that stratospheric ozone
could recover by midcentury, but the ozone hole in the Antarctic will
likely persist one to two decades longer, according to the latest
analysis in the 2010 Quadrennial Ozone Assessment issued by the World
Meteorological Organization and United Nations Environment Programme,
with co-authors from NASA and NOAA.
NASA currently measures ozone in the stratosphere with the
Dutch-Finnish Ozone Monitoring Instrument, or OMI, on board the Aura
satellite. OMI continues a NASA legacy of monitoring the ozone layer
from space that dates back to 1972 with launch of the Nimbus-4
satellite. The instrument measured the 2011 ozone hole at its deepest
at 95 Dobson units on Oct. 8 this year. This differs slightly from
NOAA's balloon-borne ozone observations from the South Pole (102
Dobson units) because OMI measures ozone across the entire Antarctic
region.
That satellite-monitoring legacy will continue with the launch of
NASA's National Polar-orbiting Operational Environmental Satellite
System Preparatory Project, known as NPP, on Oct. 28. The satellite
will carry a new ozone-monitoring instrument, the Ozone Mapping and
Profiler Suite. The instruments will provide more detailed daily,
global ozone measurements than ever before to continue observing the
ozone layer's gradual recovery.
It will take a few years of averaging yearly lows in Antarctic ozone
to discern evidence of recovery in ozone levels because seasonal
cycles and other variable natural factors -- from the temperature of
the atmosphere to the stability of atmospheric layers -- can make
ozone levels dip and soar from day to day and year to year.
NOAA has been tracking ozone depletion around the globe, including the
South Pole, from several perspectives. NOAA researchers have used
balloons to loft instruments 18 miles into the atmosphere for more
than 24 years to collect detailed profiles of ozone levels from the
surface up. NOAA also tracks ozone with ground-based instruments and
from space.
For the updates on the status of the Antarctic ozone layer, visit:
http://ozonewatch.gsfc.nasa.gov
For more information on the Antarctic ozone hole, visit:
http://www.ozonelayer.noaa.gov
-end-
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