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By Peter Rejcek
Latest depletion event 10th largest in last 30 years.
The size of the annual ozone hole over Antarctica peaked
in late September at 23.8 million square miles, slightly
smaller than the North American continent, according to
a news release from the National Oceanic and Atmospheric
Administration (NOAA) in November.
That ranks as the 10th largest since satellite measurements
began in 1979. Ozone over South Pole Station also reached
its thinnest vertical point of the year on Sept. 26, NOAA
reported.
The ozone layer in the Earth’s stratosphere, between
10 and 30 kilometers above the ground, helps shield the
planet from harmful ultraviolet radiation. Human-produced
compounds known as chlorofluorocarbons, or CFCs, release
ozone-destroying chemicals into the atmosphere responsible
for the depletion.
Extreme cold, ice cloud formation in the stratosphere,
and a pattern of rapidly circulating air, called the polar
vortex, make the ozone layer over Antarctica much more
vulnerable to CFC-destruction than anywhere else on the
planet.
International agreements have strictly limited the use
of CFCs since the early 1990s. Scientists predict the
ozone hole will recover by the end of the century.
NOAA scientists working from the Atmospheric Research
Observatory at the South Pole Station launch balloons
to measure ozone vertically at least once a week, and
more frequently in the austral spring when the polar vortex
forms. Another group led by Terry Deshler from the University
of Wyoming performs similar measurements from McMurdo
Station during the formation of the ozone hole each austral
spring. [See previous article: Ozone hole.]
Work on the ground at South Pole can be difficult, with
temperatures approaching minus 70 degrees Celsius (minus
100 degrees Fahrenheit). NOAA engineer Patrick Cullis
and NOAA Corps officer Marc Weekley have nearly completed
a yearlong assignment there to collect atmospheric data
and keep instruments operating.
“It’s actually been hardest to launch during
the long dawn before sunrise,” Cullis said in a NOAA
press release. “The landscape starts to brighten,
but there are no shadows to warn you of the large clumps
of snow left in your path by the movement of bulldozers.
“Plus, this year, the polar dawn brought an intense
35-knot storm lasting over a week. Even during lulls in
the storm, launching large plastic balloons was like running
a 50-meter dash in soft snow. My lungs would burn from
the combination of 10 pounds of gear, soft snow, and thin
air.”
Scientists in Antarctica, including teams from NOAA and
the University of Wyoming, have been measuring atmospheric
ozone since 1986.
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