Early data show that the ozone hole that develops each year over Antarctica
has reached about the same magnitude as those of the past several years,
according to scientists from the Commerce Department’s National Oceanic and
Atmospheric Administration and NASA.
Last year, the geographic area covered by the ozone hole was one of the
largest on record. By early October, additional data will provide a more
complete picture of the extent and intensity of this year’s ozone hole in
Antarctica.
The primary cause of the ozone hole, which has occurred each year over
Antarctica since the early-to-mid-1980s, is the chemical reactions that
release chlorine and bromine into the atmosphere. The source of these
chemicals is human-produced chlorofluorocarbons and bromine containing
compounds used in a variety of industrial and commercial applications.
“While chlorine has started to decline in the atmosphere, very high
concentrations still remain at the altitude of the ozone layer. ” NOAA
researcher Sam Oltmans. The amounts are more than sufficient to cause the
ozone hole we observe each year.”
These chemicals — in combination with very cold temperatures that form
high-altitude clouds during the polar night, and a confined circumpolar
wind system, produce potent conditions for ozone destruction. These ozone-
destroying chemicals are no longer increasing because of the regulations
put in place by the Montreal Protocol. However, they break down very slowly
in the earth’s atmosphere, and a recurring annual ozone hole will be present
for several more decades. Year-to-year fluctuations in the area of the ozone
hole can be expected due to variations in upper atmospheric weather patterns.
NASA and NOAA use satellites to measure the extent and depth of the ozone
hole. NASA’s Total Ozone Mapping Spectrometer (TOMS), currently aboard the
Earth Probe satellite, and NOAA’s Solar Backscattering Ultra-Violet (SBUV/2)
instrument aboard the Polar-orbiting Operational Environmental Satellites,
have been measuring Antarctic ozone levels for more than 20 years. NOAA also
monitors the ozone hole at the South Pole using instrumented balloons that
take vertical profiles of the atmosphere and measure the amount of total
ozone present.
The ozone hole is defined as area of the region with total ozone below 220
Dobson units. A Dobson unit describes the thickness of the ozone layer in
a column directly above the location being measured.
“This year preliminary satellite data show that as of early September,
ozone hole area was in excess of 20 million square kilometers (8 million
square miles), about twice the size of the contiguous United States,” said
Lawrence Flynn, a research scientist with NOAA’s National Environmental
Satellite, Data, and Information Service.
The hole’s size similar to last year at this time and about 50 percent
larger than the 10 year (1991-2000) average for early September. With very
cold temperatures over Antarctica and with the circumpolar wind currents
(the polar vortex) in a stable pattern, a large ozone hole, similar to the
past several years has already developed.
The global ozone layer has also suffered from depletion because of an
increase in stratospheric chlorine and bromine but not to the degree that
is observed each spring in Antarctica. Ozone forms a layer that surrounds
and protects the earth from the harmful effects of the sun’s ultraviolet
radiation. Excessive amounts of UV radiation can damage important plant
and animal life on earth and in the oceans as well as contribute to
increases in skin cancer and cataracts in humans.
Video File Feed:
A B-roll of imagery and other materials will be broadcast during NASA TV
video file feed scheduled for Sept. 17 at 3 p.m., 6 p.m., 9 p.m. and
midnight EDT. NASA TV is broadcast on GE-2, transponder 9C, C-band, located
at 85 degrees West Longitude. The frequency is 3880 MHz. Polarization is
vertical and audio is monaural at 6.8 MHz.
Additional information on the science and on measurements of the ozone hole
and of atmospheric ozone depletion in general can be found at
http://www.ozonelayer.noaa.gov
and
http://toms.gsfc.nasa.gov
Links available on these sites will let you follow the development of this
year’s ozone hole.
A link under the Data menu (Current/Antarctic) on the first site gives a
plot tracking the area of the ozone hole estimated from SBUV/2 data and
another plot tracking the ozone amount at the South Pole as measured by
balloon sondes. A link on the second site uses information from Earth Probe
TOMS to estimate the minimum total ozone column within the polar vortex as
well as to track the area.
Relevant Web Sites
* NOAA’s Stratospheric Ozone
http://www.ozonelayer.noaa.gov/data/antarctic.htm
* NOAA’s National Environmental Satellite, Data, and Information Service
* NASA’s Total Ozone Mapping Spectrometer (TOMS)
