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The Antarctic Ozone HoleReturn to the South Pole ozone page. |
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The Antarctic Ozone HoleReturn to the South Pole ozone page. |
The Antarctic Ozone Hole was discovered by the British Antarctic Survey from data obtained with a Dobson ozone spectrophotometer at Halley Bay station in the 1981-1983 period. They reported the October ozone loss in 1985. Satellite measurements then confirmed that the springtime ozone loss was a continent-wide feature. Research conducted during the National Ozone Expeditions to the U.S. McMurdo Station in 1986 and 1987, and NASA stratospheric aircraft flights into the Antarctic region from Chile in 1987 showed conclusively that the ozone loss was related to halogen (chlorine)-catalyzed chemical destruction which takes place following spring sunrise in the Antarctic polar region. The chlorine is derived from manmade chlorofluorocarbons (CFCs) which have migrated to the stratosphere and have been broken down by solar ultraviolet light, freeing chlorine atoms. The cold dark Antarctic winter, with its stratospheric ice clouds mixed with manmade chlorine, sets the stage for springtime chemical ozone destruction when the missing ingredient in the photochemical reactions, sunlight, appears.
Owing to regulations on the production of certain ozone-destroying,
chlorinated compounds, which went into effect in January 1996, the atmospheric
concentration of some of these man-made substances has begun to decline,
(CFC-11 vs. Time Plot and other CFC info) and should reach maximum levels
in the stratosphere near the turn of the century. It is anticipated that the recovery of
the Antarctic Ozone Hole can then begin; however, because of the slow rate of healing, it
is expected that the beginning of this recovery will not be conclusively detected for a
decade or more into the next century, and that complete recovery of the Antarctic ozone
layer will not occur until the year 2050 or later. The exact date of recovery will depend
on the effectiveness of present and future regulations on the emission of CFCs and their
replacements, which, while more ozone-friendly, will also require regulation during the
next century. It will also depend on climate change in the intervening years. For example,
a colder stratosphere would exacerbate ozone loss and prolong recovery.
 To the South Pole Ozonesonde Program |
Climate Monitoring & Diagnostics Laboratory 325 Broadway R/E/CG Boulder, CO 80303 (303) 497-6074 |