This year, the ozone hole over Antarctica
was far smaller than expected. In fact,
it was the smallest since the ozone hole was discovered,
the result of unusual weather patterns in the stratosphere over the South Pole.
The ozone hole is caused by interactions between chlorine from chemicals called chlorofluorocarbons, or CFCs,
and ozone. Although CFCs were banned
by the Montreal Protocol in 1987, they last a long time in the atmosphere.
Ozone depletion is enhanced when temperatures are colder.
So the ozone hole fluctuates with the season, appearing during the colder,
austral winter months and disappearing by summer.
It reaches an annual maximum size in early southern spring, usually in October.
This year, the polar vortex, a spiraling wind pattern over the South Pole,
was unusually wonky. This warmed the stratosphere –
the part of the atmosphere with the ozone layer – which significantly slowed down ozone depletion.
Although the small ozone hole this year was caused by weather patterns,
the ozone layer has shown overall signs of improvement as a result of the Montreal Protocol.
NASA and NOAA have worked together to study
study the ozone hole since its discovery.
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