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As the ice melts and the gradual disappearance of ecosystems continue in Antarctica, the ozone layer above the continent is also in a bad situation. Whereas 2019, under the effect of favorable atmospheric conditions, the hole in the ozone layer had shrunk, This is no longer the case today. At the beginning of the month, the hole covered a surface of 25 million km², a considerable increase over last year's figures. In question ? Atmospheric temperatures and photochemical reactions produced by aerosols of human origin.
In 2019, scientists revealed that the Antarctic ozone hole reached its smallest annual peak since monitoring began in 1982, but the update of 2020 on this atmospheric anomaly brings a sobering perspective. “Our observations show that the ozone hole in 2020 has grown rapidly since mid-August and covers most of the Antarctic continent, with a size well above the average ", explains project manager Diego Loyola of the German Aerospace Center.
New measurements from the European Space Agency's Copernicus Sentinel-5P satellite show the hole has reached its maximum size of around 25 million square kilometers on 2 October of this year. This puts it at about the same level as the ozone holes in 2018 and 2015, which respectively recorded peaks of 22.9 and 25.6 million square kilometers.
“There is great variability in the way ozone holes develop each year.. The hole in the ozone layer 2020 looks like that of 2018, which was also a pretty big hole, and is definitely at the top of the peloton of 15 last years ", says atmospheric physicist Vincent-Henri Peuch from the European Center for Medium-Range Weather Forecasts.
In addition to fluctuating from year to year, the ozone hole over Antarctica is shrinking and also increasing every year, ozone concentrations inside the hole depleting as temperatures in the stratosphere get colder. When this happens - especially, when polar stratospheric clouds form at temperatures below –78 ° C -, chemical reactions destroy ozone molecules in the presence of solar radiation.
“With the return of sunlight to the South Pole in recent weeks, we have seen continued ozone depletion in the region. After the unusually small and short lived ozone hole in 2019, which was due to special weather conditions, we still have a pretty big one this year, which confirms that we must continue to enforce the Montreal Protocol banning emissions of chemicals that deplete the ozone layer ", explains Peuch.
The Montreal Protocol marked an important step in environmental protection, by phasing out the manufacture of harmful chlorofluorocarbons (CFC) - chemicals previously used in refrigerators, packaging and sprays - which destroy ozone molecules in sunlight.
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As we now know that human action on this front is helping us fix the Antarctic ozone hole, the continuous fluctuations from year to year show that the healing process will be long. An evaluation carried out in 2018 by the World Meteorological Organization revealed that ozone concentrations over Antarctica would return to levels before years 1980 towards 2060.
Although the maximum peak of 2020 is not the greatest ever recorded - it was that of 2000, with a hole 29.9 million square kilometers -, it is always significant, the hole being also one of the deepest in recent years. The researchers claim that the event of 2020 was driven by a strong polar vortex : a wind phenomenon maintaining stratospheric temperatures over Antarctica.
On the other hand, warmer temperatures over the past year are responsible for the record small size of ozone holes in 2019. “It is important to recognize that what we have seen in 2019 was due to warmer stratospheric temperatures. It was not a sign that atmospheric ozone had suddenly set itself on a fast track to recovery ", says Paul Newman, geophysicist at NASA's Goddard Space Flight Center.
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Ozone, Antarctica, Ozone depletion
World news – THAT – The size of the Antarctic ozone hole has increased dramatically in 2020