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This year, persistent cold and strong circumpolar winds (also known as the polar vortex) contributed to the formation of a large and deep Antarctic ozone hole, just a year after scientists recorded that 2019 was the smaller since the ozone hole was discovered in 1982, according to a report by NOAA and NASA scientists on October 30, 2020.
Antarctica’s annual ozone hole – the 12th largest on record – reached its maximum size for 2020 on September 20, at about 9.6 million square miles (24.8 million square km), about three times the area of the continental United States. Nearly complete elimination of ozone in a 4-mile (6 km) column of the stratosphere above the South Pole, the scientists report. Diego Loyola, of the German Aerospace Center, said in a statement:
Our observations show that the 2020 ozone hole has grown rapidly since mid-August and covers most of the Antarctic continent, with its size well above average. What’s also interesting to see is that the 2020 ozone hole is also one of the deepest and shows record ozone values.
Ozone is a molecule made up of three oxygen atoms. A high ozone layer in the atmosphere – about 9 to 18 miles (15 to 30 km) and up – surrounds the entire Earth. It protects life on our planet from the harmful effects of the sun’s ultraviolet rays. In the 1980s, scientists began to realize that ozone-depleting chemicals, such as chlorofluorocarbons (CFCs), were creating a thin patch – a hole – in the ozone layer above Antarctica.
The size of the ozone hole over Antarctica fluctuates regularly. From August to October, during the Southern Hemisphere’s late winter, when the returning sun’s rays initiate reactions that deplete the ozone layer, the ozone hole increases in size, peaking between mid-September and mid-October. As temperatures high up in the stratosphere begin to rise in the southern hemisphere, ozone depletion slows, the polar vortex weakens and eventually breaks down, and in late December ozone levels return to normal.
At 23.3 million square km, the average ozone hole size between September 7 and October 13 used to compare with other years, the 2020 ozone hole is 12th by area. Image via NASA / NASA Ozone Watch / Katy Mersmann
The steady decline in levels of ozone-depleting chemicals controlled by the Montreal Protocol – the 1987 treaty designed to phase out ozone-depleting substances – prevented the hole from being as large as it would have been under the same conditions. decades ago, scientists say. Paul A. Newman is the chief scientist for earth sciences at NASA’s Goddard Space Flight Center. He said in a statement:
Since the peak of the year 2000, the levels of chlorine and bromine in the Antarctic stratosphere have dropped approximately 16% towards the natural level. We still have a long way to go, but this improvement has made a big difference this year. The hole would have been about one million square miles larger if there was still as much chlorine in the stratosphere as there was in 2000.
View larger. | Ozone concentration on Antarctica week 14-20 September 2020. To allow year-to-year comparisons, experts define the “ozone hole” as the area where ozone levels are below 220 Dobsonian units ( dark blue, marked with a black triangle on the color bar). Image via NOAA Climate.gov.
Here’s more from NASA, about what the ozone hole is and why it matters:
Ozone is made up of three oxygen atoms and is highly reactive with other chemicals. In the stratosphere, about 7-25 miles above the Earth’s surface, the ozone layer acts as a sunscreen, protecting the planet from ultraviolet radiation that can cause skin cancer and cataracts, suppressing the immune system and damaging plants and the sensitive plankton underlying the global food chain. Conversely, ozone that forms closer to the Earth’s surface through photochemical reactions between the sun and pollution from vehicle emissions and other sources, forms harmful smog in the lower atmosphere.
The Antarctic ozone hole forms during the southern hemisphere’s late winter when the returning sun’s rays initiate reactions that deplete the ozone layer. The cold winter temperatures that persist into spring allow for the ozone depletion process, which is why the “hole” forms over Antarctica. These reactions involve chemically active forms of chlorine and bromine derived from artificial compounds. The chemistry leading to their formation involves chemical reactions occurring on the surface of cloud particles forming in the cold stratospheric layers, ultimately leading to uncontrolled reactions that destroy ozone molecules. With warmer temperatures, fewer polar stratospheric clouds form and do not persist as long, limiting the ozone depletion process.
This animation shows the size of the ozone hole from 25 September to 18 October 2020.
Learn more about NOAA and NASA’s efforts to monitor ozone and ozone-depleting gases
Conclusion: The Antarctic ozone hole in 2020 is among the largest and deepest in recent years
Through NASA
Via World Meteorological Organization
Via ESA
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