In 2022, the World Meteorological Organization (WMO) and the United Nations Environment Program presented
At the same time, researchers from the Monitoring ServiceThe atmosphere of the European Copernicus space program reported that the ozone hole over Antarctica in 2022 was the 12th largest in 43 years of observations. At the same time, for three years in a row, the ozone hole above the south pole of the Earth closes anomalously late: only at the end of December.
Change in the ozone layer in 2022. Video: Copernicus Atmosphere Monitoring Service, ECMWF
What is the ozone layer and ozone hole?
Ozone is a colorless gas found in alllayers of the atmosphere. This is an allotropic modification of oxygen, in which three atoms of this chemical element are connected. Ozone is a very powerful oxidizing agent: it is much more reactive than diatomic oxygen and enters into chemical interaction with almost all metals and non-metals, many inorganic and organic substances.
Most of the ozone in the earth's atmosphere (about 90%)is in the stratosphere. It is part of the Earth's gaseous envelope that begins at an altitude of about 10–16 km (depending on latitude) above the planet's surface and extends to an altitude of about 50 km. Ozone in the stratosphere protects life on Earth from harsh ultraviolet radiation.
Distribution of ozone in the atmosphere."Useful ozone" is considered to be that which is formed in the stratosphere Above 15 km from the Earth's surface. It is this area that protects living organisms from harmful ultraviolet radiation. An increase in the concentration of ozone in the troposphere near the surface of the planet is associated with anthropogenic emissions and has a harmful, toxic character. Image: Salawitch et al, WMO, 2019; Copernicus Atmosphere Monitoring Service
The ozone hole is an area typically inpolar regions, in which the total ozone content in the atmospheric column (a column of air with an area of 1 m²) falls below 220 Dobson units. One such unit is equal to a 10 micron ozone layer at standard pressure and temperature.
Typically, when people talk about ozone holes,refer to the thinning of the ozone layer over Antarctica. This is due to the fact that the special meteorological and chemical conditions that form above the south pole increase the anthropogenic impact on the stratosphere.
The maximum size of the ozone hole over Antarctica from 1979 to 2022. Image: CAMS
Low temperatures of the polar night and the difference betweencold poles and warmer temperate zones leads to the formation of a stratospheric polar vortex. It consists of strong air currents circulating high in the atmosphere over Antarctica, sealing off the cold air above and allowing ozone depleting chemicals to build up. As a result, an ozone hole forms over the region every spring in the southern hemisphere.
However, this is not the only knownsimilar object. Similar (albeit less regular and less stable due to the proximity to the mountain ranges of the mainland) processes can also be observed at the North Pole. And a Canadian researcher last year reported the discovery of a large ozone hole in the tropical region.
How has the ozone hole changed in 2022?
As every year, the arrival of the Australian summer (inIn the southern hemisphere, spring begins in September and summer in December) with relatively higher stratospheric temperatures causes the polar vortex to break up. As a result, higher concentrations of ozone in the mid-latitudes move toward the south polar region, filling the depleted area and closing the hole.
Annual seasonal formation and closureozone hole over Antarctica. Averaged data of long-term observations and anomalous values for 2020–2022. Image: Copernicus Atmosphere Monitoring Service, ECMWF
But, while the average area of the ozone holeusually decreasing rapidly in October and even faster in November, in the last three years, researchers have observed that the ozone hole persists until November and closes only in December. Long-term observations show that this used to happen in late October or November, and in 2022 the ozone hole closed only in mid-December. At the same time, the longest ozone hole in the history of observations in 2020 lasted even longer and closed only on December 28.
A satellite study showed that in 2022year, the maximum area of the ozone hole was almost 25 million km². This is the 12th result in the entire history of observations since 1979. At the same time, researchers previously recorded a long-term trend towards a reduction in the area of the hole since 2000; only the last three years have broken this trend.
The area of the ozone hole above the South Pole according to long-term observations. Image: CAMS
Restoration of the ozone layer or growth of holes?
As noted in a study by the UN and WMO,The concentration of ozone-depleting substances in the stratosphere, although slowly, has been changing: it has been declining since the late 1990s. This is due, according to researchers, with the adoption of the Montreal Protocol on Substances that Deplete the Ozone Layer. This document, adopted in 1987 and entered into force in 1989, defined a list of measures to protect the ozone layer. First of all, he introduced a phased restriction on the production and use of chlorofluorocarbons.
Reducing the amount of substances that destroy ozone in the troposphere. Observational data and forecast. Image: WMO, UNEP, NOAA, NASA, European Commission
However, the fact that this lengthy"ozone hole season" is repeating for the third time in a row, suggesting additional factors may be at work in the South Pole's stratosphere. Researchers from the atmospheric monitoring service of the European Copernicus space program name three possible factors, two of which are constant, and the third is characteristic only for 2022.
First, size and lifespanthe ozone hole may depend on the strength of the polar vortex. The area of low atmospheric pressure formed under the influence of many climatic factors accumulates a greater amount of harmful substances. For example, the development of the ozone hole in 2019 was abruptly halted by a sudden stratospheric warming event over Antarctica in September that disrupted the polar vortex.
In addition, an ozone-depleting area creates a feedback loop through the radiative effect, slowing down the spring warming of the stratosphere and therefore extending the life of the ozone hole.
Secondly, global warming iscooling effect in the middle and upper stratosphere: the greenhouse effect reduces the exchange between different layers of the earth's atmosphere (warmer air masses remain "locked" in the lower layers). According to the researchers, the decrease in the temperature of the stratosphere affects the growth and increase in the "life expectancy" of ozone holes.
Finally, in 2022 there was a powerful eruptionVolcano Hunga-Tonga-Hunga-Haapai. The release of a huge array of aerosols and ash particles led to one of the largest disturbances in the stratosphere in many years. Although the effect of the release on the state of the ozone layer is still little understood, the researchers believe that it could lead to an increase in the size and life of the ozone hole.
Changes in the area of ozone holes in long-term observations. Video: Copernicus Atmosphere Monitoring Service
All this indicates that localyear-on-year changes in Antarctica do not contradict the global trend towards the restoration of the ozone layer as a whole in the Earth’s atmosphere. However, due to the long lifespan of the chemicals that destroy ozone, it will take several more decades.
The UN and WMO predict in their report thatsubpolar regions of Antarctica, ozone concentrations will return to pre-1980 levels only by 2066. At the same time, the forecast for the Arctic is more positive - 2045, and on average for most of the globe in the zone located between 60 ° N. and 60° S — around 2040.
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