As spring approaches in the southern Hemisphere, the ozone hole has been opening over Antarctica for decades now. Between September 7 and October 13, 2022, it occupied an average area of 23.2 million square kilometers: this made it 1.6 million square kilometers smaller than in 2021 and thus continues the mostly positive trend of recent years, NASA and NOAA report in a statement.
The ozone hole is not a hole in the classic sense in which there is no more ozone molecules: in this area the ozone concentration only extends from 130 to 220 Dobson units, while it is at least 260 to 320 Dobson before the mass use of CFC -units included. In lower latitudes, values between 300 and 500 Dobson units are the norm. The thinning begins in spring in the southern hemisphere: in winter, the responsible FCKW molecules accommodate themselves above the South Pole; As soon as the polar night ends and sunlight starts, the destruction of the ozone molecules begins by free radicals. Only rising temperatures in the stratosphere then end the dismantling process again.
Depending on the weather conditions, the size of the ozone hole varies, which is why new records have also been set in recent years. "Over time, however, steady progress is being made, and the hole is getting smaller and smaller, " says Paul Newman from NASA: for two decades, atmospheric researchers have been observing a trend that could lead to the disappearance of the ozone hole again in the long term.
For the first time, the phenomenon was described in the 1980s and finally attributed to released FCKW. As part of the Montreal Protocol, which came into force in 1989, the global community banned the production and use of this long-lasting gases, the concentration of which is now slowly falling in the atmosphere-even if illegal releases are always observed.
In 2022, experts had also feared that the ozone hole could grow against the trend: the eruption of the Hunga Tonga-Hunga Ha'apai in January reached into the stratosphere and thus also up to the ozone layer. The eruption of Mount Pinatubo in 1991 had released significant amounts of sulfur dioxide, which at that time intensified the depletion of the ozone layer. However, no direct effects of Hunga Tonga were detected in the data of the Antarctic stratosphere.
