The ozone layer in the upper layers of the Antarctic atmosphere has returned to normal after one of the longest and most striking deterioration episodes studied in recent decades. Experts from the Copernicus program of the European Space Agency (ESA) consider that the hole in this part of the ozone layer has returned to its usual records as of December 20.
Studies on this process are still underway and the hypothesis remains that the exceptionally high degradation of ozone molecules during much of this year has been due in part to the effects of the Hunga-Tonga-Hunga-Ha' volcanic eruption. apai and processes related to climate change.
The Copernicus program considers that "the 2023 ozone hole has completed its cycle after a series of rises, falls and rebounds that the specialists themselves have considered surprising," indicates this ESA climate program.
"The ozone hole opened early and quickly, becoming one of the largest on record in mid-September, and is one of the longest observed to date. The causes of this behavior point to climate change or volcanic emissions, but the precise reasons are not yet known," indicates Copernicus in the balance of this process published on its website.
Data on the concentration of this molecule in the stratosphere indicate that "the 2023 Antarctic ozone hole finally closed on December 20, becoming the seventh most recent closure observed, according to our data," details Copernicus. Temperatures in the southern hemisphere's polar stratosphere increased as predicted by the Copernicus Atmosphere Monitoring Service (CAMS), and winds reduced, causing a breakdown of the polar vortex, allowing the ozone layer to in the area will recover.
The 2023 ozone hole very quickly caught the attention of specialists for its early onset, causing one of the largest ozone holes observed in mid-September of any year.
The area of the ozone hole subsequently shrank significantly to almost average, but was unusually persistent during November, remaining above 14.2 m2, roughly the area of Antarctica, until early December, becoming the third largest largest for the time of year in CAMS records.
Then the closing process began, with a series of rebounds that delayed the final closure until December 20. The longest-lasting ozone hole in our data record dating back to 1979 was in 1999 and 2020; both lasted until December 27.
It is the fourth year in a row that the southern hemisphere ozone hole has shown peculiar behavior, despite global success in banning ozone-depleting substances.
Researchers suggest that the eruption of the Hunga Tonga – Hunga Ha'apai volcano in early 2022, which injected huge amounts of water vapor into the stratosphere, could have influenced the extent and intensity of ozone depletion in 2023 Other specialists explain that a period of positive Southern Annular Mode could have delayed the “final stratospheric warming” that normally closes the ozone hole, breaking the polar vortex.
New research also points to long-term atmospheric dynamics detected since the early 2000s as a possible driver of the large ozone holes observed in recent years, suggesting possible impacts of climate change.
Although research has advanced considerably in recent years, there are still gaps in the knowledge of the precise chemical and dynamic processes and interactions with other layers, due to the difficulties in obtaining observations in this remote region of our atmosphere.
Researchers collect data from stratospheric balloons and satellite observations, but the analysis can take several months or years, and some interactions are still not well understood, which is why there is no unequivocal answer to the recent changes observed in the behavior of the hole. ozone.
The ozone layer is located in the stratosphere, between 15 and 30 km altitude. Protects life on Earth from harmful ultraviolet radiation. In the late 1970s and early 1980s, scientists showed that ozone-depleting substances such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs) accumulating in the stratosphere were causing seasonal thinning of the ozone layer. of the southern hemisphere, that is, the ozone hole.
Ozone-depleting substances were banned by the Montreal Protocol in 1987, but chlorinated and brominated gases emitted before the ban will remain in the atmosphere for several decades.
The ozone hole is the result of the interaction between ozone-depleting substances, solar radiation, stratospheric clouds, and the extreme cold and wind speeds of the polar vortex that keep air masses confined over the polar region. .
With the arrival of southern spring, in August, the southern hemisphere begins to receive solar radiation. Temperatures remain extremely low and zonal winds remain high in the stratosphere after the southern winter, promoting ozone depletion by preventing the polar regions from receiving ozone-rich air masses from the southern mid-latitudes. This is known as dynamic ozone depletion.
Extreme cold and the presence of water vapor and aerosols create polar stratospheric clouds that, by interacting with chlorinated and brominated species (which act as catalysts), along with solar radiation, can also drive ozone loss. This is known as chemical exhaustion.
Between November and December, depending on the year, southern stratospheric temperatures increase, breaking the polar vortex and stopping the depletion of the ozone layer, “closing” the ozone hole.
