The ozone hole over Antarctica has opened weeks earlier than usual and could grow to near-record size due to delayed effects of the massive Hunga Tonga-Hunga Ha鈥檃pai volcanic eruption last year.
The hole in the ozone layer has been gradually healing since the 1987 Montreal Protocol led to the phase-out of ozone-depleting chemicals like chlorofluorocarbons (CFCs), but it opens and closes seasonally every year.
In recent years, the hole has started to open in mid-to-late August, when spring begins in the southern hemisphere and the increasing sunlight drives the ozone-destroying activity of the remaining CFCs in the atmosphere. It then closes in November or early December.
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Something strange appears to be happening this year, however, because the ozone hole began opening at the very beginning of August 鈥� several weeks early. By 10 August, it had already grown to in size, whereas it was still completely closed on the same date in 2021 and 2022.
at the Australian Bureau of Meteorology says this early opening is related to the eruption of the Hunga Tonga-Hunga Ha鈥檃pai volcano in Tonga in January 2022 鈥� considered the most explosive of the 21st century.
The volcano injected huge amounts of water vapour into the stratosphere. Above Antarctica, this water vapour has since turned into icy clouds that provide a surface on which CFCs can react with ozone, thereby speeding up its depletion, says Lucas.
The water vapour from the eruption didn鈥檛 affect the ozone hole in 2022 because it didn鈥檛 reach Antarctica in time for its usual opening, he says.
The early opening of the ozone hole this year could see it become one of the biggest on record, says Lucas. 鈥淲e鈥檙e predicting a bigger ozone hole this year, comparable to some of the biggest ones we鈥檝e seen,鈥� he says.
at the University of Wollongong in Australia says the early opening isn鈥檛 a major concern for wildlife in Antarctica because most organisms are still under ice or snow at this time of year.
However, if the ozone hole also ends up closing later this year, it could be harmful to animals and plants that emerge later in spring or early summer, she says, because there will be less ozone in the atmosphere to protect them from the sun鈥檚 ultraviolet rays.
The ozone hole has closed later than normal in the past three years because of factors including Australia鈥檚 Black Summer bushfires in 2019-20, which released extreme amounts of ozone-destroying smoke, but it is too early to know when it will close this year, says Robinson.
The extra water vapour that has caused the ozone hole to open early has also created a strong polar vortex 鈥� an expanse of cold air that circulates around the South Pole 鈥� which may lead to cooler-than-expected conditions during the upcoming summer of Australia, New Zealand and other southern hemisphere countries, says Lucas.
There have been fears that the summer will be hot and dry due to El Ni帽o conditions in the tropical Pacific 鈥� but a tug of war between El Ni帽o and the strong polar vortex could lead to milder weather, he says.
