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The ozone hole over Antarctica that typically forms by mid-August every year and becomes bigger through the month started appearing late this year.
The ozone columns in the stratosphere were well over the threshold value till the end of August 2024, according to Copernicus Atmosphere Monitoring Service (CAMS) that regularly monitor atmospheric conditions leading to the depletion of the ozone layer.
This resulted in a much smaller area of the hole on September 13, 2024 — 18.48 million square kilometres, smaller than in recent years for this period.
The ozone layer prevents harmful radiation from the Sun from passing into the troposphere where all lifeforms occur. So, the hole forming late and staying small is a welcome news and is widely recognised as a success of the international agreement of Montreal Protocol that was signed on September 16, 1987 to ban ozone-depletion substances such as chlorofluorocarbons, halons, carbon tetrachloride and hydrochlorofluorocarbons from being produced and used.
But multiple other factors play a role in the erosion of the ozone layer. "The ozone depletion process needs solar radiation, extremely low temperatures within a strong polar vortex, polar stratospheric clouds and ozone depleting substances," according to CAMS scientists who call this process a “complex stratospheric cocktail”.
One such element is the polar vortex which regulates the stratospheric temperatures and wind patterns that contribute to ozone hole formation.
During the austral winter (August) this year, the onset of the Southern Polar Vortex was highly disrupted, according to CAMS.
“When the polar vortex is weak, with higher temperatures and slower winds than usual in the stratosphere, the ozone depletion process is weaker, leading to ozone columns above 220 dobson units, the threshold value used to define the Antarctic ozone hole,” they explained.
Two sudden stratospheric warming events were noted in July and August this year, according to an analysis by NASA’s Earth Observatory, during which temperatures jumped 15ºC and 17ºC respectively. Such a phenomena is not common over the South Pole.
“As a result, the southern hemisphere polar vortex was elongated and with weakened winds, as opposed to the circular, cold and fast winds conditions that favour ozone depletion, seen for example in 2023,” according to CAMS.