The Antarctic ozone hole expanded rapidly in early September, reaching an estimated 25 million square kilometers (9.6 million square miles), about 5 million square kilometers (1.8 million square miles) above the average for the period, according to the Copernicus Atmosphere Monitoring Service.
The service said Wednesday that the ozone hole had developed at a typical rate since the second half of August, consistent with patterns observed over the past 46 years.
However, its area grew sharply during the first half of September, with forecasts indicating that it could expand further in mid-September.
Copernicus attributed the rapid development to a sudden drop in minimum temperatures at about 20 kilometers (12.4 miles) above the South Pole, where temperatures can allow the formation of polar stratospheric clouds.
These clouds contribute to chemical ozone destruction by activating halogens in the presence of sunlight during the Southern Hemisphere's spring, generally between August and November.
Despite the rapid increase in area, other indicators monitored by the service, including the minimum ozone column value within the defined ozone-hole area and the ozone mass deficit, remained close to historical average levels.
The ozone layer protects life on Earth from harmful ultraviolet radiation by absorbing much of it.
Human-made emissions have caused significant thinning of the layer over the past several decades, increasing exposure to ultraviolet radiation.
The Antarctic ozone hole is particularly pronounced because the region's stable polar vortex and stratospheric winds help maintain the cold conditions associated with ozone depletion.
The ozone hole typically forms over Antarctica during the Southern Hemisphere's spring and gradually changes as atmospheric conditions evolve.
The largest Antarctic ozone hole on record took place in 2006, covering 29.6 million square kilometers (11.4 million square miles), according to Copernicus.
