The ozone hole over Antarctica has expanded to its largest size in 10 years, reaching approximately 9.6 million square miles, according to scientists from NASA and the National Oceanic and Atmospheric Administration (NOAA). This area is more than double the size of the United States.
The significant expansion is attributed to unusual weather patterns and a particularly powerful polar vortex over Antarctica this season. "An unusually powerful polar vortex has extended ozone depletion in the Antarctic this season, allowing the hole to grow to proportions we haven't seen in a decade," explained Paul Newman, a senior scientist at NASA's ozone research team.
Measurements indicate the hole reached its peak extent between September 7 and October 13, with the largest single-day measurement on September 18, stretching to 10.5 million square miles. This makes it the seventh largest observed in 48 years of record-keeping, and about 90% the size of the largest hole ever recorded in 2000.
While the annual ozone hole forms each autumn, this year's size is linked to a stronger-than-average polar vortex. "The polar vortex was unusually large this year in part because planetary-scale weather systems that typically well up from the lower atmosphere and break up the vortex were especially weak in August and September," said Amy Butler, a research scientist at NOAA's Chemical Sciences Laboratory. This weakness allowed the vortex winds to remain further from the South Pole, creating a larger area conducive to ozone depletion.
Ozone in the stratosphere acts as Earth's natural sunscreen, protecting the planet from harmful ultraviolet radiation. Ozone depletion occurs when human-made compounds containing chlorine and bromine are released into the atmosphere. These gases are carried to the stratosphere, where UV radiation breaks them down, releasing atoms that destroy ozone molecules, particularly when interacting with cloud particles.
Scientists estimate that due to the Montreal Protocol, which phased out ozone-depleting substances like chlorofluorocarbons (CFCs) starting in 1987, the ozone layer is showing signs of recovery. These harmful chemicals are expected to dissipate from the atmosphere by the 2070s, leading to the full recovery of the ozone hole. Despite this progress, the current hole's size is still significant compared to the 1980s, when depletion was first detected, as these substances persist in the atmosphere.
Newman noted that the 2026 ozone hole could have been even larger if ozone-depleting substances were as prevalent as they were at their peak in 2000.