The 2026 Antarctic ozone hole ranked seventh largest by seasonal mean area in 48 years of monitoring, according to a NASA assessment published November 9. The ranking covers September 7 through October 13, the period of peak seasonal ozone depletion.
The year’s largest single-day area occurred September 18. NASA attributed the broad extent to an unusually strong Antarctic polar vortex, which created conditions favorable to ozone loss across a large region. The agency reported that depletion was less deep than in other years with large ozone holes.
What the Ranking Measures
Area and depth describe different measurements. Area records how much territory falls below the threshold used to define the ozone hole. Depth refers to how low the ozone concentration becomes within the affected region.
The threshold is 220 Dobson units, a measure of the total ozone in a column of atmosphere. An ozone hole is a region with low ozone amounts, rather than an area completely devoid of the gas.
The 2026 observations came from the Ozone Mapping and Profiler Suite aboard NOAA-20. This instrument continues a satellite record that has included NASA’s Total Ozone Mapping Spectrometer, the Ozone Monitoring Instrument aboard Aura, and OMPS aboard Suomi NPP.
How Satellites Measure Atmospheric Ozone
OMPS measures sunlight scattered back from Earth’s atmosphere. Ozone absorbs selected ultraviolet wavelengths, allowing instrument observations to be converted into estimates of its abundance.
The suite includes downward-looking instruments used for total-column and vertical-profile measurements. Total-column ozone describes the combined amount through the atmosphere above a location; a profile describes how ozone is distributed with height.
NOAA’s Climate Prediction Center describes the nadir mapper as providing daily coverage of the sunlit Earth. Repeated measurements allow scientists to follow the formation, growth, and seasonal decline of ozone-depleted regions.
The instrument program is designed to maintain stable measurements over long periods. That stability supports comparisons across seasons and years, including the distinction between short-term atmospheric variations and longer-term changes.
Ozone measurements also have operational uses. NOAA combines OMPS information with cloud forecasts to improve ultraviolet-index forecasts. The instrument can additionally detect sulfur dioxide and volcanic ash, supporting warnings relevant to aviation.
NOAA identifies continuing global ozone monitoring as part of the United States’ obligations under the Montreal Protocol. The 2026 assessment adds another season to that observing record, with separate descriptions of the ozone hole’s geographic extent and the severity of depletion within it.
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