The 2023 Antarctic ozone hole, a recurring seasonal phenomenon, reached its maximum size on September 21, as reported by NASA and NOAA. The hole covered an area of approximately 10 million square miles, or 26 million square kilometers, making it the 12th largest single-day ozone hole recorded since 1979.
NASA and NOAA Measure 2023 Antarctic Ozone Hole
During the peak of the ozone depletion season, from September 7 to October 13, this year’s ozone hole exhibited an average size of 8.9 million square miles (23.1 million square kilometers), which is roughly equivalent to the size of North America. This places it as the 16th largest over this period.
Notably, the 2023 ozone hole is described as “modest” by Paul Newman, leader of NASA’s ozone research team and chief scientist for Earth sciences at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. He attributes the reduced size to declining levels of human-produced chlorine compounds and the influence of active Antarctic stratospheric weather, which slightly improved ozone levels during this year’s ozone depletion season.
Understanding the Ozone Hole
The ozone layer in Earth’s stratosphere acts as a natural sunscreen, protecting our planet from harmful ultraviolet radiation emitted by the Sun. Thinning of the ozone layer implies reduced protection against UV rays, which can lead to sunburns, cataracts, and skin cancer in humans.
Each September, the ozone layer experiences thinning, forming an “ozone hole” above the Antarctic continent. While the term “ozone hole” doesn’t indicate a complete void of ozone, it represents an area where ozone concentrations significantly drop below the historical threshold of 220 Dobson Units. The phenomenon was first documented in 1985, and scientists have been monitoring Antarctic ozone levels since 1979.
Antarctic ozone depletion is primarily a result of human-made chemicals, including chlorine and bromine compounds, rising into the stratosphere. These chemicals undergo breakdown processes that release chlorine and bromine, initiating chemical reactions that destroy ozone molecules. Notably, chlorofluorocarbons (CFCs) were among the main ozone-depleting gases, previously used in aerosol sprays, foams, air conditioners, and other applications. CFCs have long atmospheric lifetimes, ranging from 50 to over 100 years.
In 1987, the Montreal Protocol and subsequent amendments globally banned the production of CFCs and other ozone-depleting chemicals by 2010. This reduction in emissions has contributed to the decline of ozone-depleting substances in the atmosphere and has initiated signs of stratospheric ozone recovery.
Ozone Monitoring and Research
NASA and NOAA employ satellite-based instruments on NASA’s Aura, NOAA-NASA Suomi NPP, and NOAA-20 satellites to monitor the ozone layer over Antarctica and globally. Additionally, NASA’s Aura’s Microwave Limb Sounder provides estimates of ozone-destroying chlorine levels.
Scientists also determine the extent of ozone depletion by measuring the concentration of ozone within the ozone hole. At NOAA’s South Pole Baseline Atmospheric Observatory, researchers employ weather balloons carrying ozonesondes and a Dobson spectrophotometer for ground-based measurements.
In 2023, NOAA’s measurements showed a low value of 111 Dobson units (DU) over the South Pole on October 3. NASA’s measurements, averaged over a broader area, recorded a low of 99 DUs on the same date. Comparatively, in 1979, the average ozone concentration above Antarctica measured 225 DU.
The Impact of Volcanic Activity
The volcanic eruption of Hunga Tonga-Hunga Ha’apai in January 2022, which released a massive plume of water vapor into the stratosphere, is believed to have contributed to the ozone depletion in 2023. Water vapor can enhance ozone-depletion reactions over the Antarctic region early in the season.
While it is confirmed that the volcanic activity affected the Antarctic stratosphere, the exact quantification of its impact on the ozone hole is still being determined. According to Paul Newman, “If Hunga Tonga hadn’t gone off, the ozone hole would likely be smaller this year.” However, the precise influence of the eruption on the ozone hole remains the subject of ongoing research.
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