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Why can the size of the Antarctic ozone hole vary from year to year?

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ozone depletion — Ozone depletion The Antarctic ozone hole reaches its maximum extent in October of each year. On October 7, 2021, when this image was captured, the Antarctic ozone hole spanned 24.8 million square km (9.6 million square miles).

The size of the Antarctic ozone hole varies from year to year primarily due to fluctuations in atmospheric temperatures and the dynamics of the polar vortex.1

The formation of the ozone hole is driven by chemical reactions that occur on the surfaces of particles within polar stratospheric clouds (PSCs). These clouds form only when temperatures in the lower stratosphere become extremely cold, a condition maintained by the polar vortex, which isolates the air over Antarctica during the winter.23

Because the strength and temperature of this vortex can differ annually, the extent to which PSCs form and facilitate the destruction of ozone also varies. Additionally, while the overall concentration of ozone-depleting substances like chlorine and bromine is a major factor in long-term trends, year-to-year changes in atmospheric composition and temperature continue to influence the specific size of the hole observed each spring.21