How does the Antarctic ozone hole form each spring?

The Antarctic ozone hole forms each spring due to a specific sequence of chemical and meteorological events isolated over the continent.1

During the polar winter, the circumpolar vortex—a strong jet of wind—isolates the air over Antarctica, causing temperatures to drop significantly. These extreme cold conditions facilitate the formation of polar stratospheric clouds (PSCs).1

Within these clouds, chemical reactions convert stable, less-reactive chlorine-containing molecules into highly reactive forms, such as molecular chlorine, which accumulate throughout the polar night. When sunlight returns to the region in early spring, it breaks these molecules into single chlorine atoms. These atoms then engage in a catalytic cycle that strips oxygen atoms from ozone molecules, leading to rapid ozone depletion. This destruction persists until the polar vortex breaks up, typically in November.1

While bromine also contributes to this process, the unique isolation provided by the Antarctic vortex is essential for the severity of the hole.1