Why is ozone depletion most severe over Antarctica?

Ozone depletion is most severe over Antarctica due to unique meteorological conditions that facilitate the chemical destruction of ozone.

During the polar winter, the circumpolar vortex—a strong jet of wind—isolates the air over Antarctica, preventing it from mixing with warmer air from outside the region. This isolation leads to extremely cold temperatures, which allow for the formation of polar stratospheric clouds (PSCs).

These clouds provide a surface for chemical reactions that convert stable, less-reactive chlorine compounds into highly reactive forms. These reactive species accumulate throughout the dark winter months. When sunlight returns in the spring, it triggers the release of chlorine atoms, which then rapidly destroy ozone molecules. This process continues until the polar vortex breaks up, typically in November. While similar processes can occur in the Arctic, the northern polar vortex is generally warmer and less stable, meaning the conditions necessary for such extensive ozone loss are rarely sustained for as long as they are in the Antarctic.1