| Summary: | The Antarctic polar vortex creates unique chemical and dynamic conditions when the stratospheric air over Antarctica is isolated from the rest of the stratosphere. As a result, stratospheric ozone within the vortex remains largely unchanged for a five-month period from April until late August when the sunrise and extremely cold temperatures create favorable conditions for rapid ozone loss. Such prolong stable conditions within the vortex make it possible to estimate the ozone levels there from sparse wintertime ozone observations at the South Pole. Total ozone measurements by Dobson and Brewer spectrophotometers that use the Moon as the light source, integrated ozonesonde profiles, and MERRA-2 reanalysis data were used to analyse ozone variability and trends over the South Pole. The wintertime ozone values over the South Pole during the last 20 years were 12%–15% below the pre-1980 level, i.e., the decline there was nearly twice larger than that over southern midlatitudes. It is probably the largest long-term ozone decline aside from the springtime Antarctic ozone depletion. While wintertime ozone decline over the pole hardly has any impact on the environment, it can be used as an indicator to diagnose the state of the ozone layer, particularly because it requires data only from one station. Data after 2004 show a small positive trend, although it is not statistically significant. Total ozone variability over the South Pole and observation uncertainties will be also discussed.
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