Analysis of Antarctic ozone trends from 1979 to 2023

Abstract. Antarctic ozone has shown a sustained recovery since 2000, but levels were distinctly low during 2020–2023, potentially affecting estimates of ozone recovery and long-term trends. To assess the impact of recent low ozone on long-term variability, we analyze total column ozone (TCO) data from World Ozone and Ultraviolet Radiation Centre, multi-sensor reanalysis, and Total Ozone Mapping Spectrometer/Ozone Monitoring Instrument. Ozone fields from TOMCAT, a 3-D chemical transport model, are also used to gain better insight ozone changes. Multiple linear regression (MLR) is applied to estimate ozone trends over Antarctica from 1979 to 2023, incorporating proxies representing key chemical and dynamical processes such as the El Niño-Southern Oscillation and the Brewer-Dobson circulation (BDC).

Our analysis suggests that before 2000, all datasets show significant declines in annual TCO of about 2 and 6 Dobson Units per year (DU/yr) for September and October, respectively. For the 2001–2023 period, the magnitude of the October trend shifted to −1.5 DU/yr. The MLR effectively captures long-term ozone changes as well as unusual dynamical events such as the sudden stratospheric warmings in 2002 and 2019. As dynamical proxies show the largest influence, we use TOMCAT simulations to illustrate the impact of the BDC on the Antarctic ozone. Two sensitivity simulations further demonstrate that the strengthening (weakening) of the circulation leads to high (low) ozone values in spring. These findings suggest that after ozone-depleting substances were strictly controlled, dynamical processes have played an increasingly important role in controlling the ozone recovery patterns in Antarctica.