Contrasting austral summer Southern Hemisphere circulation trends before and after the recovery of Antarctic stratospheric ozone

This is the authors' abstract. We don't add key points for this paper.

Antarctic stratospheric ozone depletion drove pronounced changes in Southern Hemisphere (SH) austral summer circulation in the late 20th century, while its recovery since the early 2000s has been accompanied by a slowdown of these trends. Utilizing ERA5 and JRA-55 data, this study examines the spatial characteristics and statistical robustness of these trend shifts. Results indicate that ozone recovery is associated with lower-to-middle stratospheric warming, accompanied by a weakening of tropospheric circulation anomalies. This weakening is spatially non-uniform, being most pronounced over the South Pacific. To quantify changes in SH summer circulation, we analyze five metrics: the Southern Annular Mode (SAM), westerly jet position, westerly jet strength, the Hadley Cell (HC) edge, and HC strength. The first four show a deceleration in the strengthening trends since the onset of ozone recovery, although their statistical significance varies. The most robust change occurs in the SAM index, from 2.03 to 1.27 hPa (10 yr) −1 , passing the Chow test at the 97.3% confidence level. In contrast, the HC edge shift shows the largest trend reduction but the weakest significance. Moreover, during 2000–2023, rolling trends fluctuate around zero and become less sensitive to extremes, indicating increased robustness of the weakened circulation anomalies.