Ozone recovery effects on mesospheric dynamics in the southern hemisphere

Abstract. The recovery of Antarctic ozone, primarily driven by the Montreal Protocol, has significantly altered stratospheric circulation. However, its effects on the mesosphere and lower thermosphere (MLT) remain underexplored. Here, we use over a decade of meteor radar observations from Davis (68.6° S, 78.0° E), Rio Grande (53.7° S, 67.7° W), and Rothera (67– 68° S, 68° W), and whole-atmosphere model outputs (GAIA and SD-WACCM-X), complemented by satellite and reanalysis datasets, to assess trends in mesospheric winds. Our results reveal a significant delay in the spring transition from westerly to easterly zonal winds at approximately 82 km. This pattern coincides with changes in gravity wave momentum flux and stratospheric winds, suggesting a link between stratospheric ozone recovery and mesospheric dynamics. Comparisons with reanalysis datasets (MERRA2 and ERA5) further validate these findings despite their limited vertical extent and assimilated observations. Model comparisons reveal that, while both GAIA and SD-WACCM-X models have limitations in reproducing the basic climatology of the mesosphere, GAIA shows a somewhat better agreement with the observed trends. These results highlight the continuing effects of ozone recovery on upper atmospheric circulation and the need for improved representation of wave-driven coupling processes in climate models.