Decadal Analysis of Antarctic Ozone Depletion: Seasonal Evolution and Signs of Recovery

The Antarctic ozone hole is a severe depletion phenomenon that has occurred every austral spring since the early 1980s. Its severity depends on ozone-depleting substances (ODSs) and lower stratospheric meteorological conditions. This study examines the structure and seasonal evolution of the ozone hole over the past decade using satellite observations (Aura MLS, OMI; SNPP OMPS; CALIPSO), ground-based measurements (South Pole sondes), and reanalysis data (MERRA-2).

The August-September period is critical for Antarctic ozone depletion as sunlight returns to polar latitudes, activating heterogeneous reactions on surfaces of polar stratospheric clouds (PSC) to release chlorine into reactive forms. Effective equivalent stratospheric chlorine (EESC)—a proxy of anthropogenic and natural ODSs in the stratosphere—has decreased by about 15% since its peak in 2000 due to the Montreal Protocol agreement. Despite lower ODS levels, year-to-year ozone variability has been primarily influenced by stratospheric temperatures. Stratospheric temperature variations (e.g., between 2019 and 2020) complicate the link between ODS reductions and changes in hole severity metrics. However, recent years have shown smaller levels of active chlorine and seasonal ozone losses compared to 2006, reflecting the Montreal Protocol's impact and signaling ozone recovery. The delayed onset of the ozone hole in recent years also supports this recovery.

The late ozone hole breakups observed in 2020-2023 can be attributed to weak planetary wave activity during austral spring, which kept stratospheric temperatures lower than average and hindered the transport of ozone-rich air from mid-latitudes. A strong correlation was found between ozone hole breakup dates and vortex breakup dates from 1990 to the present. Additionally, we will explore the impact of excess water vapor from the 2022 Hunga eruption on Antarctic ozone holes from 2022 to 2024.