Future volcanic eruptions may delay the recovery of lower stratospheric ozone over Antarctica and Southern Hemisphere mid-latitudes

Abstract. Sporadic explosive volcanic eruptions can inject large amounts of sulfur into the stratosphere, which forms volcanic sulfate aerosols with the potential to affect stratospheric ozone chemistry. Future volcanic eruptions have been represented in climate projection studies with varying degrees of realism despite their potential importance for polar ozone recovery. Climate projections typically use a constant volcanic forcing based on a historical average, which very likely underestimates the magnitude of future volcanic forcing and ignores the sporadic nature of volcanic eruptions. In this study, we use stochastic volcanic eruption scenarios and a plume-aerosol-chemistry-climate model (UKESM-VPLUME) to assess the effect of future volcanic sulfur injections on lower stratospheric ozone recovery over Antarctica and Southern Hemisphere mid-latitudes. We find that sporadic eruptions can delay Antarctic total column ozone recovery by up to five years, though this delay is relatively small when compared with the long-term ozone recovery timescale. Large-magnitude eruptions occurring before mid-century can, however, episodically cause more substantial delays in the recovery. Based on a composite analysis we show that the ozone response to volcanic sulfate aerosols over Antarctica and Southern Hemisphere mid-latitudes weakens over the 21st century due to declining chlorofluorocarbon concentrations. Overall, our findings underscore the need for fully interactive volcanic aerosol-chemistry coupling to assess the resilience of the Antarctic ozone layer in response to future volcanic eruptions and other stratospheric perturbation events. Our results also support previous calls for sustained monitoring of stratospheric composition and ozone-depleting processes to better anticipate and attribute changes in ozone recovery.