Multi-model assessment of impacts of the 2022 Hunga eruption on stratospheric ozone and its chemical and dynamical drivers

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Abstract. The 2022 Hunga eruption injected unprecedented quantities of water vapor into the stratosphere, alongside modest amounts of aerosol precursors. There remain uncertainties regarding the extent to which it influenced the stratospheric ozone layer. We address this using a multi-model ensemble of chemistry-climate model simulations, assessing the impacts of Hunga-induced perturbations in both water vapor and aerosol by combining free-running and specified-dynamics experiments. The results confirm that the Hunga eruption contributed to the anomalously low ozone abundances observed in the southern mid-latitudes in 2022. The simulations also indicate enhanced ozone depletion inside the Antarctic polar vortex, albeit with significant differences in magnitude and persistence across the models. Our results indicate that the chemical contribution was as important as the dynamical contribution in determining the overall ozone response to the Hunga eruption in the southern extra-tropics, with anomalous chemical (chlorine, bromine and nitrogen) processing on aerosol surfaces under conditions of water-induced stratospheric cooling together with dynamical contributions from altered circulation and ozone transport. Finally, while Hunga may continue to exert a smaller influence on ozone as the anomalous water vapor and aerosol is removed from the atmosphere, natural dynamical variability will likely hinder detection of any such influences, with the most robust Hunga signal expected in the upper stratosphere. Our study confirms the eruption’s role in modulating stratospheric ozone levels in the short term, but also highlights the associated uncertainties and the presence of large natural variability, all of which makes confident attribution of the Hunga impacts an ongoing challenge.

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