Stratospheric Climate Anomalies and Ozone Loss Caused by the Hunga Tonga‐Hunga Ha'apai Volcanic Eruption

Abstract

The Hunga Tonga‐Hunga Ha'apai (HTHH) volcanic eruption in January 2022 injected unprecedented amounts of water vapor (H2O) and a moderate amount of the aerosol precursor sulfur dioxide (SO2) into the Southern Hemisphere (SH) tropical stratosphere. The H2O and aerosol perturbations have persisted during 2022 and early 2023 and dispersed throughout the atmosphere. Observations show large‐scale SH stratospheric cooling, equatorward shift of the Antarctic polar vortex and slowing of the Brewer‐Dobson circulation. Satellite observations show substantial ozone reductions over SH winter midlatitudes that coincide with the largest circulation anomalies. Chemistry‐climate model simulations forced by realistic HTHH inputs of H2O and SO2 qualitatively reproduce the observed evolution of the H2O and aerosol plumes over the first year, and the model exhibits stratospheric cooling, circulation changes and ozone effects similar to observed behavior. The agreement demonstrates that the observed stratospheric changes are caused by the HTHH volcanic influences.

Stratospheric Temperature and Ozone Impacts of the Hunga Tonga‐Hunga Ha'apai Water Vapor Injection

“…MLS data show that lower stratospheric Antarctic ozone during spring 2022 was significantly lower than the 2005–2021 average (Figure 10d). Previous model results show that this low ozone could be explained by the HT aerosol perturbation combined with colder than average temperatures in the polar vortex (Wang et al., 2022). For the model simulations presented in this study, the SH planetary wave forcing (Appendix ) was reduced during winter‐spring 2022 to mimic the strong and isolated SH polar vortex that persisted well into November.…”

“…Ozone is affected by the HT water vapor anomaly globally throughout the middle atmosphere due to changes in photochemistry, both directly, and indirectly via changes in the temperature‐dependent ozone loss cycles (e.g., Brasseur & Solomon, 2005; Dvortsov & Solomon, 2001). MLS observations show that ozone in the mid stratosphere decreased significantly in the SH subtropics and midlatitudes starting in early winter 2022 (Santee et al., 2023; Wang et al., 2022). However, our model simulations suggest that the ozone response to the HT H 2 O anomaly in this region is quite small in 2022.…”

“…For the HT eruption, Wang et al. (2022) showed that significant additional ozone depletion occurred in the Antarctic lower stratosphere in spring 2022 when including the SO 2 injection in model simulations. Therefore, the ozone response to the H 2 O injection presented here likely somewhat underestimates the full response to the HT eruption, at least in the first year following the eruption.…”

Chemistry Contribution to Stratospheric Ozone Depletion After the Unprecedented Water‐Rich Hunga Tonga Eruption

“…MLS ozone concentration over 10°S-60°S show a record low relative to the climatology in the SH austral winter (Figure 1a, red line) at 30 hPa. Large midwinter interannual variability in this region is linked to the phase of the Quasi-Biennial Oscillation (QBO), as discussed in Wang et al (2023). MLS also shows a relatively deep ozone hole in the SH austral spring (Figure 1b) at 80 hPa.…”

The Chemical Effect of Increased Water Vapor From the Hunga Tonga‐Hunga Ha'apai Eruption on the Antarctic Ozone Hole

“…In addition to the effect on PSCs, changes in water vapor also cause changes in radiation, and in turn dynamical changes that could affect ozone (e.g., Schoeberl et al., 2022; Wang et al., 2023). However, we concentrate on the chemical changes in this study.…”