Antarctic Vortex Dehydration in 2023 as a Substantial Removal Pathway for Hunga Tonga‐Hunga Ha'apai Water Vapor

The January 2022 eruption of Hunga Tonga-Hunga Ha'apai (HTHH) injected a huge amount (∼150 Tg) of water vapor (H₂O) into the stratosphere, along with small amount of SO₂. An off-line 3-D chemical transport model (CTM) successfully reproduces the spread of the injected H₂O through October 2023 as observed by the Microwave Limb Sounder. Dehydration in the 2023 Antarctic polar vortex caused the first substantial (∼20 Tg) removal of HTHH H₂O from the stratosphere. The CTM indicates that this process will dominate removal of HTHH H₂O for the coming years, giving an overall e-folding timescale of 4 years; around 25 Tg of the injected H₂O is predicted to still remain in the stratosphere by 2030. Following relatively low Antarctic column ozone in midwinter 2023 due to transport effects, additional springtime depletion due to H₂O-related chemistry was small and maximized at the vortex edge (10 DU in column).