The Influence of Stratospheric Hydration from the Hunga Eruption on Chemical Processing in the 2023 Antarctic Vortex

• Main Authors: Santee, Michelle L., Manney, Gloria L, Lambert, Alyn, Millan, Luis, Livesey, Nathaniel J, Pitts, Michael C., Froidevaux, Lucien, Read, William G., Fuller, Ryan
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2024
• Subjects: Antarctic; Midwinter; The Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.22541/essoar.170542085.55151307/v1

The 2022 Hunga eruption led to extraordinary water vapor enhancement throughout the stratospheric vortex at the beginning of the 2023 Antarctic winter. Although the dynamical characteristics of the vortex itself were generally unexceptional, the excess moisture initially raised the threshold temperatures for the formation of polar stratospheric clouds (PSCs) above typical values over a broad vertical domain. Low temperatures, especially during an early-July cold spell, prompted ice PSC formation and unusually severe irreversible dehydration at higher levels (500–700 K), while atypical rehydration occurred at lower levels (380–460 K). Heterogeneous chemical processing was more extensive, both vertically (up to 750–800 K) and temporally (earlier in the season), than in prior Antarctic winters. The resultant HCl depletion and ClO enhancement both redefined their previously observed ranges at and above 600 K. Albeit unmatched in the satellite record, the early-winter upper-level chlorine activation was insufficient to induce substantial ozone loss. Chlorine activation, denitrification, and dehydration processes saturated in midwinter, with trace gas evolution essentially following the climatological mean thereafter. Chlorine deactivation started slightly later than in most years. While cumulative ozone losses at 410–550 K were relatively large, probably because of the delayed chlorine deactivation, they were not unprecedented. Thus, ozone depletion was unremarkable throughout the lower stratosphere. Although Hunga hastened the onset of and increased the vertical extent of PSC formation and chlorine activation in early winter, saturation of lower stratospheric chemical processing (as is typical in the Antarctic) prevented an exceptionally severe ozone hole in 2023.