the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 Jun 2026
The impact of the Hunga eruption on the 2023 Antarctic ozone hole: contrasting effects in the core and edge regions of the polar vortex
Abstract. The January 2022 Hunga eruption injected an exceptional 150 Tg of water vapour (H2O) into the stratosphere causing an enhancement not observed previously within the satellite era, with extensive and ongoing effects. From global chemical transport model simulations, we further assess the high-latitude H2O enhancement caused by the eruption, and how it influenced the 2023 Antarctic ozone depletion across two vortex regimes: the cold core and the less cold, and more insolated vortex edge region. Our simulations show the H2O chemical impacts arose mainly from the H2O enhancement promoting earlier formation of polar stratospheric clouds (PSCs), which in turn enhanced chlorine activation and subsequent ozone loss. We also show ice PSC dehydration in the vortex core limited Hunga’s chemical effects to occur for only the first 25 % of the vortex season; consequently, the edge region experienced the largest chemical impact to ozone depletion in 2023. Overall, the H2O enhancement increased Antarctic ozone hole area by 7 % but remaining within the historical variability over the past two decades. Sensitivity simulations including the Hunga sulfate aerosol show H2O-driven heterogeneous chlorine activation on additional PSCs, dominated the chemical impacts of Hunga on polar ozone, with only minor impact from activation on volcanic sulfate aerosol. Our results highlight that while water-rich large volcanic eruptions can worsen polar ozone depletion, the magnitude of the impact is strongly influenced by stratospheric temperatures through dehydration. This suggests that less cold vortex environments, e.g. the Arctic, may experience larger relative changes in chlorine activation under similar conditions.
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Status: open (until 31 Aug 2026)
- CC1: 'Community Comment on egusphere-2026-3619', Farahnaz Khosrawi, 12 Aug 2026 reply
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RC1: 'Comment on egusphere-2026-3619', Anonymous Referee #1, 27 Aug 2026
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The authors use model simulations to assess the influence of additional stratospheric water vapor and sulfate from the Hunga volcanic eruption on the 2023 Antarctic ozone hole. The colder core region and less cold edge vortex region are evaluated separately.
The topics covered are important and within the scope of ACP. This is not a transformative study, but the results have value and the analyses appear to have been carefully done. I support publication of this manuscript after addressing some concerns:
(1) The naming of the Simulations and Experiments in Table 1 and 2 are not at all intuitive, and it makes following the analyses in the paper significantly harder than it needs to be. Control_G, Clean, and Clean_H2O are essentially meaningless names. The simulations in Table 1 should be renamed so that the names are descriptive and clearly represent the perturbations that were done:
Control_G rename to: Aerosol only
Hunga_H2O rename to: H2O+Aerosol (or Combined)
Clean rename to: Background
Clean_H2O rename to: H2O only
I certainly would not insist that the authors use my exact suggestions if they have alternate ideas, but I do not support publication of this paper until the simulation names are changed to something more descriptive and intuitive than what they currently are.
The experiment labels in Table 2 are an additional naming complexity that is not necessary and makes the simple comparisons in the paper harder to follow. When simulations are subtracted from one another, the equation should be written out at each point in the manuscript (and actually almost always is in the current draft), so having a separate Table 2 defining “experiments” with ambiguous “Experiment labels” is not necessary and makes the paper less clear. I recommend deleting Table 2 and all mentions of the Experiment labels in the paper.
(2) Much of the paper is presented such that the reader is repeatedly asked to eyeball the colors in two similar figure panels, while the text qualitatively describes them in detail. I suggest that the authors consider making difference plots (e.g., Fig 3e minus Fig 3g, and others) as additional panels in the figures, which would make the differences immediately obvious and allow for a more quantitative approach and hopefully a more concise text description.
(3) The text is longer than necessary in many places. It would be ideal to have the text descriptions of the figures be more succinct, focus on the key points, and move the extra detail to supplemental. The paper has simple takeaway points and appears to be significantly longer than necessary.
Additional Comments/Corrections:
There are a good number of typos throughout. Please carefully go through it.
Line 9. Be clear whether this 7% result is from the model or measurements. Change ‘remaining’ to ‘remained’
Lines 17-18 and throughout. Use consistent date formats.
Line 22. Add ‘approximately’ before ‘150’.
Lines 74-75. Be more explicit regarding the wildfire impacts. Is it ‘including impacts’ or ‘due to impacts’?
Line 88. Change ‘particles both’ to ‘particles are’
Lines 92-94. Rewrite this unclear sentence.
Line 95. Add ‘a’ after ‘plays’
Line 194. ‘evaporate’ or ‘sublimate’?
Lines 195-203. This presentation of reactions seems unusual, particularly the Net HCl+NO2+2O3 reaction. Once ClO is formed in k3, by far the most likely fate is to self-react and form ClOOCl. ClO can also react with BrO. But as shown, k4 appears to be the only fate for ClO. An alternate approach to the current presentation, which I believe is far more common would be to change the presentation order to first list the reactions k1, k5, k6 as k1, k2, k3. After these het reactions are listed, rename k2 and k3 to be k4 and k5 to show the fate of the het reactions is to generate Cl atoms and cause O3 loss. The k4 reaction can become k6, and then delete the Net reaction.
Line 219. Define NRL.
Line 271. Fig 2d,e should be Fig 2c,e
Line 271. 25.55%: 4 significant figures are not warranted. Round to 26% here and other places this number is shown.
Section 4.2. Figures 3a-d are never called from the text.
Line 289. Delete ‘is’ before ‘promoting’
Line 297. Delete ‘occurs’
Figure 4. Remove the delta on the y-axis label for panels e-h
Line 333. Figs S5 and S6 are called here, but Figs S1, S2, S3, and S4 are never called from the main text.
Line 354. Add ‘as the core’ to the end of the sentence
Figure 6. If the MLS comparison figures for the chlorine species are going to be in the supplemental rather than the main paper, they need to be called from the main text. And the poor model agreement for ClO needs to be discussed.
Figure 7 caption. Change ‘millions’ to ‘million’ in the first line. Change ‘a area’ to ‘an area’ in line 4. Change ‘Panels (b)-(e)’ to ‘Panels (c)-(f)’
Line 411. It’s very hard to believe that 0.002 ppm is significant within uncertainty.
Figure 8. There are too many lines on panel a, such that it’s hard to distinguish them.
Lines 542-547. Be clear here that these are model results, not measurements. Although, some summary comparison with measurements in the Conclusions would be useful.
Conclusions. A number of previous related studies are mentioned on lines 31-38. I suggest adding some summary text in the Conclusions highlighting the core takeaways that are unique to the present study.
Citation: https://doi.org/10.5194/egusphere-2026-3619-RC1
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- 1
I have read your study with great interest and for me it was a very interesting and well done study of the impacts of the Hunga Tonga eruption on the Antarctic polar vortex in 2023. However, the manuscript in its current form is quite lengthy and would benefit from some shortening. Further, there are also a lot of small typos, especially obsolete spaces before commas and full stops, that should be removed before publication. There are also some other issues that could be improved to make the text and results presented more concise.
I will list in the following my comments and technical corrections:
General comments:
The figure main titles are rather obsolete since all information needed is provided in the caption and the text. The only titles that should be kept are core/edge and dates.
Using subsections for the introduction is rather unusual and I would suggest omitting these and trying to adjust the text flow that it will be one continuous text.
I would suggest to swap section 2 and 3, thus starting with the model and measurement data description and then describe the metrics. I also think it would be better to have both data and metrics in one “Method” section.
As mentioned above, the manuscript is quite lengthy and some shortening would make it much more concise.
The lines in the figures should be improved for better visibility, especially the PSC temperature threshold lines. I would suggest to use additional different colours or line thickness.
Figure 2, 4 and 7: The comparisons to MLS are quite nice and show the good agreement of the model simulation with the measurements. However, since this comparison is not the major focus of the study you may consider to move these figures to the supplement.
The summary and conclusions should be improved to be more concise and to provide a better statement on the implications of your results.
Specific comments:
P3, L89: In the classical classification using type Ia, Ib and II it was always assumed that type II forms homogeneously and consists of pure ice. Later it was found that ice can also form heterogeneously on NAT or on other small particles as e.g. meteoric dust. However, to be consistent at this place in the text with the classical PSC types I would suggest to write that ice is composed of H2O and NAT of HNO3 and H2O.
P4, L93: Lidar measurements and model simulations show that STS forms already when temperatures drop below 195 K. Note, the 195 K threshold is the NAT existence temperature, not the formation temperature. NAT forms usually at temperatures around 190 K (dependent on the formation process), but can exist up to 195 K.
P5, Fig. 1 caption: There is no red line. Please check the caption text and correct.
P6, L161: Here you could cite also other studies discussing the occurrence of ozone mini holes in the Arctic as e.g. the study by Hommel et al., ACP, https://doi.org/10.5194/acp-14-3247-2014 for the 2010/2011 winter.
P7, L179: I guess k1 to k6 refer to the reactions given below. However, at that place in the text this is not clear. A reference to the reactions given below is missing.
P7, L186: Not clear. Isn’t that a contradiction? Why can the HNO3 production contribute to denitrification?
P7, L194: Supported is not the correct wording here. Simply temperatures are too warm for the PSC particles so that these evaporate.
P7, 195ff: Add numbers for the reactions.
P8, L210: What exactly is meant with saturation threshold? You mean the saturation pressure? More explanations should be provided here to be more clear.
P8, L219: What is NRL? The abbreviation has not been introduced.
P8; L227: How has this given value for the fall velocity been derived? Has this been calculated or derived from a parameterisation?
P9, L240: delta_Water_Vapour denoted here as “simulations”, but not listed in Table 1. I guess you mean experiment instead of simulation.
P10, L273: Which band? Do you mean edge?
P13, L290: Not clear what you mean with slightly higher temperature thresholds.
P13, L308: In the Antarctic ice PSCs will rather consist of pure ice due to the very low temperatures and thus contribute mainly to dehydration. Even if they contain NAT, I am not sure if this will have a huge effect on denitrification. If there are studies showing that also ice PSCs containing NAT contribute to denitrification you should mention these here. Generally, I would suggest to phrase the sentences more carefully to be more precise and avoid misunderstandings.
Figure 5: Denitrfication/re-nitrification rather difficult to see. I would suggest to consider changing/adjusting the colour scale or adding boxes/circles to mark the respective areas.
P18, L383: Around which temperature fluctuations? You are not showing any temperatures.
P20, L440: Hunga report? I guess you mean here the APARC report on the Hunga Tonga eruption. You should be more precise here with the reference.
P25, L530: Sentence “For this purpose, the model predicted chemical impacts from the
Hunga H2O were analysed using an equivalent latitude co-ordinate system” not clear. Please rephrase.
P25, L552: Sentence “It is possible the edge could be used to assess the impact of a Hunga-like eruption in a warmer winter and is potentially transferable to the Arctic” not entirely clear and should be rephrased. Generally, I would also suggest to more clearly write here and throughout the manuscript “edge region” and “core region”, respectively, instead of just “edge” and “core”.
P29, Reference of Davies: Correct first name initials.
Technical corrections:
P4, L94: Add “a” -> Stratospheric H2O plays a key role
P7, L183: Change test to: ……sedimentation of the NAT particles and subsequent denitrification…
P8, L210: Ice -> ice
P8, L230: where model had fixed -> where the model had a fixed
P9, L240, K251: Remove space before full stop.
P9, L259: process -> processes
P10, L264: Remove space before full stop.
P12, Fig.3 caption: Remove obsolete spaces.
P12, L289: Either write “This is due to “that” the additional ……”or “This is due to the additional H2O promoting……”.
P13, L293 and 301: Replace “&” by “and”
P13, L297: Rephrase sentence, I think it rather should read “that occurs in the NAT extent”.
P14, L328: Add “the” so that it reads “Therefore, it is possible that ,,,,,,,” Sentence generally somewhat difficult to read. Consider rephrasing or splitting into two sentences.
P16, L335: Avoid separation of number and unit at the line break.
P17, Figure 6 caption: Replace “&” by “and”.
P18, L395: focussed -> focused, but I would rather suggest to replace focused by found.
P18, L396: Add “PSC” so that it reads “NAT PSC”.
P19, Figure 7 caption: Replace “&” by “and” (three occasions) and change “right is the edge” to “right is for the edge” or “right is shown the edge” .
P19, L404: Here you write zero, but in other occasions you use the number 0. The wrtting should be consistent throughout the manuscript.
P20, L425: hole -> holes
P21, L447: Remove obsolete space before comma.
P22, L449: Same here.
P22, L466: so can diagnose -> thus the model can diagnose
P22, L467: metrology -> meteorology
P22, L468: Add “simulations” so that it reads “both simulations with and without…..”.
P22, L479: has -> have
P22, L481: Add “increased” so that it reads “the increased H2O, stratospheric aerosol…….?
P23, Fig. 9 caption: Be more precise and write: The left column shows the core region and right column shows the edge region
P24, l490, 499 and 504: Remove obsolete space before comma.
P24, L498: Add space between “</>“ and “number”
P24, l500: Add “that” -> It is possible that….
P24, l502: Figure 9 -> Fig. 9
P24, L523: pyrocumubnimbus -> pyrocumulunimbus
References:
Hommel, R., Eichmann, K.-U., Aschmann, J., Bramstedt, K., Weber, M., von Savigny, C., Richter, A., Rozanov, A., Wittrock, F., Khosrawi, F., Bauer, R., and Burrows, J. P.: Chemical ozone loss and ozone mini-hole event during the Arctic winter 2010/2011 as observed by SCIAMACHY and GOME-2, Atmos. Chem. Phys., 14, 3247–3276, https://doi.org/10.5194/acp-14-3247-2014, 2014.