Influence of Arctic stratospheric ozone on surface climate in CCMI models

Harari, Ohad; Garfinkel, Chaim I.; Ziskin Ziv, Shlomi; Morgenstern, Olaf; Zeng, Guang; Tilmes, Simone; Kinnison, Douglas; Deushi, Makoto; Jöckel, Patrick; Pozzer, Andrea; O'Connor, Fiona M.; Davis, Sean

doi:https://doi.org/10.5194/acp-19-9253-2019

Articles | Volume 19, issue 14

https://doi.org/10.5194/acp-19-9253-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Chemistry–Climate Modelling Initiative (CCMI) (ACP/AMT/ESSD/GMD...

https://doi.org/10.5194/acp-19-9253-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 14

Research article

|

19 Jul 2019

Research article |

| 19 Jul 2019

Influence of Arctic stratospheric ozone on surface climate in CCMI models

Ohad Harari, Chaim I. Garfinkel, Shlomi Ziskin Ziv, Olaf Morgenstern, Guang Zeng, Simone Tilmes, Douglas Kinnison, Makoto Deushi, Patrick Jöckel, Andrea Pozzer, Fiona M. O'Connor, and Sean Davis

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Final revised paper (published on 19 Jul 2019)
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Preprint (discussion started on 23 Oct 2018)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Referee comment', Anonymous Referee #1, 12 Nov 2018
- SC1: 'response to major comments of reviewer 1', Chaim Garfinkel, 02 Dec 2018
- AC2: 'response to reviewer 1', Ohad Harari, 29 Jan 2019
RC2: 'Reviewer Comments', Anonymous Referee #2, 21 Nov 2018
- AC1: 'response to reviewer 2', Ohad Harari, 29 Jan 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Ohad Harari on behalf of the Authors (25 Feb 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (20 Mar 2019) by Paul Young

RR by Anonymous Referee #2 (02 Apr 2019)

RR by Anonymous Referee #1 (06 Apr 2019)

Suggestions for revision or reasons for rejection

The authors addressed some of the criticism and overall the manuscript has somewhat improved since the previous version. I am still not convinced that the manuscript represents a significant advance in science however I do appreciate author’s efforts to disentangle statistical links between Arctic stratospheric ozone and surface climate. Below I add some comments; hopefully the authors find them useful for further improvement of the manuscript.

First, contrary to what the authors assert, I don’t believe the connection between Arctic ozone and surface climate is “settled science”; I simply don’t think the authors approach this problem from the right perspective. In Calvo et al they did demonstrate that, as ozone variability increased from low Ozone Depleting Substances (ODS) period to high ODS period, this was followed by increased stratospheric cooling and stronger changes in surface climate. While their study may have caveats, for example because they only use one model, they could however with reasonable confidence attribute their surface climate response during the second period to increased stratospheric variability caused by increased ODS and low ozone. I don’t think they assumed a direct ozone-surface link because they carefully documented responses of zonal mean temperatures and winds consistent with the dynamical stratosphere-troposphere coupling, although they might have discussed the mechanism in a more clear way.

I also don’t see how the authors of the present manuscript addressed the statement from Ozone assessment, which they cite. It is well-established that extreme low ozone values, observed during some winters in the Arctic, are a result of chemical depletion, rather that stratospheric dynamics alone, see for example Manney et al. 2011. Thus, based on Calvo et al results, surface anomalies that follow low ozone episodes may be attributable to chemical ozone depletion. While the ozone assessment statement does not mention any mechanism, it is certainly consistent with stratosphere-troposphere dynamical coupling similar to what is apparently operating in the Antarctic. Thus I don’t see how the authors “explored the robustness” of the statement in the ozone assessment.
In summary, while I find that the part of the study concerning ASO-ENSO link has improved and is worth reporting, I still don’t find that the part concerning links between ASO and polar surface climate is equally exciting. Below are my suggestions:
1. The authors find strikingly large differences in ozone-climate coupling even between simulations by the same model. In Calvo et al they find similarly large differences in coupling between two periods when ozone was / was not depleted. During ozone depletion period the ozone variability was twice as large, owing to extreme low ozone events. This was linked to larger signal in stratospheric temperatures and thus in surface climate. I suggest that the authors test whether the spread shown in Figures 4 and 6 can similarly be attributed to different interannual variability between these periods. Specifically, do you see larger interannual variability in ozone (measured e.g. by interannual standard deviation) during years when ozone-climate coupling is larger? One could expect stronger coupling when there is larger variability, due to increased signal to noise ratio.
2. Further, can the authors attribute stronger coupling (and possibly larger variability) to different ozone levels and thus possibly to chemistry? The authors showed how the coupling changes between different periods (1970-2010, 2011-2051, 2052-2092) but it is difficult to understand their result without knowing what ozone values were during these runs. Is there, for example, any indication of chemical ozone depletion in those runs? One could test correlation coefficients against minimum ozone values achieved in those runs. I also wonder what could be the cause for seemingly stronger coupling during some future runs (2052-2092). One could imagine that there are still episodes of chemical ozone depletions that, combined with increased Brewer-Dobson circulation in future, would lead to larger variability and stronger coupling. I guess negative answer to these questions would indeed indicate that the variability in coupling is due to internal variability, as the authors assert, but the tests proposed above could still give more insights.
I appreciate large amount of work that authors put into the study but I nevertheless don’t find that the manuscript is complete without this additional (and rather straightforward) analysis.

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ED: Reconsider after major revisions (23 Apr 2019) by Paul Young

AR by Ohad Harari on behalf of the Authors (02 Jun 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Jun 2019) by Paul Young

RR by Anonymous Referee #1 (24 Jun 2019)

ED: Publish subject to technical corrections (24 Jun 2019) by Paul Young

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Short summary

Ozone depletion in the Antarctic has been shown to influence surface conditions, but the effects of ozone depletion in the Arctic on surface climate are unclear. We show that Arctic ozone does influence surface climate in both polar regions and tropical regions, though the proximate cause of these surface impacts is not yet clear.