Large-scale drivers of Caucasus climate variability in meteorological records and Mt El'brus ice cores

Kozachek, Anna; Mikhalenko, Vladimir; Masson-Delmotte, Valérie; Ekaykin, Alexey; Ginot, Patrick; Kutuzov, Stanislav; Legrand, Michel; Lipenkov, Vladimir; Preunkert, Susanne

doi:https://doi.org/10.5194/cp-13-473-2017

Articles | Volume 13, issue 5

https://doi.org/10.5194/cp-13-473-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue:

International Partnerships in Ice Core Sciences (IPICS) Second...

https://doi.org/10.5194/cp-13-473-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 5

Research article

|

12 May 2017

Research article |

| 12 May 2017

Large-scale drivers of Caucasus climate variability in meteorological records and Mt El'brus ice cores

Anna Kozachek, Vladimir Mikhalenko, Valérie Masson-Delmotte, Alexey Ekaykin, Patrick Ginot, Stanislav Kutuzov, Michel Legrand, Vladimir Lipenkov, and Susanne Preunkert

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Final revised paper (published on 12 May 2017)
Supplement to the final revised paper
Preprint (discussion started on 28 Jun 2016)
Supplement to the preprint

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, 29 Jul 2016
RC2: 'Reviewer comment on Large-scale drivers of Caucasus climate variability in meteorological records and Mt Elbrus ice cores', Anonymous Referee #2, 27 Sep 2016
RC3: 'Earth Science', Anonymous Referee #3, 03 Oct 2016
AC1: 'Answers to the reviewers', Anna Kozachek, 31 Oct 2016
EC1: 'editor's comments', Shugui Hou, 01 Nov 2016

Peer-review completion

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

ED: Reconsider after major revisions (14 Nov 2016) by Shugui Hou

AR by Anna Kozachek on behalf of the Authors (22 Nov 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Nov 2016) by Shugui Hou

RR by Anonymous Referee #2 (07 Dec 2016)

Suggestions for revision or reasons for rejection

The authors have generally responded well to the comments and issues raised by the reviewers. However, I still have a major concern regarding this work, which is described below. I hope that the authors will make the effort to address this concern, and doing so, making the study a solid and interesting contribution to science.

Major comments.

In my opinion the authors have not addressed the issue raised by all three reviews with respect to the definition of the seasons of the d18O record. I find the division of the seasons quite problematic, and I fail to see the argument for choosing a fixed threshold. The division using the fixed threshold seems to be based on a 4-year study (L537-540 in revised version), which I think cannot be extrapolated to the whole record. Regardless of the record not having a strong long term trend, assuming a fixed threshold in d18O for dividing summer and winter seasons can create artifacts in the seasonal d18O data, due to for example decadal variability in the record. Think of for example a decadal minimum, using a fixed threshold between summer and winter values will proportionally assign more of the accumulation to the winter season creating a high-bias in the winter values – and vice versa for summer values. This will suppress the seasonal variability simply due to the definition of the seasons. I would argue that assigning 50% of accumulation to each season, even without investigating if this is realistic, is more scientifically sound than choosing a fixed threshold. Choosing a fixed proportion per season might create an overall bias if the proportion is not correct, but the bias should be less variable in time compared with a fixed threshold.

I urge the authors to carefully read section 3.3 in Vinther et al. 2010 and adopt a similar line of thinking – if not adopting a similar approach to dividing the seasons.

Minor comments.

I can't find any references to which data is used for NAO, AO and AMO. Please make sure to check all references for data used and describe the climate indecies in the data section, including definitions and data sources.

References

Vinther, B., P. Jones, K. Briffa, H. Clausen, K. Andersen, D. Dahl‐Jensen,
and S. Johnsen (2010), Climatic signals in multiple highly resolved stable
isotope records from Greenland, Quat. Sci. Rev., 29(3‐4), 522–538,
doi:10.1016/j.quascirev.2009.11.002.

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RR by Anonymous Referee #4 (13 Dec 2016)

ED: Reconsider after major revisions (15 Dec 2016) by Shugui Hou

AR by Anna Kozachek on behalf of the Authors (20 Jan 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Jan 2017) by Shugui Hou

RR by Anonymous Referee #2 (01 Feb 2017)

Suggestions for revision or reasons for rejection

Review of “Large-scale drivers of Caucasus climate variability in meteorological records and Mt Elbrus ice cores” by Kozachek et al.

This is a review of the 2nd revision of this study by Kozachek et al., and I was also reviewer of the original version and the 1st revision. I appreciate the authors efforts into investigating the seasonal devision of the ice core data and the manuscript has generally improved a lot, although I still struggle a bit to understand how exactly the seasons are defined in this new version. However, it is clear that the variability changes a lot depending on the definition of the the seasons and that the new definitions have greater decadal variability.
If the authors address the (minor) points in the comments below I think the manuscript could be accepted for publication.

Detailed comments.

L22 “allowed” changed to “allows”?

L23 Remove extra punctuation mark after “shallow cores”.

L78-79 The potential for reconstructing the NAO using Greenland ice cores was suggested by Vinther et al. (2003) rather than proven. They show that the relation between the NAO and the main variability of the Greenland d18O from ice cores is not stable.

L158 “18” should be superscript in d18O. Check for other instances. For example in L172, L332, L333 and L416.

L171-172 I don't understand what you mean here: “We changed the borders between the
seasons when needed in order to avoid ascribing minimum of δ18O to the warm season and maximum to the cold season”. In Figure 4 of Vinther et al. (2010) warm and cold season is defined similarly as in your Figure 3? Vinther et al. performed a correlation analysis to define the extent of the seasons. How did you do this? How much accumulation was assigned to each season?

L173 “We stacked ...” you stacked the ice core data? And you assign the maximum and minimum to the center of the warm and cold season, respectively? This sentence is not clear.

L177-178 What is the motivation for this definition of warm and cold seasons?

L183 “We didn't ...” the use of contractions is in general too informal for academic writing. Check for other instances. For example in L372.

L228 Consider using the PC-based NAO index, although it doesn't make much of a difference during winter. See https://climatedataguide.ucar.edu/climate-data/hurrell-north-atlantic-oscillation-nao-index-pc-based

L264-265 The definition of summer and winter is generally done using temperature, or one might talk of dry and wet seasons if summer and winter doesn't exist. Think of southern versus northern hemisphere. Use months to define the seasons in relation to temperature.

L420 Remove punctuation mark.

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RR by Anonymous Referee #4 (24 Feb 2017)

ED: Reconsider after major revisions (25 Feb 2017) by Shugui Hou

AR by Anna Kozachek on behalf of the Authors (22 Mar 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Mar 2017) by Shugui Hou

RR by Anonymous Referee #4 (11 Apr 2017)

ED: Publish subject to minor revisions (review by Editor) (11 Apr 2017) by Shugui Hou

AR by Anna Kozachek on behalf of the Authors (17 Apr 2017) Author's response Manuscript

ED: Publish as is (18 Apr 2017) by Shugui Hou

AR by Anna Kozachek on behalf of the Authors (18 Apr 2017) Manuscript