Siberian tree-ring and stable isotope proxies as indicators of temperature and moisture changes after major stratospheric volcanic eruptions

Churakova (Sidorova), Olga V.; Fonti, Marina V.; Saurer, Matthias; Guillet, Sébastien; Corona, Christophe; Fonti, Patrick; Myglan, Vladimir S.; Kirdyanov, Alexander V.; Naumova, Oksana V.; Ovchinnikov, Dmitriy V.; Shashkin, Alexander V.; Panyushkina, Irina P.; Büntgen, Ulf; Hughes, Malcolm K.; Vaganov, Eugene A.; Siegwolf, Rolf T. W.; Stoffel, Markus

doi:https://doi.org/10.5194/cp-15-685-2019

Articles | Volume 15, issue 2

https://doi.org/10.5194/cp-15-685-2019

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

https://doi.org/10.5194/cp-15-685-2019

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

Articles | Volume 15, issue 2

Research article

|

05 Apr 2019

Research article |

| 05 Apr 2019

Siberian tree-ring and stable isotope proxies as indicators of temperature and moisture changes after major stratospheric volcanic eruptions

Olga V. Churakova (Sidorova), Marina V. Fonti, Matthias Saurer, Sébastien Guillet, Christophe Corona, Patrick Fonti, Vladimir S. Myglan, Alexander V. Kirdyanov, Oksana V. Naumova, Dmitriy V. Ovchinnikov, Alexander V. Shashkin, Irina P. Panyushkina, Ulf Büntgen, Malcolm K. Hughes, Eugene A. Vaganov, Rolf T. W. Siegwolf, and Markus Stoffel

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Final revised paper (published on 05 Apr 2019)
Supplement to the final revised paper
Preprint (discussion started on 27 Jun 2018)
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: 'Review of Churakova et al. "Heterogeneous response of Siberian tree-ring and stable isotope proxies to the largest Common Era volcanic eruptions" for Climate of the Past Discussions', Anonymous Referee #1, 27 Jul 2018
- AC1: 'Response to the Anonymous Referee #1', Olga Churakova (Sidorova), 06 Oct 2018
RC2: 'Reviewer's Comments', Anonymous Referee #2, 29 Aug 2018
- AC2: 'Response to the Anonymous Referee #2', Olga Churakova (Sidorova), 06 Oct 2018

Peer-review completion

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

ED: Reconsider after major revisions (06 Oct 2018) by Jürg Luterbacher

AR by Olga Churakova (Sidorova) on behalf of the Authors (07 Oct 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (09 Oct 2018) by Jürg Luterbacher

RR by Anonymous Referee #2 (28 Oct 2018)

RR by Anonymous Referee #1 (12 Nov 2018)

Suggestions for revision or reasons for rejection

Review of revised manuscript by Churakova et al. "Siberian tree-ring and stable isotope proxies as indicators of temperature and moisture changes after major stratospheric volcanic eruptions" (revised title) for Climate of the Past Discussions

As with my original review, I am supportive of this study because of its value in bringing together multiple tree-parameters and to infer multiple climatic parameters. My criticisms arose from the lack of a superposed epoch analysis (SEA), a focus on the heterogeneity of responses to different eruptions which hadn't been firmly established, and incorrect discussion of how the results from various poor quality figures had been described in the main text.

I am pleased that the authors have addressed many of my previous concerns. However there are still many problems with the manuscript. Individually, these are minor and could be easily addressed by the authors. Most are still about incorrect discussion of the results in the text that does not always match the values shown in the figures (the figures are improved, thank you). I'm annoyed that a whole section of my original review was ignored and not responded to, since some of these errors I had already highlighted and now I found them all over again!

Here is the section of my original review that was ignored (nothing mentioned in the authors' response). Of course the line numbers refer to the lines in the original 'discussions' manuscript. I repeat some of them later for the new manuscript but all the original ones should be checked anyway.

=======
These limitations are compounded by errors in the description of the results in Fig. 4.
Here are lines 439-449 with my comments in [CAPS]:

———– "Therefore, CE 536 was extremely humid in YAK and TAY, as well as 541 and
542 [NOTHING SIGNIFICANT IN FIG 4 IN 542] in TAY and ALT. CE 1258 was dry in
YAK and ALT, while drier than normal conditions occurred in 1259 for all studied sites.
CE 1641 [1641 ISN’T EVEN IN FIG 4] was dry in TAY; 1642 in YAK [NO, 1643!] and ALT
[NOT ACCORDING TO FIG 4]. A rather wet summer was in TAY during 1815 [THIS
YEAR IS NOT IN THE FIGURE!] and 1816 years [NOTHING SIGNIFICANT HERE].
CE 1991 [NOT IN THE FIGURE!] was wet in YAK, 1992 in ALT [NO ALT DOESN’T
APPEAR WET IN 1995 IN FIG 4] followed by a dry summer in 1993 [NOT ACCORDING
TO FIG 4!] (Fig. 4).

3.3.3. Sunshine duration proxies Instrumental measurements of sunshine duration
(Table 2) in YAK and ALT during the recent period showed a significant link with
δ18O cellulose. Based on this we conclude that sunshine duration decreased significantly in
536, 541, 542, 1258 and 1259 in YAK, and 536 in ALT. Conversely, summer 1991 in
YAK was very sunny [NOT ACCORDING TO FIG 4! BUT 1993 in ALT WAS, WHY NOT
MENTION THIS?] (Fig. 4)." ———–

For Pinatubo, the instrumental data could be used to confirm the multi-variate explana-
tions, e.g. do they confirm the statements you give about 1991-1993 on lines 442-443,
449 and 517?

Some description of Fig. 3 looks incorrect too, e.g. identification of months with significant correlations:

L370: "with the exception of TAY for the latter" - and CWT too? L381: "May" - looks like
"April"? L391: "March" - looks like "April" for CWT?
=======

Specific comments for the revised manuscript follow.

Title is improved, good.

L77: 0.5C cooling is for NH land cooling not global cooling.

L176: this says these events are VEI>6, but L136 says VEI exceeding 5. Table 1 has one with VEI=5 (Parker). Please be consistent, or if VEI was not the criteria for selection than don't say that it was. I understand that you've already made the selection and made the measurements, so I am not suggesting you make a different selection I'm just asking that you be consistent in stating how the selection was made. It doesn't matter if there is not a simple rule (VEI or something else). It is fine if you selected the largest plus Parker for another reason (data/samples were available, etc.) just say it.

L228-231: "the remaining YAK sample size was too small" Should YAK be replaced by "TAY"? Otherwise I don't see how the YAK sample size causes the TAY 536 CWT value to be missing. Perhaps these sentences would be more clearly written as:
"Unfortunately the remaining sample material for the CE 536 ring at TAY was insufficient to produce a clear anatomical signal. As a result, CWT is missing for CE 536 at TAY (Fig. 2)"

L240: Should it say "(g/cm3)"?

Various anomalies are discussed in the results section. These do not always match the values shown in the figures, suggesting that you have not checked the values very carefully. This isn't helped by using incompatible colours in Fig. 2 and in Fig. S1 for TRW (pink vs. black) and MXD (black vs. purple). Some examples:

L317-318: You have added a sentence that is not supported by Fig. 2 or Fig. S1 ("Regarding CWT, a strong decrease is observed in CE 536 at YAK.").

L321-322: MXD for YAK is not -2.8 sigma in CE 537 in Fig. 2. Maybe you mean 536 for YAK and 537 for ALT?

L325-326: This sentence is not supported by the figures:
"The δ18O chronologies show a distinct decrease one year after the eruptions for YAK -3.9 σ, in the year of 1259, TAY -3.0σ in 537, and ALT -2.9 σ in 537 only (Fig. 2, Fig. S1)."
First, 1259 and 537 are not ONE year after an eruption. Second, ALT extreme is in 536 not 537.

L347-348: "No extreme anomalies are observed in CE 1816 in Siberia regardless of the site and the tree-ring parameter analyzed." Even if this is correct for your particular definition of "extreme" (lower 10th percentile) it is nevertheless worth noting that MXD at YAK does reach about -2.5 sigma in 1816, otherwise this sentence may be misinterpreted by readers. Also, I'm not sure it is correct: is -2.5 sigma really not in the lower 10th percentile (as shown in Fig. S1 for 1816 YAK). This would imply a very non-normal distribution which seems unlikely from Fig. S1 1816 YAK. Also, this does not agree with Fig. 2 of the main paper, where TRW (pink) is not less than -1 sigma, yet in Fig. S1 1816 YAK the TRW (now black) is -2.3 sigma. Also MXD is -2.5 sigma (black in Fig. 2) but -2 sigma (purple in Fig. S1). This all needs careful checking and perhaps correcting -- and perhaps Fig. 5 may also then need correcting to show cool anomalies for YAK in 1816 for either MXD or TRW depending on whether fig. 2 or fig. S1 is the correct one.

Fig. 3: it is good to now see an SEA analysis. However it's value is limited by two aspects:

(1) by overlaying composites for the three sites means it is unclear what some of the values are (e.g. MXD in eruption+1 is negative for ALT and YAK but no idea what the TAY value is as there is no red bar; for eruption+2 ony the green bar is visible; etc.).

(2) no significance levels are shown -- a key advantage of SEA is that the anomaies can be tested against a null hypothesis that there is no volcanic signal. One brief mention of a statistical test is given in the text (L357-359) though it is unclear what is being averaged over. If it isn't possible to perform a statistical test of the SEA results then this should be clearly stated (e.g. because only selected years have been measured for some variables, rather than full timeseries) though I think this would only weaken the power of a test rather than prevent any test being performed.

L389-391: The results described do not seem to match those shown in Fig. 4 for d18O. There are no red bars for the months discussed at YAK and TAY. There are some for ALT but they don't appear to be in February and March.

Fig. 5 is a very nicely designed summary. However the text describing it is not always consistent:

L451-452: "Therefore, CE 536 was extremely humid in YAK and TAY, as well as 541 and 542 in TAY and ALT." The only coloured symbols in Fig. 5 for CE 542 are indicators or temperature or sunshine. How can you say it was extremely humid then?

L452-453: "CE 1258 was dry in YAK and ALT, while drier than normal conditions occurred in 1259 for all studied sites." Dry? Then why do you have purple circles in Fig. 5 indicating low vapour pressure deficits? Sure low VPD means wet?

L453: "CE 1641 was dry in TAY; 1642 in YAK and ALT" -- but 1641 is not shown in Fig. 5. Why not? And 1642 has no coloured symbols to mark moisture at all.

[I just realised that many of these were in my original review and have been ignored by the authors. They have not included any of these comments in their "author response" and now I have spent my time reporting the same errors for a second time!]

Fig. 2: I would recommend adding a vertical black line at CE 540, as currently this eruption is not marked in Fig. 2 but all the others are.

SM: Much clearer now. The figure caption has disappeared, however. Despite the authors' claim, they still don't show superposed epoch analyses since all years are shown separately rather than superposed to obtain a composite. But an SEA has been included in the main figure 3.

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ED: Reconsider after major revisions (12 Nov 2018) by Jürg Luterbacher

AR by Olga Churakova (Sidorova) on behalf of the Authors (01 Dec 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Dec 2018) by Jürg Luterbacher

RR by Anonymous Referee #1 (05 Dec 2018)

ED: Reconsider after major revisions (15 Dec 2018) by Jürg Luterbacher

AR by Olga Churakova (Sidorova) on behalf of the Authors (19 Jan 2019)

ED: Referee Nomination & Report Request started (03 Feb 2019) by Jürg Luterbacher

RR by Anonymous Referee #1 (03 Mar 2019)

ED: Publish as is (05 Mar 2019) by Jürg Luterbacher

AR by Olga Churakova (Sidorova) on behalf of the Authors (06 Mar 2019) Manuscript

Short summary

We present a unique dataset of multiple tree-ring and stable isotope parameters, representing temperature-sensitive Siberian ecotones, to assess climatic impacts after six large stratospheric volcanic eruptions at 535, 540, 1257, 1640, 1815, and 1991 CE. Besides the well-documented effects of temperature derived from tree-ring width and latewood density, stable carbon and oxygen isotopes in tree-ring cellulose provide information about moisture and sunshine duration changes after the events.