High-latitude Southern Hemisphere fire history during the mid- to late Holocene (6000–750&thinsp;BP)

Battistel, Dario; Kehrwald, Natalie M.; Zennaro, Piero; Pellegrino, Giuseppe; Barbaro, Elena; Zangrando, Roberta; Pedeli, Xanthi X.; Varin, Cristiano; Spolaor, Andrea; Vallelonga, Paul T.; Gambaro, Andrea; Barbante, Carlo

doi:https://doi.org/10.5194/cp-14-871-2018

Articles | Volume 14, issue 6

Clim. Past, 14, 871–886, 2018

https://doi.org/10.5194/cp-14-871-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Clim. Past, 14, 871–886, 2018

https://doi.org/10.5194/cp-14-871-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 6

Research article 21 Jun 2018

Research article | 21 Jun 2018

High-latitude Southern Hemisphere fire history during the mid- to late Holocene (6000–750 BP)

Dario Battistel et al.

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Final revised paper (published on 21 Jun 2018)
Supplement to the final revised paper
Preprint (discussion started on 21 Dec 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'reviewer comments', Anonymous Referee #1, 05 Feb 2018
- AC3: 'Reply to RC 1', Dario Battistel, 22 Mar 2018
RC2: 'Revirew of High latitude Southern Hemisphere fire history during the Mid-Late Holocene (750- 6000 yr BP)', Anonymous Referee #2, 09 Feb 2018
- AC2: 'reply to RC2', Dario Battistel, 22 Mar 2018
EC1: 'Editorial comment', Eric Wolff, 16 Feb 2018
- AC1: 'Reply to Editor', Dario Battistel, 22 Mar 2018
- AC4: 'revised paper', Dario Battistel, 22 Mar 2018

Peer-review completion

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

ED: Reconsider after major revisions (29 Mar 2018) by Eric Wolff

AR by Anna Wenzel on behalf of the Authors (20 Apr 2018) Author's response

ED: Referee Nomination & Report Request started (27 Apr 2018) by Eric Wolff

RR by Anonymous Referee #1 (07 May 2018)

RR by Anonymous Referee #2 (18 May 2018)

Suggestions for revision or reasons for rejection

Overall I think this revision is a much stronger version. I have outlined a few major and minor comments for the authors to consider.

Major:
Page 7 line 35: I do not think this paragraph accurately reflects the Kbb profile observed. Rather I would describe the Kbb profile as showing an increase beginning at 4ka to level but fluctuating values from 3.5 to 1.25 ka, followed by an increase from 1.25 to .75 ka.
Page 7 line 35 to page 8 line 9: I still encourage the authors to avoid discussion of individual spikes in the records. Considering that very few of the spikes in the Kbb and Levoglucosan record agree, I do not see the added value of the discussion on Page 7 lines 35-page 8 line 9. I think the authors should shorten this discussion and lead directly into the following paragraph that states “the individual levoglucosan and Kbb spikes occur during the same time…”
Section 3.2: I appreciate the authors approach to use dust as a potential indicator of the source of biomass burning. However, it is also worth noting that model and observation studies from Antarctica have shown that South America is a source of biomass burning aerosols to Antarctica.

Minor:
General: When describing time periods, I would encourage the authors to describe time from oldest to youngest. For example, in the Abstract line 18 it would make more sense to say “between 2500 to 1500 year BP”. This is observed though out the manuscript and I will not point out all of the instances.
Page 7 line 4: This introductory sentence is confusing. This paragraph is about other factors influencing the Levoglucosan and therefore setting up the discussion about the Potassium record in the following paragraph. I think a more general introductory sentence here would be more appropriate.
Page 8 line 10: This introductory sentence is wordy and confusing. I would consider instead “the individual levoglucosan and Kbb spikes occur during the same time periods which correspond to…”

Figure comments:
Figure 1: The caption should include “Talos Dome (TD) and Dome C (DC), Taylor Dome (Taylor D)”. The labels for South America, South Africa, Australia and New Zealand should be made white or removed.
Figure 3 caption: I would include in the figure caption “Red dots on map indicate the location of the charcoal records”
Figure 4 caption: The authors do not need to capitalize “Temperature” or “Dust” when following a comma.
Figure 5 caption: “Carbon” does not need to be capitalized when following a comma.

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ED: Reconsider after major revisions (31 May 2018) by Eric Wolff

Dear authors

I received referee reports from the same two reviewers for your new version. You will see that reviewer 2 is broadly supportive, but raises some detailed issues you would have to address. However reviewer 1 still has a fundamental problem with your potassium (K) data and its use. They are an expert on ice core ionorganic chemistry and I share their concern. As presented the K data must be wrong. You therefore need either to review your K data so it becomes explainable, or remove all discussion of the K data from the paper. If you are unable to take either of these steps then I would have to reject the paper, but I hope you can come to understand the problem and therefore deal with it.

The problem is:
(a) that the K data AND the K_BB data appear to be quite well-correlated with the Na data, both in the spikes and the background. The ratio between K and Na for the correlation (about 0.2) is far higher than the sea salt ratio.
(b) because the K values are high and cannot be explained by seasalt with the normal ratio, you end up with K_BB always being the major component of K (in the background as well), which is extremely surprising for such a remote site, and much higher than would be expected even in places where biomass burning is a strong influence.

The most parsimonious explanation is that your K data are systematically a factor about 5 too high, and that actually sea salt is a much larger component. Clearly any spikes that coincide with Na spikes (as most do) cannot be considered as BB spikes. Unless you can identify a calibration problem I do not see any easy way to correct for this issue. Even if you think your analyses are OK, the K data are so strange that they would need a separate explanation (why should K_BB be correlated with Na) before it was possible to consider them as a BB marker. In these circumstances I cannot see any way to accept a paper that incloudes K data.

Just as a positive, I disagree with Rev 1 about the accumulation data which seem coherent with those shown in the AICC2012 files.

Please either prepare a new version without K_BB or let me know what alternative you propose.

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AR by Lorena Grabowski on behalf of the Authors (12 Jun 2018) Author's response

ED: Publish as is (14 Jun 2018) by Eric Wolff

Short summary

From the analysis of an Antarctic ice core we showed that during the mid- to late Holocene (6000–750 BP) the long-term fire activity increased with higher rates starting at ~ 4000 BP and, more surprisingly, peaked between 2500 and 1500 BP. The anomalous increase in biomass burning centered at about 2000 BP is due to a complex interaction between changes in atmospheric circulation and biomass availability, with the main contribution coming from southern South America.