Evolution of <sup>231</sup>Pa and <sup>230</sup>Th in overflow waters of the North Atlantic

Deng, Feifei; Henderson, Gideon M.; Castrillejo, Maxi; Perez, Fiz F.; Steinfeldt, Reiner

doi:https://doi.org/10.5194/bg-15-7299-2018

Articles | Volume 15, issue 23

https://doi.org/10.5194/bg-15-7299-2018

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

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https://doi.org/10.5194/bg-15-7299-2018

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

Articles | Volume 15, issue 23

Research article

|

10 Dec 2018

Research article |

| 10 Dec 2018

Evolution of ²³¹Pa and ²³⁰Th in overflow waters of the North Atlantic

Feifei Deng, Gideon M. Henderson, Maxi Castrillejo, Fiz F. Perez, and Reiner Steinfeldt

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Final revised paper (published on 10 Dec 2018)
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Preprint (discussion started on 27 Apr 2018)
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Status: closed

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

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RC1: 'Review of bg-2018-191 by R. Francois', Roger Francois, 13 May 2018
- AC1: '“Evolution of 231Pa and 230Th in overflow waters of the North Atlantic” by Feifei Deng et al. Response to referee #1', Feifei Deng, 31 Aug 2018
RC2: 'Review of bg-2018-191', Anonymous Referee #2, 14 May 2018
- AC2: '“Evolution of 231Pa and 230Th in overflow waters of the North Atlantic” by Feifei Deng et al. Response to referee #2', Feifei Deng, 31 Aug 2018
RC3: 'Comment on “Evolution of 231Pa and 230Th in overflow waters of the North Atlantic"', Anonymous Referee #3, 19 May 2018
- AC3: '“Evolution of 231Pa and 230Th in overflow waters of the North Atlantic” by Feifei Deng et al. Response to referee #3', Feifei Deng, 31 Aug 2018

Peer-review completion

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

ED: Reconsider after major revisions (10 Sep 2018) by Gilles Reverdin

AR by Feifei Deng on behalf of the Authors (10 Sep 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Sep 2018) by Gilles Reverdin

RR by Anonymous Referee #3 (04 Oct 2018)

Suggestions for revision or reasons for rejection

Deng et al. have provided a thoughtful response to comments from the referees, and the authors have made helpful clarifications in revising their text. I recommend publication with just a few further changes.

The following comments refer to page and line numbers in the authors’ response version of the revised manuscript.

1) Section 4.3, p. 8, around line 29: Although the model equation from Moran et al. (1997) is given in the Supplementary Material, it would be easier for readers to understand the findings described in the text if the model equation were included in the main text. It was not immediately obvious to me how the model curves in Figure 9 were obtained until I realized that the curves were derived by plugging the preformed concentrations, S, SPM and Kd into Moran’s equation (originally from Rutgers van der Loeff?) along with the reference depth (either 2000 m or 3500 m) to obtain the curves as a function of water mass age. Anticipating that other readers may similarly find this hard to follow, I recommend that the equation be added to the main text so that readers can see immediately how the curves in Figure 9 were obtained.

2) p. 9, lines 11-14: It is not only possible that scavenging of 230Th is more intense than would be inferred from the parameters derived using Station 13 data, the model-data offsets observed here require this. I suggest adding a sentence or two to speculate about why scavenging may be greater than at Station 13 at these locations.

3) p. 9, line 27: Delete “from” in “those in from DSOW”

4) Figure 6, caption, change “older waters west of” to “older waters east of”

5) Figure 7, bottom left panel, in the heading change “Observed” to “Scavenged”

6) Figure S1, caption, change “profiles of and 13” to “profiles of Station 13”

7) Section S4, providing information about sources of uncertainty in the assessment of scavenging, is very important. I recommend moving it to the Discussion section of the main text.

8) Supplementary material, the Journal, Volume and page numbers is missing for the first reference.

Summary: As stated in my original review, the authors present a valuable new data set. The discussion of the sensitivity of Pa/Th ratios to preformed (initial) dissolved 231Pa and 230Th concentrations, to my knowledge, has not been presented before. This is a particularly useful discussion to help direct future studies of the Pa/Th ratio as a paleo circulation proxy when applied to North Atlantic sediments.

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ED: Publish subject to minor revisions (review by editor) (10 Oct 2018) by Gilles Reverdin

AR by Feifei Deng on behalf of the Authors (24 Oct 2018) Manuscript

ED: Publish as is (29 Oct 2018) by Gilles Reverdin

AR by Feifei Deng on behalf of the Authors (08 Nov 2018) Author's response Manuscript

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Short summary

To better use Pa / Th to reconstruct deep water ventilation rate, we assessed controls on ²³⁰Th and ²³¹Pa in the northern North Atlantic. With extended optimum multi-parameter analysis and CFC-based water-mass age, we found the imprint of young overflow water on Th and Pa and enhanced scavenging near the seafloor. A significantly higher advective loss of Pa to the south relative to Th in the Atlantic was estimated, supporting the use of Pa / Th for assessing basin-scale meridional transport.

Evolution of 231Pa and 230Th in overflow waters of the North Atlantic

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Evolution of ²³¹Pa and ²³⁰Th in overflow waters of the North Atlantic