Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean

Salt, L. A.; van Heuven, S. M. A. C.; Claus, M. E.; Jones, E. M.; de Baar, H. J. W.

doi:https://doi.org/10.5194/bg-12-1387-2015

Articles | Volume 12, issue 5

https://doi.org/10.5194/bg-12-1387-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-12-1387-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 12, issue 5

Research article

|

05 Mar 2015

Research article |

| 05 Mar 2015

Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean

L. A. Salt, S. M. A. C. van Heuven, M. E. Claus, E. M. Jones, and H. J. W. de Baar

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Final revised paper (published on 05 Mar 2015)
Preprint (discussion started on 12 May 2014)

Interactive discussion

Status: closed

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

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- Supplement

RC C2363: 'Review of Salt et al.', Anonymous Referee #1, 11 Jun 2014
RC C2637: 'Review of the BGD work', Marta Álvarez, 18 Jun 2014
AC C4305: 'Response to Reviewers', Lesley Salt, 12 Aug 2014

Peer-review completion

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

AR by Lesley Salt on behalf of the Authors (12 Aug 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Nov 2014) by Gerhard Herndl

RR by Marta Álvarez (09 Dec 2014)

RR by Anonymous Referee #1 (12 Dec 2014)

Suggestions for revision or reasons for rejection

In general I think that the authors have responded in a thoughtful way to the comments from me and the 2nd reviewer, and so made the manuscript significantly better. There are a few minor comments (editorial) that I mention below that should be dealt with. More importantly though is the response to two major remarks by both reviewers that is not really dealt with in a satisfactory way. In light of this my review is that the manuscript should be published, but that additional revision is necessary.
Major issues:
The author’s response to my request for a secondary quality control of the data used in this study is not satisfactory. The authors of the paper are well familiar with 2nd QC and cross over analysis. No comparisons need to be shown in the paper, but the analysis needs to be done, it is almost a standard procedure these days, particularly in any work dealing with temporal trends and changes of properties. The authors should compare the accuracy/consistency of their data to publically available data collections such as CARINA or GLODAP. This is valid for both the carbonate system variables as well as supporting variables for the MLR analysis. An attempt is done for a comparison with the 194 A17 data, although the biases that the authors report on for, for instance, silicate is not convincing. I suggest using the consistent data products that exists to deal with this.
The second major issue is the neglect of including an analysis of other repeats of the A17 line. The focus of the paper now seems to have shifted (?) towards discussing buffer factors and thus the sensitivity of various water masses to the CO2 perturbation, rather than focuses on temporal changes. In this sense the neglect of the additional A17 lines might be justified. However, the authors mention in the introduction how the southwest Atlantic might have become more important in recent times for storage of anthropogenic carbon, including more A17 would give the authors some leverage to verify, or not, that suggestion.
Sections in Figures 3 and 4: I think it would be more useful to state (for instance) “Revelle factor” rather than “(a)” in Figure 4a as a text field over the bottom contour.
Line 475: I assume the authors mean “The highest buffer factors”, not “Revelle factors”.

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ED: Publish subject to minor revisions (Editor review) (26 Dec 2014) by Gerhard Herndl

AR by Lesley Salt on behalf of the Authors (16 Jan 2015) Author's response Manuscript

ED: Publish as is (19 Jan 2015) by Gerhard Herndl

AR by Lesley Salt on behalf of the Authors (26 Jan 2015)

Short summary

The increase in anthropogenic atmospheric carbon dioxide is mitigated by uptake by the world ocean, which alters the pH of the water. In the South Atlantic we find the highest rates of acidification relative to increase in anthropogenic carbon (Cant) found in Subantarctic Mode Water and Antarctic Intermediate Water. The moderate rates of increase in Cant combined with low buffering capacities, due to low salinity and alkalinity values, have caused rapid acidification in the Subantarctic Zone.