Antarctic Bottom Water and North Atlantic Deep Water  in CMIP6 models

Heuzé, Céline

doi:https://doi.org/10.5194/os-17-59-2021

Articles | Volume 17, issue 1

https://doi.org/10.5194/os-17-59-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/os-17-59-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 1

Research article

|

13 Jan 2021

Research article |

| 13 Jan 2021

Antarctic Bottom Water and North Atlantic Deep Water in CMIP6 models

Céline Heuzé

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Final revised paper (published on 13 Jan 2021)
Preprint (discussion started on 10 Jul 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'of “Antarctic Bottom Water and North Atlantic Deep Water in CMIP6 models” by Heuzé, submitted for publication in Ocean Sciences', Anonymous Referee #1, 25 Jul 2020
- AC1: 'Response to Reviewer 1', Céline Heuzé, 15 Sep 2020
RC2: 'Review of “Antarctic Bottom Water and North Atlantic Deep Water in CMIP6 models”', Anonymous Referee #2, 17 Aug 2020
- AC2: 'Response to Reviewer 2', Céline Heuzé, 15 Sep 2020

Peer-review completion

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

AR by Céline Heuzé on behalf of the Authors (15 Sep 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (09 Oct 2020) by Matthew Hecht

RR by Anonymous Referee #1 (15 Oct 2020)

Suggestions for revision or reasons for rejection

This manuscript discusses differences of ocean water properties between observations and the CMIP6 suite of coupled climate models, focusing on density, temperature, and salinity at the sea floor in the North Atlantic and Southern Ocean, where North Atlantic Deep Waters and Antarctic Bottom Waters are formed, as well as thicknesses of both of those water masses, and mixed layer depths. The work is interesting and original. The manuscript has been revised, and is very nearly ready for publication. There is still at least one inaccurate statement in the manuscript that should be corrected prior to publication. Furthermore, there is one suggestion for a small change to some of the figures that might improve them.

Substantive suggestions:

1. L23-24. The phrase “2000 m thick” is a bit too precise here. Perhaps “several hundred to few thousand meter thick” might be more accurate?

2. L83. Here is it not “the non-linearity of the equation of state” but probably much more owing to the positive skewness of mixed layer depth distributions. If one estimates mixed layer depths from instantaneous, or even daily profiles of water properties, in many locations one will obtain many shallow values and a few deep values. If one uses monthly average profiles they are likely to result in a deeper mixed layer than the average of the daily or hourly values.

3. L105 and following. The GIN sea component of the NADW is confusing. It seems like in this paper the GIN seas component is estimated within the GIN seas, whereas in Johnson (2008) it is estimated from near-bottom data in the Northern N. Atlantic, after most of the entrainment during the overflow process has taken place. Therefore the GIN seas component of NADW in Johnson (2008) will be much more “Atlantic” in character than in this paper. Does this cause issues? At the very least the difference should be pointed out in the revised manuscript.

4. Figures 2 and 4. If the colorbar were flipped for the standard deviation plots so that lighter shades correspond to smaller magnitudes, and darker shades to larger magnitudes, this reviewer would have an easier time assessing the patterns as the regions with large standard deviations would stand out.

5. L318. Change “fresh” to “light”? Density is not fresh, it is either light or dense.

Minor suggestions:

6. L153. The quotation marks are unnecessary here.

7. L181. Change “who” to “which”.

8. L368. Change “between” (which is used when comparing two things) to “among” (which is used when comparing more than two things).

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ED: Publish subject to minor revisions (review by editor) (28 Oct 2020) by Matthew Hecht

AR by Céline Heuzé on behalf of the Authors (02 Nov 2020) Author's response Manuscript

ED: Publish subject to technical corrections (21 Nov 2020) by Matthew Hecht

AR by Céline Heuzé on behalf of the Authors (21 Nov 2020) Author's response Manuscript

Short summary

Dense waters sinking by Antarctica and in the North Atlantic control global ocean currents and carbon storage. We need to know how these change with climate change, and thus we need accurate climate models. Here we show that dense water sinking in the latest models is better than in the previous ones, but there is still too much water sinking. This impacts how well models represent the deep ocean density and the deep currents globally. We also suggest ways to improve the models.