Pending recovery in the strength of the meridional overturning circulation at 26°&thinsp;N

Moat, Ben I.; Smeed, David A.; Frajka-Williams, Eleanor; Desbruyères, Damien G.; Beaulieu, Claudie; Johns, William E.; Rayner, Darren; Sanchez-Franks, Alejandra; Baringer, Molly O.; Volkov, Denis; Jackson, Laura C.; Bryden, Harry L.

doi:https://doi.org/10.5194/os-16-863-2020

Articles | Volume 16, issue 4

https://doi.org/10.5194/os-16-863-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/os-16-863-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 4

Research article

|

23 Jul 2020

Research article |

| 23 Jul 2020

Pending recovery in the strength of the meridional overturning circulation at 26° N

Ben I. Moat, David A. Smeed, Eleanor Frajka-Williams, Damien G. Desbruyères, Claudie Beaulieu, William E. Johns, Darren Rayner, Alejandra Sanchez-Franks, Molly O. Baringer, Denis Volkov, Laura C. Jackson, and Harry L. Bryden

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Final revised paper (published on 23 Jul 2020)
Preprint (discussion started on 17 Jan 2020)

Interactive discussion

Status: closed

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

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RC1: 'reviews_OS', Anonymous Referee #1, 25 Feb 2020
- AC1: 'Response to reviewer 1', Ben Moat, 15 May 2020
RC2: 'Moat et al. 2020 Review', Anonymous Referee #2, 09 Mar 2020
- AC2: 'Response to reviewer 2', Ben Moat, 15 May 2020

Peer-review completion

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

AR by Ben Moat on behalf of the Authors (15 May 2020) Manuscript

ED: Referee Nomination & Report Request started (20 May 2020) by Erik van Sebille

RR by Anonymous Referee #1 (02 Jun 2020)

Suggestions for revision or reasons for rejection

I thank the authors for the detailed response and for addressing my comments. The manuscript has now been much improved. That said, here I have two comments based on my review of the revised manuscript, which require clarification and revision accordingly.

1. Lines 311-314 on Page 8: The authors appear to infer the intensity of “localized deep convection” from the intensity of basin-integrated water mass transformation. However, there have been no observations to support such a reversal around 2005 in deep convection intensity in the subpolar basins. Actually, the deep convection in the Labrador and Irminger basins were intensified during the consecutive winters of 2007/2008 and 2008/2009 (Yashayaev et al. 2016; de Jong et al. 2012).

It further raises a question as to whether there is expected to be a delayed overturning response to the well-documented 2007-2009 events. What are the implications for the expectation of such a response to the 2013-2015 events (lines 324-325, page 8)?

2. Section 4.3 seems to be defocusing as it discusses the overturning’s impact over the time scales that may not be resolved by the RAPID time series. The analysis instead mainly relies on the GloSea5 AMOC at 26N to relate AMV and NAO to overturning changes. Thus, the statement about ‘observed AMOC variability’ (lines 484-486, page 10) is misleading because of the use of the GloSea5 AMOC series. I would suggest the authors discuss the SST and atmospheric changes during the observational time period and their implications for the longer-term AMV or NAO changes.

References:

de Jong, M. F., et al. (2012). "Convective mixing in the central Irminger Sea: 2002–2010." Deep Sea Research Part I: Oceanographic Research Papers 63: 36-51.

Yashayaev, I. and J. W. Loder (2016). "Recurrent replenishment of Labrador Sea Water and associated decadal-scale variability." Journal of Geophysical Research-Oceans 121(11): 8095-8114.

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RR by Anonymous Referee #2 (04 Jun 2020)

ED: Publish subject to minor revisions (review by editor) (04 Jun 2020) by Erik van Sebille

AR by Ben Moat on behalf of the Authors (13 Jun 2020) Author's response Manuscript

ED: Publish as is (23 Jun 2020) by Erik van Sebille

AR by Ben Moat on behalf of the Authors (26 Jun 2020) Manuscript

Short summary

The RAPID 26° N array has been measuring the Atlantic meridional overturning circulation (AMOC) since 2004. Since 2009 the AMOC has, compared with previous years, been in a low state. In 2013–2015, in the northern North Atlantic, strong cooling was observed in the ocean and anticipated to intensify the strength of the AMOC some years later. Here, we analyse the latest results from 26° N and conclude that while the AMOC has increased since 2009, this increase is not statistically significant.