A comparison of ocean model data and satellite observations of features affecting the growth of the North Equatorial Counter Current during the strong 1997–1998 El Niño

Webb, David J.; Coward, Andrew C.; Snaith, Helen M.

doi:https://doi.org/10.5194/os-16-565-2020

Articles | Volume 16, issue 3

https://doi.org/10.5194/os-16-565-2020

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

https://doi.org/10.5194/os-16-565-2020

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

Articles | Volume 16, issue 3

Research article

|

05 May 2020

Research article |

| 05 May 2020

A comparison of ocean model data and satellite observations of features affecting the growth of the North Equatorial Counter Current during the strong 1997–1998 El Niño

David J. Webb, Andrew C. Coward, and Helen M. Snaith

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Final revised paper (published on 05 May 2020)
Preprint (discussion started on 19 Aug 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review for Authors', Anonymous Referee #1, 17 Sep 2019
- AC1: 'Preliminary Response to Reviewer 1', David Webb, 18 Sep 2019
- AC2: 'Response to Reviewer 1', David Webb, 28 Oct 2019
RC2: 'Review for Authors', Anonymous Referee #2, 26 Oct 2019
- AC3: 'Response to Reviewer 2', David Webb, 31 Oct 2019

Peer-review completion

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

AR by David Webb on behalf of the Authors (18 Nov 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Dec 2019) by Matthew Hecht

RR by Anonymous Referee #2 (21 Jan 2020)

Suggestions for revision or reasons for rejection

This paper argues that the NECC transport is a key player during the development of the 1997/98 El Nino : 1) the NECC becomes stronger because of « larger sea level difference across the current than normal », and 2) the waters advected by the NECC becomes warmer because of reduced cooling by the TIW activity. I cannot really disagree with this view, but my concern is that these processes are just the consequences of the equatorial wave activity during the development of El Nino : the Kelvin wave modifies the sea level difference across the equatorial band, which modulates the NECC, and it deepends the thermocline in the east, which reduces the current instability in the east that normally produces TIW. So it seems to me that the authors do not really provide a new perspective on the 1997/98 El Nino development, as it is suggested, but they just proposes a different angle of view. I think this should be more clearly recognized in the text.

The analyses also remain qualitative ; for instance it is not really demonstrated that reduced TIW activity during the development of the 1997/98 El Nino reduces the cooling of the waters transported by the stronger NECC. A heat budget would be required to quantify this, in which the contribution the NECC anomalies to the advection terms would need to be isolated. A discussion on how the suggested processes should be further tested in the model should be provided (e.g. what type of sensitivity experiments could be done with the model to isolate the effect of the NECC? how would the authors estimate the contribution of reduced TIW activity on the NECC heat transport?)

The title should also reflect that the work focuses on the role of the NECC on the development of the 1997/98 El Nino.

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RR by Matthew Hecht (03 Feb 2020)

ED: Publish subject to minor revisions (review by editor) (03 Feb 2020) by Matthew Hecht

AR by David Webb on behalf of the Authors (27 Feb 2020) Author's response Manuscript

ED: Publish as is (11 Mar 2020) by Matthew Hecht

AR by David Webb on behalf of the Authors (20 Mar 2020)

Short summary

In conflict with conventional theory, recent analysis of data from a high-resolution global ocean model showed that the North Equatorial Counter Current was responsible for the unusually warm water which triggered the strong El Niños of 1982–83 and 1997–98. In this paper some of the key physics deduced from the model results are tested against satellite data from the 1997–98 event. The results show that the model closely followed reality during the period, further supporting the new mechanisms.