New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

Guyennon, A.; Baklouti, M.; Diaz, F.; Palmieri, J.; Beuvier, J.; Lebaupin-Brossier, C.; Arsouze, T.; Béranger, K.; Dutay, J.-C.; Moutin, T.

doi:https://doi.org/10.5194/bg-12-7025-2015

Articles | Volume 12, issue 23

https://doi.org/10.5194/bg-12-7025-2015

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

https://doi.org/10.5194/bg-12-7025-2015

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

Articles | Volume 12, issue 23

Research article

|

07 Dec 2015

Research article |

| 07 Dec 2015

New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

A. Guyennon, M. Baklouti, F. Diaz, J. Palmieri, J. Beuvier, C. Lebaupin-Brossier, T. Arsouze, K. Béranger, J.-C. Dutay, and T. Moutin

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Final revised paper (published on 07 Dec 2015)
Supplement to the final revised paper
Preprint (discussion started on 24 Apr 2015)

Interactive discussion

Status: closed

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

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- Supplement

RC C3122: 'Reviewer's comments on "New insights into the organic carbon export in the Mediterranean Sea from 3D modeling"', Anonymous Referee #1, 25 Jun 2015
- AC C3829: 'Answer to the referees comments', Arnaud Guyennon, 27 Jul 2015
RC C3234: 'Review of: New insights into the organic carbon export in the Mediterranean Sea from 3D modeling, submitted to Biogeosciences', Anonymous Referee #2, 01 Jul 2015
- AC C3830: 'Answer to the referees comments', Arnaud Guyennon, 27 Jul 2015

Peer-review completion

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

ED: Reconsider after major revisions (28 Jul 2015) by Christoph Heinze

AR by Melika Baklouti on behalf of the Authors (07 Sep 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Sep 2015) by Christoph Heinze

RR by Anonymous Referee #3 (29 Sep 2015)

Suggestions for revision or reasons for rejection

I have read the revised version of the manuscript submitted by Guyennon et al. as well as the answers provided by the authors to the reviewers comments. I am not convinced that this revised version can now be published in Biogeosciences. Indeed, the authors decided to put in the appendix a substantial part of the manuscript in order to answer to the comments of the reviewers that the manuscript is too long (which was true). This results in a very long appendix (more than a half of the main text length). I understand that the authors have to show that their model has the ability to understand the key questions at the core of this manuscript but it would have been more appropriate to have a full paper dedicated to model validation issues and then to have another one focused on the estimation of the export. This is my advice because it would allow describing extensively the validation exercise which is a crucial problem in modelling that cannot be put in the appendix but rather deserves an entire paper.
Moreover, the validation of the results is in some places not convincing as also noticed by the other reviewers. In particular, I am not satisfied with the answer provided by the authors as concerns the validation of the physical model and in particular, on the ability of the physical model to simulate vertical processes such as convective ones. A large part of the conclusions on the vertical export is determined by the capacity of the physical model to generate deep convection (e.g. in intense convective regions like the Gulf of Lions).
Another process that is essential for the vertical export is the sedimentation process of POC. Here, the authors used one class of POM with one sinking speed. There are other models that used several size classes or aggregation models in order to refine the representation of the export. This refinement would be needed considering the questions that the model has to address.
I am not convinced by the answer provided by the authors for justifying the period 1973-1977 for performing the adjustment to initial conditions and then to run the simulations in the 1990s since the conditions drastically change in the 1990s. This choice makes that the nutrient content of deep waters show discrepancies with results from the BOUM cruise as pointed by the authors. The authors justify this choice by saying that they would like to be outside the period of EMT but if as they mentioned EMT drastically change the nutrient structure, then there is nosense to use 70s conditions for simulating the 90s.
Finally (minor), I am not convinced by the answer they provide to justify the innovative aspect of their model. I agree with the reviewer that since years, models (e.g. ERSEM, BFM) simulate the nutrient content of PFTs and not only the ratios as mentioned by the authors. The new part here is the explicit representation of the cells number.

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RR by Anonymous Referee #4 (12 Oct 2015)

RR by Anonymous Referee #5 (13 Oct 2015)

ED: Publish subject to minor revisions (Editor review) (14 Oct 2015) by Christoph Heinze

AR by Melika Baklouti on behalf of the Authors (27 Oct 2015) Author's response Manuscript

ED: Publish as is (05 Nov 2015) by Christoph Heinze

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Short summary

Dissolved organic carbon (DOC) has already been identified as a potentially significant source of carbon export in the Mediterranean Sea, though in situ export estimations are scarce. This work provides a thorough analysis at basin scale of carbon export with the coupled model NEMO-MED12/Eco3M-MED model. The seasonality and the processes of particulate and dissolved carbon production are also investigated. DOC export appears to be dominant in most regions, especially in the eastern basin.