Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

Jahn, A.; Lindsay, K.; Giraud, X.; Gruber, N.; Otto-Bliesner, B. L.; Liu, Z.; Brady, E. C.

doi:https://doi.org/10.5194/gmd-8-2419-2015

Articles | Volume 8, issue 8

https://doi.org/10.5194/gmd-8-2419-2015

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

https://doi.org/10.5194/gmd-8-2419-2015

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

Articles | Volume 8, issue 8

Development and technical paper

|

05 Aug 2015

Development and technical paper |

| 05 Aug 2015

Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

A. Jahn, K. Lindsay, X. Giraud, N. Gruber, B. L. Otto-Bliesner, Z. Liu, and E. C. Brady

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Final revised paper (published on 05 Aug 2015)
Supplement to the final revised paper
Preprint (discussion started on 06 Nov 2014)

Interactive discussion

Status: closed

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

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- Supplement

RC C2541: 'Review of “Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)” by Alex Jahn et al.', Anonymous Referee #1, 02 Dec 2014
- AC C3679: 'Author comment, reply to Reviewer #1', Alexandra Jahn, 01 May 2015
RC C2817: 'Interactive comment on “Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)” by A. Jahn, K. Lindsay, X. Giraud, B.L. Otto-Bliesner, Z. Liu and E.C. Brady, submitted to Geosci. Mod. Dev. Discuss.', Anonymous Referee #2, 31 Dec 2014
- AC C3686: 'Author comment, reply to Reviewer #2', Alexandra Jahn, 01 May 2015

Peer-review completion

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

AR by Alexandra Jahn on behalf of the Authors (26 May 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 May 2015) by Guy Munhoven

RR by Anonymous Referee #1 (23 Jun 2015)

Suggestions for revision or reasons for rejection

Second review of gmd-2014-182, “Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)” by Alex Jahn et al.

I am glad that the authors decided to equilibrate the model for an additional 2450 years. While still not in equilibrium, I am now more confident with the presented results.

However, the authors have decided not to act on most of my other suggestions, including (a) a more detailed comparison with observations, (b) a comparison with other isotope-enabled models and (c) a more thorough analysis of the reasons why the simulated isotopes are over- or underestimated in certain regions. The recurrent reasoning in their rebuttal for not taking these suggestions on board is the claim that the coarse-resolution model described here is not commonly used for science applications. Instead, the authors plan to validate the carbon isotope simulation in the fully coupled CESM at 1 degree resolution in the future, as the 1 degree model will be used for science applications.

I find this reasoning bizarre. Why did the authors decide to describe new model development for a model that won’t be used for science applications? Why not wait instead and describe the model development and the validation together for the 1 degree model instead?

Furthermore, I believe that there is enough interest in the modeling community for the 3 degree model. There is an urgent need for fully coupled isotope enabled models that are fast enough to simulate longer timescales. Future users would benefit from a more thorough validation of this model.

Either way, my suggestions were just suggestions to improve the paper; they were never intended to be a showstopper. The description of the new model components is certainly at a publishable standard. I am happy to accept the authors’ reasoning and give green light for publication.

Minor comment: Please include the last sentence in your abstract that was deleted in the second version: “At the same time, the carbon isotopes reveal biases in the physical model, for example…”. I think that this is one of the major virtues of isotopes in climate models.

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ED: Publish subject to minor revisions (Editor review) (03 Jul 2015) by Guy Munhoven

AR by Alexandra Jahn on behalf of the Authors (13 Jul 2015) Author's response Manuscript

ED: Publish as is (14 Jul 2015) by Guy Munhoven

AR by Alexandra Jahn on behalf of the Authors (15 Jul 2015)

Short summary

Carbon isotopes have been added to the ocean model of the Community Earth System Model version 1 (CESM1). This paper describes the details of how the abiotic 14C tracer and the biotic 13C and 14C tracers were added to the existing ocean model of the CESM. In addition, it shows the first results of the new model features compared to observational data for the 1990s.