Effects of strongly eddying oceans on multidecadal climate variability in the Community Earth System Model

Jüling, André; von der Heydt, Anna; Dijkstra, Henk A.

doi:https://doi.org/10.5194/os-17-1251-2021

Articles | Volume 17, issue 5

https://doi.org/10.5194/os-17-1251-2021

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

https://doi.org/10.5194/os-17-1251-2021

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

Articles | Volume 17, issue 5

Research article

|

16 Sep 2021

Research article |

| 16 Sep 2021

Effects of strongly eddying oceans on multidecadal climate variability in the Community Earth System Model

André Jüling, Anna von der Heydt, and Henk A. Dijkstra

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Final revised paper (published on 16 Sep 2021)
Preprint (discussion started on 18 Sep 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of os-2020-85', Anonymous Referee #1, 05 Oct 2020
- AC1: 'Reply on RC1', André Jüling, 12 Feb 2021
RC2: 'Review of “Effects of strongly eddying oceans on multidecadal climate variability in the Community Earth System Model”', Anonymous Referee #2, 19 Oct 2020
- AC2: 'Reply on RC2', André Jüling, 12 Feb 2021

Peer-review completion

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

AR by André Jüling on behalf of the Authors (12 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (28 Mar 2021) by Bernadette Sloyan

RR by Anonymous Referee #1 (07 Apr 2021)

Suggestions for revision or reasons for rejection

I believed the author has addressed most of the comments raised in the first round of review. Overall, I think the conclusions are clearer and more convincing. I have some additional suggestions/comments that I think would help improve the manuscript.

1. I suggest adding uncertainties in the mean spectral power and spectral slope estimates and/or carrying out hypothesis testing to determine if the difference seen in these mean spectral powers (and spectral slope) are statistically different.
2. Line 5: remove ‘eventually’ from the phrase ‘eventually the global mean surface temperature’.
3. Line 9: I appreciate that you tried to be more explicit about the implications of the study in the abstract and discussion. But I’m not super satisfied with the abstract part. I guess what I’m thinking is it would be great to highlight the implications of this study (mesoscale variability is important to multidecadal variability) on studies that use CMIP class models in the abstract.
4. Lines 46-57: I appreciate the addition of this paragraph to clarify the relationship between these climate modes, SHF, OHC, and GMST. However, how this paragraph is currently written is a bit awkward. Since the majority of the introduction section is about the SST modes, I would reorganize the paragraph a bit, such that it focuses on how representation of SST patterns affects our quantification of SHF, OHC, and GMST, instead of how it is currently written – how the latter three metrics are related to SST.
5. Lines 92-93: I would change ‘In idealized non-eddying ocean models, modes of multidecadal variability exist that depend critically on the prescribed eddy diffusivity’ to ‘In idealized non-eddying ocean models, the existence of modes of multidecadal variability depends critically on the prescribed eddy diffusivity’.
6. At some point in the intro, it might be worth mentioning what is the spatial scale of mesoscale just to highlight why 1 deg models do not resolve mesoscale.
7. Line 121-123: I would also add Chang et al. (2020), where they did a longer simulation and supplemented it with extremely detailed analyses.
8. Line 141: For the sake of completeness, maybe it’s worth to test the sensitivity of your results with other SST products also (e.g., ERSST, COBE)?
9. Line 208: Out of curiosity, why is the HR-CESM is interpolated to specifically 0.4deg rectangular grid?
10. Line 222: ‘(Fig. (Fig. 2d)’ should be ‘Fig. 2d’.
11. Line 222-223: This statement is a bit confusing – it is implying that there is a causal relationship between the previous sentence and this sentence, but in reality, the larger amplitude in observed low-pass filtered PDO compared to models *does not* imply there is a larger proportion of spectral power >13 years. Please clarify.
12. Line 268: The correct reference for MacDonald 2005 should be MacDonald and Case 2005. Apologies for providing the incorrect reference in the previous review.

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RR by Anonymous Referee #2 (19 Apr 2021)

ED: Publish subject to minor revisions (review by editor) (29 Apr 2021) by Bernadette Sloyan

AR by André Jüling on behalf of the Authors (26 May 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (22 Jun 2021) by Bernadette Sloyan

AR by André Jüling on behalf of the Authors (30 Jun 2021) Manuscript

Short summary

On top of forced changes such as human-caused global warming, unforced climate variability exists. Most multidecadal variability (MV) involves the oceans, but current climate models use non-turbulent, coarse-resolution oceans. We investigate the effect of resolving important turbulent ocean features on MV. We find that ocean heat content, ocean–atmosphere heat flux, and global mean surface temperature MV is more pronounced in the higher-resolution model relative to higher-frequency variability.