JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1)

Wiltshire, Andrew J.; Burke, Eleanor J.; Chadburn, Sarah E.; Jones, Chris D.; Cox, Peter M.; Davies-Barnard, Taraka; Friedlingstein, Pierre; Harper, Anna B.; Liddicoat, Spencer; Sitch, Stephen; Zaehle, Sönke

doi:https://doi.org/10.5194/gmd-14-2161-2021

Articles | Volume 14, issue 4

https://doi.org/10.5194/gmd-14-2161-2021

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

Special issue:

Joint UK Land Environment Simulator (JULES) – configurations,...

https://doi.org/10.5194/gmd-14-2161-2021

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

Articles | Volume 14, issue 4

Model description paper

|

27 Apr 2021

Model description paper |

| 27 Apr 2021

JULES-CN: a coupled terrestrial carbon–nitrogen scheme (JULES vn5.1)

Andrew J. Wiltshire, Eleanor J. Burke, Sarah E. Chadburn, Chris D. Jones, Peter M. Cox, Taraka Davies-Barnard, Pierre Friedlingstein, Anna B. Harper, Spencer Liddicoat, Stephen Sitch, and Sönke Zaehle

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Final revised paper (published on 27 Apr 2021)
Preprint (discussion started on 24 Jul 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Clear model description of the implementation of the nitrogen cycle within JULES', David Wårlind, 17 Aug 2020
- AC1: 'Response to RC1', Eleanor Burke, 03 Nov 2020
RC2: 'Nitrogen and vertically resolved land model in JULES', William Wieder, 19 Aug 2020
- AC2: 'Response to RC2', Eleanor Burke, 03 Nov 2020
RC3: 'Manuscript needs substantial work', Anonymous Referee #3, 20 Aug 2020
- AC3: 'Response to RC3', Eleanor Burke, 03 Nov 2020

Peer-review completion

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

AR by Eleanor Burke on behalf of the Authors (02 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Dec 2020) by Jatin Kala

RR by William Wieder (13 Dec 2020)

Suggestions for revision or reasons for rejection

I appreciate the revisions Wiltshire and co-authors made to their manuscript. This is good work, well written & very clear. I appreciate how directly the text lays out model assumptions from the outset.

My main outstanding question is how much of the reduction in global productivity, biomass, and IAV with the new C-N model comes from actual N limitation on living biomass and the intended declines in CUE associated with N limitation vs. simply killing off plants by imposing N limitation. Specifically, the N model makes the bare ground bias in JULES even stronger (relative to the C-only model (Fig. 3). Thus, are lower C flux and stocks simulated by JULES-CN simply a product of having more dead plants in the model?

On a related note, I appreciate the synthesis of many results in zonal mean plots and annual time series, but wonder if there are insights or information that could be gained from showing full spatial maps of initial results (e.g. vegetation cover, GPP, or LAI in the CN model and their difference from the C-only results?). Maybe it makes sense to put these in supplemental material, if the authors are worried about cluttering up their results.

It seems like these two points matter, especially if JULES-CN is going to be included in UKESM1 simulations where potential biases in bare ground fraction may influence the land energy and water balance in ways that feedback on the atmosphere and climate.

Line 80: Minor concern, but I think there’s a new GCP paper out now.

Finally, it should also be noted that comparisons with GCP2019 estimates of NEE and IAV are themselves a modeled product from the TRNEDY simulations, of which JULES-CN participated. These are quasi-independent estimates, not results residual of bookkeeping methods, as previously presented.

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RR by Anonymous Referee #3 (04 Feb 2021)

ED: Publish subject to minor revisions (review by editor) (04 Feb 2021) by Jatin Kala

AR by Eleanor Burke on behalf of the Authors (05 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (09 Mar 2021) by Jatin Kala

AR by Eleanor Burke on behalf of the Authors (11 Mar 2021)

Short summary

Limited nitrogen availbility can restrict the growth of plants and their ability to assimilate carbon. It is important to include the impact of this process on the global land carbon cycle. This paper presents a model of the coupled land carbon and nitrogen cycle, which is included within the UK Earth System model to improve projections of climate change and impacts on ecosystems.