Modelling northern peatland area and carbon dynamics since the Holocene with the ORCHIDEE-PEAT land surface model (SVN r5488)

Qiu, Chunjing; Zhu, Dan; Ciais, Philippe; Guenet, Bertrand; Peng, Shushi; Krinner, Gerhard; Tootchi, Ardalan; Ducharne, Agnès; Hastie, Adam

doi:https://doi.org/10.5194/gmd-12-2961-2019

Articles | Volume 12, issue 7

https://doi.org/10.5194/gmd-12-2961-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-12-2961-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 7

Model description paper

|

15 Jul 2019

Model description paper |

| 15 Jul 2019

Modelling northern peatland area and carbon dynamics since the Holocene with the ORCHIDEE-PEAT land surface model (SVN r5488)

Chunjing Qiu, Dan Zhu, Philippe Ciais, Bertrand Guenet, Shushi Peng, Gerhard Krinner, Ardalan Tootchi, Agnès Ducharne, and Adam Hastie

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Final revised paper (published on 15 Jul 2019)
Supplement to the final revised paper
Preprint (discussion started on 29 Nov 2018)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review for Qiu et al. (2018) GMDD “Modelling northern peatlands area and carbon dynamics since the Holocene with the ORCHIDEE-PEAT land surface model (SVN r5488)”', Benjamin Stocker, 11 Jan 2019
- AC1: 'reply to RC1', Chunjing Qiu, 28 Mar 2019
RC2: 'Review of Qiu et al.', Anonymous Referee #2, 01 Feb 2019
- AC2: 'reply to RC2', Chunjing Qiu, 28 Mar 2019

Peer-review completion

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

AR by Chunjing Qiu on behalf of the Authors (28 Mar 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Apr 2019) by Tomomichi Kato

RR by Joe Melton (05 Apr 2019)

RR by Benjamin Stocker (19 Apr 2019)

Suggestions for revision or reasons for rejection

The authors carefully addressed or responded to the comments I had raised on the initial submission. The manuscript is now clearer and the work is better motivated in the context of previous work that has been done on global dynamic peatland modelling.

Please consider my comments on specific points raised before and the author's response below. I rated "scientific reproducibility" as "fair" due to the argument made below under 'Q1'.

Q1: I can see practical reasons that it’s often very challenging to separate model parts so that they can be run as a stand-alone. The authors argue that there is a feedback between hydrology and peatland development that is subject to the processes in the non-peatland part of the model. I am suggesting to ignore this and prescribe soil moisture or whatever is required. The point is that the relevant model parts can be run in a demo setup, not actually reproducing the results presented here exactly. Plug and play.

Q2: Would be worth mentioning how permafrost is dealt with also in the manuscript? Appreciate the inclusion of the evaluation of inundation timing.

Q3: Interesting added text on the isostatic rebound effect and the formation of the Hudson Bay Lowland peatland complex. The essential mechanism of the “sponge-feedback” is that, on peatlands, less water is diverted into runoff, raises the water table, and adds to subsequent inundation. Is it spelled out explicitly in the manuscript, that this effect is accounted for by the model?

Q4: Ok, added text explaining the necessity and effect of the empirical depth scaling addresses my comment.

Q5: This is interesting, that the simulation with fixed peatland extent did no yield faster accumulation. But as authors explain, this may be due to the redistribution of runoff water within the gridcell and C transferred from the mineral soil to the peatland fraction. It sounds like this is a model-specific issue then and cannot easily be resolved in this paper. Therefore, I agree with how it’s dealt with in the revised manuscript.

Q6: I would recommend stating it in the manuscript as clearly as given in the response to the editor that “we can’t compare simulated peat C profile against dated peat cores because our model doesn’t track age bins explicitly.” The statement now given in the manuscript (“more peat core data collected with more rigorous sampling methodologies”) does not reflect this limitation of the model evaluation. I would find it helpful if this limitation was spelled out in order to motivate future research in this direction.

Q9: I do not agree with the statement now made in the manuscript: “The model therefore aims to simulate average peat depth and C profile in a grid location rather than capturing peat inception time and age-depth profiles of peat cores.” The timing of inception and C accumulation history (yielding the age-depth profile) are essential for simulating the C cycle effect of peatlands. That’s what the model will be used for and is used for here (Holocene simulations).

Q10: The reason I made this point is to motivate a revision of the manuscript text, so that readers will better understand the model.

Q11: I was not advocating a more direct comparison to inundation simulated by Stocker et al., (2014), but rather that a statement is made for why the improvements in the simulated inundation is achieved. Btw, it’s not correct that “ST14 used gridcell average soil parameters in soil hydrology.”

The explicit spelling out of differences between ST14 and the present model (l. 284) is very helpful. Thanks for including this!

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ED: Publish subject to minor revisions (review by editor) (23 May 2019) by Tomomichi Kato

AR by Chunjing Qiu on behalf of the Authors (27 May 2019) Author's response Manuscript

ED: Publish as is (26 Jun 2019) by Tomomichi Kato

AR by Chunjing Qiu on behalf of the Authors (27 Jun 2019) Manuscript

Short summary

We present a model that can simulate the dynamics of peatland area extent and the vertical buildup of peat. The model is validated across a range of northern peatland sites and over the Northern Hemisphere (> 30° N). It is able to reproduce the spatial extent of northern peatlands and peat carbon accumulation over the Holocene.