Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3

Westermann, S.; Langer, M.; Boike, J.; Heikenfeld, M.; Peter, M.; Etzelmüller, B.; Krinner, G.

doi:https://doi.org/10.5194/gmd-9-523-2016

Articles | Volume 9, issue 2

https://doi.org/10.5194/gmd-9-523-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/gmd-9-523-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 9, issue 2

Model description paper

|

08 Feb 2016

Model description paper |

| 08 Feb 2016

Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3

S. Westermann, M. Langer, J. Boike, M. Heikenfeld, M. Peter, B. Etzelmüller, and G. Krinner

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Final revised paper (published on 08 Feb 2016)
Supplement to the final revised paper
Preprint (discussion started on 26 Aug 2015)

Interactive discussion

Status: closed

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

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- Supplement

SC C1986: 'Executive Editor Comment on "Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3"', Astrid Kerkweg, 15 Sep 2015
- AC C3089: 'Reply to Executive Editor comment', Sebastian Westermann, 26 Nov 2015
RC C2252: 'Review of Westermann et al.', Anonymous Referee #1, 29 Sep 2015
- AC C3090: 'Reply to Referee #1', Sebastian Westermann, 26 Nov 2015
RC C2288: 'Review of Westerman etal. CryoGrid 3', Anonymous Referee #2, 30 Sep 2015
- AC C3091: 'Reply to Referee #2', Sebastian Westermann, 26 Nov 2015
RC C2539: 'REVIEW: SIMULATING THE THERMAL REGIME AND THAW PROCESSES OF ICE-RICH PERMAFROST GROUND WITH THE LAND-SURFACE MODEL CRYOGRID 3 BY WESTERMANN ET AL.', Anonymous Referee #3, 19 Oct 2015
- AC C3092: 'Reply to referee #3', Sebastian Westermann, 26 Nov 2015

Peer-review completion

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

AR by Sebastian Westermann on behalf of the Authors (26 Nov 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Nov 2015) by Jeremy Fyke

RR by Anonymous Referee #2 (23 Dec 2015)

Suggestions for revision or reasons for rejection

The paper describes the complexities of modeling ice-rich permafrost thaw. The model or the data description has not changed much since the last version of the paper. Some interesting temperature data has been added from a thaw lake, this data looks very nice.
Some concerns also remain in the paper:
1) L97: Soil hydrology is not accounted for. You need to explain why! This may be the single most important variable that explains inter-annual variability of thaw depth and it determines subsidence versus thaw lake formation.
2) L573: Why do you expect a thaw depth difference from different snow density? Permafrost temperature? Heat capacity is so much smaller compared to latent heat from thaw. I would take this out, it does not add to the paper.
3) L580: The surface temperatures in Figure 2 are really not that great, I understand that this is largely due to the reanalysis versus observed data, but why than state that surface temperatures were in good agreement? I see up to a 10 degree C difference in observed and modeled. Why not show some time series to see if the trends are good?
4) L595: Buoyancy-driven thermal stratification has nothing to do with the temperature mismatch you point out from Figure 6. The heat comes from the sediment and no temperature rises above 4 degrees, so all water remains stable. It is more likely that the thermal conductivity of the sediment is underestimated.
5) L597: A future suggestion for improvement of the model, during spring only allow mixing of the layers with ice.
6) L644: Why partly? There is plenty of temperature increase to explain the entire warming.
7) L645-650: Is this driven by sea ice decline?
8) L722: Improve the performance? I doubt it will simulate faster maybe improve accuracy?
9) L789-791: see comment above
10) L815: There is not enough energy entering the ground to melt the active layer and after that ice rich permafrost, in order to melt several meters of ice rich permafrost in less than a decade, without first seriously damaging the existing biomass and active layer. Looking carefully at Figure 7 and 8 I see, but have a hard time seeing the details, that the active layer is thinner on top of the rapidly degrading permafrost section (numerical instability?). Unless it got suddenly much warmer or a fire came through the area, I do not see that this is realistic. The onset of the rapid thaw is also earlier in the cooler climate scenario that does not make any sense, some explanation and careful analysis needs to be given for this difference.
11) L839: What is it about the Euler solution that will make people want to change this code? Maybe they will be frustrated by it and replace it with something more sophisticated? I would think that those areas that people want to modify are simple and the rest of the code is robust to allow those changes without problems.
12) L846 surface temperatures, I see little proof in the paper that the surface temperatures are adequately reproduced.
Specific edits:
L15 add “the” thaw process
L57 remove “a”
L458 add “as”
L501 add soft return
L602 remove “It is remarkable that rather modest” and fix sentence
L647 change “is” to “its”
L664 remove “in”

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ED: Publish subject to minor revisions (Editor review) (06 Jan 2016) by Jeremy Fyke

AR by Sebastian Westermann on behalf of the Authors (20 Jan 2016) Author's response Manuscript

ED: Publish subject to technical corrections (22 Jan 2016) by Jeremy Fyke

Thank you for your final response to the Reviewer. Please consider this article accepted pending a final proof. In particular I suggest the following, mostly grammatical, changes:

L.54: Revise sentence to: “ To predict future landscape development in a warming climate that is intimately linked to the carbon cycle of these areas, new and robust model approaches are needed which can potentially be implemented in the land-surface schemes of Earth System Models (ESMs).”

L66: “be by directly” -> “be directly”

L349: “400 and 600 m” -> “400-600 m”

L393: “are ongoing” -> “have been ongoing

L531: “can very well reproduce measured surface temperatures” -> “can reproduce measured surface temperatures very well”

L547: “in particularly” -> “, particularly”

L571: “considerably too early” -> “abnormally early”

L580: “ We emphasize that the average of 150 point measurements of thaw depth is displayed in Fig. 5, while a considerable spatial variability occurs (average standard deviation of 0.06m ) due to variable ground and surface properties.” -> “ We emphasize that the average of 150 point measurements of thaw depth displayed in Fig. 5, masks considerable spatial variability (average standard deviation of 0.06m ) due to variable ground and surface properties.”

L584: “dynamics all of which” -> “dynamics, all of which”

L591: “Fig. 6 is clear evidence” -> “Fig. 6 presents clear evidence”

L682: “and more” -> “or more”

L698: “already for a the moderate warming scenarios RCP 4.5” -> “even for the moderate RCP4.5 scenario”

L701: “, while expanding” -> “and expand”

L727: “Hereby, in particular” -> “Specifically, ”

L730: “, but also more flexible… could be incorporated.” -> “, and more flexible… could also be incorporated.”

L745 “highly feasible” -> “sufficient”

L747: “constitutes” -> “provides”

L768: “facilitates comparing” -> “facilitates comparison of”

L769: “qualitatively” -> “qualitative”

L773: “can clearly document” -> “clearly documents”

L789: “, while it” -> “, while in nature it”

L814: “in particular of” -> “of (in particular)”

L816: “3D-variability” > “3D variability”

L819: “in areas, where” -> “in areas where”

L820: remove word “already”

L823: “The simulations” -> “The simulations presented here”

L841: “are encouraging that” -> “provide encouragement that”

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AR by Sebastian Westermann on behalf of the Authors (23 Jan 2016) Author's response Manuscript

Short summary

Thawing of permafrost is governed by a complex interplay of different processes, of which only conductive heat transfer is taken into account in most model studies. We present a new land-surface scheme designed for permafrost applications, CryoGrid 3, which constitutes a flexible platform to explore new parameterizations for a range of permafrost processes.