Coupled land surface–subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

Tran, Anh Phuong; Dafflon, Baptiste; Hubbard, Susan S.

doi:https://doi.org/10.5194/tc-11-2089-2017

Articles | Volume 11, issue 5

https://doi.org/10.5194/tc-11-2089-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/tc-11-2089-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 11, issue 5

Research article

|

06 Sep 2017

Research article |

| 06 Sep 2017

Coupled land surface–subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

Anh Phuong Tran, Baptiste Dafflon, and Susan S. Hubbard

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Final revised paper (published on 06 Sep 2017)
Preprint (discussion started on 07 Feb 2017)

Interactive discussion

Status: closed

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

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RC1: 'Review', Anonymous Referee #1, 09 Mar 2017
- AC1: 'Reply to comment from reviewer 1', Anh Phuong tran, 14 May 2017
RC2: 'Coupled Land Surface-Subsurface Hydrogeophysical Inverse Modeling to Estimate Soil Organic Content and explore associated Hydrological and Thermal Dynamics in an Arctic Tundra', Anonymous Referee #2, 20 Apr 2017
- AC2: 'Reply to the reviewer 2', Anh Phuong tran, 14 May 2017

Peer-review completion

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

AR by Anh Phuong tran on behalf of the Authors (14 May 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (16 May 2017) by Julia Boike

RR by Anonymous Referee #1 (29 May 2017)

Suggestions for revision or reasons for rejection

I have also reviewed the first version of the manuscript and the authors have revised most of my comments.

I have still some reservations regarding some parts of the manuscript where the authors are urgently requested to be formally correct in their wording: As the authors state clearly in their response to my first review, there is no direct relationship between OC and electrical resistivity. In their conclusions of the revised version, they again state (P. 22, L 16-17) „we concentrated on the impact of OC content on the soil electrical resistivity via its hydrological-thermal properties“. Formally and physically correct, only properties or states that influence electrical conduction can influence measured electrical resistivity. The most important ones are clay content, dissolved ions in the water phase in combination with the continuity of the water phase which allows electrical conduction, and temperature. Most other properties only have indirect effects on electrical resistivity as they are mostly (often non-linearly) related to one (or even some at the same time) of the properties stated above. I know that there are many hydrogeophysical applications that follow a similar approach, however, it is important to stick to the physical basis of the processes. Consequently, the wording needs to be carefully revised in this respect.

Besides all the challenges at unfrozen conditions, this is particularly important as soon as the soil becomes frozen and, hence, the water phase becomes discontinuous causing the characteristic drop in electrical resistivity during freezing. This effect is not considered by the empirical Archie’s Law. I did a quick literature scan mayself and found some work by Hauck and collaborators who did some nice work employing ERT in periglacial and glacial environments. So the authors may take a look at these publications. For this manuscript, it should be ok to include a review about application of Archie’s Law in permafrost research which also mentions the difficulty with using this equation and discusses the limits of the approach followed in this study. Formalizing this process correctly, which would mean finding a better equation than Archie’s Law, could be one grand challenge in future research to really establish ERT for quantitatively investigating freeze/thaw and related processes.

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RR by Anonymous Referee #2 (14 Jun 2017)

ED: Reconsider after major revisions (16 Jun 2017) by Julia Boike

AR by Anna Mirena Feist-Polner on behalf of the Authors (24 Jul 2017) Author's response

ED: Publish as is (04 Aug 2017) by Julia Boike

Short summary

Soil organics carbon (SOC) and its influence on terrestrial ecosystem feedbacks to global warming in permafrost regions are particularly important for the prediction of future climate variation. Our study proposes a new surface–subsurface, joint deterministic–stochastic hydrological–thermal–geophysical inversion approach and documents the benefit of including multiple types of data to estimate the vertical profile of SOC content and its influence on hydrological–thermal dynamics.