BrAHMs V1.0: a fast, physically based subglacial hydrology model for continental-scale application

Kavanagh, Mark; Tarasov, Lev

doi:https://doi.org/10.5194/gmd-11-3497-2018

Articles | Volume 11, issue 8

https://doi.org/10.5194/gmd-11-3497-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gmd-11-3497-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 11, issue 8

Development and technical paper

|

30 Aug 2018

Development and technical paper |

| 30 Aug 2018

BrAHMs V1.0: a fast, physically based subglacial hydrology model for continental-scale application

Mark Kavanagh and Lev Tarasov

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Final revised paper (published on 30 Aug 2018)
Preprint (discussion started on 28 Nov 2017)

Interactive discussion

Status: closed

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

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SC1: 'Code Accessability.', Lutz Gross, 13 Dec 2017
RC1: 'A novel and worthwhile model, hindered by issues related to reproducibility and scope', Jesse Johnson, 30 Dec 2017
RC2: 'An important model development for palaeo-ice sheet studies.', Julien Seguinot, 13 Feb 2018
AC1: 'Response to reviewer comments and revised manuscript', Lev Tarasov, 26 Apr 2018

Peer-review completion

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

AR by Lev Tarasov on behalf of the Authors (26 Apr 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 May 2018) by Philippe Huybrechts

RR by Jesse Johnson (11 Jun 2018)

Suggestions for revision or reasons for rejection

The authors have provided a detailed and thoughtful response to my initial review. Looking back, my primary concerns were that 1) the numerical experiments were not reproducible because the source code was not well documented, and the coupling not described in detail, 2) that the asynchronous runs might mask numerical instabilities, 3) the design criteria are unclear, and 4) that the summary results relied on metrics and plots that were not that informative.

Issue 1 has been addressed by making the source code available online, and by providing additional text in a number of areas. In particular, the stating inputs and outputs of BrAHMs are instructive. I no longer believe this is an issue.

Issue 2 was closely tied to 3 - in the case of a ice sheet systems model, I had questions about the interaction between ice sheet and hydrology components. The authors have taken care to scope the paper towards the development of the hyrdrology only, with some tests of its function in asynchronous experiments. Rereading, I find this reasonable, and am satisfied with the outcome. Additionally, the authors made efforts to demostrate the stability of the model in a number of ways, for example, figures 2 and 4 are excellent.

Issue 3 - by adding four paragraphs to differentiate between BrAHMs and other large scale ice sheet models including hydrology helps to clarify the importance of this work, and makes many of the questions raised in the original review less relevant.

Issue 4 - Both reviewers made comments on the figures, and I'm glad to see that some changes were made. I also liked the paragraph that acknowledges that local sensitivity may be obscured by looking at bulk results. I'd like the authors to consider, a final time, the possibility that the information density is low in figures 1 and 3 - and that the visual representation obscures potentially interesting details in the spatial distribution of water thickness and pressure. Both reviewers note this. But, if the authors feel strongly, I'm not going to get in the way. Finally, please read a little about colorblindness and the 'jet' color map. I get the sense that these figures are mostly OK because they use only 10 unique colors (good!), but you'd hate to lose audience because of something as superficial as the colormap.

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ED: Publish subject to technical corrections (13 Jul 2018) by Philippe Huybrechts

AR by Lev Tarasov on behalf of the Authors (21 Jul 2018) Author's response Manuscript

Short summary

We present and validate BrAHMs (BAsal Hydrology Model): a new physically based basal hydrology model, which captures the two main types of subglacial drainage systems (high-pressure distributed systems and low-pressure channelized systems). BrAHMs is designed for continental glacial cycle scale contexts, for which computational speed is essential. This speed is accomplished, in part, by numerical methods novel to basal hydrology contexts.