Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

Maier, Nathan; Gimbert, Florent; Gillet-Chaulet, Fabien; Gilbert, Adrien

doi:https://doi.org/10.5194/tc-15-1435-2021

Articles | Volume 15, issue 3

https://doi.org/10.5194/tc-15-1435-2021

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

https://doi.org/10.5194/tc-15-1435-2021

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

Articles | Volume 15, issue 3

Research article

|

22 Mar 2021

Research article |

| 22 Mar 2021

Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

Nathan Maier, Florent Gimbert, Fabien Gillet-Chaulet, and Adrien Gilbert

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Final revised paper (published on 22 Mar 2021)
Supplement to the final revised paper
Preprint (discussion started on 04 Aug 2020)
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 Maier et al.', Bradley Lipovsky, 13 Oct 2020
- AC1: 'Response to reviewer comments.', NATHAN Maier, 13 Nov 2020
RC2: 'Review of Maier et al', Anonymous Referee #2, 20 Oct 2020
- AC2: 'Response to reviewer comments.', NATHAN Maier, 13 Nov 2020

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (15 Nov 2020) by Joseph MacGregor

AR by Nathan Maier on behalf of the Authors (16 Nov 2020) Author's response Manuscript

ED: Publish subject to revisions (further review by editor and referees) (16 Nov 2020) by Joseph MacGregor

ED: Referee Nomination & Report Request started (30 Nov 2020) by Joseph MacGregor

RR by Bradley Lipovsky (05 Jan 2021)

RR by Anonymous Referee #2 (19 Jan 2021)

Suggestions for revision or reasons for rejection

The authors give very thorough and thoughtful replies to our comments, which I greatly appreciate. I was a bit struck that the replies were so thorough, yet when I compare the manuscripts, there aren’t nearly as many edits as I expected. I was definitely appeased by the thorough replies, but have some remaining concerns with how these comments were translated into the text. (For example, the reply to my comment about basal drag and driving stress was very thorough and highlighted the similarity between models up to “high velocities” of 300 m/yr. No edits to the text reflect this.)

I would still like to see more de-emphasis of the conclusion that this model works everywhere, even in fast flowing locations. This is true for the text as a whole, but particularly in the abstract and conclusion (which is what most people will read). Some care is taken in the text to emphasize the complexity in fast flow given that only 5% of the data cover velocities >450 m/yr, and the models diverge there. In the conclusion you state that the models work well over “grounded regions” – which is unclear to me. Aside from NEGIS and the floating ice tongues, the whole ice sheet is grounded, even the fast flowing (>1000 m/yr) regions. And, in the abstract, the issue of model performance at high velocities is simply de-emphasized with a brush-off generalization (“relationships are captured reasonably well by simple traction laws over the entire velocity range, including regions with velocities over 100 m/yr”). The last part of this sentence is really not supported by your results, which show complexity and are also data poor.

Perhaps my definition of fast flowing is just different from yours. In places (e.g. line 331) where you specify fast and slow regions, please add detail about what that means (and not just the max velocity, but the mean velocity in that region). I have a feeling in the manuscript, you’re considering ~400 m/yr as fast flowing, whereas several readers will have different perspectives.

Line 510: what do you mean by “partially floating regions of the ice sheet”? Where are these regions? I suspect several of them are the high velocity (>1000 m/yr) regions that are giving me such pause.

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ED: Publish subject to minor revisions (review by editor) (20 Jan 2021) by Joseph MacGregor

AR by Nathan Maier on behalf of the Authors (27 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (28 Jan 2021) by Joseph MacGregor

AR by Nathan Maier on behalf of the Authors (01 Feb 2021) Manuscript

Short summary

In Greenland, ice motion and the surface geometry depend on the friction at the bed. We use satellite measurements and modeling to determine how ice speeds and friction are related across the ice sheet. The relationships indicate that ice flowing over bed bumps sets the friction across most of the ice sheet's on-land regions. This result helps simplify and improve our understanding of how ice motion will change in the future.