Ice-stream flow switching by up-ice propagation of instabilities along glacial marginal troughs

Brouard, Etienne; Lajeunesse, Patrick

doi:https://doi.org/10.5194/tc-13-981-2019

Articles | Volume 13, issue 3

https://doi.org/10.5194/tc-13-981-2019

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

https://doi.org/10.5194/tc-13-981-2019

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

Articles | Volume 13, issue 3

Research article

|

22 Mar 2019

Research article |

| 22 Mar 2019

Ice-stream flow switching by up-ice propagation of instabilities along glacial marginal troughs

Etienne Brouard and Patrick Lajeunesse

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Final revised paper (published on 22 Mar 2019)
Preprint (discussion started on 02 Oct 2018)

Interactive discussion

Status: closed

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

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RC1: 'manuscript review', Anonymous Referee #1, 18 Oct 2018
RC2: 'review of tc-2018-196', Anonymous Referee #2, 06 Nov 2018
EC1: 'Editor Comment', Chris R. Stokes, 30 Nov 2018
AC1: 'Authors response to comments', Etienne Brouard, 23 Jan 2019
EC2: 'Editor Comment', Chris R. Stokes, 30 Jan 2019

Peer-review completion

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

AR by Etienne Brouard on behalf of the Authors (23 Jan 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Jan 2019) by Chris R. Stokes

RR by Anonymous Referee #2 (15 Feb 2019)

Suggestions for revision or reasons for rejection

Following the advice from the first round of review, the authors have revised their manuscript into a regular format. I think the paper benefits from that and I consider the study well laid out now, with clearly described objectives, methods, results, and their implications.

I would recommend the authors to give the manuscript at least one more proper read – there is a lot of typos and omissions. The authors might also consider having the text proof-read by a colleague to further work on the style – the phrasing is a little weird at places and it does not read all that well.

Detailed comments:
L 18 ‘…competition for ice discharge between ice streams, which implies piracy of ice-drainage basins via marginal troughs…’ This is a weird statement: competition for ice discharge between ice streams does not have to automatically imply piracy of drainage basins through via marginal troughs.
L19-20 ‘the union of ice catchment by piracy’ I suggest to possibly rephrase it to ‘the enlargement of its ice catchment by piracy…’
L 25 West Antarctic Ice Sheet
L 34-35 ‘data …. are needed’ (data is the plural of datum)
L 64-65 ‘The glacial overdeepening of the troughs probably began during the late Pliocene’ – up until some ten years ago, the extent of glaciation on the shelf was debated for the LGM, one of the coldest periods of the Pleistocene. In the Late Pliocene the ocean was significantly warmer and the cold parts of the climate fluctuations were shorter and less pronounced. The cross shelf troughs might be younger than the fiords: the troughs being a product of fully-fledged ice sheets while the fiords might have been repeatedly incised by the gradually growing forms of glaciation in the Late Cenozoic.
L 68 Ice streams in plural
L 67-69 The sentence is weirdly worded after ‘i.e.’, I don’t fully understand.
L 75 Either extended to the shelf break or reached the shelf break, having both is unnecessarily complicated.
L 77 There’s some uncertainty on the dating so it would be better to write ‘until ca. 14.1 cal ka BP’. Also, I find it unnecessary to write ‘cal. ka’ – in general context, ‘ka’ is now used for absolute/calendar time not for radiocarbon.
L 80 Not ‘up to’ but ‘from as early as’
L 81 the presence of
L 90 ‘The specifics of acquisition’ consider rewording
L 95 ‘The complete surface was transferred in ESRI ArcMap 10.2 software 95 geomorphological mapping and topographic analyses.’ Something is missing in that sentence.
L 96-98 Change to ‘Individual landforms were digitised in ArcMap 10.2 and interpreted based on their apparent character (width, length, orientation, etc.) and relevant literature (e.g., Dowdeswell et al., 2016b).’
L 125 marked by a steep wall
L 130 delete one Fiord
L 144 Delete ‘s’ in ‘Troughs’
L 173 The term ‘wet bed glaciers’ is somewhat uncommon (Google Scholar only gives five hits) – I would recommend to change it o ‘warm-based glaciers’.
L 179 lineations
L 184 ‘Cross-cut by grounding-zone wedges’ this phrasing is somewhat unfortunate. It migh be better to write that the areas with MSGLs are at places overprinted / covered by GZW or something in that sense but it’s not really a cross-cutting relationship.
L 188 Like instead of alike
L 193 King first than Jezek in the REF
L 243 in the same way
L 270 ‘steering along was’ – something missing in that sentence?
L 332-333 Delete the repeated citation.
L 391 ‘… and leads’’
L 411 provide

Formatting comment:
Order of references in the in-text citations: it should be ordered chronologically not alphabetically

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ED: Publish subject to minor revisions (review by editor) (19 Feb 2019) by Chris R. Stokes

AR by Etienne Brouard on behalf of the Authors (27 Feb 2019) Author's response Manuscript

ED: Publish as is (05 Mar 2019) by Chris R. Stokes

Short summary

Modifications in ice-stream networks have major impacts on ice sheet mass balance and global sea level. However, the mechanisms controlling ice-stream switching remain poorly understood. We report a flow switch in an ice-stream system that occurred on the Baffin Island shelf through the erosion of a marginal trough. Up-ice propagation of ice streams through marginal troughs can lead to the piracy of neighboring ice catchments, which induces an adjacent ice-stream switch and shutdown.