Iceberg calving of Thwaites Glacier, West Antarctica: full-Stokes modeling combined with linear elastic fracture mechanics

Yu, Hongju; Rignot, Eric; Morlighem, Mathieu; Seroussi, Helene

doi:https://doi.org/10.5194/tc-11-1283-2017

Articles | Volume 11, issue 3

https://doi.org/10.5194/tc-11-1283-2017

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

https://doi.org/10.5194/tc-11-1283-2017

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

Articles | Volume 11, issue 3

Research article

|

30 May 2017

Research article |

| 30 May 2017

Iceberg calving of Thwaites Glacier, West Antarctica: full-Stokes modeling combined with linear elastic fracture mechanics

Hongju Yu, Eric Rignot, Mathieu Morlighem, and Helene Seroussi

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Final revised paper (published on 30 May 2017)
Supplement to the final revised paper
Preprint (discussion started on 09 Nov 2016)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review', Till Wagner, 14 Dec 2016
RC2: 'Review of Yu et al.', Jeremy Bassis, 20 Dec 2016
SC1: 'Quick comment on calving criterion', Joe Todd, 04 Jan 2017
AC1: 'Author response of "Iceberg calving of Thwaites Glacier, West Antarctica: Full-Stokes modeling combined with linear elastic fracture mechanics"', Hongju Yu, 09 Feb 2017

Peer-review completion

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

AR by Hongju Yu on behalf of the Authors (09 Feb 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 Mar 2017) by David M Holland

RR by Till Wagner (04 Apr 2017)

Suggestions for revision or reasons for rejection

I commend the reviewers for comprehensively addressing my comments. I believe the manuscript to be much improved and regard it worthy of publication, subject to some minor revisions (which I will detail below). Overall, I still found a number of typos and grammatical errors (some of which I'll point out below), and I urge the authors to address these issues in the next round of revisions.

page 1

l.5 "match the distribution" appears somewhat strong, since the observed crevasse dimensions are significantly more spread out than the modeled ones. I suggest "are consistent with the distribution".
Furthermore, the authors discuss the mismatch of the observed and modeled crevasse widths, but there is no mention of the modeled surface crevasses being restricted to much smaller depths than the observed distribution. An acknowledgment of this mismatch (and speculative explanation?) may be in order.

page 2

l.6 suggested rewrite: "The calving of icebergs is difficult to model because the processes involved, such as the initiation, propagation, and orientation of crevasses are not well understood, and direct observations are rare..."

l.20 "In this study, however, ..." I do not quite understand this sentence.

l.24 rewrite: "The model simulations are conducted ..."

page 5

l.13 "matches the observed surface velocity"

l.15 "Here, the simulation time is short, ..."

l.26 "For SSA and HO, zb is known because ..."

page 6

l.6 "In order to obtain a realistic ..."

l.18 a textbook reference for the three modes of fracture may be worthwhile

l.25 the authors fixed the typo in eq (20), but it appears that the following text has not been updated. Presumably it should read something like, "\sigma_xx' = \sigma_xx + p, is the deviatoric stress, with \sigma_xx being the longitudinal stress and p ..."

page 7

l.20 I would suggest moving the requirement of minimum depth being smaller than 1 m up to line 3 of the page (specifying under what conditions the K>Kc criterion actually leads to crevasse propagation).

l.25 "20 m width to 60-70m..."

l.32 There seems to be something wrong with this sentence.

page 8

l.22 "The initial crevasse positions ..."

l.26 "In the fourth set of experiments ..."

page 9

l.18 I would suggest renaming this subsection maybe "Deviation from hydrostatic equilibrium"

l.30 "... downstream of the grounding line."

page 10

l.1 It should be stated that the crevasse stops growing when K falls below Kc.

l.26 "...stops growing."

page 11

l.16 "Over time, the stress at ..."

page 12

l.11 This statement appears too strong. Suggested rewrite: "This conclusion may help reconcile the previous studies ..."

l.17/18 the revised sentence needs rewriting

l.23 "With these additions ..."

l.26 I'd suggest spelling out Thwaites Glacier here (rather than TG).

l.30 "... that assume hydrostatic equilibrium ..."

Fig 5:
The colors between panels (a) and (b) don't match. The blue profiles (12 and 13) have the grounding line retreat back to x~700 km. In panel (b) the grounding line profiles appear as if they increase monotonically (i.e., not showing the hysteresis loop).

Fig 7, caption: Which experiment is the modeled data is from? Labels of horizontal and vertical axes should be consistent (i.e., specify or leave out "surface"/"bottom" on both).

Fig 8: It is difficult to distinguish between the red and the magenta curves (maybe use green or some other color instead). If I read this figure correctly, crevasse propagation can happen only if a given curve goes through the bottom right quadrant? Maybe this can be highlighted visually, with shading or a box?

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RR by Jeremy Bassis (04 Apr 2017)

ED: Publish subject to minor revisions (Editor review) (04 Apr 2017) by David M Holland

AR by Hongju Yu on behalf of the Authors (13 Apr 2017) Author's response Manuscript

ED: Publish as is (21 Apr 2017) by David M Holland

AR by Hongju Yu on behalf of the Authors (21 Apr 2017)

Short summary

We combine 2-D ice flow model with linear elastic fracture mechanics (LEFM) to model the calving behavior of Thwaites Glacier, West Antarctica. We find the combination of full-Stokes (FS) model and LEFM produces crevasses that are consistent with observations. We also find that calving is enhanced with pre-existing surface crevasses, shorter ice shelves or undercut at the ice shelf front. We conclude that the FS/LEFM combination is capable of constraining crevasse formation and iceberg calving.