The 21st-century fate of the Mocho-Choshuenco ice cap in southern Chile

Matthias Scheiter, Marius Schaefer, Eduardo Flández, Deniz Bozkurt, and Ralf Greve

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Final revised paper (published on 06 Aug 2021)
Preprint (discussion started on 11 Nov 2020)

Interactive discussion

Status: closed

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

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RC1: 'Review of “21st century fate of the Mocho-Choshuenco ice cap in southern Chile”', Anonymous Referee #1, 12 Jan 2021
- AC1: 'Reply on both anonymous referees', Matthias Scheiter, 11 Mar 2021
RC2: 'Review of Matthias Scheiter et al.', Anonymous Referee #2, 24 Jan 2021
- AC1: 'Reply on both anonymous referees', Matthias Scheiter, 11 Mar 2021

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (22 Mar 2021) by Benjamin Smith

AR by Matthias Scheiter on behalf of the Authors (03 May 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (22 May 2021) by Benjamin Smith

RR by Anonymous Referee #1 (05 Jun 2021)

Suggestions for revision or reasons for rejection

Comments on revised version of “21st century fate of the Mocho-Choshuenco ice cap in southern Chile” by M Scheiter et al.
4 June, 2021

Dear colleagues,

I think this is a very and thorough revision of the study and manuscript. I see that the major changes are an updated surface mass balance parameterization and also a transient spin up to capture the ice cap’s modern disequilibrium. Thanks for taking the time to carefully address these points (which I note the other reviewer raised as well), and nice work integrating them.

The adjusted methods and the reasoning behind them are described well, and I think the new figure panels will help the reader evaluate the model calibration and spinup. Based on these figures/analyses and the updated projections, I agree with you that the model seems to better capture the recent state of the ice cap – and that lends more confidence to the projections

I have just a few remaining comments, which are mostly minor questions of clarity or wording. Hopefully these will be quick to address.

I support publication of the revised manuscript. I think it will make a nice contribution both as a case study for glacier change in this region, and a useful demonstration of applying a 3D ice-flow model to a mountain glacier/ice cap setting.

Comments (line by line)

7: “exposition” – consider changing to aspect, which I think is more familiar and also used later in the manuscript

26-27: “apart from ice dynamics…” – consider re-wording; somewhat confusing to separate these with “apart from”, as ice dynamics relate the climate forcings to glacier change

97: I assume the altitude is the (evolving) ice surface elevation, but perhaps you could specify

134: I think estimating the local warming since 1979 based on both radiosonde and reanalysis is a good approach. This isn’t a criticism, more of a comment: I was just surprised to see it is only a ~0.2 C warming – much less than the global average over this time. Could be worth just pointing that out in case readers have other regions with stronger recent warming in their minds.

136-37: I’m a little confused by this description – shouldn’t the ELA be lowered to make the 1979 steady state?

152: model >> models

176: “of availability of…” – suggest changing to “where both the ELA and… are available”

Fig. 6: I assume this is for the present day (transient) state, not 1979? Consider stating to clarify.

224: suggest “until 2100” >> “by 2100”

256: “ice loss accelerates” – this is thickness change, right? I think I understand what you mean, but consider clarifying as this seems at odds with earlier statement about how the mean curves flatten by 2100 (229).

309: “dynamical processes” – consider wording to “dynamical state”? Or transient state? The spinup to me seems more about capturing the state rather than new processes.

332: Opposed >> as opposed

342: suggest “climate” rather than “circulation” for consistency

364: of advantage >> advantageous

370: Drawback >> a drawback

378: few >> a few (??)

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ED: Publish subject to minor revisions (review by editor) (15 Jun 2021) by Benjamin Smith

AR by Matthias Scheiter on behalf of the Authors (23 Jun 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (25 Jun 2021) by Benjamin Smith

AR by Matthias Scheiter on behalf of the Authors (07 Jul 2021) Manuscript

Short summary

We simulate the current state and future evolution of the Mocho-Choshuenco ice cap in southern Chile (40°S, 72°W) with the ice-sheet model SICOPOLIS. Under different global warming scenarios, we project ice mass losses between 56 % and 97 % by the end of the 21st century. We quantify the uncertainties based on an ensemble of climate models and on the temperature dependence of the equilibrium line altitude. Our results suggest a considerable deglaciation in southern Chile in the next 80 years.