Unravelling the evolution of Zmuttgletscher and its debris cover since the end of the Little Ice Age

Mölg, Nico; Bolch, Tobias; Walter, Andrea; Vieli, Andreas

doi:https://doi.org/10.5194/tc-13-1889-2019

Articles | Volume 13, issue 7

https://doi.org/10.5194/tc-13-1889-2019

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

https://doi.org/10.5194/tc-13-1889-2019

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

Articles | Volume 13, issue 7

Research article

|

11 Jul 2019

Research article |

| 11 Jul 2019

Unravelling the evolution of Zmuttgletscher and its debris cover since the end of the Little Ice Age

Nico Mölg, Tobias Bolch, Andrea Walter, and Andreas Vieli

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Final revised paper (published on 11 Jul 2019)
Supplement to the final revised paper
Preprint (discussion started on 18 Jan 2019)
Supplement to the preprint

Interactive discussion

Status: closed

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

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RC1: 'Review of Molg et al', David Rounce, 01 Feb 2019
RC2: 'Review of Mölg et al.', Philip Kraaijenbrink, 15 Feb 2019
AC1: 'Final response to both reviews', Nico Mölg, 01 Apr 2019
EC1: 'Editor response to the authors', Etienne Berthier, 09 Apr 2019

Peer-review completion

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

AR by Anna Mirena Feist-Polner on behalf of the Authors (10 May 2019) Author's response

ED: Referee Nomination & Report Request started (13 May 2019) by Etienne Berthier

RR by Philip Kraaijenbrink (29 May 2019)

RR by David Rounce (13 Jun 2019)

Suggestions for revision or reasons for rejection

The paper has significantly improved and reads very well. The content is excellent and the discussion is well written. The only significant comments regard figures and use of acronyms. I recommend accepting for publication after these minor/technical revisions are addressed.

Specific comments:
- Are acronyms for "TMG", "SBG", etc. really necessary? Perhaps for figures to save space (and then they should be stated in each caption), but given space is not an issue electronically and these only save several letters, I highly suggest avoiding the use of needless acronyms that only reduce readability by having the reader by having to look them up constantly.
- Figure 4: There doesn't seem to be any statement of comparing to the other glaciers like there was for Figure 3. Add this statement otherwise the reader is left wondering why all these other glaciers are shown. Zmuttgletscher should be the first in the legend and it should also be more pronounced (perhaps a thicker line, black color, or both). The abbreviations are not provided in the caption. It also seems unnecessary to have these glacier name abbreviations only one time in the text (especially for the study area glacier!). I highly recommend providing the full names, which may be possible if the legend is one column. If you still favor abbreviations, then the abbreviations should be stated in the caption. Additionally, "Zmuttgletscher shows a relatively modest retreat..." - this sentence belongs in the text, not in the caption, and then makes sense as to why you add the other glaciers and address the first part of this comment.
- Figure 8: The labels are now acronyms of acronyms. This is very confusing and a bit ridiculous. Just state SBG1, SBG2, TMG1, TMG2 if you're limited for space in the inset figure.
- Figure 9: The plot is very misleading as it shows periods of time that are not equidistant; ex. the first one is 16 years and the second is 6 years, but they have the same space between. I would plot the years and then plot the values at the mid-points as this would show the time more accurately. Also, it'd be nice to be able to compare the timing of these changes with the data in Table 3. I would recommend plotting Table 3 as subfigures to Figure 9. This is why having the actual time on the x-axis would be nice as well. This would allow one to see that in 1983-1988, there was also a decrease in debris-covered glacier area.
- Supplementary table captions should be above tables like the text
- Supplementary figures 7-16 appear to be the same as Figure 10 - delete these in the supplement (also they should each have a proper caption if they were to remain for some reason)

Minor comments:
P1, L13 - delete "with decadal"
P1, L16 - "by comparison"
P1, L19 - glacier "has" been quasi-stagnant
P1, L20 - in "the" surface slope
P1, L24 - decreasing glacier dynamics sounds odd. More accurate would be decreasing flux divergence, ice flux, or whatever way the authors would prefer to state this.
P2, L16 - (iv) "long-term (> decade) glacier-scale studies have mostly..."
P2, L28 - add reference for long response times (>50 years)
P3, L8 - weather "systems"
P3, L9 - change units to m in order to be consistent with the next line of m w.e.
P3, L14 - Zmuttgletscher "has" several independent...
P3, L20 - "mainly fed by TMG and to a lesser extent..."
P4, L6 - our analysis "is" based
P5, L4 - new paragraph seems unnecessary
P5, L8 - using "the Topo-to-Raster tool in ArcGIS."
P5, L13 - "and then georeferenced"
P5, L17 - "the number of images and image quality..."
P5, L28 - ... "(1859), Siegfried map (1879), all available orthophotos, and Swisstop (...) by manual digitization"
P5, L29 - Swisstopo images? maps? stating simply "Swisstopo" sounds odd
P6, L1 - "The time series of maps and orthophotos resulted in glacier area values ..."
P6, L2 - "debris-covered areas" compared to...
P6, L2 - of "these" images
P6, L12 - influence "of" debris cover
P6, L14 - glacier boundary "and" the start and end of the length profile", respectively ..."
Figure 2 - state in the caption that c & d are looking at Tiefmattengletscher to provide the reader with the proper context for looking at the images
P7, L2 - the "long-term elevation change data"
P7, L9 - delete "results of upper transect see Figure 7a" as this is unnecessary
P7, L11 - "However, for debris thicknesses greater than" 20 cm...
P7, L14 - add the time periods used by each station in the parentheses since you provide the elevation and distance from the site. I would also switch the order to be consistent with the text (i.e., close to study site, similar elevation, long period)
P7, L20 - into four "sections" and eleven...
P7, L26 - Between "August 22-24 2017"...
P7, L27 - replace "today's" terminus with the year. Many years from now "today's" terminus will not be accurate. I would suggest this for each use of "today" in the text
P8, L10 - specify "9b"
P8, L15 - A glacier's elevation change gradient is typically inclined towards ... - this sentence is very confusing to read. Please clarify. The gradient is a number, so inclining a number doesn't make sense.
P8, L35 - accounted for "due to a" lack of such data
P9, L6 - delete "negative at"
P9, L8 - Zmuttgletscher "had less" mass loss
P9, L8 - add citation for Swiss mean
P10, L14 - delete ~12.9% of the entire glacier area, and move this to the next line, so it reads "resulting in an increase in percent debris cover from ~12.9% to 31.8+/-0.06% of the glacier area from ~1850 to 2013." Also, add error for the 12.9% if able to do so, since you show it for the 2013 image.
P10, L21 - and "now is" close to the foot...
P11, L8 - from "less than" 5 cm to "greater than" 70 cm
P11, L16 - seven "week" period
P11, L17 - if stating "Ostrem-like" behavior then should add reference to the Ostrem study here
P12, L6 - The "middle" section ... - this is then consistent with term middle in Figure 8
P12, L20 - delete "and more"
P13, L21 - The use of "on average" with all the years sounds like it's setting up an average for the time period, only to realize that it's meant for spatial average; hence, I would recommend something along the lines of "Since 1879, the average thinning over the ablation area has been 104.7...". Although even here, I would suggest putting the value in m/yr because 104 m is a lot but it lacks the context to be able to compare it to all the other thinning rates mentioned in this paragraph.
P15, L7 - delete "rather"
P15, L18 - which "provide" a clear picture
P15, L30 - delete "in our case"
P16, L31 - develop "a" more negative mass balance
P17, L9 - delete "points"
P18, L10 - Table S15 doesn't exist
P21, L28 - Recommend changing Owen to "O." to be consistent with the other acknowledgements.

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ED: Publish subject to technical corrections (17 Jun 2019) by Etienne Berthier

Dear Authors,

Both referees have now read your revised manuscript (MS) and yours responses. They are generally enthusiastic about your revisions. As you will read, they did a fantastic job at evaluating your paper a second time and I would like to acknowledge them.

They (and myself) also have some, mostly minor, corrections that will help you finalize properly your MS. Thanks for considering them carefully.

Do not hesitate to contact me if you have some further questions.

Best regards,

Etienne Berthier

Single general comment
The contribution of 1.5 days of radar interferometry measurement is so negligible to your story that it could be skipped. To really focus the paper and not district the reader.

Technical corrections.
Table 1. Dh not defined yet (I think)
5.23. Maybe remind here the date of the reference DEM to which all others are coregistered.
7.19 too large rather than too big. (I think).
8.30 Does not really make sense to have a section 3.6.1 if you do not have 3.6.2.
Table 2. Even if you write "annual" I think it is good for clarity that the unit in the table is set to m/yr. To avoid any mis-understanding.
Do your glacier-wide mass balance agrees with the one from Fischer et al., TC, 2015 when cumulated over a similar period? It would be a nice sanity check.
Figure 7. The last sentence of the caption appears to be incomplete.
16.32. Minus sign missing in front of the mass balance.
18.10. Not clear why you say “comparatively high” here and then provide the example of Findeleng. where the area loss is even larger.
19.14. The same statement applies I think to Argentière Glacier in the French Alps (see Vincent, C., Soruco, A., Six, D. and Le Meur, E.: Glacier thickening and decay analysis from 50 years of glaciological observations performed on Glacier d’Argentière, Mont Blanc area, France, Ann. Glaciol., 50(50), 73–79, doi:10.3189/172756409787769500, 2009.)
20.19. I had a hard time tracking back the 5% contribution of ice cliff to the glacier-wide mass balance. Better explain how you calculated this 5% value (if not already done)
20.25 and 20.29 are mostly repetitions.

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AR by Nico Mölg on behalf of the Authors (26 Jun 2019) Author's response Manuscript

Short summary

Debris can partly protect glaciers from melting. But many debris-covered glaciers change similar to debris-free glaciers. To better understand the debris influence we investigated 150 years of evolution of Zmutt Glacier in Switzerland. We found an increase in debris extent over time and a link to glacier flow velocity changes. We also found an influence of debris on the melt locally, but only a small volume change reduction over the whole glacier, also because of the influence of ice cliffs.