the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Jan 2025
Distribution and characteristics of supraglacial channels on mountain glaciers in Valais, Switzerland
Abstract. Supraglacial channels form a key component of glacier hydrology, transporting surface meltwater to englacial and proglacial positions, which impacts ice flow dynamics, surface mass balance and the hydrochemistry of glacial runoff. The presence of supraglacial channels is well-documented on ice sheets using satellite imagery, but little is known about their distribution and characteristics on smaller mountain glaciers because most channels fall below the resolution of freely-available satellite imagery. Here we use high-resolution (0.15 m) orthophotos to delineate <2000 supraglacial channels (> 0.5 m wide) across a sample of 285 glaciers, 85 of which contain channels, in Valais Canton, Switzerland, and investigate their distribution and characteristics. We find that glacier hypsometry, size and slope are good predictors of drainage density, with glaciers characterised by lower relief slopes (with fewer crevasses) and larger ablation areas (high meltwater supply) exhibiting higher drainage densities. Drainage density is higher when glaciers terminate at mid-range elevations (2600 – 3100 m.a.s.l), likely due to less surface lowering than at lower elevations, which allows channels to persist. On average, 80 % of high order channels run-off supraglacially, with 20 % terminating englacially. However, there is marked inter-glacier variability in where channels terminate, with 40 % of glaciers containing no englacially-terminating channels, versus 3.5 % where all channels are terminate englacially. Most channels are slightly sinuous, with higher sinuosities associated with large, high-order channels that are heavily incised and more likely to reactivate annually. In comparison to ice sheets, the majority of channels reach the terminus supraglacially and little meltwater is stored in lakes.
Competing interests: At least one of the (co-)authors is a member of the editorial board of The Cryosphere. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.-
Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-3894', Anonymous Referee #1, 30 Jan 2025
- AC1: 'Reply on RC1', Holly Wytiahlowsky, 20 Mar 2025
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RC2: 'Comment on egusphere-2024-3894', Anonymous Referee #2, 04 Feb 2025
Please see my comments on the attached document.
- AC2: 'Reply on RC2', Holly Wytiahlowsky, 20 Mar 2025
-
RC3: 'Comment on egusphere-2024-3894', Ian Willis, 21 Feb 2025
- AC3: 'Reply on RC3', Holly Wytiahlowsky, 20 Mar 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-3894', Anonymous Referee #1, 30 Jan 2025
Wytiahlowsky et al. present an extensive analysis of supraglacial channel characteristics for 285 glaciers within the Calais Canton, Switzerland. They manually delineated channels from high-resolution (0.15 m) orthophotos and use these delineations to preform their analysis which included investigating channel characteristics and its relationship to glacier properties. I found the manuscript to be well written and in general easy to follow, with clear and appropriate methodology to support the results and conclusions presented in the manuscript. While supraglacial channel analysis is not necessarily new, the number of channels and individual glaciers characterized in this study is impressive and allows for the understanding of supraglacial hydrology on a regional scale, which is very exciting for the field of glacial hydrology. The results of this work contribute to furthering the scientific understanding of supraglacial hydrology on alpine glaciers while also acting as a point of comparison for future studies of supraglacial channel formation in other alpine environments. My opinion is that this manuscript is suitable for publication in The Cryosphere. Below I have included some general and specific comments for the authors to review.
General Comments
-Figure 1: The manuscript would benefit from a overview of the glaciers within the Valais Canton. Currently, a lot of space is used to show the region that is not the study area. I would suggest to highlight the values area (as in panel a) but within a smaller area, then use a majority of the space to delineate and show all of the glaciers in the region (currently indicated by blue). A full view of all the glaciers in the area would allow the authors to then color-code them as (1) glaciers too small to be considered in this study <1km^2 (maybe white or gray to denote they are being excluded or alternatively leave them out due to the small size if they are not visible at the scale chosen), (2) glaciers without channels, and (3) glaciers with channels. Panel B does a good job in showing the large Alestsch glacier, however the debris cover is hard to see in panel C. This may be an artifact of the low-resolution of background imagery for figure 1 in the version of the manuscript submitted for review (I understand .png are often submitted early whereas .pdfs are instead used in the final version, if this is the case this last point can be ignored and I will assume the debris cover will be more apparent in the final version). Finally, if possible under the space limitations, it would be nice if some of the glaciers referenced in subsequent figures could be indicated in some way within Figure 1. This would make it easier to put specific glaciers into context when they are directly named later on in the manuscript.
-Figure 4. This is a great figure of the delineated channels, however, it would benefit from the inclusion of insets (or sub panels) that include the entire glacier overlaid elevation contours and annotated with the region with channels shown. By including both a glacier-wide view would help top put the streams into the glacier-wide context which is the focus of this work.
I am curious if glacier aspect has a relationship with channel formation
In referring to the two types of crevasses you see (ones that transport meltwater englacially vs. ones that redirect stream flow). The authors state that the crevasse fills with meltwater and overspills along the crevasse trace. This may be true as is seen in Greenland (e.g., Chudley et al., XXXX) but alternatively, the crevasses may have already advected shut, these old crevasses may then act as a preferential flow path as observed in Fig 8 (I see this frequently in Greenland). I would suggest elaborating on this process in the discussion, as a natural question that would arise would be why is the crevasse not hydrofracturing if it completely full of meltwater. While the answer would be the stress regime in such a case (it would suggest the crevasse is old, having advected into a compressional region). Altogether I feel this process deserves some added clarity within the discussion.
Specific Comments
Comments regarding figures:
Fig 1: expand the description of the yellow start to include that it is a weather station
Fig 2: Do the arrows indicate ice flow or water flow or both? Stating this in the caption would help clarify.
Fig 3: The x-axis labels are hard to see, I think all the font sizes in this figure need to be enlarged. The inclusion of the greater than/less than symbols in the x tick marks clutters the text making it even harder to read. I suggest instead including this information in the legend or using bracket notation.
Figs 3 and 5: I am confused as to what the different colors represent, are they supposed to correspond to something? All of the different colors when one variable is being plotted is confusing. Particularly because different colors are being used in different figures. Note that this comment is only referring to Fig 3c-f, and Fig 5a,b,e-g.
Fig 5. Including an annotation to each of the subplots with the results from the spearman’s rank analysis would be helpful here. Currently the reader has to go back and forth between figures 5 and 6 to interpret the data presented. The x-axis labels in 5d are very hard to read, I would suggest making these larger. Also, the outliers in panels c and d makes it difficult to see the differences between the box and whisker plots. Maybe consider excluding the outliers or adjusting your subplot size/spacing so that the distribution is more clear, particularly in 4c and 5d.
Fi 7. This is a great figure, however, most of the the text in this figure is too small to read. Also, consider either making the ela dashed line bold or a different color (or both so it is easier to see)
Fig 8: I would suggest adding arrows to indicate meltwater flow direction
Fig A2: all labels are too small to see
Manuscript comments:
L63: Here you site WorldView-3 with a ~3.7m resolution, however, this is the short-wave infrared resolution, WorldView-3 has a 31cm panchromatic and a 1.24 m multispectral.
L127-137: There is a lot of information and numbers in this paragraph that becomes hard to follow, consider removing unnecessary information or making a figure or a table to accompany this information.
L141-142: Explicitly state the channel width the method was successful on and then the channel size in this study area.
L143: define the abbreviation NDWI_ice before use.
144: state that you are referring to multispectral here, WV-2 has a 46cm panchromatic resolution.
Paragraph starting on L332: Reference specific tables and figures within the appendix rather than the appendix as a whole.
L354: change “…crevassed area of a glacier, restricting the area” to “…crevassed area of a glacier which restricts the area…”. As phrased it is unclear if your last clause is referencing the preceding clause or entirety of the sentence (which would not make sense), so I suggest removing the final clause for clarity.
L356: the end of this sentence is confusing as written. I suggest rephrasing the sentence to read something like “When crevasses are open they can intercept meltwater and…, crevasses that have closed modify small-scale surface topography and meltwater can be routed along the crevasse trace…” or something like that.
L357: The term “bottom-heavy hypsometries”
L316: I think this should be referencing Figure 5e.
L317: This figure reference may also be incorrect
L371: change to “in order for channels to form”.
L381: change “/“ to “and”, also remove “on” in the phrase “on the runoff hydrograph”
L390: specify lag time here, a lag between what and what? Melt and peak proglacial discharge? If so, state that here.
L393: comma between large and low
L394: Break into two sentences, ending the first at the word “melt”
L400: Define lag times here as well
L400: Here you refer to “main stem segments”, but earlier in the text you referred to stream order. I suggest being consistent with terminology.
L451: change “/“ to “or”
L465: change “additionally” to “The”
L467: do you mean on instead of “and” here?
L470-1: I am not sure if this is true, most debris-covered research has been done in the Himalaya with some in Alaska (e.g., all work by Doug Benn and many others).
L496: add “on” before meltwater routing
L509: mountain glacier environments have glacier lake outburst floods which could cause abrupt acceleration, I would mention this here even though you do not see them in your area. Alternatively, refer to your specific area rather than “mountain glacier environments” more broadly.
Citation: https://doi.org/10.5194/egusphere-2024-3894-RC1 - AC1: 'Reply on RC1', Holly Wytiahlowsky, 20 Mar 2025
-
RC2: 'Comment on egusphere-2024-3894', Anonymous Referee #2, 04 Feb 2025
Please see my comments on the attached document.
- AC2: 'Reply on RC2', Holly Wytiahlowsky, 20 Mar 2025
-
RC3: 'Comment on egusphere-2024-3894', Ian Willis, 21 Feb 2025
- AC3: 'Reply on RC3', Holly Wytiahlowsky, 20 Mar 2025
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- 1
Holly Wytiahlowsky
Chris R. Stokes
Rebecca A. Hodge
Caroline C. Clason
Stewart S. R. Jamieson
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2332 KB) - Metadata XML
Wytiahlowsky et al. present an extensive analysis of supraglacial channel characteristics for 285 glaciers within the Calais Canton, Switzerland. They manually delineated channels from high-resolution (0.15 m) orthophotos and use these delineations to preform their analysis which included investigating channel characteristics and its relationship to glacier properties. I found the manuscript to be well written and in general easy to follow, with clear and appropriate methodology to support the results and conclusions presented in the manuscript. While supraglacial channel analysis is not necessarily new, the number of channels and individual glaciers characterized in this study is impressive and allows for the understanding of supraglacial hydrology on a regional scale, which is very exciting for the field of glacial hydrology. The results of this work contribute to furthering the scientific understanding of supraglacial hydrology on alpine glaciers while also acting as a point of comparison for future studies of supraglacial channel formation in other alpine environments. My opinion is that this manuscript is suitable for publication in The Cryosphere. Below I have included some general and specific comments for the authors to review.
General Comments
-Figure 1: The manuscript would benefit from a overview of the glaciers within the Valais Canton. Currently, a lot of space is used to show the region that is not the study area. I would suggest to highlight the values area (as in panel a) but within a smaller area, then use a majority of the space to delineate and show all of the glaciers in the region (currently indicated by blue). A full view of all the glaciers in the area would allow the authors to then color-code them as (1) glaciers too small to be considered in this study <1km^2 (maybe white or gray to denote they are being excluded or alternatively leave them out due to the small size if they are not visible at the scale chosen), (2) glaciers without channels, and (3) glaciers with channels. Panel B does a good job in showing the large Alestsch glacier, however the debris cover is hard to see in panel C. This may be an artifact of the low-resolution of background imagery for figure 1 in the version of the manuscript submitted for review (I understand .png are often submitted early whereas .pdfs are instead used in the final version, if this is the case this last point can be ignored and I will assume the debris cover will be more apparent in the final version). Finally, if possible under the space limitations, it would be nice if some of the glaciers referenced in subsequent figures could be indicated in some way within Figure 1. This would make it easier to put specific glaciers into context when they are directly named later on in the manuscript.
-Figure 4. This is a great figure of the delineated channels, however, it would benefit from the inclusion of insets (or sub panels) that include the entire glacier overlaid elevation contours and annotated with the region with channels shown. By including both a glacier-wide view would help top put the streams into the glacier-wide context which is the focus of this work.
I am curious if glacier aspect has a relationship with channel formation
In referring to the two types of crevasses you see (ones that transport meltwater englacially vs. ones that redirect stream flow). The authors state that the crevasse fills with meltwater and overspills along the crevasse trace. This may be true as is seen in Greenland (e.g., Chudley et al., XXXX) but alternatively, the crevasses may have already advected shut, these old crevasses may then act as a preferential flow path as observed in Fig 8 (I see this frequently in Greenland). I would suggest elaborating on this process in the discussion, as a natural question that would arise would be why is the crevasse not hydrofracturing if it completely full of meltwater. While the answer would be the stress regime in such a case (it would suggest the crevasse is old, having advected into a compressional region). Altogether I feel this process deserves some added clarity within the discussion.
Specific Comments
Comments regarding figures:
Fig 1: expand the description of the yellow start to include that it is a weather station
Fig 2: Do the arrows indicate ice flow or water flow or both? Stating this in the caption would help clarify.
Fig 3: The x-axis labels are hard to see, I think all the font sizes in this figure need to be enlarged. The inclusion of the greater than/less than symbols in the x tick marks clutters the text making it even harder to read. I suggest instead including this information in the legend or using bracket notation.
Figs 3 and 5: I am confused as to what the different colors represent, are they supposed to correspond to something? All of the different colors when one variable is being plotted is confusing. Particularly because different colors are being used in different figures. Note that this comment is only referring to Fig 3c-f, and Fig 5a,b,e-g.
Fig 5. Including an annotation to each of the subplots with the results from the spearman’s rank analysis would be helpful here. Currently the reader has to go back and forth between figures 5 and 6 to interpret the data presented. The x-axis labels in 5d are very hard to read, I would suggest making these larger. Also, the outliers in panels c and d makes it difficult to see the differences between the box and whisker plots. Maybe consider excluding the outliers or adjusting your subplot size/spacing so that the distribution is more clear, particularly in 4c and 5d.
Fi 7. This is a great figure, however, most of the the text in this figure is too small to read. Also, consider either making the ela dashed line bold or a different color (or both so it is easier to see)
Fig 8: I would suggest adding arrows to indicate meltwater flow direction
Fig A2: all labels are too small to see
Manuscript comments:
L63: Here you site WorldView-3 with a ~3.7m resolution, however, this is the short-wave infrared resolution, WorldView-3 has a 31cm panchromatic and a 1.24 m multispectral.
L127-137: There is a lot of information and numbers in this paragraph that becomes hard to follow, consider removing unnecessary information or making a figure or a table to accompany this information.
L141-142: Explicitly state the channel width the method was successful on and then the channel size in this study area.
L143: define the abbreviation NDWI_ice before use.
144: state that you are referring to multispectral here, WV-2 has a 46cm panchromatic resolution.
Paragraph starting on L332: Reference specific tables and figures within the appendix rather than the appendix as a whole.
L354: change “…crevassed area of a glacier, restricting the area” to “…crevassed area of a glacier which restricts the area…”. As phrased it is unclear if your last clause is referencing the preceding clause or entirety of the sentence (which would not make sense), so I suggest removing the final clause for clarity.
L356: the end of this sentence is confusing as written. I suggest rephrasing the sentence to read something like “When crevasses are open they can intercept meltwater and…, crevasses that have closed modify small-scale surface topography and meltwater can be routed along the crevasse trace…” or something like that.
L357: The term “bottom-heavy hypsometries”
L316: I think this should be referencing Figure 5e.
L317: This figure reference may also be incorrect
L371: change to “in order for channels to form”.
L381: change “/“ to “and”, also remove “on” in the phrase “on the runoff hydrograph”
L390: specify lag time here, a lag between what and what? Melt and peak proglacial discharge? If so, state that here.
L393: comma between large and low
L394: Break into two sentences, ending the first at the word “melt”
L400: Define lag times here as well
L400: Here you refer to “main stem segments”, but earlier in the text you referred to stream order. I suggest being consistent with terminology.
L451: change “/“ to “or”
L465: change “additionally” to “The”
L467: do you mean on instead of “and” here?
L470-1: I am not sure if this is true, most debris-covered research has been done in the Himalaya with some in Alaska (e.g., all work by Doug Benn and many others).
L496: add “on” before meltwater routing
L509: mountain glacier environments have glacier lake outburst floods which could cause abrupt acceleration, I would mention this here even though you do not see them in your area. Alternatively, refer to your specific area rather than “mountain glacier environments” more broadly.