the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
A climate-driven, altitudinal transition in rock glacier dynamics detected through integration of geomorphological mapping and InSAR-based kinematics
Abstract. In dry southwestern South Tyrol, Italy, rock glaciers are dominant landforms of the high-mountain cryosphere. Their spatial distribution and degree of activity hold critical information on the past and current state of discontinuous permafrost, and consequently on response potential to climate warming. Traditional geomorphologic mapping, however, owing to the qualitative expert-based nature, typically displays a high degree of uncertainty and variability among operators with respect to the dynamic classification of intact (permafrost bearing) and relict (permafrost devoid) rock glaciers. This limits the reliability of geomorphologic rock glacier inventories for basic and applied purposes. To address this limitation: (i) we conduct a systematic evaluation of the improvements that InSAR-based information can afford to the detection and dynamic classification of rock glaciers; and (ii) build an integrated inventory that wishes to combine the strengths of geomorphologic- and InSAR-based approaches. To exploit fully InSAR-based information towards a better understanding of the topo-climatic conditions that sustain creeping permafrost, we further explore how velocity and the spatial distribution of moving areas (MAs) within rock glaciers may vary as a function of simple topographic variables known to exert first-order controls on incoming solar radiation, such as elevation and aspect. Starting from the compilation of a geomorphologic inventory (n = 789), we characterize the kinematics of InSAR-based MAs and the relevant hosting rock glaciers on thirty-six Sentinel-1 interferograms computed over 6- through 342-day baselines in the 2018–19 period. With respect to the original inventory, InSAR analysis allowed identifying 14 previously undetected rock glaciers. Further, it confirmed that 246 (76 %) landforms, originally interpreted as intact, do exhibit detectable movement (i.e., ≥1 cm yr-1), and that 270 (60 %) of the relict labelled counterparts do not, whereas 144 (18 %) resulted kinematically undefined due to decorrelation. Most importantly, InSAR proved critical for reclassifying 121 (15 %) rock glaciers, clarifying that 41 (13 %) of those interpreted as intact, do not exhibit detectable movement, and that 80 (17 %) of the original relict ones do actually move. Reclassification, by increasing the altitudinal overlap between intact and relict rock glaciers depicts a broad transition belt in the aspect-elevation space, the amplitude of which varies from as little as 50 m on west facing slopes to a maximum of 500 m on easterly ones. This finding deteriorates the significance of elevation and aspect as topographic proxies for modelling permafrost occurrence, and highlights the importance of using InSAR for informing such models. From a process-oriented standpoint, InSAR information proves fundamental for imaging how this altitudinal transition manifests through changing rates and styles of rock glacier surface deformation. Specifically, we find that as rock glaciers move faster, an increasingly larger proportion of their surface becomes kinematically involved (i.e., percent MA cover), and that this proportion increases with elevation up to the 2600–2800 m, beyond which an inflection occurs and consistent average values are attained. Considering that the inflection falls between the -1 °C and -2 °C MAAT – the lower boundary for discontinuous permafrost – and is independent of slope gradient, we conclude that this altitudinal pattern represents a geomorphic signature: the dynamic expression of increasing permafrost distribution (i.e., from sporadic to discontinuous), until optimal thermal conditions are reached.
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RC1: 'Comment on tc-2023-143', Remya Namboodiri, 23 Jan 2024
Thank you for the opportunity to review your paper title"A climate-driven, altitudinal transition in rock glacier dynamics detected through integration of geomorphological mapping and InSAR-based kinematics." The study focuses on the use of InSAR-based information to improve the detection and dynamic classification of rock glaciers in the dry southwestern South Tyrol, Italy. Traditional geomorphologic mapping faces challenges in accurately classifying intact and relict rock glaciers. The research combines InSAR data with geomorphologic approaches to create a more reliable inventory. The findings highlight the significance of InSAR in identifying previously undetected rock glaciers, reclassifying their status, and providing insights into the altitudinal transition of permafrost distribution. The study also emphasizes the importance of InSAR for modelling permafrost occurrence and understanding the dynamics of rock glacier surface deformation in response to changing rates and styles of movement. Overall, I find the study to be valuable, addressing the challenges in accurately classifying rock glaciers and emphasizing the importance of InSAR technology in enhancing inventory reliability.
I have some specific comments that, if incorporated, could further strengthen the study, and contribute to its successful publication.
Abstract:
To enhance clarity and conciseness, the abstract should be streamlined while preserving key objectives and novel contributions. Organize it with a clear structure by introducing the problem, detailing methods, presenting findings, drawing conclusions, and outlining implications. Explicitly highlight the study's significant contributions, ensuring each sentence is concise and contributes to the overall coherence of the abstract.
Introduction:
- Incorporate a more comprehensive background on the significance of rock glaciers within the context of permafrost and climate change. Refer to relevant recent literature such as Karjalainen et al., 2020, Pruessner et al., 2022, to strengthen the introduction.
- Introduce a structured guide in the introduction to lead readers through the paper's organization, highlighting key components to be discussed. This will provide a stronger foundation for comprehension.
- Clearly state the study's objectives in the introduction. Articulate the problem the research aims to address, providing a robust rationale for the study.
Study Area
- The description of the study area is comprehensive and provides essential details regarding the rugged mountain terrain in the north-eastern portion of the Ortles-Cevedale massif. The inclusion of elevation ranges, key valleys, and bedrock geology contributes to a clear understanding of the study context.
- The information on climate and permafrost occurrence is valuable. However, it will enhance the reader's understanding if you briefly mention the limitations or uncertainties associated with the climate and permafrost data, especially if there are variations in these parameters.
- Also, if the the authors can address potential challenges related to the chosen boundaries, terrain characteristics, or data constraints that might influence the study outcomes.
Data collection and analysis
3.1
- Authors please explicitly mention the sources of the optical imagery (2014, 2017, 2020) and LiDAR-derived hill shade raster (2006). This clarification will provide readers with a clear understanding of the data utilized.
- It will be preferable while the explanation of dynamic classification in detailed, consider summarizing it briefly or using a bulleted list for easy reference.
- When referring to previous studies (e.g., Brardinoni et al., 2019; Haeberli, 1985), consider providing brief context about the study to help readers access additional information.
- Provide a concise clarification or rationale for merging active and inactive landforms into the "intact" category, referring to Haeberli (1985) and Barsch (1996) as appropriate. Also clarify the rationale behind choosing the 1 cm displacement threshold and its relevance to the study's timeframe.
3.2
- The mention of the InSAR-based kinematic characterization is clear but consider providing a summary or overview of the methodology in this section.
- Ensure consistent terminology throughout the document. For example, if "kinematic characterization" and "kinematic classification" are used interchangeably, clarify their relationship, or use the term consistently.
3.2.1
- Specify the exact periods in September to October of 2018 and 2019 when the acquisitions were made. Providing specific dates or a more precise timeframe would enhance clarity.
- While the document is likely targeted at a technical audience, it's important to define technical terms or acronyms, such as LOS (Line of Sight)
- When discussing underestimation of ground deformation due to the LOS, provide a brief explanation of the consequences or implications of such underestimation in the context of the study.
- If appropriate, consider using subheadings in the section discussing limitations and challenges of InSAR measurements.
- Please use consistent units for displacement measurements (e.g., cm, meters) to avoid confusion.
- In Equation 1, ensure that the variable 𝑈 is defined or referred to in the text, so readers can understand its significance.
3.2.2
- Provide a brief explanation of why the minimum area threshold of 20 adjacent pixels is chosen. What significance does this threshold have, and how does it contribute to the consistency and accuracy of the inventorying process?
- Elaborate on the criteria used for assigning velocity classes based on the change in colour observed on the wrapped interferograms. Explain how these classes are indicative of different movement rates, and clarify any assumptions made during this classification.
- Briefly discuss the limitations associated with the choice of a maximum temporal baseline of one year and its implications for velocity detection. This would help readers understand the study's constraints and potential sources of uncertainty.
- Ensure consistency in units throughout the section, especially when expressing velocity classes. For example, use consistent units such as cm/yr for clarity.
3.2.3
- Provide explicit criteria for classifying rock glaciers into the categories of moving, not moving, and undefined.
- Elaborate on the rationale behind assigning the median class to a rock glacier hosting multiple moving areas with diverse kinematics. Explain why more weight is given to the largest moving area closest to the rock glacier front.
- Justify the chosen categories for kinematic classification (e.g., cm/yr, cm to dm/yr, etc.). Provide a rationale for these divisions and discuss how they contribute to the understanding of rock glacier dynamics.
- Discuss any temporal considerations in the kinematic classification process. For instance, mention if the classification is based on an annual average or if there are seasonal variations considered.
- Clearly state the sources of data or observations used for the kinematic analysis. If there are specific interferograms or datasets used in this analysis, refer to them explicitly.
- Address potential sources of uncertainty in the kinematic classification process. Discuss how factors like layover, shadowing, atmospheric artifacts, phase bias, or decorrelation.
Results
- The text is generally well-structured and logically organized. Consider providing a brief introductory paragraph to set the context and purpose of the study before delving into specific sections.
- There is a slight repetition in phrases like "moving areas" and "rock glaciers." Consider using synonyms occasionally for better readability.
- Ensure consistent use of terminology. For instance, the text uses both "rock glacier fronts" and "rock glacier polygons." Clarify if these terms refer to distinct features or are used interchangeably.
- Given the complexity of InSAR analysis, consider adding a brief explanation or reference for readers who may not be familiar with the technique. This can enhance the accessibility of your findings. Also, emphasize the significance of integrating the geomorphologic and InSAR approaches earlier in the section to highlight the study's methodology and its contribution to understanding rock glacier dynamics.
- Maintain consistency in the use of abbreviations and acronyms throughout the text. Ensure that abbreviations are defined upon first use.
- The analysis of the altitudinal distribution of moving areas is clear. However, provide more context or potential explanations for the observed dependence on slope aspect and the remarkable gap on south-facing slopes for faster moving areas.
- The analysis of the size of moving areas is well-presented. Consider briefly discussing the implications of the distinctive peak in median size for areas moving at 30-100 cm yr-1.
- Discuss the absence of an obvious correlation between moving area size and slope aspect. Elaborate on the implications of this finding and how it aligns or contrasts with expectations.
- The observation that moving area size does not appear to correlate with elevation is notable. Provide some insight or hypothesis on why this might be the case and discuss its significance.
- Discuss the factors that might contribute to the observed variability in total moving area below 2500 m a.s.l. Provide possible explanations for cases where the entire rock glacier surface moves versus cases with less than 10% moving extent.
- Offer insights into the observed scatter for rock glaciers moving at cm annual rates and the abrupt drop in scatter for faster rock glaciers. Relate these observations to the overall dynamics and behaviour of rock glaciers.
- Consider concluding the section of the results with a brief transition or summary statement that leads into the future part of the study. This will help maintain a smooth flow in the narrative.
Discussion
- Compilation of a rock glacier inventory is crucial for understanding challenges associated with the changing high-mountain cryosphere. It will be better if the authors can add aids in evaluating responses to warmer climate conditions, from transitioning to relict morphologies to destabilization with increased velocity.
- Please discuss potential biases introduced by the integration of InSAR data, such as the reliance on elevation for dynamic classification. Are there alternative methods to mitigate such biases.
- Consider adding a section discussing the potential implications of the findings for future research and applications in high-mountain cryosphere studies.
- Ensure that the citations are up-to-date, and if possible, include the most recent studies in the field to strengthen the discussion.
Conclusion
- Authors, please acknowledge the contribution of InSAR to geomorphologic inventory reliability.
- Authors, please address potential limitations or challenges associated with future work.
- Provide further clarification on the implications of the increase in altitudinal overlap between relict and intact rock glaciers.
The conclusions section provides valuable insights into the contributions of InSAR technology and the implications for understanding rock glacier dynamics. Addressing the suggestions can further enhance the clarity and impact of the conclusions.
Comment on Figures
Figure 1: The horizontal line graph showing the temporal baselines for both ascending and descending passes is cluttered. I suggest you to replace the line graph with a bar graph with dates along the x axis and the baseline days along the y axis. Easier to interpret that way. Also panel a map doesn’t show any useful information. Can you instead zoom into the two valleys instead and show a DEM or even a Sentinel-1 backscatter map. That would set the InSAR context.
Figure 2: Can the schematic be better shown? The orange boxes show a show of sub parameters and variables (which is OK and is explained in text) that could be better represented In the flowchart. Especially the classification part from ‘moving areas’ to ‘rock glaciers’ box where you show multiple lines characterizing different moving areas at different velocities in cm/yr. to rock glacier velocities in different units other than only cm/yr. (see one of my comments above regarding this).
Figure 3: I see a few issues here. Showing the whole area ‘including’ RG1 and RG2 masks a lot of internal information within RG1 and RG2. To show fringes more clearly I would strongly suggest to redo the figure showing only the RG1 and RG2 ROIs as it is and remove the other areas. Secondly, how do you delineate regions in terms of no fringes, noisy one, decorrelated ones and complete fringes? I suggest to remove those tags from the figures and let the readers understand from the text. The legend used for the fringe scale needs to be changed. The reader now has to use their ‘math’ brain to calculate the displacement. Can we make it simpler and use discrete range of values from RG1 and RG2 ranges? Figure 4a and 7: I am slightly confused by the directions here in the x-axis. Where is the origin here? What I mean is when you say N, where is North with respect to RG1 and RG2. The y axis label is RG front elevation. So RG means both Rock Glaciers or just one? Please clarify. And what I miss in Figure 7 is also this spatial reference with respect to which glacier you are referring to. Maybe a small inset map showing the direction could help?
Is Figure 6 MISSING?
Figure 11: It seems like in panel b, there are values above 3000m masl, but the secondary Y-axis only shows range up to 3000m. In panel a, what is slope (m/m) what is m/m?
Figure 14: The same problem as above with the y axis masl ranges in both lower and higher ends. Also the box plots with the sample numbers tagged above looks cluttered and busy. What is the relevance of sample numbers in this figure? If its not used in the analysis, I suggest you to remove them.
Citation: https://doi.org/10.5194/tc-2023-143-RC1 -
AC1: 'Reply on RC1', Francesco Brardinoni, 10 Mar 2024
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2023-143/tc-2023-143-AC1-supplement.pdf
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RC2: 'Comment on tc-2023-143', Anonymous Referee #2, 24 Jan 2024
The paper A climate driven, altitudinal transition in rock glaciers dynamics detected through integration of geomorphological mapping and InSAR-based kinematics (authors: Bertone et al.) presents a rock glacier inventory in the western South Tirol established through a combined geomorphic approach and InSAR analysis. The research underscores the significance of InSAR in inventorying rock glaciers and assessing their surface kinematics. The paper is clearly structured and well-illustrated, containing sufficient critical reflections and arriving at appropriate conclusions. The methodology is rigorous and consistent, integrating several complementing techniques, whit data supporting the interpretations. The results align with the findings and there are no factual errors. Therefore, I recommend accepting the manuscript with minor revisions. These are outlined below.
- It is not clear if for this study area previous rock glacier inventories were compiled. Please, clearly refer to this issue in the Introduction and refer to the nearby inventories.
- Line 126: what type of optical imagery you used?
- 4b: the bars should correspond to altitude intervals not to altitude values. Please correct the elevation values below the graph either by shifting all the values to the left, or replace it with elevation intervals.
- Line 298: Can you shortly present here the elevation range of all the moving areas?
- Based on the InSAR analysis 14 new rock glaciers were detected (fig. 6). I think it would be useful to shortly presents the elevation range of these rock glaciers.
- Fig 6: 144 rock glaciers could not be classified, which means around 18% of the total inventory. For these rock glaciers (RG) you`ve used the geomorphologic criteria, which seems logical. However, it might be necessary to address this issue in the Discussion section, particularly when discussing the limitations. Perhaps, the notion to convey could be that the geomorphic interpretation should not be entirely supplanted by InSAR; instead a combination of both approaches is deemed desirable.
- Lines 348-349: You mention that the upper altitudinal limit of slow-moving areas (1-3 cm) are 300 m below the other faster classes. However, in Fig. 7a, this distinction is not very clear (please correct me if I`m mistaken). It appears that the upper green dots fall between 3000 and 3200 m, similar to the other graphs. In 7b, c and d the upper dots occur a bit higher, but certainly not with a difference of 300 m. Please double-check! Additionally, high-velocity MA`s (> 1m) do not seem to occur at very high elevations. There are several RG below 2600 m which move very rapidly (which might be interesting to investigate further in the future), even if they fall below the elevation band 2600-2800 m, where the majority of the intact rock glaciers are found. However, it seems that very fast rock glaciers are not strongly constrained by elevation. An analysis over a more extended period of time might help to understand their recent behavior.
- Line 365: I think it might be useful to create a graph similar with 4b for intact/relict RG after considering the velocity because otherwise, it might be confusing. Ultimately, the rock glacier inventory based on InSAR data represents the final version of this work. Upon examining these figures it becomes apparent that no intact RG occurs below 2200 m (fig. 4b), whereas in 8b there are MAs below 2000 m. These low-altitude permafrost sites might also be an interesting finding of this work, so I recommend briefly referring to this in the Discussion (similar sites are found in various locations below 2000 m across mid-latitude mountains). Earlier, I asked you to present the elevation range of the 14 new rock glaciers detected because I am curious to know if these occur particularly at lower elevations.
- Lines 379-380: you are correct, but the number of RG above 2900 m is also significantly low and this should be taken into consideration as well.
- Lines 393-394: This is an interesting finding, but keep in mind that the most extended RG in generally are not necessary moving the fastest presently. Additionally, in this study, I don`t believe the fastest rock glaciers are necessarily the most extended (please correct me if I`m mistaken). As you are aware, there are other factors influencing their extent, such as the duration of activity, contributing area, lithology and structural conditions etc.
- Figure 15: This is a very useful graph, but what is somehow surprising is the big number of intact RG occurring at MAAT above -1o Maybe would be interesting to add other few isotherm with a different color and to discuss on the reliability of this theoretical threshold (-1o C or -2o C) for discontinuous permafrost, respectively to refer to a threshold for sporadic permafrost in Tirol because it seems that there are enough moving areas/intact rock glaciers in areas with positive MAAT.
- Lines 587-588: it`s hard to determine the importance of erosion rates for the acceleration of RGs in South Tirol. The reality is that using only a 1-year interval of velocity measurements makes it challenging to draw definitive conclusions. This could be related to various factors such as: snow cover regime, characteristics of the zero curtain, the freezing period in the active layer, intense summer rainfalls among others.
Citation: https://doi.org/10.5194/tc-2023-143-RC2 -
AC2: 'Reply on RC2', Francesco Brardinoni, 10 Mar 2024
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2023-143/tc-2023-143-AC2-supplement.pdf
Status: closed
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RC1: 'Comment on tc-2023-143', Remya Namboodiri, 23 Jan 2024
Thank you for the opportunity to review your paper title"A climate-driven, altitudinal transition in rock glacier dynamics detected through integration of geomorphological mapping and InSAR-based kinematics." The study focuses on the use of InSAR-based information to improve the detection and dynamic classification of rock glaciers in the dry southwestern South Tyrol, Italy. Traditional geomorphologic mapping faces challenges in accurately classifying intact and relict rock glaciers. The research combines InSAR data with geomorphologic approaches to create a more reliable inventory. The findings highlight the significance of InSAR in identifying previously undetected rock glaciers, reclassifying their status, and providing insights into the altitudinal transition of permafrost distribution. The study also emphasizes the importance of InSAR for modelling permafrost occurrence and understanding the dynamics of rock glacier surface deformation in response to changing rates and styles of movement. Overall, I find the study to be valuable, addressing the challenges in accurately classifying rock glaciers and emphasizing the importance of InSAR technology in enhancing inventory reliability.
I have some specific comments that, if incorporated, could further strengthen the study, and contribute to its successful publication.
Abstract:
To enhance clarity and conciseness, the abstract should be streamlined while preserving key objectives and novel contributions. Organize it with a clear structure by introducing the problem, detailing methods, presenting findings, drawing conclusions, and outlining implications. Explicitly highlight the study's significant contributions, ensuring each sentence is concise and contributes to the overall coherence of the abstract.
Introduction:
- Incorporate a more comprehensive background on the significance of rock glaciers within the context of permafrost and climate change. Refer to relevant recent literature such as Karjalainen et al., 2020, Pruessner et al., 2022, to strengthen the introduction.
- Introduce a structured guide in the introduction to lead readers through the paper's organization, highlighting key components to be discussed. This will provide a stronger foundation for comprehension.
- Clearly state the study's objectives in the introduction. Articulate the problem the research aims to address, providing a robust rationale for the study.
Study Area
- The description of the study area is comprehensive and provides essential details regarding the rugged mountain terrain in the north-eastern portion of the Ortles-Cevedale massif. The inclusion of elevation ranges, key valleys, and bedrock geology contributes to a clear understanding of the study context.
- The information on climate and permafrost occurrence is valuable. However, it will enhance the reader's understanding if you briefly mention the limitations or uncertainties associated with the climate and permafrost data, especially if there are variations in these parameters.
- Also, if the the authors can address potential challenges related to the chosen boundaries, terrain characteristics, or data constraints that might influence the study outcomes.
Data collection and analysis
3.1
- Authors please explicitly mention the sources of the optical imagery (2014, 2017, 2020) and LiDAR-derived hill shade raster (2006). This clarification will provide readers with a clear understanding of the data utilized.
- It will be preferable while the explanation of dynamic classification in detailed, consider summarizing it briefly or using a bulleted list for easy reference.
- When referring to previous studies (e.g., Brardinoni et al., 2019; Haeberli, 1985), consider providing brief context about the study to help readers access additional information.
- Provide a concise clarification or rationale for merging active and inactive landforms into the "intact" category, referring to Haeberli (1985) and Barsch (1996) as appropriate. Also clarify the rationale behind choosing the 1 cm displacement threshold and its relevance to the study's timeframe.
3.2
- The mention of the InSAR-based kinematic characterization is clear but consider providing a summary or overview of the methodology in this section.
- Ensure consistent terminology throughout the document. For example, if "kinematic characterization" and "kinematic classification" are used interchangeably, clarify their relationship, or use the term consistently.
3.2.1
- Specify the exact periods in September to October of 2018 and 2019 when the acquisitions were made. Providing specific dates or a more precise timeframe would enhance clarity.
- While the document is likely targeted at a technical audience, it's important to define technical terms or acronyms, such as LOS (Line of Sight)
- When discussing underestimation of ground deformation due to the LOS, provide a brief explanation of the consequences or implications of such underestimation in the context of the study.
- If appropriate, consider using subheadings in the section discussing limitations and challenges of InSAR measurements.
- Please use consistent units for displacement measurements (e.g., cm, meters) to avoid confusion.
- In Equation 1, ensure that the variable 𝑈 is defined or referred to in the text, so readers can understand its significance.
3.2.2
- Provide a brief explanation of why the minimum area threshold of 20 adjacent pixels is chosen. What significance does this threshold have, and how does it contribute to the consistency and accuracy of the inventorying process?
- Elaborate on the criteria used for assigning velocity classes based on the change in colour observed on the wrapped interferograms. Explain how these classes are indicative of different movement rates, and clarify any assumptions made during this classification.
- Briefly discuss the limitations associated with the choice of a maximum temporal baseline of one year and its implications for velocity detection. This would help readers understand the study's constraints and potential sources of uncertainty.
- Ensure consistency in units throughout the section, especially when expressing velocity classes. For example, use consistent units such as cm/yr for clarity.
3.2.3
- Provide explicit criteria for classifying rock glaciers into the categories of moving, not moving, and undefined.
- Elaborate on the rationale behind assigning the median class to a rock glacier hosting multiple moving areas with diverse kinematics. Explain why more weight is given to the largest moving area closest to the rock glacier front.
- Justify the chosen categories for kinematic classification (e.g., cm/yr, cm to dm/yr, etc.). Provide a rationale for these divisions and discuss how they contribute to the understanding of rock glacier dynamics.
- Discuss any temporal considerations in the kinematic classification process. For instance, mention if the classification is based on an annual average or if there are seasonal variations considered.
- Clearly state the sources of data or observations used for the kinematic analysis. If there are specific interferograms or datasets used in this analysis, refer to them explicitly.
- Address potential sources of uncertainty in the kinematic classification process. Discuss how factors like layover, shadowing, atmospheric artifacts, phase bias, or decorrelation.
Results
- The text is generally well-structured and logically organized. Consider providing a brief introductory paragraph to set the context and purpose of the study before delving into specific sections.
- There is a slight repetition in phrases like "moving areas" and "rock glaciers." Consider using synonyms occasionally for better readability.
- Ensure consistent use of terminology. For instance, the text uses both "rock glacier fronts" and "rock glacier polygons." Clarify if these terms refer to distinct features or are used interchangeably.
- Given the complexity of InSAR analysis, consider adding a brief explanation or reference for readers who may not be familiar with the technique. This can enhance the accessibility of your findings. Also, emphasize the significance of integrating the geomorphologic and InSAR approaches earlier in the section to highlight the study's methodology and its contribution to understanding rock glacier dynamics.
- Maintain consistency in the use of abbreviations and acronyms throughout the text. Ensure that abbreviations are defined upon first use.
- The analysis of the altitudinal distribution of moving areas is clear. However, provide more context or potential explanations for the observed dependence on slope aspect and the remarkable gap on south-facing slopes for faster moving areas.
- The analysis of the size of moving areas is well-presented. Consider briefly discussing the implications of the distinctive peak in median size for areas moving at 30-100 cm yr-1.
- Discuss the absence of an obvious correlation between moving area size and slope aspect. Elaborate on the implications of this finding and how it aligns or contrasts with expectations.
- The observation that moving area size does not appear to correlate with elevation is notable. Provide some insight or hypothesis on why this might be the case and discuss its significance.
- Discuss the factors that might contribute to the observed variability in total moving area below 2500 m a.s.l. Provide possible explanations for cases where the entire rock glacier surface moves versus cases with less than 10% moving extent.
- Offer insights into the observed scatter for rock glaciers moving at cm annual rates and the abrupt drop in scatter for faster rock glaciers. Relate these observations to the overall dynamics and behaviour of rock glaciers.
- Consider concluding the section of the results with a brief transition or summary statement that leads into the future part of the study. This will help maintain a smooth flow in the narrative.
Discussion
- Compilation of a rock glacier inventory is crucial for understanding challenges associated with the changing high-mountain cryosphere. It will be better if the authors can add aids in evaluating responses to warmer climate conditions, from transitioning to relict morphologies to destabilization with increased velocity.
- Please discuss potential biases introduced by the integration of InSAR data, such as the reliance on elevation for dynamic classification. Are there alternative methods to mitigate such biases.
- Consider adding a section discussing the potential implications of the findings for future research and applications in high-mountain cryosphere studies.
- Ensure that the citations are up-to-date, and if possible, include the most recent studies in the field to strengthen the discussion.
Conclusion
- Authors, please acknowledge the contribution of InSAR to geomorphologic inventory reliability.
- Authors, please address potential limitations or challenges associated with future work.
- Provide further clarification on the implications of the increase in altitudinal overlap between relict and intact rock glaciers.
The conclusions section provides valuable insights into the contributions of InSAR technology and the implications for understanding rock glacier dynamics. Addressing the suggestions can further enhance the clarity and impact of the conclusions.
Comment on Figures
Figure 1: The horizontal line graph showing the temporal baselines for both ascending and descending passes is cluttered. I suggest you to replace the line graph with a bar graph with dates along the x axis and the baseline days along the y axis. Easier to interpret that way. Also panel a map doesn’t show any useful information. Can you instead zoom into the two valleys instead and show a DEM or even a Sentinel-1 backscatter map. That would set the InSAR context.
Figure 2: Can the schematic be better shown? The orange boxes show a show of sub parameters and variables (which is OK and is explained in text) that could be better represented In the flowchart. Especially the classification part from ‘moving areas’ to ‘rock glaciers’ box where you show multiple lines characterizing different moving areas at different velocities in cm/yr. to rock glacier velocities in different units other than only cm/yr. (see one of my comments above regarding this).
Figure 3: I see a few issues here. Showing the whole area ‘including’ RG1 and RG2 masks a lot of internal information within RG1 and RG2. To show fringes more clearly I would strongly suggest to redo the figure showing only the RG1 and RG2 ROIs as it is and remove the other areas. Secondly, how do you delineate regions in terms of no fringes, noisy one, decorrelated ones and complete fringes? I suggest to remove those tags from the figures and let the readers understand from the text. The legend used for the fringe scale needs to be changed. The reader now has to use their ‘math’ brain to calculate the displacement. Can we make it simpler and use discrete range of values from RG1 and RG2 ranges? Figure 4a and 7: I am slightly confused by the directions here in the x-axis. Where is the origin here? What I mean is when you say N, where is North with respect to RG1 and RG2. The y axis label is RG front elevation. So RG means both Rock Glaciers or just one? Please clarify. And what I miss in Figure 7 is also this spatial reference with respect to which glacier you are referring to. Maybe a small inset map showing the direction could help?
Is Figure 6 MISSING?
Figure 11: It seems like in panel b, there are values above 3000m masl, but the secondary Y-axis only shows range up to 3000m. In panel a, what is slope (m/m) what is m/m?
Figure 14: The same problem as above with the y axis masl ranges in both lower and higher ends. Also the box plots with the sample numbers tagged above looks cluttered and busy. What is the relevance of sample numbers in this figure? If its not used in the analysis, I suggest you to remove them.
Citation: https://doi.org/10.5194/tc-2023-143-RC1 -
AC1: 'Reply on RC1', Francesco Brardinoni, 10 Mar 2024
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2023-143/tc-2023-143-AC1-supplement.pdf
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RC2: 'Comment on tc-2023-143', Anonymous Referee #2, 24 Jan 2024
The paper A climate driven, altitudinal transition in rock glaciers dynamics detected through integration of geomorphological mapping and InSAR-based kinematics (authors: Bertone et al.) presents a rock glacier inventory in the western South Tirol established through a combined geomorphic approach and InSAR analysis. The research underscores the significance of InSAR in inventorying rock glaciers and assessing their surface kinematics. The paper is clearly structured and well-illustrated, containing sufficient critical reflections and arriving at appropriate conclusions. The methodology is rigorous and consistent, integrating several complementing techniques, whit data supporting the interpretations. The results align with the findings and there are no factual errors. Therefore, I recommend accepting the manuscript with minor revisions. These are outlined below.
- It is not clear if for this study area previous rock glacier inventories were compiled. Please, clearly refer to this issue in the Introduction and refer to the nearby inventories.
- Line 126: what type of optical imagery you used?
- 4b: the bars should correspond to altitude intervals not to altitude values. Please correct the elevation values below the graph either by shifting all the values to the left, or replace it with elevation intervals.
- Line 298: Can you shortly present here the elevation range of all the moving areas?
- Based on the InSAR analysis 14 new rock glaciers were detected (fig. 6). I think it would be useful to shortly presents the elevation range of these rock glaciers.
- Fig 6: 144 rock glaciers could not be classified, which means around 18% of the total inventory. For these rock glaciers (RG) you`ve used the geomorphologic criteria, which seems logical. However, it might be necessary to address this issue in the Discussion section, particularly when discussing the limitations. Perhaps, the notion to convey could be that the geomorphic interpretation should not be entirely supplanted by InSAR; instead a combination of both approaches is deemed desirable.
- Lines 348-349: You mention that the upper altitudinal limit of slow-moving areas (1-3 cm) are 300 m below the other faster classes. However, in Fig. 7a, this distinction is not very clear (please correct me if I`m mistaken). It appears that the upper green dots fall between 3000 and 3200 m, similar to the other graphs. In 7b, c and d the upper dots occur a bit higher, but certainly not with a difference of 300 m. Please double-check! Additionally, high-velocity MA`s (> 1m) do not seem to occur at very high elevations. There are several RG below 2600 m which move very rapidly (which might be interesting to investigate further in the future), even if they fall below the elevation band 2600-2800 m, where the majority of the intact rock glaciers are found. However, it seems that very fast rock glaciers are not strongly constrained by elevation. An analysis over a more extended period of time might help to understand their recent behavior.
- Line 365: I think it might be useful to create a graph similar with 4b for intact/relict RG after considering the velocity because otherwise, it might be confusing. Ultimately, the rock glacier inventory based on InSAR data represents the final version of this work. Upon examining these figures it becomes apparent that no intact RG occurs below 2200 m (fig. 4b), whereas in 8b there are MAs below 2000 m. These low-altitude permafrost sites might also be an interesting finding of this work, so I recommend briefly referring to this in the Discussion (similar sites are found in various locations below 2000 m across mid-latitude mountains). Earlier, I asked you to present the elevation range of the 14 new rock glaciers detected because I am curious to know if these occur particularly at lower elevations.
- Lines 379-380: you are correct, but the number of RG above 2900 m is also significantly low and this should be taken into consideration as well.
- Lines 393-394: This is an interesting finding, but keep in mind that the most extended RG in generally are not necessary moving the fastest presently. Additionally, in this study, I don`t believe the fastest rock glaciers are necessarily the most extended (please correct me if I`m mistaken). As you are aware, there are other factors influencing their extent, such as the duration of activity, contributing area, lithology and structural conditions etc.
- Figure 15: This is a very useful graph, but what is somehow surprising is the big number of intact RG occurring at MAAT above -1o Maybe would be interesting to add other few isotherm with a different color and to discuss on the reliability of this theoretical threshold (-1o C or -2o C) for discontinuous permafrost, respectively to refer to a threshold for sporadic permafrost in Tirol because it seems that there are enough moving areas/intact rock glaciers in areas with positive MAAT.
- Lines 587-588: it`s hard to determine the importance of erosion rates for the acceleration of RGs in South Tirol. The reality is that using only a 1-year interval of velocity measurements makes it challenging to draw definitive conclusions. This could be related to various factors such as: snow cover regime, characteristics of the zero curtain, the freezing period in the active layer, intense summer rainfalls among others.
Citation: https://doi.org/10.5194/tc-2023-143-RC2 -
AC2: 'Reply on RC2', Francesco Brardinoni, 10 Mar 2024
The comment was uploaded in the form of a supplement: https://tc.copernicus.org/preprints/tc-2023-143/tc-2023-143-AC2-supplement.pdf
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