Estimation of Glacier Outline and Volume Changes in the Vilcanota Range Snow-Capped Mountains, Peru, Using Temporal Series of Landsat and a Combination of Satellite Radar and Aerial LIDAR Images

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I'm convinced of the scientific aspects described in the manuscript and their contribution to advancing research in your field. This paper represents a very important contribution. The new dataset allows for extremely interesting observations regarding the relative importance of frontal dynamics versus surface elevation changes in glacier monitoring. The commentary on the correlation between glacier area, precipitation, and air temperature is relevant and illustrates glacier trends over the past decades.

Abstract
Please include information about the methodology.

Line 28: Snow cover area or glacier area?

Introduction
Lines 66–77: This paragraph could be removed.
Line 84: The "; 2004" should be removed.

Materials and Methods
The methods are sufficiently documented to allow for replication studies. The statistical methods are valid and correctly applied.

Regarding the dataset:
Line 237: What is the period of the year during which the images were obtained?
Line 254: The “/estimation” should be removed.
Line 283: Please clarify what “expert-defined shapefiles” refers to.
Line 309: Is the topic volume change or elevation change?
Line 322: What GPS equipment was used in this step?
For Figure 3: Please review the visual quality of this figure.
Please explain the annual glacier volume formula used in this estimation.
Table 1: What is the source of the DEM data from January 3, 2000?

Results and Discussion
Figure 5: The legend should be revised. Is the estimated volume related to snow cover or to the glacier? The graph appears to be about elevation change, in my opinion.
Figure 7: Replace “Yearly” with “Annual.”

Please discuss whether the changes in glaciers have intensified since 2000, 2010, or another period.

Conclusions
The text could be removed because the numerical data in line 502 and 504 are not supported by the methodology.

Comments on the Quality of English Language

This paper represents a very important contribution. The new dataset allows for extremely interesting observations regarding the relative importance of frontal dynamics versus surface elevation changes in glacier monitoring. The commentary on the correlation between glacier area, precipitation, and air temperature is relevant and illustrates glacier trends over the past decades.

Abstract
Please include information about the methodology.

Line 28: Snow cover area or glacier area?

Introduction
Lines 66–77: This paragraph could be removed.
Line 84: The "; 2004" should be removed.

Materials and Methods
The methods are sufficiently documented to allow for replication studies. The statistical methods are valid and correctly applied.

Regarding the dataset:
Line 237: What is the period of the year during which the images were obtained?
Line 254: The “/estimation” should be removed.
Line 283: Please clarify what “expert-defined shapefiles” refers to.
Line 309: Is the topic volume change or elevation change?
Line 322: What GPS equipment was used in this step?
For Figure 3: Please review the visual quality of this figure.
Please explain the annual glacier volume formula used in this estimation.
Table 1: What is the source of the DEM data from January 3, 2000?

Results and Discussion
Figure 5: The legend should be revised. Is the estimated volume related to snow cover or to the glacier? The graph appears to be about elevation change, in my opinion.
Figure 7: Replace “Yearly” with “Annual.”

Please discuss whether the changes in glaciers have intensified since 2000, 2010, or another period.

Conclusions
The text could be removed because the numerical data in line 502 and 504 are not supported by the methodology.

Author Response

Comments 1: Abstract
Please include information about the methodology.

Response 1: The suggestion was accepted. The methodology was included in the abstract.

 

Comments 2: Line 28: Snow cover area or glacier area?

Response 2: The suggestion is accepted.

Line 28: “glacier area” was replaced with “”snow cover”

 

Comments 3: Introduction
Lines 66–77: This paragraph could be removed.
Response 3: The suggestion is accepted.

Lines 66 – 77 were removed.

 

Comments 4: Line 84: The "; 2004" should be removed.

Response 4: The suggestion is accepted.

Line 84: 2004 was removed

 

Comments 5: Materials and Methods
The methods are sufficiently documented to allow for replication studies. The statistical methods are valid and correctly applied.

Regarding the dataset:
Line 237: What is the period of the year during which the images were obtained?

 

Response 5: In the period from 2006 to 2013, the Sentinel images were downloaded closely to ALOS PALSAR and LIDAR images date, the common around of July with exception of two images. Whilst the optical images from 1990 to 2000 were downloaded around of July, the driest period of year.

 

Line 229 – 230: The Landsat images were downloaded in two periods, Landsat 5 Thematic Mapper (TM) imagery from 1990 to 1999, and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) imagery from 2000 to 2013.

 

Line 282: The ALOS PALSAR images were downloaded from 2006 to 2010.

 

The ALOS PALSAR and Landsat images description: dates, glacier area estimation, glacier volume estimation and errors, are shred in the complementary information.

Dataset link:  https://doi.org/10.21223/6UWFPN (Line 509)

 

Comments 6: Line 254: The “/estimation” should be removed.

Response 6: The suggestion is accepted:

Line 254: “/estimation” was removed.

 

Comments 7: Line 283: Please clarify what “expert-defined shapefiles” refers to.

Response 7: It was clarified, the shapefiles defined by experts refers to work titled “Inventory of Glaciers and Glacial Lagoons” prepared by the Glaciology and Water Resources Unit (UGRH) of the National Water Authority (ANA) of Peru in the framework of COP20. They reported the first inventory of glaciers in Peru in the Urubamba and Vilcanota cordillera using topographic maps, maps of the National Charter and aerial photographs from 1970.

 

The next cite was added [43]:

“Autoridad Nacional del Agua; Dirección de Conservación y Planeamiento de Recursos Hídricos; Unidad de Glaciología y Recursos Hídricos Inventario nacional de glaciares y lagunas. Autoridad Nacional del Agua 2014.”.

 

Comments 8: Line 309: Is the topic volume change or elevation change?
Response 8: Thanks by the comment. The topic is “Volume changes in glaciers”.

 

The material and Methods section was improved.

 

Equations to compute the glacier volume and the volume changes were added (section 2.3.1.2).

The Figure 6 was updated.

In the Result section, the metric values were updated..

 

Comments 9: Line 322: What GPS equipment was used in this step?

Response 9: The GPS was a Garmin, with an error - provided by manufactured - of 12.5 m. 

 

Comments 10: For Figure 3: Please review the visual quality of this figure.
Please explain the annual glacier volume formula used in this estimation.

Response 10: The suggestion is accepted. The images quality have been improved.

The Figure 3 was updated..

 

Comments 11: Table 1: What is the source of the DEM data from January 3, 2000?

 

Response 11: Thanks by the comment. The DEM image from January 3, 2000 is from ASTER, a composite ranging from 2000 to 2010. The next corrections were performed:

 

The Table2 and Figure 6 were updated.

The date and statistics results were updated in the manuscript.

 

Comments 12: Results and Discussion
Figure 5: The legend should be revised. Is the estimated volume related to snow cover or to the glacier? The graph appears to be about elevation change, in my opinion.

 

Response 12: The suggestion is accepted, the legend was corrected:

The legend was updated with:  “A) Volume of the Quisoquipina and B) Suyuparina glaciers” instead of “A) Volume of the Quisoquipina and B) Suyuparina glaciers”.

 

Comments 13: Figure 7: Replace “Yearly” with “Annual.”

 

Response 13: The suggestion is accepted,

 “Yearly” was replaced with “Annual”

 

Comments 14: Please discuss whether the changes in glaciers have intensified since 2000, 2010, or another period.

 

Response 14: In the results section, an analysis of glacier area change has been included for the periods of 1990-1999 and 2000-2013.

 

Comments 15: Conclusions
The text could be removed because the numerical data in line 502 and 504 are not supported by the methodology.

Response 15: The suggestion is accepted. The text was removed.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Glacier area and length changes need to be precisely assessed to be valuable as an indicator of climate change. Remote sensing approaches allow for regular monitoring of the properties of alpine glaciers such as ice extent, terminus position, volume and surface elevation, from which glacier mass balance can be inferred, and deriving glacier outlines from satellite data has become increasingly popular in the past decade. The MS explored the estimation of glacier outline and volume changes in the Vilcanota range snow-capped mountains, Peru, using multi-source remote sensing data, such as optical and LiDAR. The topic is interesting, and the MS is well-written, but I think that the following concerns should be addressed before it goes to any future.

(1) The study should be driven by scientific or technical problems. The section ABSTRACT should be rewritten, it should be divided into four parts: purpose, methods, results and conclusions.

(2) The motivation and innovation should be indicated in the opening sentence of section ABSTRACT and in the last paragraph of section INTRODUCTION.

(3) For section INTRODUCTION, lines 81-82 on page 2, “However, several methods have been developed to map glacier outlines based on multispectral images automatically.” I want to know what are the methods? The principle, advantages and disadvantages of each remote sensing methods should be briefly described.

(4) For section 2.2.1. LANDSAT IMAGE PROCESSING, the USGS and NASA have unified all the Landsat data processing into surface reflectance, which can be downloaded through cloud platforms, such as GEE, why do this study carried out radiometric calibration and atmospheric correction based on FLAASH?

(5) The section 2. MATERIALS and METHODS should be reorganized, it should be divided into three parts: study area, data sources and methods.

(6) How to estimate glaciers volume or glaciers volume changes? Which model used? The principle and equations should be described. In addition, how to verify that the results are accurate?

 

(8) There are some grammar and spelling errors, the language should be improved before publication.

Comments on the Quality of English Language

There are some grammar and spelling errors, the language should be improved before publication.

Author Response

Comments 1: (1) The study should be driven by scientific or technical problems. The section ABSTRACT should be rewritten, it should be divided into four parts: purpose, methods, results and conclusions.

Response 1: I accept the suggestion. The Abstract has been rewritten.

Comments 2: (2) The motivation and innovation should be indicated in the opening sentence of section ABSTRACT and in the last paragraph of section INTRODUCTION.

Response 2: The suggestion is accepted. The last paragraph of Introduction section has been rewritten.

Comments 3: (3) For section INTRODUCTION, lines 81-82 on page 2, “However, several methods have been developed to map glacier outlines based on multispectral images automatically.” I want to know what are the methods? The principle, advantages and disadvantages of each remote sensing methods should be briefly described.

Response 3: Thanks by the comment. In the lines 81 – 82 we cite to Veettil et al., 2017, a review paper where is describe various remote sensing methods for monitoring glacier variables like area and mass balance. The phrase in the lines 81 – 82 has been updated to include a brief description of the remote sensing methods, advantages, and disadvantages.

Veettil, B.K.; Kamp, U. Remote Sensing of Glaciers in the Tropical Andes: A Review. International Journal of Remote Sensing 2017, 38, 7101–7137, doi:10.1080/01431161.2017.1371868.

Comments 4: (4) For section 2.2.1. LANDSAT IMAGE PROCESSING, the USGS and NASA have unified all the Landsat data processing into surface reflectance, which can be downloaded through cloud platforms, such as GEE, why do this study carried out radiometric calibration and atmospheric correction based on FLAASH?

Response 4: Thank you for the comment. It is true that GEE can perform this procedure automatically. Our team consists of various expertises, including young researchers, professors, and specialists in fieldwork in snow-capped regions. We chose to process Sentinel-2 images using our traditional expertise.

Comments 5: (5) The section 2. MATERIALS and METHODS should be reorganized, it should be divided into three parts: study area, data sources and methods.

Response 5: The suggestion was accepted. The Material and Methods section was reorganized according to the proposed sections.

Comments 6: (6) How to estimate glaciers volume or glaciers volume changes? Which model used? The principle and equations should be described. In addition, how to verify that the results are accurate?

Response 6: Thank you for the comment. The material and methods section was updated. The models and equations to compute glacier volume and their respective changes were added.

Since we do not have measured data of glacier area and volume, we calculated uncertainties or errors based on remote sensing methods.

Comments 7: (8) There are some grammar and spelling errors, the language should be improved before publication.

Response 7: Thank you for the comment. We have made efforts to improve the grammar.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

You mention that increased precipitation could contribute to glacier loss. However, this statement lacks clarity, as precipitation, particularly in the form of snow, is typically associated with a positive mass balance for glaciers. I recommend clarifying the mechanism you are referring to. One possible explanation might be similar to the findings of Persoiu et al. (2021), where warm, heavy summer rains contributed to significant glacier melting. You may find their study relevant to your case: Persoiu et al., Record summer rains in 2019 led to massive loss of surface and cave ice in SE Europe, The Cryosphere, 2021.

Author Response

Comments 1:

You mention that increased precipitation could contribute to glacier loss. However, this statement lacks clarity, as precipitation, particularly in the form of snow, is typically associated with a positive mass balance for glaciers. I recommend clarifying the mechanism you are referring to. One possible explanation might be similar to the findings of Persoiu et al. (2021), where warm, heavy summer rains contributed to significant glacier melting. You may find their study relevant to your case: Persoiu et al., Record summer rains in 2019 led to massive loss of surface and cave ice in SE Europe, The Cryosphere, 2021.

Response 1:

 

Thank you for the comment.

 

We have added to our discussion of results associated with precipitation versus glacier area change the findings presented by Persoui et al., 2021 as a possible explanation for why precipitation has a greater impact than temperature on the reduction of glacier area in snow-capped mountains Quisoquipina and Suyuparina.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

 

Title: Estimation of glacier outline and volume changes in the Vilcanota range snow-capped mountains, Peru, using temporal series of Landsat and a combination of satellite radar and aerial LIDAR images

Manuscript Number: remotesensing-3196820

 

This paper by Montoya-Jara et al. presents an important topic aimed at estimating glacier outline and volume changes in the Vilcanota range of Peru, using a combination of remote sensing data from Landsat, ALOS PALSAR, and LIDAR data. The general structure of the manuscript is suitable, before this manuscript can be published, a major revision is still needed to improve the quality of the manuscript. Please, see my detailed comments below.

 

Comments

 

 

-Materials section needs to be enhanced. One table can be added to introduce the detail information of the used data sets.

 

-Error estimation missed in the methodology section. This research used the Landsat data, ALOS PALSAR, and LIDAR data, but further details regarding data preprocessing, error analysis about the area and volume (e.g., snow cover, the quality of the imagery), and data processing methods should be further enhanced. It is recommended that the authors provide more information on data quality and error estimation to enhance the credibility of the results.

-Check and revised the errors in the references.

 

-Here, the Landsat date chose during 1990-2013, ALOS PALSAR images for 2006-2010. Ten reference glaciological stakes were installed between 2014 and 2016 by [35] were used for validation. The study period appears to be inconsistent, and the endpoint of 2013 is outdated for current standards.

 

 

-Enhanced the quality of the Figures, e.g., Figure 7, Figure 5.

 

- The conclusions should clearly and accurately reflect the main findings of this research, and provide specific recommendations and directions for future research. Thus, the conclusions should be greatly enhanced.

 

 

Comments on the Quality of English Language

No comments

 

Author Response

Comments 1: Materials section needs to be enhanced. One table can be added to introduce the detail information of the used data sets.

Response 1: Thanks by the comment.

Materials and Methods section was updated. We introduce a detail information of data sets used.

 

Supplementary information with areas, volumes, estimated errors and dates of Landsat, ALOS PALSAR and LIDAR images are shared in the next dataset.

https://doi.org/10.21223/6UWFPN.

 

Comments 2: Error estimation missed in the methodology section. This research used the Landsat data, ALOS PALSAR, and LIDAR data, but further details regarding data preprocessing, error analysis about the area and volume (e.g., snow cover, the quality of the imagery), and data processing methods should be further enhanced. It is recommended that the authors provide more information on data quality and error estimation to enhance the credibility of the results.

 

Response 2: Thanks by the comment. The Material and Methods section was improved. The equations to compute area, volume and misclassification area were introduced.

 

Comments 3: Check and revised the errors in the references.

 

Response 3: Thank by the comment, the references were checked.

 

Comments 4: Here, the Landsat date chose during 1990-2013, ALOS PALSAR images for 2006-2010. Ten reference glaciological stakes were installed between 2014 and 2016 by [35] were used for validation. The study period appears to be inconsistent, and the endpoint of 2013 is outdated for current standards.

 

Response 4: Thank by the comment. It is true that our study with remote data extends only until 2013, due to the restricted availability of DEM data in our study area, with the last being a LIDAR dataset from 2013 funded by Universidad Nacional San Antonio de Abad del Cusco (UNSAAC) project. We have removed the analysis concerning the validation of changes in DEMs with the stakes, as they do not cover the same period.

 

Comments 5: Enhanced the quality of the Figures, e.g., Figure 7, Figure 5.

 

Response 5: The suggestion is accepted. The quality of Figures 5 and 7 were improved.

 

Comments 6: The conclusions should clearly and accurately reflect the main findings of this research, and provide specific recommendations and directions for future research. Thus, the conclusions should

be greatly enhanced.

Response 6: Thanks by the comment. The conclusions were clarified.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

I believe the authors have made significant improvements to the manuscript, particularly in the Introduction, and I support its publication.

However, I recommend addressing the following minor issues before publication:

• I noticed the repeated appearance of the message: "Error! Reference source not found." Please correct this.

• In Figures 4-6, the x-axis should display actual years (e.g., 1990-1999) rather than numbering from 1 to 10.

• There is inconsistency in the references to "snow volume changes" and "ice volume changes." Please ensure consistency throughout.

• Lines 777-779 should be removed, as they are unrelated to the study and do not add value.

 

Author Response

Comments 1: I noticed the repeated appearance of the message: "Error! Reference source not found." Please correct this.
Response 1: The suggestion is accepted. The hyperlink of figures and tables were corrected. The references and cites were reviewed too. 

Comments 2: In Figures 4-6, the x-axis should display actual years (e.g., 1990-1999) rather than numbering from 1 to 10.
Response 2: The suggestion is accepted. The x-axis of figures 4, 5 and 6 displays the actual years.

Comments 3: There is inconsistency in the references to "snow volume changes" and "ice volume changes." Please ensure consistency throughout.
Response 3: The suggestion is accepted. The document was reviewed and corrected to maintain consistent.

Comments 4: Lines 777-779 should be removed, as they are unrelated to the study and do not add value.
Response 4: The suggestion is accepted. The lines were removed.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

Much improved, this version may be accepted once the following points have been addressed.

Some points can be further enhanced as follows:

-L248: Please check the sentence and ensure that the author's name is included.

-L338: Where is the reference? Additionally, in lines 414, 467, 514, 604, etc., please check and revise the references as needed.

-Please provide the precise figures for the error estimation within the text of the manuscript.

-Adjust and improve the style of Figure 3, which needs to be beautified. Ensure consistency in terminology (e.g., "rainfall" or "precipitation") and revise the error in the word "Glacier's area" in the Figure.

Comments on the Quality of English Language

No

Author Response

Comments 1: L248: Please check the sentence and ensure that the author's name is included
Response 1: The suggestion is accepted. The author’s name was included.

Comments 2: L338: Where is the reference? Additionally, in lines 414, 467, 514, 604, etc., please check and revise the references as needed.
Response 2: The suggestion is accepted. The references were corrected.

Comments 3: Please provide the precise figures for the error estimation within the text of the manuscript.
Response 3: The suggestion is accepted. The errors of figures were described.

Comments 4: Adjust and improve the style of Figure 3, which needs to be beautified. Ensure consistency in terminology (e.g., "rainfall" or "precipitation") and revise the error in the word "Glacier's area" in the Figure.
Response 4: The suggestion is accepted. The figure 3 was improved. The inconsistency in terminology was corrected. The orthography error was corrected.

Author Response File: Author Response.docx