the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Nov 2025
Slowdown of glacier velocity emerging in the Zanskar Himalayas
Abstract. Trends in glacier surface velocity provide insight into the response of glaciers to climate change as well as local drivers of ice dynamics. The Zanskar Himalayas are heavily glacierised, but retreating glaciers pose a threat to local and regional water security. Remote sensing provides a tool for observing surface velocity over multiple glaciers in a remote and challenging area for field work, providing key observations for tracking changes in this important region. This study provides a comprehensive analysis of long-term (1992–2023) interannual glacier surface velocity and elevation change for 12 selected glaciers in the Zanskar Basin of the Ladakh Himalayas. We show that glaciers have overall experienced deceleration at an average rate of -2.43 m year-1 decade-1 in this region. This reduction in ice velocity corresponds with a mean glacier surface elevation decrease of ~ -0.21 m yr-1 between 2000–2005, increasing to ~ -0.57 m yr-1 by 2015–2020. While glacier mass loss, particularly through thinning, and associated reduction in driving stress was identified as the primary driver of velocity deceleration, glacier-specific characteristics, such as geometry, topography, debris cover and terminus type, also influenced glacier response. For example, lake-terminating glaciers exhibited local increases in ice velocity near their termini. Overall, our results confirm a reduction in glacier health in this region, as glaciers thin and slow down as a consequence of climate warming.
Competing interests: One of the author is a member of the editorial board of The Cryosphere. All other authors declare that they have no conflict of interest.
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.- Preprint
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Status: open (until 07 Jan 2026)
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CC1: 'Comment on egusphere-2025-5260', Daya Songh, 10 Dec 2025
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EC1: 'Editor statement: Unprofessional comment, lacking an affiliation', Etienne Berthier, 16 Dec 2025
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As editor handling this manuscript, I would like to express my concerns about the community comment posted by Daya Songh.
First, both I and the co-editors-in-chief of The Cryosphere (TC) felt that the tone of the comment was unprofessional and goes beyond the level of negativity that would be deemed appropriate in peer review.
Second, we would like to remind all colleagues that a pre-print considered for publication in TC “undergo(es) an interactive public discussion, during which the referees' comments (anonymous or attributed), additional community comments by other members of the scientific community (attributed), and the authors' replies are posted.” See https://publications.copernicus.org/services/public_peer_review.html
Hence, we would please request that Daya Songh confirms their affiliation as we could not verify their identity, after which the authors can respond to the scientifically relevant points raised in this community comment.
Etienne Berthier
Citation: https://doi.org/10.5194/egusphere-2025-5260-EC1
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EC1: 'Editor statement: Unprofessional comment, lacking an affiliation', Etienne Berthier, 16 Dec 2025
reply
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RC1: 'Comment on egusphere-2025-5260', Anonymous Referee #1, 27 Dec 2025
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Summary
Ghosh et al. (2025) present a comprehensive analysis of long-term glacier surface velocity and elevation changes in the Zanskar Basin, Ladakh Himalaya. Utilizing satellite remote sensing data, primarily from Landsat imagery processed via COSI-Corr for velocity estimation and reanalyzed elevation data from Hugonnet et al. (2021), the study examines 12 selected glaciers to characterize trends in flow deceleration and thinning. The main findings indicate an overall velocity slowdown of -2.4 m yr⁻¹ decade⁻¹, with thinning accelerating from -0.22 m yr⁻¹ (2000–2005) to -0.57 m yr⁻¹ (2015–2020). The authors attribute these changes to climate-driven mass loss, which reduces gravitational driving stress and is modulated by glacier geometry, debris cover, and terminus type (e.g., lake-terminating glaciers exhibit localised accelerations). However, weaknesses were observed in inconsistent terminology, insufficient methodological details, and potential biases in ERA5 climatic data. The use of median rather than mean values for velocity and elevation changes may hinder comparisons with prior studies that use mean velocity and elevation changes. The discussion could be enhanced by incorporating regional contrasts, such as the accelerating surrounding Karakoram glaciers (Heid and Kääb, 2012), to better contextualise the slowdown of Zanskar’s glaciers. Please see my following suggestions. I hope this will help improve the text.
Suggestions:
L9: Several sentences include the term 'Glacier' twice or three times (L9, L16-19, L20, L23, L24, L40-41). For example, in this study, we have selected 12 glaciers as test glaciers to study the evolution of inter-annual glacier surface velocity and glacier surface elevation change (L110-111). This sentence contains the word 'glacier' four times.
L11: Remote Sensing provides a tool; what type of tool is it? You may mention the image correlation here.
L15: After point 1, a digit is sufficient, for example, -2.4 instead of -2.43 throughout the manuscript. Also, what does an uncertainty ± represent?
L15-16: Somewhere written year-1 and somewhere written yr-1. Please maintain consistency throughout the entire manuscript.
L16: Between 2000 and 2005, instead of 2000-2005. Please maintain consistency throughout the entire manuscript.
L28-29: Please use the word 'glacierized' instead of 'glaciated', as the latter word implies a former glacier area that has deglaciated now. Please check throughout the manuscript.
Please check this glossary- https://wgms.ch/downloads/Cogley_etal_2011.pdf
L35: You may replace 'impacted' with 'reduced'.
L38: Weertman (1957) is an outdated reference; you may replace it with more recent references.
L44: First mention the complete form of DGNSS and then write its acronym.
L45: Surface velocity can be estimated; a reference is needed.
L48: Two times mention 'particular' and 'particularly' in a single sentence.
L49-50: Satellite-based remote sensing methods. Please describe the specific techniques here.
L58: Please describe what other local conditions are.
L73: The three-year mass balance of Rulung Glacier and the four-year mass balance of Stok Glacier do not present a declining trend. To understand the trend in mass balance, we require a long series of in situ measurements. You may mention here the negative mass balance only.
L75-76: Correct the reference of Soheb et al. (2020) and Mehta et al. (2021).
L93: Omit Western Himalaya.
L97: Test……………………..reframe this sentence.
L110: Why were selected 12 glaciers? Please give the justification. What is the range of area and elevation of these glaciers? Please add 2-3 sentences on this.
L139: Green (B2 band), why was the Green band? Please explain here.
L158: There is some confusion. Did you co-register the Landsat images, as these images are already orthorectified? If not performed, please omit this.
L162: What is the "salt-and-pepper" effect?
L166: 4*4 pixels, but Landsat 5 does not contain a panchromatic band. Possibly you used 2*2.
L176-178: I feel five iterations are best, whereas two iterations may give some noise. Please carefully check and rewrite.
L204: It may also arise due to a horizontal shift in two images; you may mention this here.
L213: Please provide more details on pairwise uncertainty in the supplementary material.
L221-223: Please reframe this sentence, and replace glacier mass balance with elevation changes.
L229: Equation 5, how are these parameters calculated in this equation? What is the uncertainty in these estimates? Please describe in the text. I also could not find how this equation helps to interpret the result of glacier surface flow velocity in the manuscript.
L242: ERA5 Land reanalysis climate data: Many studies have reported biases in the ERA5 land reanalysis dataset in mountainous areas. Our own study found a 5- to 8-degree temperature difference between the automatic weather station and the ERA5 Land dataset in different seasons, without bias correction, in the Central Himalaya. Such climatic trend analysis without bias corrections is not appropriate and provides unrealistic trends. I would suggest conducting bias correction in ERA5 data using nearby IMD sites or the IMD grid dataset.
L247: Section 4.1, Glacier velocity trend and surface elevation change: Both sections must be presented separately. Also, section 4.3 "elevation-wise glacier velocity trend is actually section 4.2 (possibly typo mistake), which can be merged with section 4.1 (glacier velocity trends) following the removal of surface elevation change.
L257-258: In the result and discussion section for surface flow velocity and elevation changes, the median flow velocity term and median elevation change term are frequently used. However, most of the previous studies use mean or average surface flow velocity or mean elevation change values. It is not straightforward to compare the median surface flow velocity with the previously published mean surface flow velocity.
L260: Use 24.5 ±5.7 instead of 24.50±5.73 throughout the manuscript.
L263: T-statistic test, please describe this statistical test in detail in the methodology section for the interest of readers.
L281: Between 2001 and 2010, instead of between 2001-2010. Please carefully review the entire manuscript for any similar text.
L283: From 1992 to 2000 instead of from 1992-2000.
L296-300: This is related to methodology, not related to the result section. Please shift to the relevant section and write only the results here.
L326: omit theory.
L326: median glacier surface elevation change. Primarily, studies use mean glacier elevation changes. Please see my previous comment.
L327: What are bottom-heavy glaciers? First, define these terms.
L355; Figure 8: In sub-panel A, also show Drun Drung glacier in the subset, as shown in sub-figure b.
L380; Figure 9: In this figure, you mentioned median velocity and mean elevation, whereas in text L326, you mentioned median glacier surface elevation change. Please correct it throughout the manuscript.
L386; 4.4 Climatic trends: Please see my previous comment on the ERA5 Land dataset without Bias correction, such trends are not appropriate. Additionally, please describe how the calculated uncertainty of the ERA5 land dataset is ±0.01 °C in the methodology.
L396: The discussion section can also be improved. Please see the following papers, which can help enhance the discussion section, particularly regarding the increase in lake-terminating glacier flow velocity and its comparison with the Karakoram region.
Hyde, A., Carr, J.R., Dunning, S. and de Vries, M.V.W., 2025. Quantifying heterogeneous glacier dynamics in Lunana, Bhutan, using spatiotemporally high-resolution satellite imagery. Journal of Glaciology, pp.1-33.
Heid T, Kääb AJ. Repeat optical satellite images reveal widespread and long term decrease in land-terminating glacier speeds. The Cryosphere. 2012 Apr 10;6(2):467-78.
Wu, K., Liu, S., Xu, J., Zhu, Y., Liu, Q., Jiang, Z., and Wei, J., 2021. Spatiotemporal variability of surface velocities of monsoon temperate glaciers in the Kangri Karpo Mountains, southeastern Tibetan Plateau. Journal of Glaciology, 67(261), pp.186-191.
Citation: https://doi.org/10.5194/egusphere-2025-5260-RC1
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General comments
The manuscript does not demonstrate sufficient novelty, methodological rigor, or scientific contribution to merit publication in its current form. Most findings reiterate well-established results from previous studies in the Himalaya, and the manuscript lacks a clearly articulated research gap, robust methodology, or quantitative analyses to substantiate its interpretations. Significant conceptual, methodological, and presentation issues further weaken the study.
Specific comments
Lack of Novelty and Insufficient Contribution
The manuscript largely repeats previously published results on glacier velocity, surface elevation change, and heterogeneous glacier response in the western Himalaya (e.g., Dehecq et al., 2019; Bhambri et al., 2023; Garg et al., 2025). The conclusions on glacier thinning, deceleration, debris-cover influence, and behaviour of lake-terminating glaciers are all well documented in existing literature and are not presented with new insights, methodological improvements, or conceptual advances.
The study area (Zanskar Basin) has already been extensively analysed (Rai et al., 2012; Pandey et al., 2012; Shukla & Qadir, 2016; Rana et al., 2023; Jasrotia et al., 2023; Mandal et al., 2024). The manuscript does not convincingly demonstrate how its results expand current understanding or address an unmet research need. The authors claim earlier works cover limited time periods, but Bhushan et al. (2018) computed regional mass budgets for 1999–2014, and Rana et al. (2023) produced velocity time series from 1999–2021. It is unclear what genuinely new temporal dataset or insight the present manuscript adds.
Issues in the Introduction
The Introduction incorrectly implies that earlier studies provide only short-term or two-epoch comparisons. However, prior works already assess long-term glacier changes. The manuscript must clarify what additional value its stated 1992–2023 velocity record brings, especially given the absence of field validation and without clear methodological innovation.
Study Area Description – Conceptual and Factual Errors
The manuscript lacks critical methodological information necessary to evaluate scientific reliability:
Overall, the methodological gaps are substantial and undermine confidence in the results.
Conclusion
The manuscript suffers from fundamental issues in novelty, methodology, interpretation, and presentation. It reiterates previously established results without providing new scientific insight, lacks essential methodological transparency, and misinterprets or oversimplifies glacier dynamics.
Given the magnitude of conceptual, analytical, and structural shortcomings, the manuscript is not suitable for publication.