Dear authors,

Please see the attached supplement for comment on your paper. I have some concerns over the velocity analysis of the GPR data, hence my review focuses exclusively on these aspects as I don't think it's possible to comment on the match to climate models until these issues are resolved.

Best regards,

Adam Booth

Review of manuscript by Akash M. Patil and colleagues entitled “Investigating firn structure and density in the accumulation area of Aletsch Glacier using Ground Penetrating Radar” (https://doi.org/10.5194/egusphere-2025-615).

Summary

Akash Patil and colleagues investigated the snow and firn structure of Grosser Aletschergletscher, Switzerland, based on snow pits, firn cores, Ground Penetrating Radar (GPR), and Common Mid-Point (CMP) measurements from field campaigns carried out between February and May 2024. They used these field observations and firn compaction models to reconstruct the accumulation history over the past 12 years and validated (or compared) their results against snow water equivalents from a long-term glaciological point mass-balance program run by Glacier Monitoring Switzerland.

Evaluation

Akash Patil and colleagues have conducted extensive fieldwork and investigated their observations in combination with process understanding, firn modelling, and existing measurements. This combination of methods provides new insights into the processes of snow/firn accumulation and densification in the accumulation zone of the largest Alpine glacier, which is changing from a dry zone to a percolation zone under current climatic conditions. The manuscript presents a valuable and very interesting study that fits well into the scope of The Cryosphere. Still, major revisions are required to improve the structure and readability of its text and figures, and to elaborate and discuss its key findings better. As such, it would be nice to add a direct comparison of their results from 2024 with an earlier survey from 2021 by Bannwart et al. (2024). My feedback is summarized as general and specific remarks outlined in the attached PDF file.