Dear Mr. Alexander et al.,

This manuscript received two positive reviews, highlighting the excellent quality and scientific significance of your results. Both reviewers suggested a number of improvements, with the more substantial points being (i) the need for a clear statement about the scope of your work in the abstract and introduction, (ii) the lack of a technical description of the instrument (electronics, safe operation limits, etc.), and (iii) suggestions for a more condensed manuscript, e.g. through the use of supplementary information. The comments of the reviewers and their suggestions for improvement have been comprehensively addressed in your replies, and I would like to invite you to submit a revised manuscript that reflect these comments and replies.

Best regards,
Jan De Rydt, editor

Dear Andreas et al.,

Based on a further excellent review by Samuel Doyle, I would like to encourage you to make a few additional minor corrections before the manuscript can be published. Please provide a point-by-point response to his suggestions (see a copy below) and relate these to changes in the manuscript. Please also consider including a statement about data availability at the end in order to comply with TC data policy (see https://www.the-cryosphere.net/about/data_policy.html for further details)

Many thanks,
Jan De Rydt - Editor

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Referee #2: Samuel Doyle, sdd08@aber.ac.uk

My previous comments have largely been addressed, however, further work is required to justify the inclusion of the table of wireless sub-surface sensor systems (now Table S2; see below). The same applies to Table 1. The manuscript needs a through check for grammar and typographical mistakes. Please see a list of comments below.

Title - Consider whether the title could be shortened and made clearer to something like “Multi-sensor drifters for glacial hydrology flow path measurements”. I’m not sure many readers will immediately understand precisely what is meant by ‘Multi-modal’. Consider what you mean by ‘repeatable’ in the title, and elsewhere.

P1L6 - you need to make clear that the experiments were repeated multiple times in the same channel section and then the results compared.

P1L16 - ‘… repeated measurements …’

Table 1 - Please consider whether this table is essential to the reader. I’m not sure that it is necessary here and It could be moved to the supplement. The reader does not currently have access to an example dataset so does not need the metadata. Even if an example dataset were provided the metadata does not need to be provided in the manuscript. Column names and abbreviations should be explained.

P2L17 - the reference here to Table S2 which lists subsurface sensors is a bit misleading as it is immediately followed by a list of other techniques without explaining the difference. Table S2 also focusses on wireless sub-surface glacial sensors neglecting entirely (without a reason being given) very similar wired sensor systems, which are used more commonly. Neither appear to be directly relevant to this study. More work is required to organise this section for the readers benefit.

P7L15 - what kind of debris? I’m guessing you mean ice?

P7L16 - Suggest ‘emerging’ or ‘re-emerging’.

P11L5 - the equations for the recovery rate etc are methods and should be moved to the methods section. It’s not necessary to show your workings. These results could potentially be presented in a table.

P11L30 - here a list is started using a colon but then the second part of the list follows as a new sentence. Suggest avoid new sentence.

P12L8 - Table S3 not A3.

P13L3 - increasing atmospheric pressure with (known) decrease in altitude could be calculated to isolate its contribution here.

P13L9 - ensure consistency with writing out confidence interval in full and abbreviating it

P14L1 - the sentence beginning (on this page) ‘… all sensor modalities’ needs revising.

P14L10 - its the hydrodynamics of the drifter and balloon than lead the drifter to face away, combined with the current.

P19L11 - is the use of the double greater than sign >> intended to indicate P approximately greater than 0.05?

P19L14 - ‘could’ instead of ‘can’

P20L29 - I’m not sure this sentence says what you intend it to. Do you mean that additional fieldwork should compare drifter data to other measurements (e.g. tracer velocity)? Please clarify.

P21L8 - time-averaged?

P21L10 - typo

P21L11 - sentence beginning ‘After low pass filtering …’ needs re-ordering.

Ensure Table S2 and Figure S1 are referenced in the manuscript. If not, are they necessary?

Dear Andreas and co-authors,

Thank you for providing a revised manuscript and for your comprehensive treatment of the reviewer's suggestions. I have some minor comments that you might want to consider as part of your final manuscript submission.

1. Recovery and utility rates are now defined in the Methods section, but this definition would benefit from a short motivation. At the moment these are just 3 floating equations without context.

2. Please expand on why the data is not publicly available in the 'Data Availability' section. Please note the guidelines in the Copernicus data policy booklet in this context: "If the data are not publicly accessible, a detailed explanation of why this is the case is required (e.g. applicable laws, university and research institution policies, funder terms, privacy, intellectual property and licensing agreements, and the ethical context of the research);"

Many thanks again for considering The Cryosphere for your manuscript submission, and I look forward to receiving the final version.

Best regards,
Jan De Rydt - editor

Dear Andreas et al.

Many thanks for addressing my comments and for providing a revised manuscript. I'm happy to recommend your manuscript for publication in its present form. Thank you for your efforts throughout, and for choosing The Cryosphere to publish your work.

Best regards,
Jan De Rydt - editor