Dear Sanne and co-authors,

Thank you for your thorough and thoughtful responses to the reviewers and your accompanying descriptions of manuscript revisions. Please submit your revised manuscript as described in your responses to the reviewers.

All the best,
Kaitlin

Dear Dr. Veldhuijsen and co-authors,

Thank you for your revised manuscript based on your thoughtful consideration of the two reviewers’ comments and one discussion comment. I think the motivation and methods are clearer, and the conclusions are stronger. The manuscript would be further improved by addressing the following comments:

General Comment:
1) The central message of the manuscript is still hard to determine in this revised version despite the new text providing more motivation and stronger conclusions from the presented results. Consider making the central message of the paper more explicit in the abstract and other relevant sections, and revising the title to reflect that central message/big takeaway from your results.

Technical/Line-specific Comments:
*line comments made with respect to line numbers on the track changes version of the manuscript

L11: no space needed between 89% (and every other percentage value reported in the manuscript)
L11-13: consider rearranging this sentence to avoid repeating ‘Using’ in two consecutive sentences: ‘We predict future PFAs (2015-2100) using the PFA emulator for…’
L13: consider using a description of the two emission scenarios you name here instead to allow the reader to quickly understand the context of those named scenarios. Something like: ‘Under our low and moderate emissions scenarios (SSP1-2.6 and SSP2-4.5)…’
L13: consider the same approach for the next sentence too (SSP5-8.5)
L14: you can remove ‘the’ from the added ‘six out of the seven…’
L15: like the previous sentence, you can remove ‘the’ from the added phrase here
L15-21: consider merging these two added sentences to improve the flow. Something like: ‘…conditions required for PFA formation, while those for HIRHAM are lower due to the model’s different relation between temperature, accumulation, and melt compared to RACMO.’
L47: I think there’s a missing word here: ‘Combining regional climate model (RCM) output/data with satellite data…’
L52-55: I appreciate the added text here to expand upon the description of the motivation here, but it might be further improved by outlining how ‘water storage capacity’ directly contributes to ‘ice-shelf disintegration events’ here faster. I think the easiest way to accomplish that is to put the information about the break-ups of the Wilkins ice shelf after the description of the mechanisms that the water impacts in Lines 56-59.
L56: I think ‘extensions’ should be singular here
L59-63: combine these references to ice shelf disintegration with the Wilkins ice shelf examples from Lines 53-55 here to improve flow
L64: a comma is needed after ‘Greenland’
L78-79: I think you’re missing a phrase at the end of this sentence here. Something like: ‘Therefore, we developed an XGBoost PFA emulator to generate projections of future PFA extent with limited data.’
L99: either add ‘just’ before ‘firn temperature’ again here, change the wording to highlight that the updated densification rate depends on firn temperature like before but also grain size and overburden pressure
L106-107: The wording in this added sentence is awkward. Consider rewording to something like “Since perennial firn aquifers (PFAs) are defined as saturated firn, IMAU-FDM cannot simulate them.”
L132: add ‘because it’ to the sentence here: ‘…and because it has been shown…’
L136: there is a missing connecting phrase or word here between ‘…and complex models,’ and ‘it incorporates…’
L163: I think you mean ‘ultimately’ or ‘also’ here instead of ‘therewith’
L190: you can remove ‘part of the’ here
L230: while I think that your description of the target variable (annual perennial LWC) is much clearer, I still think that the reviewers’ comments about reporting the RMSE and bias in mm and days being confusing, is still valid here. Can you include a phrase or sentence to quickly clarify that the mm units refer to the positive values and days refer to the negative values?
L238: two commas needed here: ‘When randomly, instead of strategically, …’
L240: remove ‘using’ here
L251: ‘onset of aquifers’  ‘onset of aquifer formation’
4.1 Section title: ‘PFA predictions…’
L266: ‘arises by’  ‘arises from’
4.2 Section title: ‘PFA predictions…’
L276: add ‘the’ after ‘yields’
L278: add ‘to be’ after ‘predicted’
L288: the original formulation of the sentence was correct: ‘For example, MAR-NorESM predicts the smallest…’
L308: ‘appear thus’  ‘thus appear’
L309: remove ‘a’
L313: ‘…, and henceforth will be referred to as…’
L349-350: the phrase ‘in addition to’ here makes the sentence awkward and hard to interpret. Reword to clarify the sentence.
L386: add ‘in’ after ‘resulting’

All the best,
Kaitlin

Dear Dr. Veldhuijsen and co-authors,

Thank you for your careful consideration of my previous comments. Your work to incorporate those suggestions has made the manuscript clearer and allows the reader to understand the importance of the work you present quickly. We will be pleased to publish your manuscript after two final grammatical corrections are made:

Line 338: remove the added 's' at the beginning of this sentence

Lines 339-344: In your revised manuscript (track-changes version), this sentence now includes two instances of 'e.g.', making it harder to understand if you're presenting two examples of sources of mismatch or if you're trying to say that the meltwater drainage process is an example of the limitations in the firn model. Please clarify this sentence in some way. One suggestion would be to remove the first 'e.g.' and reword to something like "...the underestimation of observationally detected aquifers due to widely spaced radar data, resolution and process limitations of the firn model, e.g., the drainage of meltwater into crevasses is not included in the model, and/or biases in the climatic forcing.'

All the best,
Kaitlin

Dear Dr. Veldhuijsen and co-authors,

Thank you for incorporating those final few comments. We are pleased to now publish your manuscript.

All the best,
Kaitlin