Dear authors,

thank you for your revision and considering the reviewer´s comments. The manuscript reads very well and is fine as such, so I’m happy to accept you MS for publication in TC. I would just like to ask: why didn’t you include the analysis you discuss in this comment, if it is easy to calculate? The MS and it’s impact would benefit from it!

„AC : Such a parameter is very simple to compute, which is one of its strength, therefore we would only need the reconstructed tomographic volumes, or directly the volume of labelled pores. It would be interesting to compare the CI evolution for all the sites previously studied by X-ray tomography. This would allow the CI ability to estimate the COD to be confirmed.“

Other remarks

Abstract l10: older gas at which site? Be explicit.

p3 l31 rewrite: These authors studied three polar sites with a microstructure computed from tomography allowing very large volumes of firn to be imaged.

p4 l19&28 you use different abbreviations for weyr-1. Please use m w.e. yr-1 or define once and use only m yr-1 (would be most readable). Or cm yr-1.

p9 unclear: processing ones. Clarify.

p16 l9 whose -> who‘s

Very, very minor copy-editing remarks:

Eq (1), (2): add dot
p14 l12 remove space at end.
Tab 2: remove blank after samples (2x)
p10 l21 remove space after 6)
p14 l4 remove blank after %
p14 l12 dto. 6a)
p23 l6 space missing before The
p25 l22 remove blank after 7)

Data availability: do the data have a doi or permanent link?

Please consider these recommendations before uploading the final version.

Thank you for submitting your work to TC!

Regards,
Olaf