Review of the paper « Characterization of in situ cosmogenic 14CO production, retention and loss in firn and shallow ice at Summit, Greenland

The crucial point in this paper is to put additional constrains on the muon induced 14C production rate in ice as function of depth. A recent study (Dyonisius 2023) indicated that this production channel, which is most relevant in depth below the LIZ, seems to be less pronounced than previously predicted in the literature (by a factor of 6 and 4 for negative muon capture and fast muon interaction respectively). These observations were confirmed in the current study. This may have important implication for ice core research, but potentially also for other research areas where cosmogenic isotope production (not only 14C) in the underground becomes relevant. In the conclusions, this aspect could be highlighted more. This holds also for hypothesis regarding the possible underlying reasons for the resulting disagreement, (such as variations in fast muon energy spectra with depth and cross-sectional considerations etc).

The paper is very well written and technically sound (with some minor issues as listed below). The 14C extraction and analytical methods, which follow well established procedures described in the literature are well documented. Data interpretation was done in the frame of existing production- (Balco 2008) and ice transport models (Buizert 2012). This excellent contribution is basically ready to be published as it is.

Some uncertainties persist in the parametrization of the partitioning of 14CO in the ice reservoirs. The introduction of a two-domain approach, involving rapid and slower release rates/reservoirs, may seem somewhat arbitrary. While this approach might align well with the data (as expected with the inclusion of extra model parameters), there remains a need for some additional physical justification in the text, although some hypotheses are mentioned in L 526 ff. The small resulting retention of ~0.5% makes me wonder how “worst” the model fit would be without consideration of R1?

The leakage coefficient L0 was fixed at 1 yr-1 (corresponding to a half-loss time of 0.7 years). Where is this value coming from?

What exactly is meant with “indicating slow leakage of 14CO from the ice grain (L 421 p 13) in relation to the concentration decrease with depth? Please clarify.

Minor issues

P14 L455ff: there is something wrong with the grid search interval for Fn. I guess the step size should be 0.01 instead of 0.05

Page 16, L515ff: Also, here is something wrong. It seems that the diffusion time was calculated with a grain radius of 3mm. Either this is a typo or the resulting diffusion time for 0.3mm should be ~4.5 h instead of 18 days (what emphasizes the assumption of nearly complete 14C loss on timescales of 1 year even more).