|Overall assessment of re-submission:|
The authors made a great, if not exceptional, effort to answer the reviewers' questions in great detail, which eventually resulted in a substantial reformulation of large parts of the manuscript incl. changes made to Figures. There is also a largely extended supplementary section. With that, the manuscript is very comprehensive, and I do not see what else needs to be added.
As the underlying data is key for the present paper, I should also mention that the presentation of the data and their availability is now very clearly described in the paper (this point was brought up by both reviewers that assessed the first version of the paper). Another point referred to the extrapolation of the glacier mass balance to higher elevations, which the authors carefully addressed with a dedicated separate section.
Overall, the paper is very comprehensive and it includes really all (or nearly all) aspects that are relevant when assessing glaciological mass balances and especially when implementing a (new) glaciological mass-balance programme. The Introduction offers many references to other studies; it is almost a complete overview on previous (glaciological) work for the particular study region, which is rather long but I think it will also be useful for other studies, too. The following description of the study site and its climate is written very carefully (the sub-section on climate is very comprehensive, but it will be useful for readers who are less familiar with the region). Presentation of results and their discussion are very clear, and there is extensive supplementary material referred to. Finally, I think the new Recommendations section will be very useful, too.
In addition, I also noticed the following points that could be addressed before final publication:
Line 12: you could first list the mass balance and then the length changes, as the main focus of the paper is on (glaciological) mass balance.
Line 15: It is not quite evident why there are two different observation periods for Yala Glacier (2000-2012 and 2011-2017), which also partly overlap (or maybe do not overlap, because the second period is actually 2011/12-2016/17 (?).
Line 18/19: “mass-balance rates”
Line 26: The new FoG database version will be 2021-05 and it should appear very soon on the WGMS doi landing page (you may check here: https://wgms.ch/data_databaseversions/)
Line 30: Good and interesting that you refer to the WMO(GCOS) headline indicators.
Line 32: You could also refer to Gärtner-Roer et al. 2019 (Worldwide assessment of national glacier monitoring and future perspectives, MRD, 39, A1-A11) about the national implementation of the glacier monitoring strategy.
Line 45: I would just write “glaciers” and not “clean glaciers”. If you want to use the term “clean” in this context, you would have to first explain what you exactly mean. On the other hand, it would open many other questions., e.g. what about glaciers that are partly debris-covered, and how would this affect the glaciological mass balance.
Line 110: There is a kind of break in here, maybe you could link this last paragraph more to the previous Introduction.
Line 113/114: Not fully clear; what do you mean with “other supporting data beyond the scope of the WGMS FoG database”?
Figure 1 is very useful for the broader context, incl. the overview map showing the location of other glaciers with mass-balance measurements.
You could add the date of the glacier outlines (= the same as the satellite image?).
Line 292: Sentence is logically not fully clear, as the DEM is part of the geodetic method (?). Or is it an additional DEM that you are referring to?
Line 320/21: You could explicitly state that Wagnon et al. used this methodology on Mera and Pokhalde glaciers.
Line 535: there is some repetition in this paragraph, when compared to the beginning of this section.
Line 604: “Yala Glacier will disappear”
Line 663: The conclusions of this discussion (about glacier length, flow, and downwasting) remains a bit elusive: Do you mean that there is a bias in the mass-balance measurements? I read in this paragraph that the detailed topographical analyses (length, flow, downwasting) are useful to better assess the mass-balance measurements. But this could be mentioned more explicitly.
Line 695: rather “Fujita and Nuimura (2011) found that…”
Line 746: or: debris-free
Line 817: maybe reformulate this sub-title; the in situ measurements will always remain the same, but the mass balance will be extrapolated to regions without in situ measurements.
Line 854: Not fully clear: I understood that the glacier-wide mass balance is given for the entire glacier as shown in Figure 1. Hence, there is a quantification for these slopes (as long as they are in the respective glacier area/outline?), but this extrapolation (which nevertheless represents a quantification) may have a certain error. It is also a bit confusing because line 855 says that this error (underestimation of ablation) can be addressed with the geodetic method, which was actually done in the presented study. Or was the applied DEM not sufficient enough (as the following sentence might suggest?).
Line 872: “on the following points”
Line 1205: Wagnon et al. 2020 is listed twice (it must be an important paper :-) )
Line 1220: The WGMS (2020a) reference might be replaced with WGMS (2021), because the 2021 database version also includes all data of the 2020 version, and hence you can just refer to the latest database version. (Unless you explicitly want to refer to some data that were in the 2020 database but are not any more or that have changed in the 2021 version; but I think, this (rare) case does not apply here). WGMS (2020b) would then be WGMS (2020).
Further point that I have noticed:
Usage of three nouns: for mass-balance rate or mass-balance monitoring etc., they are usually written with hyphen (not quite with all occurrences in the text), but other word combinations are written without (e.g. sea level rise).