General comments

High Mountain Asia is prone to cryosphere related hazards including glacier lake outburst floods (GLOFs) which are frequently recognized as major glacier hazard in the region. Bursts of large lakes could lead to floods traveling a few hundred kilometers, dramatic damage of infrastructure and life losses. However, lack of case studies lead poor understanding of triggering mechanisms and processes for the majority of occurred GLOFs. The authors point out that it is particularly true for GLOFs happened during monsoon period, when cloud-free satellite images are limited.

Assessment of GLOF long-term conditioning and short-term triggering factors as well as flood dynamics is highly relevant topic not just for Tibet but for whole High Mountain Asia. It is especially important now considering changing environment, including lake formation, expansion and drainage, changing land use patterns, growth of population and consequent implications for GLOF hazard and risk.

The manuscript provides high-quality case study with significant conclusions, important for many high-mountain regions with rapid glacier retreat. Remote sensing approach accompanied by eye-witness analysis and numerical modelling is definitely suitable tool for this research. Scenarios for r.avaflow simulations are fully reasonable and description is clear for readers. Authors have explained obtained results and related problems in details. Hypothesis to interpret sequence of events are interesting, however it is difficult to exclude single versions at this stage. Author’s opinion on high and increasing role of lateral moraine collapses in GLOF triggering is interesting and logical despite still based on limited number of cases.

The manuscript is well written and free of technical errors, well structured, appropriate in length. References are adequate. All figures and the table are high-quality. The conclusions are clear and precise. The results obtained in this study are highly relevant to assess hazard of future GLOFs within regions with fast glacier retreat. Novelty of results is absolutely clear. I strongly recommend to publish the manuscript in the Cryosphere with very minor corrections.

Specific comments.

Line 81 – please indicate year of assessment.

Fig.2 – it will better to identify date or season and year of photos.

Fig.8 – it is not clear, why daily maximum temperature has been chosen as criteria instead of daily mean temperature. Please explain it.

Table 1 - *resolution of multispectral/panchromatic image. If so, for Ziyuan-3 02 and Gaofen-2 resolution of multispectral image is better than panchromatic?

Table 2 – a nice set of equations has been used for the volume assessments. My feeling that it will be better to include a couple of more regionally specified formulae developed by Yao et al. (2012), approach and statistics from (Veh et al., 2020, Supplementary) containing 24 Himalayan lakes which allows to refine volumetric assessments. Similarly, it will be better to include the relation between lake volume and peak discharge (Popov, 1991) was determined specifically for moraine lakes in Kazakhstan. Furthermore, in the Supplement there is no information about type of lakes have been used for equations. I might be wrong, but ice-dammed lakes were considered in some equations.  

You might also want to discuss a bit more about specific features of landslide-lake interactions and consequent impact on process chain.

Popov, N. 1991. Assessment of glacial debris flow hazard in the north Tien-Shan. In Proceedings of the Soviet-China-Japan Symposium and field workshop on natural disasters, 2–17 Sept. 1991, pp. 384–391.

Veh, G., Korup, O., Walz, A., 2020. Hazard from Himalayan glacier lake outburst floods. Proc. Natl. Acad. Sci. 117 (2), 907–912 https://doi.org/10.1073/pnas.1914898117

Yao, X., Liu, S., Sun, M., Wei, J., and Guo, W.: Volume calculation and analysis of the changes in moraine-dammed lakes in the north Himalaya: a case study of Longbasaba lake, J. Glaciol., 58, 753–760, 2012

This paper describes in detail the development of a GLOF using a wide range of technical data, remote sensing and appropriate lake and GLOF modelling.  It provides a nice regional example of how some GLOFs may develop and introduces some suggested lag effects that account for the difference in potential GLOF trigger and the actual flood. I think the paper is appropriate for The Cryosphere but some changes are suggested.  These are listed below

 In the introduction you could expand the references to include: Wilson et al (Wilson, R., Harrison, S., Reynolds, J., Hubbard, A., Glasser, N.F., Wündrich, O., Anacona, P.I., Mao, L. and Shannon, S., 2019. The 2015 Chileno Valley glacial lake outburst flood, Patagonia. Geomorphology, 332, pp.51-65).  Also: Haritashya, U.K., Kargel, J.S., Shugar, D.H., Leonard, G.J., Strattman, K., Watson, C.S., Shean, D., Harrison, S., Mandli, K.T. and Regmi, D., 2018. Evolution and Controls of Large Glacial Lakes in the Nepal Himalaya. Remote Sensing, 10(5).

 Line 115. Figure 2.  "Opposite side". Clarify this.  Also reword the caption.  What does 'front to back' refer to.

 Line 167.  Met data section.  How important are climate and weather differences over 50km in this mountainous region?  I would suggest they are significant (especially precipitation) given rainfall shadow effects.  If so, the data may not be relevant for the site.  The authors need at least to acknowledge these problems. 

Line 300.  The timing of the GLOF is not not much warmer than the mean climate, especially compared with other periods of 2020 where it is both above and below the 1986-2015 climate mean.  The potential link to precipitation is a bit more convincing but if heavy rainfall is the trigger then the use of a data set from 50km distance might not tell us much.  The authors need to reflect on these caveats and complications. 

While temperature might show some regional synchronicity, it is not very likely that precipitation does. 

Line 309.  Why do 2 volume equations not yield meaningful results?  Make sure you haven't 'cherry-picked' the ones that do!

Line 440.  An alternative assessment might conclude that the landslide and the GLOF are unrelated given the lag times.  The GLOF might just be a stochastic event?  If so, the climate attribution might be premature (which I think is likely).  At least the authors should discuss this issue.

Line 450-457.  This section is rather vague.  Please discuss what you know and point out what you don't with more clarity.

Line 489.  Attribution to climate change is very complicated.  Climate warming probably caused the lake expansion (but this might be regional), although calving might also have played a role.  The specific event could only have caused a GLOF if the lake already existed, but this does not represent a clear example of a climate change attribution.  This section is relatively weak and does not consider what attribution really means here.  I would also suggest that the issue of paraglaciation is extremely important, yet there is little consideration of this.  Papers by Ballantyne and also by Knight could be cited and discussed. 

Line 508.  Mention Wilson et al who also assessed GLOFs from moraine landslides. 

Finally, we are not told what the moraine dam is made of.  How sensitive are the model equations to whether the moraine has an ice core or is composed of sediment.  Also what type of sediment is likely, and how does this affect the model results?  Are ice-cored moraines common in the area?  At least you need to discuss these issues. 

Overall, I think this is a nice paper with excellent figures and a comprehensive modelling exercise.  It needs some changes but I think it could be published in this journal.  There is a reservation about whether this paper is only of regional interest, but I think that they produce a well-argued and comprehensive case study.

The authors have analyzed the GLOF process chain of the 2020 GLOF at Jinwuco, Tibet.

It is a robust study where the causes, impacts, and implications are well presented. The authors also point out that heavy precipitation can be an important trigger of GLOF. Meteorological conditions, especially extreme rain events, may partly melt ice in the moraine dam and weaken the moraine, or cause overfill and thermal and physical erosion of the moraine, or induce a mass movement into the lake.

The effort is relevant from a scientific point of view and definitely falls under the scope of the journal. The manuscript is well structured. I highly recommend the paper and suggest some moderate changes. Hope my comments will be useful to the authors.

See below for the comments.

Abstract:

I would suggest including some results of the most likely scenario presented in the study.

Line 25-30- It is strange to have such a long lag time of 5-17 days between the landslide and the GLOF event.  Overtopping waves are normally short-lived, and has an instantaneous or short-lived but high impact on the damming moraine. I would recommend rephrasing this sentence.

As the lag time is over several days, overfill of the lake due to rainfall can be a cause for one of the scenarios in the study??

 Introduction:

I would recommend focusing on studies that reconstructed previous GLOF events

(e.g. Westoby, M.J., Glasser, N.F., Hambrey, M.J., Brasington, J., Reynolds, J.M. and Hassan, M.A., 2014. Reconstructing historic Glacial Lake Outburst Floods through numerical modelling and geomorphological assessment: Extreme events in the Himalaya. Earth Surface Processes and Landforms, 39(12), pp.1675-1692.

Nie, Y., Liu, W., Liu, Q., Hu, X. and Westoby, M.J., 2020. Reconstructing the Chongbaxia Tsho glacial lake outburst flood in the Eastern Himalaya: Evolution, process and impacts. Geomorphology, 370, p.107393.

Westoby, M.J., Brasington, J., Glasser, N.F., Hambrey, M.J., Reynolds, J.M., Hassan, M.A. and Lowe, A., 2015. Numerical modelling of glacial lake outburst floods using physically based dam-breach models. Earth Surface Dynamics, 3(1), pp.171-199.

Majeed, U., Rashid, I., Sattar, A., Allen, S., Stoffel, M., Nüsser, M. and Schmidt, S., 2021. Recession of Gya Glacier and the 2014 glacial lake outburst flood in the Trans-Himalayan region of Ladakh, India. Science of The Total Environment, 756, p.144008.)

Last para:

I would suggest introducing the event further by adding one or two sentences to emphasize the presented case study.

Materials and methods:

Section 3.4

The values of breach and lake characteristics fit better in the Result section.

It remains unclear how the volume of the lake was empirically determined. Was it from a particular empirical equation or the average of all? Sorry if I missed it.

Section 3.5

The flow propagation is analyzed up to 1.2 km downstream. I note that validation of the flow is difficult in the downstream part of the channel. However, it can be assumed that if the initial conditions of reconstruction (trigger and breach) were validated (which the authors have done a good job), the downstream propagation more or less will represent the flow. E.g. inundations at places shown in Fig 12 and 13, table 3, etc can be helpful here to evaluate the modeled inundation.

At places in the section, results are mentioned e.g. Line-216, Line 218, etc. I would suggest shifting it to the results section.

Results:

Section 4.3 Line 310-313: As mentioned earlier the lag time between the landslide and GLOF is several days. This can be discussed.

Section 4.4. Line 319 to 321- How was the reconstructed lake volume of 13.9 M m3 calculated? This can be explained in the methodology and result section 4.2 or 4.4.

Section 4.5. Line 343 – The peak discharge reaches 10.900 m3/s. It does not reflect in the hydrograph in Fig.10.

Discussion:

The authors have done a great job here discussing the uncertainties in detail. This also answers some of my questions above.

I agree that reconstructing GLOF is associated with a lot of uncertainties, lack of evidence, the complexity of the triggering process, etc.

Evaluating multiple scenarios to reconstruct the process chains can however be useful to understand the event and not rule out the various possibilities.

Figures:

Fig-1 Township border and river colors can be changed.

Fig.2 Caption –To avoid confusion, front to back can be replaced with downstream to upstream.  Similarly Left to right or right to left can be represented in terms of directions with respect to north.  

Fig.3- recheck the scale of Fig. a; dates in a and b is not visible.

Fig. 10- Hp1, Hp2 , Qp1, Qp2…etc can be mentioned in the caption. The discharge represented on a negative scale? Sorry if I missed anything.

Table 1- Line 140 – Date or Data?

Overall a very nice study that includes remote sensing and complex modeling to understand GLOF events.

I highly recommend this paper with moderate revisions