Review Surface heat fluxes at coarse-blocky Murtel rock glacier (Engadine, eastern Swiss Alps) - Amschwand et al.

The authors attempt to describe the surface energy balance in the active layer of a rock glacier in the Swiss Alps with an impressively well thought out measurement setup within a cavity complemented by a well established monitoring setup of the atmosphere above. Over two years they show how the energy input is nearly completely turned over, explaining the resilience rock glaciers have versus potential drivers of mass wasting but also providing an understanding what parameters are crucial to keep in mind in future, to anticipate the potential decay of ground ice in such landforms under a changing climate. They are also able to test a variety of stability corrections and discuss their suitability to estimate turbulent fluxes efficiently and show suitable fits for already established models for a rock glacier case.

The study is extremely well thought out, relies on an impressive instrumentation array and both methods and results are described in lucid language. As much as I would like to get further into a discussion of individual details of the study, it is already so dense and well crafted that I can not propose any big changes before I would recommend this for publication. I believe this work will be a crucial contribution to the community’s understanding of potential resilience of rock glaciers (and even debris covered ones) as well as when and how this resilience may come to an end. Future studies will hugely benefit from the ideas in monitoring and some of the concepts proposed in the Results to further this understanding. I am looking forward to this being part of future discussions on the topic.

There are very few general comments I have below and even fewer minor ones, as the authors have done an excellent job in language, syntax and copy editing already.

General:

L112: It is unclear what you mean with ‘massive ice’, please clarify. You mean depth? Or high content?

L130ff: Definitely important to point out the crucial role this laboratory has, I am just wondering if you could reduce the list of citations here to a few key publications that anyway then point to these further papers (e.g. ‘Hoelzle et al. 2002 and Scherler et al. 2014 and references therein, as well as at least 10 unpublished MSc theses’). The theses can not be directly accessed so am not sure how useful to cite here (or provide links to Uni repositories if possible). Also in references you call them ‘phdthesis’ and ‘mathesis’, if you keep them write it out so it is clear (PhD Thesis, MSc Thesis). Also you switch between ‘Umlaut’ spellings (e.g. ‘Ueber den Wärmehaushalt…’), keep it uniform.

L146: If reported in both enough if you just refer to one here.

L445: It wasn’t completely clear to me what ‘time period bias’ is supposed to mean. Can you explain that further?

L713: I am surprised this happens only ‘occasionally’ (Ts < Ta) – could you specify on how many nights or how many hourly measurements fulfilled that criterion? On debris cover we see this reversal relatively frequently.

L839: maybe better ‘daily as well as monthly’?

L851: I understand that the data was extremely difficult to retrieve and is valuable but I would invite the authors to consider making it available through a repository in the spirit of open science. I believe no scientist without the detailed field knowledge and knowledge of the setup would be able to take away any of your future research ideas before you are able to execute them. Conversely I believe that this dataset could be an extremely crucial contribution to our better understanding of cooling (or the future end of it) in such surface covers, and giving the opportunity to others who have experience in such environments to think along with this data, could accelerate our understanding even further.

Minor:

L44: ‘… exceptions being Rist and Phillips (2005) and Rist (2007)’

L85: You use the ‘sensu Oke’ reference already in L35, I think here it is redundant as this is already introduced.

L330: You mean ‘could not (!) test this bulk method’?

This manuscript presents a thorough analysis based on a substantial amount of field data. As such, it is not an easy read, but I cannot identify anything that I would suggest cutting (there is an amount of repetition that could be removed). The statements that the parametrisation “closed the monthly SEB” but “wind speeds had to be scaled to close the SEB” using a calibration parameter are alarming, but my comments are otherwise minor.

Figure 2

Photograph not mentioned in the caption.

181

Could say that the Sicart et al. (2005) correction is for interference of solar radiation.

214

The psychrometric constant here is the theoretical value for a ventilated wet bulb. Is that appropriate?

272

Missing ) in C_p

330

“could not test this bulk method”

379

The modulus for downwards longwave radiation is unnecessary

Figure 7

First reference to this figure in the text comes after Fig. 11.

The black points on top of blue points are fine on screen but did not print well.

Figure 12

The “Air flow speed proxy” axis needs an upper value.

The caption or legend should state that the dashed lines are latent heat fluxes.

757

The use of parentheses and “respectively” make for a mangled sentence.

872

Having given Ta as being measured in degrees Celsius in Table 1, need to state that this is a Kelvin temperature.

905

The first \psi_h should be \psi_m