Rock glaciers in the Daxue Shan, southeastern Tibetan Plateau: an inventory, their distribution, and their environmental controls

Rock glaciers are typical periglacial landforms. They can indicate the existence of permafrost, and can also shed light on the regional geomorphological and climatic conditions under which they may have developed. This article provides the first rock glacier inventory of the Daxue Shan. The inventory has been based on analyses of Google Earth imagery as well as upon scientific validation in the field. In total, 295 rock glaciers were identified in the Daxue Shan, covering a total area of 10 55.70 km, between the altitudes of 4,300 and 4,600 m above sea level (asl). Supported by the ArcGIS and SPSS software programs, we extracted and calculated the parameters of these rock glaciers, and analyzed the characteristics of their spatial distribution within the Daxue Shan. Our inventory suggests that the lower altitudinal boundary for permafrost across the eight aspects of slopes observed in the Daxue Shan (i.e., slopes facing north, northeast, east, southeast, south, southwest, west and northwest) differs significantly. The lower altitudinal permafrost boundary is ~104 m lower on easternrather than western15 facing slopes. The analysis of rock glaciers parameters indicates that the formation of rock glaciers is closely related to local topographical parameters. These results show that environmental controls (i.e., topographical, climatic, lithological factors) greatly affect the formation and development of rock glaciers. This study provides important data for exploring the relation between maritime periglacial environments and the development of rock glaciers on the southeastern Tibetan Plateau (TP). It may also highlight the characteristics typical of rock glaciers found in a maritime setting. 20

active, inactive, and relict rock glaciers three types (Sattler et al., 2016). In general, the presence of ice within an active/inactive rock glaciers have a steep (>35°) frontal slope (Ikeda and Matsuoka, 2002) and a well-developed flow-like morphology defined by sets of parallel and curved ridges separated by long V-shaped furrows (Barsch, 1996;Roer and Nyenhuis, 2007), the absence or the sparse occurrence of vegetation (Onaca et al., 2013). Inactive rock glaciers also contain ice, but are immobile. In contrast, relict rock glaciers are characterised by surface collapse features as a result of permafrost degradation, with gentler frontal and marginal slopes, and often vegetation cover (Wahrhaftig and Cox, 1959;Haeberli, 1985;Scotti et al., 2013)." (P5L2-P5L9) (2) Thank you for pointing out our mistaken expression and we have removed the relevant sentences "as well as upon scientific validation in the field" in the abstract and "Ground truthing was only possible at a limited number of rock glacier sites within the Daxue Shan, and no fossilized glacier-derived features were visited." in the paper. At present, due to the inconvenience of transportation in the Daxue Shan, it is difficult for humans to go to the field to obtain field data. Therefore, we mainly identify rock glaciers through visual interpretation of google earth remote sensing images.
(3) We have added data and transformed Table 3 into Figure 7 to better illustrate the freezing and thawing effect of rock glaciers in the Daxue Shan. However, there are currently only four meteorological stations. In the future, we hope to seek funding from relevant agencies and establish more meteorological stations in high altitudes.

Results and Discussion
Since you manually derived the RG geometries it would be great if you could elaborate on the accuracy of your method. Did you have several persons working on the digitization of the RGs and did they perform differently or do you have more accurate field data which you could compare to the manual mapping and are there any differences? I would suggest to refrain from using latitude and longitude to analyse RG properties since lat and long do not describe any environmental parameter but rather the regional topographical setting is more important. And thats the parameter that changes with Lat and Long. Focus more on the regional settings such as aspects, debris sources and valley/slope orientation to interpret RG properties. It would be very beneficial if you include a description of the topographical characteristics of the study site in relation to the formation and evolution of rock glaciers. This would also help to understand the spatial setting which goes with the latitudinal impact.
Reply: Thank you for your advice and it is very important. We have analyzed and discussed about the accuracy and uncertainty of method (P6L10~P6L17), and we have two persons working on the digitization of the rock glaciers and the performance is basically the same. At present, due to the inconvenience of transportation, it is difficult for humans to go to the field to obtain field data. Therefore, we mainly identify rock glaciers through visual interpretation of google earth remote sensing images. In addition, we compared our manual mapping and the Gruber's (2012) global Permafrost Zonation Index (PZI) map, and found that the rock glaciers distribution in the Daxue Shan is in good agreement with the PZI on the whole (Fig. 3). (P12L13~P12L16) Your advice is very important, indeed, longitude and latitude do not describe environmental parameter. However, we can use longitude and latitude to analyze the spatial distribution and aggregation state of rock glaciers from the perspective of geography. Then, we analyze the properties of rock glaciers by using other parameters other than longitude and latitude (i.e. the parameter that changes with longitude and latitude). As you said, regional settings are very important. Therefore, we are also concerned about aspects, debris sources and valley/slope orientation to interpret rock glaciers properties, to explore the correlation between the local topographical characteristics and the formation, evolution, spatial distribution of rock glaciers.
We have added the description sentences of the topographical characteristics "With the increase of latitude from the south to the north in the Daxue Shan, the high altitude slopes increase, and flow further downvalley than low altitude, these topographical characteristics result in the rock glaciers altitude asl and length increase with latitude." (P10L13~P10L16) 4.2.3 Lithological controls on rock glaciers. The lithological setting influences RG formation mainly by steepness and sedimentation rates contributing debris to the landforms. Please include this aspect into your elaboration and cite some references supporting the influence of lithology towards RG formation and evolution. sentences "as well as upon scientific validation in the field" and "Ground truthing was only possible at a limited number of rock glacier sites within the Daxue Shan, and no fossilized glacier-derived features were visited." in the paper. At present, due to the inconvenience of transportation in the Daxue Shan, it is difficult for humans to go to the field to obtain field data. Therefore, we mainly identify rock glaciers through visual interpretation of google earth remote sensing images.
Next is the reply to the supplement to this comment: https://www.the-cryospherediscuss.net/tc-2017-290/tc-2017-290-RC1-supplement.pdf P2L5: All Rock glaciers move down valley. Otherwise they would move at all. Also lobate RGs are inclined and creep therefore down valley. Please rephrase... Reply: Thanks for pointing out this. We have rewritten the relevant sentences to "As the bodies of rock glaciers are similar to moraines in that," (P2L4~P2L5) P2L7: That's a continuum. Many Himalayan RGs develop out of moraines and it is hard to distinguish where the moraine ends and the RG begins. Please mention that.
Reply: Thanks very much for your insightful suggestion. We have added the sentence "Many Himalayan rock glaciers develop out of moraines and it is hard to distinguish where the moraine ends and the rock glacier begins."(P2L6~P2L7) P2L12: What does block type mean? It is agreed upon that rock glaciers move due to the viscous creep of the rock-ice melange and can be described and modelled as such. see wahrhaftig & Cox 1959, Olyphant 1983. references in the written comments.
Reply: This is our misnomer and we have changed "block-type movement" to "creep movement". (P2L13) P2L16: How are they more accurate? I would prefer advanced or powerful.
Reply: We are grateful for the suggestions, and we have changed "accurate" to "advanced". (P2L17) P3L1: Do you mean underneath the rock glaciers or inside of the rock glacier? or altitudinal? Please rephrase.
Reply: We have rewritten the sentence is "However, the study of the rock glaciers of the Daxue Shan on the southeastern margins of the TP is less involved." (P3L9~P3L10) P3L15: and natural hazards and or environmental planning/management. Reply: We have rewritten the sentence is "It is therefore of particular importance to study the environmental controls on the rock glaciers of the Daxue Shan as an aid to the further study of the complex geographical environment, natural hazards, environmental planning and management found on the southeastern margins of the TP." (P3L15) P5L12: reference?
Reply: The reference "A geological layer (using a geological map with a scale of 1:500,000 from the China Geological Survey)" has been added in the revised version. (P5L19) P7L22: Isn't this also a function of sediment supply and terrain inclination? Maybe you can discuss the impact of terrain topography and sediment/ice supply and its impact on flow velocity and RG morphology.
Reply: We are grateful for the suggestions and we have added the sentence "compared with lobate rock glaciers, moraine-type and tongue-shaped rock glaciers have more sediment supplies and last longer on gentle slope, indicating that moraine-type and tongue-shaped rock glaciers flow further than lobate rock glaciers." (P9L2~P9L4) P8L7: Probably be there are more steep rock walls on the north faces producing debris. Please check.
Reply: Your opinion is really right, and we have added the sentence "However, there are more steep rock walls on the north faces producing debris, north-facing (i.e., N, NW and NE) slopes seem to be more favorable for the formation of lobate rock glaciers than do south-facing (i.e., SW, S and SE) ones (Fig. 5)."(P9L21) P8L21: How does the regional climate change with the latitude? I would argue that the latitude oer se isn't so important but rather the regional climate, topography and environmental setting.
Reply: Indeed, regional climate, topography and environmental setting are very important, and we have discussed them in the paper. Latitude may have little impact on the regional climate of a single small area. However, when comparing two areas in different latitudes (Daxue Shan: 30°N, Tianshan Mountains: 40°45°N) (Zhu, 1992;Zhu et al., 1992;Wang et al., 2017), the temperature will decrease with the increase of latitude, resulting in latitude zonal differences in climate between different regions (Daxue Shan and Tianshan Mountains). P9L1: Because there aren't so many of these W-E facing slopes?
Reply: Yes, the topographical characteristics of the Tianshan Mountains are roughly W-E in presentation, east-and west-facing slopes are less than the north-and south-slopes, these topographical characteristics are not conducive to the formation and development of rock glaciers, except on its north-slopes.
P9L15: You just mentioned in line 11 that local topography and local climate are very important. Latitude and longitude have no impact on these parameters. So I'd say any correlation with these parameters is rather an expression for other local parameters influenced by e.g. topography and any interpretation including lat and long doesn't help much.
Reply: Latitude and longitude may have little effect on other parameters of a single rock glacier; however, it can reflect the spatial distribution and aggregation characteristics of 295 rock glaciers in the Daxue Shan. It is one of the topics (titles) discussed in this paper: "their distribution", which focuses on the study of the relationship between local topography and the spatial distribution (Johnson et al., 2007) of 295 rock glaciers from the geographic space macro perspective. Therefore, we have rewritten the sentence is "In summary, the topography of the Daxue Shan is an important environmental control on the formation, development and spatial distribution of the region's rock glaciers."(P11L5~ P11L7) P9L17: This is trivial.
Reply: Thanks for pointing out this and we have removed the relevant sentences "a significantly positive correlation (p=0.01) between rock glacier area, length and width." P9L22: Does this only hold true for active RGs or also for relict RGs?
Reply: Revised data shows that there is not enough evidence and we have removed the sentences "larger-scale rock glaciers occur mainly in the higher mountains". P10L1: It would be very beneficial if you include a description of the topographical Characteristics somewhere in the discussion.
Reply: We have added the description sentences of the topographical characteristics: "With the increase of latitude from the south to the north in the Daxue Shan, the high altitude slopes increase, and flow further downvalley than low altitude, these topographical characteristics result in the rock glaciers altitude asl and length increase with latitude." (P10L13~P10L16) P10L7: Why? I would awesome because of temperature but further elaboration would be helpful.
Reply: We have added the further elaboration sentences "with the increase of longitude and the decrease of altitude, the closer it is to warm and humid, which kind of climatic conditions are not conducive to the formation of permafrost landforms such as rock glaciers." (P10L21~P10L23) P10L13: This hold trues for all the slopes in the world...
Reply: Revised data shows that there is not enough evidence and we have removed the sentences "The fact that mean gradient of slope and aspect exhibit a significantly negative correlation (p=0.01) reflects the topographical realities of the Daxue Shan, where sunny slopes are often less steep than shady ones". P11L1: Maybe mention the global permafrost distribution maps and their take on the Daxue Shan (e.g. Gruber et al. 2012).
Reply: We have added the global permafrost distribution maps and their take on the Daxue Shan. As shown below: "The cryosphere reacts sensitively to climate change (Gruber et al., 2017). Compared with Gruber's (2012) global Permafrost Zonation Index (PZI) map, the rock glaciers distribution in the Daxue Shan is in good agreement with the PZI on the whole and some rock glaciers are situated within the PZI fringe of uncertainty (Fig. 3). Strictly controlled by the temperature decreasing with increasing altitude, further indicating the climatic controls on development of permafrost such as rock glaciers." (P12L13~P12L16)