Interactive comment on “Inventory, motion and acceleration of rock glaciers in Ile Alatau and Kungöy Ala-Too, northern Tien Shan, since the 1950s” by Andreas Kääb et al.

Abstract. Spatio-temporal patterns of rock glacier creep have rarely been studied outside the densely populated European Alps. This study investigates the spatial and temporal variability of rock glacier motion in the Ile Alatau and Kungöy Ala-Too mountain ranges, northern Tien Shan. Over the study region of more than 3000 km2, an inventory of slope movements is constructed using a large number of radar interferograms and high-resolution optical imagery. The inventory includes more than 900 landforms, of which around 550 are interpreted as rock glaciers. Out of the active rock glaciers, 45 are characterised by a rate of motion exceeding 1 m/a. From these fast rock glaciers we select six and study them in more detail (Gorodetzky, Morenny, Archaly, Ordzhonikidze, Karakoram and Kugalan Tash rock glaciers) using offset tracking between airphotos, and historical and modern very high resolution optical satellite data. Most of them show an overall increase of decadal surface velocities from the 1950s onwards with speeds being roughly two to three times higher in recent years compared to the 1950s and 1960s. This development indicates a possible significant increase in sediment and ice fluxes through rock glaciers and implies that – when compared to glacier shrinkage – periglacial sediment transport in the region seems to gain importance relative to glacial sediment transport. Those rock glacier fronts reaching the valley floors show a strongly compressive flow regime, and changes in speeds further upstream affect them only in a damped way. The only rock glacier investigated in detail that does not exhibit an overall increase in speed since the 1950s is Gorodetsky where glacier retreat and dead-ice degradation seem to have decoupled the rock glacier from its supply by glacial sediments and ice.

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Inventory and changes of rock glacier creep speeds in Ile Alatau and Kungöy Ala-Too, northern Tien Shan, since the 1950s

The Cryosphere ◽

10.5194/tc-15-927-2021 ◽

2021 ◽

Vol 15 (2) ◽

pp. 927-949

Author(s):

Andreas Kääb ◽

Tazio Strozzi ◽

Tobias Bolch ◽

Rafael Caduff ◽

Håkon Trefall ◽

...

Keyword(s):

High Resolution ◽

Tien Shan ◽

Spatial And Temporal Variability ◽

European Alps ◽

Material Transport ◽

Rock Glacier ◽

Study Region ◽

Rock Glaciers ◽

The 1950S ◽

Northern Tien Shan

Abstract. Spatio-temporal patterns related to the viscous creep in perennially frozen sediments of rock glaciers in cold mountains have rarely been studied outside the densely populated European Alps. This study investigates the spatial and temporal variability of rock glacier movement in the Ile Alatau and Kungöy Ala-Too mountain ranges, northern Tien Shan, a region with particularly large and fast rock glaciers. Over the study region of more than 3000 km2, an inventory of slope movements was constructed using a large number of radar interferograms and high-resolution optical imagery. The inventory includes more than 900 landforms, of which around 550 were interpreted as rock glaciers. Out of the active rock glaciers inventoried, 45 are characterized by a rate of motion exceeding 100 cm/a. From these fast rock glaciers we selected six (Gorodetzky, Morenny, Archaly, Ordzhonikidze, Karakoram, and Kugalan Tash) and studied them in more detail using offset tracking between repeat aerial images and historical and modern high-resolution optical satellite data. Two of these rock glaciers showed a steady increase in decadal surface velocities from the 1950s onwards, with speeds being roughly 2 to 4 times higher in recent years compared to the 1950s and 1960s. Three rock glaciers showed similar accelerations over the last 1 to 2 decades but also phases of increased speeds in the 1960s. This development indicates a possible significant increase in current sediment and ice fluxes through rock glaciers and implies that their material transport in the region might gain geomorphodynamic importance relative to material transport by glaciers, assuming the latter decreases together with the regional glacier shrinkage. The study demonstrates how air and satellite image archives are exploited to construct one of the longest decennial times series of rock glacier speeds currently available. Our results are in line with findings from Europe about rock glacier speeds increasing with atmospheric warming and underline local variability of such an overall response.

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Characteristics and Origin of Rock Glaciers in Northern Tien Shan (Kazakhstan/Kyrgyzstan)

Permafrost and Periglacial Processes ◽

10.1002/ppp.1825 ◽

2014 ◽

Vol 25 (4) ◽

pp. 320-332 ◽

Cited By ~ 26

Author(s):

Tobias Bolch ◽

Aldar P. Gorbunov

Keyword(s):

Tien Shan ◽

Rock Glaciers ◽

Northern Tien Shan

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Mapping and inventorying active rock glaciers in the northern Tien Shan of China using satellite SAR interferometry

The Cryosphere ◽

10.5194/tc-11-997-2017 ◽

2017 ◽

Vol 11 (2) ◽

pp. 997-1014 ◽

Cited By ~ 26

Author(s):

Xiaowen Wang ◽

Lin Liu ◽

Lin Zhao ◽

Tonghua Wu ◽

Zhongqin Li ◽

...

Keyword(s):

Quantitative Information ◽

Google Earth ◽

Tien Shan ◽

Sar Interferometry ◽

Western China ◽

Mountain Ranges ◽

Optical Images ◽

Rock Glaciers ◽

Altitudinal Limit ◽

Northern Tien Shan

Abstract. Rock glaciers are widespread in the Tien Shan. However, rock glaciers in the Chinese part of the Tien Shan have not been systematically investigated for more than 2 decades. In this study, we propose a new method that combines SAR interferometry and optical images from Google Earth to map active rock glaciers (ARGs) in the northern Tien Shan (NTS) of China. We compiled an inventory that includes 261 ARGs and quantitative information about their locations, geomorphic parameters, and downslope velocities. Our inventory shows that most of the ARGs are moraine-derived (69 %) and facing northeast (56 %). The altitude distribution of ARGs in the western NTS is significantly different from those located in the eastern part. The downslope velocities of the ARGs vary significantly in space, with a maximum of about 114 cm yr−1 and a mean of about 37 cm yr−1. Using the ARG locations as a proxy for the extent of alpine permafrost, our inventory suggests that the lowest altitudinal limit for the presence of permafrost in the NTS is about 2500–2800 m, a range determined by the lowest ARG in the entire inventory and by a statistics-based estimation. The successful application of the proposed method would facilitate effective and robust efforts to map rock glaciers over mountain ranges globally. This study provides an important dataset to improve mapping and modeling permafrost occurrence in vast western China.

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Review comment on "Mapping and inventorying active rock glaciers in the Northern Tien Shan (China) using satellite SAR interferometry" by Wang et al.

10.5194/tc-2016-254-rc2 ◽

2016 ◽

Author(s):

Tazio Strozzi

Keyword(s):

Tien Shan ◽

Sar Interferometry ◽

Review Comment ◽

Rock Glaciers ◽

Northern Tien Shan

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Mapping and inventorying active rock glaciers in the Northern Tien Shan (China) using satellite SAR interferometry

10.5194/tc-2016-254 ◽

2016 ◽

Author(s):

Xiaowen Wang ◽

Lin Liu ◽

Lin Zhao ◽

Tonghua Wu ◽

Zhongqin Li ◽

...

Keyword(s):

Quantitative Information ◽

Google Earth ◽

Tien Shan ◽

Sar Interferometry ◽

Western China ◽

Mountain Ranges ◽

North East ◽

Optical Images ◽

Rock Glaciers ◽

Northern Tien Shan

Abstract. Rock glaciers are widespread in the high mountains of western China. However, they have not been systematically investigated for more than two decades. In this study, we propose a new method that combines SAR interferometry and optical images from Google Earth to map active rock glaciers (ARGs) in the Northern Tien Shan (NTS) in China. We compiled an inventory that includes 261 ARGs and quantitative information about their locations, geomorphic parameters, and down-slope velocities. Our inventory shows that most of the ARGs are moraine-derived (68 %) and facing north-east (56 %). The altitude distribution of ARGs in the western NTS is significantly different from those located in the eastern part. The down-slope velocities of the ARGs vary significantly in space, with a maximum of about 114 cm yr−1 and a mean of about 37 cm yr−1. Using the ARG locations as a proxy for the extent of alpine permafrost, our inventory suggests that the lowest altitudinal limit for the presence of permafrost in the Northern Tien Shan is about 2500–2800 m, a range determined by the lowest ARG in the entire inventory and by a statistics-based estimation. The successful application of the proposed method would facilitate an effective and robust effort to map rock glaciers over major mountain ranges and provide important datasets to improve mapping and modeling permafrost distribution in vast western China.

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