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

Other literature type English OPEN
Wang, Xiaowen ; Liu, Lin ; Zhao, Lin ; Wu, Tonghua ; Li, Zhongqin ; Liu, Guoxiang (2016)

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&thinsp;%) and facing north-east (56&thinsp;%). 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&thinsp;cm&thinsp;yr<sup>&minus;1</sup> and a mean of about 37&thinsp;cm&thinsp;yr<sup>&minus;1</sup>. 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&ndash;2800&thinsp;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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