Mapping and Characterizing Rock Glaciers in the Arid Western Kunlun
Mountains Supported by InSAR and Deep Learning
Abstract
Rock glaciers manifest the creep of mountain permafrost occurring in the
past or at present. Their presence and dynamics are indicators of
permafrost distribution and changes in response to climate forcing.
There is a complete lack of knowledge about rock glaciers in the Western
Kunlun Mountains, one of the driest mountain ranges in Asia, where
extensive permafrost is rapidly warming. In this study, we first mapped
and quantified the kinematics of active rock glaciers based on satellite
Interferometric Synthetic Aperture Radar (InSAR) and Google Earth
images. Then we trained DeepLabv3+, a deep learning network for semantic
image segmentation, to automate the mapping task. The well-trained model
was applied for a region-wide, extensive delineation of rock glaciers
from Sentinel-2 images to map the landforms that were previously missed
due to the limitations of the InSAR-based identification. Finally, we
mapped 413 rock glaciers across the Western Kunlun Mountains: 290 of
them were active rock glaciers mapped manually based on InSAR and 123 of
them were newly identified and outlined by deep learning. The rock
glaciers are categorized by their spatial connection to the upslope
geomorphic units. All the rock glaciers are located at altitudes between
3,390 m and 5,540 m with an average size of 0.26 km2 and a mean slope
angle of 17°. The median and maximum surface downslope velocities of the
active ones are 17±1 cm yr-1 and 127±6 cm yr-1, respectively.
Characteristics of the inventoried rock glaciers provided insights into
permafrost distribution in the Western Kunlun Mountains.