Progressive advance and runout hazard assessment of a low-angle valley glacier in East Kunlun Mountains from multi-sensor satellite imagery analysis

Abstract. Collapses of large parts of low-angle mountain glaciers in recent years have raised great attention due to their threats to lives and properties downstream. While current studies have mainly focused on post-event analysis, assessing the potential hazard of glaciers prone to collapse is rare. Here we presented a comprehensive analysis of the dynamics and runout hazard of a low-angle (~ 20°) valley glacier, close to the Qinghai–Tibet railway and highway, in the Kunlun Pass of East Kunlun Mountains on the Qinghai–Tibet Plateau. The changes in morphology, terminus position, and surface elevation of the glacier between 1975 and 2019 were characterized with multi-sensor remote sensing data including a stereo-image pair from the historical KH-9 spy satellite, six Digital Elevation Models (DEMs), and nine high-resolution images from Planet Labs. The surface flow velocities of the glacier tongue between 2009 and 2019 were also tracked based on cross-correlation of Planet images. Our observations show that the glacier snout has been progressively advancing in recent four decades, with a stepwise increase of advance velocity from 4.25 ± 0.28 m a−1 between 1975 and 2009 to 32.53 ± 4.45 m a−1 between 2015 and 2019. DEM differencing confirms the glacial advance, with surface thinning in the source region and thickening in the tongue region. The net volume loss over the glacier tongue was about 11.21 ± 2.66 × 105 m3 during 1975–2019. Image cross-correlation reveals that the surface flow velocity of the glacier tongue has been increasing in recent years, with the mean velocity below 4800 m almost trebled from 22 ± 4 cm a−1 during 2009–2012 to 61 ± 5 cm a−1 during 2016–2019. Piecing these observations together, we suggest that the flow of the glacier tongue is mainly controlled by the geometry of the glacier, while the presence of an ice-dammed lake and a supraglacial pond implies a hydrological influence as well. Taking the glacier tongue as an avalanche source, we quantitively simulated the potential runout distance using the Voellmy–Salm avalanche model. The simulations predict that the avalanche of the glacier tongue will result in a maximum runout distance of about 1.3 km with moderate friction parameters, unlikely to threaten the safety of the Qinghai–Tibet railway.