Short-term glacier velocity changes at West Kunlun Shan, Northwest Tibet, detected by Synthetic Aperture Radar data

Seasonal glacier velocity changes across the High Arctic, including the Greenland Ice Sheet, have been observed and have attracted significant attention over the past decade. However, it remains uncertain how much short-term variability exists in other polythermal glaciers, particularly those in High Asia. Here we report satellite radar image analyses that reveal diverse glacier surface velocities and their evolution in West Kunlun Shan (WKS), NW Tibet, where little is known about glacier dynamics. On the basis of radar images obtained from 2003 to 2011, we examined 36 glaciers, and classified them into two classes according to their multi-temporal velocity profiles: 25 as normal-flow type (surface velocity reaches maxima around the middle part, and gradually approaches zero toward downstream and upstream), and four as surging type (surface velocities are greater than 150 m/yr, and/or the terminus advance is recognized from the radar images). Seven other glaciers do not fit the former two classes, and reveal stagnant velocity profiles that are nearly zero in the lower part but are similar to those of the normal type in the upper part. Although these glaciers could be just stagnant tongues indicative of receding normal type glaciers, given the temporal evolution at the Zhongfeng Glacier, the stagnant type possibly represents a quiescent phase of the surging type glaciers. While glacier surfaces are mostly clean with limited debris-cover, except near the termini, surge-type glaciers might be common in WKS. The observed short-term velocity changes provide us with evidence for efficient basal slip even at the high-elevation polythermal glaciers. This study demonstrates that frequent radar image acquisitions are helpful to understand short-term velocity changes at remote glaciers in detail.