Characteristics of mountain glacier surge hazard: learning from a surge event in NE Pamir, China

Abnormal glacier movement is likely to result in canyon-type hazards chain, such as the barrier lake of Yarlung Zangbo Grand Canyon formed by glacier debris flow in October 2018 in China. Glacier hazard usually evolves from the glacier surge and may occur in a regular cycle. Understanding the characteristics and process of glacier surge is important for early hazard recognition and hazard assessment. Based on field investigations, remote sensing interpretations and SAR offset-tracking surveys, this study confirms a typical glacier surge in the northeast Pamir, and presents its characteristics and processes. "Black ice" mixed moraines choking uplift and overflowing lateral marine are the most important scenic characteristics, which were formed under the conditions of stagnant glacier downstream and abundant super-glacial moraine. Glacier movement event can be divided into a five-period cycle including quiescent, inoculation, initiation, fracture and decline. This surge event lasted for about 300 days, initiated in February 2015 developed extensive fracturing zone in spring and early summer at maximum velocity of 10±0.95 m/day, declined after August 2015 and recovered to quiescent status in October 2015 for the next inoculation. The average height of glacier "receiving" area increased by 20–40 m with 2.7–3.6×10⁸ m³ ice transferred from glacier "reservoir", and this volume accumulation again require 50–100 years for glacier mass balance which gives approximately 100 years frequency of the glacier surge. Nevertheless, long-period increase of precipitation and temperature were favorable for the occurrence, hydrological instability is the direct triggering mechanism, and while the Glacier Lake Outburst Flood (GLOF) hazards are unlikely to occur with this surge.