Abstract
Glacier surge, which causes a quick movement of ice mass from high to low elevation, is closely associated to the glacial hazards of debris flows and glacial lake outburst floods. Over the West Kunlun Shan, surge events have been detected for some glaciers, however, the characteristics (e.g., the active phase) of the identified surge-type glaciers are not fully understood due to the paucity of long-term observations of glacier changes. In this study, we investigated the geometric evolution of the Chongce Glacier (a surge-type glacier) over the past five decades. Glacier elevation changes were observed by comparing topographic data from different times. Surface velocity and terminus position were derived using a cross-correlation algorithm and band ratio method, respectively. A decreasing rate of glacier surface thinning was found for the Chongce Glacier during the studied period. Glacier elevation changes of −0.46 ± 0.12, −0.12 ± 0.05, and 0.27 ± 0.11 m yr−1 were estimated for the periods of 1970–2000, 2000–2012, and 2012–2018, respectively. Moreover, this glacier experienced obvious surface lowering over the terminus zone and clear surface thickening over the upper zone during 1970–2000, and the opposite during 2000–2018. Surface velocity of the Chongce Glacier was less than 300 m yr−1 in 1990–1993, and then quickly increased to more than 1000 m yr−1 between 1994 and 1998, and dropped to less than 50 m yr−1 in 1999–2020. Over the past five decades, the Chongce Glacier generally experienced a slight retreat, except for a terminus advance from 1995 to 1999. According to the spatial pattern of glacier elevation changes in 1970–2000 and the long-term changes of glacier velocity and terminus position, the recent surge event at the Chongce Glacier likely initiated in winter 1993 and terminated in winter 1998. Furthermore, the start date, end date, and duration of the active phase indicate that the detected surge event was likely triggered by a thermal mechanism.
Highlights
Surge-type glaciers feature periodically alternating long quiescent phases and short active phases [1,2,3]
In the period of 1970–2000, pronounced glacier thickening can be observed over the terminus zone, whereas glacier thinning is apparent over the upper zone (Figure 2a)
Between 2000 and 2018, the Chongce Glacier experienced obvious surface lowering over the terminus zone, and clear surface thickening is apparent over the upper zone (Figure 2b,c)
Summary
Surge-type glaciers feature periodically alternating long quiescent phases and short active phases [1,2,3]. A surge event can threaten the safety of the downstream communities, and can result in river blocking [8,9,10,11]. A surge event at the Kyagar Glacier in the Chinese Karakoram mountains during 2015–2016 caused the formation of an ice-dammed lake and subsequent glacial lake outburst floods [9]. Glacier in the Karakoram mountains led to an advancement of about 12 km in three months, and engulfed the villages, farmland, and forest downstream [10]. In summer 2016, a surge event was recorded in the western Tibetan Plateau, where two massive glaciers
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