What controls the surging of Karayaylak glacier in eastern Pamir? New insights from remote sensing data

Glacier surges in the Pamir have been widely documented, but the surge mechanism remains poorly known. The Karayaylak Glacier is the first reported surging glacier in eastern Pamir but different dates and possible triggers were published. In this research, the Karayaylak Glacier was studied using an extensive Landsat and Ziyuan-3 (ZY-3) satellite image set. The active phase initiated in May to June 2014, and experienced a peak velocity of 20.1 +/- 0.7 m d(-1) in May 2015, terminating in October 2015. During 2014-2015, the reservoir zone experienced an average surface elevation reduction of 33.1 +/- 1.5 m, and the receiving zone experienced an average surface elevation gain of 36.8 +/- 1.5 m. The large basal sliding during the active phase (2014-2015) was likely driven by high water pressure at the bed in an inefficient drainage system. A large volume of water released at the end of the active phase indicated the drainage at the glacier base became more efficient. The abrupt peak velocity, the short active phase and the changes in drainage suggest that the Karayaylak Glacier surge was controlled by hydrology. The behaviour of the Karayaylak Glacier was similar to that of the Kyagar Glacier and Shispare Glacier in the Karakoram.