Acceleration Processes of Glacier Velocity Driven by Ice-Dammed Lakes: A Case Study of Southern Inylchek Glacier and Lake Merzbacher in Central Tian Shan

The ice-dammed Lake Merzbacher forms in depressions beside the Southern Inylchek Glacier and drains periodically through subglacial drainage systems, strongly influencing glacier dynamics. We applied speckle offset tracking (SPO) and multidimensional small baseline subset (MSBAS) techniques to ascending and descending Sentinel-1 images to derive three-dimensional glacier velocity time series, focusing on acceleration processes near the ice dam. Before lake drainage, the ice dam accelerated rapidly at an average rate of 1.77%/d as the lake expanded, especially when the lake area exceeded 1 km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The ice dam exhibited distinct periodic vertical motion. Upward acceleration of the ice dam was observed starting in May and peaking in summer, closely coinciding with the period of maximum lake extent and the timing of its drainage. From 2017 to 2021, the uplift height of the ice dam increased from 12.64 m to 26.75 m. Following drainage, velocities near the ice dam decreased rapidly. The maximum velocities at the ice dam and its downstream section occurred within 10 days post-drainage, indicating a dynamic response of the glacier to the drainage. On 6 August 2018, the lake reached its observed maximum area of 2.80 km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, with a maximum water depth of 76.25 m and a storage volume of 106.52*10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>. Glacier dynamics are primarily influenced by the influx of lake water into subglacial channels, where the increased water pressure plays a critical role. This study advances understanding of the interaction between glacier dynamics and the evolution of Merzbacher Lake at Southern Inylchek Glacier.