Constantly renewing glacial lakes in the Kyrgyz Range, northern Tien Shan

Abstract. In the Kyrgyz Range of the northern Tien Shan, Central Asia, glacial lakes have been a focus of monitoring due to the increasing concern over glacial lake outburst floods (GLOFs) in the context of notable glacier recession. This study investigates (1) the historical evolution in the number and area of glacial lakes larger than 0.00045 km2 in 1968, 2000, and 2021 using Corona KH-4, Landsat 7/ETM+, and Sentinel-2 imagery, and (2) the relationship between lake development and the evolution of glacier-moraine complexes (GMCs) that contain buried ice. The number of glacial lakes doubled between 1968 and 2021, while their total area increased by 76 % from 0.80 to 1.42 km2. Over the same period, 190 of the 274 lakes that existed in 1968 had disappeared by 2000, while 154 new lakes had formed. Between 2000 and 2021, an additional 142 lakes disappeared, and 175 new lakes appeared. One lake that had vanished by 2000 reappeared by 2021. Rapid lake formation was associated with a 31 % reduction in glacier area over the past 50 years and with GMC evolution. The expansion of GMCs and melting of buried ice within GMCs produced new surface depressions (thermokarst features), which subsequently filled with water to form lakes, resulting in continuous glacial lake renewal. Thus, the continuous renewal of glacial lakes in the Kyrgyz Range results from the combined effects of glacier retreat, GMC expansion, and buried-ice melt.