Four large drainages from glacial lakes occurred during 2006–2014 in the western Teskey Range, Kyrgyzstan. These floods caused extensive damage, killing people and livestock as well as destroying property and crops. Using satellite data analysis and field surveys of this area, we find that the water volume that drained at Kashkasuu glacial lake in 2006 was 194 000 m³, at western Zyndan lake in 2008 was 437 000 m³, at Jeruy lake in 2013 was 182 000 m³, and at Karateke lake in 2014 was 123 000 m³. Due to their subsurface outlet, we refer to these short-lived glacial lakes as the “tunnel-type”, a type that drastically grows and drains over a few months. From spring to early summer, these lakes either appear, or in some cases, significantly expand from an existing lake (but non-stationary), and then drain during summer. Our field surveys show that the short-lived lakes form when an ice tunnel through a debris landform gets blocked. The blocking is caused either by the freezing of stored water inside the tunnel during winter or by the collapse of ice and debris around the ice tunnel. The draining then occurs through an opened ice tunnel during summer. The growth–drain cycle can repeat when the ice-tunnel closure behaves like that of typical supraglacial lakes on debris-covered glaciers. We argue here that the geomorphological characteristics under which such short-lived glacial lakes appear are (i) a debris landform containing ice (ice-cored moraine complex), (ii) a depression with water supply on a debris landform as a potential lake basin, and (iii) no visible surface outflow channel from the depression, indicating the existence of an ice tunnel. Applying these characteristics, we examine 60 depressions (> 0.01 km²) in the study region and identify here 53 of them that may become short-lived glacial lakes, with 34 of these having a potential drainage exceeding 10 m³ s⁻¹ at peak discharge.

To assess the current state of glacial lakes, we examine the seasonal lake-area changes of 339 glacial lakes in the Teskey and Kungoy Ranges of the Issyk-Kul Basin, Kyrgyzstan, during 2013–2016 based on optical satellite images (Landsat7/ETM+ and 8/OLI). The glacial lakes are classified into six types based on their seasonal variations in area: stable, increasing, decreasing, appearing, vanishing, and short-lived. We then track the number of each type in a given year and examine how each number changes from one year to the next. We find that many appearing, vanishing, and short-lived types occurred in both mountain ranges, having a large variability in number that is not directly related to the local short-term summer temperature anomaly, nor to precipitation or glacier recession. However, those in the Teskey Range vary significantly more than those in the Kungoy Range. To determine if the changing number and distribution of the various lake types may be due to changes in ground ice, we apply differential interferometric synthetic aperture radar (DInSAR) analysis using ALOS-2/PALSAR-2 for the debris landforms behind which glacial lakes appear. In the Teskey Range, ground ice occurs in 413 out of a total of 930 debris landforms, whereas in the Kungoy Range, ground ice occurs in 71 out of 180. In zones with predominant glacier-retreat during 1971–2010 (from Corona KH-4B and ALOS/PRISM), the Teskey Range had 180 new lake depressions as potential lake-basins, whereas the Kungoy Range had just 22. Existing depressions also expanded when melting ice produced subsidence. Such subsidence, together with debris landforms containing ground ice and ice tunnels, appear to cause the observed large number variability. In particular, the deposition of ice and debris by tunnel collapse or the freezing of storage water in a debris landform may close-off an ice tunnel, causing a lake to appear. Subsequent re-opening via melting of such blockage would produce either a vanishing or a short-lived type. In this way, the large variability in the number of each lake type and the distribution of types over this four-year period arises from regional geomorphological conditions and not directly from the local short-term summer temperature anomaly and precipitation or glacier recession.

In Kyrgyzstan, outburst flood disasters from glacial lakes are increasing. An example is the sudden drainage on 8 August 2019 of the Toguz-Bulak glacial lake in the Tosor river basin of the northern Tien Shan region. In this study, we used remote sensing and field surveys to examine the reasons for the outburst. We found that the lake area changed from 0.021 km² to 0.002 km² due to the outburst, in which most of the initial 130,000 m³ of water discharged within four hours. In examining the longer-term behavior of this lake, we found that from 2010 through 2019, it appears in June and disappears in September every year. Its maximum area occurs in late July and early August. With the expansion of the lake basin between 2010 and 2019, the lake also increased greatly in size, particularly so in the three years before the outburst, linked to high summer temperatures and the resulting higher inflow of glacier meltwater, finally leading to the sudden drainage in 2019. Before this outburst, a 2-m high moraine dam retained the lake. Continuously inflowing meltwater and the related increasing pressure by the lake water mass eventually broke the moraine dam. Satellite radar interferometry revealed active displacement fringes in the lake basin and moraine dam due to the melting and subsidence of buried ice. An analysis using digital elevation models from 1964 and 2010 also confirms the surface lowering in the lake basin by up to 8.5 m and on the moraine dam by 2 m. Such lowering of the proglacial moraine complex destabilized the moraine dam.

In the Teskey Range of the Tien Shan (Kyrgyz Republic), five outburst flood disasters from short-lived glacial lakes in 2006, 2008, 2013, 2014, and 2019 caused severe damages in the downstream part. Short-lived glacial lakes in the Teskey Range grow rapidly and drain within a few months, due to closure and opening of an outlet ice tunnel in an ice-cored moraine complex at the glacier front. In addition to these factors, summer meltwater from the glacier can cause rapid growth. Outburst floods of this lake type are a major hazard in this region and differ from the moraine-dam failures common to the eastern Himalaya. To clarify how short-lived glacial lakes store and drain water over short periods, we use results from a field survey and satellite data to analyze the water level, area, volume, and discharge of Korumdu lake (2017–2019) as well as satellite data to monitor the appearance of 160 other short-lived lakes (2013–2018). Except in 2016, Korumdu lake appeared and drained within about 1 month during all the summers. Water level data recorded by a data logger and time-lapse camera images show that the lake appeared and expanded suddenly from July to August in 2017–2019. The timing of lake appearance indicates that the lake formed when an outlet ice tunnel (subsurface channel) drainage was blocked by depositions of an ice–debris mixture due to ice melting and not by freezing of stored water. For 2017, we used uncrewed aerial vehicle (UAV)-derived digital surface models (DSMs) and water levels, finding that the lake's volume reached 234 000 m³ within 29 d, and then the water discharged for 17 d at a maximum rate of 0.66 m³/s. This discharge rate is more than 20 times smaller than those found earlier (2006–2014) for four short-lived lakes of tunnel type in this region. We argue that this large variation in discharge rates is due to variation in the dimensions of the outlet ice tunnels. For the 160 other short-lived glacial lakes, we found that 117 formed during the ice-melt period from July to September. This timing and our findings for Korumdu lake show that these 117 lakes likely formed primarily because deposition of an ice–debris mixture blocked the outlet tunnel, though increased glacial melt would also have contributed. In the Teskey Range, the appearance of short-lived glacial lakes on the moraine complexes at glacier fronts is inevitable in summer when the melting rate is high. Similar behavior of short-lived lakes may occur in other mountain regions of Central Asia, such as the Tien Shan and Pamir Mountains, wherever ice-cored moraine complexes exist within mountain permafrost zone. Moreover, increasing temperatures may increase both tunnel size and lake-basin size (lake volume), leading to increased hazard potential from such lakes in the future.

During 2006–2014 in the western Teskey Range, Kyrgyzstan, four large drainages from glacial lakes have occurred. These flooding events caused extensive damage, killing people and livestock as well as destroying bridges, roads, homes, and crops. According to satellite data analysis and field surveys, the volume of water that drained at Kashkasuu glacial lake in 2006 was 198,000 m³, that at Jeruy lake in 2013 was 163,000 m³, and that at Karateke lake in 2014 was 169,000 m³. Due to their tunnel outlet, we refer here to these glacial lakes as a tunnel-type of short-lived glacial lakes that drastically grow and drain over several months. From spring to early summer, such a lake either appears, or in some cases, significantly expands from an existing lake, and then drains during summer. Our field surveys show that these short-lived lakes form when the ice tunnels inside a debris landform get blocked. The blocking is caused either by the freezing of stored water during winter or from collapse of the ice tunnel. The draining occurs through an open ice tunnel during summer. The growth–drain cycle can repeat when the ice-tunnel closure behaves like that on supraglacial lakes on debris-covered glacier. We argue here that the geomorphological conditions in which such a short-lived glacial lake appears are (i) existence of an ice-containing debris-landform (moraine complex), (ii) existence of lake-basin depressions having its water supply on a debris-landform, and (iii) no surface water channel from lake-basin depressions. Using these geomorphological conditions, we examined 60 lake-basin depressions (> 0.01 km²) in this region and identify here 56 of them that are potential locations for a short-lived glacial lake.

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.