10:45 〜 12:15
[ACC25-P03] Condition and evolution of glacial lakes in the northern Tien Shan of Kyrgyzstan, Central Asia.
キーワード：glacier, glacial lakes, northern Tien Shan, area change
The disappearance of mountain glaciers and the thawing of permafrost has resulted increasing the size and number of glacial lakes in the northern Tien Shan in the Kyrgyz Republic. However, the condition of glacial lakes is not well documented in our study site and some of the lake characters remain unclear. A detailed understanding of the condition of glacial lakes can allow for mitigating the lake drainage hazards in the area.
Therefore, in this study we evaluated the variability of glacial lakes in the northern Tien Shan Mountains of Kyrgyzstan using Landsat 7ETM, Landsat 8OLI, Sentinel-2 and PlanetScope optical satellite images from 2000 to 2021. Corona KH-4B data (1964-1974) also were used for the analysis of glacial lakes at glacier fronts.
Results confirm that from 1974 to 2000 the total number of glacial lakes in the region increased by 161 (total 288 in 2000). However, since 2000 their number were increased by 382 (total 831 in 2021). Based on satellite images taken between 2000 and 2021, we found seasonality in the character of glacial lakes, 786 lakes have been found to be unstable during our observation period. From 2000 to 2021, 160 glacial lakes showed significant variations in area or expanded continuously. Meanwhile, 408 glacial lakes are found to be newly emerging. In 2021, the average elevation of newly appeared lakes in the Kyrgyz Range has risen 15 m higher than compared to 2018 and 32 m higher in the Teskey Range compared to 2013. Before 2018, glacial lakes were distributed below 3900 m, and, by 2021 their appearance reached higher than 4100 m. This is because the elevation of the zero isotherms has increased and with the retreat of the glaciers glacial lakes appeared higher and higher above sea level.
We found that most glacial lakes were proglacial lakes in 1964-2000, which appeared at glacier fronts or on the glacier moraines amid glacier retreats. However, since 2000, some proglacial lakes changed their dynamics to unstable or a short-lived position and started to appear more frequently. As it turned out, if between 1964-2000 glacial lakes mostly appeared as the retreat of glaciers, after the 2000s, the moraines of study region were more significantly exposed to degradation induced by climate change and the drainage system of glacial lakes changed from surface to underground type. It resulted in the character of glacial lakes becoming seasonality. The study also reviled the shifts in the elevation of glacial lakes up over 3500 m asl, and below 3500 m glacial lakes disappearing or appear less because of the complete degradation of debris-covered dead ice and too far distance from glacier terminus.
Therefore, in the northern Tien Shan Mountains glacial lakes will continue to expand or appear new or short-lived lakes emerge occasionally because of melting of glaciers and degradation of ice-cored moraine complexes within mountain permafrost zone.
Therefore, in this study we evaluated the variability of glacial lakes in the northern Tien Shan Mountains of Kyrgyzstan using Landsat 7ETM, Landsat 8OLI, Sentinel-2 and PlanetScope optical satellite images from 2000 to 2021. Corona KH-4B data (1964-1974) also were used for the analysis of glacial lakes at glacier fronts.
Results confirm that from 1974 to 2000 the total number of glacial lakes in the region increased by 161 (total 288 in 2000). However, since 2000 their number were increased by 382 (total 831 in 2021). Based on satellite images taken between 2000 and 2021, we found seasonality in the character of glacial lakes, 786 lakes have been found to be unstable during our observation period. From 2000 to 2021, 160 glacial lakes showed significant variations in area or expanded continuously. Meanwhile, 408 glacial lakes are found to be newly emerging. In 2021, the average elevation of newly appeared lakes in the Kyrgyz Range has risen 15 m higher than compared to 2018 and 32 m higher in the Teskey Range compared to 2013. Before 2018, glacial lakes were distributed below 3900 m, and, by 2021 their appearance reached higher than 4100 m. This is because the elevation of the zero isotherms has increased and with the retreat of the glaciers glacial lakes appeared higher and higher above sea level.
We found that most glacial lakes were proglacial lakes in 1964-2000, which appeared at glacier fronts or on the glacier moraines amid glacier retreats. However, since 2000, some proglacial lakes changed their dynamics to unstable or a short-lived position and started to appear more frequently. As it turned out, if between 1964-2000 glacial lakes mostly appeared as the retreat of glaciers, after the 2000s, the moraines of study region were more significantly exposed to degradation induced by climate change and the drainage system of glacial lakes changed from surface to underground type. It resulted in the character of glacial lakes becoming seasonality. The study also reviled the shifts in the elevation of glacial lakes up over 3500 m asl, and below 3500 m glacial lakes disappearing or appear less because of the complete degradation of debris-covered dead ice and too far distance from glacier terminus.
Therefore, in the northern Tien Shan Mountains glacial lakes will continue to expand or appear new or short-lived lakes emerge occasionally because of melting of glaciers and degradation of ice-cored moraine complexes within mountain permafrost zone.