Warming in the Third Pole region accelerates glacier and snow melt, leading to a rise in glacial lake numbers and sizes. However, accurately measuring their water level changes poses challenges, hindering precise volume assessments and evaluation of glacier mass balance contributions. Here, we took the Ak-Shyirak glaciers and the largest Petrov proglacial lake in the Central Tien Shan as a case study to investigate these phenomena. Specifically, firstly, we conducted mass balance assessments for the Ak-Shyirak massif for six sub-periods from 1973 to 2023 using KH-9 DEMs, SRTM DEM, and ASTER DEMs. The results indicate that glaciers were in a state of rapid melting for 1980–2000 and 2005–2012, with rates of −0.46 m w.e./a and − 0.37 m w.e./a; moderate melting during 1973–1980 and 2012–2018, with rates of −0.26 m w.e./a and − 0.28 m w.e./a, while slower melting during 2000–2005 and 2018–2023, with rates of −0.08 m w.e./a and − 0.18 m w.e./a. Subsequently, we conducted assessments of the area change of Petrov Lake for 1973–2023 using KH-9 and Landsat images. The results reveal a significant increase in the glacial lake area by 2.81 km2 (150.25 %), corresponding to a rate of 0.054 km2/a over the entire study period. Furthermore, we conducted monitoring of Petrov Lake's water level from 2019 to 2023 by utilizing ICESat-2 laser altimetry and Sentinel-3 radar altimetry data. Our findings indicate that the glacial lake level shows intra-annual fluctuations and inter-annual change, with amplitudes of 0.67 ± 0.09 m and increase rate of 0.30 ± 0.05 m/a, respectively, as determined by a periodic fluctuation model. Finally, after a comprehensive analysis of ERA5-Land meteorological data, topography, glacier mass balance, lake area, and water level, we can draw the following conclusions: (1) glacier mass balance is predominantly influenced by the air temperature and snowfall; (2) changes in glacial lake area are driven by factors such as the lake basin, glacier surface elevation, and drainage event; (3) intra-annual fluctuations and inter-annual change in glacial lake levels are both primarily influenced by precipitation and glacier mass balance; (4) glacier mass balance accounts for (36.19 ± 8.47)% of the water supply contributing to changes in glacial lake volume change, while precipitation represents (63.81 ± 5.08)%. Glacier mass balance measurements reveal changing patterns in the Ak-Shyirak massif, Central Tien Shan, due to climate change. Inaugural proglacial lake level measurements provide unique insights into both intra-annual and inter-annual changes, serving as a reference for Third Pole region-wide glacial lake monitoring. Additionally, quantifying glacier meltwater contributions to lake volumes will aid future glacial lake evaluation and potential outburst flood impacts.

中文翻译：

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使用多源卫星数据分析了 1973 年至 2023 年天山中部 Ak-Shyirak 地块 Petrov 湖的冰川质量变化和演变


第三极地区的变暖加速了冰川和积雪的融化，导致冰川湖的数量和规模增加。然而，准确测量它们的水位变化带来了挑战，阻碍了精确的体积评估和冰川质量平衡贡献的评估。在这里，我们以 Ak-Shyirak 冰川和天山中部最大的彼得罗夫前冰湖为案例研究来研究这些现象。具体来说，首先，我们使用 KH-9 DEM、SRTM DEM 和 ASTER DEM 对 1973 年至 2023 年的六个子时期的 Ak-Shyirak 地块进行了质量平衡评估。结果表明，冰川在 1980-2000 年和 2005-2012 年处于快速融化状态，速率为 -0.46 m w.e./a 和 -0.37 m w.e./a;1973-1980 年和 2012-2018 年期间中度融化，熔化率为 -0.26 M W.E./A 和 -0.28 M W.E./A，而 2000-2005 年和 2018-2023 年期间融化较慢，熔化率为 -0.08 M W.E./A 和 - 0.18 M W.E./A。随后，我们使用 KH-9 和 Landsat 图像对 1973-2023 年彼得罗夫湖的面积变化进行了评估。结果显示，冰川湖面积显著增加了 2.81 km2 （150.25 %），相当于整个研究期间的 0.054 km2/a 的速率。此外，我们利用 ICESat-2 激光测高和 Sentinel-3 雷达测高数据对 2019 年至 2023 年彼得罗夫湖的水位进行了监测。结果表明，由周期性波动模型确定的冰川湖水位呈现年内波动和年际变化，幅度分别为 0.67 ± 0.09 m，增加速率分别为 0.30 ± 0.05 m/a。 最后，在对 ERA5-Land 气象资料、地形、冰川物质平衡、湖泊面积和水位进行综合分析后，我们可以得出以下结论：（1） 冰川物质平衡主要受气温和降雪的影响;（2）冰川湖面积的变化受湖盆、冰川表面高程和排水事件等因素驱动;（3） 冰川湖水位的年内波动和年际变化都主要受降水和冰川物质平衡的影响;（4） 冰川物质平衡占导致冰川湖体积变化的供水量的 （36.19 ± 8.47）%，而降水量占 （63.81 ± 5.08）%）。冰川物质平衡测量揭示了由于气候变化，天山中部 Ak-Shyirak 地块的模式发生了变化。首次冰期前湖水位测量为年内和年际变化提供了独特的见解，为第三极地区范围的冰川湖监测提供了参考。此外，量化冰川融水对湖泊体积的贡献将有助于未来的冰川湖评估和潜在的溃决洪水影响。