Thermal dynamics of proglacial lakes in 1990–2023: A case study of Jiongpu Co, Southeastern Tibet

The temperature of proglacial lakes is a sensitive indicator of glacier‒lake interactions and climate forcing, yet its long-term evolution on the Tibetan Plateau remains poorly constrained. This study focuses on Jiongpu Co, one of the largest and fastest expanding proglacial lakes in southeastern Tibet. Since 1990, it has expanded by 190%, increasing from 1.88 ± 0.03 to 5.32 ± 0.08 km 2 . We integrated multi-temporal Landsat 5 TM/8 TIRS land surface temperature (LST) data from 1990 to 2023, along with Sentinel-2 based thermal downscaling to a 10 m resolution and in-situ lake depth-temperature measurements, to analyze the surface and subsurface thermal dynamics. The results indicate that Jiongpu Co been warming at a rate of 0.086 ± 0.019 °C per year ( p < 0.01). The lake has experienced a net surface warming of 2–3 °C and exhibits distinct thermal phases. Analysis of the centerline temperature profiles and trends revealed a transition from initial subzero, ice-dominated conditions to a stable warming pattern in later stages, mainly driven by glacier dynamics. In-situ profiles indicate stable summer thermal stratification, with surface temperatures ranging from 5.4 to 6.5 °C and deep-water temperatures between 4.0‒4.8 °C. The colder waters near the glacier terminus suggest a continuous influence of subglacial meltwater. Notably, the downscaling approach demonstrates remarkable potential for capturing the fine-scale spatial heterogeneity of lake surface temperatures. Integrating a multi-decadal satellite thermal record with high resolution temperature mapping and in situ depth profiles tightly constrains surface and subsurface thermal coupling in proglacial lakes across both space and time. This improved constraint advances understanding of proglacial lake evolution under ongoing climate warming and supports assessments of accelerated glacier retreat and the heightened risk of glacial lake outburst floods.