Thermodynamics and its drivers of Mang Co: A high-altitude freshwater lake in the southeastern Tibetan Plateau

Mang Co, a dimictic freshwater lake in the southeastern Tibetan Plateau (TP) influenced by the summer monsoon, lies within the Jinsha River catchment. The region experiences warm, humid summers and cold, dry winters. Using a three-year (2019–2022) high-resolution (30-min interval) vertical water temperature dataset, we investigated Mang Co’s seasonal thermal stratification and mixing dynamics, and compared controlling mechanisms with those of arid mid-western TP lakes. Mang Co exhibits monsoon-driven humidity amplification (annual mean up to 60 %), which suppresses evaporative cooling and maintains hypolimnetic temperatures up to ∼10 °C—significantly warmer than those in mid-western TP lakes where the climate is drier. Stratification develops from late May to early October, followed by spring and autumn overturning and ∼4 months of winter ice cover with inverse stratification, and post-melt convection. Episodic spring wind gusts (>10 m·s⁻¹) drive mixing. Summer stratification is mainly stabilized by air temperature and humidity–radiation synergy, unlike arid lakes where wind and solar radiation dominate. Due to Mang Co’s shallow depth and low salinity, the thermocline is shallower (∼10 m) and Schmidt stability lower (max ∼194 J·m⁻²) than in deeper saline lakes. These findings highlight divergent thermal structures shaped by humidity, wind events, and ice–water interactions. They underscore the importance of incorporating humidity thresholds and episodic wind forcing into lake models for accurately simulating monsoon-affected high-altitude lakes under climate change. • Presented 3-year high-resolution thermal profiles from Mang Co, SE Tibetan Plateau. • Identified monsoon-driven stratification stabilized by humidity and air temperature. • High humidity suppresses hypolimnetic cooling. • Stratification dynamics differ from arid lakes due to local climate and lake features.