Lake Heatwaves and the Driving Mechanism in US Lakes

Lake heatwaves (LHWs) pose a growing threat to freshwater ecosystems, yet the drivers of these short-term extremes versus long-term warming are often conflated. This study aims to disentangle these mechanisms for US lakes. We analyzed daily surface temperature data from 43 representative US lakes (1980–2020), combining Mann–Kendall trend analysis, Sen’s slope estimation, and Random Forest attribution modeling. Results reveal a significant overall warming trend of 0.14 °C/decade, a pattern primarily driven by lakes outside the Western Cordillera region. Concurrently, LHWs intensified in frequency, duration, and cumulative intensity, occurring most frequently in summer but with the greatest intensity in spring. Crucially, the attribution analysis identified distinct controlling mechanisms: short-term LHWs were predominantly governed by meteorological factors (57.3% contribution), whereas long-term warming trends were modulated by geographical factors (47.5% contribution) that dictate the lake’s thermal sensitivity. These findings establish that lakes respond differently to short-term weather extremes versus long-term climate shifts. This distinction is critical for developing more accurate meteorologically based LHW forecasts and tailored, region-specific ecosystem management.