| Summary: | The thermal dynamics of lakes are affected by climate change, and in turn affect most aspects of lake ecology, including primary and secondary production, biogeochemistry, and biodiversity. These effects may be particularly large in polymictic lakes which have variable durations and degrees of thermal stratification. A one-dimensional model, the Dynamic Reservoir Simulation Model (DYRESM), was used to evaluate the impacts of predicted climate change on temperature and stability in Oneida Lake, a 207km2 shallow, polymictic lake in central New York State. Field data were collected on stream temperature and discharge, weather, and lake temperatures at varying depths to calibrate and validate the model for Oneida Lake. Modeled temperatures at 2m and 10m were generally within ±1°C of observed values, but only after wind speeds from a nearby airport were decreased by 25%. Downscaled climate data from three general circulation models and two emissions scenarios were used to assess the impacts of different anticipated climate scenarios on the lake for 2041–2050 and 2090–2099. By 2050, under the higher emissions scenario, water temperatures (April–November) at 2m and 10m depths indicated an increase of 1.36°C and 1.43°C, respectively; however, 2011 simulation temperatures already aligned with mid-century predictions. By the end of the century, the prediction of the higher emissions scenario indicated an increase in 2m and 10m water temperatures (April–November) of 3.70°C and 3.37°C, respectively, and an increase of 61 consecutive days of stratification in Oneida Lake. These impacts would lead to increased periods of lack of oxygen in the bottom waters of this lake and changes in the biotic species composition, including extirpation of a coldwater fish species, burbot (Lota lota). This study contributes to our understanding of the thermal regime of polymictic lakes in a warmer world. Aquatic ecosystem; Calibration; Hydrodynamic; Lake mixing; Physical limnology; Validation;
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