A Small Temperate Lake in the 21st Century: Dynamics of Water Temperature, Ice Phenology, Dissolved Oxygen, and Chlorophyll a

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AbstractIt is unclear how small temperate lakes will evolve physically and biologically in the whole water column under future climate because previous modeling studies usually focused on only one or two physical or biological state variables in the surface waters. Here we used a well‐validated lake biogeochemistry model driven by different climate scenarios of the 21st century to predict the dynamics of ice phenology, water temperature, dissolved oxygen (DO), and chlorophyll a in a small Canadian temperate lake (0.714 km2) that is oligotrophic and strongly stratified in summer, considering the influence of catchment hydrology. The ice season and thickness of the lake are projected to shrink substantially under warming, resulting in a positive energy feedback between climate and the lake. Due to the reduced heat diffusion and water mixing, the dynamics of water temperature in surface and deep waters of the lake are considerably different, with surface waters warmed dramatically but deep waters muted to warming. DO depletion is predicted to occur in the whole water column of the lake under warming, but the controlling processes are depth dependent. Unexpectedly, the predicted growth of the lake's chlorophyll a is small under warming, due to the weakened convection and the mismatch of the timings of favorable solar radiation, thermal, and nutrient conditions. For the examined state variables, our prediction shows that only the dynamics of DO is significantly impacted by the changing catchment hydrology. This study suggests that similar temperate lakes will have diverse physical and biological responses to climate change.