Evaluating Winter Turbulent Heat Fluxes in a Hydrodynamic‐Ice Model of the Great Lakes

Lükő, Gabriella and Anderson, Eric J. and Spence, Christopher and Lenters, John D. and Blanken, Peter D. and Nicholls, Erin and Torma, Péter (2025) Evaluating Winter Turbulent Heat Fluxes in a Hydrodynamic‐Ice Model of the Great Lakes. WATER RESOURCES RESEARCH, 61 (12). ISSN 0043-1397

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Abstract

Turbulent heat fluxes are affected by and influence the temperature dynamics and ice conditions of lakes. Significant efforts have been made to develop operational hydrodynamic and ice models for large lakes such as the North American Great Lakes. However, the behavior of surface fluxes in these lakes has previously focused on the ice‐free season and has not yet been fully assessed during winter conditions in the presence of ice. Given the importance of navigation support and regional weather forecasting, we therefore analyze operational configurations of the Great Lakes for modeled fluxes to evaluate them for open water, ice‐covered, and partial ice conditions. We compare the modeled fluxes with eddy covariance‐based observed fluxes from the Great Lakes Evaporation Network. While observed latent heat fluxes have periods of high values both during ice‐free and ice‐covered periods, we find that elevated open water fluxes in early winter can be well modeled. However, the modeled fluxes during ice‐covered periods appear less accurate, where the errors are likely related to the simulated ice thickness. Thin ice has many small cracks, resulting in large fluxes nearly as high as over open water; very thick ice can reduce the latent fluxes to near zero, according to observations. Overall, the algorithms used in existing operational models show promise in resolving winter lake fluxes; however, further improvement may require adaptations to underlying ice and hydrodynamic model formulations.

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