Evaluating sea ice influence on water exchange dynamics through three-dimensional hydrodynamic simulation in a semi-closed shallow sea

To understand the capacity of water exchange of semi-closed nearshore shallow waters during winter, this study investigates the effect of sea ice on water exchange dynamics under extreme cold wave conditions by developing a coupled three-dimensional simulation tool and taking the Bohai Sea as a case study. This coupling model integrates the hydrodynamic model, wave model, sea ice model, and Lagrangian particle tracking model. The results demonstrate that sea ice inhibits water exchange in the northern Liaodong Bay due to a clockwise residual circulation. Conversely, sea ice enhances water exchange in the southwestern areas, specifically Bohai Bay and Laizhou Bay. This conclusion is supported by further calculations and analyses of half-life time and volumetric flow rate. Considering the impact of adjacent bays, the percentage of residual particles in the southern area after simulating a severe ice period is 33.5% higher compared to scenarios without this consideration. Finally, the uncertainty of the model was evaluated by altering the quantity of tracer particles, and the validity of the model results was confirmed through comparisons with measured chlorophyll-a and dissolved inorganic nitrogen concentrations. These findings are significant for management departments to develop effective strategies for pollutant prevention and control.