Numerical Simulation of the Hydrodynamics Affected by Coastline and Bathymetry Changes in the Bohai Sea

In order to explore the influence of coastline and bathymetry changes on the ocean hydrodynamic field, the three-dimensional hydrodynamic model of the Bohai Sea under present (2015) and historical (2003) coastline and bathymetry conditions were constructed based on the Delft3D-FLOW model, and the hydrodynamic conditions of the Bohai Sea were simulated accordingly. The simulated tidal wave and tidal residual current were compared andanalyzed, and the influence of coastline and bathymetry changes on the dynamic field of the Bohai Sea was explored. The simulation results showed that the changes of coastline and bathymetry had noticeable impact on the M₂ tidal wave system in the Bohai Sea. After reclamation, the amplitude of the M₂ tide decreased and the amphidromic point near Qinhuangdao shifted to the northwest. The tide-induced Eulerian residual current was affected by the coastline and bathymetry changes. The residual current in the southern of Caofeidian Port exhibited irregular changes, formed complex eddies, and increased in the offshore area. The residual current from the Tianjin Port to the northern coastal area of the Huanghua Port increased by 3—5 cm/s in 2015 compared to that in 2003. A counterclockwise circulation formed in the southern part of Huanghua Port, and the residual current decreased by 2—5 cm/s. As the water depth increased, the residual current decreased by 2—7 cm/s near the Liaohe Estuary of the Liaodong Bay. The counterclockwise current near the Yellow River Estuary moved to the southeast, the residual current in the northern part of the Yellow River Estuary decreased slightly, and the residual current in the southeast significantly increased by up to 9 cm/s. The clockwise circulation on the south of the Diaolongzui decreased, and the clockwise current on the north increased by 4—9 cm/s.