Dynamics of the extension of the Yellow River plume in the Bohai Sea

The Yellow River is one of the largest rivers in China, and its river plume has significant influences on the physical and ecological environment and fishery resources in the adjacent sea. However, how the Yellow River plume extends and its dynamic mechanism remain unclear. A 3D numerical model was used to study the dynamics of the extension of the Yellow River plume in summer. The results of the numerical experiments show that the river plume has an unrealistic upstream extension in the absence of tidal forcing. Tidal forcing plays a key role in arresting the river plume upstream extension and creates the majority of the river plume that spreads downstream along the west coast of Laizhou Bay and a small part of the river plume that extends northeastward. Sea surface heat enhances the pycnocline, resulting in the river plume spreading further eastward offshore, and the downstream and upstream residual currents and low-salinity water along the coast retreat to the river mouth at the surface. The southerly wind plays a key role in the far northeastward extension of the Yellow River plume. The detachment of the low-salinity water in the river plume during spring tide is induced by tide-induced vertical mixing and not by the southerly wind. Numerically sensitive experiments indicate that the magnitudes of the river discharge and southerly wind speed have considerable effects on the extension of the Yellow River plume. The revealed dynamics of the extension of the Yellow River plume are fundamental to better understand the physical and ecological processes and protect fishery resources.