Wave effects on the detachment of low-salinity water from the Changjiang River plume in summer

The detachment of low-salinity water (LSW) from river plume is critical to coastal systems and the inner-shelf biogeochemical process. In this study, the wave effects on the LSW detachment from the Changjiang River plume are explored. Model results show that wave can enhance the vertical mixing, the northward intrusion of inshore branch of the Taiwan Warm Current, and also the double-core upwelling system. The diluted water is thus narrowed and less extended, which accelerates the detachment of LSW. The wave-enhanced vertical mixing will enlarge the core salinity of the isolated LSW when detached; but after that the core salinity is increased by the horizontal advection/diffusion rather than the vertical mixing due to the strong stratification in summer. Waves also affects the trajectory of the isolated LSW, which is moved further northward and travelled more in distance. Five wave-current interaction processes are compared and it is found that the vertical transfer of wave-generated pressure to the mean momentum equation (also known as the form drag) contributes most to the wave-varied river plume and the LSW detachment through enhancing the vertical mixing and the wave-driven flow. The wave dissipation on turbulence weakens the northeastward flow off the Changjiang River estuary, which restrains the diluted water expansion. The current advection and refraction of wave energy contributes most to the enhancement of the double-core upwelling system. Overall, wave is not the key mechanism leading to the occurrence of LSW detachment, but it promotes the detachment and alters the migration of the isolated LSW.