Numerical Study On Tidal Mixing In The Bohai Sea

Barotropic tides flow over rough topography,barotropic tidal energy is transformed into baroclinic in the form of internal waves.Part of these waves dissipate locally where they generated,creating locally enhanced turbulent mixing called tidal mixing.Tidal mixing is the main energy source of mixing in the ocean,with the exchange of matter,momentum and energy of seawater,has an important influence on the physical and chemical properties of seawater.Better understanding of tidal mixing will be helpful to explore the ocean.The spatial and temporal variability of tidal mixing in summer and winter in Bohai Sea is studied using POM.The results show that the tidal mixing in Bohai Sea is very strong,without obviously seasonal difference.Tidal mixing in Bohai Bay,Liaodong Bay and Bohai Strait is quite strong,the values reach the magnitude of 10^-3m²s^-1,which is two orders of magnitude higher than the background level.The mixing in the central sea area is weakest,the magnitude of mixing values is about 10^-410^-5m²s^-1.The vertical stratification of tidal mixing in Bohai Sea is insignificant,generally renders a barotropic structure.The tidal mixing estimated in Bohai Sea fluctuates considerably within a single day,with the peak value of O(10^-2)m²s^-1.Result also shows that rough topography plays a more important role than tidal current in tidal mixing in Bohai Sea.The influence of tidal mixing on the hydrological environment in Bohai Sea is explored.It is found that the variations of temperature and salinity in summer and winter are not directly related to the values of tidal mixing,mainly depending on the vertical structure.The strong tidal mixing in Bohai Sea has an insignificant effect on the circulation.This paper also explores the distribution characteristics of the tidal mixing under typhoon and the response of the hydrological environment to the tidal mixing in Bohai Sea.Generally,the tidal mixing of Bohai Sea under typhoon is significantly greater than that of normal weather.The variation of seawater temperature and salinity is similar to that of normal weather.In the case of typhoon,wind is the main factor that domains the circulation of Bohai Sea.