Observation Of Turbulent Mixing In The Continental Shelf Sea East Of Hainan Island

Turbulent mixing is one of the most important processes in the ocean and it is crucial for the exchange of matter and the transport of energy. The shelf sea is vital for the survival and development of humans, where the complex topography and abundant dynamic processes are important factors to control and influence the turbulent mixing. Based on the in-situ hydrographic and microstructure observations conducted in February and July 2012, this study reveals the spatial distribution characteristics and seasonal variation characteristics of the mixing in the continental shelf sea east of Hainan Island. Three previous parameterization models for mixing are tested in the observation area and new model is further proposed.There is obvious seasonal variation characteristic for mixing in the continental shelf sea east of Hainan Island by analyzing the observational data. The mixing is very weak in summer in the continental shelf sea east of Hainan Island. And average values of the turbulent kinetic dissipation rate and the diffusion coefficient are 1 ×10-9 -1 and 1 × 10-62 -1. Both of them are lower than the background values of oceans. But the mixing is stronger in winter than in summer. And average values of the turbulent kinetic dissipation rate and the diffusion coefficient are 1 ×10-8 -1 and 1 × 10-42 -1. The stratification is the vital factor for controlling and influencing the mixing in the continental shelf sea east of Hainan Island. The average values of stratification(N2) are 3.2 × 10-4 -2 in summer and 3.2 × 10-5 -2 in winter. The summer upwelling in the continental shelf sea east of Hainan Island upward the isopycnals and strengthens the coastal stratification.Three parameterization models of Gregg 1989(G89), Kunze 1990(K90) and MacKinnon and Gregg 2003(MG03) are tested to simulate the mixing in the continental shelf sea east of Hainan Island. The results of G89 and K90 are obviously deviated from the observation with values more than ten times larger, while the MG03 is relatively closer to the observation. In addition, the difference between the simulate result and the observation in winter is smaller than that in summer, indicating that the upwelling in summer affects much more on the mixing east off Hainan Island. From the summer observation, we propose a new parameterization model as ε =10-6.3344? 1.103? 0.3008 for the mixing in the continental shelf sea east of Hainan Island in summer. More works on the dynamics and the parameterization of the mixing in the continental shelf sea east of Hainan Island are further needed.