Seasonal Thermocline in the Daya Bay and its Influence on the Environmental Factors of Seawater

The thermocline is one of familiar physical phenomena in the ocean, the transitional layer between the mixed layer at the surface and the deep water layer, the definition of which is based on temperature. In the thermocline, the temperature would decrease rapidly from the higher surface temperature to the much colder deep water temperature. The formation of seasonal thermocline in the Daya Bay due to the double effects of the upwelling stream and the rising of surface water temperature. The seasonal thermocline's formation time is about from May to October in the Daya bay, especially obvious between July and September. The hot cooling water from the nuclear power station has a visible influence on the thermocline, which prolongs its duration and enhance its intensity in the sea area in front of power station. The vertical mixing would practically stop when the themocline has formed, which signals the onset of stratification. The stratification can have a great influence on some of the environment factors such as temperature, salinity, DO, COD, BOD5 and nutrients etc., and have an indirect effect on the environment of Daya Bay.