Seasonal Structure And Variation Of The Circulation In The Southern South China Sea

In situ hydrographic data of 12 oceanographic cruises of the southern South China Sea (SSCS) since 1 980s, together with satellite remote sensing data, have been collected and processed. With these multi-source data sets and by using the dynamic calculation method, the structure and variation of the SSCS circulation are systematically analyzed. The basic distributing features of the upper (O-500m) and lower (500-l000m) circulation in the stable periods of the NE and SW monsoons and the evolution processes of the circulation during the monsoon transitions are studied. The features of the year-round multi-eddy structures are revealed and the forcing of wind stress curl and topographic effect are suggested to be the major mechanisms of the SSCS upper circulation. For the first time, the northward counter-wind current crossing the southern continental slope in winter and the eastward off-shore current at the northwest part of the SSCS in summer are proposed and their dynamic mechanism are discussed. The fronts in the SSCS are studied, showing that there exist two type of oceanic fronts梥ummer front at the north-part and winter front over southwest continental shelf-break. Salinity-reversing anomaly water was found for the first time at surface layer in the period of spring-to-summer transition. Several factors, such as the westward intrusion of the Sulu Sea high temperature and salinity water, the strong sea surface evaporation as well as the weak vertical mixing, are the major formation mechanism.