Three-dimensional Structure Of The Summer Circulation In Southwestern Yellow Sea And Its Control Mechanism

The southwest Yellow Sea, which abuts Chinese mainland, is rich in fisheries and biological resources, while, enteromorpha events have been served as wake-up calls since 2007. It is thus very significant for us to study the hydrological structure and circulation pattern of the southwest Yellow Sea, which may have instructive effects on ecological presentiment and marine fishery activities.This study firstly explores the three-dimensional structure of the summer circulation in southwest Yellow Sea with the help of the temperature and velocity data from ROMS. The results show that the north current, mainly located near Jiansu Province, is highly affected by the coastal wind, and its width and flux present decreasing trends when the latitudes are increasing. The feature of the vertical distribution in meridional velocity field is that the whole surface currents are northward, shallow and thin from June to August, while almost the whole layers are southward currents in September. Besides, the nuclear direction of the northward current is northward in spring and summer, but opposite in autumn and winter, and that of the southward current is nearly southward all the year round.Secondly, the influence factors of the circulation in the southwestern yellow sea are discussed in this paper. We analyzed the generating and vanishing process of cold water mass in the South Yellow Sea, and the seasonal variations of Eddy Kinetic Energy (EKE) and related mechanism by calculating the kinetic energy flux spectrum. The main conclusions as follows:the South Yellow Sea Cold Water Mass is a seasonal water mass, appearing in spring, peak period is in summer, weakening in autumn, disappearing entirely in winter. The cold water mass which is located in the east side of the South Yellow Sea is relatively more stable and deeper. The cold water mass on the west bank is shorter and shallower. The left branch of cold water mass circulation in Yellow Sea play a very important role on strength and structure of the northward flow.We found that EKE had a double-peak structure on seasonal scales in that region, with peaks appeared respectively in September (stronger one) and January (weaker one). Furthermore, the eddies were found more meridionally elongated in the first half year while zonally elongated in the later half year. The EKE spectral characters showed that the EKE peak in September were mainly due to the baroclinic instabilities in summer time while the another peak in January may be the results of eddy-eddy interactions.