| Based on the data of four-season investigation in the Northern Yellow Sea and the Southern Yellow Sea from July, 2006 to October 2007, the distribution characteristics and seasonal variation of chemical elements are studied in the entire Yellow Sea, such as temperature, salinity and biogenic elements. The Yellow Sea Cold Water Mass (YSCWM) is divided into two parts based on temperature, salinity and biogenic elements. The main conclusions are as follows:(1) Horizontal distribution: In winter, the distribution of hydrological and chemical elements (except dissolved oxygen) is high in the central Yellow Sea but low in the inshore areas. Distribution of dissolved oxygen was contrast, it reflected the impact of the Yellow Sea Warm Current; in spring, the distribution could be divided into two types, in the upper layer and 30-meter layer there are minimal nutrients and maximum dissolved oxygen in the central area, while in the bottom layer it is contrast. In the Southern Yellow Sea, the distribution of the upper layer is similar with the North Yellow Sea,while the other layers are the same as winter. The distribution of chemical elements in summer and autumn is similar, the concentration is low in central, high in surrounding in the surface layer, 30m and the bottom layer are covered by the YSCWM. They are characterized by low temperature, high salinity, low dissolved oxygen and high nutrients. The difference between two seasons is that the coverage of YSCWM reduced.(2) Vertical distribution: In winter, all the elements of the two vertical section are generally mixed uniformly; in spring, the Northern Yellow Sea appeared clear stratification, dissolved oxygen and pH is high in the upper water, nutrients is contrast, in the Southern Yellow Sea, the stratification is very weak; in summer, the entire Yellow Sea appeared strong temperature and salinity thermocline, the vertical water is divided into three layers, the upper mixed layer - thermocline - the lower mixed layer. There is maximum concentration of dissolved oxygen next to the thermocline in the South Yellow Sea. The value of nutrients in the water below thermocline are accumulated while the nutrients are almost exhausted in the remaining water; in autumn, the thermocline is sinked to the lower layer, the YSCWM existed in the Yellow Sea trough, there is very weak stratification in the Northern Yellow Sea, but stratification remained in the Southern Yellow Sea, the value of nutrients in the water below thermocline were further accumulated.(3) Seasonal variation: Nutrient concentration in the upper water (less than 30) is the highest in winter, followed by autumn, the third in spring, and the minimum in summer, which is due to the uptake by phytoplankton. Dissolved oxygen is high in winter and spring, low in summer and autumn, which is the result by water temperature and biological activity. Nutrient concentration in the lower water (deeper than 30 m) is the highest in autumn, followed by winter, the third in summer, and the minimum in spring, but the dissolved oxygen is contrast, it showed that organic maters was consumed while the nutrients were regenerated.(4) By cluster analysis and T-S diagram, the YSCWM can be divided into North YSCWM and South YSCWM, their border is not the geographical boundary. In summer, the South YSCWM is characterized by the salinity at 33.23, temperature at 8.91°C ,while the North YSCWM's temperature is 7.55°C and salinity is 32.05. In autumn, the North YSCWM and South YSCWM is separated in the salinity of 32.5. Through the comparison of chemical elements between them, it showed that the distribution of the elements in the North YSCWM is uniform, while the range of elements in the South YSCWM was very large. Compared with the south YSCWM, North YSCWM is characterized by the features of low temperature, low salt, high oxygen, low pH, low suspended particulate matter, low silicate and low dissolved inorganic nitrogen.
|
PDF Full Text Request