Spring Turbidity Distribution on the Shelf Edge Zone in the East China Sea

Abstract

Conductivity-temperature-turbidity surveys were conducted along ten transects from 31.5° to around 27°N across the shelf edge zone in May 1995 (Leg 1; 10-16 May and Leg 2; 19-26 May). During Leg 1 survey, a well-developed turbid layer extended from the shelf to the shelf edge at the central transects located from 28° to 29°N. On the contrary, the development of the turbid layer was significantly weaker at the same locations during Leg 2 survey. At the northern and southern transects, the turbidity was quite low throughout the present survey. During Leg 1 the continental coastal water which had relatively low salinity and high turbidity was observed on the outer shelf, suggesting the coastal water supplies particulate matter to the shelf edge zone. It was also observed that high turbidity in the bottom layer was related to the well-developed mixing layer. On the other hand, during Leg 2, the high turbidity water diminished on the outer shelf while no intrusion of the continental coastal water and well-develped mixing layer was observed in this area. These observation showed the temporal and spatial variability of the turbidity was quite large on the shelf edge zone, suggesting the seaward transport of particles from the shelf is a sporadic event.