| Chinese scientists have conducted many studies on the radial circulations of the Northern Yellow Sea Cold Water Mass (NYSCWM). Early researchers (Guan, 1962; Yuan, 1979: Miao, 1989) thought that notable upwelling appears in the central part of the NYSCWM and downwelling near its boundary areas. But these cannot explain why the dissolved oxygen maximum near the bottom of the thermocline, and T S characteristics in the central part of the cold water mass remain unvarying for long time. Yuan and Li (1993)’s solution of Yuan (1979)'s mathematical model was bassed on the assumption of a very level isotherm and omitted the ?T / ?r term. In fact, because of the existence of a tidal front, ?T / ?r becomes very large (maximum) in the boundary areas of the NYSCWMJ So the ?T / ?r term should not be disregarded as negligible.
We started to study tidal mixing and tidal fronts in the Yellow Sea in 1985 and pointed out that upwelling in the NYSCWM’ s boundary areas is more noticeable than that at its centre. To clarify the NYSCWM’ s circulations characteristics a diagnostic model of tidal front was used to find a numerical solution, which showed mainly circular currents in the upper layer near the NYSCWM boundary, Radial movement of off-shore currents in the upper layer, shoreward currents in the lower layer, the strong upwelling in boundary areas, very weak upwelling in the NYSCWM's upper layer only, and a pound of stagnant water under the thermocline. The above circulation structure of the NYSCWM keeps the dissolved oxygen maximum near the bottom of the thermocline and stabilizes the T S property of the NYSCWM. Measured currtny data and satellite pictures were used to verify the above circulation pattern and show that the Ekman pumping by inner friction of stratified fluid at the thennocline is the main driving force for above the radial circulations. |
