Study on the evaluation of the influences of the Three Gorges Dam construction in China on the marine environment in the East China and Japan Seas

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The behavior of the Changjiang Diluted Water(CDW) was observed by satellite-tracking drifters with T/S sensors deployed in the mid-shelf area during the summer of 2003 and 2004. Both of the seasonal variations in the CDW shown by climatology and the daily variations detected by drifters are reproduced by numerical models. The numerical models indicated that the behavior of the CDW is strongly influenced by wind stress both in seasonal and daily variations. Comparison of the movements of drifters with daily wind stress also shows the significant wind effect on the movement of CDW.The horizontal distribution of the CDW is often compared with that of ocean color detected from satellites. The nutrients consumed by phytoplankton should be supplied into the CDW. Estimation of the vertical eddy diffusivity with measurements of the microstructure in the CDW area and salinity change from the Lagrangian measurements suggested that vertical advection could play a significant role on the increase … More in salinity in the CDW. The magnitude of the vertical velocity estimated is roughly coincident with that calculated from the divergence of drifters' dispersion.Water mass analysis using nutrients along with temperature and salinity revealed that water at the lower layer on the shelf could be a mixture of the Kuroshio thermocline water and the fresh water with a small fraction. The distribution of oxygen-18 isotope ratio suggests that the Kuroshio intermediate water would intermittently intrude into the bottom layer of the continental shelf.The monitoring of salinity by the regular ferry, Camellia line, crossing the Tsushima Strait showed that the western channel of the strait is usually much influenced by the low salinity water compared with the eastern channel. However, the interannual variations in salinity in the eastern channel are larger than those in the western channel. The variations appear to be related to the variation in the volume transport of Changjiang discharge.The spectral analyses for the mooring data in the deep layer in the Japan Sea revealed that inertial internal gravity waves would play a significant role on the vertical mixing in the deep water. Less