Thursday 25 August 2005

P3

PTH0126
A salinity front in the southern East China Sea separating the Chinese coastal and Taiwan Strait waters from those of the Kuroshio
Chen, Chen-Tung Arthur¹, Wang, Shu-Lun²
1 National Sun Yat-Sen University, Taiwan
2 National Kaohsiung Marine University, Taiwan
Author email: ctchen@mail.nsysu.edu.tw
It has generally been accepted that waters at essentially all depths across the entire Taiwan Strait flow northward in summer. Evidences are shown here, however, that these waters are confined to the western three-quarters of the northernmost Taiwan Strait, while cooler but more saline Kuroshio subsurface waters which circumvent the northern tip of Taiwan occupy the eastern quarter. The Chinese coastal and Taiwan Strait waters are separated from the Kuroshio waters by a salinity front. In fact, waters are vertically well mixed near the front where surface waters show a clear horizontal salinity maximum but a weak temperature minimum. These compare with bottom waters which show a horizontal salinity minimum but a temperature maximum. Subsurface waters near the front are distinctively warmer but less saline and are lighter and less oxygenated than the waters on either side. These warm, fresh, light, low-oxygen bottom waters are attributed to downwelling of waters from the east which have previously upwelled near the shelf break northeast of Taiwan. These waters can be traced to at least 30¢XN in the East China Sea (ECS) following the 75m isobath. Similarly, water column-integrated nutrients, chlorophyll a and primary productivity also show a horizontal minimum at this isobath. Such an unusual subsurface warm temperature ridge but low salinity trough may be used to define the seaward boundary of coastal and Taiwan Strait waters in the ECS. The salinity maximum at the surface also seems to define the seaward boundary of fresh (S<33) coastal waters.

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