The South China Sea thermohaline structure and circulation

Abstract

The minimum curvature with spline method was used to establish a three-dimensional monthly-varying gridded data from the Navy's Master Oceanographic Observation Data Set (approximate 189,000 profiles), covering the area of 5 deg N - 25 deg N and 105 deg E - 125 deg E and from the surface to 400 m depth. For temperature, profiles were binned into 204 monthly data sets from 1968 to 1984 (17 years). Because of the paucity of salinity data, salinity profiles were binned into 12 climatological monthly data sets, and the monthly climatological mean was computed. After the gridded data set had been established, both composite analysis and the Empirical Orthogonal Function (EOF) analysis were used to identity the major thermohaline features. The first EOF mode accounts for 26.7% of the variance and represents the seasonal variation. The second EOF mode accounts for 17.7% of the variance and represents the interannual SCS warning/cooling phases. Furthermore, the P-vector method was used to invert three-dimensional velocity fields from the analyzed temperature and salinity data. Important dynamical processes, including th Kuroshio intrusion, the western boundary current (counter-current), the cross basin current (undercounter-current), the mesoscale eddies, and the basin gyre are identified.