Seasonal and intraseasonal thermocline variability in the Central South China Sea

Seasonal and intraseasonal variability of thermocline and relative surface height in the central South China Sea (SCS) are investigated using time ser ies data of temperature from three buoys and sea surface height anomaly dat a from TOPEX/POSEIDON and ERS-1/ERS-2 satellites (T/P-ERS) from Feb. 1998 t hrough Mar. 1999. We found that the thermocline becomes deeper and thinner in winter, owing to a great loss of the heat on the sea surface. This featu re is more evident in the northern than the southern part of the central SC S. The intraseasonal variation of the thermocline is mainly controlled by t he geostrophic vorticity and is out-of-phase with sea surface height (SSH). Furthermore, we find a double-thermocline phenomenon occurs in the SCS: In spring, owing to maximum net downward heat flux at the surface, with the n ew thermocline appearing above 80 m and the old thermocline keeping under 8 0 m deep.