Ekman pumping

Theoretically, the observed SSH seasonal cycle represents the variation in the mean thermocline in the SCS, where the response to Ekman pumping is concerned. The circulation in the NSCS is relatively stable. However, the SSCS circulation has a strong annual variation. One reasonable interpretation is that the seasonal signal in the SSCS is much stronger than that in the NSCS. In winter, there exists a cyclonic vorticity center over both the SSCS and NSCS. 

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