South China Sea isopycnal-surface circulations

Abstract

This paper investigates the seasonal variabilities of the South China Sea isopycnal-surface circulations and of the Kuroshio intrusion through the Luzon Strait using the U.S. Navy’s climatological temperature and salinity dataset (public domain) with 1/2 degrees X 1/2 degrees resolution by the P-vector method. The representative pattern is a persistent basin-scale cyclonic circulation away from the surface, and a seasonally varying circulation with a weak anti-cylonic gyre in the summer and a strong cyclonic gyre in the winter near the surface. This pattern is consistent with a classical view of mean cyclonic circulation in large stratified lakes and semienclosed marginal seas by Emery and Csaanady and with a recent numerical simulation using the navy's Layered Ocean model by Metzger and Hurlburt. The computed monthly volume transport through the Luzon Strait is negative (inflow) all year round with a minimum vlue of 13.7 Sv in February (strongest intrusion) and a maximum value of - 1.4 Sv in September (weakest intrusion). The annual mean transport is - 6.5 Sv (intrusion).