South China Sea Isopycnal-Surface Circulation

Peter C. Chu Department of Oceanography, Naval Postgraduate School, Monterey, California

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Rongfeng Li LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

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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 ½° × ½° 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 anticylonic 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 Csanady 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 value 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).

Corresponding author address: Dr. Peter Chu, Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943.

chu@nps.navy.mil

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 ½° × ½° 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 anticylonic 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 Csanady 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 value 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).

Corresponding author address: Dr. Peter Chu, Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943.

chu@nps.navy.mil

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