Deep Western Boundary Current in the South China Sea

Chun Zhou,Yuchao Zhu,Qingxuan Yang,Tangdong Qu,Xiaolong Zhao,Wei Zhao,Jiwei Tian

doi:10.1038/s41598-017-09436-2

Abstract

Deep western boundary current (DWBC) was observed for the first time by an array of 6 current meter moorings southeast of the Zhongsha Islands in the South China Sea (SCS) deep basin during the period from August 2012 to January 2014. In the mean, the DWBC in the SCS flows southwestward with core velocity of 2.0 cm/s and a volume transport of 1.65 Sv (1 Sv = 1 × 106 m3/s). Its temporal variability is dominated by intraseasonal fluctuations with period around 90 days. The main axis of the DWBC, characterized by a low temperature core, tends not to shift with the 90-day fluctuation.

Highlights

The South China Sea (SCS) is the largest marginal sea in the northwestern Pacific, with its central basin covering more than 1 × 106 km[2] below 2000 m and a maximum water depth over 5000 m
Considering that the deep western boundary current (DWBC) generally follows the topography, we re-coordinate the current into the cross-section (v′, generally along the isobaths with positive direction pointing to the southwest) and along-section component (u′, perpendicular to v′ with positive pointing offshore to the southeast)
The results presented here are to some extent different with the previous study on the DWBC with potential temperature and salinity of the core being 2.39 °C and 34.625 psu[9], derived from the Generalized Digital Environment Model (GDEM) climatology

Summary

Introduction

The South China Sea (SCS) is the largest marginal sea in the northwestern Pacific, with its central basin covering more than 1 × 106 km[2] below 2000 m and a maximum water depth over 5000 m. As a result of enhanced diapyncal mixing (~10−3 m2/s) in the deep SCS15, 16, the NPDW upwells and exits the SCS in the upper and intermediate layers[4, 17,18,19,20,21]. This three dimensional circulation constitutes the South China Sea Throughflow, serving as a heat and freshwater conveyor that is believed to be climatologically important both regionally and globally[20, 22,23,24].

Methods

Results

Conclusion