Journal of Tropical Oceanography ›› 2019, Vol. 38 ›› Issue (4): 1-9.doi: 10.11978/2018128CSTR: 32234.14.2018128

Special Issue: 南海专题

• Marine Hydrography •     Next Articles

Low-frequency variability of subsurface salinity in the South China Sea and its relationship with the Pacific Decadal Oscillation

Xiangpeng WANG1,2,Yuhong ZHANG1,Aimei WANG3,Wei ZHAO4,Yan DU1,2()   

  1. 1. State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
    3. National Marine Data and Information Service, Tianjin 300100, China
    4. College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China;
  • Received:2018-11-26 Revised:2019-02-28 Online:2019-07-20 Published:2019-07-21
  • Supported by:
    This work is supported by the Chinese Academy of Sciences((XDA19060501、XDA13010404););the State Oceanic Administration of China((GASI-IPOV AI-02););and the National Natural Science Foundation of China((41525019、41506019、41805057、41830538))

Abstract:

The South China Sea is the largest marginal sea in the northwestern Pacific and the key channel connecting the North Pacific and northern Indian Ocean. When the Kuroshio flows northward along the Philippine Islands, signals from the western Pacific are transmitted to the South China Sea through the Luzon Strait, thus affecting the hydrodynamic environment of the South China Sea. We analyze the spatial distribution and low-frequency variability of subsurface salinity in the South China Sea, and try to explain the relationship between the subsurface salinity in the South China Sea and the Pacific Decadal Oscillation (PDO); we also explore the change of the subsurface salinity in recent years. The results are as follows. 1) Driven by the subsurface cyclonic circulation, subsurface salinity at about 24-26 σθ decreases gradually from north to south counterclockwise starting from the Luzon Strait. 2) The low-frequency variability of subsurface salinity is significantly correlated with PDO. When the PDO is in the positive phase, the westward transport in the Luzon Strait is strengthened and the subsurface salinity increases. When the PDO is in the negative phase, the westward transport in the Luzon Strait is weakened and the subsurface salinity decreases, and the salinity change is directly affected by the horizontal circulation. 3) In recent years, the subsurface salinity has shown a trend of refreshing from 2006 to early 2014, and then increasing from 2014 to early 2017, lagging behind the PDO by about 10 months. Since 2017, the salinity decreased again.

Key words: subsurface salinity, low frequency variability, Pacific Decadal Oscillation (PDO), advection, South China Sea