Decadal Variation of the Kuroshio Intrusion Into the South China Sea During 1992–2016

• Published in: Journal of geophysical research. Oceans 2020-01, Vol.125 (1), p.n/a
• Main Authors: Chen, Yicheng, Zhai, Fangguo, Li, Peiliang
• Format: Article
• Language: English
• Subjects: Anomalies; Circulation anomalies; Cyclonic winds; decadal variation; Decadal variations; Geophysics; Height; Height anomalies; Intrusion; Kelvin waves; Kuroshio intrusion into the South China Sea; Kuroshio transport; large-scale wind forcing; Local winds; Long-term changes; Ocean circulation; Ocean currents; Ocean models; Oceans; Oscillations; Planetary waves; Rossby waves; Sea surface; sea surface height anomaly; Straits; the Philippines-Taiwan Oscillation; Transport; Tropical climate; Upwelling; Variation; Wind; Wind effects; Wind stress; Wind stress curl
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2019JC015699

Decadal variation of the Kuroshio intrusion into the South China Sea (KIS) during 1992–2016 is investigated using high‐resolution Hybrid Coordinate Ocean Model reanalysis data. The results indicate that both the yearly occurrence frequency of the Kuroshio intrusion and Luzon Strait transport show significant decadal variations and were generally high in approximately 1993, 2003–2004, and 2015–2016 and low in 1998–1999 and 2009–2010. The KIS is closely connected to the decadal oscillation of the meridional sea surface height anomaly (SSHA) gradient west of the Luzon Strait (LS). Further analyses reveal that large‐scale wind forcing in the western tropical Pacific Ocean is a major factor regulating decadal variation of the KIS, while local wind forcing has little impact. Cyclonic wind stress curl anomalies (WSCAs) over the western tropical Pacific Ocean induce negative SSHAs that propagate westward to the eastern coast of the Philippines via upwelling Rossby waves, weakening the Kuroshio transport and consequently enhancing the KIS. In addition, signals of negative SSHAs can propagate clockwise along the Philippines as coastal Kelvin waves and hence strengthen the northward SSHA gradient west of the LS, eventually leading to a stronger KIS. The situation is reversed when anticyclonic WSCAs prevail in the western tropical Pacific Ocean. The Philippines‐Taiwan Oscillation is linked to decadal WSCAs over the western tropical Pacific Ocean and hence regulates the decadal KIS. Plain Language Summary The Kuroshio intrusion into the South China Sea (SCS) is important to the variations of the circulation and climate in the SCS. Due to the lack of long‐term observations, there is still debate regarding the characteristics and mechanisms of its long‐term variability. In this study, decadal variation of the Kuroshio intrusion into the SCS during the period 1992–2016 is investigated based on the Hybrid Coordinate Ocean Model reanalysis. The results show that decadal oscillations of the circulation and salinity in the northern SCS are regulated by the Kuroshio intrusion. Large‐scale wind forcing over the tropical Pacific is a key factor modulating the decadal Kuroshio intrusion by affecting the circulation anomalies east of the Philippines and sea surface height west of the Luzon Strait, whereas the effects of local wind forcing are insignificant. Key Points The KIS during 1992–2016 shows significant decadal variation The meridional SSHA gradient west of the LS exhibits