Observations of Kuroshio intrusion into the South China Sea

• Published in: Chinese journal of oceanology and limnology Vol. 28; no. 5; pp. 1012 - 1020
• Main Author: 刘泽 侯一筠 齐鹏 胡珀
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science Press 01.09.2010; Springer Nature B.V
• Subjects: ADCP; Buoyancy; Data collection; Deep layer; Direction; Earth and Environmental Science; Earth Sciences; Empirical analysis; High temperature; Intrusion; Marine; Oceanography; Salinity; Salinity effects; Sea; Seasonal variation; Straits; Stratification; Vertical mixing; Water flow; 北太平洋; 南中国海; 南海东北部; 数据显示; 黑潮入侵; South China Sea; ISEW, Pacific, Luzon Strait; ISEW, South China Sea; INW, Pacific, Kuroshio Current; IN, North Pacific; SCS water; Kuroshio intrusion; moored ADCP data; CTD survey; evolution period
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-010-9065-7

To discuss the intrusion of the Kuroshio into the SCS, we examined the mixing between the North Pacific and South China Sea （SCS） waters based on in-situ CTD data collected in August and September 2008 and the moored ADCP data taken from mid September 2008 to early July 2009. The CTD survey included four meridional sections from 119°E to 122°E around the Luzon Strait, during which pressure, temperature, and salinity were measured. The CTD data show that the isopycnal surface tilted from the SCS to the North Pacific; and it was steeper in the lower layers than in the upper ones. Meanwhile, we found strong vertical mixing taken place in the areas near 121°E. The Kuroshio in high temperature and salinity intruded westward through Luzon Strait. The frequency of buoyancy was one order of magnitude greater than that of the common ones in the ocean, suggesting stronger stratification in the northeastern SCS. On the other hand, the long-term ADCP data show that before late October 2008, the direction of water flow in the SCS was eastward, and from November 2008 to late February 2009, it turned northwestward in the layers shallower than 150 m, while remained unchanged in deep layers from 200 to 450 m. From March to June 2009, the direction shifted with increasing depth from northward to southward, akin to the Ekman spiral, EOF analysis of the current time series revealed dominant empirical modes： the first mode corresponded to the mean current and showed that the Kuroshio intrusion occurred in the upper layers only from late December to early March. The temporal coefficient of the first and the second mode indicated clearly a dominant signal in a quasi-seasonal cycle.