The intrusion of water masses into the sea southwest of Taiwan

Abstract

Characteristics of water masses were analyzed to study the Kuroshio intrusion into the sea southwest of Taiwan. Hydrographic data were obtained from CTD (conductivity, temperature, and depth) casts during two cruises in May and August 1986. In May, remnants of water intruding from the Kuroshio were found on the continental slope south of the Penghu Channel. By August, these were replaced by water from the South China Sea. During this period, water from the Kuroshio also appeared near the southern tip of Taiwan. The intrusion current reached a depth of at least 500 m and was probably part of a cyclonic circulation in the northern South China Sea. The results support the hypothesis of a seasonal pattern of the intrusion process: intrusion of water from the Kuroshio begins in late sununer, intensifies in winter, and ceases by late spring when South China Sea waters again enter this region. of Luzon and Taiwan [Nitani, 1972]. However, the Luzon Strait with its deepest sill at 2500 m forms a gap in the western boundary (Figure 1). Similar to the Loop Current in the Gulf of Mexico between the Straits of Yucatan and the Straits of Florida, the Kuroshio front has been known to enter the Luzon Strait [Nitani, 1972]. Furthermore, water from the Kuroshio may reach the sea southwest of Taiwan [Fan and Yu, 1981; Fan, 1982]. Since the Luzon Strait is the only deep passage of the South China Sea, the intrusion of water from the Kuroshio is important to the salt budget in the basin. Furthermore, the process is of importance to the circulation in the northern South China Sea. A description of the phenomenon is essential to future dynamic studies of the intrusion process. The intrusion of waters from the Kuroshio to the sea southwest of Taiwan has been studied for more than 20 years. Early ship drift data showed that there is a branch of the Kuroshio in the northern South China Sea in winter but not in sununer [see Nitani, 1972]. Some authors believed that a branch of the Kuroshio flows through the shallow Taiwan Strait to the East China Sea [see Wang and Chern, 1987b]. Hydrographic surveys showed that the saline water from the Pacific Ocean enters the Luzon Strait in the upper 150 m in winter [Fan and Yu, 1981; Fan, 1982] but is replaced by waters from the South China Sea in summer [Fan, 1984]. These hydrographic studies demonstrated the existence of the intrusion water in the South China Sea. However, the distribution of the intrusion water has not been examined. Also little is known about the circulation in the northern South China Sea. The objectives of this study are to describe the distribution of the intrusion water from the Kuroshio and to infer the path of intrusion. Data from closely spaced CTD (conductivity, temperature, and depth) stations were examined to study the distribution of various water masses. A preliminary study of this data set showed the presence of water from the Kuroshio off the southwest coast of Taiwan [Li, 1987]. Water characteristics will be further examined in detail in this paper. The results show ...

Internal Solitons in the Northeastern South China Sea Part I: Sources and Deep Water Propagation

“…Numerical models [10] produce an intrusion in the winter but not in the summer. Observations are sparse but also show greater incursions of Kuroshio water during winter than summer [11]. The nature of the KI within the SCS is also variable.…”

Distribution of Thaliacea in SW Taiwan coastal water in 1997, with special reference to Doliolum denticulatum, Thalia democratica and T. orientalis

“…The area under study in this paper has been the subject of many oceanographic studies, both physical (Wang & Chern 1987, Shaw 1989, Hung & Shy 1995, Tseng 2002) and biological (Fong et al 1990, Soong & Chen 1991, Mok & Kuo 2001, including zooplankton studies (Lo et al 2001, 2004, Hwang & Lo 2002, but no attention has been paid to pelagic tunicates. We initiated a project to observe such tunicates, which may play an important role in the ecosystem, with the objective of understanding the seasonal variation in species compositions and life stages of Thaliacea in the study area, and to elucidate the relationship between their patterns of vertical migration and hydrographical conditions.…”

Toward establishing a maritime proxy record of the East Asian summer monsoons for the late Quaternary

“…Summer sea-surface salinities range between 32.8 and 33.6x, but the north^south gradient in salinity in the SCS increases during the winter with a branch of warm, saline Kuroshio enters into the SCS through the Luzon Strait (Shaw, 1989(Shaw, , 1991, mixing with colder waters from the north via the Taiwan Strait. These two surface water masses combine and £ow southward along the coast of Indochina Peninsula and result in a counterclockwise circulation.…”