碩士 / 國立中山大學 / 海洋地質及化學研究所 / 101 / It has been known that Kuroshio subsurface waters are the major source of nutrients to the East China Sea continental shelf, a major fishing ground. It has also been known that subsurface waters that upwell onto the shelf are heavily affected by the South China Sea Tropical Water (SCSTW) and the SCS Intermediate Water (SCSIW) which contain more nutrients than the tropical(Smax) and intermediate(Smin) waters from the West Philippine Sea(WPS). A front has been found to separate the tropical and intermediate waters from the SCS and WPS. The reported front in the Okinawa Trough, however, was identified based only on one-time data from a single cross-section. Here historical hydrographicl data between Jan., 1950 and Jan., 2012 from the Luzon Strait to the Okinawa Trough are analyzed.
Compared to the El Niño–Southern Oscillation(ENSO) signals, the data show more clear difference of the salinity in the Luzon Strait between the warm and the cool PDO phases. The salinity of the WPSTW near the Luzon Strait during the warm phase is higher than during the cool phase. The SCSTW mixes with the most WPSTW in all seasons during the warm phase and the least in summer of the cool phase. As for intermediate waters(Smin at sigma theta=26.7-26.9) the WPSIW and SCSIW show much weaker seasonality or ENSO signals compared with tropical waters. On the other hand, the WPSIW penetrates the most westward in the Luzon Strait in spring during the cool phase while at PR18 it is in winter that the WPSIW moves most to the west during the cool phase.
Compared to PDO signals, the data show more seasonal variation in the Okinawa Trough based on ENSO signals. A vertical front tilted toward the west is found in all seasons in all years across the World Ocean Circulation Repeated Lines PR 18 and 19 as well as at a cross-section in the central Okinawa Trough. The front at the Smax level (sigma theta=24.6-24.9) shows large seasonal and interannual variations. In winter during normal and La Nina periods the presence of the SCSTW is the most prominent. It is the weakest in autumn during normal periods, but in spring during La Nina periods. Yet during El Nino periods the SCSTW is the most prominent in spring and it becomes the weakest in winter. As for intermediate waters(Smin at sigma theta=26.7-26.9) the WPSIW and SCSIW show much weaker seasonality compared with tropical waters although during normal periods in winter the WPSIW contribution is larger than during other times. During El Nino periods the WPSIW contribution is the smallest but in spring it is much strengthened. On the other hand, the WPSIW contribution is the smallest in spring, and the largest in winter during the La Nina periods.
| Identifer | oai:union.ndltd.org:TW/101NSYS5271007 |
| Date | January 2013 |
| Creators | Ya-Ting Yeh, 葉雅婷 |
| Contributors | Chen-Tung Arthur Chen, 陳鎮東 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 98 |
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