In the present study we use Argo float data, in-situ shipboard ADCP data,IFREMER wind stress curl data, QuikSCAT wind data and AVISO sea level anomaly data from 2006 to 2010 to investigate hydrographical characteristics and surface and deep currents in the seas surrounding Taiwan. The studied areas consist of the followings: the cyclonic eddy off the northeastern Taiwan coast, flow structure of the Luzon Strait, anticyclonic eddies off the southwestern Taiwan coast and east of Kuroshio.
Our results found that some Argo floats drifting northward with the Kuroshio were occasionally intruded to the continental shelf off the northeastern Taiwan at 25¢XN-26¢XN,122¢XE-123¢XE. Statistics indicate that this phenomenon occurs most frequently in winter, and float profiling data reveal a marked upwelling above 150m depth. Temperature drops within this area can reach 5.1¢J and 8¢J, respectively at 50m and 100m depths. A deep southward current with a maximum speed of 30 cms can be found to exist between northeastern Taiwan and Kuroshio. On the other hand, Surface flows have strong seasonal variations in the Luzon strait, i.e., toward the southeastern side of Taiwan in the summer and intrude into the South China Sea (SCS) in the fall and winter. Deep currents in the Luzon Strait, however, flow mostly into the SCS regardless of seasonality. Maximum speed of deep current can reach 6 cms . Mixed-layer depth in the northern
SCS is approximately 50m in the spring and summer, and about 110m depth in winter.
The third part of this thesis concerns with the anticyclonic circulation off the southwestern Taiwan coast. Float observations show that this circulation exists almost all year round in 2009. Surface currents have a maximum speed in early May, reaching 104 cms , and the wind stress curl attains a maximum negative value. It is conjectured that this anticyclonic eddy is generated primarily due to the restriction of local coast and topography, and the wind stress curl is the secondary mechanism. Surface current derived from Shipboard ADCP is also consistent with the float results. The diameter of this eddy is about 110 km. T-S characteristics of Kuroshio can be observed at 150-210m depth, indicating a close link between this eddy and the Kuroshio. Finally, anticyclonic warm eddies east of Kuroshio are also investigated from the float data. It is found that the eddy flow structure in this region is more obvious in depths than in surface. Temperature distribution below the depth of 200 m also confirms the warm core structure. At an event during which when one float incidentally travelling through a cold eddy and an adjacent warm eddy, the temperature difference can reach 4.5 ¢J at 160m depth. The warm eddies are found to be more stable and more frequently observed than the cold eddies in this region.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0827110-213627 |
| Date | 27 August 2010 |
| Creators | Chang, Yung-sheng |
| Contributors | I-Huan Lee, Yu-Huai Wang, Guan-Yu Chen, Ruo-Shan Tseng |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0827110-213627 |
| Rights | restricted, Copyright information available at source archive |
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