A Study on the Vertical Thermohaline Fluctuation in the Waters off Quay-Shan Island during 1997-1998 ENSO Event

• Main Authors: Tsung-Jung Yeh, 葉宗融
• Other Authors: 呂學榮
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/18335973429734300670

碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 92 === Abstract The 1997/98 ENSO event is the strongest one occurred in the Twentyth Century and its influence to Taiwan waters is highly concerned. Since lack of long-term subsurface in situ data, we usually use SST data obtained by Satellite Remote Sensing as instead. The waters off Quay-Shan Island, located in northeastern Taiwan, with favorable geographic and oceanographic features contributed by seabed terrain and Kuroshio Current, has been one of the most important fishing ground of Taiwan for a long time. During the period, the Ocean Research Vessel (Ocean Researcher II) conducted her routine cruises and accumulated massive CTD observation data in the interested area. In order to investigate the vertical thermohaline fluctuation in the region during the 1997/98 ENSO event, we analyze CTD data collected in 164 stations by the vessel. The major findings of the analysis are as follows: （1）According to SST remote sensing data, the time series of SST anomalies in the Quay-Shan waters as well as its adjacent waters in the north and south are out of phase with SOI time series. Such phenomena observed in the south are much more significant than those in the north, which indicate that the ENSO do affect the SST in Quay-Shan waters. （2）In upper layers (<100 m), the declination of water temperatures measured in each station have similar T-D curves, however those in deeper layers (>100 m) differ considerably station by station. The variations of salinity in surface layers are between 33.2-34.7 psu. In upper layers (<100 m ), the salinity inceases while the depth increases, with a maximum value about 34.5 psu. The salinity then decreases with depths in deeper layers until reaching the depth of 300m where salinity levels are stable around 34.4 psu. （3）ANOVA shows that the inter-annual differences of the water temperature are mainly located at depths above 150 m. There are no significant inter-annual differences in the waters under 150 m. For salinity, the coastal and pelagic waters show different characteristics. The inter-annual differences of the former exist in the whole layers above 150 m, however those differences of the latter only occur in the depths of 150 m and 200 m . In July 1998, the El Niño event converse to La Niña event during 1997 /98 ENSO event. According to the CTD data, the most significant values of variation observed in surface waters and sub-surface waters are during 1998. This suggests that the ENSO event’s influence is able to reach subsurface of the study waters to a certain extent. As the alignments of the CTD stations in the study area are not even in space and time, it is impossible to built up a model for the result. It is recommended that to establish a stationary monitoring system at sea would be the only solution. Keywords：Quay-Shan Island、ENSO、CTD observation