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Frontiers of Earth Science

Front Earth Sci    2013, Vol. 7 Issue (2) : 141-150     DOI: 10.1007/s11707-013-0355-1
On summer stratification and tidal mixing in the Taiwan Strait
Jia ZHU, Jianyu HU, Zhiyu LIU()
State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen 361005, China
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On continental shelves, a front that separates the sea into well-mixed and stratified zones is usually formed in warm seasons due to spatial variations of tidal mixing. In this paper, using eight years of in situ hydrographic observations, satellite images of sea surface temperature (SST) and chlorophyll-a (Chl-a) concentration, and results of a tidal model, we investigate summer stratification in the Taiwan Strait and its dependence on tidal mixing, upwelling, and river diluted water plumes. In most regions of the strait the dominant role of tidal mixing in determining the thermohaline structure is confirmed by the correlation between the two; there are some regions, however, where thermohaline structure varies in different ways owing to significant influences of upwelling and river diluted water plumes. The well-mixed regions are mainly distributed on the Taiwan Bank and in the offshore regions off the Dongshan Island, Nanao Island, and Pingtan Island, while the northern and central Taiwan Strait and the region south of the Taiwan Bank are stratified. The critical Simpson-Hunter parameter for the region is estimated to be 1.78.

Keywords Taiwan Strait      stratification      tidal mixing      coastal upwelling      river plume     
Corresponding Authors: LIU Zhiyu,   
Issue Date: 05 June 2013
 Cite this article:   
Jia ZHU,Jianyu HU,Zhiyu LIU. On summer stratification and tidal mixing in the Taiwan Strait[J]. Front Earth Sci, 2013, 7(2): 141-150.
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Fig.1  Bathymetry of the study area. Acronyms: ECS-East China Sea, SCS-South China Sea, PT-Pingtan, MZ-Meizhou, XM-Xiamen, DS-Dongshan, NA-Nanao, ST-Shantou, WC-Wuci, TB-Taiwan Bank, PH-Penghu Archipelagos, PHC-Penghu Channel. The depth contours are in meters. Inset shows the model domain.
Fig.2  Comparison between observed and modeled tidal current ellipse axes for the (a) M and (b) K tidal constituents at six stations in the TWS. The observation data are redrawn from Jan et al. (). The observed stations (WC1, WC2, WC3, WC4, EWC and PHC) are marked in Fig. 1.
Fig.3  Distributions of temperature (a) and salinity (b) STDs. The study area is divided into six regions: Area A-F Acronyms: PT-Pingtan, MZ-Meizhou, XM-Xiamen, DS-Dongshan, NA-Nanao, ST-Shantou, WC-Wuci, TB-Taiwan Bank, PH-Penghu Archipelago, PHC-Penghu Channel.
Fig.4  Typical profiles of temperature (red) and salinity (blue) in Areas A-F.
Fig.5  Distribution of tidal mixing parameter (). The areas where <5 are filled with color, and the area with >5 are filled in gray. Acronyms: PT-Pingtan, MZ-Meizhou, XM-Xiamen, DS-Dongshan, NA-Nanao, ST-Shantou, WC-Wuci, TB-Taiwan Bank, PH-Penghu Archipelago, PHC-Penghu Channel.
Fig.6  Distribution of the turbulent kinetic energy dissipation rate (log[? (W kg)]) along section V. The section location is shown in the lower left inset.
Fig.7  Comparison of STDs of temperature (T) and salinity (S), and tidal mixing parameter in Areas A-F.
Fig.8  Linear regression of the versus STD relationship.
Fig.9  MODIS images of (a) SST on August 20, 2008 and (b) Chl- on July 9, 2009. The contours for the critical tidal mixing parameter ( = 1.78) are marked in red. Section I~VI are marked with black lines. Locations of the summertime upwelling cores in the TWS are marked by blue ellipses (adopted from Hu et al. ()). Acronyms: PT-Pingtan, MZ-Meizhou, XM-Xiamen, DS-Dongshan, NA-Nanao, ST-Shantou, WC-Wuci, TB-Taiwan Bank, PH-Penghu Archipelago, PHC-Penghu Channel, SCS-South China Sea, ECS-East China Sea.
Fig.10  Sectional distributions of temperature (°C) and salinity at sections I-VI. The section locations are shown in the lower left insets.
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