Source water of two-pronged northward flow in the southern Taiwan Strait in summer

Journal of Oceanography (Impact Factor: 1.27). 07/2011; 67(4):385-393. DOI: 10.1007/s10872-011-0036-1

ABSTRACT It is generally accepted that the flow is northward in the Taiwan Strait during summer and that the strongest current is detected in the Penghu Channel between the Penghu Islands and the Taiwan Island. This current, the eastern prong flow, is made up of waters from the South China Sea (SCS) and the Kuroshio. North of the Penghu Islands, the current veers to the west before turning northward again because of the shallow Chang-Yuen Ridge, and extends westward off the coast of Taiwan. There is a second prong of northward flow existing between the Taiwan Bank and the China mainland coast. Here, we show with observational data as well as results from a numerical model that this water receives little influence from the Kuroshio and is distinctively cooler, fresher, less oxygenated and more acidic, and contains more dissolved inorganic carbon than waters at the same density level of the eastern prong. Evidence is provided to show that the source water of the western prong should be the subsurface water from the strong upslope advection flowing northward from the SCS to the southern Taiwan Strait and upwelling along the coast during the favorable southwesterly wind. Subsequently, the upwelled water flows over the saddle west of the Taiwan Bank and joins the main flow northwest of the Penghu Islands.

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Available from: Chen-Tung Arthur Chen, Sep 26, 2015
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    • "There are four papers related to the current, upwelling, or water mass in the Taiwan Strait and in the Beibu Gulf. Hong et al. (2011) analyze the observational data and numerical model results and confirm the two-pronged northward flow in the southern Taiwan Strait in summer. Qiu et al. (2011) "
    Journal of Oceanography 12/2011; 67(4):359-363. DOI:10.1007/s10872-011-0063-y · 1.27 Impact Factor
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    ABSTRACT: In order to understand the fate of nutrients in the Taiwan Strait during summer, we built a coupled physical-biological numerical ocean model, which can capture the basic hydrographic and biological features within the strait. The nutrient that we chose to model is dissolved inorganic nitrogen (DIN). The model includes individual reservoirs for nitrate (NO3) and ammonium (NH4). Both the observational evidence and model results show that NO3 in the strait originates primarily from the upwelling subsurface water in the northern South China Sea (SCS) that enters the strait via the eastern and western routes separated by the Taiwan Bank. The coupled physical and biological effects on the NO3 transport at these two routes are highlighted in the study. For the western route, the shallow topography and the coastal upwelling intensify the biological uptake of NO3 in the whole water column. Consequently, the nitrogenous contribution by this route is mainly in form of the particulate organic nitrogen (PON). In contrast, NO3 is transported conservatively below the nitricline at the deep eastern route, contributing the whole NO3 supply in the TWS. The model estimates the fluxes of DIN and PON into the TWS, from the northern SCS, are 1.8 and 4 kmol s-1, respectively. Over half (˜1 kmol s-1) of the DIN is synthesized into PON by the phytoplankton in the strait. Overall, this study estimates the physical and biological effects on the nutrient transport in the TWS during summer.
    09/2013; 118(9):n/a-n/a. DOI:10.1002/jgrc.20300
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    ABSTRACT: The Penghu Channel is the main channel connecting the East and South China Seas, two of the largest marginal seas in the world. Located in the southeast of Taiwan Strait, the Penghu Channel is usually covered by the high salinity water from the South China Sea and the Kuroshio. However, we observed abnormal low-salinity water in the Penghu Channel during a cruise through the southern Taiwan Strait and northern South China Sea in August 2008. We argue that the normalized alkalinity is a good indicator for the identification of a river plume as it is not affected by rainwater. Using satellite-derived water transparency and chlorophyll images and field-measured alkalinity, the source of this low salinity water was found to be the intrusion of the Pearl River plume. A significant phytoplankton bloom across the entire Taiwan Strait occurred with the intrusion event. The intrusion was not a unique event, as we also found a strong jet-shaped Pearl River plume intruding into the Penghu Channel in the summer of 2009 from cloud-free satellite-derived images. Time series satellite data reveal that the Pearl River plume intrudes into the Penghu Channel in the summer of most years. Multiple data analysis and modeling simulation indicate that a large river discharge and strong southwesterly winds on the shelf may be responsible for the significant intrusion of the Pearl River plume into the Penghu Channel in summer. As the Pearl River plume has a high nutrient and dissolved inorganic carbon content, combined with the strong northward flows through the Penghu Channel, such intrusions may contribute to the nutrient dynamics and carbon budget of the East and northern South China Seas.
    Journal of Sea Research 01/2015; 95:1-15. DOI:10.1016/j.seares.2014.10.003 · 1.99 Impact Factor