Interannual Carbon and Nutrient Fluxes in Southeastern Taiwan Strait

Abstract

Abstract:The Taiwan Strait (TS) is one of the main sources of phosphate that supports the large fish catches of the phosphate-limited East China Sea (ECS). The Penghu Channel is the deepest part of the TS, and most of the flow of the TS towards the ECS is principally through this channel. Empirical equations that are based on measurements made during 19 cruises (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) were combined with water velocity, salinity, and temperature, which were modeled using HYCOM (the Hybrid Coordinate Ocean Model) to obtain the annual fluxes for total alkalinity (TA), dissolved inorganic carbon (DIC), nitrate plus nitrite, phosphate, and silicate fluxes. The TA and DIC are mainly transported in the top layer (0-55 m) because the current is much stronger there than in the bottom layer (55-125 m) whereas the TA and DIC concentrations in the top layer are only slightly smaller compared with the bottom layer. In contrast, the nitrate plus nitrite flux is mainly transported in the bottom layer because the concentrations are much higher in the bottom layer. Generally, nutrient flux increases with the Pacific Decadal Oscillation (PDO) index, but TA and DIC fluxes increase as the PDO index decreases.

Seasonal Variations of Marine Environment and Primary Production in the Taiwan Strait

“…The seasonal variations of nutrients are strongly influenced by the seasonal change of different water mass occupation. Consequently, the seasonal change of water masses in the Taiwan Strait in this research is in accordance with previous research (Jan et al, 2002(Jan et al, , 2006(Jan et al, , 2010Chen, 2003Chen, , 2011Chen and Sheu, 2006;Wu et al, 2007;Chen et al, 2010;Huang et al, 2018). Hong et al (2011) revealed that there are three upwelling areas in the southern Taiwan Strait in summer.…”

“…In addition, Jan et al (2010) found that the source water in the Taiwan Strait comes from the SCSW in summer. Huang et al (2018) also reported that during the summer and autumn, the main water mass in the Penghu Channel is the SCSW. Moreover, since precipitation is heavier in summer, water in the top layer is warmer and fresher during the summer than during the autumn (Huang et al, 2018).…”

“…Huang et al (2018) also reported that during the summer and autumn, the main water mass in the Penghu Channel is the SCSW. Moreover, since precipitation is heavier in summer, water in the top layer is warmer and fresher during the summer than during the autumn (Huang et al, 2018). As three primary water masses in the Taiwan Strait have different characteristics, different mixing ratios of water masses may cause different chemical and hydrographic conditions.…”

East China Sea increasingly gains limiting nutrient P from South China Sea

“…Those estimates were calculated using chemical data from one or only a few cruises, and so may exhibit higher uncertainty than the data in this study based on 57 cruises. Our pervious study reported that the water, TA, DIC, N, P, and Si transports in the deepest part of the TS, Penghu Channel, are 0.81 ± 0.34 Sv, 1.87 ± 0.79 mmol C s −1 , 1.65 ± 0.71 mmol C s −1 , 1.20 ± 0.99 kmol N s −1 , 0.13 ± 0.085 kmol P s −1 , and 3.06 ± 1.83 kmol Si s −1 30 . Generally, the water and chemical transports in the TS are higher than those in the Penghu Channel except the N transport, and that reflects the substantial southward N transport by the CCC in the TS.

Figure 2Time series of ( a ) water, ( b ) TA, ( c ) DIC, ( d ) N, ( e ) P, and ( f ) Si model-calculated transports.

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“…To understand the exchanges between the ECS and the SCS, the study area covers cross-sections at both ends of the TS. Compared with our preliminary study which investigated the southeastern corner of the TS 30 , this investigation focuses on the interaction between the ECS and the SCS, and mechanisms affecting long-term variations in the TS.…”