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Approximately 700 water samples from the South China Sea (SCS) and 300 water samples from the western Philippine Sea (wPS) were collected during eight cruises from August 2003 to July 2007 to determine methane (CH 4 ) distributions from the surface to a depth of 4250 m. The surface CH 4 concentrations exceeded atmospheric equilibrium, both in the SCS and the wPS, and the concentrations were 4.5±3.6 and 3.0±1.2 nmol L −1 , respectively. The sea-to-air fluxes were calculated, and the SCS and the wPS were found to emit CH 4 to the atmosphere at 8.6±6.4 µmol m −2 d −1 and 4.9±4.9 µmol m −2 d −1 , respectively. In the SCS, CH 4 emissions were higher over the continental shelf (11.0±7.4 µmol m −2 d −1 ) than over the deep ocean (6.1±6.0 µmol m −2 d −1 ), owing to greater biological productivity and closer coupling with the sediments on the continental shelf. The SCS emitted 30.1×10 6 mol d −1 CH 4 to the atmosphere and exported 1.82×10 6 mol d −1 CH 4 to the wPS. The concentrations of both CH 4 and chlorophyll a were high in the 150 m surface layer of the wPS, but were not significantly correlated with each other. CH 4 concentrations generally declined with increasing depth below the euphotic zone but remained constant below 1,000 m, both in the SCS and the wPS. Some high CH 4 concentrations were observed at mid-depths and bottom waters in the SCS, and were most likely caused by the release of CH 4 from gas hydrates or gas seepage. [ABSTRACT FROM AUTHOR]

Dissolved inorganic and organic carbons (DIC and DOC) provide two of the largest pools of carbon in the ocean. However, limited information is available concerning the relationship between DIC and different constituents of dissolved organic matter (DOM), such as fluorescent compounds. This study investigates the dynamics of DOM and their implications for carbon and nutrient cycling in the east Taiwan Strait, using DOC, absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC). The study area was dominated by the waters from the South China Sea during the sampling period in summer 2013. The dynamics of DOM were influenced strongly by microbial activities, as indicated by the close correlations (the absolute value of r : 0.75–0.97, p < 0.001) between apparent oxygen utilization (AOU) and DOM parameters, including DOC, the absorption coefficient at 280 nm, the fluorescence intensity of protein-like component C3, and the humification index HIX. The contribution of DOC degradation to the net increase in DIC was approximately 15% and 21% in the north and the south of the east Taiwan Strait, respectively. The DIC was correlated negatively with protein-like fluorescence, revealing the production of DIC by the microbial degradation of labile components. The DIC was correlated positively with humic-like fluorescence and HIX, suggesting that the storage of carbon by produced refractory humic substances could not compensate for the release of DIC in the deeper waters. The correlations of nutrients with DOM parameters were similar to those of DIC, further indicating the profound impacts of the dynamics of labile DOM on nutrient cycling. [ABSTRACT FROM AUTHOR]

Approximately 600 water samples from the South China Sea (SCS) and 250 water samples from the West Philippines Sea (WPS) were collected during seven cruises from August 2003 to July 2007 to determine nitrous oxide (N 2 O) distributions between the surface and a maximum depth of 4250 m. In the SCS, the average surface N 2 O concentration exceeded the atmospheric equilibrium concentration (on average 132±23%); however in the WPS, the surface N 2 O concentration was lower than the atmospheric equilibrium concentration (on average 90±22%). The N 2 O concentration reached a maximum (~23 nmol L −1 ) in the WPS at 800–1000 m, and (~28 nmol L −1 ) at a shallower depth of around 600–800 m in the SCS, owing to vertical mixing and intensive upwelling in the SCS. In the SCS, the surface N 2 O concentration was 7.59±1.32 nmol L −1 and the calculated sea-to-air flux was 5.5±3.9 μmol m −2 d −1 . The surface N 2 O concentration in the WPS, 5.19±1.26 nmol L −1 , was lower than that in the SCS. The WPS is a sink for N 2 O and the calculated sea-to-air flux was −1.7±3.9 μmol m −2 d −1 . The SCS emitted 19.3×10 6 mol d −1 N 2 O to the atmosphere and exported 8.5×10 6 mol d −1 N 2 O to the WPS during the wet season. [ABSTRACT FROM AUTHOR]

The Luzon Strait is the main channel connecting the West Philippine Sea (WPS) and the South China Sea (SCS). It has been known that the strait’s upper-layer waters have a net tendency to flow into the SCS in winter, whereas its intermediate waters mainly flow out of the SCS year round. A shallow, longitudinal subsurface front separates the WPS Tropical Water and SCS Tropical Water which are characterized by the maximum salinity. This front is located between 119.8 and 121°E, with the WPS Tropical Water extending westward the most in winter during normal periods. During El Niño events, however, the WPS Tropical Water extends westward the most compared with those during normal and La Niña periods. Further, an intermediate-depth front also separates the WPS Intermediate Water and the SCS Intermediate Water at roughly 122°E along 21.75°N. This study reports that this intermediate-depth front is roughly longitudinal across the Luzon Strait from 19°N to 21.75°N. Although it is generally stationary at 122°E, the WPS Intermediate Water extends westward the most in spring whereas in fall it extends westward the least. In spring during El Niño periods and in fall during La Niña periods, the WPS Intermediate Water also extends westward the most. The fact that the front for Subtropical Water is located up to 1.7° west of the front of the Intermediate Water indicates that the front is tilted westward when the depth of the front decreases from the intermediate depth up to subsurface depth. Such a tilt is consistent with the notion that there is a net flux of near surface waters flowing into the SCS, while there is a net flux of intermediate waters flowing out of the SCS. Finally, the tilt is the most significant during El Niño periods and the least apparent during La Niña periods. [ABSTRACT FROM AUTHOR]

The Taiwan Strait is the only direct passage between the South China Sea (SCS) and the East China Sea. Variations in the intensity of Kuroshio Branch and surface currents in the SCS result in seasonal and inter-annual variability in the hydrography of the SE Taiwan Strait, where the northwardly pointing funnel-like Penghu Channel is located. These currents vary with the intensity and direction of monsoons. The teleconnection between air-sea interaction of the east Pacific and west Pacific reportedly has time differences. The data in this study reveal that the salinity of the seawater in the Penghu Channel is highest during El Niño events with a seven-month lag to the monthly Niño 3.4 index, and lowest during La Niña periods, also with a lag of seven months to the monthly Niño 3.4 index. The chemical parameters also vary with these events. The concentrations of apparent oxygen utilization, nutrients, and hydrogen ions vary with the mixing ratio of SCS water and Kuroshio Branch water. The maximum concentrations of nutrients are significantly higher during the summer, seven months after a La Niña event (La Niña-7), than in other seasons. However, biological activities also affected these chemical parameters. In spring, active photosynthesis consumes more nutrients and hydrogen ion concentrations in La Niña-7 periods than in normal-7 periods. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The trajectories of 110 satellite-tracked surface drifters from 1989 to 2007 were analyzed to elucidate near-surface circulation in the Taiwan Strait. Although the summer circulation observed generally agrees with previous studies, several aspects of the winter circulation were revealed by the analyses. Unlike many earlier studies, which have suggested that a northward (southward) current prevails in the eastern (western) part of the Taiwan Strait during the northeast monsoon season, this study shows that almost all winter drifters that entered the Taiwan Strait eventually moved southward. Inside the Taiwan Strait, northward moving tracks can only be found in the Penghu Channel. After passing the Penghu Channel, the drifters were blocked by the northeast monsoon wind and the Yun-Chang Rise, and turned southward. None of the drifters flowed persistently northward through the Taiwan Strait in winter. In the southern Taiwan Strait, three typical patterns of circulation were observed for the winter trajectories-the 'throughflow' pattern that enters the South China Sea flowing westward along the slope; the loop current pattern that circulates anticyclonically and returns to the Kuroshio; and the blocked intrusion pattern that penetrates into the Taiwan Strait through the Penghu Channel. [ABSTRACT FROM AUTHOR]

Abstract: To study the dissolved carbonate system in the South China Sea (SCS) and to understand the water mass exchange between the SCS and the West Philippine Sea (WPS), pH, total alkalinity and total CO2 were measured aboard the R/V Ocean Researcher 1. Because of the sill that separates these two seas in the Luzon Strait with a maximum depth of 2200 m, the SCS Deep Water has characteristics similar to those of water at about 2200 m in the WPS. The minimum pH and the maxima of normalized alkalinity and total CO2 commonly found in the open oceans at mid-depth also prevail in the WPS but are, however, very weak in the SCS. Rivers and inflows from Kuroshio Surface and Deep Waters through the Luzon Strait as well as those through the Mindoro Strait transport carbon to the SCS year-round. Meanwhile, the outflowing Taiwan Strait water as well as the SCS Surface and Intermediate Waters of the Luzon Strait transports carbon out of the SCS year-round. The Sunda Shelf is also a channel for carbon transport into the SCS in the wet season and out of the SCS in the dry season. fCO2 data and mass balance calculations indicate that the SCS is a weak CO2 source in the wet season but an even weaker CO2 sink in the dry season. With these facts taken together, the SCS is likely a very weak CO2 source. Anthropogenic CO2 penetrates to about 1500 m in depth in the SCS, and the entire SCS contains 0.60±0.15×1015 g of excess carbon. Typical profiles of pH as well as the degree of saturation of each of calcite and aragonite in 1850 and 1997 are presented, and those for 2050 AD are projected. The maximum decrease in pH is estimated to be 0.16 pH units in the surface layer when the amount of CO2 is doubled. It is anticipated that aragonite in the upper continental slope will likely start to dissolve, thereby neutralizing excess CO2 by around 2050 AD. This paper is unique in that it presents the results of the first attempt ever to estimate the past, present and future physico-chemical properties of the world''s largest marginal sea. [Copyright &y& Elsevier]

The South China Sea (SCS) is the world’s largest tropical marginal sea with an oligotrophic basin. In June 2015, a rare large phytoplankton bloom, which is ~500 km long, 100 km wide and lasting more than 19 days, was captured in the northern SCS basin by satellite daily chlorophyll images. Water within the bloom area had a feature of low salinity and high temperature measured by an accidental-passing cruise. Meanwhile, satellite sea level anomaly images and drifter trajectory proved there was a cyclonic eddy nearby. No typhoon and heavy rain happened in this period, so we believed the bloom was triggered by the injection of nutrient-rich Pearl River plume driven by eddy. This is the first report on eddy-entrained Pearl River plume into the SCS, which would raise a new view on irregular transportation of nutrient and carbon and its related biogeochemical influence on the oligotrophic ocean. [ABSTRACT FROM AUTHOR]

Typhoon-enhanced primary production (PP) in the ocean has long been neglected, as it is a big challenge to estimate such PP due to the lack of ocean color data obscured by clouds and rainfall that accompany typhoons and complicated biological responses. In this study, we developed a statistical approach, based on all the typhoons passing though the South China Sea (SCS) and the Western North Pacific Subtropical Ocean (WNPSO) during 2003 and 2012. We then estimated the annual and interannual carbon fixation induced by typhoons in the SCS and the WNPSO. The annual mean carbon fixation due to typhoons in the whole SCS was estimated to be approximately 2.716±0.304 Mt (1 Mt=10 12 g), equivalent to 5–15% of the new PP of the SCS. This suggests that typhoons contribute to the biological carbon fixation in the SCS. In terms of the WNPSO, the annual mean carbon fixation due to typhoons was only about 2.112±0.640 Mt, although the area is much larger and super typhoons occur more frequently. The main reason for the smaller value in the WNPSO is that the cold nutrient-rich water is more difficult to be brought to the upper layer to support the growth of phytoplankton due to thicker mixed layer depth and deeper nutricline depth in the WNPSO in comparison with those in the SCS. In addition, typhoon-enhanced PP tended to be higher in the El Niño years in the WNPSO due to increased occurrence of super typhoons, while it was lower in the La Niña years. However, no obvious relationship with El Niño-Southern Oscillation (ENSO) was found in the SCS during the study period. [ABSTRACT FROM AUTHOR]

Open ocean mariculture can be established by the artificial upwelling of deep ocean water (DOW). However, one of the major obstacles is the difficulty of containing a nutrient-rich DOW plume without significant dilution. In this paper, the hydrodynamic design of DOW discharge for the creation of the DOW plume in the South China Sea (SCS) is presented. The trajectory and DOW concentration of the plume in a stratified ocean environment where a sharp density interface exists is investigated relative to the current speed, pumped water flow rate, pipe diameter and optimal depth of DOW discharge. A mathematical model is presented to ensure that a desirable nutrient concentration in the DOW plume can be maintained under specific ocean stratification and current conditions. The validity of the mathematical model is verified by a computational fluid dynamics (CFD) analysis on the flow and nutrient transport of the DOW plume. The results show that the volume concentration of DOW in the plume can be controlled by setting up the flow rate, pipe diameter and corresponding optimal DOW discharge depth. In this way, the nutrient-rich DOW plume can be sustained in the open ocean to stimulate marine primary productivity. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that skin sea surface temperature (SSST) is different from bulk sea surface temperature (BSST) by a few tenths of a degree Celsius. However, the extent of the error associated with dry deposition (or uptake) estimation by using BSST is not well known. This study tries to conduct such an evaluation using the on-board observation data over the South China Sea in the summers of 2004 and 2006. It was found that when a warm layer occurred, the deposition velocities using BSST were underestimated within the range of 0.8–4.3%, and the absorbed sea surface heat flux was overestimated by 21 W m−2. In contrast, under cool skin only conditions, the deposition velocities using BSST were overestimated within the range of 0.5–2.0%, varying with pollutants and the absorbed sea surface heat flux was underestimated also by 21 W m−2. Scale analysis shows that for a slightly soluble gas (e.g., NO2, NO and CO), the error in the solubility estimation using BSST is the major source of the error in dry deposition estimation. For a highly soluble gas (e.g., SO2), the error in the estimation of turbulent heat fluxes and, consequently, aerodynamic resistance and gas-phase film resistance using BSST is the major source of the total error. In contrast, for a medium soluble gas (e.g., O3 and CO2) both the errors from the estimations of the solubility and aerodynamic resistance are important. In addition, deposition estimations using various assumptions are discussed. The largest uncertainty is from the parameterizations for chemical enhancement factors. Other important areas of uncertainty include: (1) various parameterizations for gas-transfer velocity; (2) neutral-atmosphere assumption; (3) using BSST as SST, and (4) constant pH value assumption. [Copyright &y& Elsevier]

Abstract: Results of clay mineralogy in 140 samples collected in major rivers and lakes in southwestern Taiwan and on the seafloor off Taiwan in the northeastern South China Sea (SCS), combined with clay mineral records of the Pearl River drainage basin, rivers in Luzon, and the South China shelf and slope, are used to semi-quantitatively evaluate the detrital fine-grained sediment contribution of Taiwan to the northern SCS. The clay mineral assemblage of the Taiwan-sourced sediments consists dominantly of illite (average 56%) and chlorite (41%), with very scarce kaolinite and smectite. Their respective distribution from the rivers and lakes to the seafloor off Taiwan does not show obvious basin-wide differences. Linear correlations of illite chemistry index with illite crystallinity and of illite crystallinity with kaolinite (%) present two end-members of provenances, the Pearl River and Taiwan, for the South China shelf and slope. Assuming that kaolinite in the northern SCS is provided completely from the Pearl River, the contribution of Taiwan in clay minerals is evaluated as 29% to the South China shelf and 23% to the South China slope, respectively. Accordingly, the contribution of the Pearl River to the South China shelf and slope is 52% and 31%, respectively. The Luzon Arc accounts for the rest of clay mineral components for the northern SCS mainly by providing smectite. The Bashi Strait-crossed branches of the southward deep North Pacific Deep Water and the northward surface Kuroshio Current in the western Pacific may transport Taiwan-sourced suspended sediments westwards to the northern SCS. [Copyright &y& Elsevier]