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Major and trace elements, Sr and Nd isotopes of bulk particles from the SCS‐NW and SCS‐N‐03 traps were studied to trace the provenance of sinking particles in the northern South China Sea (SCS). About 63% of biogenic materials and most of lithogenic materials from the SCS‐NW trap may be contributed from resuspended sediments, and more biogenic materials are collected in winter than in summer. The immobile‐element discrimination diagrams also indicate that the lithogenic materials of particles are, to a large degree, from local seafloor sediments, and that the lithogenic materials of particles from SCS‐N and SCS‐W traps have seasonal variations. Sr isotopes (87Sr/86Sr and δ88Sr) of bulk particles are significantly influenced by biogenic materials and cannot be used in provenance tracing. In contrast, Nd isotopes are ideal tools to trace particle provenance. However, the traditional Nd isotope (143Nd/144Nd) shows no statistical difference on the particles of the SCS‐NW and SCS‐N‐03 traps, making it unable to identify their provenance. Fortunately, the stable Nd isotope, ε146Nd, shows different correlation trends to ε143Nd in these two traps, suggesting that stable Nd isotope can potentially identify the sources of lithogenic materials in the northern SCS. Our results indicate that distribution and transportation of sinking particles are controlled by currents of the SCS mainly driven by the East Asian Monsoon. Plain Language Summary: As the largest semi‐enclosed marginal sea in the west Pacific, the South China Sea (SCS) is supplied with a large amount of suspended sediments from its surrounding continents and islands. Studies on sedimentary process and source of sediments in the SCS have long been carried out, but no consensus has been reached yet. This study presents elemental and Sr‐Nd isotope geochemistry of sinking particles from the northern SCS. According to fluxes and element concentrations of sinking particles, we find that resuspended sediments are an important contributor to sinking particles in the SCS. The relationship between trace elements of sinking particles and offshore surface sediments indicates that these resuspended sediments may be derived from continental shelves. The distribution and transportation of sinking particles are influenced by hydrological conditions of the SCS mainly driven by the East Asian monsoon. This study also reveals that stable Nd isotope could be a powerful tool in tracing sediment provenances in the northern SCS. Therefore, our results will improve the understanding of sediment transportation and sedimentary processes in the northern SCS. Key Points: Resuspended sediments are an important contributor of the sinking particles collected by sediment traps, especially deep trapsProvenance and seasonal variation of sinking particles can be identified by immobile‐element discrimination diagramsThe stable Nd isotopic composition coupled with conservative trace elements is a potential tool in provenance tracing [ABSTRACT FROM AUTHOR]

To elucidate the sources and transformations of nitrogen in the South China Sea (SCS), the nitrogen isotopic composition of nitrate ( $${\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}$$ ) was measured in seawater samples from the water column of this marginal sea and the adjacent western North Pacific Ocean (WNP). Comparison of the isotopic signatures from these two locations suggests that the main source of nitrogen into the SCS was nitrate that entered from the WNP through the Luzon Strait. Values of $${\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}$$ were generally lower in the SCS than in the WNP, and the $${\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}$$ maximum observed in the SCS intermediate water was lower than the corresponding WNP maximum. This pattern is attributed to mixing within the SCS in combination with the outflow of SCS intermediate water to the WNP. A mass balance model indicates that atmospherically derived N (a combined input of new nitrogen from marine N fixation and atmospheric deposition) supplied approximately 6% of the particulate nitrogen exported from the euphotic zone to the deep SCS. This supply of isotopically light nitrogen cannot, however, explain the low and downward-decreasing δN that has been previously observed in sinking particles of the deep SCS. We propose that an alternative explanation might be a downward-increasing ratio of isotopically light NH -N to organic N due to the degradation of organic N within the sinking particles (i.e., relative enrichment of the NH ) and also particle incorporation of excreted ammonium from zooplankton. [ABSTRACT FROM AUTHOR]

Seasonal variability of diatom abundance and species composition in sinking particles in the northern South China Sea was studied using continuous time-series sediment trap moorings during a one-year period, 2009–2010. A clear seasonal pattern of diatom abundance was observed, with higher fluxes in winter than in summer. This could be related to positive response of diatom growth to increased nutrient supply from the subsurface waters as a result of enhanced vertical mixing in winter. Mesoscale eddy activities and strong Asian dust input could also stimulate the diatom growth and increase the diatom export flux to the deep South China Sea. The strong Asian dust input during spring 2010 probably accelerated the aggregation and downward flux of diatoms in the northern South China Sea. No distinctive seasonal pattern in diatom species composition was recorded, but there was a close correlation of diatom abundances with the cell size and the degree of silification. The sinking velocity of the diatom related particles from the sea surface to the deep South China Sea has been estimated to be ~30–50 m d −1 by comparing the surface chlorophyll a with the diatom abundance and species in sediment traps at 1003 m and 3226 m depths. Strong dissolution of small-sized and low-silicified diatom species and lateral advection of particles were also indicated for the deep northern South China Sea. The present results are crucial as a basis for future understanding of fossil assemblage changes in connection with palaeoclimatic and palaeooceanographic research. [ABSTRACT FROM AUTHOR]

Deals with a study which examined the relationship among siliceous microplankton fluxes, monsoon climate and El Nino events in the central South China Sea from 1993 through 1995. Materials and methods; Results and discussion; Conclusions.

Estimates primary and export production in the South China Sea, which reflects the net absorption of carbon dioxide by marine euphotic zone. Adjustment of atmospheric carbon dioxide content by ocean interior; Influence of monsoons on carbon fluxes; Paleoproductivity or organic carbon accumulation rate in the glacial age.

The East Asian Monsoon and mesoscale eddies are known to regulate primary production in South China Sea (SCS), the largest tropical marginal sea; however, their contributions to the deep biogenic flux are yet to be quantified. Based on 7-year time series sediment trap observations at the depth of 1200 m in the central SCS, we used the monthly average sinking biogenic fluxes to evaluate the impact of the monsoon and mesoscale cyclonic eddies on biogenic fluxes in combination with remote sensing physical parameters. The monthly average particulate organic carbon (POC) and opal fluxes, ranging from 3.0 to 5.2 and 14.8–34.9 mg m −2 d −1 , respectively, were higher during the northeastern monsoon period. This corresponded to the deeper mixed layer depth and higher net primary production in this area, due to nutrient replenishment from the subsurface induced by monsoon transition and surface cooling. In contrast, lower POC and opal fluxes occurred during well-stratified inter-monsoon periods. In addition, CaCO 3 flux (23.6–37.0 mg m −2 d −1 ) exhibited less seasonality and was assumed to originate from foraminifera. In terms of the long-term record, the combined effect of cyclonic eddies and mixing in the upper ocean could effectively regulate the temporal variation in the biogenic flux. In particular, the opal and POC fluxes in cyclonic eddies were 116% and 41% higher on average, respectively, than those during the non-cyclonic eddy period. Since the cyclonic eddies mainly occurred during the northeastern monsoon period, their contributions to biogenic flux via diatom blooms might overlap the regular winter flux peak, which could make the biological carbon pump more efficient at CO 2 sequestration during this period thus amplifying the impact of seasonal transition. [ABSTRACT FROM AUTHOR]

Abstract: The South China Sea (SCS) is the largest tropical marginal sea in the western Pacific Ocean. While the proxy is known to reflect the sea surface temperature (SST) of the 0–30m mixed layer in the SCS, little is known about the applicability of the TEX86 proxy. Here, we present results from paired analyses of , a modified version of TEX86, and from core top sediment samples from the SCS. -based SST calculated from the global regression exhibited slightly higher values (avg. 28.7°C, range 27.1–30.3°C) than values from the World Ocean Atlas 1994 (avg. 27.4°C, range 26.1–28.6°C) and -based temperature values (avg. 27.3°C, range 26.1–29.0°C). Moreover, the linear relationship between and SST was poor (r 2, 0.44). Correlation analysis of with annual temperature and seasonal temperature at various depths revealed that correlated better with annual sea temperature at 30–125m (r, 0.89) than with temperature in the 0–30m mixed layer (r, 0.69). This suggests that reflects a deeper and cooler subsurface temperature rather than surface or mixed layer temperature in the SCS. As a result, the global regression, which results in higher SST values, could not be applied to predict subsurface temperature in the SCS and a local calibration of vs. 30–125m subsurface temperature was tentatively established. Furthermore, the difference between and derived temperature (ΔT Alkenone–GDGT) correlated moderately (r, 0.62) with the depth of the thermocline of the 18°C isotherm in the SCS, suggesting that the difference may provide a proxy for upper ocean vertical thermal gradient in this marginal sea. [Copyright &y& Elsevier]

Abstract: The mineralogy, major and trace elements, and neodymium and strontium isotopes of surface sediments in the South China Sea (SCS) are documented with the aim of investigating their applicability in provenance tracing. The results indicate that mineralogical compositions alone do not clearly identify the sources for the bulk sediments in the SCS. The Nd isotopic compositions of the SCS sediments show a clear zonal distribution. The most negative ε Nd values were obtained for sediments from offshore South China (−13.0 to −10.7), while those from offshore Indochina are slightly more positive (−10.7 to −9.4). The Nd isotopic compositions of the sediments from offshore Borneo are even higher, with ε Nd ranging from −8.8 to −7.0, and the sediments offshore from the southern Philippine Arc have the most positive ε Nd values, from −3.7 to +5.3. This zonal distribution in ε Nd is in good agreement with the Nd isotopic compositions of the sediments supplied by river systems that drain into the corresponding regions, indicating that Nd isotopic compositions are an adequate proxy for provenance tracing of SCS sediments. Sr isotopic compositions, in contrast, can only be used to identify the sediments from offshore South China and offshore from the southern Philippine Arc, as the 87Sr/86Sr ratios of sediments from other regions overlapped. Similar zonal distributions are also apparent in a La–Th–Sc discrimination diagram. Sediments from the west margin of the SCS, such as those from Beibuwan Bay, offshore from Hainan Island, offshore from Indochina, and from the Sunda Shelf plot in the same field, while those offshore from the northeastern SCS, offshore from Borneo, and offshore from the southern Philippine Arc plot in distinct fields. Thus, the La–Th–Sc discrimination diagram, coupled with Nd isotopes, can be used to trace the provenance of SCS sediments. Using this method, we re-assessed the provenance changes of sediments at Ocean Drilling Program (ODP) Site 1148 since the late Oligocene. The results indicate that sediments deposited after 23.8Ma (above 455 mcd: meters composite depth) were supplied mainly from the eastern South China Block, with a negligible contribution from the interior of the South China Block. Sediments deposited before 26Ma (beneath 477 mcd) were supplied mainly from the North Palawan Continental Terrane, which may retain the geochemical characteristics of the materials covered on the late Mesozoic granitoids along the coastal South China. For that the North Palawan Continental Terrane is presently located within the southern Philippine Arc but was located close to ODP Site 1148 in the late Oligocene. The weathering products of volcanic material associated with the extension of the SCS ocean crust also contributed to these sediments. The rapid change in sediment source at 26–23.8Ma probably resulted from a sudden cessation of sediment supply from the North Palawan Continental Terrane. We suggest that the North Palawan Continental Terrane drifted southwards along with the extension of the SCS ocean crust during that time, and when the basin was large enough, the supply of sediment from the south to ODP Site 1148 at the north slope may have ceased. [Copyright &y& Elsevier]