In the east coast Peninsular Malaysia region,sediments are transported by several rivers from the east Malaysia into the South China Sea estuary.In the vicinity of the five river estuaries core sediments were collecte...In the east coast Peninsular Malaysia region,sediments are transported by several rivers from the east Malaysia into the South China Sea estuary.In the vicinity of the five river estuaries core sediments were collected in order to investigate rare earth elements(REEs) profile.Core sediments were divided into strata of between 2 to 4 cm intervals and prepared for analyzing by ICP-AES.REE concentrations of 54.3 μg/gr at 24-26 cm in EC4 increased to 114.1 μg/gr at 20-22 cm in EC5.The measured concentration of LREEs and Fe normalized enrichment factors indicated that sediments were not enriched with light rare earth elements derived from effluents of anthropogenic activities.Results of the total concentration were used to establish baseline data in environmental pollution assessment and to develop the correlations between the Ce/Ce and Eu/Eu anomalies and the distribution patterns of some light rare earth elements(LREEs) and the heavy rare earth elements(HREEs).The chondrite-normalized ratios of REEs showed LREEs enrichment and flat HREE depletion.展开更多
The South China Sea (SCS), in particular the northern SCS, is one of ocean areas where energetic internal solitary waves (ISWs)occur most frequently (Cai et al., 2012; Zheng, 2017). Based on the re-appearance period (...The South China Sea (SCS), in particular the northern SCS, is one of ocean areas where energetic internal solitary waves (ISWs)occur most frequently (Cai et al., 2012; Zheng, 2017). Based on the re-appearance period (RP) at an observation station, Ramp et al.(2004) divided the ISWs into two types:Type-a and Type-b. Type-a ISWs arrive regularly at the same time every day, i.e., the RP is about 24 h, and Type-b ISWs arrive about one hour late every day, i.e., the RP is about 25 h. The discovery of the Types-a and b展开更多
The spatiotemporal features of submesoscale processes(SMPs) in the northeastern South China Sea(SCS) are analyzed based on a high-resolution simulation from 2009 to 2012. The simulation results show that the SMPs with...The spatiotemporal features of submesoscale processes(SMPs) in the northeastern South China Sea(SCS) are analyzed based on a high-resolution simulation from 2009 to 2012. The simulation results show that the SMPs with a vertical relative vorticity that matches the local planetary vorticity are ubiquitous in the upper ocean of the northeastern SCS. The SMPs distribution shows an asymmetry due to centrifugal instability, with stronger positive vorticity than negative vorticity. Meanwhile, the SMPs demonstrate an obvious seasonal variation. The SMPs are strong and active in winter but weak and inactive in summer. An investigation of the SMPs generation mechanisms reveals that flow straining and mixed layer depth account for this seasonal variation. The strong flow straining and deep mixed layer depth in winter favor the SMP generation via frontogenesis and mixed layer instability.展开更多
The rheological properties of South China Sea(SCS) crude oil were studied. A group of synthetic long-chain polymers, including octadecyl acrylate-maleic anhydride bidodecyl amide copolymer(VR-D),octadecyl acrylate-mal...The rheological properties of South China Sea(SCS) crude oil were studied. A group of synthetic long-chain polymers, including octadecyl acrylate-maleic anhydride bidodecyl amide copolymer(VR-D),octadecyl acrylate-maleic anhydride bioctadecyl amide copolymer(VR-O) and octadecyl acrylate-maleic anhydride phenly amide copolymer(VR-A), were employed to serve as viscosity reducers(VRs). Their performance was evaluated by both experimental and computational methodologies. The results suggest that the SCS crude oil has low wax content yet high resin and asphaltene contents, which lead to high viscosity through formation of association structures. Additionally, the SCS crude oil appears to be a pseudoplastic fluid showing linear shear stress-shear rate dependence at low temperature. Interestingly, it gradually evolves into a Newtonian fluid with exponential relationship between shear stress and shear rate at higher temperature. Synthetic VRs demonstrate desirable and effective performance on improvement of the rheological properties of SCS crude oil. Upon the introduction of 1000 ppm VR-O,which is synthesized by using octadecylamine in the aminolysis reaction, the viscosity of SCS crude oil is decreased by 44.2% at 15 °C and 40.2% at 40 °C. The computational study suggests significant energy level increase and shear stress decrease for VR-containing crude oil systems.展开更多
Tropical cyclone (TC) genesis over the South China Sea (SCS) during 1965-2004 was analyzed. The locations of TC genesis display evident seasonal changes, with the mean position of formation situated north of 15 °...Tropical cyclone (TC) genesis over the South China Sea (SCS) during 1965-2004 was analyzed. The locations of TC genesis display evident seasonal changes, with the mean position of formation situated north of 15 °N in summer (June-July-August) and south of 15 °N in autumn (September-October-November). The TC genesis in summer underwent dramatic interdecadal variations, with more and less TC frequency during 1965-1974/1995-2004 and 1979-1993, respectively. In contrast, a significant interannual variation of TC genesis with a period of ~4 years was observed in autumn. This study investigated the relationship of SCS TC genesis to the East Asian jet stream (EAJS) and the western North Pacific subtropical high (WNPSH) on an interdecadal time scale. Analysis and comparison of the impacts of the EAJS and the WNPSH on vertical wind shear changes indicate that changes in the WNPSH and EAJS intensity rather than EAJS meridional location are responsible for changes in TC genesis on an interdecadal time scale. Corresponding to a weaker EAJS, anomalous Rossby wave energy at upper levels displays equatorward propagation at midlatitudes and poleward propagation in the subtropics. This induces anomalous convergence and divergence of wave activity fluxes in East Asia around 30 °N and the SCS, respectively. The anomalous divergence of wave activity fluxes reduces easterlies at upper levels over the SCS, which is favorable to TC genesis.展开更多
Mesoscale eddies(MEs) in the South China Sea(SCS) simulated by a quasi-global eddy-resolving ocean general circulation model are evaluated against satellite data during 1993–2007. The modeled ocean data show more act...Mesoscale eddies(MEs) in the South China Sea(SCS) simulated by a quasi-global eddy-resolving ocean general circulation model are evaluated against satellite data during 1993–2007. The modeled ocean data show more activity than shown by the satellite data and reproduces more eddies in the SCS. A total of 345(428) cyclonic eddies(CEs) and 330(371) anti-cyclonic eddies(AEs) generated for satellite(model) data are identified during the study period, showing increase of ~24% and ~12% for the model data, respectively. Compared with eddies in satellite, the simulated eddies tend to have smaller radii, larger amplitudes, a slightly longer lifetime, faster movement and rotation speed, a slightly larger nonlinear properties(U/c) in the model. However, the spatial distribution of generated eddies appears to be inhomogeneous, with more CEs in the northern part of SCS and fewer AEs in the southern part. This is attributed to the exaggerated Kuroshio intrusion in the model because the small islands in the Luzon Strait are still not well resolved although the horizontal resolution reaches(1/10)°. The seasonal variability in the number and the amplitude of eddies generated is also investigated.展开更多
The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxid...The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ^(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ^(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ^(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.展开更多
The unique survey in December 1998 mapped the entire western boundary area of the South China Sea(SCS),which reveals the three-dimensional structure and huge volume transport of the swift and narrow winter western bou...The unique survey in December 1998 mapped the entire western boundary area of the South China Sea(SCS),which reveals the three-dimensional structure and huge volume transport of the swift and narrow winter western boundary current of the SCS(SCSwwbc) in full scale. The current is found to flow all the way from the shelf edge off Hong Kong to the Sunda Shelf with a width around 100 km and a vertical scale of about 400 m. It appears to be the strongest off the Indo-China Peninsula, where its volume transport reached over 20×10~6 m^3/s. The current is weaker upstream in the northern SCS to the west of Hong Kong. A Kuroshio loop or detached eddy intruded through the Luzon Strait is observed farther east where the SCSwwbc no more exists. The results suggest that during the survey the SCSwwbc was fed primarily by the interior recirculation of the SCS rather than by the"branching" of the Kuroshio from the Luzon Strait as indicated by surface drifters, which is likely a near-surface phenomenon and only contributes a minor part to the total transport of the SCSwwbc. Several topics related to the SCSwwbc are also discussed.展开更多
In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea(SCS) is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS se...In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea(SCS) is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS sea surface temperature(SST) have changed from warming to cooling since the late 1990 s. A heat budget analysis suggests that the warming of the surface mixed layer during 1984–1999 is primarily attributed to the horizontal heat advection and the decrease of upward long wave radiation, with the net surface heat flux playing a damping role due to the increase of upward latent and sensible heat fluxes. On the other hand, the cooling of the surface mixed layer during 2000–2009 is broadly controlled by net surface heat flux, with the radiation flux playing the dominant role. A possible mechanism is explored that the variation of a sea level pressure(SLP) over the North Pacific Ocean may change the prevailing winds over the SCS, which contributes to the change of the SST in the SCS through the horizontal heat advection and heat fluxes.展开更多
Ferromanganese nodules and crusts contain relatively high concentration of rare earth elements(REE) and yttrium(REY),with a growing interest in exploitation as an alternative to land-based REY resources.On the basis o...Ferromanganese nodules and crusts contain relatively high concentration of rare earth elements(REE) and yttrium(REY),with a growing interest in exploitation as an alternative to land-based REY resources.On the basis of comprehensive geochemical approach,the abundance and distribution of REY in the ferromanganese nodules from the South China Sea are analyzed.The results indicate that the REY contents in ferromanganese deposits show a clear geographic regularity.Total REY contents range from 69.1×10^(–6) to 2 919.4×10^(–6),with an average value of 1 459.5×10^(–6).Especially,the enrichment rate of Ce content is high,accounting for almost 60% of the total REY.This REE enrichment is controlled mainly by the sorption of ferromanganese oxides and clay minerals in the nodules and crusts.Moreover,the total REY are higher in ferromanganese deposits of hydrogenous origin than of diagenetic origin.Finally,Light REE(LREE) and heavy REE(HREE) oxides of the ferromanganese deposits in the study area can be classified into four grades: non-enriched type,weakly enriched type,enriched type,and extremely enriched type.According to the classification criteria of rare earth resources,the Xisha and Zhongsha platform-central deep basin areas show a great potential for these rare earth metals.展开更多
The upper-ocean responses to Typhoon Megi(2010)are investigated using data from ARGO floats and the satellite TMI.The experiments are conducted using a three-dimensional Princeton Ocean Model(POM)to assess the storm,w...The upper-ocean responses to Typhoon Megi(2010)are investigated using data from ARGO floats and the satellite TMI.The experiments are conducted using a three-dimensional Princeton Ocean Model(POM)to assess the storm,which affected the Northwest Pacific Ocean(NWP)and the South China Sea(SCS).Results show that the upwelling and entrainment experiment together account for 93% of the SST anomalies,where typhoon-induced upwelling may cause strong ocean cooling.In addition,the anomalous SST cooling is stronger in the SCS than in the NWP.The most striking feature of the ocean response is the presence of a two-layer inertial wave in the SCS—a feature that is absent in the NWP.The near-inertial oscillations can be generated as typhoon wakes,which have maximum flow velocity in the surface mixed layer and may last for a few days,after the typhoon's passage.Along the typhoon tracks,the horizontal currents in the upper ocean show a series of alternating negative and positive anomalies emanating from the typhoon.展开更多
This study investigates the structure and propagation of intraseasonal sea surface temperature(SST) variability in the South China Sea(SCS) on the 30–60-day timescale during boreal summer(May–September). TRMM-based ...This study investigates the structure and propagation of intraseasonal sea surface temperature(SST) variability in the South China Sea(SCS) on the 30–60-day timescale during boreal summer(May–September). TRMM-based SST, GODAS oceanic reanalysis and ERA-Interim atmospheric reanalysis datasets from 1998 to 2013 are used to examine quantitatively the atmospheric thermodynamic and oceanic dynamic mechanisms responsible for its formation. Power spectra show that the 30–60-day SST variability is predominant, accounting for 60% of the variance of the 10–90-day variability over most of the SCS. Composite analyses demonstrate that the 30–60-day SST variability is characterized by the alternate occurrence of basin-wide positive and negative SST anomalies in the SCS, with positive(negative) SST anomalies accompanied by anomalous northeasterlies(southwesterlies). The transition and expansion of SST anomalies are driven by the monsoonal trough–ridge seesaw pattern that migrates northward from the equator to the northern SCS. Quantitative diagnosis of the composite mixed-layer heat budgets shows that, within a strong 30–60-day cycle, the atmospheric thermal forcing is indeed a dominant factor, with the mixed-layer net heat flux(MNHF) contributing around 60% of the total SST tendency, while vertical entrainment contributes more than 30%. However, the entrainment-induced SST tendency is sometimes as large as the MNHF-induced component, implying that ocean processes are sometimes as important as surface fluxes in generating the30–60-day SST variability in the SCS.展开更多
Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underly...Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underlying sea surface in the mesoscale numerical model to simulate Typhoon Dujuan that moved across the South China Sea in 2003. The numerical results show that different SSTs near the typhoon center result in differences in the atmospheric wind field, indicating that the model has a fast and obvious response to SSTs. Different SST influences the intensity and track of Dujuan to some degree and has significant impacts on its precipitation and latent heat flux near the eye. The SST influence on Dujuan is mainly fulfilled by changing the latent heat flux between the ocean surface and the atmosphere above.展开更多
The best track data of tropical cyclones (TCs) provided by Regional Specialized Meteorological Center (RSMC) Tokyo for the South China Sea (SCS) from 1977 to 2007 are employed to study the spatiotemporal variations (f...The best track data of tropical cyclones (TCs) provided by Regional Specialized Meteorological Center (RSMC) Tokyo for the South China Sea (SCS) from 1977 to 2007 are employed to study the spatiotemporal variations (for a period of 12 hours) and the rapid (slow) intensification (RI/SI) of TCs with different intensity. The main results are as follows. (1) Over this period, the tropical storms (TSs) and severe tropical storms (STSs) mostly intensify or are steady while the typhoons (TYs) mostly weaken. The stronger a TC is initially, the more observation of its intensification and the less its variability will be; the more observation of its weakening is, the larger its variability will be. (2) The TC intensifies the fastest at 0000 UTC while weakening the fastest at 1200 UTC. (3) In the intensifying state, TSs, STSs, and TYs are mainly active in the northeastern, central-eastern, and central SCS respectively. The weakening cases mainly distribute over waters east off Hainan Island and Vietnam and west off the Philippines. Some cases of TSs and STSs weaken over the central SCS. (4) The RI cases form farther south in contrast to the SI cases. The RI cases are observed in regions where there are weaker vertical shear and easterly components at 200 hPa. The RI cases also have stronger mid-and lower-level warm-core structure and smaller radii of 15.4 m/s winds. The SI cases have slightly higher SST.展开更多
The northern slope region of the South China Sea(SCS) is a biological hot spot characterized by high primary productivity and biomasses transported by cross-shelf currents, which support the spawning and growth of com...The northern slope region of the South China Sea(SCS) is a biological hot spot characterized by high primary productivity and biomasses transported by cross-shelf currents, which support the spawning and growth of commercially and ecologically important fish species. To understand the physical and biogeochemical processes that promote the high primary production of this region, we conducted a cruise from June 10 and July 2, 2015. In this study, we used fuzzy cluster analysis and optimum multiparameter analysis methods to analyze the hydrographic data collected during the cruise to determine the compositions of the upper 55-m water masses on the SCS northern slope and thereby elucidate the cross-slope transport of shelf water(SHW) and the intrusions of Kuroshio water(KW). We also analyzed the geostrophic currents derived from acoustic Doppler current profiler measurements and satellite data. The results reveal the surface waters on the northern slope of the SCS to be primarily composed of waters originating from South China Sea water(SCSW), KW, and SHW. The SCSW dominated a majority of the study region at percentages ranging between 60% and 100%. We found a strong cross-slope current with speeds greater than 50 cms^(-1) to have carried SHW into and through the surveyed slope area, and KW to have intruded onto the slope via mesoscale eddies, thereby dominating the southwestern section of the study area.展开更多
基金supported by the 973 Project(no. 2007CB411705)the National Natural Science Foundations of China(no.40806019)+1 种基金the Key Laboratory of Marginal Sea Geology,Chinese Academy of Sciences (no.MSGL09-10)the Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences)project(no.TPR-2009-17)
文摘In the east coast Peninsular Malaysia region,sediments are transported by several rivers from the east Malaysia into the South China Sea estuary.In the vicinity of the five river estuaries core sediments were collected in order to investigate rare earth elements(REEs) profile.Core sediments were divided into strata of between 2 to 4 cm intervals and prepared for analyzing by ICP-AES.REE concentrations of 54.3 μg/gr at 24-26 cm in EC4 increased to 114.1 μg/gr at 20-22 cm in EC5.The measured concentration of LREEs and Fe normalized enrichment factors indicated that sediments were not enriched with light rare earth elements derived from effluents of anthropogenic activities.Results of the total concentration were used to establish baseline data in environmental pollution assessment and to develop the correlations between the Ce/Ce and Eu/Eu anomalies and the distribution patterns of some light rare earth elements(LREEs) and the heavy rare earth elements(HREEs).The chondrite-normalized ratios of REEs showed LREEs enrichment and flat HREE depletion.
基金The National Science and Technology Major Project of China under contract No.2016ZX05057015the National Natural Science Foundation of China under contract Nos 41376038 and 40406009+3 种基金the NSFC-Shandong Joint Fund for Marine Science Research Centers of China under contract No.U1606405the National Program on Global Change and Air-Sea Interaction of China under contract Nos GASI-03-01-01-02,GASI-02-IND-STSsum and GASI-IPOVAI-01-05the Public Science and Technology Research Funds Projects of Ocean of China under contract No.200905024the National Key Scientific Instrument and Equipment Development Projects of China under contract No.2012YQ12003908
文摘The South China Sea (SCS), in particular the northern SCS, is one of ocean areas where energetic internal solitary waves (ISWs)occur most frequently (Cai et al., 2012; Zheng, 2017). Based on the re-appearance period (RP) at an observation station, Ramp et al.(2004) divided the ISWs into two types:Type-a and Type-b. Type-a ISWs arrive regularly at the same time every day, i.e., the RP is about 24 h, and Type-b ISWs arrive about one hour late every day, i.e., the RP is about 25 h. The discovery of the Types-a and b
基金The National Key Research and Development Program of China under contract No.2017YFA0604103the National Basic Research Program(973 Program)of China under contract No.2014CB745003+1 种基金the National Natural Science Foundation of China under contract No.91628302the Startup Foundation for the Introducing Talent of the Nanjing University of Information Science and Technology under contract No.2243141601059
文摘The spatiotemporal features of submesoscale processes(SMPs) in the northeastern South China Sea(SCS) are analyzed based on a high-resolution simulation from 2009 to 2012. The simulation results show that the SMPs with a vertical relative vorticity that matches the local planetary vorticity are ubiquitous in the upper ocean of the northeastern SCS. The SMPs distribution shows an asymmetry due to centrifugal instability, with stronger positive vorticity than negative vorticity. Meanwhile, the SMPs demonstrate an obvious seasonal variation. The SMPs are strong and active in winter but weak and inactive in summer. An investigation of the SMPs generation mechanisms reveals that flow straining and mixed layer depth account for this seasonal variation. The strong flow straining and deep mixed layer depth in winter favor the SMP generation via frontogenesis and mixed layer instability.
基金financially supported by the Training Program of the Major Research Plan of the National Natural Science Foundation of China(grant no.91634112)the Natural Science Foundation of Shanghai(grant no.16ZR1408100)+2 种基金the Fundamental Research Funds for the Central Universities of China(grant no.22A201514010)the Open Project of State Key Laboratory of Chemical Engineering(SKL-Ch E-16C01)the institutional funds from the Gene and Linda Voiland School of Chemical Engineering and Bioengineering at Washington State University
文摘The rheological properties of South China Sea(SCS) crude oil were studied. A group of synthetic long-chain polymers, including octadecyl acrylate-maleic anhydride bidodecyl amide copolymer(VR-D),octadecyl acrylate-maleic anhydride bioctadecyl amide copolymer(VR-O) and octadecyl acrylate-maleic anhydride phenly amide copolymer(VR-A), were employed to serve as viscosity reducers(VRs). Their performance was evaluated by both experimental and computational methodologies. The results suggest that the SCS crude oil has low wax content yet high resin and asphaltene contents, which lead to high viscosity through formation of association structures. Additionally, the SCS crude oil appears to be a pseudoplastic fluid showing linear shear stress-shear rate dependence at low temperature. Interestingly, it gradually evolves into a Newtonian fluid with exponential relationship between shear stress and shear rate at higher temperature. Synthetic VRs demonstrate desirable and effective performance on improvement of the rheological properties of SCS crude oil. Upon the introduction of 1000 ppm VR-O,which is synthesized by using octadecylamine in the aminolysis reaction, the viscosity of SCS crude oil is decreased by 44.2% at 15 °C and 40.2% at 40 °C. The computational study suggests significant energy level increase and shear stress decrease for VR-containing crude oil systems.
基金sponsored by the National Basic Research Program of China (also called 973 Program, Grant Nos 2011CB403504 and 2010CB950400)National Natural Science Foundation of China (Grant Nos U0833602, U0733002 and 40906010)+2 种基金Hong Kong Croucher Foundation (Grant No 9220055)City University of Hong Kong (Strategic Research Grant No 7002717)Key Laboratory of Tropical Marine Environmental Dynamics (LED), Chinese Academy of Sciences (Grant No LED0804)
文摘Tropical cyclone (TC) genesis over the South China Sea (SCS) during 1965-2004 was analyzed. The locations of TC genesis display evident seasonal changes, with the mean position of formation situated north of 15 °N in summer (June-July-August) and south of 15 °N in autumn (September-October-November). The TC genesis in summer underwent dramatic interdecadal variations, with more and less TC frequency during 1965-1974/1995-2004 and 1979-1993, respectively. In contrast, a significant interannual variation of TC genesis with a period of ~4 years was observed in autumn. This study investigated the relationship of SCS TC genesis to the East Asian jet stream (EAJS) and the western North Pacific subtropical high (WNPSH) on an interdecadal time scale. Analysis and comparison of the impacts of the EAJS and the WNPSH on vertical wind shear changes indicate that changes in the WNPSH and EAJS intensity rather than EAJS meridional location are responsible for changes in TC genesis on an interdecadal time scale. Corresponding to a weaker EAJS, anomalous Rossby wave energy at upper levels displays equatorward propagation at midlatitudes and poleward propagation in the subtropics. This induces anomalous convergence and divergence of wave activity fluxes in East Asia around 30 °N and the SCS, respectively. The anomalous divergence of wave activity fluxes reduces easterlies at upper levels over the SCS, which is favorable to TC genesis.
基金The National Key Program for Developing Basic Science of China under contract No.2013CB956204the National Natural Science Foundation of China under contract Nos 41275084 and 41575084the Strategic Priority Research of the Chinese Academy of Science under contract No.XDA 11010304
文摘Mesoscale eddies(MEs) in the South China Sea(SCS) simulated by a quasi-global eddy-resolving ocean general circulation model are evaluated against satellite data during 1993–2007. The modeled ocean data show more activity than shown by the satellite data and reproduces more eddies in the SCS. A total of 345(428) cyclonic eddies(CEs) and 330(371) anti-cyclonic eddies(AEs) generated for satellite(model) data are identified during the study period, showing increase of ~24% and ~12% for the model data, respectively. Compared with eddies in satellite, the simulated eddies tend to have smaller radii, larger amplitudes, a slightly longer lifetime, faster movement and rotation speed, a slightly larger nonlinear properties(U/c) in the model. However, the spatial distribution of generated eddies appears to be inhomogeneous, with more CEs in the northern part of SCS and fewer AEs in the southern part. This is attributed to the exaggerated Kuroshio intrusion in the model because the small islands in the Luzon Strait are still not well resolved although the horizontal resolution reaches(1/10)°. The seasonal variability in the number and the amplitude of eddies generated is also investigated.
基金The Qingdao National Laboratory for Marine Science and Technology under contract No.QNLM2016ORP0210the National Natural Science Foundation of China under contract Nos 41306061,41473080 and 41376076the Scientific Cooperative Project by China National Petroleum Corporation and Chinese Academic of Sciences under contract No.2015A-4813
文摘The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ^(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ^(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ^(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.
基金The National Basic Research Program(973 Program)of China under contract Nos 2009CB421205 and 2011CB40350the National Key Research and Development Program of China under contract No.2016YFC1402607the State Oceanic Administration Special Grant of China under contract No.HY126-04-02-03
文摘The unique survey in December 1998 mapped the entire western boundary area of the South China Sea(SCS),which reveals the three-dimensional structure and huge volume transport of the swift and narrow winter western boundary current of the SCS(SCSwwbc) in full scale. The current is found to flow all the way from the shelf edge off Hong Kong to the Sunda Shelf with a width around 100 km and a vertical scale of about 400 m. It appears to be the strongest off the Indo-China Peninsula, where its volume transport reached over 20×10~6 m^3/s. The current is weaker upstream in the northern SCS to the west of Hong Kong. A Kuroshio loop or detached eddy intruded through the Luzon Strait is observed farther east where the SCSwwbc no more exists. The results suggest that during the survey the SCSwwbc was fed primarily by the interior recirculation of the SCS rather than by the"branching" of the Kuroshio from the Luzon Strait as indicated by surface drifters, which is likely a near-surface phenomenon and only contributes a minor part to the total transport of the SCSwwbc. Several topics related to the SCSwwbc are also discussed.
基金The National Natural Science Foundation of China under contract Nos 41476002 and 41506008the National Basic Research Program(973 Program)of China under contract No.2012CB955600
文摘In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea(SCS) is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS sea surface temperature(SST) have changed from warming to cooling since the late 1990 s. A heat budget analysis suggests that the warming of the surface mixed layer during 1984–1999 is primarily attributed to the horizontal heat advection and the decrease of upward long wave radiation, with the net surface heat flux playing a damping role due to the increase of upward latent and sensible heat fluxes. On the other hand, the cooling of the surface mixed layer during 2000–2009 is broadly controlled by net surface heat flux, with the radiation flux playing the dominant role. A possible mechanism is explored that the variation of a sea level pressure(SLP) over the North Pacific Ocean may change the prevailing winds over the SCS, which contributes to the change of the SST in the SCS through the horizontal heat advection and heat fluxes.
基金The National Natural Science Foundation of China under contract Nos 41376057,41306047,41676056the Spanish project SUBVENT under contract No.CGL2012-39524-C02
文摘Ferromanganese nodules and crusts contain relatively high concentration of rare earth elements(REE) and yttrium(REY),with a growing interest in exploitation as an alternative to land-based REY resources.On the basis of comprehensive geochemical approach,the abundance and distribution of REY in the ferromanganese nodules from the South China Sea are analyzed.The results indicate that the REY contents in ferromanganese deposits show a clear geographic regularity.Total REY contents range from 69.1×10^(–6) to 2 919.4×10^(–6),with an average value of 1 459.5×10^(–6).Especially,the enrichment rate of Ce content is high,accounting for almost 60% of the total REY.This REE enrichment is controlled mainly by the sorption of ferromanganese oxides and clay minerals in the nodules and crusts.Moreover,the total REY are higher in ferromanganese deposits of hydrogenous origin than of diagenetic origin.Finally,Light REE(LREE) and heavy REE(HREE) oxides of the ferromanganese deposits in the study area can be classified into four grades: non-enriched type,weakly enriched type,enriched type,and extremely enriched type.According to the classification criteria of rare earth resources,the Xisha and Zhongsha platform-central deep basin areas show a great potential for these rare earth metals.
基金supported by the National Key Basic Research and Development Plan(Grant No.2015CB953900)the National Natural Science Foundation of China(Grant No.41176005)+1 种基金the Public Science and Technology Research Funds Projects of the Ocean(Grant No.GYHY201105018)the China R&D Special Fund for Public Welfare Industry(GYHY 201306016)
文摘The upper-ocean responses to Typhoon Megi(2010)are investigated using data from ARGO floats and the satellite TMI.The experiments are conducted using a three-dimensional Princeton Ocean Model(POM)to assess the storm,which affected the Northwest Pacific Ocean(NWP)and the South China Sea(SCS).Results show that the upwelling and entrainment experiment together account for 93% of the SST anomalies,where typhoon-induced upwelling may cause strong ocean cooling.In addition,the anomalous SST cooling is stronger in the SCS than in the NWP.The most striking feature of the ocean response is the presence of a two-layer inertial wave in the SCS—a feature that is absent in the NWP.The near-inertial oscillations can be generated as typhoon wakes,which have maximum flow velocity in the surface mixed layer and may last for a few days,after the typhoon's passage.Along the typhoon tracks,the horizontal currents in the upper ocean show a series of alternating negative and positive anomalies emanating from the typhoon.
基金supported by the SOA Program on Global Change and Air–Sea Interactions (Grant No.GASI-IPOVAI03)the National Basic Research Program of China (Grant No.2014CB953902)+1 种基金the Natural Science Foundation of China (Grant Nos.91537103 and 41375087)the Priority Research Program of the Chinese Academy of Sciences (Grant Nos.QYZDY-SSWDQC018 and XDA11010402)
文摘This study investigates the structure and propagation of intraseasonal sea surface temperature(SST) variability in the South China Sea(SCS) on the 30–60-day timescale during boreal summer(May–September). TRMM-based SST, GODAS oceanic reanalysis and ERA-Interim atmospheric reanalysis datasets from 1998 to 2013 are used to examine quantitatively the atmospheric thermodynamic and oceanic dynamic mechanisms responsible for its formation. Power spectra show that the 30–60-day SST variability is predominant, accounting for 60% of the variance of the 10–90-day variability over most of the SCS. Composite analyses demonstrate that the 30–60-day SST variability is characterized by the alternate occurrence of basin-wide positive and negative SST anomalies in the SCS, with positive(negative) SST anomalies accompanied by anomalous northeasterlies(southwesterlies). The transition and expansion of SST anomalies are driven by the monsoonal trough–ridge seesaw pattern that migrates northward from the equator to the northern SCS. Quantitative diagnosis of the composite mixed-layer heat budgets shows that, within a strong 30–60-day cycle, the atmospheric thermal forcing is indeed a dominant factor, with the mixed-layer net heat flux(MNHF) contributing around 60% of the total SST tendency, while vertical entrainment contributes more than 30%. However, the entrainment-induced SST tendency is sometimes as large as the MNHF-induced component, implying that ocean processes are sometimes as important as surface fluxes in generating the30–60-day SST variability in the SCS.
基金Natural Science Foundation of China (U0733002, 40876009)Natural Science Foundation of Guangdong Province (8351030101000002)+1 种基金Science and Technology Planning Project of Guangdong Province (2008B030303025)Tropical Marine Meteorology Science Research Project
文摘Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underlying sea surface in the mesoscale numerical model to simulate Typhoon Dujuan that moved across the South China Sea in 2003. The numerical results show that different SSTs near the typhoon center result in differences in the atmospheric wind field, indicating that the model has a fast and obvious response to SSTs. Different SST influences the intensity and track of Dujuan to some degree and has significant impacts on its precipitation and latent heat flux near the eye. The SST influence on Dujuan is mainly fulfilled by changing the latent heat flux between the ocean surface and the atmosphere above.
基金Specialized Project for Forecasters, China Meteorological Administration 2011(CMAYBY2011-041)
文摘The best track data of tropical cyclones (TCs) provided by Regional Specialized Meteorological Center (RSMC) Tokyo for the South China Sea (SCS) from 1977 to 2007 are employed to study the spatiotemporal variations (for a period of 12 hours) and the rapid (slow) intensification (RI/SI) of TCs with different intensity. The main results are as follows. (1) Over this period, the tropical storms (TSs) and severe tropical storms (STSs) mostly intensify or are steady while the typhoons (TYs) mostly weaken. The stronger a TC is initially, the more observation of its intensification and the less its variability will be; the more observation of its weakening is, the larger its variability will be. (2) The TC intensifies the fastest at 0000 UTC while weakening the fastest at 1200 UTC. (3) In the intensifying state, TSs, STSs, and TYs are mainly active in the northeastern, central-eastern, and central SCS respectively. The weakening cases mainly distribute over waters east off Hainan Island and Vietnam and west off the Philippines. Some cases of TSs and STSs weaken over the central SCS. (4) The RI cases form farther south in contrast to the SI cases. The RI cases are observed in regions where there are weaker vertical shear and easterly components at 200 hPa. The RI cases also have stronger mid-and lower-level warm-core structure and smaller radii of 15.4 m/s winds. The SI cases have slightly higher SST.
基金supported by the National Basic Research Program of China (No. 2014CB441500)the National Natural Science Foundation of China (No. 41406021)
文摘The northern slope region of the South China Sea(SCS) is a biological hot spot characterized by high primary productivity and biomasses transported by cross-shelf currents, which support the spawning and growth of commercially and ecologically important fish species. To understand the physical and biogeochemical processes that promote the high primary production of this region, we conducted a cruise from June 10 and July 2, 2015. In this study, we used fuzzy cluster analysis and optimum multiparameter analysis methods to analyze the hydrographic data collected during the cruise to determine the compositions of the upper 55-m water masses on the SCS northern slope and thereby elucidate the cross-slope transport of shelf water(SHW) and the intrusions of Kuroshio water(KW). We also analyzed the geostrophic currents derived from acoustic Doppler current profiler measurements and satellite data. The results reveal the surface waters on the northern slope of the SCS to be primarily composed of waters originating from South China Sea water(SCSW), KW, and SHW. The SCSW dominated a majority of the study region at percentages ranging between 60% and 100%. We found a strong cross-slope current with speeds greater than 50 cms^(-1) to have carried SHW into and through the surveyed slope area, and KW to have intruded onto the slope via mesoscale eddies, thereby dominating the southwestern section of the study area.