Observed residual currents off the Changjiang （Yangtze） Rivermouth in wintertime of 1959 and 1982

Data taken in the two large-scale ocean investigations in China in winter 1959 and 1982 are used to analyze the residual current off the Changjiang (Yangtze) River mouth in this paper. The current in wintertime off the river mouth consist of the Changjiang runoff, wind-driven current, coastal current, density-driven current and Taiwan Warm Current (TWC). The TWC occurs in wintertime off the mouth. The surface TWC reaches only to the east side of Dinghai, then turns southeastward. The bottom TWC can flow to the area off the Changjiang mouth along west slop of the submerged river valley (SRV) and to the area off the Subei coast, The simulated currents by 3D model are basically consistent with the observed currents, although the model was run with climatological forces and the observations was done in episodic time manner.     

Observed residual currents off the Changjiang （Yangtze） Rivermouth in summertime of 1959 and 1982

Data taken in two large scale ocean observations in China in summer 1959 and 1982 were used to analyze the residual current off the Changjiang (Yangtze) River mouth. The currents at surface off the mouth in July 1959 and 1982 flow northeastward and eastward due to the river discharge, the current speed was larger in 1982 than in 1959. All the bottom currents flow landward due to baroclinic effect. The surface current was controlled by the river runoff and the Taiwan Warm Current (TWC). A return current at surface off the mouth was observed in September 1959. In general, the bottom currents were controlled by the TWC in most study area in addition to the runoff near the mouth. Although driven by 3-D model with the monthly averaged forces (river discharge, wind stress, baroclinic effect, open boundary water volume flux and tidal mixing) in August, the simulated circulations were basically consistent with the observed ones with episodic time manner.     

ON THE SOURCES OF THE TAIWAN WARM CURRENT FROM THE SOUTH CHINA SEA

Historical hydrographic data across several sections in the South China Sea (SCS) and Taiwan Strait have been reconsidered. The year-around existence of the South China Sea Warm Current (SCSWC) along the shelf break off the Guangdong coast and the seemingly year-around southwestward current to the east of SCSWC are both evident in the data. The data also showed that the northward current in the Taiwan Strait seemed to be the extension of SCSWC.A barotropic numerical model is employed to explain some of the observed features. Reasonable simulation of the circulation in the northeast part of SCS has been found.     

3-D BAROCLINIC NUMERICAL SIMULATION OF THE SOUTH CHINA SEA I. UPPER CIRCULATION

A three-dimensional baroclinic shelf sea model was employed to simulate the seasonal characteristics of the South China Sea (SCS) upper circulation. The results showed that: in summer, an anticyclonic eddy, after its formation between the Bashi Channel and Dongsha Islands in the northeastern SCS, moves southwestward until it disperses slowly. There exists a northward western boundary current along the east shore of the Indo-China Peninsula in the western SCS and an anticyclonic gyre in the southern SCS. But at the end of summer and beginning of autumn, a weak local cyclonic eddy forms in the Nansha Trough, then grows slowly and moves westward till it becomes a cyclonic gyre in the southern SCS in autumn. At the beginning of winter, there exists a cyclonic gyre in the northern and southern SCS, and there is a southward western boundary current along the east shore of the Indo-China Peninsula. But at the end of winter, an anticyclonic eddy grows and moves toward the western boundary after forming in the Nansha Trough. The eddy‘s movement induces a new opposite sign eddy on its eastern side, while the strength of the southward western boundary current gets weakened. This phenomenon continues till spring and causes eddies in the southern SCS.     

C haracteristics of turbulent kinetic energy dissipation rate and turbidity near the coast of East China Sea

The East China Sea(ECS) has a high suspended-sediment concentration because of the influence of the Changjiang River,indicated by high turbidity in the water.Considering the islands off the coast and the complex topography,and the strong influence of tides and wind,the coast off the ECS is a typical region with strong oceanic mixing processes.The changes in the dynamic processes near the bottom play an important role in the control of water turbidity.The turbulent kinetic energy dissipation rate(ε) is a parameter that shows the strength of ocean mixing.This is estimated based on a structure method using current velocity that is measured by a high-frequency Acoustic Doppler Current Profiler(ADCP) from a seafloor observatory in the ECS.The results indicate strong ocean mixing processes with a mean e value of 5.7×10~(-5) W/kg and distinct tidal variations in the dissipation rate.Conversely,the variation of the water turbidity leads to changes in the water dynamical structure near the bottom.Comparing the dissipation rate with the turbidity near the bottom boundary layer,we find that the high turbidity mimics strong ocean mixing.     

Response of Asian summer monsoon to CO2 doubling

Based on simulations of the IPCC 20C3M and SRES A1B experiments in ten coupled models, the Asian summer mon-soon (ASM) response to CO2 doubling and the different responses among models are examined. Nine models show the similar results that the weakening of land-ocean thermal contrast caused by the CO2 doubling contributes to a weaker large-scale ASM circulation. Further analysis in this study also shows that the major ASM components,such as the Somali cross-equatorial flow,the low level India-South China Sea monsoon trough,and the upper level tropical easterly jet stream, weaken as CO2 doubles.However,the ASM rainfall increases as a result of the increased moisture from the warmer Indian Ocean and the South China Sea, and the enhanced northward moisture transport over the ASM region.For the response of enhanced northward moisture transport over South Asia, the positive contribution of moisture content increase in the Indian Ocean is dominant and the negative contribution of the weaker mon-soon circulation is secondary at 850 hPa,but both have positive contribution to the total moisture transport along the East China coast.The paradox of the weaker ASM circulation and the increasing precipitation in CO2 doubling is confirmed.It is found that strengthening of northward moisture transport could intensify the precipitation and atmospheric heat source over the north Arabian Sea and East China,and result in enhanced southwesterly at 850 hPa as global warming occurs.All ten models show significant enhanced southwesterly response over the north Arabian Sea,and six of them show enhanced southwesterly response along the East China coast.     

The western South China Sea currents from measurements by Argo profiling floats during October to December 2007

The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. The trajectories of the Argo floats provided robust evidence that there does exist southward flowing current along the Vietnam coast. The southward current begins at about 15°N, 111°E, flowing along the 1 000 m isobath and extending to 5°N south. The estimated surface and parking depth velocities obtained from the floats suggest that this southward current can extend to 1 000 m depth. The mean surface velocity of the western boundary current is about 49 cm/s, with the maximum speed exceeding 100 cm/s occurring at 11.6°N, 109.5°E in the direction of 245°. The mean parking depth (1 000 m) velocity is 12–16 cm/s with the maximum speed of 36 cm/s occurring at 12.1°N, 109.7°E in the direction of 239°. The water mass analysis suggests that the Kuroshio surface water and NPIW are not apparent in the western boundary current although this time was the favored season for the Kuroshio intrusion into Luzon Strait. The mean geostrophic currents suggest that the Kuroshio intrusion into Luzon Strait during October to December 2007 is very weak, as most of the intruding water was carried eastward at 14°N near the western boundary and little flowed southward along the western boundary, providing an explanation for the absence of Kuroshio surface water and NPIW in the water mass analysis. There is a strong cyclonic circulation in the SSCS during this time, which induces a strong mixing in the western boundary companied by a homogeneous salinity layer between 300–600 m in the salinity vertical distribution. No reversal undercurrent occurred at the intermediate depth along the western boundary east of the Vietnam coast during October to December 2007.     

A NUMERICAL STUDY OF THE WINTERTIME CIRCULATION IN THE BOHAI AND HUANGHAI SEAS

The paper presents a numerical two-dimensional model (with a realistic sea basin and wind fields as exter nal forcing) to simulate the basic features of the wintertime circulation in the Bohai and Huanghai (Yellow) Seas (BHS) and to show how the circulation can be driven by wind. The main results can be summarized as follows (1) The basic features of the BHS wintertime circulation can be depicted by the wind-driven barotropi'c motion. (2) The traditionally named Huanghai Sea Warm Current (HSWC) is actually generated by the north wind field, at least in winter. (3) The southward coastal current off the Korean west coast plays a more significant role in the southern Huanghai Sea wintertime circulation than traditionally believed. (4) Though the coastal landform and bottom topography play important roles in the wintertime BHS circulation pattern, the wind is a primary forcing.     

On the Study of Wave Propagation and Distribution in the Global Ocean

Based on the simulation with SWAN wave model and data of ERA-Interim from 1979 to 2016, how the waves propagate globally and why swell pools distribute in the eastern ocean were investigated in this study. The simulation results show that waves from North Pacific and North Atlantic mainly propagate southeastward or southward and swells generated in Southern Ocean spread northeastward. The waves from high latitude regions spread along the east coast and encounter in the tropical Pacific and Atlantic to form swell fronts around equator and then turn eastward. As the weak wind field with numerous swell inflows, swell pools are generally located on the eastern side of the ocean basin, where the swell index S are greater than 0.9 calculated using ERA-20 C data for the period of 1981–2010. Another remarkable feature is that swell pools move southward and split into two parts in winter, while they move northward and merge together in summer.     

The main phosphorous sources in the Changjiang estuary

Analysis using historical data on the phosphate sources in Changjiang （Yangtze River） estuary show that phosphate was supplied equally from the east, south, west and north of the estuary. These sources include the Changjiang River, the Taiwan Warm Current （TWC）, a cyclone-type eddy, and the 32°N Upwelling, supplying different phosphates in different times, ways and intensities. The magnitude of their supplying phosphate concentration was related with the size in the order of the Changjiang River 〈 the TWC 〈 the 32°N Upwelling 〈 the cyclone-type eddy, and the duration of the supplying was： the Changjiang River 〉 the TWC 〉 the cyclone-type eddy 〉 the 32°N Upwelling. The four sources supplied a great deal of phosphate so that the phosphate concentration in the estuary was kept above 0.2 pmol/L in previous years, satisfying the phytoplankton growth. The horizontal and vertical distribution of the phosphate concentration showed that near shallow marine areas at 122°E/31°N, the TWC in low nutrient concentration became an upwelling through sea bottom and brought up nutrients from sea bottom to marine surface. In addition, horizontal distribution of phosphate concentration was consistent with that of algae： Rhizosolenia robusta, Rhizosolenia calcaravis and Skeletonema, which showed that no matter during high water or low water of Changjiang River, these species brought by the TWC became predominant species. Therefore, the authors believe that the TWC flowed from south to north along the coast and played a role in deflecting the Changjiang River flow from the southern side.     

Characteristics of Light Transmission in Summer and Winter and Its Relation on Sediment Transport in the East China Sea

Light transmission data collected from June to July 1987 and from February to March 1997 by the R/V Kexue 1 in the East China Sea were used to analyze its distribution characteristics and its relation to the sediment transport in this sea. Some results obtained were: (1) The Taiwan Warm Current flowing northwards seemed to be a barrier preventing suspended matter discharged from the Changjiang River Estuary from continuously moving southeastward and causing the suspended matter to flow along a path near 123°30′E in summer and 123°00′E in winter. (2) Suspended matter in the area adjacent to the Changjiang River Estuary could not be transported southward along the coast in summer due to opposing offshore currents including the Taiwan Warm Current flowing northward and the Changjiang Diluted Water turning northeastward. (3) The thermocline and temperature front bar suspended matter from crossing through.     

Seasonal variations of several main water masses in the southern Yellow Sea and East China Sea in 2011

The seasonal variations of several main water masses in the southern Yellow Sea (SYS) and East China Sea (ECS) in 2011 were analyzed using the in-situ data collected on four cruises. There was something special in the observations for the Yellow Sea Warm Current (YSWC), the Yellow Sea Cold Water Mass (YSCWM) and the Changjiang Diluted Water (CDW) during that year. The YSWC was confirmed to be a seasonal current and its source was closely associated with the Kuroshio onshore intrusion and the northerly wind. It was also found that the YSCWM in the summer of 2011 occupied a more extensive area in comparison with the climatologically-mean case due to the abnormally powerful wind prevailing in the winter of 2010 and decaying gradually thereafter. Resulting from the reduced Changjiang River discharge, the CDW spreading toward the Cheju Island in the summer of 2011 was weaker than the long-term mean and was confined to flow southward in the other seasons. The other water masses seemed normal without noticeable anomalies in 2011. The Yellow Sea Coastal Current (YSCC) water, driven by the northerly wind, flowed southeastward as a whole except for its northeastward surface layer in summer. The Taiwan Warm Current (TWC) was the strongest in summer and the weakest in winter in its northward movement. The Kuroshio water with an enhanced onshore intrusion in autumn was stable in hydrographic features apart from the seasonal variation of its surface layer.     

Characteristics of Light Transmission in Summer and Winter and Its Relation to Sediment Transport in the East China Sea

INTRODUCTIONTheSubeiShoalandtheChangjiangRiverestuarineareainthewestoftheHuanghaiandEastChinaSeasisoneofthemarginalseasintheworld ,wheresuspendedmatterisextremelyhigh .Here ,notonlyistheretheTaiwanWarmCurrentoneoftheKuroshio’sbranchesintheEastChinaSea,butalsotheHuanghaiCoastalCurrent,andChangjiangDilutedWater.Sothestrongmixingbetweenthecoastalandoffshorewaterscomplicatessuspendedmatterdistributioninthisarea.HowthesuspendedmatterdischargedfromtheChangjiangRiverandtheabandonedHuan…     

Numerical Study of Water and Suspended Matter Exchange Between the Yellow Sea and the East China Sea

INTRODUCTIONTheYellowSeaandtheEastChinaSea (ECS)aremarginalseasofthenorthwestPacificandhaveexpansivecontinentalshelves .TheuniqueandstrikingfeaturesoftheYellowSeaandtheECSarethattheyhavestrongtidalcurrent;aresubjecttostrongmonsooninfluence ;andreceiveinflowfromthebiggestriverinChina ,theChangjiangRiver ;andthatthefamouswesternboundarycurrent,theKuroshio ,passesthroughtheECS ,withitsbranchesintrudingupwardintothecontinentalshelfareas.Generallyspeaking ,thewaterexchangecapacityofthe…     

Abyssal Circulation in the Philippine Sea

The abyssal circulation in the Philippine Sea(PS)is investigated,with outputs from the Simple Ocean Data Assimilation version 2.2.4(SODA224).The deep-water currents in SODA224 are carefully evaluated,with sparse in situ observations in the North Pacific Ocean.In the upper deep layer(20003000 m)of the PS,a strong westward current,which originates from the Northeast Pacific Basin and enters the PS through the Yap-Mariana Junction,exists along 1114 N.This strong westward current bifurcates into two western boundary currents off the Philippines.The northward-flowing current flows out of the PS around 2021 N,whereas the southward-flowing current transports deep water from the northern hemisphere to the southern hemisphere.In the lower deep layer(30004500 m),the inflow water first flows northward to the east of the Western Mariana Basin and then turns westward at approximately 18 N.The inflow water mainly enters the Philippine Basin(PB),with a small part turning southward to constitute a weak cyclonic circulation.The water entering the PB mainly merges into a strong southward western boundary current in the south-ern PB.In the bottom layer(below 4500 m),both the northeast and northwest PB show single cyclonic gyres,whereas the south PB shows a single anticyclonic gyre.Moreover,comparisons with the observations indicate the possible existence of a cyclonic sense of circulation over the Philippine Trench.The current study provides the implications for future observations,which are needed to fur-ther investigate the temporospatial variations of the abyssal circulation in the PS on multiple scales.     

Study on suspended matter in seawater in the Southern Yellow Sea

Distribution of suspended matter in seawater in the Southern Yellow Sea is investigated in five regions: 1) the Northern Jiangsu bank, the highest TSM (total suspended matter) content region; 2) the high TSM content region off the Changjiang River mouth; 3) the high TSM content region off the Chengshan Cape; 4) the low TSM region off Haizhou Bay; 5) the central part of the Southern Yellow Sea, a low TSM content region. The vertical distribution of TSM is mainly characterized by a spring layer of suspended matter, written as “suspended-cline” whose genesis is related to storms in winter. In this paper, non-combustible components and grain sizes in suspended matter, relationship between suspended matter and bottom sediments, and salinity in seawater are described. Investigation result shows that, in this area, suspended matter comes mainly from resuspended bottom sediment and secondarily from present discharge loads from rivers and biogenic materials. Discharged sediments from the Huanghe River move around the Chengshan Cape and affect the northwestern region of this area. Sediments from the Changjiang River affect only the southern part and have little or no direct influence on the central deep region. Wave is the main factor affecting distribution of suspended matter. Water depth controls the critical depth acted on by waves. The cold water mass in the central region limits horizontal and vertical dispersions of terrigenous materials. Suspended matter here has the transitional properties of the epicontinental sea. Its concentration and composition are different from those of a semi-closed sea (such as the Bohai Sea) and those of the East China Sea outer continental shelf or those near oceanic areas.