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1.
An analytical study is made on the formation of the Cold Water Mass of the Yellow Sea (CWYS) and the relevant thermally driven circulation. The temperature and velocity field, obtained by solving the coupled equations of motion and heat conduction, show that, in summer, the CWYS has a horizontal cyclonic circulation (component) with vertical upwelling in the middle and downwelling at the edges, that the vertical convection (u-w components) occurs only within a thin layer near the thermocline. and that the deeper layer remains almost motionless. This current structure represents well the mechanisms responsible for the maintenance of the thermocline or CWYS during the wanner months. Comparisons between the theoretical and observed temperatures show very good qualitative and quantitative agreements for corresponding seasons.  相似文献   

2.
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.  相似文献   

3.
Study of horizontal and vertical distributions of the N/P(nitrogen versus phosphate)atom ratio in the northem South Yellow Sea showed that the ratio varied greatly in upper waters of the in-vestigated area and was always much greater than the theoretical Redfield ratio of 16:1 found below the thermocline zone.It was in general higher near the coast and lower in the central part.With increasing depth,the ratio became smaller and smaller.This distribution pattem is attributed to :1)the anthropo-genic influence of the surface N and P which makes the N/P ratio differ from the normal value;2)the easy adsorption of P on particles hinders P trasport to the central part;3)below the thermocline zone,the N and P mainly come from the remineralization of the sedimented phytoplankton residues which have almost the theoretical Redfield value and;4)the existence of the Yellow Sea Bottom Cold Water which inhibits the vertical exchange of the water.  相似文献   

4.
The concentration of suspended load can be determined by its linear relationship to turbidity. Our results present the basic distribution of suspended load in North Yellow Sea. In summer, the suspended load concentration is high along the coast and low in the center of the sea. There are four regions of high concentration in the surface layer: Penglai and Chengshantou along the north of the Shandong Peninsula, and the coastal areas of Lüshun and Changshan Islands. There is a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west. And there is a 2 mg/L contour at 124°E that separates the North Yellow Sea from regions of lower concentrations in the open sea to the west. The distribution features in the 10 m and bottom layer are similar to the surface layer, however, the suspended load concentration declines in the 10 m layer while it increases in the bottom layer. And in the bottom layer there is a low suspended load concentration water mass at the region south of 38°N and east of 123°E extending to the southeast. In general, the lowest suspended load concentration in a vertical profile is at a depth of 10 to 20 m, the highest suspended load concentration is in the bottom near Chengshantou area. In winter, the distribution of suspended load is similar to summer, but the average concentrations are three times higher. There are two tongue-shaped high suspended load concentration belt, one occurring from surface to seafloor, extends to the north near Chengshantou and the other invades north to south along the east margin of Dalian Bay. They separate the low suspended load concentration water masses in the center of North Yellow Sea into east and west parts. Vertical distribution is quite uniform in the whole North Yellow Sea because of the cooling effect and strong northeast winds. The distribution of suspended load has a very close relationship to the current circulation and wind-induced waves in the North Yellow Sea. Because of this, we have been able to show for the first time that the distribution of suspended load can be used to identify water masses.  相似文献   

5.
The distribution of the suspended sediment concentration (SSC) in the Bohai Sea, Yellow Sea and East China Sea (BYECS) is studied based on the observed turbidity data and model simulation results. The observed turbidity results show that (i) the highest SSC is found in the coastal areas while in the outer shelf sea areas turbid water is much more difficult to observe, (ii) the surface layer SSC is much lower than the bottom layer SSC and (iii) the winter SSC is higher than the summer SSC. The Regional Ocean Modeling System (ROMS) is used to simulate the SSC distribution in the BYECS. A comparison between the modeled SSC and the observed SSC in the BYECS shows that the modeled SSC can reproduce the principal features of the SSC distribution in the BYECS. The dynamic mechanisms of the sediment erosion and transport processes are studied based on the modeled results. The horizontal distribution of the SSC in the BYECS is mainly determined by the current-wave induced bottom stress and the fine-grain sediment distribution. The current-induced bottom stress is much higher than the wave-induced bottom stress, which means the tidal currents play a more significant role in the sediment resuspension than the wind waves. The vertical mixing strength is studied based on the mixed layer depth and the turbulent kinetic energy distribution in the BYECS. The strong winter time vertical mixing, which is mainly caused by the strong wind stress and surface cooling, leads to high surface layer SSC in winter. High surface layer SSC in summer is restricted in the coastal areas.  相似文献   

6.
The Yellow Sea Cold Water Mass(YSCWM),one of the most vital hydrological features of the Yellow Sea,causes a seasonal thermocline from spring to autumn.The diel vertical migration(DVM) of zooplankton is crucial to structural pelagic communities and food webs,and its patterns can be affected by thermocline depth and strength.Hence,we investigated zooplankton community succession and seasonal changes in zooplankton DVM at a fixed station in the YSCWM.Annual zooplankton community succession was affected by the forming and fading of the YSCWM.A total of 37 mesozooplankton taxa were recorded.The highest and lowest species numbers in autumn and spring were detected.The highest and lowest total densities were observed in autumn(14 464.1 inds./m3) and winter(3 115.4 inds./m3),respectively.The DVM of the dominant species showed obvious seasonal variations.When the YSCWM was weak in spring and autumn,most species(e.g.Paracalanus parvus,Oithona similis,and Acartia bifilosa) stayed above the thermocline and vertically migrated into the upper layer.Calanus sinicus and Aidanosagitta crassa crossed the thermocline and vertically migrated.No species migrated through the stratification in summer,and all of the species were limited above(P.parvus and A.crassa) or below(C.sinicus and Centropages abdominalis)the thermocline.The YSCWM disappeared in winter,and zooplankton species were found throughout the water column.Thus,the existence of thermocline influenced the migration patterns of zooplankton.Cluster analyses showed that the existence of YSCWM resulted in significant differences between zooplankton communities above and below the thermocline.  相似文献   

7.
Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass (YSCWM) and East China Sea Cold Eddy (ECSCE) areas is examined. Relationships between the thermocline and atmospheric and oceanic forcing were investigated using multiyear wind, Kuroshio discharge and air temperature data. Results show that: 1) In the YSCWM area, thermocline strength shows about 4-year and 16-year period oscillations. There is high correlation between summer thermocline strength and local atmospheric temperature in summer and the previous winter; 2) In the ECSCE area, interannual oscillation of thermocline strength with about a 4-year period (stronger in El Ni o years) is strongly correlated with that of local wind stress. A transition from weak to strong thermocline during the mid 1970s is consistent with a 1976/1977 climate shift and Kuroshio volume transport; 3) Long-term changes of the thermocline in both regions are mainly determined by deep layer water, especially on the decadal timescale. However, surface water can modify the thermocline on an interannual timescale in the YSCWM area.  相似文献   

8.
Seasonal variability of thermocline in the Yellow Sea   总被引：5，自引：0，他引：5  
Based on the MASNUM wave-tide-circulation coupled numerical model, seasonal variability of thermocline in the Yellow Sea was simulated and compared with in-situ observations. Both simulated mixed layer depth (MLD) and thermocline intensity have similar spatial patterns to the observations. The simulated maximum MLD are 8 m and 22 m, while the corresponding observed values are 13 m and 27 m in July and October, respectively. The simulated thermocline intensity are 1.2℃/m and 0.5℃/m in July and October, respectively, which are 0.6℃/m less than those of the observations. It may be the main reason why the simulated thermocline is weaker than the observations that the model vertical resolution is less precise than that of the CTD data which is 1 m. Contours of both simulated and observed thermocline intensity present a circle in general. The wave-induced mixing plays a key role in the formation of the upper mixed layer in spring and summer. Tidal mixing enhances the thermocline intensity. Buoyancy-driven m  相似文献   

9.
MODUrnONTheS0uthChinaSea(SCS)isabophalrnarginalbasinwhereEastAsiamonsoonsprevail.0bviousadjustInentSoftheupperocanoccurduetOthealtematingsurnxneandwintermonsoons.ThemostboohantaspchoflargeanlecurmtSintheSesaretheupperoonnicresponsetothemonsoons(Dale,l956).MostpreviousmrehesfocusedondiagnostiesandmodelingofsuffocecurmtS.Wwti(l96l)plotalsurfacentsbasedonshipdriflsintheNAGAReportNo.2anddescritaltheperiodicallysdri-annualreversingofwindsandrtinthisarea.Xuetal.(l982)calculatalthedy-naAn…  相似文献   

10.
Based on the MASNUM wave-tide-circulation coupled numerical model, the temperature structure along 35°N in the Yellow Sea was simulated and compared with the observations. One of the notable features of the temperature structure along 35°N section is the double cold cores phenomena during spring and summer. The double cold cores refer to the two cold water centers located near 122°E and 125°E from the depth of 30m to bottom. The formation, maintenance and disappearance of the double cold cores are discussed. At least two reasons make the temperature in the center (near 123°E) of the section higher than that near the west and east shores in winter. One reason is that the water there is deeper than the west and east sides so its heat content is higher. The other is invasion of the warm water brought by the Yellow Sea Warm Current (YSWC) during winter. This temperature pattern of the lower layer (from 30m to bottom) is maintained through spring and summer when the upper layer (0 to 30m) is heated and strong thermocline is formed. Large zonal span of the 35°N section (about 600 km) makes the cold cores have more opportunity to survive. The double cold cores phenomena disappears in early autumn when the west cold core vanishes first with the dropping of the thermocline position. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).  相似文献   

11.
Interannual variability of the southern Yellow Sea Cold Water Mass   总被引：2，自引：0，他引：2  
Temperature data collected in the sections of 34°N, 35°N and 36°N in August from 1975 through 2003 were analyzed using Empirical Orthogonal Function (EOF) to investigate interannual variability of the southern Yellow Sea Cold Water Mass (YSCWM). The first mode (EOF1) reveals variations of basin-wide thermocline depth, which is mainly caused by surface heating. The second mode (EOF2) presents fluctuations of vertical circulation, resulting mainly from interannual variability of cold front intensity. In addition, it is found that the upward extent of upwelling in the cold front is basically determined by wind stress curl and the zonal position of the warm water center in the southern Yellow Sea is correlated with spatial difference of net heat flux.  相似文献   

12.
The circulation of Yellow Sea Cold Water Mass(YSCWM) in the Southern Yellow Sea is investigated using a diagnostic 2D MITgcm model. The resolution of the computational grid is 900 m in the horizontal and 2 m in the vertical where an initial temperature distribution corresponding to a typical measured Yellow Sea Cold Water Mass was applied. The existence of YSCWM that causes fluid density difference, is shown to produce counter-rotating cyclonic horizontal eddies in the surface layer: the inner one is anti-cyclonic(clockwise) and relatively weaker(8–10 cm s-1) while the outer one is cyclonic(anti-clockwise) and much stronger(15–20 cm s-1). This result is consistent with the surface pattern observed by Pang et al.(2004), who has shown that a mesoscale anti-cyclonic eddy(clockwise) exists in the upper layer of central southern Yellow Sea, and a basin-scale cyclonic(anticlockwise) gyre lies outside of the anti-cyclonic eddy, based on the trajectories and drifting velocities of 23 drifters. Below the thermocline, there is an anti-cyclonic(clockwise) circulation. This complex current eddy system is considered to be capable of trapping suspended sediments and depositing them near the front between YSCWM and the coastal waters off the Subei coast, providing an explanation on the sediment depth and size distribution of mud patches in the Southern Yellow Sea. Moreover, sensitive test scenarios indicate that variations of bottom friction do not substantially change the main features of the circulation structure, but will reduce the bottom current velocity, increase the surface current velocity and weaken the upwelling around the frontal area.  相似文献   

13.
The Yellow Sea Warm Current (YSWC) is one of the principal currents in the Yellow Sea in winter. Former examinations on current activity in the Yellow Sea have not observed a stable YSWC because of the positioning of current meters. To further understand the YSWC, a research cruise in the southern Yellow Sea was carried out in the winter of 2006/2007. Five moorings with bottom-mounted acoustic Doppler current profilers (ADCP) were deployed on the western side of the central trough of the Yellow Sea. The existence and distributional features of the YSWC were studied by analyzing three ADCP moorings in the path of the YSWC in conjunction with conductivity-temperature-depth (CTD) data over the observed area in the southern Yellow Sea. The results show the following. (1) The upper layer of the YSWC is strongly influenced by winter cold surge; its direction and speed often vary along a south-north axis when strong cold surges arrive from the north. (2) The YSWC near the bottom layer is a stable northwest flowing current with a speed of 4 to 10 cm/s. By combining the analyses of the CTD data, we speculate that the core of the YSWC may lie near the bottom. (3) On a monthly average timescale, the YSWC is stably oriented with northward flow from the sea surface to the sea floor.  相似文献   

14.
A two-month seabed-mounted observation(YSG1 area) was carried out in the western Yellow Sea Cold Water Mass(YSCWM) using an RDI-300 K acoustic Doppler current profiler(ADCP) placed at a water depth of 38 m in late summer, 2012. On August 2012, Typhoon Bolaven passed east of YSG1 with a maximum wind speed of 20 m s-1. The water depth, bottom temperature, and profile current velocities(including u, v and w components) were measured, and the results showed that the typhoon could induce horizontal current with speed greater than 70 cm s-1 in the water column, which is especially rare at below 20 meters above bottom(mab). The deepening velocity shear layer had an intense shear velocity of around 10 cm s-1 m-1, which indicated the deepening of the upper mixed layer. In the upper water column(above 20 mab), westward de-tide current with velocity greater than 30 cm s-1 was generated with the typhoon's onshore surge, and the direction of current movement shifted to become southward. In the lower water column, a possible pattern of eastward compensation current and delayed typhoon-driven current was demonstrated. During the typhoon, bottom temperature variation was changed into diurnal pattern because of the combined influence of typhoon and tidal current. The passage of Bolaven greatly intensified local sediment resuspension in the bottom layer. In addition, low-density particles constituted the suspended particulate matter(SPM) around 10 mab, which may be transported from the central South Yellow Sea by the typhoon. Overall, the intensive external force of the Typhoon Bolaven did not completely destroy the local thermocline, and most re-suspended sediments during the typhoon were restricted within the YSCWM.  相似文献   

15.
A one-dimensional coupled pelagic-benthic box model for the Yellow Sea Cold Water Mass （YSCWM） is developed. The model is divided into three boxes vertically according to the depths of thermocline and euphotic layer. It simulates well the oligotrophic shelf ecosystem of the YSCWM considering effects of nutrients deposition and microbial loop. Main features of vertical structure of various variables in ecosystem of the YSCWM were captured and seasonal variability of the ecosystem was well reconstructed. Calculation shows that the contribution of microbial loop to the zooplankton can reach up to 60%. Besides, input of inorganic nutrients from atmospheric deposition is an important mechanism of production in upper layer of the YSCWM when stratified.  相似文献   

16.
A modified lower trophic ecosystem model (NEMURO) is coupled with a three-dimensional hydrodynamic model for an application in the central Yellow Sea. The model is used to simulate the horizontal distributions and annual cycles of chlorophyll-a and nutrients with results consistent with historical observations. Generally, during the winter background and spring bloom periods, the exchange with neighboring waters constitutes the primary sources of nutrients. Howerver, during the winter background period, the input of silicate from the layer deeper than 50 m is the most important source that contributes up to 60% to the total sources. During the spring bloom period, the transport across the thermocline makes significant contribution to the input of phosphate and silicate. During the post spring bloom period, the relative contribution of relevant processes varies for different nutrients. For ammonium, atmospheric deposition, excretion of zooplankton and decomposition of particulate and dissolved nitrogen make similar contributions. For phosphate and silicate, the dominant input is the transport across the thermocline, accounting for 62% and 68% of the total sources, respectively. The N/P ratio averaged annually and over the whole southern Yellow Sea is up to 51.8, indicating the potential of P limitation in this region. The important influence of large scale sea water circulation is revealed by both the estimated fluxes and the corresponding N/P ratio of nutrients across a section linking the northeastern bank of the Changjiang River and Cheju Island. During the winter background period, the input of nitrate, ammonium, phosphate and silicate by the Yellow Sea Warm Current is estimated to be 4.6×1010, 2.3×1010, 2.0×109 and 1.2×1010 mol, respectively.  相似文献   

17.
We used data from bottom trawl surveys to study the factors influencing the abundance of small yellow croaker, Larimichthys polyactis, in the southern Yellow Sea (SYS) and the East China Sea (ECS). The resource density index (RDI) was generally higher in summer and autumn than in spring and winter. RDIs were also significantly greater in the SYS than in the ECS in summer and autumn. The bottom water salinity and depth of spatial distribution of small yellow croaker was similar between the two areas in summer, but different in other seasons. Regression analysis suggested that environmental factors such as bottom water temperature, salinity, and depth influenced the RDIs in summer in these areas. Growth condition factor (GCF) in the two areas varied monthly and the croaker in the SYS grew more slowly than those in the ECS. This was likely due to the low bottom temperature of the Yellow Sea Cold Water Mass in summer and autumn or to higher human fishing pressure in the ECS. To ensure sustainable utilization of the croaker stocks in these regions, we recommend reducing the fishing intensity, increasing the cod-end mesh size, and improving the protection of juveniles.  相似文献   

18.
A two and a half layer oceanic model of wind-driven, thermodynamical general circulation is appliedto study the interannual oscillation of sea surface temperature (SST) in the South China Sea (SCS). Themodel consists of two active layers: the upper mixed layer (UML) and the seasonal thermocline, with themotionless abyss beneath them. The governing equations which include momentum, continuity and sea.temperature for each active layer, can describe the physics of Boussinseq approximation, reduced gravityand equatorial β-plane. The formulas for the heat flux at the surface and at the interface between twoactive layers are designed on the Haney scheme. The entrainment and detrainment at the bottom of theUML induces vertical transport of mass,momentum and heat, and couples of dynamic andthermodynamic effect.Using leap-frog integrating scheme and the Arakawa-C grid the model is forced bya time-dependent wind anomaly stress pattern obtained from category analysis of COADS. The numerical results indicate that t  相似文献   

19.
Surveys since 1959 showed that the dynamic basis of the East China Sea sectional circulation is the nearshore seawater horizontal divergence caused by wind on the surface compensated by Kuroshio subsurface water convergence caused by meridional current in the lower layer. Fish always tend to migrate along certain routes or stay in certain areas favorable for development of eggs, survival of larvae and living of adults. The movement of water masses supplies a very important driving force for marine animals migrating long distance. The lower part of the sectional circulation formed by the subsurface water of Kuroshio is not suitable for the aggregation of fish because of its lack of oxygen, and has therefore a driving influence on demersal fishes. This study of the sectional circulation influence on the distributions of some commercially important species in the East China Sea reveals a close relationship between the circulation and the movement of fish schools. The principal factors influencing zonal vertical circulation are the meridional vector of the Kuroshio lower layer and atmospheric circulation, referning here mainly to the subtropical high pressure in the Asia-Pacific area that causes surface divergence and lifts subsurface water from the bottom to the surface at the nearshore area. Some simple methods for estimating the intensity of the sectional circulation are, introduced for fishery forecasts and operations.  相似文献   

20.
The Chinese east coastal areas and marginal seas are foggy regions.The development of effective forecasting methodsrests upon a comprehensive knowledge of the fog phenomena.This study provides new observations associated with the sea fogsover the northwestern Yellow Sea by means of L-band radar soundings with a high vertical resolution of 30 m.The monthly tem-perature lapse rate,the Richardson Numbers,and the humidity show obvious seasonal variations in the lower level of the planetaryboundary layer (PBL) that are related to the onset,peak and end of the Yellow Sea fog season.The typical pattern of stratification forthe sea fog season in the northwestern Yellow Sea is that a stable layer of about 400 m thick caps a 150 m conditionally unstable layer.Besides,the differences between fogs and stratus clouds in terms of humidity,turbulence and temperature are analyzed,which is ofsignificance for sea fog forecast and detection by satellites.The thickness of the sea fogs varies in different stages of the fog season,and is associated with the temperature inversion.The numerical simulation proves that the seasonal variations obtained by the radarwell represent the situations over the Yellow Sea.  相似文献   

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