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1.
In order to clarify the structure of the strong tidal current at the Naruto Strait in the Seto Inland Sea of Japan, the sea-level values were observed in the strait and the current measurements were made with an Acoustic Doppler Current Profiler (ADCP).The tidal volume transports for M2 and S2 tides were about 74×103 and 26×103 m3 sec–1, respectively. The horizontal profile of the velocity at the phase of the strong tidal current compares favorably with a theoretical profile of the two-dimensional steady turbulent jet except for the side parts of the profile. Moreover, the entrainment rate of the surrounding water into the strong tidal jet was estimated from the difference of mass flux between two cross-sections at the strait, the entrainment rate and entrainment constant for both the northward and southward flows being about 1.3–2.5×10–4m–1 and about 0.03–0.05, respectively.  相似文献   

2.
Observations were made of time variations of carbon dioxide in seawater, pCO2, and in the atmosphere, PCO2, in the Seto Inland Sea of Japan. The pCO2 data showed well defined diurnal variation; high values at nighttime and low values during daylight hours. The pCO2 correlated negatively with dissolved oxygen. These results denote that the diurnal variation of pCO2 is associated with effects of photoplankton's activity in seawater. The pCO2 measured in the Seto Inland Sea showed higher values than the PCO2 during June to November, denoting transport of carbon dioxide from the sea surface to the atmosphere, and lower values during December to May, denoting transport of carbon dioxide from the atmosphere to the sea surface. The exchange rates of carbon dioxide were calculated using working formula given by Andriéet al. (1986). The results showed that the Seto Inland Sea gained carbon dioxide of 1.0 m-mol m–2 d–1 from the atmosphere in March and lost 1.7 m-mol m–2 d–1 to the atmosphere in August.  相似文献   

3.
Constant flows, as well as oscillatory tidal flow, play an important role in the long-term dispersion of water in the Seto Inland Sea. Two kinds of numerical model (1-line and 2-line models) of the Seto Inland Sea have been developed to determine the role of density-induced currents, one type of the constant flow, in water dispersion in the Inland Sea. The seasonal variations of temperature, salinity and density fields are simulated and the density-induced current field is predicted at the same time. It is found that the most appropriate value of the longitudinal eddy diffusion coefficient,K x, is 5×106–7×106 cm2sec–1. The value of the overall mean dispersion coefficient is of the order of 107cm2sec–1 (Hayami and Unoki, 1970). Consequently, it is suggested that 50–70% of the total dispersion in the Seto Inland Sea can be attributed to currents other than density-induced currents,i.e., tidal currents, tide-induced currents and wind-driven currents.In winter, both density and velocity fields, calculated using the 1-line model, satisfy the conditions for the existence of a coastal front in Kii Channel and in the eastern Iyo-nada.  相似文献   

4.
Time series of the vertical distribution of resuspended matter and bottom current were collected concurrently during summer at a few anchored stations in the Seto Inland Sea. The vertical distribution of resuspended matter was measured every hour for about one tidal cycle and the three components of current fluctuation were obtained at each sampling station. Current data at each sampling station show that the bottom is hydraulically smooth.Assuming that the averaged vertical distribution of resuspended matter for one tidal cycle shows a steady state distribution, the settling velocityWs of resuspended matter is estimated to be in the range of 1.2×10–2 to 5.7×10–2 cm sec–1 from analysis of the averaged distributions.The relation between the erosion rate and the bottom shear stress for this study area is investigated and is compared with that for other areas. The results show that the erosion of sediment in the Seto Inland Sea during summer occurs even due to the low bottom shear stress which is considered as almost smooth hydraulically.  相似文献   

5.
The concentrations of228Ra in surface waters of the Seto Inland Sea were determined. Surface waters from the central region of the Seto Inland Sea, Hiuchi Nada and Bingo Nada, contained concentrations of228Ra of 655–811 dpm/1000 l which were 100 times higher than those obtained in the Pacific Ocean. These high concentrations of228Ra must be supported by a228Ra flux from the bottom sediment. The lower limit of this flux was estimated to be more than 0.16 dpm cm–2 y–1. The228Ra concentrations decreased markedly from central regions of the Seto Inland Sea to about 18 dpm/1000 l in the Kii and the Bungo Channels as salinity increased. Using a box model and the228Ra data, the mean residence time of sea water in the Seto Inland Sea with respect to the exchange with the open ocean water was estimated to be less than 10 y, and the most probable value is the order of several years.  相似文献   

6.
Heat and salt balances in the Seto Inland Sea   总被引：1，自引：0，他引：1  
Seasonal variations of heat and salt balances are estimated in the Seto Inland Sea with the use of a numerical experiment.The surface effect is dominant with respect to the heat balance. In spring, however, the effect of the horizontal heat transport is the same as or greater than that of the surface heating (or cooling). Annual mean heat transport is 85 cal cm–2 day–1 (356 J cm–2 day–1) which is supplied from the open ocean and lost through the sea surface in the Inland Sea as a whole. Because of the shallow water depth, heat is supplied through the surface and carried out by the horizontal heat transport in Hiuchi- and Bingo-nada in the annual mean. The heat transport has the opposite sense to that in the whole Seto Inland Sea and annual mean transport is negative (–10 cal cm–2 day–1,i.e., –42 J cm–2 day–1).The salt balance is primarily controlled by the river discharge and the surface effect (precipitation) in June and July. In the other months, the effects of horizontal salt transport, of river inflow and of sea surface exchange (especially of the evaporation in autumn) are comparable to each other. In the Bungo Channel the river effect is relatively small. Osaka Bay and the Kii Channel are characterized by a smaller surface effect.Contribution No. 446 from Tohoku Regional Fisheries Research Laboratory.  相似文献   

7.
To analyse material transport in inland seas, a horizontal two-dimensional dispersion equation is derived, and the dispersion coefficient due to the combined effect of vertical turbulent mixing and vertical shear of both a steady current and a tidal current is studied. In the present study, the assumption that velocity is uniform in horizontal planes is not necessary, and velocity has a free vertical profile; thus the dispersion coefficient formulated is general, and is represented by a tensor of the second order. The properties of the dispersion coefficient in the horizontal two-dimensional dispersion model are also investigated, and it is shown that the time-averaged dispersion coefficient due to the tidal current over a tidal period is approximately half that due to the steady current, if the velocity amplitude and the vertical profile of the tidal current are the same as those of the steady current (a similar result was presented byBowden (1965) for horizontal one-dimensional models). Finally, the dispersion coefficient in Hiuchi-Nada (Hiuchi Sound) in the central part of the Seto Inland Sea is evaluated by using the model. The values of the dispersion coefficient in that region range from 103 cm2 s–1 to 105 cm2 s–1 when vertical turbulent diffusivity is taken to be 50 cm2 s–1.  相似文献   

8.
In the Suo-Nada area of the Seto Inland Sea, Japan, sedimentation rates and the sedimentary record of anthropogenic metal loads were determined by combining the Pb-210 dating technique with heavy metal analysis of the sediments. The sedimentation rates vary from 0.11 to 0.27 g cm–2 yr–1. Lower sedimentation rates were observed in the eastern part of the basin which is characterized by a bottom with sand and gravel, and fast tidal currents.Anthropogenic and natural loads of copper and zinc into the sediments are 34 and 326, and 65 and 375 ton yr–1, respectively. The anthropogenic loads are fairly low compared with those of the other main areas of sediment accumulation in the Seto Inland Sea. The highest level of zinc and copper pollution was observed in the western part of the basin because of waste discharge from an old and big ironworks outside basin since the early 1900's.  相似文献   

9.
The metal load into sediments and the change in the sedimentary environment of Osaka Bay in the Seto Inland Sea have been studied through geochemical analysis of core sediments, using both Pb-210 dating and a selective chemical leaching technique. Analytical results from a 6-m core of sediment show that copper and zinc pollution started in the late 1800's and the present enrichment ratios of copper and zinc, relative to background levels (20 mg kg–1 for Cu and 94 mg kg–1 for Zn), are 2.8 and 4.1, respectively. The present anthropogenic copper and zinc loads into Osaka Bay sediments, are 47 and 368 ton yr–1, while natural copper and zinc loads are 40 and 186 ton yr–1, respectively. Osaka Bay sediment at the present day is considered to be seriously polluted by zinc, now. The vertical profiles of copper and zinc in four successively separated fractions (10% acetic acid soluble fraction: F-HAC, 0.1M hydrochloric acid-soluble fraction: F-HCl, hydrogen peroxide-soluble fraction: F-H2O2 and hydrofluoric acid-soluble fraction: F-HF) from the core sediments indicate that enrichments of copper and zinc in the upper layer of the sediment are dependent on increases in the metal contents of the F-HAC, F-HCl and F-H2O2 fractions. Copper in F-HAC, and zinc in F-HAC and F-HCl, seem to be of anthropogenic origin.Results of sequential studies of the whole Seto Inland Sea can be summarized as follows: At the present time, the sedimentary loads of copper and zinc over the whole Seto Inland Sea area are 630 and 3,500 ton yr–1, respectively, while the natural and anthropogenic loads are 320 and 310 ton yr–1 for copper and 1,800 and 1,700 ton yr–1 for zinc, respectively.  相似文献   

10.
We observed tidal currents, turbulent energy dissipation and water column stratification at the entrance of a narrow strait (Neko Seto) in the Seto Inland Sea, Japan, using a free-falling turbulent microstructure profiler (TurboMAP) and acoustic Doppler current profiler (ADCP). The variation in turbulent energy dissipation at the entrance of the strait was not at quarter-diurnal frequency but at semi-diurnal frequency; turbulent energy dissipation was enhanced during the ebb tide, although it was moderate during the flood tide. This result is consistent with the results of Takasugi (1993), which showed the asymmetry of tidal energy loss during a semidiurnal tidal cycle using control volume analysis. It is suggested that significant turbulent energy dissipation is generated in the strait, which influences the properties of water outside the strait when tidal currents flow out from the strait.  相似文献   

11.
Numerical study of baroclinic tides in Luzon Strait   总被引：6，自引：1，他引：5  
The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional tide model driven by four principal constituents, O1, K1, M2 and S2, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19 GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%). The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal (O1 and K1) and semidiurnal (M2) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m−1 emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally, which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS. The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is O(10−7) W kg− 1 and the turbulence diffusivity is O(10−3) m2s−1, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the SCS waters.  相似文献   

12.
In order to assess the roles of Fe and Cu in outbreaks ofChattonella antiqua red tide, concentrations of these metals in the surface seawater were monitored around the Ie-shima Islands in the Seto Inland Sea during the summers of 1986–1988. Bioassay of the surface seawater with respect to Fe and Cu was also conducted using a cultured strain ofC. antiqua.Concentrations of Fe and Cu in the filtered seawater (FeF and CuF) were in the range of 3.9–10.0 and 9.3–11.2 nM, respectively. The bioassay with respect to Fe revealed that Fe at the surface layer was usually insufficient to support the maximum growth rate ofC. antiqua, except whenC. antiqua was dominant in the field. However, correlations between FeF and the growth rate of the control cultures (Fe, EDTA=not enriched; N, P, B12=enriched at optimum levels) were not apparent, probably because FeF did not reflect the concentration of available Fe.The bioassay with respect to Cu was coupled with the CuF values obtained. The results indicated that Cu at the surface layer was detoxified by complexation with natural organic ligand(s), and that pCu (=minus log of cupric ion activity) was 11.5–11.7, optimum for the growth ofC. antiqua, throughout the survey period. It is suggested that Fe, but not Cu, is a potentially important factor in regulating the natural populations ofC. antiqua in the Seto Inland Sea.  相似文献   

13.
The long-term mean (31-year mean) surface heat fluxes over the Japan Sea are estimated by the bulk method using the most of the available vessel data with the resolution of 1o×1o. The long-term annual mean net heat flux is about –53 W m–2 (negative sign means upward heat flux) with the annual range from 133 W m–2 in May to –296 W m–2 in December. The small gain of heat in the area near Vladivostok seems to indicate the existence of cold water flowing from the north. In that area in winter, the mean loss of heat attains about 200 W m–2, and the Bowen's ratio is over the unity. The largest insolation occurs in May in the Japan Sea, and the upward latent heat flux becomes the largest in November in this area. The heat flux of Haney type is also calculated, and the result, shows that the constantQ 1 has the remarkable seasonal and spatial variation, while the coefficientQ 2 has relatively small variation throughout all seasons. Under the assumption of constant volume transport of 1.35×106 m3s–1 through the Tsugaru Strait, the long-term averages of the volume transport through the Tsushima and Soya Straits are estimated to be about 2.20 and 0.85×106 m3s–1 from the result of the mean surface heat flux, respectively.  相似文献   

14.
内潮耗散与自吸-负荷潮对南海潮波影响的数值研究   总被引：1，自引：0，他引：1  
利用非结构三角形网格的FVCOM海洋数值模式,在其传统二维潮波方程中加入参数化的内潮耗散项和自吸-负荷潮项,计算了南海及其周边海域的M_2、S_2、K_1和O_1分潮的分布。与实测值的比较表明,引入这两项对模拟准确度的提高有明显效果。根据模式结果本文计算分析了研究海域的潮能输入和耗散。能量输入计算表明,能通量是潮能输入的最主要构成部分,通过吕宋海峡断面进入南海的M_2和K_1分潮能通量分别为38和29GW;半日周期的自吸-负荷潮能量输入以负值居多,而全日周期的自吸-负荷潮能量输入以正值居多,因而自吸-负荷潮减弱了南海的半日潮,并加强了南海的全日潮。引潮力的作用也减弱了半日潮而加强了全日潮,但其作用要小于自吸-负荷潮。潮能耗散的分析显示底摩擦耗散在沿岸浅水区域起主导作用,内潮耗散则主要发生在深水区域。内潮耗散的最大值出现在吕宋海峡,且位于南海之外的海峡东部的耗散量大于位于南海之内的海峡西部的耗散量。对M_2和K_1分潮吕宋海峡的内潮耗散总值分别达到16和23GW。  相似文献   

15.
The physical and chemical variability of the water column at subtidal station of an estuary in the Seto Inland Sea, Japan, was studied over a 24-hour period during a spring tide (tidal range ca. 2 m) in May 1995. Surface water and several depths through the water column were monitored every one and two hours, respectively. At each occasion, water temperature, salinity and dissolved oxygen concentration were measured and water samples were collected for the determination of nutrients and suspended particulate matter (SPM). Disruptive changes in the physical and chemical characteristics of the water was produced by the tidal cycle and the mixing of water masses of different origin. These changes were highly significant both spatially and temporally, yet with varying effects on physical parameters, nutrients and the different components of SPM. Significant differences in nutrient concentrations were also observed when the data-set was divided into ebb and flood components, irrespective of the depth. Nitrate and nitrite rose to 1.8 times higher during the flood. Spatial differences of SPM were less marked than those of nutrients, only particulate organic carbon (POC) being significantly higher at the surface than in the intermediate and the lower layer. Both POC and pheopigment concentrations increased markedly through the water column, being highest shortly before the lower low tide. In contrast, suspended solid (SS) content increased sharply after the lower low tide (>40 mg l−1) and this coincided with a marked decrease of the C/SS content (<20 mg g−1). The lagtime between POC and SS tidal transport was caused by particle resuspension from the exposed intertidal sediments as the tidal level rose, and particle transport selection in relation to the tidal state. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

16.
The strong tidal current (tidal jet) in straits generates tidal vortices with a scale of several kilometers. The role of the vortices in material transport was investigated in the Neko Seto Sea, located in the western part of the Seto Inland Sea of Japan. A clockwise vortex with a diameter of about 0.8 km was observed in Nigata Bay (lying between two straits, the Neko Seto Strait and the Meneko Seto Strait). It was concluded that the clockwise vortex was the tidal vortex which was generated by the tidal jet in the Meneko Seto Strait. The vortex moved into the bay with the tide, but tended to stay on the sand bank in the bay. It was confirmed by current measurement with an ADCP and turbidity measurement that the secondary convergent flow was generated in the bottom layer of the vortex. This secondary flow seemed to contribute to the formation of the sand bank. It was suggested that tidal vortices may play an important role in the sediment transport and formation of topography in and around straits.  相似文献   

17.
Long-term current measurements were carried out near the Soya Strait in the Okhotsk Sea during a period from February 1980 to September 1982. The data were divided into five segments, each being 150 days long, and the tidal ellipse parameters of major axis, minor axis, orientation, and phase for the four major constituents (M2, S2, K1 and O1 tides) were calculated at each segment. The major axis of the mean tidal ellipse averaged over five segments was 29.9 cm sec–1 for O1 tide, 28.3 cm sec–1 for K1 tide, 10.4 cm sec–1 for M2 tide, and 3.7 cm sec–1 for S2 tide. The phase and orientation of the tidal ellipse were much stable. But, the root mean square deviations of the major axis reached 20% of the mean values for all four constituents. The tidal currents estimated from the sea level records at Wakkanai and Esashi along the Hokkaido coast in the Okhotsk Sea show that their amplitudes and phases are in good agreement with the observed ones for all four constituents.  相似文献   

18.
A three-dimensional hydrodynamic model has been developed to simulate water mass circulation in estuarine systems. This model is based on the primitive equation in Cartesian coordinates with a terrain-following structure, coupled with a Mellor–Yamada 2.5 turbulence scheme. A fractional-step method is applied and the subset of equations is solved with finite volume and finite element methods. A dry–wet process simulates the presence of the tidal flat at low water. River inputs are introduced using a point-source method. The model was applied to a partially mixed, macrotidal, temperate estuary: Southampton Water, UK. The model is validated by comparisons with sea surface elevation, ADCP measurements and salinity data collected in 2001. The mean spring range 2(M2 + S2) and the mean neap range 2(M2 − S2) are modelled with an error relative to observation of 12 and 16%, respectively. The unique tidal regime of the system with the presence of the ‘young flood stand’ corresponding to the slackening conditions occurring at mid flood and ‘double high water’ corresponding to an extension of the slackening conditions at high tide is accurately reproduced in the model. The dynamics of the modelled mean surface and bottom velocity closely match the ADCP measurements during neap tides (rms of the difference is 0.09 and 0.01 m s−1 at the bottom and at the surface, respectively), whereas at spring the difference is greater (rms of the difference is 0.25 and 0.20 m s−1 at bottom and surface, respectively). The spatial and temporal variation of the degree of stratification as indicated by salinity distributions compares well with observations.  相似文献   

19.
Surface samples of sea water collected in the Seto Inland Sea were analyzed for232Th and228Th. The concentrations of232Th were generally less than 2 dpm/1,0001 and these values are probably an upper limit for the232Th concentration in surface waters of the Seto Inland Sea. The228Th concentrations ranged between 4.2 to 42.3 dpm/1,0001. Remarkable seasonal and temporal variations in228Th concentrations were found, in comparison with the minimal variations in228Ra concentrations reported previously. The activity ratios of228Th/228Ra were about 0.18 in the southern part of the Kii and the Bungo Channels, and decreased markedly from the open ocean toward the central region of the Seto Inland Sea. The average value of the228Th/228Ra ratio in the central region of the Seto Inland Sea was 0.032±0.020. This suggests that removal residence time of228Th can be estimated to be about 34±22 days in surface waters of the Seto Inland Sea.  相似文献   

20.
We adopt a parameterized internal tide dissipation term to the two-dimensional (2-D) shallow water equations, and develop the corresponding adjoint model to investigate tidal dynamics in the South China Sea (SCS). The harmonic constants derived from 63 tidal gauge stations and 24 TOPEX/Poseidon (T/P) satellite altimeter crossover points are assimilated into the adjoint model to minimize the deviations of the simulated results and observations by optimizing the bottom friction coefficient and the internal tide dissipation coefficient. Tidal constituents M2, S2, K1 and O1 are simulated simultaneously. The numerical results (assimilating only tidal gauge data) agree well with T/P data showing that the model results are reliable. The co-tidal charts of M2, S2, K1 and O1 are obtained, which reflect the characteristics of tides in the SCS. The tidal energy flux is analyzed based on numerical results. The strongest tidal energy flux appears in the Luzon Strait (LS) for both semi-diurnal and diurnal tidal constituents. The analysis of tidal energy dissipation indicates that the bottom friction dissipation occurs mainly in shallow water area, meanwhile the internal tide dissipation is mainly concentrated in the LS and the deep basin of the SCS. The tidal energetics in the LS is examined showing that the tidal energy input closely balances the tidal energy dissipation.  相似文献   

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