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1.
The seasonal variation of water temperature in the Seto Inland Sea, Japan is examined using data analysis and numerical experiments and is shown to be controlled by heat exchange through the sea surface and horizontal heat dispersion from the Pacific Ocean. The average water temperature goes down from the Pacific Ocean to the center of the Seto Inland Sea indicating that 4.0 to 6.0×1015 cal day?1 (1.6 to 2.5×1016 joule day?1) of heat is transported from the Pacific Ocean to the Seto Inland Sea and is lost through the sea surface. The amplitude of seasonal variation of water temperature is large at the center of the Seto Inland Sea and the maximum water temperature is reached first at Bisan Straits and last at Iyo-Nada.  相似文献   

2.
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   

3.
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   

4.
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   

5.
The tidal volume transport in the Seto Inland Sea is calculated. The cross-section where the volume transport of the M2 tide is zero, is located around the western part of Bisan Strait. The tidal energy dissipation of the M2 tide by friction is 6.30×1016 ergs s–1 in the Seto Inland Sea. The quality factorQ for the M2 tide is 20.2. The total energy dissipation of the M2, S2, K1 and O1 tides is 7.99×1016 ergs s–1.  相似文献   

6.
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   

7.
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   

8.
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   

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 have observed the temporal variation of oxygen deficient water with short time scale (less than a few days) in the central area of Ohmura Bay, Kyushu, Japan, in summer, 1995 and 1996. The vertical profiles of temperature were similar to those of dissolved oxygen. We noticed a linear relation between temperature and dissolved oxygen in the bottom layer, and applied the T-DO relation to estimate the net oxygen consumption rate, rather than direct evaluation of the advection and diffusion. Oxygen consumption rate just above the bottom was estimated to be about 0.21 g O2 m–3day–1 in July 1995, and about 0.28 g O2 m–3day–1 in August 1996. The net oxygen consumption rate estimated for the bottom layer below the second thermocline was about 0.61 g O2 m–3day–1 with variability from 0.55 to 0.66 g O2 m–3day–1 during July 25 to 29, 1995. This is was about 0.64 g O2 m–3day–1 with variability from 0.18 to 1.4 g O2 m–3day–1 during August 22 to 30, 1996. The net oxygen consumption rates are about half of those measured with a closed system in the Seto Inland Sea.  相似文献   

11.
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   

12.
Prominent coastal upwelling and downwelling events due to Ekman transport were observed during the period from 14 to 18 August 1983 along the Misaki Peninsula in the Seto Inland Sea, Japan. The coastline of the Misaki Peninsula is aligned approximately in an ENE-WSW direction. When an ENE wind continued blowing for about two days, the warm water in the upper layer was pushed offshore and cold water in the lower layer upwelled along the peninsula. The estimated upwelling speed 3 m below the sea surface was 0.032 cm sec–1. On the other hand, when a WSW wind continued blowing for about two days the warm water in the upper layer sank into the lower layer along the peninsula. The estimated downwelling speed 3 m below the sea surface was 0.080 cm sec–1. The time lag between the variations of the alongshore wind and offshore current was about 0.5 days.  相似文献   

13.
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   

14.
Sedimentation rates were determined with the210Pb technique in six sediment cores from Harima Nada (Harima Sound), Seto Inland Sea. The rate of deposition varies from 0.11 g cm–2y–1 in the northern part to 0.33 g cm–2 y–1 in the southern part of the basin. A marked increase in copper and zinc content was observed above a depth in the core corresponding to about 1900 A.D. as a result of increasing human activities. Anthropogenic input of copper and zinc decreased slightly after 1970. Natural background levels of copper and zinc in the sediment in this sound are 11–16 ppm and 100–120 ppm, respectively. The total amounts of anthropogenic copper and zinc in the sediments were estimated to be 110–180g cm–2 and 610–1,280g cm–2, respectively. These values constitute 40–50% of the total sedimentary input of copper and zinc in the sediments since about 1900 A.D.  相似文献   

15.
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   

16.
In the Hiuchi-Nada area of the Seto Inland Sea, Japan, sedimentation rates were determined with the Pb-210 technique, and heavy metals in sediments were also analyzed. Sediments were collected in twelve short sediment cores and a long sediment core, using 1-m and 6-m gravity corers.The sedimentation rates vary from 0.14 to 0.31 g cm–2yr–1. The highest sedimentation rate was observed in the central part of the area, while lower sedimentation rates were observed in the eastern part.In Hiuchi-Nada, a remarkable increase in copper and zinc contents is noticeable as early as the 1800's. Over the past 240 years a copper smelter at the south-western side of this area has been causing serious pollution of the sediment. Now, anthropogenic copper and zinc loads into the sediment are 123 and 376 ton yr–1 compared to natural copper and zinc loads of 82 and 401 ton yr–1, respectively. The highest level of copper and zinc pollution was observed in the 1960's, when the relative enrichments above background values (copper; 19 and zinc; 93 mg kg–1) were 5.5 and 2.8, respectively.  相似文献   

17.
The horizontal and vertical distributions of manganese in sea water, interstitial water and sediments in the Hiro Bay, Seto Inland Sea, Japan, have been investigated. The outflow from a pulp mill is the primary source of manganese in this bay. The industrial waste water contained 0.19 mg l–1 of manganese, mostly in a dissolved form. This manganese diffused out both horizontally and vertically into the surrounding sea water. The content of manganese in the liquid and solid phases in the sediments, however, are inverse with that in the sea water; namely the lowest concentration of manganese in the sediments was observed at the station near the outfall and manganese concentration increased with the distance from the outfall.  相似文献   

18.
The variability of the pathway of the Kuroshio is known to control that of the intensity of upwelling of the cold and nutrient-rich deep shelf water at the shelf-break point. This study has investigated the influences of the long-term variability of the hydrographical and biogeochemical conditions at the shelf-break point on those in the inner Seto Inland Sea. Results from observations conducted since 1972 by prefectural fisheries observatories showed a temporary decrease of temperature in the lower layer of the entrance of Kii Channel in summertime in the specific years when the Kuroshio pathway favored deep shelf water intrusion. A corresponding change in temperature was also found in the inner shelf sea, such as western Osaka Bay and Harima-Nada. The model developed in this study covers a 30-year period and well reproduces the temporal change in temperature. It also shows sufficient reproducibility in both seasonal behavior of hydrographical and biogeochemical properties and the inter-annual variability of hydrographical properties throughout the eastern Seto Inland Sea. It was found that the inter-annual variations of annual total flux through the section at the entrance to Kii Channel affect the inter-annual variation of the observed concentration of Dissolved Inorganic Nitrogen (DIN) in Harima Nada, but the effect was smaller than those of river input and other parameters.  相似文献   

19.
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   

20.
The effects of the coastal boundary geometries on the tidal currents and the tidal mixing are studied mainly on the basis of hydraulic model experiments. Mizushima-Nada Sea, which is located in the central part of Seto Inland Sea, and the whole Seto Inland Sea were chosen as the prototypes.Currents and eddies geometrically induced in the tidal currents and in the ocean currents have significant effects on the water exchange, from small scales to meso scales, in the bays and near-shore regions of the ocean.As to small scale phenomena near irregular coastal boundaries such as river mouths, headlands and harbors, tidal currents produce organized eddy currents of the width scale. They are important to the temporary flushing and the local redistribution of the river water or the waste water.As to phenomena of larger scales, the tidal currents produce rather steady residual circulations in each part of the Inland Sea, due to the non-linear effects of the oscillating component. They are controlled by the geometry of the sea as separated by a narrow strait. These horizontal circulations of about 20 km in scale become the main mechanism of the water exchange in the Inland Sea. The one-dimensional dispersion coefficient due to these circulations is proportional to the product of the diameter and the current velocity of the circulations. The proportional constant takes the value of 0.40.5.  相似文献   

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