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1.
Non-dimensional equations of motion are derived for the A.C.C. of the barotropic mode, including the bottom friction and the horizontal eddy viscosity. Integration of the vorticity equation along a streamline leads to the zeroth order stream function which is dependent only on depth divided by Coriolis parameter. Integration of the momentum equation along a streamline yields the relation between the momentum input by wind stress and its dissipation by the bottom friction and by the horizontal eddy viscosity. This relation determines the magnitude of the stream function. It explains differences in the total transport of the A.C.C. obtained byBryan andCox (1972), though it gives only one third of the total transport obtained byKamenkovich (1972) with his vertical eddy viscosity of 102cm2 s?1. With 1 cm2 s?1 of this viscosity,Bryan andCox obtained the transport of about 650 or less than 32×106m3s?1 for constant or variable depth models, respectively. The higher transport is mainly due to broadening of the width of the A.C.C., whereas the lower value is due to its narrowing and meandering which in turn make the horizontal eddy viscosity more effective (by exercising friction on both sides of the A.C.C.) and the wind stress input smaller than the almost zonal streamlines for constant depth. In the Appendix dynamics of the bottom boundary layer is treated to give rational estimates of the bottom stress in terms of the geostrophic flow and is compared to the recent observations of the benthic boundary current in the Straits of Florida and off San Diego.  相似文献   

2.
The result of two sequential oceanographic stations of 36 hours each in the area of sand ridges are presented. One station was located in the trough between two sand ridges and the other was at the crest of a sand ridge. At these stations salinity and temperature of the sea water, currents, winds, waves, and barometric pressure were measured each hour.During the observations, a cold front passed; this generated westerly winds that grew in speed from 24 to 52 km h?1. The average height of the wind generated waves grew from 1.0 to 1.5 m and their periods increased from 7 to 10 s, and the speed of the northeast directed surface current increased from 40 to 82 cm s?1. A bottom current (also directed northeast) increased from 26 to 34 cm s?1.After the cold front had passed, the wind backed to the southeast and decreased in speed from 26 to zero km h?1. The surface current in a northwest direction decreased from 29 to 8 cm s?1. A bottom current (also directed northwest) decreased from 22 to 3 cm s?1. Later, swells from the southeast appeared and their periods increased from 5 to 9 s and their heights grew from 1.0 to 1.5 m. After 3 hours, the speeds of the surface and bottom currents increased from 8 to 72 cm s?1 and 3 to 62 cm s?1 respectively.This cold front induced strong winds and storm-wave currents able to erode sediments (assuming a threshold velocity of 20 cm s?1) and transport them in a north-northeast direction.The origin and the maintenance of these sand ridges is thought to be a function of sediments eroded from troughs and piled up at ridge crests during a storm condition. Some eroded sediments are transported north of Verga lighthouse where they are deposited on a smooth bottom.  相似文献   

3.
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   

4.
The flux of ammonia, phosphate, silica and radon-222 from Potomac tidal river and estuary sediments is controlled by processes occurring at the sediment-water interface and within surficial sediment. Calculated diffusive fluxes range between 0·6 and 6·5 mmol m?2 day?1 for ammonia, 0·020 and 0·30 mmol m?2 day?1 for phosphate, and 1·3 and 3·8 mmol m?2 day?1 for silica. Measured in situ fluxes range between 1 and 21 mmol m?2 day?1 for ammonia, 0·1 and 2·0 mmol m?2 day?1 for phosphate, and 2 and 19 mmol m?2 day?1 for silica. The ratio of in situ fluxes to diffusive fluxes (flux enhancement) varied between 1·6 and 5·2 in the tidal river, between 2·0 and 20 in the transition zone, and from 1·3 to 5·1 in the lower estuary. The large flux enhancements from transition zone sediments are attributed to macrofaunal irrigation. Nutrient flux enhancements are correlated with radon flux enhancements, suggesting that fluxes may originate from a common region and that nutrients are regenerated within the upper 10–20 cm of the sediment column.The low fluxes of phosphate from tidal viver sediments reflect the control benthic sediment exerts on phosphorus through sorption by sedimentary iron oxyhydroxides. In the tidal river, benthic fluxes of ammonia and phosphate equal one-half and one-third of the nutrient input of the Blue Plains sewage treatment plant. In the tidal Potomac River, benthic sediment regeneration supplies a significant fraction of the nutrients utilized by primary producers in the water column during the summer months.  相似文献   

5.
To accurately characterize sound speed dispersion of shallow sediments in the Southern Yellow Sea, three types of sediments, i.e., silt, clayey silt, and silty clay, were selected to measure the sound speeds at 25–250?kHz. Over the frequency range, the sound speeds vary approximately from 1,536 to 1,565?m?s?1 in silt sediment, from 1,511 to 1,527?m?s?1 in clayey silt sediment, and from 1,456 to 1,466?m?s?1 in silty clay sediment. The sound speed exhibits a slow increase with frequency in a nearly linear gradient, but these three types of sediments have different sound speed dispersion characteristics. The silt sediment with relatively coarse grains has the most significant sound speed dispersion, while the sound speed dispersions of the two others are relatively weak. Comparison between the measured dispersions and the model predictions shows that the grain-shearing model can match the measured data at most of frequencies. Nevertheless, when the grain bulk modulus was assigned 3.2?×?1010?Pa according to relevant references, the Biot–Stoll model predictions were higher than the measured values at high frequencies; when it was assigned a relatively small value of 2.8?×?1010?Pa, the model predictions achieved optimal matching with the measured values.  相似文献   

6.
Application of a simple model describing regional variations in the contents of manganese and associated minor metals in deep-sea sediments suggests that solid manganese phases are being removed from the <0.5 μm fraction of seawater at ～1–7 · 1012g yr?1 in excess of the rate of stream-supplied manganese. This flux is consistent with: (1) the relative rates of sediment accumulation in the Atlantic and Pacific Oceans; (2) the contrast between the oceanic residence time of manganese calculated from stream-supply data (14 · 103 yr) and from the flux of manganese precipitating in marine sediments or as manganese nodules (0.38–2.4 · 103 yr); (3) the surplus mass of manganese revealed by geochemical balance calculations (22.9 · 102g). On this basis excess manganese is accumulating in deep-sea sediments at 0.2–2.0 · 10?6 g cm?2yr?1. Manganese supplied to the upper layers of marine sediments by diagenesis has been evaluated with the aid of vertical advection—diffusion—reaction models. The calculated diagenetic flux of manganese at the sediment surface in a near-shore environment is in agreement with the known accretion rate of manganese deposits (1.7 · 10?2 g cm?2 10?3 yr?1) and the regionally variable flux over the area assessed is consistent with the presence or absence of manganese nodules at or near the water-sediment interface. The diagenetic flux at the surface of deep-sea sediments has been calculated at 0.7 · 10?4 g cm?2 10?3 yr?1 when the upper, oxic, zone of the sediment is ～20 cm thick. A limiting factor on the in situ production flux of dissolved manganese in deep-sea sediments appears to be the availability of reducing agents for manganese dissolution rather than the rate of downward transport of manganese-rich sediment to a reaction boundary where dissolution takes place. Various estimates of the rate of upward-migrating manganese suggest that manganese precipitates in the oxic zone with a rate constant of ～10?7 sec?1 with the result that diagenetic processes cannot supply the flux of excess manganese through more than ～0.25 m of oxic sediment. However, estimates of the flux of manganese to the oceans by submarine volcanic processes (0.79–1.1 · 1012g yr?1) are similar to the surplus mass of manganese detected by geochemical balance calculations (0.7 · 1012g yr?1). If submarine hydrothermal solutions provide only 10% of this excess then their computed discharge rate (39 g cm?2 yr?1) and residence time in the upper layer of oceanic crust (130,000 yr) agree well with these parameters for continental thermal springs.  相似文献   

7.
《Oceanologica Acta》1998,21(4):533-542
Seawater samples collected in the northeast Pacific from 112° 50′W to 126° 36′W along a latitudinal band (21–25° N) have been analysed for 228RA and 226Ra. Both nuclides exhibit their characteristic distributions. In the surface water, the exponential-like decrease of 228 Ra away from Baja California can be interpreted by horizontal water mixing with eddy diffusion coefficients (Kx) of 1 × 106 cm2 s−1 and 5 × 107 cm2 S−1 for scale lengths of 200 km and 1000 km, respectively. In the bottom waters, the decrease of 228Ra away from bottom sediments can be modeled by vertical eddy diffusivities (Kz) of 15–30 cm2 s−1 except at one station (24° 16.9′ N, 115° 8.9′ W) where a value of 120 cm2 s−1 is obtained. The 228Ra-derived diffusivities were used to compute the mass balance of 226Ra using a two-box model. The model results show a mean mixing coefficient of 3.8 cm2 s−1 for the thermocline and a mean upwelling velocity of 7.7 m y−1 in the study area, both are about two or three times higher than those generally quoted for the Pacific.  相似文献   

8.
This study quantifies diapycnal mixing and vertical heat transfer in the Pacific side of the Arctic Ocean, where sea-ice cover has disappeared between July and September in the last few decades. We conducted microstructure measurements in the open water region around the Canada Basin from late summer to fall in 2009 and 2010 using R/V Mirai. In the study domain, the dissipation rate of turbulent kinetic energy, ε, is typically as low level as O(10?10) W kg?1, resulting in vertical heat diffusivity of O(10?7) m2 s?1, which is close to the molecular diffusivity of heat, suggesting comparatively little predominance of mechanical turbulent mixing. An exception is the case at the Barrow Canyon, where the strong baroclinic throughflow generates substantial vertical mixing, producing ε > O(10?7) W kg?1, because of the shear flow instability. Meanwhile, in the confluence region, where the warm/salty Pacific water and the cold/fresh Arctic basin water encounter, the micro-temperature profiles revealed a localized enhancement in vertical diffusivity of heat, reaching O(10?5) m2 s?1 or greater. In this region, an intrusion of warm Pacific water creates a horizontally interleaved structure, where the double-diffusive mixing facilitates vertical heat transfer between the intruding Pacific water and the surrounding basin waters.  相似文献   

9.
Turbulent mixing in the central equatorial Pacific has been quantitatively evaluated by analyzing data from microstructure measurements and conductivity temperature depth profiler (CTD) observations in a meridionally and vertically large region. The result that strong turbulent mixing with dissipation rate ε (>O(10?7) W kg?1), continuing from sea-surface mixed layer to low Richardson number region below, in the area within 1° of the equator, shows that turbulent mixing has a close relationship to shear instability. ε > O(10?7) W kg?1 and turbulent diffusivity K ρ  > O(10?3) m2 s?1 were obtained from near-surface to 85 db at stations even southwardly beyond 3°S, where it is already far from the southern boundary (~2°S) of the Equatorial Undercurrent. Turbulence-induced heat flux and salinity flux were calculated, and both had their maxima in the equatorial upwelling region, though the former was downward and the latter was upward. Accordingly, vertical velocity in the upwelling region was estimated to be similar to the results derived by other methods. These fluxes and the vertical velocity suggest the critical importance of turbulent mixing in maintaining the well-mixed upper layer. Secondly, in the intermediate region (>500 db), turbulent eddies were investigated by applying Thorpe’s method to the CTD data. A large number of overturns were detected, with spatial-averaged K ρ (700–1,000 db) being 3.3 × 10?6 m2 s?1, and the corresponding K ρ-max reaching to O(10?4) m2 s?1 in the north (3°–13°N). The results suggest that, in the intermediate region, considerable turbulent mixing occurs and moderates the properties of the water masses.  相似文献   

10.
The spatial and temporal variability of tidal mixing in Bohai Sea is studied using a numerical approach. In calculating tidal mixing, accurate barotropic tidal current is obtained via a harmonic analysis package utilizing the simulated current output from a high-resolution regional ocean model. And a “small-scale” roughness map is adopted to describe the detailed topographic features of Bohai Sea. It is shown that the tidal mixing estimated in Bohai Sea is much higher than the level of global background, and fluctuates considerably at some regions within a single day. In Liaodong Bay, Bohai Bay and Bohai Strait, the mixing varies greatly, with the peak value of O (10?2) m2 s?1. The order of magnitude of mixing in Laizhou Bay is about O (10?5～10?3) m2 s?1. Mixing with background level of O (10?5) m2 s?1 only appears in central area. Result also shows that rough topography plays relatively a more important role than tidal current in enhancing diapycnal mixing in Bohai Sea. The distributions of tidal mixing in selected sections reveal that the vertical stratification in Bohai Sea is not obvious, generally renders a barotropic structure.  相似文献   

11.
Vessel-based observations of water column structure and flow near a shallow-crested seamount are used to quantify the physical disturbance induced by that seamount. The implications of this disturbance on the ‘feeding hole’ hypothesis are then examined based on data from moored thermistors and acoustic current profilers, as well as vessel-based acoustic sounding-derived biomass estimates, currents, and conductivity-temperature-depth profiles from a 55 km square grid of stations around the crest. Mean currents in the region of 0.2 m s?1 are comparable to observations from surface drifters whereas the semidiurnal tidal flow amplitude was one third of this. Thorpe Scale-based estimates of energy dissipation rate were in the range 10?9 to 2.10?8 W kg?1 and vertical diffusivities Kz were in the range 10?4 to 10?3 m2 s?1. Turbulence levels were higher upstream of the seamount–likely due to the influence of nearby seamounts Rumble IV and V. There was no evidence of a Taylor Cap in the Rumble III velocity field. The sounder data provide some evidence of a feeding hole and analysis based on diffusivities suggests that this might persist downstream of the seamount for as much as 7 days.  相似文献   

12.
This survey of the southernmost significant upwelling site in the Benguela Current showed that the oceanography is dominated by the seasonal wind cycle of predominant S-E winds in summer and N-W winds in winter. In the upwelling season, extending from September to March, a semi-permanent plume is isolated by a pronounced oceanic front whose position varies in the short-term and is related to wind direction. Surface waters change immediately and deeper waters more slowly to fluctuations in wind. The rate of upwelling was statistically related to wind data. A maximum rate of 32 m day?1 was found.In spring low temperature and salinity water flows northward on the shelf while between late summer and later winter oxygen-depleted water, rich in nutrients, flowed south at an estimated rate of 7–21 × 104 m3 s?1 in a counter current to the Good Hope Jet.Local depletion of oxygen occurs due to phytoplankton decomposition caused, in autumn, by falling light levels and, in summer in calm periods, by nitrate depletion (<1 μg-at N 1?1). Primary productions is estimated at 3.7 kg C m?2 yr?1 with a maximum growth rate (PImax) = 17.4–19.0 mg C mg chlorophyll a?1 hr?1 and half-saturation constant (KS) = 0.4–1.1 μg-at N 1?1. Nutrients were utilized and oxygen produced: ΔP:ΔN:ΔSi:ΔO=1:19.1 to 23.3:17.5 to 23.3:?227 to ?293. High N:Si ratios (maximum 4.28) were found in oxygen-depleted water produced locally while that coming from the north had low ratis, due to resolution of silica from the sediments and nitrate reduction. The mean zooplankton standing stock, 2.3 g dry weight m?2, was 12% of the phytoplankton crop. In summer stocks were maximal 40–100 km and minimal 20–50 km from the coast while in winter they were maximal inshore. Little vertical migration occurred and the waters above the thermocline contained the majority of the population.  相似文献   

13.
Chemical extraction techniques show that the majority of the arsenic in North Atlantic deep-sea sediments is associated with an iron phase compositionally similar to that found in deep-sea ferromanganese nodules (As/Fe ～ 11 · 10?4) and is probably of seawater origin. Some sediments also contain As associated with Fe oxides produced by continental weathering. A minority (～8%) of the arsenic is of detrital origin but is not associated with Fe or Mn oxides; it has a content (1.7 ppm) similar to the average crustal abundance. In the Eastern Mediterranean Sea, near-shore sediments contain As associated with land-derived Fe oxides (As/Fe ～ 2 · 10?4), but As/Fe ratios increase to ～ 13 · 10?4 in deep-sea sediments as the contribution of seawater derived arsenic becomes dominant. Arsenic is enriched in metalliferous sediments (As/Fe ～ 20?50 · 10?4) but As/P ratios of metalliferous sediments, deep-sea ferromanganese nodules and deep-ocean water are all similar. Although a hydrothermal contribution cannot be discounted, it is likely that the arsenic is also of seawater origin, suggesting that hydrothermal iron oxyhydroxides remove As more efficiently from seawater than do iron phases (goethite) in deep-sea sediments and nodules. Arsenic accumulates in deep-sea sediments (～ 6 μg cm?2 10?3 yr?1) at sediments (～ 120 μg cm?2 10?3 yr?1) at rate sufficient to balance river input input (～3 · 1010 g yr?1). These estimates give an oceanic residence time for arsenic of 1–2 · 105 yr.  相似文献   

14.
The partitioning of annual organic carbon fluxes from five stations located in the vicinity of the Pacific-Antarctic Ridge and the Peru continental margin suggests that 35–85% of the total near-bottom organic carbon flux is utilized at or near the sediment-water interface. These estimates have large uncertainties, but illustrate that assessments of organic carbon utilization can be made by several stepwise approaches which are generally applicable to a wide spectrum of marine environments.In one approach, the mineralization of organic carbon from the sediments was predicted from both sedimentary organic carbon and pore water nutrient profiles with comparable results. Neglecting sediment mixing, the rate constants of the anoxic sediments off Peru range from 0.1 × 10?3 to 4 × 10?3 y?1, and rate constants derived for oxic SW Pacific sediments range from 3 × 10?4 to 7 × 10?4 y?1. As with other values reported for sulfate reducing sediments by Toth and Lerman (1977) and for oxic central Pacific sediments by Müller and Mangini (1980), log-log plots of rate constants vs. sedimentation rate define two parallel linear relationships for oxic and anoxic sediments, respectively. The apparently enhanced rates for oxic environments may result from large benthic organisms which redistribute a portion of the available detritus and in doing so convert it into more easily accessible and metabolizable organic matter. In low-oxygen environments, bottom feeders and infauna are less abundant and more likely to irrigate rapidly accumulating sediments.  相似文献   

15.
Volatile fatty acid (VFA) apparent turnover rates in organic-rich marine sediments were determined by measuring whole sediment VFA concentration and the corresponding first-order reaction rate constants. In order to measure VFA concentrations, bulk wet sediment samples were basified, freeze-dried, extracted with methanol, derivatized to form methyl esters of the VFAs, and analyzed by packed-column gas chromatography using hexanoic acid as an internal standard. The detection limits for acetate, propionate, iso-butyrate and butyrate were 1.0, 0.4, 0.2 and 0.2 μmol l?1s, respectively, for 600 ml samples. Rate constants for acetate and propionate were determined by anaerobically incubating samples at in-situ temperatures with tracer levels of 14C-labelled VFAs. Metabolized label was recovered as CO2, CH4, cellular material, water-soluble material, and VFA (ether-soluble) fractions. Apparent turnover rates measured during summer and winter in anoxic Cape Lookout Bight, North Carolina (U.S.A.) sediments were in the range of 19–330 μmol l?1s h?1 for acetate and 0.7–7.0 μmol l?1s h?1 for propionate.  相似文献   

16.
Investigations including a bathymetric survey, sonic prospecting, and vibrocoring were performed to understand the horizontal and vertical distribution of 137Cs in seabed sediments in shallow seas with depths less than 30 m near the Fukushima Daiichi Nuclear Power Plant. Especially, features of 137Cs distributions in deeper sections of the seabed sediments were studied to evaluate the vertical heterogeneity of 137Cs distribution in the seabed sediments in shallow seas. The distribution area of the seabed sediments was less than half of the investigation area, and the locations of the seabed sediments were divided into flat and terrace-like seafloors based on their topographical features. The thicknesses of the seabed sediment layers were mostly <2 m. The 137Cs inventories in the seabed sediments varied from 13 ± 1 to 3,510 ± 26 kBq m?2, and continuous distributions of 137Cs at depths greater than 81 cm were observed. The 137Cs distributions were not uniform; however, the 137Cs inventories tended to be larger near the base of the steeper ascending slopes than in the terrace-like seafloors themselves. Based on the relationship between the 137Cs inventories and mean shear stress, features of the seafloor topography were inferred to be significant control factors governing the horizontal and vertical distribution of 137Cs in the seabed sediments. Rapid changes and multiple peaks in the vertical profile of the 137Cs distributions suggest that they are related to pulse input caused by heavy-rain events. Change in the 137Cs inventories with depth in this study are larger than those reported in previous studies, indicating earlier results of 137Cs inventories per unit in seabed sediments in shallow seas, especially near the river mouth, which drains a radiologically highly-contaminated basin, were underestimated.  相似文献   

17.
-In this paper, an improvement and revision of the theory of Miiller (1974, 1976), has been made under two conditions: (1) the horizontal component of the Coriolis force has been taken into account in the equations of motion for the internal wave field; and (2) the role of internal waves with frequencies close to the inertial frequency has been considered. The values of the viscosity coefficients and the diffusivity coefficients obtained in this paper are: Theappearance of the cross-diffusion (vc) of momentum is a natural result from the effect of the horizontal Coriolis force. Therefore the role of the horizontal shear of the mean flow cannot be absolutely separated from that of the vertical shear. So far in testing Muller's theory, the approximation of effective wave stress obtained by Ruddick and Joyce (1979) was extensively used, but it has to be revised under the conditions of this paper. The revised approximation shows that the internal waves with low frequencies close to the inertial frequency pl  相似文献   

18.
The aim of this study was to evaluate the erodibility of submarine coastal sediments for the purpose of modelling sediment dynamics in Mecklenburg Bay, south-western Baltic Sea. Erosion thresholds derived from experiments with a device microcosm on cores of fine sand (n=5, mean grain size=132 µm) and mud (n=5, medium silt size, mean=21 µm), collected at different times of the year, were compared to theoretical critical shear stress velocities based on grain-size measurements. For this purpose, a sedimentological map of natural surface sediments was constructed for the study area. Calculated values for critical shear stress velocities (u* cr-Hjulström ) are 1.2 cm s?1 for fine sand, and 3.75 cm s?1 for cohesive mud. At the mud station, erosion experiments showed an initial transport of the fluffy surface layer (u* cr-initial ) at a mean critical shear stress velocity of 0.39 cm s?1. Initial rolling transport at the fine sand station for single sand grains was recorded at values of 0.5 cm s?1. At higher shear stress velocities, the two sediment types showed diverging erosion behaviour. Measurable erosion (ε>5.0×10?6 kg m?2 s?1) of fine sand starts at a mean critical shear stress velocity (u* cr-erosion ) of 1.15 cm s?1 whereas fluffy surface material on mud cores was eroded at mean u* cr-erosion of 0.62 cm s?1. This indicates that measured erosion thresholds at the fine sand site fit well to calculated critical shear stress velocities whereas calculated erosion thresholds for cohesive mud are roughly 6 times higher than measured values. As erosion behaviour at the mud station was dominated by fluffy surface material, the comparability of measured and calculated threshold values may be reduced. The underlying silt-sized sediment itself was stable due to cohesive effects. This behaviour has to be taken into consideration by using sediment types instead of mean grain sizes for mapping and modelling sediment dynamics. A comparison of the near-bottom hydrodynamic conditions in the study area and experimentally derived critical shear stress velocities suggests that particle transport is controlled by storm events whereas under calm conditions shear stress velocities do not exceed the critical values.  相似文献   

19.
The vertical structure of the Soya Warm Current (SWC) was observed by a bottom-mounted acoustic Doppler current profiler (ADCP) in the region of the SWC axis near the Soya Strait during a 1-year period from May 2004. The ADCP data revealed a marked seasonal variability in the vertical structure, with positive (negative) vertical shear in summer and fall (winter and spring). The volume transport of the SWC is estimated on the basis of both the vertical structure observed by the ADCP and horizontal structure observed by the ocean radars near the strait. The transport estimates have a minimum in winter and a maximum in fall, with the yearly-averaged values in the range of 0.94–1.04 Sv (1 Sv = 106 m3 s−1). These lie within a reasonable range in comparison to those through other straits in the Japan Sea.  相似文献   

20.
The strength of mixing due to turbulence in the Antarctic Slope Front (ASF) region was investigated using CTD (conductivity-temperature-depth profilers) observations and direct measurements of turbulence conducted off Adélie Land, East Antarctica along 140°E from the 12th–14th February, 2005. The strongest horizontal gradient of the ASF was located below 300 m depth near the 1000 m isobath. The turbulent measurements revealed that the energy dissipation rate frequently exceeded 10?8 Wkg?1 on the continental shelf and upper slope regions. Turbulent diffusivities near the shelf break were higher than 10?3 m2s?1. Near the ASF the average turbulent heat flux was 5.7 Wm?2 and 1.1 Wm?2 across the temperature minimum layer to 250 m and from 300 to 600 m, respectively. The distribution of the high dissipation rate was consistently explained by the characteristic curve of the M2 internal wave emanating from the shelf break and continental slope. The water mass observed in the ASF below 300 m in the continental slope comprised Modified Circumpolar Deep Water and low salinity Shelf Water originating from either the upper layer of the Adélie Depression or the Adélie Bank, and produced by boundary mixing near the shelf break.  相似文献   

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