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1.
On the basis of the climatic data array on temperature and salinity including the data of observations carried out at 102,000 oceanographic stations in 1910–1998, we estimate the amount of available potential energy of large-scale processes in the 0–300-m layer of the Black Sea and study its annual variability. The annual average amount of available potential energy in the active 0–300-m layer is equal to 13.5×1014 J, its maximum amount attained in March is 25×1014 J, and its minimum amount attained in August is 8×1014 J. In the autumn–winter period, the density of available potential energy in the 0–50-m layer increases and its maximum is attained in December–January (30 J/m3). Beginning with January, the density of available potential energy increases in the layer of the main pycnocline (50–150 m). Its maximum is attained in March (50 J/m3) and then this quantity decreases till August (down to 14 J/m3). In August, we study the interdecadal variability of the available potential energy in the 50–300-m layer by using the data accumulated for decadal periods with five-year shifts in 1956–1995. The maximum variability is observed at a depth of 100 m. The maximum average (over the sea) amounts of available potential energy were observed in 1961–1970 and 1986–1995. The minimum amounts were recorded in 1976–1985.  相似文献   

2.
We present the results of six dye tracer experiments that measured the mixing and circulation at the shelfbreak front on the New England Shelf. The last three were conducted during the New England Shelfbreak Productivity Experiment (NESPEX) with concurrent isopycnal float deployments. The results are consistent with the Chapman and Lentz [Chapman, D.C., and Lentz, S.J. (1994). Trapping of a coastal density front by the bottom boundary layer. Journal of Physical Oceanography, 24, 1465–1479.] model prediction of the separation and upwelling along the shelfbreak front of bottom boundary layer (BBL) water forced by an Ekman buoyancy flux, but show considerable variability. Cross-shelf velocities at the detachment point are 2–3 × 10−2 m/s. But seaward, over the slope region, dye tagged water was sheared from the main patch into small filaments that upwelled along the front with cross-shelf speeds up to 0.1 m/s. Cross-shelf diffusion was of order 10 m2/s in the mixed bottom layer and 1 m2/s in the interior along the front. Within the stratified front, the mean vertical diffusivity was Kz  4 × 10−6 m2/s. The dispersion of shelfwater in the slope region is effected by turbulent flow with advective speeds exceeding the small scale diffusive mixing. The mean flux of the detached BBL water is sufficient to account for the net loss of shelf water during its transit from Cape Cod to Cape Hatteras.  相似文献   

3.
A five-element mooring array is used to study surface boundary-layer transport over the Northern California shelf from May to August 2001. In this region, upwelling favorable winds increase in strength offshore, leading to a strong positive wind stress curl. We examine the cross-shelf variation in surface Ekman transport calculated from the wind stress and the actual surface boundary-layer transport estimated from oceanic observations. The two quantities are highly correlated with a regression slope near one. Both the Ekman transport and surface boundary layer transport imply curl-driven upwelling rates of about 3×10−4 m s−1 between the 40 and 90 m isobaths (1.5 and 11.0 km from the coast, respectively) and curl-driven upwelling rates about 1.5×10−4m s−1 between the 90 and 130 m isobaths (11.0 and 28.4 km from the coast, respectively). Thus curl-driven upwelling extends to at least 25 km from the coast. In contrast, upwelling driven by the adjustment to the coastal boundary condition occurs primarily inshore of the 40-m isobath. The upwelling rates implied by the differentiating the 40-m transport observations with the coastal boundary condition are up to 8×10−4 m s−1. The estimated upwelling rates and the temperature–nitrate relationship imply curl-driven vertical nitrate flux divergences are about half of those driven by coastal boundary upwelling.  相似文献   

4.
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   

5.
Time-series measurements of temperature, salinity, suspended matter and beam attenuation coefficient () were measured at four hour intervals for about two days in June/ July 1982 in the middle shelf region and the coastal region of the southeastern Bering Sea. Current meters were also moored at the same locations.Depth-time distributions of indicated that profiles of suspended matter resulted from a combined process of resuspension of underlying sediments and sinking of suspended particles. Average-values for all measurements for particles revealed that the upward transport of particles due to resuspension formed a boundary layer, with a thickness apparently related to scalar speed. The average-profiles of the particle volume concentration were assumed to result from a balance between the sinking and diffusive flux of particles under a steady state, and the upward fluxes were calculated. Within the boundary layer, values of the upward fluxes of particulate organic matter linearly decreased with the logarithm of distance from the bottom. Fluxes of organic carbon at the upper edge of the boundary layer were 0.375 gC·m–2·day–1 in the middle shelf region (18 m above the bottom, bottom depth=78m) and 0.484gC·m–2·day–1 in the coastal region (25 m above the bottom, bottom depth=33m), and fluxes of nitrogen in both regions were 0.067 gN·m–2·day–1. The flux of organic carbon obtained in the middle shelf region (18 m above the bottom) agreed approximately with the flux (0.416 gC·m–2·day–1) calculated by substituting primary production data into the empirical equation of Suess (1980).  相似文献   

6.
In Iwanai Bay, which is located on the Japan Sea coast in Hokkaido, seasonal fluctuations in cell densities of phycoerythrin-dominant cyanobacteria and chlorophyll-dominant, other picophytoplankton were examined. Cell densities of cyanobacteria and other picophytoplankton ranged from 1.4×105 to 1.9×108 and from 4.0×104 to 4.3×106 cells 1–1, respectively. The cell densities of both groups tended to increase after spring diatom bloom with remarkable fluctuations from June to August. This tendency was caused by the vertical distributions of both groups. The maximum density layer shifted from 0–20 m depth in April–June to 20–50 m depth in August–October. Cyanobacteria were dominant in picophytoplankton community which accounted for 73–99% of the total cell density during the whole year. Present results show that the picophytoplankton community in Iwanai Bay was influenced by a single water mass system (Tsushima Warm Current) during the whole year.This is contribution No. 254 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University.  相似文献   

7.
Suspended particulate matter (SPM) concentration and properties (particle size and settling velocity), water column and boundary layer dynamics were measured during a 60-d period at a site in 110 m water depth in the northern North Sea. The site was in stratified waters and measurements were made during September–November as the seasonal thermocline was progressively weakening. SPM concentration was low, c. 1 mg dm−3 in the surface mixed layer and maximum values of 2 mg dm−3 in the bottom mixed layer. The bottom layer was characterised by larger mean particle size. SPM signals in the two layers were decoupled at the start of the period, when the thermocline was strong, but were increasingly coupled as the thermocline progressively weakened. A spring-neap cycle of resuspension and deposition of SPM was observed in the bottom mixed layer. Bed shear stresses were too small to entrain the bottom sediment (a fine sand) but were competent to resuspend benthic fluff: threshold bed shear stress and threshold current velocity at 10 mab were 0.02–0.03 Pa. and 0.18 m s−1, respectively. Maximum SPM concentration in the bottom layer preceded peak spring tide currents by 3 d. Simulation of fluff resupension by the PROWQM model confirms that this was due to a finite supply of benthic fluff: the fluff layer was stripped from the seabed so that fluff supply was zero by the time of peak spring flow. SPM was redeposited over neap tides. Fluff resuspension must have been enhanced by intermittent inertial currents in the bottom layer but unequivocal evidence for this was not seen. There was some resuspension due to wave activity. Settling velocity spectra were unimodal or bimodal with modal values of 2×10−4–2×10−3 mm s−1 (long-term suspension component) and 0.2–5.7 mm s−1 (resuspension component). The slowest settling particles remained in suspension at peak spring tides after the fluff layer had been exhausted. There was evidence of particle disaggregation during springs and aggregation during neaps.  相似文献   

8.
Mixed populations of free-living marine bacteria were collected at depths from the surface to the bottom (1,960m in Suruga Bay and 1,585 m in the Japan Sea) in the northwest Pacific during deep-sea diving by the submersible,Shinkai 2000. Their abundance in total cell counts and in lipopolysaccharide (LPS) concentration was found to decrease with increasing depth, and the decreasing profiles were shown to be linear on logarithmic scales. The total cell counts and the LPS concentration showed a linear relationship on arithmetic scales, and the LPS content per cell was found to be 1.02×10–14 g.  相似文献   

9.
Seasonal and vertical changes in abundances of bacteria and heterotrophic nanoflagellates (HNF), and HNF grazing on bacteria were investigated in a small eutrophic inlet of Uranouchi-Wan throughout the years. Bacterial densities in the surface water ranged from 1.2 to 11 (average 4.3)×106 cells ml–1 with a couple of maxima following the algal blooming. Densities of HNF ranged from 0.54 to 73 (average 16.4)×103 cells ml–1 in the surface, and showed almost similar fluctuation pattern to that of bacteria with a time lag of about 1 to 2 weeks. Grazing rates of HNF on bacteria obtained by FLB method were 4.78 to 16.9 (average 10.3±SD 4.8) cells HNF–1h–1 in the surface layer in summer, and consequent total bacterial consumption rates by HNF fluctuated from 4 to 99×104 cells ml–1h–1. In deeper layers, however, as HNF densities and grazing rates on bacteria were low, the grazing pressure of HNF on bacteria was small. Turnover times of bacteria by HNF grazing in the surface layer were calculated as relatively constant values of 40 to 60 h, however, it decreased to as low as 6 to 7 h when the HNF activity was highest. These results indicate that bacteria grew so actively by consuming organic matter in seawater as to compensate high HNF grazing pressure, and that bacteria and HNF in the microbial loop play important roles on the turnover of substrates in coastal ecosystems.  相似文献   

10.
A new deep-sea laser Raman spectrometer (DORISS—Deep Ocean Raman In Situ Spectrometer) is used to observe the preferential dissolution of CO2 into seawater from a 50%–50% CO2–N2 gas mixture in a set of experiments that test a proposed method of CO2 sequestration in the deep ocean. In a first set of experiments performed at 300 m depth, an open-bottomed 1000 cm3 cube was used to contain the gas mixture; and in a second set of experiments a 2.5 cm3 funnel was used to hold a bubble of the gas mixture in front of the sampling optic. By observing the changing ratios of the CO2 and N2 Raman bands we were able to determine the gas flux and the mass transfer coefficient at 300 m depth and compare them to theoretical calculations for air–sea gas exchange. Although each experiment had a different configuration, comparable results were obtained. As expected, the ratio of CO2 to N2 drops off at an exponential rate as CO2 is preferentially dissolved in seawater. In fitting the data with theoretical gas flux calculations, the boundary layer thickness was determined to be  42 μm for the gas cube, and  165 μm for the gas funnel reflecting different boundary layer turbulence. The mass transfer coefficients for CO2 are kL = 2.82 × 10− 5 m/s for the gas cube experiment, and kL = 7.98 × 10− 6 m/s for the gas funnel experiment.  相似文献   

11.
Observations of the western Arabian Sea over the last decade have revealed a rich filamentary eddy structure, with large horizontal SST gradients in the ocean, developing in response to the southwest monsoon winds. This summertime oceanic condition triggers an intense mesoscale coupled interaction, whose overall influence on the longer-term properties of this ocean remains uncertain. In this study, a high-resolution regional coupled model is employed to explore this feedback effect on the long-term dynamical and thermodynamical structure of the ocean.The observed relationship between the near-surface winds and mesoscale SSTs generate Ekman pumping velocities at the scale of the cold filaments, whose magnitude is the order of 1 m/day in both the model and observations. This additional Ekman-driven velocity, induced by the wind-eddy interaction, accounts for approximately 10–20% of oceanic vertical velocity of the cold filaments. This implies that Ekman pumping arising from the mesoscale coupled feedback makes a non-trivial contribution to the vertical structure of the upper ocean and the evolution of mesoscale eddies, with obvious implications for marine ecosystem and biogeochemical variability.Furthermore, SST features associated with cold filaments substantially reduce the latent heat loss. The long-term latent heat flux change due to eddies in the model is approximately 10–15 W/m2 over the cold filaments, which is consistent with previous estimates based on short-term in situ measurements. Given the shallow mixed layer, this additional surface heat flux warms the cold filament at the rate of 0.3–0.4 °C/month over a season with strong eddy activity, and 0.1–0.2 °C/month over the 12-year mean, rendering overall low-frequency modulation of SST feasible. This long-term mixed layer heating by the surface flux is approximately ±10% of the lateral heat flux by the eddies, yet it can be comparable to the vertical heat flux. Potential dynamic and thermodynamic impacts of this observed air–sea interaction on the monsoons and regional climate are yet to be quantified given the strong correlation between the Somalia upwelling SST and the Indian summer monsoons.  相似文献   

12.
Lagrangian experiments with short-term, drifting sediment traps were conducted during a cruise on RRS Charles Darwin to the NW coast of Spain to study the vertical flux and composition of settling biogenic matter. The cruise was split into two legs corresponding to (i) a period of increased production following an upwelling event on the continental shelf (3–10 August 1998) and (ii) an evolution of a cold water filament originating from the upwelled water off the shelf (14–19 August). The export of particulate organic carbon (POC) from the upper layer (0–60m) on the shelf was 90–240mgC.m−2.d−1 and off the shelf was 60–180mgC.m−2.d−1. Off shelf the POC flux at 200m was 50–60mg.m−2.d−1. A modest sedimentation of diatoms (15–30mgC.m−2.d−1) after the upwelling was associated with increased vertical flux of chlorophyll a (1.8–2.1mg.m−2.d−1) and a decrease of the POC:PON molar ratio of the settled material from 9 to 6.4. Most of the pico-, nano-, and microplankton in the settled material were flagellates; diatoms were significant during the on shelf and dinoflagellates during the off shelf leg. Off shelf, the exponential attenuation of POC flux indicated a strong retention capacity of the plankton community between 40 and 75m. POC:PON ratio of the settled particulate matter decreased with depth and the relative portion of flagellates increased, suggesting a novel, flagellate and aggregate mediated particulate flux in these waters. Export of POC from the euphotic layer comprised 14–26% of the integrated primary production per day during the on shelf leg and 25–42% during the off shelf leg, which characterises the importance of sedimentation in the organic carbon budget of these waters.  相似文献   

13.
The vertical flux of particulate matter at 330 m depth in San Lázaro Basin off southern Baja California ranged from 63 to 587 mg m−2 d−1 between August and November 1996. Organic carbon contents were between 5.6 and 14.8%, yielding flux rates of 9–40 mgC m−2 d−1. In December 1997 and January 1998, at the height of the strong El Niño event, the respective fluxes (47–202 mg m−2 d−1 and 3–8 mgC m−2 d−1) were comparable. The February–June 1998 records, however, revealed sharply reduced mass (1–6 mg m−2 d−1) and organic carbon (0.2–0.8 mgC m−2 d−1) fluxes. The organics collected in 1996 were predominantly autochthonous (δ13C=−22‰; C/N=8). The variations in δ15N (8.3–11.0‰) suggest an alternation of new and regenerated production, possibly associated with fluctuations in the intensity of deep mixing during that autumn. The relatively high organic matter fluxes in December 1997 appear to be associated with regenerated production. The average composition from February to June 1998 (δ13C=−23.6‰; 15N=11.7‰; C/N=10.5) indicates degraded material of marine origin. The maximum δ15N value found (14‰) suggests that deeper, denitrified waters were brought to the surface and possibly advected laterally. Regime changes in the waters of the basin occur at 6–10 week intervals, evidenced by concurrent shifts in most of the measured parameters, including fecal pellet types and metal chemistry. The marine snow-dominated detritus collected showed a shift from a mixed diatom-rich-radiolarian-coccolith assemblage in late 1996 to a coccolith-dominated assemblage, including the contents of fecal pellets, during the 1997–1998 El-Niño period. T–S profiles, plankton analysis and chlorophyll contents of the upper water column indicated that the strong phytoplankton bloom, normally associated with seasonal upwelling along the Pacific coast of Baja, did not occur during the spring of 1998. The persistence of oligotrophic conditions during the 1997–1998 El Niño event favored the dominance of nanoplankton and reduced the vertical flux of particles.  相似文献   

14.
In this paper methods are given of the IR radiometric determination of the temperature of the radiating oceanic layer,T s, and the determination on its basis of the temperature drop in the skin layer,dt, from on board a ship underway, which allows for the emissivity of the sea surface and the contribution of the atmosphere to the upward radiation of the sea surface. The seawater temperatureT w was registered by a contact sensor towed along the ship at a depth of 0.1–0.4 m. The valuedt=T s–T w was found to be within the limits of 0.07 to –0.85 K, being on average 0.33 K. The near-surface wind speedv (v=1–13 m s–1) had the best relationship withdt;dt=–0.66+0.06v. The empirical values ofdt were compared with the model ones obtained by the well-known formulae for the conditions of forced and free convection of the surface layer.Translated by Mikhail M. Trufanov.  相似文献   

15.
Aquatic surface microlayer contamination in chesapeake bay   总被引：1，自引：0，他引：1  
The aquatic surface microlayer (SMIC), 50 μm thick, serves as a concentration point for metal and organic contaminants that have low water solubility or are associated with floatable particles. Also, the eggs and larvae of many fish and shellfish species float on, or come in contact with, the water surface throughout their early development. The objectives of this study were (1) to determine the present degree of aquatic surface microlayer pollution at selected sites in Chesapeake Bay, and (2) to provide a preliminary evaluation of sources contributing to any observed contamination.Twelve stations located in urban bays, major rivers, and the north central bay were sampled three times, each at 5-day intervals during May 1986. Samples of 1.4–4.1 each were collected from the upper 30–60-μm water surface (surface microlayer, SMIC) using a Teflon-coated rotating drum microlayer sampler. One sample of subsurface water was collected in the central bay.At all stations, concentrations of metals, alkanes, and aromatic hydrocarbons in the SMIC were high compared with one bulk-water sample and with typical concentrations in water of Chesapeake Bay and elsewhere. SMIC contamination varied greatly among the three sampling times, but high mean contaminant levels (total polycyclic aromatic hydrocarbons, 1.9–6.2 μg 1−1; Pb, 4.9–24 μg 1−1; Cu, 4–16 μg 1−1; and Zn, 34–59 μg 1−1) were found at the upper Potomac and northern bay sites. Three separate areas were identified on the basis of relative concentrations of different aromatic hydrocarbons in SMIC samples - the northern bay, the Potomac River, and the cleaner southern and eastern portions of the sampling area.Suspected sources of surface contamination include gasoline and diesel fuel combustion, coal combustion, and petroleum product releases. Concentrations of metals and hydrocarbons, at approximately half the stations sampled, are sufficient to pose a threat to the reproductive stages of some fish and shellfish. Sampling and analysis of the surface microlayer provides a sensitive tool for source identification and monitoring of potentially harmful aquatic pollution.  相似文献   

16.
A set of hydrographic surveys were carried out in the Ría of Vigo (NW Spain) at 2–4 d intervals during four 2–3 week periods in 1997, covering contrasting seasons. Residual exchange fluxes with the adjacent shelf were estimated with a 2-D, non-steady-state, salinity–temperature weighted box model. Exchange fluxes consist of a steady-state term (dependent on the variability of continental runoff) and a non-steady-state term (dependent on the time changes of density gradients in the embayment). More than 95% of the short-time-scale variability of the exchange fluxes in the middle and outer ría can be explained by the non-steady-state term that, in turns, is correlated (R2>75%) with the offshore Ekman transport. Conversely, 96% of the variability of exchange fluxes in the inner ría rely on the steady-state term. The outer and middle ría are under the direct influence of coastal upwelling, which enhances the positive residual circulation pattern by an order of magnitude: from 102to 103 m3s−1. On the contrary, downwelling provokes a reversal of the circulation in the outer ría. The position of the downwelling front along the embayment depends on the relative importance of Ekman transport (Qx, m3s−1km−1) and continental runoff (R, m3s−1). When Qx/ R>7±2 the reversal of the circulation affects the middle ría. Our results are representative for the ‘Rías Baixas’, four large coastal indentations in NW Spain. During the upwelling season (spring and summer), 60% of shelf surface waters off the ‘Rías Baixas’ consist of fresh Eastern North Atlantic Central Water (ENACW) upwelled in situ. The remaining 40% consists of upwelled ENACW that previously enters the rías and it is subsequently outwelled after thermohaline modification. During the downwelling season (autumn and winter), 40% of the warm and salty oceanic subtropic surface water, which piled on the shelf by the predominant southerly winds, enters the rías.  相似文献   

17.
In January–February 1987, an urgent cruise JENEX-87 was carried out in the central equatorial Pacific during the occurrence of the 1986–87 El Niño. This cruise, supported by the Japan Science and Technology Agency, supplied heat flux data through the sea surface, on the basis of direct measurements of short- and long-wave radiation fluxes.In the time average, the heat gain due to the radiation flux (153 W m–2) was almost compensated by the heat loss due to latent heat flux (130 W m–2), and thus the net heat gain was small in magnitude (20 W m–2). On the other hand, day-to-day changes of the net heat flux ranged within ±130 W m–2, mainly reflecting the downward short-wave radiation variations.The heat balance in the surface oceanic mixed layer was investigated in two quadrangle areas (160°E-180° and 180°-160°W between 2°N and 2°S), using the surface heat flux and estimating the advective heat fluxes due to the geostrophic and Ekman currents. In these two quadrangles, we respectively derived –187±88 W m–2 and +27±95 W m–2. The former value, which is equivalent to about 1°C month–1 drop of the mixed layer temperature, is evidence of the abnormal oceanic condition in the occurrence of the 1986–87 El Niño event.  相似文献   

18.
The vertical distributions of suspended particles in Osaka Bay were measured by using anin situ beam attenuation meter. The concentration of suspended particles near the bottom increases rapidly toward the bottom where size of sediment is in a range of silt. The settling velocity of suspended particles near the bottom was measured with the use of a settling tower in the laboratory. The settling velocity of the suspended particles with diameter from 10 to 100m is 2×10–3cm s–1 to 5×10–2cm s–1. The density of the particles ranges from 2.0 to 1.1 and decreases with increasing particle diameter.  相似文献   

19.
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   

20.
Data on the diffusion coefficientK zand the concentration of H2S in the Black Sea are used to compute the depth distribution of the vertical flux, and the intensity of the H2S sources and sinks. On average, the total production of H2S in the Black Sea reaches 37×106 t/year. The main bulk of H2S is produced not at the bottom, but in the layer of 450–1300 m. Destruction of H2S prevails above the 400 m layer. Dissolved oxygen penetrating the H2S zone can oxidize only half of the hydrogen sulphide produced in the sea.Translated by Mikhail M. Trufanov.  相似文献   

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