Nonlinearity of the horizontal velocity field under wind-waves

Using the data from a wind-tunnel experiment, bispectra of orbital-motions of wind-waves and of turbulence are calculated, and nonlinear interaction of wind-waves with turbulence in water are discussed. The wind-waves or the orbital motions of them, at first, produce the turbulence coherent with themselves, and then this coherent turbulence changes to the turbulence noncoherent with wind-waves. Nonlinearity of the velocity fluctuations in the surface layer in water under wind-waves is almost due to the nonlinear energy transfer from the orbital motions of wind-waves to the coherent turbulence. The vertical variations of the power spectra and of the normalized bispectra suggest that the wind driven currents near the surface play an important role in the process from orbital motion of wind-waves to noncoherent turbulence.     

Some characteristics of the development process of the wind-wave spectrum

The development process of wind-waves of which spectral peak distributes from 0.6 cps to 9.3 cps will be discussed on the basis of the wind tunnel experiments and of the field observations performed at Lake Biwa. The characteristics of power and slope spectra are here presented. The development process of these wind-waves is characterized by three stages;i.e. initial-wavelets, transition stage and sea-waves. In the wind tunnel experiments, the transition from the stage of the initial-wavelets to the transition stage occurs when the wave spectral peak arrives at the line 6.40×10^–4 k ^–2cm²·sec (wherek is wave number) or when the slope spectral density at the frequencyf _max becomes larger than 6.40×10^–4 sec. In the stage of sea-waves, the component wave of a wave-spectral peak is steepest in the component waves. And the wave spectral peak develops along the line 1.02×10² f ^–6 cm²·sec (wheref is the frequency corresponding to the wave numberk) untill it reaches the line 33.3f ^–4cm²·sec, and thereafter develops along the latter line, which indicates the constant density of slope spectrum. It is suggested that the nonlinearity of wind-waves must become stronger as wind-waves develop. The effective momentum flux _ws from the air flow to wind-waves in this stage is evaluated to be about 49% of the total stress ₀.     

Mean Vertical Distribution of the Dissipation Rate of Turbulent Energy in the Black Sea. Comparison with the Existing Models

We compare the results obtained by using theoretical and semiempirical models developed for the evaluation of the dissipation rate of turbulent energy in a stratified ocean with independent distribution of this quantity established by the authors for the active layer of the Black Sea (50–300 m) by using a one-dimensional model taking into account the balance of heat, salt, and fluid inside the layer. It is shown that, in a layer with gradual variation of the Väisälä–Brunt frequency N as a function of depth, the predominant sink of the energy of motion into dissipation N ² is ensured by the flow of energy through the spectrum of internal waves toward low frequencies and small vertical scales. On the contrary, in layers with abrupt drops of density as a function of depth (layers with jumps of density), an important role is played by the interface-type waves and the dependence of on N transforms into N .     

Thermolability of dehydrogenases from a psychrophilic marine bacterium

The heat lability of succinic dehydrogenase, malic dehydrogenase and lactate dehydrogenase in cell-free extracts ofVibrio marinus MP-1 grown at 15C was compared for the tris buffer suspended enzymes and the NaCl suspended enzymes. The tris buffer suspended enzymes lost 50 percent activity at low thermal exposure between 5C and 27C. No activity was evident on thermal exposure between 32C and 39C. The enzyme extracts suspended in NaCl at 36 % were more heat stable, losing 50 percent activity after exposure between 16C and 40C. The enzymes lost all activity on thermal exposure between 33C and 42C in the presence of NaCl.     

Practical Formulas for Intercoupling of Pressure and Depth in the Black Sea

On the basis of the generalization of the concept of standard ocean to the Black Sea, we deduce practical formulas for the conversion of pressure into depth and vice versa depending on the latitude of the place with regard for the equation of state for 1980. The error of these relations for the standard Black Sea (whose salinity is equal to 22.2 at a temperature of +9°C from the surface to the bottom) does not exceed ±0.2m and ±0.2dbar. The difference between the practical and actual depths in winter and summer periods does not exceed ±0.35m for depths varying within range 0–2000m. The proposed practical formulas enable one to simplify the procedure of rapid evaluation of depth (or pressure) in real time by excluding the procedure of integration over a specific volume.     

Abundance and size composition of the summer phytoplankton communities in the western North Pacific Ocean,the Bering Sea,and the Gulf of Alaska

Chlorophylla concentrations (Chla) of size-fractionated phytoplankton samples were measured in the western North Pacific Ocean, the Bering Sea, and the Gulf of Alaska during the summer of 1986. Among samples collected in the upper 100 m (total of 210 samples), 207 samples were dominated by micro- (>10 m) or picoplankton (<2 m) and only three samples were represented by nanoplankton (2–10 m). These 207 samples were classified based on the total Chla content into three types: Type H (>1.0 g l^–1), Type M (0.5–1.0 g l^–1), and Type L (<0.5 g l^–1). These types further divided into two subtypes (-p and-m), depending upon dominancy of pico (-p) and microplankton (-m). The phytoplankton community was represented by Type L-p in the Gulf of Alaska, where 80% of the samples fell into this type. It was represented by Type M-p in the western North Pacific and the Oceanic Domain in the Bering Sea, where 53 and 41% of samples were identified as this type, respectively. In the Middle Domain of the Bering Sea, 68% of samples collected below the nitracline was Type H-m, which indicates blooms of microplanton. This type was also observed in the neritic waters near the Aleutian Islands. These types described above are consistent with a general trend that an increase in phytoplankton abundance is attributed to the growth of microplankton. An unusual type occurred above the nitracline of the Middle Domain, where microplankton prevailed, although the total Chla was less (Type L-m). This type represents a feature of late phase of an ice edge bloom. Another unusual type was found mainly in the Outer Domain of the Bering Sea, where the total Chla was high and picoplankton prevailed (Type H-p). The predominance of picoplankton seems to result from the heavy grazing intensity of large calanoid copepods upon microplankton but not upon picoplankton     

The mechanism of the development of wind-wave spectra

The mechanism of the development of wind-waves will be proposed on the basis of the observed wave spectra in the wind tunnels and at Lake Biwa (Imasato, 1976). It consists of two aspects: One is that the air flow over the wind-waves transfers momentum concentratively to the steepest component waves and the other is that the upper limit of the growth of a wave spectral density is given by the ultimate value in the slope spectral density. The first aspect means that the wave field has the momentum transfer filter on receiving the momentum from the air flow. Wind-waves in the stage of sea-waves receive the necessary amount of momentum by the form drag,e.g. according to the Miles' (1960) inviscid mechanism, through a very narrow frequency region around a dominant spectral peak. On the other hand, wind-waves in the stage of initial-wavelets receive it according to the Miles' (1962a) viscous model through a fairly broad frequency region around the peak. The upper limit ofS _max developing according to viscous mechanism is given byS _max =6.40×10^–4 k _max ^–2cm²s andS _max =2.03C(f _max )^–2cm²s(S _max is the power density of the wave spectral peak with the frequencyf _max ,k _max is the wave number corresponding to the frequencyf _max andC is the phase velocity).From the second aspect, the upper limit of the growth of wave spectral density is given by 33.3f ^–4cm²s in the frequency region of late stage of sea-waves. Therefore, the spectral peak, which has the largest value in the slope spectral density in the component waves of the wave spectrum, rises high over the line 4.15f ^–5cm²s. The energy is transported from the spectral peak to the high frequency part and to the forward face of a wave spectrum by nonlinear wave-wave interaction. This nonlinearity is confirmed by the bispectra calculated from the observed wind-wave data. In the stage of sea-waves, nonlinear rearrangement of the wave energy comes from a narrow momentum transfer filter, and, in the stage of initial-wavelets, it comes mainly from small corrugations and small steepness of the wave field.     

Parameterization of the dispersion relation of internal waves using the data of hydrological soundings in the Tropical Atlantic

Dependences have been determined which connect the parameters of the dispersion relation of the lowest mode of internal waves with the integral characteristics of the seasonal thermocline when 10 min30 min, 20 mh150 m, and 0·4 m²/s² Q5·2 m²/s².Translated by Mikhail M. Trufanov.     

New constraints on the width of the zone of active faulting on the East Pacific Rise 8° 30′ N – 10° 00′ N from Sea Beam Bathymetry and SeaMARC II Side-scan Sonar

Sea Beam bathymetry and SeaMARC II side-scan sonar data are used to constrain the width of the zone of active faulting (plate boundary zone) to be 90 km (0.8 Ma) wide along the East Pacific Rise 8° 30N – 10° 00N. Fault scarps, identified on the basis of contoured, shaded relief and slope intensity maps of bathymetry, are measured. These scarp measurements, used in conjunction with data from a separate near-axis study, show that both inward- and outward-facing fault scarps increase in height away from the ridge axis, reaching average heights of 100 m at 0.8±0.2 Ma, 45±10 km from the ridge axis. Beyond this distance, there is no significant increase in scarp height. Earlier studies had suggested that the width of the zone of active faulting for outward-dipping faults might be significantly narrower than for inward-dipping faults. A lower crustal decoupling zone between brittle crust and strong upper mantle is predicted to exist out to 20–200 km from the ridge based on previously published lithospheric models. Such a decoupling zone may explain why outward-dipping faults continue to be active as far off-axis as inward-dipping faults. If the width of the zone of active faulting is controlled by the width of a lower crustal decoupling zone, our observations predict an 90 km wide decoupling zone in the lower oceanic crust at this location.     

Reflection and breaking of internal waves on a sloping beach

The reflection and breaking of internal waves on a sloping beach were studied in a small wavetank filled with water and petroleum. The dependence of the reflection coefficient of the internal waves on wave steepness and on beach slope is found to be very similar to that of surface waves. The reflection coefficient is small for the very gentle slope, increases rapidly as the slope increases, and becomes almost constant for the steep slope. The reflection coefficient decreases with increase of the wave steepness. Also, the transition slope at which the coefficient curve has the maximum gradient increases with increase of the wave steepness. Breaking pattern of the internal waves is classified into four types; breaking, semi-breaking, wrinkle-generating, and non-breaking. Their dependence on beach slope and wave steepness is examined. The regular sequence of the four breaking types from breaking to non-breaking is observed with decrease of wave steepness or with increase of beach slope.     

The content of selenium and its chemical form in sea water

By using the new fluorometric method of determination of the total selenium ( Se), Se (IV) and Se (VI), the content of selenium in sea weter was determined in the western North Pacific. Results showed that the content of Se in surface water ranged from 0.06 to 0.12g l^–1, while in deeper layers, the content increased to 0.20g l^–1. It was found that Se (IV) showed rather uniform distribution with depth, while Se (VI) increased with depth to about three times that in the surface. The ratio of Se (IV) to the Se ranged from 0.5 to 0.8 in the surface and 0.4 to 0.6 in the deep. The coexistence of the hexa- and tetravalent ions of selenium was confirmed both in surface and deep layers. Some results of observations on the content of selenium in the coastal areas of Japan were also reported.     

Distribution and chemistry of manganese,iron, and suspended particulates in Orca Basin

The intense halocline and redoxcline in the Orca Basin, northwest Gulf of Mexico, induce dramatic water column profiles for manganese, iron, and suspended particulates. Within a 17 m interval, the salinity of the basin water increases from 66 to 260 & permil and dissolved oxygen decreases to zero. Midway through this transition zone, concentrations of suspended matter peak at 900 g/liter. Dissolved iron and manganese concentrations in the anoxic brine increase from oceanic values to maxima of 1.6 and 22 mg/liter, respectively. Upward migration of dissolved manganese from the brine leads to production of manganese-rich particles in the slightly oxygenated overlying water.     

Morphology of largeHalimeda bioherms,eastern Java sea (Indonesia): A side-scan sonar study

The most extensive and thickestHalimeda bioherms reported from modern seas occur along both open and protected margins of Kalukalukuang Bank, eastern Java Sea (Indonesia). Seismic profiles suggest these features average 20 to 30 m thick (maximum 50 m) and developed over large areas by coalescence of individual mounds. Bioherm morphologies range from numerous small mounds ( 10–20 m diameter) through hay-stack features ( 100 m diameter) to broad swells. Some modern bank bioherms display surface forms that appear related to onbank flow from Makassar Strait. Upwelling of cold, nutritive water is likely responsible for unusualHalimeda productivity and large bioherm development.     

High-resolution seismic study of modern fine-grained deposits: Inner shelf off the southeastern coast of Korea

The geometry and internal structures of modern sediments on the inner shelf off the southeastern coast of Korea were investigated by means of analysing high-frequency (3.5 kHz) seismic records. The records reveal a wedge-shaped sediment body, tapering off toward the sea. On the basis of reflection patterns, the sediments can be classified into two units; foreset (prodelta) unit and bottomset unit, consisting of sandy muds and clays, respectively. The lateral transition from foreset to bottomset deposits suggests a prograding delta system of the Nakdong River since the late Holocene.     

Classification of “siome”, streaks and fronts

Siome, which was firstly defined by Uda (1938); is a line of convergence on the sea surface. There are many kinds of siome in the sea. I propose in this paper that siome should be classified into streak and front. Streak is defined as the convergence within the same water mass and front the convergence between two different water masses. Streaks and fronts are classified into more details on the basis of their mechanisms of generation. The proposed classification will be useful for understanding the dynamics of siome and should help to promote interdisciplinary studies around siome regions.     

Volume transport of the western boundary current penetrating into a marginal sea

The amount of penetration of a western boundary current into a marginal sea which is connected to an open ocean by two narrow straits is estimated from a linear, steady and barotropic theoretical model. In this model the western boundary current in the open ocean is driven by a wind stress imposed at the sea surface. The inflow of the water of the open ocean into the marginal sea is caused by the pressure difference between two straits produced by the wind-driven circulation in the open ocean.Main external parameters are combined into two non-dimensional parameters; and (the ratio of the depth of the marginal sea to that of the open ocean), whereb is the distance between north and south boundaries of the ocean,D ₀ is the depth of the open ocean, is the latitudinal variation of the Coriolis parameter andR is the coefficient of friction. The friction is assumed to be proportional to the flow velocity.In the limit of infinite the volume transport into the marginal sea is not affected by the width of two straits and . It is mainly controlled by the wind stress and the positions of two straits. For finite values of , however, the volume transport depends considerably on and the width of the straits.Guided by both this model and physical considerations, we obtained a relation between the volume transport into the marginal sea and the external parameters. This relation predicts that about 2 % of the volume transport of the Kuroshio penetrates into the Japan Sea.     

Kinetics of nitrate and ammonium uptake by the natural populations of marine phytoplankton in the surface water of the Oyashio region during spring and summer

The maximum uptake rate (_max) and affinity constant (K _s) for nitrate and ammonium were estimated in the surface water of offshore Oyashio in May (spring) and September (summer), 1990. The average _max/Chl.a for ammonium was 2.1 times larger than that of nitrate in both seasons. The average _max/Chl.a for both nitrogens were 3.5 times larger in summer than in spring. Water temperature and size composition of phytoplankton population were related to the seasonal difference in the _max/Chl.a. Phytoplankton population showed high affinity for both nitrogens in the spring and summer. In addition, the contribution of new production to total production was estimated by _max[_max–No₃/(_max–NO₃+_max–NH₄)]. The spring value was in the range of 0.26 to 0.45 (mean±SD=0.35±0.092), and the values in spring bloom were especially a little over 0.4. The summer value was in the range of 0.30 to 0.37 (0.34±0.04).     

Organic geochemistry of the Japan Sea sediments-1: Bulk organic matter and hydrocarbon analyses of Core KH-79-3, C-3 from the Oki Ridge for paleoenvironment assessments

Organic geochemical study of bulk organic matter (OM), hopanoid hydrocarbon and normal hydrocarbon (C₂₃C₃₅) was conducted for a 936-cm-long sediment core sample from the Oki Ridge of the Japan Sea (Core KH-79-3, C-3; 37°03.5 N, 134°42.6E, water depth 935 m). Stable carbon isotopic ratios were also measured for both bulk OM and individual hydrocarbons. The following results were obtained: (1) The weight ratios of total organic carbon to total nitrogen range from 6.2 to 9.4 in the core. The ¹³C values of bulk OM range from –25.1–20.7%.. The ¹³C values of OM in the sections of 140190 cm are lower (–25–24) than those in the other sections (–23–21). This result indicates that OM in the core except for the 140190 cm sections is essentially of marine origin. (2) The ¹³C value of diploptene (a hopanoid hydrocarbon) in the last glacial maximum (LGM), is –66.3 (vs. PDB), which indicates it originating in methanotrophic bacteria. This result provides evidence to support for the previous ideas (Oba et al., 1980, 1984; Masuzawa and Kitano, 1984) that the bottom waters in the Japan Sea were anoxic in LGM. (3) Long chain (C₂₃C₃₅) n-alkanes of higher-plant wax origin were found throughout the core. Their concentration is high in 140190 cm in depth, suggesting that eolian dust load was high in LGM. (4) The n-alkane/TOC ratio increases with decreasing ¹³C values of bulk OM. This result indicates that the load of terrestrial (probably eolian dust-derived) OM to the Japan Sea became higher in colder climates. (5) The CPI values of long-chain n-alkanes are different in different ¹³O stages of paleoclimate, probably reflecting variations in species of terrestrial higher plants as a result of climatological adaptations.     

Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment

Carbon and nitrogen stable isotope ratios (¹³C and ¹⁵N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The ¹³C and ¹⁵N of surface sediments in the estuary of the Yodo River were less than –23 and 5 respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving ¹³C of about –20 and ¹⁵N about 6). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.     

A stratigraphic and tectonofacies framework of the “calcari aLucina” in the Apennine Chain,Italy

The Apennine Chain provides the first example of stratigraphic (time) and synsedimentary tectonic (space) distribution of the calcari aLucina Miocene equivalents of modern cold-vent carbonates. Chemosynthetic faunal assemblages and related carbonate deposits are found at different stratigraphic levels, with peaks during Langhian-Serravallian and late Tortonian-early Messinian times. A general increase in frequency and volume occurs with time. A genetic link between venting and the Messinian Evaporite event is difficult to demonstrate. However,Lucina limestones are limited to preevaporitic times, and their maximum abundance is reached just before the onset of the Messinian Evaporite accumulation.Lucina limestones occur in almost all tectofacies of the orogen, from backland to foreland.