Evolution of an isolated eddy near a coast and its relevance to the “Kyucho”

The evolution of an isolated meso-scale eddy near a coast is studied numerically. In particular, it is found that the translation speed of the adjusted eddy is estimated well by the mutual induction mechanism adapted to a rotating stratified fluid. The nonlinear Kelvin wave excited during the adjustment process is also discussed in connection with the Kyucho, the sudden warming of coastal waters associated with swift currents.     

Transmission and reflection of planetary and topographic Rossby waves in a two-layer ocean

Transmission and reflection problems when kissing≓ occurs among planetary and topographic Rossby waves in a two-layer ocean are studied. The slope parameterS(=dh ₂/dx, whereh ₂is the thickness of the lower layer) is assumed to have constant values in the regionsx 0 andxL and to vary linearly with the increase ofx in the region0xL (refer to Fig. 2 in the text). Furthermore, a wave is entered fromx=– and kissing is assumed to occur in the region (0<)x _axx_b(<L).It is found that a wave of the same type as the incident wave is mainly transmitted when the width of the region in which kissing occurs,L _kiss(=tx _b–x_a), is smaller than _kiss=2/(¦K¦+ _y/2), whereK is a representative wavenumber in the regionx _ab, _y is they-component of , and is the frequency. WhenL _kiss is larger than _kiss, on the other hand, the main wave transmitted is of a different type to the incident wave. As an application, transmission and reflection problems of planetary Rossby waves are considered, and it is shown that when an external (internal) planetary Rossby wave is entered, an internal (external) one can be transmitted due to the effect of kissing.     

Variation of water system distribution in the Sanriku Coastal Area

We analyzed hydrographic data obtained monthly by the Iwate Prefectural Fisheries Laboratory during 1977–1981. Our attention was focussed on the classification of waters based on the Temperature-Salinity (T-S) scatter diagram analyses, and on the extraction of the mean state of their distribution for each season. The water system was defined as all waters occupying some specific region on the T-S plane, and the mean state for each season was expressed by the distribution of the mode water systems (i.e., the most commonly occuring water system).Because of the coexistence of the Tsugaru Warm Current, the Oyashio and the Kuroshio, and their large seasonal variability, the sea waters had a wide variety of T-S combinations. The detailed T-S scatter diagram analyses allowed us to classify the waters into six water systems. A time-longitude diagram of water systems and the distribution of mode water systems are presented. The latter showed clear seasonal variations of the Tsugaru Warm Current and the Oyashio.Though the water system analysis was successfully able to present the distribution of the various waters in the Sanriku Coastal Area and to clearly extract the mean state of sea conditions, it was found that the classification of water systems on the T-S plane was not complete in all cases for this area.     

Mud waves at Deep Sea Drilling Project Site 603, US Atlantic lower continental rise

An extensive field of mud waves occupies the Lower Continental Rise, east of Cape Hatteras, USA. Seismic profiles at Deep Sea Drilling Project Site 603 show that they have migrated upcurrent at a steadily decreasing rate, until a standing wave phase was established in the Quaternary. The growth of the waves was terminated between the early Pleistocene and Holocene by an erosional event(s). Erosion was greatest on the downcurrent sides of the waves causing an apparent upcurrent migration at the surface. It is suggested that erosion may have played a significant part in the migration of the deeper waves at Site 603.     

Studies on the dissolution of diatomaceous silica as a function of heating

Diatomaceous silica, pretreated at various temperatures between 125 and 900C, was subjected to dissolution experiments and was analyzed using X-ray diffraction and infrared spectra. The diatomaceous silica preheated up to 900C, dissolved throughly into the solution of 2 per cent Na₂CO₃. On the digestion in the solution of 2 per cent Na₂SO₄, the dissolution of the silica decreased as the pretreating temperature increase; the degree of dissolution was different for various species. According to infrared absorption studies, the diatomaceous silica pretreated at a temperature below 500C preserved the reversibility of dehydration-rehydration almost qualitatively, while heating above 500C the samples lost the reversibility. Deformation of some kinks of diatomaceous silica pretreated above 500C, was percepted on infrared absorption spectra around 1,150 cm^–1. The samples pretreated up to 900 C, however, did not show such an internal structural change as could be identified by the X-ray diffraction analysis. The content of Al and Fe in diatomaceous silica was low and have not much difference in quality among diatom species. From these experimental results, it was adequately understandable that diatomaceous silica, which has a metastable character, is variable in the silica forms among species and its process and rate of transformation of internal structure and/or surface sites by the treatment at given temperatures also show differences.     

Anomalously large marine sedimentary units deposited in a single mass wasting event

This note serves to introduce a group of papers centered around the theme of massive submarine gravity deposits, megaturbidites, presented in a 1986 AAPG/SEPM Symposium organized by Larry J. Doyle and Robert Bourrouilh. Although megaturbidite may be an unfortunate term, massive gravity deposits are significant as marker beds, time lines, and potential hydrocarbon reservoirs, as well as being manifestations of important geological phenomena. The papers which follow begin to explore the inter-relationships among the four principal variables: time, basin size and shape, tectonic setting, and sediment accumulation in the provenance areas, which govern the formation of these extraordinary units.     

Error of digitization of multidimensional random hydrophysical fields with power spectra

Exact and approximate formulae are proposed to evaluate the errors of spatial/temporal digitization (aliasing) of then-dimensional random fields withm-power spectra atn=1, , 4 and 1m5, which satisfactorily approximate temperature, velocity, density, and other fields in the sea and atmosphere.Translated by Vladimir A. Puchkin.     

Occurrence of coprostanol, 24-ethylcoprostanol and 5α-stanols in the marine sediments

The present study deals with the elucidation of sterol composition of the marine sediments in Kagoshima Bay. The identification of each sterol was performed by gas-liquid chromatography, Ag⁺ impregnated column chromatography, mass spectrometry, and nuclear magnetic resonance spectrometry. The sediment obtained near the estuary of River Koutsuki contained large portions of 5-stanols such as coprostanol and 24-ethylcoprostanol basides 5-stanols such as cholestanol, 24-methylcholestanol, and 24-ethylcholestanol in the sterol fraction. These 5-stanols in the marine sediment may be derived from the fecal contamination by domestic sewages.     

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.     

Rates of net assimilation and respiration of amino acids by marine bacteria

The selectivity of amino acid assimilation by marine bacteria was examined using seven kinds of¹⁴C-amino acids and the acid hydrolysate of¹⁴C-labelled proteins. It was found that the net assimilation and respiration by marine bacteria followed MICHAELIS-MENTEN kinetics for all of amino acids used in our experiments. Maximum velocities of amino acids were 0.01 to 0.19g carbon/hour per 2×10⁷ cells for net assimilation and less than 0.18g carbon/hour per 2×10⁷ cells for respiration at 20C. The velocity of gross assimilation was found with the following order: phenylalanine>valine, glutamic acid>serine, arginine>tryptophan>glycine. The assimilation velocities of amino acids in these laboratory works showed almost the same order as those in field experiments. The assimilation velocity of an amino acid was influenced by coexisting another amino acids or glucose. The assimilation velocity in lower substrate range of amino acids was directly proportional to the number of bacterial cells in the range from 6×10² to 3×10⁴ cells per ml. No linear relation between the assimilation velocity of amino acids and reciprocal of absolute temperature was found, but a marked bending was observed at 15 to 20C. The velocity at the optimum temperature was three to six times of that at 5C.     

Iodine in the surface water of the ocean

Iodine in sea water of the Pacific was determined with special interest in the relation between iodide and iodate in the surface water of the ocean. The result was discussed with reference to the mechanism of iodide formation proposed byTsunogai andSase. The concentration of iodide varies widely from the lower value than the detection limit to 0.21g at./l, while the concentration of total iodine is nearly constant and the mean value is 0.41g at./l. The vertical profile of iodide often shows the maximum in the surface layer. In the surface layer, the concentration of iodide is higher in warm water (0,10g at./l on the average) than that in cold water of lower temperature than 20° C (0.03g at/l). The highest concentration of iodide among the warm waters is found in the surface water of the equatorial area (0.13g at./l) where the biological productivity is also high. Iodide is generally more enriched in the water having higher biological activity even in the cold water. These results are considered to be compatible with the mechanism of iodide formation proposed.     

Global distribution and atmospheric transport of chlorinated hydrocarbons: HCH (BHC) isomers and DDT compounds in the Western Pacific,Eastern Indian and Antarctic Oceans

Concentrations of chlorinated hydrocarbons such as HCH isomers and DDT compounds were determined in air and surface water samples taken from the Western Pacific, Eastern Indian and Antarctic Oceans. The most interesting finding was their presence in measurable concentrations in the Antarctic Ocean. Chlorinated hydrocarbon pesticides are widely distributed in the open ocean environment over both the northern and southern hemispheres, and some characteristic distribution patterns of pesticide species in different oceanic regions were observed both in air and water samples. HCH residues found in the northern hemisphere were much higher in concentration than those in the southern hemisphere. On the other hand, higher concentrations of DDT residues were found in the tropical regions, but their levels were not so different between both the northern and southern hemispheres. HCH isomers found in the northern hemisphere had the following order of concentrations:-HCH> HCH>-HCH, while in the southern hemisphere-HCH was apparently dominant. DDT compound compositions were rather uniform in all the oceans surveyed, and more than 50% wasp,p-DDT. These facts can be explained by the world wide situation regarding pesticide use and the physicochemical properties of the pesticides such as their vapor pressures and water solubilities. In addition, the meridional circulation of the atmosphere, particularly the mass flows of the Hadley and Ferrel cells in the troposphere, also contributes to the atmospheric transport and global distribution of these pesticides.     

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.     

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.     

Variability of the axial morphology and of the gravity structure along the Central Spreading Ridge (North Fiji Basin): evidence for contrasting thermal regimes

The Central Spreading Ridge (CSR) is located in the central part of the North Fiji Basin, a complex back-arc basin created 12 Ma ago between the Pacific and Indo-Australian plates. The 3.5 Ma old CSR is the best developed, for both structure and magmatism, of all the spreading centers identified in the basin, and may be one of the largest spreading systems of the west Pacific back-arc basins. It is more than 800 km long and 50–60 km wide, and has been intensively explored during the French-Japanese STARMER project (1987–1991).The CSR is segmented into three first order segments named, from north to south, N160°, N15° and N-S according to their orientation. This segmentation pattern is similar to that found at mid-ocean ridges. The calculated spreading rate is intermediate and ranges from 83 mm/yr at 20°30 S to 50 mm/yr at 17°S. In addition, there is a change in the axial ridge morphology and gravity structure between the northern and southern sections of the CSR. The axial morphology changes from a deep rift valley (N160° segment), to a dome split by an axial graben (N15° segment) and to a rectangular flat top high (N-S segment). The Mantle Bouguer Anomalies obtained on the northern part of the CSR (N160°/N15° segments) show bull's eye structures associated with mantle upwelling at the 16°50S triple junction and also in the middle of the segments. The Mantle Bouguer Anomalies of the southern part of the ridge (N-S segment) are more homogeneous and consistent with the observed smooth topography associated with axial isostatic compensation.At these intermediate spreading rates the contrast in bathymetry and gravity structure between the segments may reflect differences in heat supply. We suggest that the N160° and N15° segments are cold with respect to the hot N-S segment. We use a non-steady-state thermal model to test this hypothesis. In this model, the accretion is simulated as a nearly steady-state seafloor spreading upon which are superimposed periodic thermal inputs. With the measured spreading rate of 50 mm/yr, a cooling cycle of 200,000 yr develops a thermal state that permits to explain the axial morphology and gravity structure observed on the N160° segment. A spreading rate of 83 mm/yr and a cooling cycle of 120,000 yr would generate the optimal thermal structure to explain the characteristics of the N-S segment. The boundaries between the hot N-S segment and its cold bounding segments are the 18°10 S and 20°30 S propagating rifts. A heat propagation event along the N-S segment at the expense of the adjacent colder failing segments, can explain the sharp changes in the observed morphology and structure between the segments.     

Internal wave dispersion in deep oceans calculated by means of two-variable expansion techniques

An analytical study is made of linearized internal wave dispersion relation in a density-stratified deep ocean with aN(z) profile which contains turning points. Principal emphasis is placed on obtaining the-k relationship for all frequencies. Taking advantage of the largeness of the nondimensional wavenumber (kS1), the mathematical tool to attack the governing Sturm-Liouville equation is a combination of the two-variable expansion (valid far away from the turning point) and the limit-process expansion (valid in the neighborhood of the turning point). The matching conditions for these two expansion schemes provide the desired-k relationship. A numerical example of this method demonstrates satisfactory agreement with the results obtained by the strict analytical solution and the multi-layered matrix numerical model.     

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.     

Some remarks on the spectrum of rapid-changing random data in the ocean

Spectral characteristics of rapid-changing random data in the ocean are discussed. Analysis shows that, if records are approximated by saw-toothed random series ₁ and step series ₂, ₁ and ₂ generally have spectral ranges of the –4th power and –2nd power, respectively, with respect to frequency (or wave number).     

On nonlinear sea waves and the induced mean flow

The nonlinear modulation of water wave groups is investigated and the interaction equations with induced flows are obtained. The analysis is performed up to the third order of the wave steepness a by treating it as a small parameter in the singular perturbation technique by means of the Krylov-Bogoliubov-Mitropolski method. The equation which governs the development of the wave envelope is found by a modification of the ordinary nonlinear Schroedinger equation for the case of uniform depth. The equations governing the behavior of the induced mean flow are examined by deriving the second order flow when the form of the modulated wave train is prescribed. The present theory can describe the mean flow caused by the radiation stress. Some applications containing the monochromatic wave instability are given to confirm the theoretical results.An outline of this paper was presented at The Ocean Surface Symposium (Sendai, 1984).     

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.