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.     

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.     

Dissolved carbon and 33-133-133-1anomalies in the water column caused by hydrocarbon seeps on the northwestern Gulf of Mexico slope

Alkalinity, dissolved inorganic carbon (DIC), and ¹³C profiles from seep sites on the northwestern Gulf of Mexico upper slope show anomalously negative ¹³C values of up to –4.5 PDB, increased levels of DIC of up to 2.45 mmole/liter, and slight alkalinity rises of up to 2.54 meq/liter, relative to water column profiles from a seep-free site (0.63, 2.04 mmole/liter, and 2.39 meq/liter). The observed DIC enrichments coupled with the¹³C-depletions are attributed to the release of CO₂ by microbial oxidation of crude oil in the seep environment, and its migration into the water column. The ¹³C composition of the migrating CO₂ is estimated to be –26.0 on the basis of dissolved carbon inventory. Manifestation of DIC and ¹³C anomalies in the water column caused by hydrocarbon seepage holds promise to be useful for hydrocarbon reconnaissance surveys over large offshore tracts on account of the simplicity of sampling acquisition, and rapidity of analytical techniques in the laboratory.     

Glacial to Holoceneδ 13C variations in intermediate depth water masses of North Indian Ocean

The ¹⁸O and ¹³C compositions of glacial- to Holocene-aged benthic foraminifera in a core collected from the eastern Arabian sea (water depth 1230 m) were determined to investigate glacial—interglacial variations in the intermediate depth water chemistry of the North Indian Ocean. In addition, we determined the ¹³C composition of Holocene benthic foraminifera from seven cores for which the ¹⁸O and ¹³C of benthic foraminifera from last glacial maximum (LGM) were reported by Kallel et al. (1988). The ¹³C_DIC in the intermediate waters was generally depleted by 0.3–0.4 during the last glacial maximum compared to Holocene.     

δ15N of PON and Nitrate as a Clue to the Origin and Transformation of Nitrogen in the Subarctic North Pacific and Its Marginal Sea

Nitrogen isotope compositions of particulate organic matter and nitrate were analyzed for seawater sampled at five stations at the Alaskan Gyre, Western Subarctic Gyre and East China Sea, focusing on the samples from the surface to 5000 m water to characterize the nitrogen cycling in the subarctic North Pacific Ocean and its marginal sea. The ¹⁵N of particulate organic matter showed little agreement with a conceptual closed model that interprets isotopic variation as being caused by isotope discrimination on nitrate utilization. The ¹⁵N and ¹³C of particulate organic matter varied with the water depth. A correlation between isotope compositions and C/N elemental ratio was found generally at all stations, although some irregular data were also found in deep layers. We developed a hypothetical nitrogen balance model based on N₂ fixation and denitrification in seawater and attempted to apply it to distinguish nutrient cycling using both ¹⁵N-NO₃ ^– and N* variation in seawater. This model was applied to the observed data set of ¹⁵N-NO₃ ^– and N* in the North Pacific water and estimated the ¹⁵N-NO₃ ^– of primordial nitrate in the North Pacific deep water as 4.8. The North Pacific intermediate water for all stations showed similar ¹⁵N-NO₃ ^– and N* values of 6 and –3 µmol/kg, respectively, suggesting a similar nitrogen biogeochemistry. In the East China Sea, analysis showed evidence of water exchange with the North Pacific intermediate water but a significant influence of nitrogen from the river runoff was found in depths shallower than 400 m.     

Deglaciation and meltwater events in hudson strait and the Eastern Canadian Arctic

Stable isotope measurements on molluses from raised marine deposits, and on foraminifera in a piston core, define a series of light isotope events. A major event is¹⁴C dated at ca. 10.3 ka and is correlated with a marked isotopic excursion in HU77-021-156. This event is followed by a dramatic rise in diatom and, slightly later, in benthic foraminiferal abundances. Molluses record another light event around 8 ka. Major fluctuations in both ¹⁸O and ¹³C around 10.3 ka suggests that the Hudson Strait ice stream may have responded to the Younger Dryas climatic oscillation.     

Geophysical and geochemical observations on actively seeping hydrocarbon gases on the south-eastern Yellow Sea continental shelf

In the southeastern Yellow Sea, active seepage of hydrocarbon gases has been observed by high-resolution (3.5 kHz) seismic profiling both in 1987 and 2001, occurring through a large number of plumes from the topmost pre-Holocene sedimentary layer. It is strong enough to compensate for current speed, extending vertically up to the sea surface. The gas seepage often appears to be explosive to form craters and diapirs, although pockmarks are rare due to the redistribution of mobile palimpsest sands. In core-top seawater and sediments, the gases are characterized by high amounts of C₂, homogenous ¹³C₁ values and a large difference (19.7 on average) between ¹³C₁ (–55.2 to –53.6 PDB) and ¹³C₂ (–36.8 to –32.5 PDB) values. The gases are considered to be generated with a smaller amount of C₁ at the early thermal cracking stage of labile source materials, after which the C₂ gas is enriched in ¹³C by diffusion or biological alternation at the generation or accumulation site. The homogenous ¹³C₁ values may be one of the geochemical characteristics of gases acquired at depth which are less altered in the case of rapid diffusive gas migration to the seafloor.     

The chemical states of iron in marine sediments by means of Mössbauer spectroscopy in combination with chemical leachings

The chemical states of iron in near-shore and deep-sea sediments were investigated by means of⁵⁷Fe Mössbauer spectroscopy in combination with selective and nonselective chemical leachings. As far as a limited number of the sediments analyzed are concerned, Mössbauer spectra of near-shore sediments consist of high-spin paramgnetic ferrous (=1.13 mm/s, Eq=2.65 mm/s) and paramagnetic ferric (=0.35 mm/s, Eq=0.64 mm/s) components, while those of deep-sea sediments are composed of high-spin paramagnetic ferrous, paramagnetic ferrous, paramagnetic ferric and magnetic ferric (0.4 mm/s,H510 KG) components. The Fe²⁺/Fe³⁺ ratios of deepsea sediments are much smaller than those in near-shore sediments, while the total contents of iron in the former are much higher than those in the latter. This is principally due to the high contents of authigenic ferric oxides in deep-sea sediments. Further, in the aluminosilicate fraction, the Fe²⁺/Fe³⁺ ratios of deep-sea sediments are also smaller than those of near-shore sediments. This is probably attributed to high contents of clay minerals and authigenic aluminosilicates in deep-sea sediments relative to near-shore ones. The magnetic components in deepsea sediments are attributable to hematite, magnetite and/or maghemite.     

Stable oxygen isotopes as recorders of salinity and river discharge in the German Bight,North Sea

A high-resolution sediment core (sedimentation rate ~2 mm/year) from the German Bight was analysed for its foraminiferal stable oxygen isotope (¹⁸O) composition. These data were correlated with instrumental summer sea-surface temperature and salinity data from the nearby island of Helgoland, reaching back 100 years. Comparing the isotope data with the instrumental records reveals a distinct ¹⁸O–salinity relationship (¹⁸O=0.34×S–9.36; r=0.86) for the German Bight, where salinity is mainly driven by freshwater input from the Elbe River. Thus, these findings provide the possibility for future regional paleosalinity and paleodischarge reconstructions for times far beyond the instrumental timescale.     

Microbial Diversity in Nankai Trough Sediments at a Depth of 3,843 m

Dense populations of bivalves, primarily Calyptogena sp., were observed at cold seeps of the Nankai Trough. Bacterial input to the sediment was estimated through determination of phospholipid ester-linked fatty acid (PLFA) and DNA profiles. Results indicated a bacterial biomass of 10⁹ cells (g dry wt)^-1 while individual fatty acid profiles revealed a predominance of monounsaturated fatty acids, mainly 18:1 isomers. The presence of these fatty acids can be interpreted to reflect a response to low temperature and a predominance of psychrophilic bacteria. DNA fragments encoding bacterial ribosomal RNA small-subunit sequences (16S rDNA) were amplified by the polymerase chain reaction method using DNA extracted directly from the sediment samples. From the sequencing results, at least 19 kinds of bacterial 16S rDNAs related to mostly the Proteobacteria and a few gram-positive bacteria were identified. These results suggest that the bacterial community in the Nankai Trough sediments consists of mainly bacteria belonging to the Proteobacteria , , and subdivisions. Bacteria belonging to the and subdivisions, which are known to include epibiont and sulfate reducing bacteria, respectively, were mostly detected in the sediment obtained from inside the area of the Calyptogena community, and the -Proteobacteria may function to supply reduced sulfur to bacterial endosymbionts of Calyptogena.     

Palaeo-carbonate seep structures above an oil reservoir, Gryphon Field, Tertiary, North Sea

Petrographic and geochemical analyses performed on a North Sea core from the Gryphon Field reveal the presence of palaeo-degassing features surrounded by injected sandstones in the Eocene interval. The injected sandstones are oil-stained and poorly cemented by carbonate and quartz. ¹⁸O isotope analyses indicate that carbonate cementation occurred during shallow burial (likely less than about 300 m). Depleted ¹³C (around –30 V-PDB) carbonate cement suggests that bicarbonate was derived from the microbial oxidation of oil and gas. Late quartz overgrowths enclose oil present in the injected units. The tubular degassing conduits are composed of zoned cements and have ¹⁸O and ¹³C isotope values similar to the injected sandstones, indicating that oil and gas seepage induced the precipitation of authigenic carbonate in the shallow subsurface. Oil inclusions in inter- and intra-crystal cement sites in both injected sandstones and degassing conduits indicate that oil seepage was an ongoing feature at shallow burial. A proposed model involves oil and gas seepage and the formation of the degassing conduits, followed by a sand injection phase. It seems likely that oil and gas continued to leak towards the seabed by exploiting the network of permeable injected sandstones and the horizons of porous degassing features.     

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.     

Bathymetric reconstructions of the Miocene-age “calcari aLucina” (northern Apennines,Italy) from oxygen isotopes and benthic Foraminifera

Two independent methods of paleobathymetry, applicable to hydrocarbon-derived carbonates, are explored in this study. The oxygen isotope method exploits the temperature decline with depth that leaves a measurable imprint on the ¹⁸O composition of pristine products of venting comprised of aragonites and dolomites. The other method makes use of the bathymetric preferences of benthic foraminiferal taxa entrapped in the carbonate buildups. These two methods were tested on the calcari aLucina limestones hosted in turbidites and mudstones infilling the Miocene-age Marnoso-arenacea basin. The limestone blocks, rich in fossils of chemosymbiotic-like fauna, preserve a 10-Ma record of hydrocarbon venting from Langhian to lower Messinian times. Our results indicate that carbonate accretion and lithification occurred at upper bathyal depths in waters not shallower than 200–250 m. The ¹⁸O of venting products contains the imprints of profound hydrographic changes that occurred in the ancient Mediterranean basin from the lower Serravallian to the lower Messinian.     

The evolution of isolated vortices interacted with steep slope

Numerical solutions are examined for isolated, intense vortices as influenced by western bounding bottom topography through the use of a rigid-lid, two-layer primitive -plane numerical model. Systematic studies are made of the sense of rotation (cyclonic/anticyclonic), the consequence of varying the gradient of bottom slope, and the different vertical shear in a two layer ocean. In the basin with a bottom slope, the nearly barotropic anticyclonic vortex forms a modon-like vortex for S with fixedRo ₂<O(1) (where is the ratio between the variation of the Coriolis parameter across the eddy to the Coriolis parameter in the center, S the topographic effect and,Ro ₂ the Rossby number in the lower layer) and its generation is due to a compound effect of the planetary beta, topographic beta, avvection, and mirror image. The formation of the modon-like vortex and the propagation of the original vortex onto the bottom slope depends on the strength of slope gradient and the baroclinicity of the vortex. The nearly barotropic anticyclonic vortex evolves into the stronger upper ocean one with increasing S: the gradient of the bottom slope becomes steeper. Then the original vortex lives longer because the barotropic component of the energy is converted to the baroclinic one and it moves toward southeast in forming a modon-like vortex in the lower layer. The evolution of a vortex in the model results are compared to observational results of a Kuroshio warm core ring (KWCR) obtained from hydrographic data (June, 1985) and from NOAA satellite infrared images (April, 1985 to July, 1985). It is shown that a KWCR (June, 1985) is influenced by the western continental slope/shelf of the East Japan.     

Radiation balance and heat budget at the ocean/atmosphere interface in the western North Pacific

The downward short- and long-wave radiation fluxes at the sea surface (S, L) were measured aboard the R/VHakuho Maru, University of Tokyo, for the period of 117 days on six cruises from 1981 to 1985 in the western North Pacific near Japan. The upward fluxes of short- and long-wave radiation (S, L) were calculated by Payne's (1972) table and the Stefan-Boltzmann's law, respectively. The sensible and laten heat fluxes (Q _h ,Q _e ) were also estimated from an aerodynamic bulk method.From April to August, the daily mean value ofS varied with the amplitude of 100200 Wm^–2. The value ofS was estimated approximately 6% ofS in all seasons. The difference betweenL andL was so small that the net radiation flux (Q _n ) was dominated byS. In addition, the net heat flux at the sea surface was also dominated byS due to small values ofQ _h andQ _e , and then the ocean was warmed at the rate of 111 Wm^–2 in April and 63 Wm^–2 in August in the Oyashio Area, and 132 Wm^–2 in May and 164 Wm^–2 in June in the Kuroshio Area, respectively.From September to March, a remarkable negative correlation between the day to day variation ofS and that ofL was observed except when an intense cold air outbreak occurred. It was found that the correlation was caused by the cloud climatological feature of the western North Pacific in this period.S was not a dominant factor in the net heat flux. The value ofQ _h +Q _e in the Kuroshio Area ranged from 260 Wm^–2 to 630 Wm^–2, much larger thanQ _n which ranged from –8 Wm^–2 to 92 Wm^–2 in the leg mean values (each leg period was about 10 days). Then the ocean was cooled at the rate of –160–620 Wm^–2 during this period. The net heat flux in the Kuroshio Area averaged over five legs from late November to February was –473 Wm^–2. This value is 50100% larger than the climatological values reported so far.The temporal and spatial variability of radiation fluxes and heat fluxes during each leg was also discussed.     

AOU as indicator of water-flow direction in the central North Pacific

Salinity, preformed phosphate and AOU distribution on the sigma-t surfaces of 26.8 and 27.3 of the central North Pacific Ocean, as well as the topography of these density surfaces, were studied. The direction of water flow suggested by the AOU distribution on these density surfaces was compared to that indicated by the acceleration potential contours on the _t =125 cl/ton and _t =80cl/ton surfaces drawn by Joseph L.Reid, Jr. The disagreements were explained in terms of mixing and possible gradients of primary production at the sea surface. On the 26.8 sigma-t surface a southward flow connecting the westward flow south of the Aleutian chain and the eastward flow farther south, between 175E and 180 is suggested by the AOU distribution but is not implied by the acceleration potential contours. If the circulation pattern at this density surface is similar to that at the sea surface, this southward flow is very likely to be real.     

Horizontal Pressure Gradient Errors of the Monterey Bay Sigma Coordinate Ocean Model with Various Grids

A coastal ocean -coordinate model of Monterey Bay (MOB) with realistic bottom topography and coastlines is developed using the Princeton Ocean Model (POM) and grid generation technique (GGT) to study the horizontal pressure gradient errors associated with the MOB steep topography. The submarine canyon in MOB features some of the steepest topography encountered anywhere in the world oceans. The MOB grids are designed using the EAGEAL View and GENIE⁺⁺ grid generation systems. A grid package developed by Ly and Luong (1993) is used in this study to couple grids to the model. The MOB model is tested with both orthogonal and curvilinear nearly-orthogonal (CNO) grids. The CNO grid has horizontal resolution which varies from 300 m to 2 km, while the resolution of the orthogonal grid is uniform with x = 1.25 km and y = 1.38 km. These grids cover a domain of 180 × 160 km with the same number of grid points of 131 × 131. Vertical resolutions of 25, 35 and 45 vertical sigma levels are tested. The error in the MOB are evaluated in terms of mean kinetic energy and velocity against various grids, vertical, horizontal resolution and distributions, and bottom topography smoothing. Simulations with various grids show that GGT can be used as another tool in reducing -coordinate errors in coastal ocean modeling besides increasing resolution and smoothing bottom topography. Topographical smoothing not only reduces topographic slope, but changes realistic topography. A CNO grid with a high grid density packed along steep slopes and Monterey Submarine Canyon reduces the errors by 40% compared to a rectangular grid with the same number of grid points. The CNO grid is more efficient than the rectangular grid, since it has most of its grids over water. The simulations show that the presented MOB -coordinate model can be used with a confidence regarding horizontal pressure gradient error.     

Petrography and stable isotope aspects of cold-vent activity imprinted on Miocene-age “calcari aLucina” from Tuscan and Romagna Apennines,Italy

Over 20 occurrences of discontinuous limestone blocks, locally called calcari aLucina, were mapped in the Tuscan—Romagna region of the northern Italian Apennines. The limestones, consisting of a variable mixture of authigenic carbonates (calcite, dolomite, and aragonite), sulfides (primarily pyrite), and allogenic silicates, occur in association with turbidite and hemipelagite units that were deposited in foredeep basins during early to late Miocene times. The limestone blocks are interpreted to represent relicts of carbonate buildups formed around methane-rich fluid vents on the basis of their (1) striking petrographic similarities to carbonates from cold vents in the modern oceans; (2) unique chemosynthetic-like fauna, and (3) anomalously negative ¹³C values ( ¹³C = – 16 to – 58 PDB). The contemporaneous tectonism of the Apennine orogeny is likely to be the primary cause for the expulsion of the methane-rich fluids to the seabed in a manner analogous to the fluid-flow processes occurring at modern accretionary prisms.     

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 .