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51.
Vertical profiles of210Pb and230Th in the deep water were analyzed by using a simple one-dimensional model. Both nuclides are considered to settle down with the velocity of 1×10–4 cm/sec. The diameter of particle corresponding to the velocity is calculated to be 5, while only about 10 % of the nuclides can be collected on filter paper with a pore size of 0.5. It is supposed that the nuclides exist in particulate materials which is changeable in size. This suggestion is supported from the following evidences. (1) The directly observed behavior of marine snow and the size distribution of particles observed with a coulter counter. (2) The existence of many chemical elements of which residence time is about 150 years. (3) Their possible existence as eutectic solid phases in the seawater. (4) The consistency of the observed accumulation rate of pelagic sediments with that estimated from the settling velocity. (5) The consistency of the decomposition rate of organic matter in the deep water estimated from the oxygen comsumption with that from the settling velocity. 相似文献
52.
Chlorofluorocarbons (CFC-11 and CFC-12) in the intermediate water having between 26.4 and 27.2 were determined at 75 stations in the western North Pacific north of 20°N and west of 175.5°E in 1993. The intermediate water of 26.4–26.6 was almost saturated with respect to the present atmospheric CFC-11 in the zone between 35 and 45°N around the subarctic front. Furthermore, the ratios of CFC-11/CFC-12 of the water were also of those formed after 1975. These suggest that the upper intermediate water (26.4–26.6) was recently formed by cooling and sinking of the surface water not by mixing with old waters. The water below the isopycnal surface of 26.8 contained less CFCs and the area containing higher CFCs around the subarctic front was greatly reduced. However, the CFC age of the lower intermediate water (26.8–27.2) in the zone around the subarctic front was not old, suggesting that the water was formed by diapycnal mixing of the water ventilated with the atmosphere with old waters not containing appreciable CFCs, probably the Pacific Deep Water. The southward spreading rate decreased with depth and it was one sixth of its eastward spreading rate of the North Pacific Intermediate Water (NPIW). 相似文献
53.
Shizuo Tsunogai 《Journal of Oceanography》1984,40(4):314-322
Since 1960 when I was a senior student, I have studied natural phenomena observed in the hydrosphere and atmosphere by means
of chemical elements. Each of the phenomena is, in general, very complicated and so I have attempted to depict the whole picture
of material circulation in the marine environment by studying its various aspects at the same time. My chief strategy has
been to use natural radio-nuclides as clocks of various phenomena, and to use sediment traps for the determination of vertical
fluxes in the ocean. The many results I have obtained can be summarized as follows.
1. I have found that several sporadic events control the material exchange through the atmosphere. These include the strong
winter monsoon and typhoons that transport sea-salt particles to the Japanese Islands, theKosa episodes that transport soil dust to the ocean, and storms that result in exchange of sparingly soluble gases such as oxygen
and carbon dioxide at the air-sea interface. I have also proved quantitatively that the source of aluminosilicate material
in pelagic sediments is air-borne dust.
2. I have proposed a model,Settling model, for the removal of chemical substances from the ocean and found various lines of evidence supporting the model. This model
predicts the reversibility in the existing state of insoluble chemical elements in seawater among large settling particles,
small suspended particles and colloidal particles that pass through a membrane filter and explains well their behavior in
the ocean. I have first precisely measured calcium and iodine in the ocean and have explained their distributions on the basis
of the solution and redox equilibria.
3. Using chemical tracers, I have estimated the vertical eddy diffusion coefficients to be 1.2 cm2sec−1 for the Pacific deep water, 0.5 cm2sec−1 for the deep Bering Sea water and 3–80 cm2sec−1 for the Pacific surface water, and have studied the structure of water masses in the western North Pacific and the Sea of
Japan. I have also invented and applied a method for the calculation of the age of deep waters using radiocarbon.
4. I have calculated the rates of decomposition of organic matter and the regeneration rates of chemical components in the
deep and bottom waters as well as coastal waters by modelling water circulation and mixing. Particulate fluxes and regeneration
rates are larger in the deep waters beneath the more biologically productive surface waters. I have stressed the role of silicate
in the marine ecosystem, especially in the succession of phytoplankton species.
5. I have quantitatively studied the migration of chemical elements during the early diagenesis of bottom sediments especially
manganese using chemical and radiochemical techniques. Manganese is being actively recycled not only in coastal seas but also
in pelagic sediments except in the highly oligotrophic subtropical ocean. This recycling can explain the formation of manganese
nodules and enables us to balance the manganese budget in the ocean. 相似文献
54.
Shizuo Tsunogai Kentaro Kawada Shuichi Watanabe Takafumi Aramaki 《Journal of Oceanography》2003,59(5):685-693
The distributions of CFC (chlorofluorocarbon) in the water column was determined twice in 2000 and 2001 in the northwestern
Japan Sea. In 2000 the CFC-11 concentration decreased almost exponentially with depth from 6 pmol/kg at a few hundred m deep
to 0.3 pmol/kg or less at the bottom of about 3400 m depth at three stations (40–41°N, 132–133°E) about 300 km off Vladivostok.
In 2001 the CFC-11 concentration increased sharply up to 2 pmol/kg in the bottom water, while it did not increase at a station
(42.0°N, 136.5°E) about 450 km away to the northeast. This is due to the renewal of the bottom water which is replaced by
the surface water flowing down along the continental slope, as suggested by Tsunogai et al. (1999), who proposed the continental shelf pump. Furthermore, an increase in the CFC-11 concentration was observed throughout
the entire water column above 3000 m depth, although the proportion of the increase was about 20%, which was one order of
magnitude smaller than that in the bottom water. The increase in inventory is almost four times larger than that in the bottom
water below 3000 m depth which is equivalent to about 1/6 of the total inventory found in 2000. The increase also means that
3% of the deep water was replaced by the recent surface water, or, if the turnover occurs every year, that the turnover time
of the deep water to be about 30 years.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
55.
Shuichi Watanabe Nobuo Tsurushima Masashi Kusakabe Shizuo Tsunogai 《Journal of Oceanography》1995,51(2):239-255
Methane in the deep water of Izena Cauldron (maximum depth: ca. 1650 m) at the east side of mid-Okinawa Trough was studied by casting a CTD system with 12 Niskin bottles for water sampling at 11 stations inside and outside the cauldron. The water contained much methane up to 706 nmoles/l. The depths of maximum concentration varied widely from station to station, indicating the existence of a considerable number of vents emitting methane and heat. The waters containing less methane formed a straight line in theT-S diagram, while those containing more methane were more largely deviated from the line. The temperature anomaly was virtually proportional to the methane concentration, suggesting that the oxidation rate of methane inside the cauldron is negligibly small and methane can be used as a tracer of the cauldron water. The relation and the estimated vertical diffusivity gave the following fluxes. The emissions of methane and heat out of the bottom below 1450 m turn out to be 1400 moles/day and 7×1010 cal/day, respectively. The total emission rates inside the cauldron are presumed to be about twice the above values. The turnover time of methane has been estimated to be 240 days, which is also that of heat generated from the bottom and probably that of the bottom water. 相似文献
56.
More than 14,000 measurements of surface water xCO2 were obtained during two cruises, 3 weeks apart in June 2000, along 155°E between 34 and 44°N in the western North Pacific Ocean. Based on the distributions of salinity and sea surface temperature (SST), the region has been divided into 6 subregions; Oyashio, Oyashio front, Transition, Kuroshio front, and Kuroshio extension I and II zones, from north to south. The surface waters were always undersaturated with respect to atmospheric CO2. The Oyashio water was the least undersaturated: its xCO2 decreased slightly by 7 ppm, while SST increased by 2°C. The xCO2 normalized to a constant temperature decreased considerably. In the two frontal zones, a large drawdown of 30–40 ppm was observed after 18–19 days. In the Kuroshio extension zones, the xCO2 increased, but the normalized xCO2 decreased considerably. The Transition zone water may be somewhat affected by mixing with the subsurface water, as indicated by the smallest SST rise, an undecreased PO4 concentration, and a colder and less stable surface layer than the Oyashio front water. As the uncertainty derived from the air-sea CO2 flux was not large, the xCO2 data allowed us to calculate the net biological productivity. The productivities around 60 mmol C m−2d−1 outside the Transition zone indicate that the northwestern North Pacific, especially the two frontal zones, can be regarded as one of the most productive oceans in the world. 相似文献
57.
Biogeochemistry of Dimethylsulfoniopropionate (DMSP) in the Surface Microlayer and Subsurface Seawater of Funka Bay,Japan 总被引:1,自引:0,他引:1
Twenty-eight sea surface microlayer samples, along with subsurface bulk water samples were collected in Funka Bay, Japan during October 2000–March 2001 and analyzed for dimethylsulfoniopropionate, dissolved (DMSPd) and particulate (DMSPp), and chlorophyll a. The aim of the study was to examine the extent of enrichment of DMSP in the microlayer and its relationship to chlorophyll a, as well as the production rate of dimethylsulfide (DMS) from DMSP and the factors that influence this. The enrichment factor (EF) of DMSPd in the surface microlayer ranged from 0.81 to 4.6 with a mean of 1.85. In contrast, EF of DMSPp in the microlayer varied widely from 0.85–10.5 with an average of 3.21. Chlorophyll a also appeared to be enriched in the microlayer relative to the subsurface water. This may be seen as an important cause of the observed enrichment of DMSP in the microlayer. The concentrations of DMSPp in the surface microlayer showed a strong temporal variation, basically following the change in chlorophyll a levels. Moreover, the microlayer concentrations of DMSPp were, on average, 3-fold higher than the microlayer concentrations of DMSPd and there was a significant correlation between them. Additionally, there was a great variability in the ratios of DMSPp to chlorophyll a over the study period, reflecting seasonal variation in the proportion of DMSP producers in the total phytoplankton assemblage. It is interesting that the production rate of DMS was enhanced in the microlayer and this rate was closely correlated with the microlayer DMSPd concentration. Microlayer enrichment of chlorophyll a and higher DMS production rate in the microlayer provide favorable evidence supporting the view that the sea surface microlayer has a greater biological activity than the underlying water. 相似文献
58.
Sand banks around straits are used as a commercial fishing ground. In order to clarify the mechanism of sand bank formation, the Lagrangian method was used to measure currents and turbidity around the banks in the Neko Seto Sea in the Seto Inland Sea of Japan. A neutrally buoyant float released in the Neko Seto Strait at the maximum tidal flow stage was engulfed in a pair of tidal vortices and moved around one of the sand banks. The vertical distribution of turbidity, which was measured by the vessel moving with the neutral float, showed an extremely high turbidity in the bottom layer of this bank area. According to the analysis of these observational data, the process of sand bank formation around straits is as follows. The tidal vortex transports water mass with suspended materials (including sand) which are whirled up at the bottom by the tidal jet. In the decaying stage of the vortex, the materials in the bottom layer are gathered in the central part of the vortex by the secondary convergent flow in the vortex. Among these materials, a large-size sand particle with a high critical erosion velocity accumulates at the bottom and forms banks. The distribution of bottom sediment and the thickness of alluvium support this result. 相似文献
59.
60.
Boonyatumanond R Wattayakorn G Amano A Inouchi Y Takada H 《Marine pollution bulletin》2007,54(5):554-565
This paper reports the first reconstruction of a pollution history in tropical Asia from sediment cores. Four sediment core samples were collected from an offshore transect in the upper Gulf of Thailand and were analyzed for organic micropollutants. The cores were dated by measurement of (137)Cs and geochronometric molecular markers (linear alkylbenzenes, LABs; and tetrapropylene-type alkylbenzenes, TABs). Polychlorinated biphenyl (PCB) concentrations showed a subsurface maximum in layers corresponding to the 1970s, indicating the effectiveness of regulation of PCBs in Thailand. LAB concentrations increased over time, indicating the increase in input of sewage into the Gulf during the last 30 years. Hopanes, biomarkers of petroleum pollution, also increased over time, indicating that the inputs of automobile-derived hydrocarbons to the coastal zone has been increasing owing to the increased number of cars in Thailand since the 1950s. Polycyclic aromatic hydrocarbons (PAHs) increased in the layers corresponding to the 1950s and 1960s, probably because of the increased inputs of automobile-derived PAHs. PAH concentrations in the upper layers corresponding to the 1970s and later remained constant or increased. The absence of a subsurface maximum of PAHs contrasts with results observed in industrialized countries. This can be explained by the facts that the Thai economy did not depend on coal as an energy source in the 1960s and that economic growth has continued since the 1970s to the present. The deposition flux of PAHs and hopanes showed a dramatic offshore decrease, whereas that of LABs was uniform. 相似文献