Chlorofluorocarbons in the western North Pacific in 1993 and formation of North Pacific intermediate water     

Takayuki Tokieda  Shuichi Watanabe  Shizuo Tsunogai 《Journal of Oceanography》1996,52(4):475-490

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   

Cycles of chemical substances in the atmosphere,the Sea and the sea-floor     

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   

CFC Indicating Renewal of the Japan Sea Deep Water in Winter 2000–2001     

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   

Methane in Izena Cauldron,Okinawa Trough     

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   

Spatial and Temporal Variation of Surface xCO<Subscript>2</Subscript> Providing Net Biological Productivities in the Western North Pacific in June     

Koto?SugiuraEmail author  Shizuo?Tsunogai 《Journal of Oceanography》2005,61(3):435-445

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   

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  

Yang  Gui-Peng  Tsunogai  Shizuo  Watanabe  Shuichi 《Journal of Oceanography》2005,61(1):69-78

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 (DMSP_d) and particulate (DMSP_p), 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 DMSP_d in the surface microlayer ranged from 0.81 to 4.6 with a mean of 1.85. In contrast, EF of DMSP_p 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 DMSP_p in the surface microlayer showed a strong temporal variation, basically following the change in chlorophyll a levels. Moreover, the microlayer concentrations of DMSP_p were, on average, 3-fold higher than the microlayer concentrations of DMSP_d and there was a significant correlation between them. Additionally, there was a great variability in the ratios of DMSP_p 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 DMSP_d 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   

Origins of hydrocarbons in the Sagara oil field, central Japan     

Tomohiro  Toki  Toshitaka  Gamo  Urumu  Tsunogai 《Island Arc》2006,15(3):285-291

Abstract   We collected free-gas and in situ fluid samples up to a depth of 200.6 m from the Sagara oil field, central Japan (34°44'N, 138°15'E), during the Sagara Drilling Program (SDP) and measured the concentrations and stable carbon isotopic compositions of CH₄ and C₂H₆ in the samples. A combination of the CH₄/C₂H₆ ratios with the carbon isotope ratios of methane indicates that the hydrocarbon gases are predominantly of thermogenic origin at all depths. The isotope signature of hydrocarbon gases of δ¹³      < δ¹³     suggests that these gases in the Sagara oil field are not generated by polymerization, but by the decomposition of organic materials.  相似文献   

Chemical Assessment of Oceanic and Terrestrial Sulfur in the Marine Boundary Layer over the Northern North Pacific during Summer   总被引：2，自引：0，他引：2  

K. Aranami  S. Watanabe  S. Tsunogai  A. Ohki  K. Miura  H. Kojima 《Journal of Atmospheric Chemistry》2002,41(1):49-66

Dimethylsulfide (DMS) in surface seawater and the air, methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO₄ ²–) in aerosol, and radon-222 (Rn-222) were measured in the northern North Pacific, including the Bering Sea, during summer (13 July – 6 September 1997). The mean atmospheric DMS concentrations in the eastern region (21.0 ± 5.8 nmole/m³ (mean ± S.D.), n=30) and Bering Sea (19.9 ± 9.8 nmole/m³, n=10) were higher than that in the western region (11.1 ± 6.4 nmole/m³, n=31) (p<0.05), although these regions did not significantly differ in the mean DMS concentration in surface seawater. Mean sea-to-air DMS flux in the eastern region (21.0 ± 10.4 mole/m²/day, n=19) was larger than those in the western region (11.3 ± 16.9 mole /m²/day, n=22) and Bering Sea (11.2 ± 7.8 mole/m²/day, n=7) (p<0.05). This suggests that the longitudinal difference in atmospheric DMS was produced by that in DMS flux owing to wind speed, while the possible causes of the higher DMS concentrations in the Bering Sea include (1) later DMS oxidation rates, (2) lower heights of the marine boundary layer, and (3) more inactive convection. The mean MSA concentrations in the eastern region (1.18 ± 0.84 nmole/m³, n=35) and Bering Sea (1.17 ± 0.87 nmole/m³, n=13) were higher than that in the western region (0.49 ± 0.25 nmole/m³, n=28) (p < 0.05). Thus the distribution of MSA was similar to that of DMS, while the nss-SO₄ ²– concentrations were higher near the continent. This suggests that nss-SO₄ ²– concentrations were regionally influenced by anthropogenic sulfur input, because the distribution of nss-SO₄ ²– was similar to that of Rn-222 used as a tracer of continental air masses.  相似文献   

Recycling of manganese in the coastal sea,Funka Bay,Japan     

Mitsuo Uematsu  Shizuo Tsunogai 《Marine Chemistry》1983,13(1):1-14

The downward flux of Mn through the water column was directly measured using sediment traps. The Mn flux from the bottom sediment to the water column, and the removal rate of Mn in the bottom water were estimated from Mn gradients in the bottom water. The sediment traps were deployed more than ten times at the same station in Funka Bay, Japan. The trapped settling matter and filtered suspended matter samples were analyzed for Mn, Fe, Al and ignition loss. The observed downward flux of Mn through the water column in winter (1.3–2.8 μg/cm² /day) was generally an order of magnitude larger than that in summer (0.13–0.45 μg/cm² /day), and the Mn fluxes for both seasons were also greater than the accumulation rate of Mn in the bottom sediments (0.10 μg/cm ²/day). More Al was contained in the trapped settling matter than in the suspended matter, while Mn showed the opposite behavior. The Fe/Mn ratio of the residual fraction (obtained by subtracting the sediment component of the settling matter) was rather well correlated with the corresponding ratio in suspended matter. Settling particles are expected to scavenge suspended matter during their passage through the water column. The flux of Mn across the sediment—water interface was estimated from its vertical profiles in the water column to be 0.1–0.3 μg/cm² day. The residence time of Mn in bottom water was about one to several months. These results suggest that Mn is actively recycled between the water column and the sediments of the coastal sea.  相似文献   

Methane in the western North Pacific   总被引：7，自引：0，他引：7  

Shuich Watanabe  Naoto Higashitani  Nobuo Tsurushima  Shizuo Tsunogai 《Journal of Oceanography》1995,51(1):39-60

The concentration of methane in about 400 seawater samples collected in the western North Pacific, mostly from 40°N to 5°S along 165°E was determined. While the concentration of methane in the surface water was slightly greater in the high-latitudes, it did not widely vary with a standard deviation of 0.29 n mol/l for a mean value of 2.49 n mol/l. The 90% confidence limit of the mean was 0.08 n mol/l. The degree of oversaturation in 1991 (31±4%) was not different from that in circa 1970. If we assume that this degree of oversaturation occurs in the entire oceans, the annual flux of methane becomes 6×10¹²g CH₄. Both the concentrations of methane and chlorophylla were higher in the surface 100 m layer. However, the correlation between them was not well in the entire surface waters. This may indicate that the production of methane is not directly related to the photosynthetic process. The concentration of methane decreased gradually with increasing depth down to 1000 m. Its horizontally and vertically uniform concentration in the abyssal water suggests that the turnover time of methane in the oxic pelagic water is in the range between a few years and a few hundred years.  相似文献