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41.
Akihiro Shiomoto Katsuyuki Sasaki Toru Shimoda Satsuki Matsumura 《Journal of Oceanography》1994,50(2):209-222
Primary productivity was measured byin situ method using13C in the offshore Oyashio region in the spring (May) and summer (September) of 1990. Most of the values were within the range of 0.1 to 4 gC 1–1 h–1 although a very large value, 7.96 gC l–1 h–1, was observed in summer. Most daily primary production fell within the range of 372 to 633 mgC m–2 d–1 although a very large value, 2,109 mgC m–2 d–1, was observed around the frontal area in summer. Chlorophylla (Chl.a) exceeded 1 g l–1 in many cases, and the maximum was 4.61 g l–1 in spring and 7.53 g l–1 in summer. Most primary productivity per unit Chl.a (photosynthetic assimilation ratio) was within the range of 0.1 to 3 gC gChl.a
–1 h–1 although higher values, 3–6 gC gChl.a
–1 h–1, were observed where small-size phytoplanktons (<2 m) were dominant. These results were compared with results obtained until now in the Oyashio region. The values beyond the range obtained so far in the offshore region were also observed in this study. Furthermore, it was pointed out that the size composition of phytoplankton community has significant influence on the results of Chl.a and photosynthetic assimilation ratio in the Oyashio region. 相似文献
42.
In order to determine quantitatively the reason for the high productivity in the Oyashio Region, which is the southwest part
of the Pacific Subarctic Region, the annual-mean vertical circulation of nitrogen in the region was estimated from the vertical
profiles of nitrate, dissolved oxygen and salinity, and sediment-trap data by adapting them to the balance equations. Estimates
of the upwelling velocity (1.7×10−5cm sec−1) and the vertical diffusivity (2.1 cm2 sec−1) in the abyssal zone and the primary and secondary productivities (44 and 4 mgN m−2day−1, respectively) in the euphotic zone were close to those of previous works. The estimated vertical circulation of nitrogen
strongly suggested that, since the divergence (5 mgN m−2day−1) is caused by the abyssal convergence (6 mgN m−2day−1) and the positive precipitation, the local new production (22 mgN m−2day−1) necessarily exceeds not only the sinking flux (10 mgN m−2day−1) itself but also the sum of the sinking flux and the downward diffusion of dissolved and particulate organic matter (7 mgN
m−2day−1) produced probably in the euphotic zone. The important roles of the abyssal circulation, the winter convection, and the metabolic
activity in the bathyal zone to support the high productivity in the euphotic zone were clarified quantitatively. 相似文献
43.
Katsuyuki Abe 《Physics of the Earth and Planetary Interiors》1981,27(3):194-205
The new scale Mt of tsunami magnitude is a reliable measure of the seismic moment of a tsunamigenic earthquake as well as the overall strength of a tsunami source. This Mt scale was originally defined by Abe (1979) in terms of maximum tsunami amplitudes at large distances from the source. A method is developed whereby it is possible to determine Mt at small distances on the basis of the regional tsunami data obtained at 30 tide stations in Japan. The relation between log H, maximum amplitude (m) and log Δ, a distance of not less than 100 km away from the source (km) is found to be linear, with a slope close to 1.0. Using three tsunamigenic earthquakes with known moment magnitudes Mw, for calibration, the relation, Mt = log H + log Δ + D, is obtained, where D is 5.80 for single-amplitude (crest or trough) data and 5.55 for double-amplitude (crest-to-trough) data. Using a number of tsunami amplitude data, Mt is assigned to 80 tsunamigenic earthquakes that occurred in the northwestern Pacific, mostly in Japan, during the period from 1894 to 1981. The Mt values are found to be essentially equivalent to Mw for 25 events with known Mw. The 1952 Kamchatka earthquake has the largest Mt, 9.0. Of all the 80 events listed, at least seven unusual earthquakes which generated disproportionately-large tsunamis for their surface-wave magnitude Ms are identified from the relation. From the viewpoint of tsunami hazard reduction, the present results provide a quantitative basis for predicting maximum tsunami amplitudes at a particular site. 相似文献
44.
Variability in the Relative Penetration of Ultraviolet Radiation to Photosynthetically Available Radiation in Temperate Coastal Waters, Japan 总被引:1,自引:0,他引:1
Victor S. Kuwahara Tatsuki Toda Koji Hamasaki Tomohiko Kikuchi Satoru Taguchi 《Journal of Oceanography》2000,56(4):399-408
UVR and PAR wavelengths are attenuated to different extents within the water column, causing variations in spectral composition with depth. The present investigation (a) describes the variability of UVR and PAR penetration at a station in the temperate coastal waters of Sagami Bay and determines (b) the characteristics of relative UVR penetration to the euphotic zone. Examination of the seasonal irradiance profile measurements indicated eight measurements displaying two distinct attenuation coefficients (K
d) for specific UVR wavelengths and PAR. The two attenuation coefficients observed from specific wavelengths in the water column may be caused not only by chlorophyll pigments, but also by dissolved organic material in the upper layer. The 1% depth of surface UVR at 305, 320, 340, and 380 nm averaged 10.8 ± 5.7, 14.9 ± 9.5, 19.8 ± 12.1, and 30.4 ± 17.6 m, respectively. The depth of euphotic layer displayed less variability averaging 62 ± 15 m throughout the entire study. Relative UVR penetration within the euphotic zone averaged 17.8 ± 8.1, 22.9 ± 10, 30.5 ± 13.8, and 46 ± 46.9% for 305, 320, 340, and 380 nm, respectively. A large variation of the relative transmission of UVR within the euphotic zone was found although the spectral composition was relatively stable in the air throughout the study. 相似文献
45.
The annual transport of anthropogenic carbon (Canth) to the North Pacific Intermediate Water (NPIW) from the Western Subarctic Gyre (WSG) has been re-estimated by using newly
estimated Oyashio transport and Canth concentration, the latter calculated by the recently-established “ΔC*” method with some modifications. Estimated annual Canth transport through the nearshore Oyashio west of 146°E was 0.020 ± 0.010 GtC y−1, closely approximating the previous estimation based on a 1-D model calibrated with the CFC vertical distribution. The present
study, however, found that an additional 0.025 ± 0.010 GtC y−1 of Canth was transported into NPIW in the region east of 146°E. Total Canth transport, 0.045 GtC y−1, contributes about 35% of annual Canth accumulation of the whole temperate North Pacific.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
46.
Abstract A systematic geochemical study of sandstones from the Cretaceous Shimanto Supergroup and psammitic schists from the Oboke unit in Shikoku has been carried out in order to clarify the depositional age of the protoliths of the Oboke psammitic schists. The geochemical data, together with chronological and geologic data, led to the following conclusions. (i) It is inferred that Oboke psammitic schists are metamorphically equivalent to sandstones in the Hiwasa Formation of the Shimanto accretionary complex, deposited in a trench area during the Campanian, in eastern Shikoku. (ii) The protolith attained to maximum metamorphic conditions within 20 million years after the deposition. (iii) The accumulation of a large amount of coarse-grained clastic sediments in the trench area induced offscraping and underplating of the sediments in the subduction zone, forming the Hiwasa Formation and Oboke unit, respectively. 相似文献
47.
The distribution and dynamics of water molecules and monovalent cations (Li+, Na+, K+, Cs+, and H3O+) on muscovite surfaces were investigated by molecular dynamics (MD) simulations. The direct comparison of calculated X-ray reflectivity profiles and electron density profiles with experiments revealed the precise structure at the aqueous monovalent electrolyte solutions/muscovite interface. To explain the experimentally observed electron density profiles for the CsCl solution-muscovite interface, the co-adsorption of Cs+ and Cl− ion pairs would be necessary. Two types of inner-sphere complexes and one type of outer-sphere complex were observed for hydrated Li+ ions near the muscovite surface. For Na+, K+, Cs+, and H3O+ ions, the inner-sphere complexes were stable on the muscovite surface. The density oscillation of water molecules was observed to approximately 1.5 nm from the muscovite surface. The number of peaks and the locations for the density of water oxygen atoms were almost similar among the water molecules coordinated to Li+, Na+, K+, and H3O+ ions adsorbed on the muscovite surfaces. The water molecules around Cs+ ions that were adsorbed to muscovite surfaces seemed to avoid coordinating with Cs+ ions on the surface, and the density of water oxygen near the muscovite surface decreased relative to that in a bulk state. There was no significant difference in self-diffusion, viscosity, retention time, and reorientation time of water molecules among different cations adsorbed to muscovite surfaces. These translational and rotational motions of water molecules located at less than 1 nm from the muscovite surfaces were slower than those in a bulk state. A significant difference was observed for the exchange times of water molecules around monovalent cations. The exchange time of water molecules was long around Li+ ions and decreased with an increase in the ionic radius. 相似文献
48.
Michinori Honda Shintaro Ohno Atsushi Iizuka Katsuyuki Kawai Hideki Ohta 《Geotechnical and Geological Engineering》2011,29(2):171-180
An evaluation method for the mechanical behavior of unsaturated soils is studied in this paper. Although the mechanical behavior
of unsaturated soils is complicated, a simple modeling is preferable in practice. This is because the soil properties are
not homogeneous and ground data is limited when structures are being designed. In addition, in order to evaluate the reliability
of the design, the physical meanings of the parameters applied in the prediction model should be clear. Firstly, the authors
study the relationship between compaction curves and compression indexes in the unsaturated state that is used in the proposed
constitutive model. Based on the constitutive model, the stress paths for constant volume shear tests are formulated under
a constant void ratio condition and the stress paths for undrained shear tests are calculated under a constant water content
condition. In the case of unsaturated specimens, the volume of these specimens changes with the shear deformation and the
stress paths depend on the initial degree of saturation. The results of the calculation qualitatively describe the test results
by considering the changes in effective confining pressure in the undrained condition and the water retention curves. 相似文献
49.
Farimah Masrouri Kátia V. Bicalho Katsuyuki Kawai 《Geotechnical and Geological Engineering》2008,26(6):691-704
This paper synthesizes the state-of-the art of the various laboratory testing techniques presently available for measuring
the water hydraulic constitutive functions of unsaturated soils. Emphasis is on the laboratory testing techniques for measuring
the soil–water retention curves and the water hydraulic conductivity functions of unsaturated soils. The significant recent
advances in the investigation of the hydraulic behaviour of unsaturated swelling soils, are also presented. Comprehensive
recent references on each measurement method are listed and discussed. 相似文献
50.
Kazuo Abe Norihisa Nakagawa Katsuyuki Abo Mutsumi Tsujino 《Journal of Oceanography》2013,69(2):269-275
Temporary enhancement of the nutrient concentrations in the coastal area was observed after heavy rain in the central Seto Inland Sea in July 2012. After passage of a stationary front accompanied by heavy rain, the river outflow was enhanced, and low salinity and high nutrient concentrations were detected near the mouths of rivers. The offshore salinity and nutrients increased and decreased, respectively, which suggested that a snapshot event, such as heavy rain, could influence the short-term variation of the coastal marine environmental conditions, such as the salinity and nutrient distributions. 相似文献