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1.
Joji Ishizaka Yasuhisa Kitaura Yasuharu Touke Hiroaki Sasaki Akihiko Tanaka Hiroshi Murakami Toshikazu Suzuki Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2006,62(1):37-45
High resolution SeaWiFS data was used to detect red tide events that occurred in the Ariake Sound, Japan, a small embayment
known as one of the most productive areas in Japan. SeaWiFS chlorophyll data clearly showed that a large red tide event, which
damaged seaweed (Nori) cultures, started early in December 2000 in Isahaya Bay, expanded to the whole sound and persisted
to the end of February 2001. The monthly average of SeaWiFS data from May 1998 to December 2001 indicated that the chlorophyll
peaks appeared twice a year, in early summer and in fall, after the peaks of rain and river discharge. The SeaWiFS data showed
that the red tide event during 2000–2001 winter was part of the fall bloom; however, it started later and continued significantly
longer than other years. Satellite ocean color data is useful to detect the red tide; however the algorithms require improvement
to accurately estimate chlorophyll in highly turbid water and in red tide areas. 相似文献
2.
Andrey Andreev Makio Honda Yuichiro Kumamoto Masashi Kusakabe Akihiko Murata 《Journal of Oceanography》2001,57(2):177-188
Excess CO2 and pHexcess showing an increase in dissolved inorganic carbon and a decrease in pH from the beginning of the industrial epoch (middle of the 19th century) until the present time have been calculated in the intermediate water layer of the northwestern Pacific and the Okhotsk Sea. It is concluded that: (1) The Kuril Basin (Okhotsk Sea) and the Bussol' Strait areas are characterized by the greatest concentrations of excess CO2 at isopycnal surfaces due to the processes of formation and transformation of intermediate water mass. (2) The largest difference in excess CO2 concentration between the Okhotsk Sea and the western subarctic Pacific (about 8 µmol/kg) is found at the = 27.0. (3) The difference in excess CO2 between the western subarctic Pacific and subtropical regions is significant only in the upper part of the intermediate water layer ( = 26.7–27.0). (4) About 10% of the excess CO2 accumulation in the subtropical north Pacific is determined by water exchange with the subarctic Pacific and the Okhotsk Sea. 相似文献
3.
Time-series measurements of temperature, salinity, suspended matter and beam attenuation coefficient () were measured at four hour intervals for about two days in June/ July 1982 in the middle shelf region and the coastal region of the southeastern Bering Sea. Current meters were also moored at the same locations.Depth-time distributions of indicated that profiles of suspended matter resulted from a combined process of resuspension of underlying sediments and sinking of suspended particles. Average-values for all measurements for particles revealed that the upward transport of particles due to resuspension formed a boundary layer, with a thickness apparently related to scalar speed. The average-profiles of the particle volume concentration were assumed to result from a balance between the sinking and diffusive flux of particles under a steady state, and the upward fluxes were calculated. Within the boundary layer, values of the upward fluxes of particulate organic matter linearly decreased with the logarithm of distance from the bottom. Fluxes of organic carbon at the upper edge of the boundary layer were 0.375 gC·m–2·day–1 in the middle shelf region (18 m above the bottom, bottom depth=78m) and 0.484gC·m–2·day–1 in the coastal region (25 m above the bottom, bottom depth=33m), and fluxes of nitrogen in both regions were 0.067 gN·m–2·day–1. The flux of organic carbon obtained in the middle shelf region (18 m above the bottom) agreed approximately with the flux (0.416 gC·m–2·day–1) calculated by substituting primary production data into the empirical equation of Suess (1980). 相似文献
4.
Masayuki Takahashi Isao Koike Takashi Ishimaru Toshiro Saino Ken Furuya Yoshihiko Fujita Akihiko Hattori Shun-ei Ichimura 《Journal of Oceanography》1980,36(4):209-216
Water plumes, 20 km long or less, identified by low temperature, high salinity and high nutrient concentrations, were observed on the eastern side of Izu Islands where the Kuroshio Current or its branch flowed eastward. The T-S diagrams and the vertical profiles of oceanographic variables indicated that the water plumes resulted from the upwelling of subsurface water. A newly formed plume, characterized by a sharp temperature front and high nutrient concentrations, contained less chlorophyll than did old plumes. It is suggested that the upwelling plumes are maintained for a period long enough to allow luxuriant growth of phytoplankton. 相似文献
5.
Annibale Mottana Takatoshi Murata Ziyu Wu Augusto Marcelli Eleonora Paris 《Physics and Chemistry of Minerals》1997,24(7):500-509
X-ray absorption Na K-edge spectra have been recorded on synthetic endmember jadeite and on a series of natural Ca-Na pyroxenes
compositionally straddling the Jd-Di join. The C2/c members of the series are systematically different from the P2/n members. Differences can be interpreted and explained by comparing the experimental spectra with theoretical spectra. These
have been calculated by the multiple-scattering formalism from the atomic positional parameters determined by single-crystal
X-ray diffraction structure refinement on the same samples. In the full multiple scattering region of the spectra (1075 to
1090 eV) C-pyroxenes exhibit three features which reflect the 6-2 configuration of the O back-scattering atoms around the Na absorber
located at the center of the cluster (site M2 of the jadeite structure). P-pyroxenes show more complicated spectra in which at least four (possibly five) features can be recognized; they reflect the
two types of configuration (6-2 and 4-2-2) of O around Na in the two independent M2 and M21 eight-fold coordinated sites of the omphacite structure. A weak, sometimes poorly resolved peak at 1079 eV is diagnostic
and discriminates C- from P-pyroxenes. The Garnet Ridge C2/c impure jadeite exhibits a spectrum which is intermediate between those of jadeite and omphacite. The Hedin-Lundqvist potential
proves best for these insulating materials and allows multiple-scattering calculations agreeing well with experiments.
Received: July 11, 1996/Revised, accepted: October 21, 1996 相似文献
6.
7.
Anwar Qadir Zulfiqar Ahmad Tahseenullah Khan Mohammad Zafar Atwar Qadir Mamoru Murata 《Arabian Journal of Geosciences》2016,9(2):149
Dera Ismail Khan (DIK) is situated in the Lower Indus Basin of Pakistan. The land use has been changed in the canal command area due to irrigation activities near the Indus River. To check the current status and predict the groundwater levels in the area, the unconfined aquifer has been simulated in Visual MODFLOW for a period of 35 years, i.e., from 1985 to 2020. The 2900-km2 area has been modeled with a grid of 500 by 500 m and the depth set to 100 m. The aquifer in the study area has been divided vertically and laterally into three and ten zones, respectively, for the characterization. Water wells and streams were used as the sinks and hydrologic boundaries, respectively. The model was successfully calibrated in steady and the non-steady state. The simulation revealed that the whole simulation can be divided into two phases, i.e., before and after the construction of the Chashma Right Bank Canal (CRBC), whereas the results were summarized in the form of water table depth maps and groundwater budget calculations. To determine the groundwater sustainability, a conjunctive use scenario has been employed to simulate the aquifer dynamics till 2020. The simulation revealed incremental drawdowns till the end. 相似文献
8.
Reza Deevsalar Ryuichi Shinjo Jean P. Liégeois Mohammad V. Valizadeh Jamshid Ahmadian Hadi Yeganehfar Mamoru Murata Iain Neill 《Swiss Journal of Geoscience》2018,111(1-2):269-293
The Malayer–Boroujerd plutonic complex (MBPC) in western Iran, consists of a portion of a magmatic arc built by the northeast verging subduction of the Neo-Tethys plate beneath the Central Iranian Microcontinent (CIMC). Middle Jurassic-aged felsic magmatic activity in MBPC is manifested by I-type and S-type granites. The mafic rocks include gabbroic intrusions and dykes and intermediate rocks are dioritic dykes and minor intrusions, as well as mafic microgranular enclaves (MMEs). MBPC Jurassic-aged rocks exhibit arc-like geochemical signatures, as they are LILE- and LREE-enriched and HFSE- and HREE-depleted and display negative Nb–Ta anomalies. The gabbro dykes and intrusions originated from metasomatically enriched garnet-spinel lherzolite [Degree of melting (fmel) ~ 15%] and exhibit negative Nd and positive to slightly negative εHf(T) (+ 3.0 to ? 1.6). The data reveal that evolution of Middle Jurassic magmatism occurred in two stages: (1) deep mantle-crust interplay zone and (2) the shallow level upper crustal magma chamber. The geochemical and isotopic data, as well as trace element modeling, indicate the parent magma for the MBPC S-type granites are products of upper crustal greywacke (fmel: 0.2), while I-type granites formed by partial melting of amphibolitic lower crust (fmel: 0.25) and mixing with upper crustal greywacke melt in a shallow level magma chamber [Degree of mixing (fmix): 0.3]. Mixing between andesitic melt leaving behind a refractory dense cumulates during partial crystallization of mantle-derived magma and lower crustal partial melt most likely produced MMEs (fmix: 0.2). However, enriched and moderately variable εNd(T) (? 3.21 to ? 4.33) and high (87Sr/86Sr)i (0.7085–0.7092) in dioritic intrusions indicate that these magmas are likely experienced assimilation of upper crustal materials. The interpretations of magmatic activity in the MBPC is consistent with the role considered for mantle-derived magma as heat and mass supplier for initiation and evolution of magmatism in continental arc setting, elsewhere. 相似文献
9.
Hiroaki Sasaki Akihiko Tanaka Mitsunori Iwataki Yasuharu Touke Eko Siswanto Chun Knee Tan Joji Ishizaka 《Journal of Oceanography》2008,64(4):511-523
Remote sensing reflectance [R
rs(λ)] and absorption coefficients of red tides were measured in Isahaya Bay, southwestern Japan, to investigate differences in
the optical properties of red tide and non-red tide waters. We defined colored areas of the sea surface, visualized from shipboard,
as “red tides”. Peaks of the R
rs(λ) spectra of non-red tide waters were at 565 nm, while those of red tides shifted to longer wavelengths (589 nm). The spectral
shape of R
rs(λ) was close to that of the reciprocal of the total absorption coefficient [1/a(λ)], implying that the R
rs(λ) peak is determined by absorption. Absorption coefficients of phytoplankton [a
ph(λ)], non-pigment particles and colored dissolved organic matter increased with increasing chlorophyll a concentration (Chl a), and those coefficients were correlated with Chl a for both red tide and non-red tide waters. Using these relationships between absorption coefficients and Chl a, variation in the spectrum of 1/a(λ) as a function of Chl a was calculated. The peak of 1/a(λ) shifted to longer wavelengths with increasing Chl a. Furthermore, the relative contribution of a
ph(λ) to the total absorption in red tide water was significantly higher than in non-red tide water in the wavelength range 550–600
nm, including the peak. Our results show that the variation of a
ph(λ) with Chl a dominates the behavior of the R
rs(λ) peak, and utilization of R
rs(λ) peaks at 589 and 565 nm may be useful to discriminate between red tide and non-red tide waters by remote sensing. 相似文献
10.
Seasonal variation of horizontal material transport through the eastern channel of the Tsushima Straits 总被引:2,自引:2,他引:0
Akihiko Morimoto Tetsutaro Takikawa Goh Onitsuka Atsushi Watanabe Masatoshi Moku Tetsuo Yanagi 《Journal of Oceanography》2009,65(1):61-71
We conducted hydrographic observations ten times in the Tsushima Strait to reveal seasonal variations of horizontal material
transports such as of heat, freshwater, chlorophyll a, and dissolved inorganic nitrogen (DIN) and phosphorus (DIP) through the eastern channel of the Tsushima Strait (ECTS). The
volume, freshwater, and heat transport results are of nearly the same order as results reported in previous studies. The annual
mean DIN and DIP transports of 3.59 kmol/s and 0.29 kmol/s are large relative to those of the Changjiang and the Taiwan Strait
and are horizontally transported through the ECTS. Nutrient transports are high in July–August and October and low in April
and November. Increased nutrient transports in July–August and October are due to the appearance of a cold saline water mass
in the bottom layer of the ECTS. Changes in DIN transports in summer and autumn, which account for two-thirds of the total
annual DIN transport, would have a large effect on the nitrogen budget and biological productivity in the Tsushima Warm Current
region. 相似文献