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1.
Makoto Yamada Shinji Ohsawa Kohei Kazahaya Masaya Yasuhara Hiroshi Takahashi Kazuhiro Amita Hideo Mawatari Shin Yoshikawa 《Journal of Geochemical Exploration》2011
To understand deep groundwater flow systems and their interaction with CO2 emanated from magma at depth in a volcanic edifice, deep groundwater samples were collected from hot spring wells in the Aso volcanic area for hydrogen, oxygen and carbon isotope analyses and measurements of the stable carbon isotope ratios and concentrations of dissolved inorganic carbon (DIC). Relations between the stable carbon isotope ratio (δ13CDIC) and DIC concentrations of the sampled waters show that magma-derived CO2 mixed into the deep groundwater. Furthermore, groundwaters of deeper areas, except samples from fumarolic areas, show higher δ13CDIC values. The waters' stable hydrogen and oxygen isotope ratios (δD and δ18O) reflect the meteoric-water origin of that region's deep groundwater. A negative correlation was found between the altitude of the well bottom and the altitude of groundwater recharge as calculated using the equation of the recharge-water line and δD value. This applies especially in the Aso-dani area, where deeper groundwater correlates with higher recharge. Groundwater recharged at high altitude has higher δ13CDIC of than groundwater recharged at low altitude, strongly suggesting that magmatic CO2 is present to a much greater degree in deeper groundwater. These results indicate that magmatic CO2 mixes into deeper groundwater flowing nearer the magma conduit or chamber. 相似文献
2.
Satoshi?KitajimaEmail author Naoki?Iguchi Naoto?Honda Tatsuro?Watanabe Osamu?Katoh 《Journal of Oceanography》2015,71(3):287-296
We investigated the horizontal distribution of Nemopilema nomurai medusae using a midwater trawl in the southwestern Sea of Japan from September to October of each year from 2006 to 2012. Numerous medusae of this species found in 2006, 2007, and 2009 were mainly distributed far (>40 km) from the mainland of Japan in the western part of the survey area, but were distributed in the stations closest (<25 km) to the mainland in the eastern part, particularly in 2006 and 2009. These distribution patterns were associated with the path of the second branch of the Tsushima Warm Current (TWC) that flows offshore to the west of Oki Islands and usually approaches the mainland of Japan to the east of Oki Islands. Differences in jellyfish distribution across the survey periods were related to the distribution of the second branch being associated with types, position and intensity of eddies in the eastern part of the survey area. Hence, the formations of eddies and consequent variation in the path of the TWC would be responsible for transporting medusae from offshore to near the mainland to the east of Oki Islands. Individuals with large bells accumulated in the northwestern part of the survey area, where a cyclonic eddy was present downstream of the third branch of the TWC. This variation in bell size distribution may be ascribed to differences in the physical and/or biological factors among the three branches of the TWC. 相似文献
3.
Osamu Katoh Kenji Morinaga Kuniaki Miyaji Kazuyuki Teshima 《Journal of Oceanography》1996,52(6):747-761
We discussed the branching and joining of the Tsushima Current around the Oki Islands, based on ADCP and CTD measurements carried out in June 1990 by the quadrireciprocal method (Katoh, 1988). The volume transport of the northeastward current northwest of the Izumo Coast was about 2 Sv. The triple-branch structure of the Tsushima Current was obscure there. This northeastward current divided into the eastward and northward currents, with volume transports of 0.5 Sv and 1.5 Sv, respectively, at the west entrance of the Oki Strait. Most of the first branch of the Tsushima Current seemed to be separated again from the other confluent branches and to pass through the Oki Strait as this eastward current. The northward current was composed of the second and the third branches of the Tsushima Current. It detoured the Oki Islands, and almost all of it returned south to the Tajima Coast. In the vicinity of the Tajima Coast, the eastward current was abruptly strengthened through the confluence of the southward one which was originated from the northward current west of the Oki Islands. This showed that the first branch finally joined the compound of the second and the third branches detouring the Oki Islands. Between the Oki Strait and the Tajima Coast, the two-layer structure of currents was clearly found. 相似文献
4.
Masaya Toyokawa Kaoru Aoki Satoshi Yamada Akira Yasuda Yusuke Murata Tomohiko Kikuchi 《Journal of Oceanography》2011,67(2):209-218
We surveyed the distribution of colonies of polyps of Aurelia
aurita sensu lato (s.l.) in Mikawa Bay, Japan. First, we surveyed the distribution of ephyrae of A. aurita s.l. at 75 stations encompassing the whole of Mikawa Bay in early 2008. A total of 37 ephyrae were sampled mostly from fishing
ports. Ephyrae were most abundant around the islands located near the mouth of the bay, and decreased from the western part
to the eastern part of Mikawa Bay. Next, we selected five fishing ports in Mikawa Bay where ephyrae occurred and surveyed
the underside of floating piers and underwater overhangs of wharfs. We found dense colonies of polyps of A. aurita s.l. under nearly all of the floating piers at the two islands located near the mouth of the bay. Fitting a logistic regression
model to the dataset showed that the percentage coverage of Aurelia polyps was significantly greater at the two islands compared with the other locations. In addition, the coverage of Aurelia polyps was greater when the coverage of other fouling organisms was in the range of 65–90%, and the coverage of Aurelia polyps was lower on floating piers with a vinyl surface and on concrete wharfs. The combined distribution of polyp colonies
of A. aurita s.l. in Ise Bay and Mikawa Bay suggested that A. aurita s.l. in the two bays probably forms a single population and shoals of medusae mainly originate from protected harbors along the
mouth-part of the bays. 相似文献
5.
Victor Vladimirovich Orlov Anna V. Petrova Kiyotaka Tanikawa Masaya M. Saito Alija I. Martynova 《Celestial Mechanics and Dynamical Astronomy》2008,100(2):93-120
The rectilinear equal-mass and unequal-mass three-body problems are considered. The first part of the paper is a review that
covers the following items: regularization of the equations of motion, integrable cases, triple collisions and their vicinities,
escapes, periodic orbits and their stability, chaos and regularity of motions. The second part contains the results of our
numerical simulations in this problem. A classification of orbits in correspondence with the following evolution scenarios
is suggested: ejections, escapes, conditional escapes (long ejections), periodic orbits, quasi-stable long-lived systems in
the vicinity of stable periodic orbits, and triple collisions. Homothetic solutions ending by triple collisions and their
dependence on initial parameters are found. We study how the ejection length changes in response to the variation of the triple
approach parameters. Regions of initial conditions are outlined in which escapes occur after a definite number of triple approaches
or a definite time. In the vicinity of a stable Schubart periodic orbit, we reveal a region of initial parameters that corresponds
to trajectories with finite motions. The regular and chaotic structure of the manifold of orbits is mostly defined by this
periodic orbit. We have studied the phase space structure via Poincaré sections. Using these sections and symbolic dynamics,
we study the fine structure of the region of initial conditions, in particular the chaotic scattering region. 相似文献
6.
Ikuko Kitaba Masayuki Hyodo Shigehiro Katoh Mariko Matsushita 《Gondwana Research》2012,21(2-3):595-600
The influence of the geomagnetic field on climate, a long hotly disputed issue, was examined for the Matuyama–Brunhes (MB) magnetic polarity transition using palynological and paleomagnetic data sets from a high accumulation rate (ca. 50 cm/kyr) sediment core from Osaka Bay. During the period from marine oxygen isotope stages (MIS) 20 to 18, climate change is well correlated with global ice volume variation in the precession cycle, with the exception of the early half of MIS 19. The postglacial warming after substage 20.2 was interrupted by cooling that began just before the sea-level highstand correlated with substage 19.3 and persisted until about a mid-point between 19.3 and 19.2, followed by a rapid warming. The thermal maximum clearly postdates the highest sea-level highstand by 6–7 kyr, and the connection between orbital forcing and climate was disrupted. The cooling event coincided with the center of the paleointensity low during the MB transition. This unusual climate cooling across a sea-level peak is very likely related to the field intensity decrease. The data from Osaka Bay may suggest an instance where the geomagnetic field has influenced climate in the past. 相似文献
7.
Short-term fluctuations of the Tsushima Current in waters northwest of Yamaguchi Prefecture 总被引：1，自引：0，他引：1
Osamu Katoh 《Journal of Oceanography》1994,50(1):51-64
We discussed the short-term fluctuations of the Tsushima Current, using ADCP (acoustic Doppler current profiler) data taken by the quadrireciprocal method (Katoh, 1988) for removing tidal currents from observed currents. Transects were set in waters northwest of Yamaguchi Prefecture to capture the first and second branches of the Tsushima Current. Along the transects, ADCP and STD (salinitytemperature-depth recorder) measurements were repeated in May to July 1989. The velocity of the first branch fluctuated considerably in a short period, while the direction and position of its axis were steadly. The stability of its axis position probably results from the topographic effect. The baroclinic transport, which is based on calculations of geostrophic current with assuming zero velocity near the bottom, of the first branch was almost equal to the barotropic one. The range of fluctuation in the barotropic transport was much larger than that in the baroclinic transport. The barotropic fluctuation was correlated with the difference in atmospheric pressure between the east and west sides of the Tsushima Strait. As for the second branch, not only the velocity but also the position of its axis changed noticeably in a short period. There was such a case where the axis was hardly recognized. The changeability of the axis position for the second branch seems to result from that of the cold water front. The baroclinic transport of the second branch was much larger than the barotropic one, but the ranges of their fluctuations were very similar with each other. 相似文献
8.
Structure of the Tsushima Current in the southwestern Japan Sea 总被引：6，自引：0，他引：6
Osamu Katoh 《Journal of Oceanography》1994,50(3):317-338
We discuss the structure of the Tsushima Current in the southwestern Japan Sea using ADCP data, which are taken by the quadrireciprocal method (Katoh, 1988) for removing tidal currents, and previous temperature data. The first, second and third branches described in the triple-branch view are recognized in three observational periods: June and August 1988 and in June 1989. The first branch basically flows eastward along the 100 m isobath. Its velocity is mostly 0.5–1.0 kt (26–51 cm s–1) and 0.4–0.6 kt (21–31 cm s–1) in the Eastern Channel of the Tsushima Strait and off the San'in Coast, respectively. In waters north of Mishima, however, a part of the first branch happens to flow northeastward, without turning clockwise along the 100 m isobath. In waters northwest of Izumo, the remainder of the first branch tends to join the second one. The second branch, which has velocities of 0.5–0.8 kt (26–41 cm s–1) in general, flows eastward along a bunch of crowded isotherms at 100 m depth. The observational results clearly illustrate the changeability of the second branch. The maximum velocity of the third branch must be larger than those of the other two branches. The Tsushima Current after leaving the Western Channel is very changeable spatially and temporally, probably because the bifurcation occurs intermittently or transiently resulting from the fluctuation of inflow through the Western Channel and from that of spread of the cold water. The bifurcation into the second and third branches becomes often obscure north of Hamada owing to confluences, even though it is recognized near the Western Channel. 相似文献
9.
We extend the flux limited diffusion theory in a moving fluid to be able to treat any combination of absoption and scattering.The extended flux limited diffusion theory is fully flux limited and displays the correct behavior in the free streaming limit and in the near thermodynamic equilibrium limit. 相似文献
10.
Masaya Saitou 《Astrophysics and Space Science》1989,162(1):47-56
Some peculiarities in the behaviour of a model self-gravitating system described by hydrodynamical equations and isothermal equation of state connected with the presence of thermodynamical fluctuations in real systems were investigated in numerical experiment. The values of density and velocity , , respectively, were computed by numerical code perturbed on each time-step and in each computational cell by random values , for modeling such fluctuations. Perturbed values
i
=
i
+
i
,v
i
=
i
+ v
i
were used to initiate the next step of computations. This procedure is equivalent to an introduction into original hydrodynamical equations of Langevin sources which are random functions. It is shown that these small fluctuations (= v =0,2 =v
2 = 10–8) grow many times in marginally-stable state. 相似文献