Sequentially sampled gas hydrate water,coupled with pore water and bottom water isotopic and ionic signatures at the Kukuy mud volcano,Lake Baikal: ambiguous deep-rooted source of hydrate-forming water     

Hirotsugu Minami  Akihiro Hachikubo  Hirotoshi Sakagami  Satoshi Yamashita  Yusuke Soramoto  Tsuyoshi Kotake  Nobuo Takahashi  Hitoshi Shoji  Tatyana Pogodaeva  Oleg Khlystov  Andrey Khabuev  Lieven Naudts  Marc De Batist 《Geo-Marine Letters》2014,34(2-3):241-251

The isotopic and ionic composition of pure gas hydrate (GH) water was examined for GHs recovered in three gravity cores (165–193 cm length) from the Kukuy K-9 mud volcano (MV) in Lake Baikal. A massive GH sample from core St6GC4 (143–165 cm core depth interval) was dissociated progressively over 6 h in a closed glass chamber, and 11 sequentially collected fractions of dissociated GH water analyzed. Their hydrogen and oxygen isotopic compositions, and the concentrations of Cl^– and HCO₃ ^– remained essentially constant over time, except that the fraction collected during the first 50 minutes deviated partly from this pattern. Fraction #1 had a substantially higher Cl^– concentration, similar to that of pore water sampled immediately above (135–142 cm core depth) the main GH-bearing interval in that core. Like the subsequent fractions, however, the HCO₃ ^– concentration was markedly lower than that of pore water. For the GH water fractions #2 to #11, an essentially constant HCO₃ ^–/Cl^– ratio of 305 differed markedly from downcore pore water HCO₃ ^–/Cl^– ratios of 63–99. Evidently, contamination of the extracted GH water by ambient pore water probably adhered to the massive GH sample was satisfactorily restricted to the initial phase of GH dissociation. The hydrogen and oxygen isotopic composition of hydrate-forming water was estimated using the measured isotopic composition of extracted GH water combined with known isotopic fractionation factors between GH and GH-forming water. Estimated δD of ?126 to ?133‰ and δ¹⁸O of ?15.7 to ?16.7‰ differed partly from the corresponding signatures of ambient pore water (δD of ?123‰, δ¹⁸O of ?15.6‰) and of lake bottom water (δD of ?121‰, δ¹⁸O of ?15.8‰) at the St6GC4 coring site, suggesting that the GH was not formed from those waters. Observations of breccias in that core point to a possible deep-rooted water source, consistent with published thermal measurements for the neighboring Kukuy K-2 MV. By contrast, the pore waters of core St6GC4 and also of the neighboring cores GC2 and GC3 from the Kukuy K-9 MV show neither isotopic nor ionic evidence of such a source (e.g., elevated sulfate concentration). These findings constrain GH formation to earlier times, but a deep-rooted source of hydrate-forming water remains ambiguous. A possible long-term dampening of key deep-water source signatures deserves further attention, notably in terms of diffusion and/or advection, as well as anaerobic oxidation of methane.  相似文献   

The effect of health benefits on climate change mitigation policies     

Masako Ikefuji  Jan R. Magnus  Hiroaki Sakamoto 《Climatic change》2014,126(1-2):229-243

This paper studies the interplay between climate, health, and the economy in a stylized world with eleven heterogeneous regions, with special emphasis on USA, Europe, China, India, and Africa. We introduce health impacts into a simple economic integrated assessment model where both the local cooling effect of SO ₂ and the global warming effect of CO ₂ are endogenous, and investigate how these factors affect the equilibrium path. Regions do not respond in the same way to climate change. In particular, emission abatement rates and health costs depend on the economic and geographical characteristics of each region. Two policy scenarios are considered, Nash and Optimal, for which we present both global and regional results. Results for Africa and China are highlighted.  相似文献   

Three‐dimensional structures and elemental distributions of Stardust impact tracks using synchrotron microtomography and X‐ray fluorescence analysis     

A. Tsuchiyama  T. Nakamura  T. Okazaki  K. Uesugi  T. Nakano  K. Sakamoto  T. Akaki  Y. Iida  T. Kadono  K. Jogo  Y. Suzuki 《Meteoritics & planetary science》2009,44(8):1203-1224

Abstract— Three‐dimensional structures and elemental abundances of four impact tracks in silica aerogel keystones of Stardust samples from comet 81P/Wild 2 (bulbous track 67 and carrot‐type tracks 46, 47, and 68) were examined non‐destructively by synchrotron radiation‐based microtomography and X‐ray fluorescence analysis. Track features, such as lengths, volumes and width as a function of track depth, were obtained quantitatively by tomography. A bulbous portion was present near the track entrance even in carrot‐type tracks. Each impact of a cometary dust particle results in the particle disaggregated into small pieces that were widely distributed on the track walls as well as at its terminal. Fe, S, Ca, Ni, and eight minor elements are concentrated in the bulbous portion of track 68 as well as in terminal grains. It was confirmed that bulbous portions and thin tracks were formed by disaggregation of very fine fragile materials and relatively coarse crystalline particles, respectively. The almost constant ratio of whole Fe mass to track volume indicates that the track volume is almost proportional to the impact kinetic energy. The size of the original impactor was estimated from the absolute Fe mass by assuming its Fe content (CI) and bulk density. Relations between the track sizes normalized by the impactor size and impact conditions are roughly consistent with those of previous hypervelocity impact experiments.  相似文献   

Baroclinic circulation and its high frequency variability in Otsuchi Bay on the Sanriku ria coast,Japan     

Kiyoshi Tanaka  Kousei Komatsu  Sachihiko Itoh  Daigo Yanagimoto  Miho Ishizu  Hiroyasu Hasumi  Takashi T. Sakamoto  Shogo Urakawa  Yutaka Michida 《Journal of Oceanography》2017,73(1):25-38

Hydrographic observations were made in Otsuchi Bay on the Sanriku ria coast, Japan, to provide clear images of the baroclinic circulation extending over the bay together with the associated intrusion of lower-layer water (bottom water) from outside the bay. In summer, a prominent baroclinic circulation with flow speeds \({>} 0.1\ \text{ m }\ \text{ s }^{-1} \) extends over the greater part of the bay. A main pycnocline (thermocline), which separates the upper and lower layers, is located at a depth of 15–40 m in and around the bay. The direction of the lower-layer flow (inflow into and outflow from the bay) is opposite to that of the upper-layer flow, which are baroclinically coupled to each other. Moreover, with regard to the lower-layer flow, the inflow tends to occur mainly through the northwestern part of the bay mouth, whereas the outflow tends to occur mainly through the southeastern part. The inflow and outflow alternate on time scales of several to a few tens of hours, and the flow directions are sometimes related to the tidal ones, although the relationship is not applied persistently. In winter, the baroclinic circulation is considerably weaker than in summer, because the stratification breaks down.  相似文献   

Impacts of climate change on growth, migration and recruitment success of Japanese sardine (Sardinops melanostictus) in the western North Pacific     

Takeshi Okunishi  Shin-ichi Ito  Taketo Hashioka  Takashi T. Sakamoto  Naoki Yoshie  Hiroshi Sumata  Yumiko Yara  Naosuke Okada  Yasuhiro Yamanaka 《Climatic change》2012,115(3-4):485-503

We developed a multi-trophic level ecosystem model by coupling physical, biogeochemical-plankton and fish models. An oceanic general circulation model was coupled with a lower trophic level ecosystem model and a Japanese sardine migration model, and applied to the western North Pacific. To investigate the impact of global warming on the pelagic fish ecosystem, such as Japanese sardine, we conducted numerical experiments of growth and migration of Japanese sardine using physical fields for the present day and future with a global warming scenario simulated by a high-resolution climate model. The model results demonstrated possible impacts of global warming on the growth and migration pattern of Japanese sardine. The growths of fish in the current main spawning region under the global warming scenario were significantly slower than those under the present climate scenario. Fish in this region will be at disadvantage for their recruitment under the global warming condition. Prey conditions in the spawning region were projected not to markedly change under global warming condition while water temperature increased. As a result sardine spawning ground was projected to shift towards more north areas. During the feeding migration period in summer, geographical distribution of juveniles fish was projected to shift northwards by one to two degrees latitude under the global warming condition following the change in the distribution of optimal temperature region for feeding. However, this northwards shift of the optimal temperature for feeding was minimized adjacent to the western North Pacific by the cooler water supply by the intensification of the Oyashio.  相似文献   

A numerical model for far-field tsunamis and its application to predict damages done to aquaculture   总被引：2，自引：0，他引：2  

Osami Nagano  Fumihiko Imamura  Nobuo Shuto 《Natural Hazards》1991,4(2-3):235-255

The 1960 Chilean tsunami which traveled the Pacific Ocean and caused much damages to Japan is simulated from its generation to the terminal effects on coastal areas. In the computation of ocean propagation by the linear longwave theory, a new technique is introduced to keep the same accuracy as the linear Boussinesq equation and reduce the CPU time as well as the computer memory. In the coastal transformation computation, the energy dissipation due to sea-bottom scouring is suggested to be included, particularly in the case of long bays. To obtain accurate results, the current velocity requires finer spatial grids than the water surface elevation. Damage done to pearl culture rafts are explained in terms of the computed current velocity.  相似文献   

Gas dynamics and structure of galaxies     

Kazushi Sakamoto 《Astrophysics and Space Science》2008,313(1-3):245-251

Between gas dynamics and structure of galaxies is a two-way relation. On one hand, gas dynamics in a galaxy is largely determined by the structure of the galaxy, and on the other hand, gas dynamics can gradually alter the galaxy structure through redistribution of mass and angular momentum within the galaxy. The first half of this relation should mostly determine gas distribution and regulate star formation in undisturbed spirals, and the second half has been suggested to cause secular evolution of spiral galaxies—a slow mode of galaxy evolution in the absence of major mergers. Our knowledge on this relation is going to be greatly deepened by the ALMA. Focusing on the galaxy evolution through gas dynamics, I briefly review what we know about the subject. Then I try to look out what the ALMA can do to answer open questions in the field. It is pointed out that the ALMA will be able to fully map all the spiral galaxies between 1 and 25 Mpc at 1″ resolution in 1000 hours.  相似文献   

Detection and hydrologic modeling of aquifers in unconsolidated alluvial plains through combination of borehole data sets: a case study of the Arao area, Southwest Japan     

Katsuaki Koike  Hidehumi Sakamoto  Michito Ohmi   《Engineering Geology》2001,62(4):301-317

In addition to spatial distribution of groundwater-flow parameters, aquifer properties of location and shape are also significant for assessing groundwater resources because they strongly affect water flow. We present a selection of geologic data suitable for aquifer analysis, a mathematical method of processing them, and a combination of several maps produced by it. The data used in the analysis are typically obtained by borehole investigation. Our targets are the areas underlain by geologic bodies with different ages and lithologies; the spatial correlation structures of geologic data over the areas tend to change locally. The processing method should be a versatile one that is applicable to areas where geostatistical stationarity is not satisfied. The aquifer analysis consistent with that requirement consists of two steps: the first is the transformation of screen locations, locations of sand and gravel layers, and resistivity by electric logging into indicator values, and the second is three-dimensional interpolation of these using the optimization principle method to produce three kinds of distribution models. A stochastic simulation is also used for modeling the resistivity distribution. The three distribution models are integrated to generate a value for evaluating the possibility of aquifer existence. A case study of an alluvial coastal plain, situated in southwest Japan, describes an aquifer model that contains three permeable layers. Each layer has about 10-m thickness and is lens shaped. To confirm the validity of the model, we have drilled two wells that reached one of the middle and bottom permeable layers, observing the water level change. Low correlation of the temporal changes of levels between the wells indicates that the two layers are hydrologically independent of each other. Additionally, groundwater-flow patterns have been estimated by transforming the simulation model parameter into hydraulic conductivity through a simple function and using a finite difference method for flow analysis. The procedure proposed by this study can be applied to other areas by changing the weights assigned to each geologic and geotechnical factor in the generation of the coefficient for aquifer existence, considering the reliability of each factor and hydrologic properties of study area.  相似文献   

Subducting oceanic crusts of the Philippine Sea and Pacific plates and weak-zone-normal compression in the Kanto district, Japan   总被引：1，自引：0，他引：1  

Nobuo Hurukawa  Masajiro Imoto 《Geophysical Journal International》1992,109(3):639-652

  相似文献   

The superstructure of plagioclase feldspars     

Yoshiharu Nakajima  Nobuo Morimoto  Masao Kitamura 《Physics and Chemistry of Minerals》1977,1(2):199-212

A modulation function representing the position and density of (Na, Ca) atoms in the superstructure of the e-plagioclase has been derived from the average structures of different plagioclase and a general modulation theory. Based on this function the superstructure of bytownite (An₇₃) has been studied with the single crystal X-ray method. The cell dimensions by Megaw's axes are a=7.946(3)A, b=67.09(2)A, c=12.236(4)A, α=39.03(1)°, β=45.63(1)° and γ=59.63(1)°. Z=18(Na, Ca) Al(Al, Si)Si₂O₈. The initial phase factor of the modulation function for bytownite has been obtained from the intensity data of the satellite reflections. This modulation function indicates a coherent small-scale alternation of the Na-rich and Ca-rich bands in the superstructure. This superstructure has been refined by applying the albite and anorthite structures to the Na-rich and Ca-rich bands, respectively. The change of the superstructure of the e-plagioclase due to the compositional change has been described based on the movements of the satellites in reciprocal space. The direction of the coherent small-scale intergrowth of the anorthite-like and albite-like bands is perpendicular to the t vector. The thickness of the intergrowth is 1/|t|. Both direction and thickness change regularly from An₇₅ to An₂₅.  相似文献