Deep-Sea Chemoautosynthesis-Based Communities in the Northwestern Pacific   总被引：3，自引：0，他引：3  

Shigeaki Kojima 《Journal of Oceanography》2002,58(2):343-363

I review chemoautosynthesis-based faunal communities which have been discovered in the deep-sea areas in the Northwestern Pacific. Fauna of each community and further biological studies are summarized. Zoogeographical and evolutionary status of communities in the Northwestern Pacific is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Biomass and production of bacterioplankton at the hydrothermal vent areas in the rift system of the North Fiji Basin     

Utsumi  Motoo  Kojima  Shigeaki  Nojiri  Yukihiro  Ohta  Suguru  Seki  Humitake 《Journal of Oceanography》1994,50(6):635-642

Mesoscale distribution of the density and productivity of bacterioplankton at representative geological locations in the rift ecosystem of the North Fiji Basin were clarified by sampling using a mannedShinkai 6500 submersible. The bacterioplankton density inside the hot and warm fluids of hydrothermal vents was one order magnitude greater than that in the deep water outside the vent plume. The bacterial production was highest inside the hot and warm vent fluids, and was higher just outside the hot and warm vent fluids than further outside in the deep water surrounding the vent plume, respectively. Productivity from outside to inside the vent fluid varied from 0.01 to 0.71 gC m^–3 day^–1.  相似文献   

Landslide detection based on height and amplitude differences using pre- and post-event airborne X-band SAR data     

Uemoto  Jyunpei  Moriyama  Toshifumi  Nadai  Akitsugu  Kojima  Shoichiro  Umehara  Toshihiko 《Natural Hazards》2019,95(3):485-503

Natural Hazards - The recognition of landslides and making their inventory map are considered to be urgent tasks not only for damage estimation but also for planning rescue and restoration...  相似文献   

Revisiting ENSO impacts on the Indian Ocean SST based on a combined linear regression method     

Lianyi Zhang  Yan Du  Tomoki Tozuka  Shoichiro Kido 《海洋学报(英文版)》2021,40(5):47-57

The El Ni?o-Southern Oscillation (ENSO) has great impacts on the Indian Ocean sea surface temperature (SST). In fact, two major modes of the Indian Ocean SST namely the Indian Ocean Basin (IOB) and the Indian Ocean Dipole (IOD) modes, exerting strong influences on the Indian Ocean rim countries, are both influenced by the ENSO. Based on a combined linear regression method, this study quantifies the ENSO impacts on the IOB and the IOD during ENSO concurrent, developing, and decaying stages. After removing the ENSO impacts, the spring peak of the IOB disappears along with significant decrease in number of events, while the number of events is only slightly reduced and the autumn peak remains for the IOD. By isolating the ENSO impacts during each stage, this study reveals that the leading impacts of ENSO contribute to the IOD development, while the delayed impacts facilitate the IOD phase switch and prompt the IOB development. Besides, the decadal variations of ENSO impacts are various during each stage and over different regions. These imply that merely removing the concurrent ENSO impacts would not be sufficient to investigate intrinsic climate variability of the Indian Ocean, and the present method may be useful to study climate variabilities independent of ENSO.  相似文献   

Inverse estimation of drifting-object outflows using actual observation data     

Shin’ichiro Kako  Atsuhiko Isobe  Satoquo Seino  Azusa Kojima 《Journal of Oceanography》2010,66(2):291-297

The present study attempts to establish a scientifically reliable method capable of computing the drifting-object sources and their outflows. First, the temporal variability of the drifting-object amount is investigated every two months on a beach west of Japan, where various source regions are anticipated because of spatiotemporally variable northeastward ocean currents over the East China Sea. Next, in order to specify drifting-object sources, two-way particle tracking model (PTM) experiments are carried out using simulated ocean currents and leeway drift estimated from QuikSCAT/Seawinds wind data. Finally, an inverse method with a Lagrange multiplier is applied to estimate drifting-object outflows at each source on the basis of the two-way PTM results and beach surveys. Accuracy of object-source identification using the two-way PTM is validated by comparing disposable-lighter sources suggested by phone numbers printed on the lighter surface with those computed by the model. In order to examine the reliability of the inverse estimation, the number of plastic-bottle caps found in actual beach surveys is compared with that computed using a forward in-time PTM during the same period of actual beach surveys, over which the outflows obtained using the inverse method are given at each source in the model.  相似文献   

Multicell Model for Ground Water Recharge Analysis: The Ibi River Basin, Japan     

Takeshi Sato  Junichi Kojima  Hugo A. Loaiciga 《Ground water》1999,37(1):58-69

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Effect of air mobility in a soil pipe on water flow through a model hillslope after pipe clogging     

Takuhei Yamasaki  Shoichiro Hamamoto  Taku Nishimura 《地球表面变化过程与地形》2020,45(4):905-911

Soil pipes (continuous macropores expanding laterally in the soil subsurface) are a key factor controlling hillslope water cycles and sediment transport. Soil pipes usually enhance slope stability under rainfall events through their high water drainage ability, and pipe clogging by sediments is regarded as a risk for slope failure. In this study, we conducted a bench-scale pipe clogging experiment to clarify the effect of air mobility in soil pipes on water flow and water pressure build-up in the slope at the clogged point. Before pipe clogging, the soil pipe drained rainwater effectively and lowered the groundwater table. After the pipe clogging event, the mobility of air in the soil pipe before the clogging determined the water flow in the slope. When the air in the soil pipe connected to the atmosphere and moved freely, the water level in the soil pipe increased at the pipe clogging, and water pressure build-up was limited near the pipe outlet. On the other hand, when air in the soil pipe was entrapped by the clogging, water pressure suddenly increased, and the groundwater table of the whole slope rose correspondingly. This study clearly demonstrated the importance of pipe morphology with respect to air connectivity between the pipe and atmosphere to elucidate the water flow and slope stability during the pipe clogging event. © 2019 John Wiley & Sons, Ltd.  相似文献   

Correlation between Expansion Rate of the Coronal Magnetic Field and Solar Wind Speed in a Solar Activity Cycle     

Kazuyuki?HakamadaEmail author  Masayoshi?Kojima  Tomoaki?Ohmi  Munetoshi?Tokumaru  Ken’ichi?Fujiki 《Solar physics》2005,227(2):387-399

Thirteen synoptic maps of expansion rate of the coronal magnetic field (CMF; RBR) calculated by the so-called ‘potential model’ are constructed for 13 Carrington rotations from the maximum phase of solar activity cycle 22 through the maximum phase of cycle 23. Similar 13 synoptic maps of solar wind speed (SWS) estimated by interplanetary scintillation observations are constructed for the same 13 Carrington rotations as the ones for the RBR. The correlation diagrams between the RBR and the SWS are plotted with the data of these 13 synoptic maps. It is found that the correlation is negative and high in this time period. It is further found that the linear correlation is improved if the data are classified into two groups by the magnitude of radial component of photospheric magnetic field, |B^pho_r|; group 1, 0.0 G ≦ |B_r^pho| < 17.8 G and group 2, 17.8 G ≦ |B_r^pho|. There exists a strong negative correlation between the RBR and the SWS for the group 1 in contrast with a weak negative correlation for the group 2. Group 1 has a double peak in the density distribution of data points in the correlation diagram; a sharp peak for high-speed solar wind and a low peak for low-speed solar wind. These two peaks are located just on the axis of maximum variance of data points in the correlation diagram. This result suggests that the solar wind consists of two major components and both the high-speed and the low-speed winds emanating from weak photospheric magnetic regions are accelerated by the same mechanism in the course of solar activity cycle. It is also pointed out that the SWS can be estimated by the RBR of group 1 with an empirical formula obtained in this paper during the entire solar activity cycle.  相似文献   

Genetic diversity and population structure of three dominant myctophid fishes (<Emphasis Type="Italic">Diaphus theta,Stenobrachius leucopsarus</Emphasis>, and <Emphasis Type="Italic">S. nannochir</Emphasis>) in the North Pacific Ocean     

Shigeaki Kojima  Masatoshi Moku  Kouichi Kawaguchi 《Journal of Oceanography》2009,65(2):187-193

We compared the genetic diversity of three dominant myctophid fishes in the North Pacific Ocean that have different diel vertical migration patterns on the basis of the nucleotide sequences of the mitochondrial gene for cytochrome b. No genetic structure was detected for each of these three species. The genetic diversity progressively increased for Diaphus theta, a diel migrant species showing clear diel vertical migration; Stenobrachius leucopsarus, a semi-diel migrant, in which only part of the population migrates vertically; S. nannochir, a non-diel migrant. All three species were suggested to have experienced a recent, sudden population expansion. Interspecific differences in genetic diversity might be attributable to differences in the degree of population size reduction during the glacial periods; this degree in turn corresponds to the energy demand of the fishes.  相似文献   

Petrology and mineralogy of the shock-melted H chondrites Yamato–791088 and LaPaz Ice Field 02240     

Takafumi Niihara  Naoya Imae  Keiji Misawa  Hideyasu Kojima   《Polar Science》2011,4(4):558-573

We studied the petrology and mineralogy of two types of shock-melted H chondrites: Yamato (Y)–791088 and LaPaz Ice Field (LAP) 02240. Y–791088, which consists of numerous coarse-grained relict phases (40%) and euhedral fine-grained minerals solidified from the shock melt (60%), experienced incomplete melting; a quiescent melt is indicated by the existence of abundant relict phases, pseudomorphed chondrules, and two types of glass. LAP 02240, which consists of small amounts of coarse-grained relict phases (～10%) and fine-grained minerals (～90%), experienced near-complete melting; a rapidly cooled mobilized melt is indicated by the homogeneous compositions of glass and opaque veins.The homogeneous compositions of relict olivines indicate that the precursors of both chondrites were equilibrated H chondrites. The melting features of Y–791088 and LAP 02240 are very similar to those of Y–790964 (LL) and the fine-grained lithology of Y–790519 (LL), respectively. These two types of shock-melted ordinary chondrites possibly formed in situ during dike formation. The quiescent melt is thought to have originated from the injection of shock-heated chondrite blocks into mobilized melt. These two types of melting could have occurred during dike formation on the H chondrite parent body. The textures of the two types of shock melts were not simply affected by the degree of shock melting: they were also controlled by the degree of shear stress.  相似文献