A three-dimensional ocean general circulation model for mesoscale eddies——Ⅱ Diagnostic analysis     

Wang Ji  Moto Ikeda 《海洋学报(英文版)》1997,16(1):29-43

A three-dimensional density field associated with mesoscaie unstable waves generated by the 3-D, primitive-equation model (Wang and Ikeda, 1996) is provided to the quasi-geostrophic pressure tendency and ω-equations, and to the (ageostrophic) Q-vector equation. Diagnostic analyses, analogous to the approaches in meteorology: ω-equation and Q-vector method, are for the first time developed to examine the mesoscaie dynamical processes and mechanisms of the unstable waves propagating in the mid-latitude ocean. The weaknesses and strengths of these two diagnostic approaches are evaluated and compared to the model results. The Q-vector method is then recommended to diagnose the vertical motion associated with the mesoscaie dynamics from a hydrographic CTD (conductivity-temperature-depth) array, while the quasi-geostrophic equations produce some small-scale features (errors) in the diagnosed fields.  相似文献   

Assimilated carbon budget for the hyperiid amphipodThemisto japonica (bovallius) from the Japan sea as influenced by temperature     

Tsutomu Ikeda 《Journal of Oceanography》1991,47(1):7-16

Using a growth model based on moult number, the assimilated carbon budget was constructed forThemisto japonica growing from the specimens just released from the marsupium to mature adults at 1–15°C. As budget parameters, growth (G), metabolism (Me), moult (Mo), and reproduction (Re) were measured and assimilation (A) was estimated as the sum of these four parameters (A=G+Me +Mo +Re). The results of the lifetime budget indicated that among these parameters the greatest allocation ofA was toMe (70–83%). Lifetime expenditure of carbon forMe was the least at 7°C, andMe increased with either increase or decrease of the temperature from 7°C. A female grown to full adult size at 7°C invested 16.6 % forG, 70.2% forMe, 2.1% forMo, and 11.1% forRe of totalA. General features seen in the partition ofA toG, Me, Mo, andRe forT. japonica are similar to those of other planktonic crustaceans being reported. Considering the profound effect of temperature on the assimilated carbon budget, practical problems in defining the representative habitat temperature for diel vertical migrators likeT. japonica in the field are discussed.  相似文献   

The Role of Zooplankton in Global Ecosystem Dynamics: Comparative Studies from the World Oceans     

Valdes  Luis; Harris  Roger; Ikeda  Tsutomu; McKinnell  Skip; Peterson  William T 《ICES Journal of Marine Science》2004,61(4):441-444

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A growth model for a hyperiid amphipodThemisto japonica (bovallius) in the Japan Sea,based on its intermoult period and moult increment     

Tsutomu Ikeda 《Journal of Oceanography》1990,46(6):261-272

Themisto japonica was reared at 1, 5, 8, and 12°C in the laboratory to estimate its intermoult period (IP) and increase in body length (BL) at each moulting (BL).IP was found to be a function of temperature andBL of the specimens, longerIPs being associated with lower temperature and larger specimens.BL was not affected by temperature but increased with growth of the specimens. Observations on consecutive moults indicated that one new segment was added to pleopod rami at each moulting.BLs obtained from the measurement of the segment number of pleopod rami andBL of wild specimens were slightly larger than values obtained from laboratory-raised specimens.IP data obtained from laboratory-reared specimens are combined withBL data from wild specimens to establish a growth model forT. japonica from its release from the marsupium (1.31 mmBL) to the maximum size (17 mmBL) as a function of temperature. This growth model predicts that a total of of 18 moultings is needed forT. japonica to reach the maximum size regardless of temperature, although the time needed to reach the maximum size is highly dependent on temperature. The life cycle, from the newly released larvae (1.31 mmBL) to the spent females (10–17 mmBL), was estimated as 333–593 days at 1°C, 195–347 days at 5°C, 118–210 days at 10°C and 82–146 days at 15°C; the last may be the upper temperature limit forT. japonica. Growth rates ofT. japonica expressed on the basis of body mass are comparable to the rates of euphausiids of equivalent size when the effect of temperature is accounted for. Feeding conditions ofT. japonica in the field are also discussed.  相似文献   

Determination of Sr/Sr mass-dependent isotopic fractionation and radiogenic isotope variation of Sr/Sr in the Neoproterozoic Doushantuo Formation     

Takeshi Ohno  Tsuyoshi Komiya  Yuichiro Ueno  Takafumi Hirata  Shigenori Maruyama 《Gondwana Research》2008,14(1-2):126

We measured both mass-dependent isotope fractionation of δ⁸⁸Sr (⁸⁸Sr/⁸⁶Sr) and radiogenic isotopic variation of Sr (⁸⁷Sr/⁸⁶Sr) for the Neoproterozoic Doushantuo Formation that deposited as a cap carbonate immediately above the Marinoan-related Nantuo Tillite. The δ⁸⁸Sr and ⁸⁷Sr/⁸⁶Sr compositions showed three remarkable characteristics: (1) high radiogenic ⁸⁷Sr/⁸⁶Sr values and gradual decrease in the ⁸⁷Sr/⁸⁶Sr ratios, (2) anomalously low δ⁸⁸Sr values at the lower part cap carbonate, and (3) a clear correlation between ⁸⁷Sr/⁸⁶Sr and δ⁸⁸Sr values. These isotopic signatures can be explained by assuming an extreme greenhouse condition after the Marinoan glaciation. Surface seawater, mixed with a large amount of freshwater from continental crusts with high ⁸⁷Sr/⁸⁶Sr and lighter δ⁸⁸Sr ratios, was formed during the extreme global warming after the glacial event. High atmospheric CO₂ content caused sudden precipitation of cap carbonate from the surface seawater with high ⁸⁷Sr/⁸⁶Sr and lighter δ⁸⁸Sr ratios. Subsequently, the mixing of the underlying seawater, with unradiogenic Sr isotope compositions and normal δ⁸⁸Sr ratios, probably caused gradual decrease of the ⁸⁷Sr/⁸⁶Sr ratios of the seawater and deposition of carbonate with normal δ⁸⁸Sr ratios. The combination of ⁸⁷Sr/⁸⁶Sr and δ⁸⁸Sr isotope systematics gives us new insights on the surface evolution after the Snowball Earth.  相似文献   

Evaluation of change in subsurface thermal environment due to groundwater flow in the Tokyo Lowland,Japan     

Akinobu Miyakoshi  Takeshi Hayashi  Atsunao Marui  Yasuo Sakura  Shinichi Kawashima  Masafumi Kawai 《International Journal of Earth Sciences》2008,97(2):401-411

Information on the distribution of subsurface temperature and hydraulic heads at 24 observation wells in and around the Tokyo Lowland, the eastern part of the Tokyo Metropolitan area, were examined to make clear the relationship between groundwater and the subsurface thermal environment in the urban area. Minimums in temperature–depth logs due to subsurface temperature increasing at shallow parts were recognized in 21 wells. This fact shows subsurface temperature is affected by ground surface warming in almost all of this area. Deeper than minimums, where the effects of surface warming became relatively small, regional variation is observed as follows: high temperatures are shown in the central part to the southern part, and low temperatures shown in the inland to eastern part. The high temperature area corresponds to an area where the lower boundary of groundwater flow is relatively shallow. This area corresponds also to an area with severe land subsidence resulting from excessive groundwater pumping. It is considered that this high temperature area is formed by the effects of upward groundwater flow affected by hydrogeological conditions and pumping. On the other hand, a comparison between past data (1956–1967) and present data (2001–2003) revealed widespread decreasing temperature in the inland area. This is explained by downward groundwater flow based on an analysis of temperature–depth logs. This fact suggests that subsurface temperature is not only increasing from the effects of surface warming but also decreasing from the effects of groundwater environment change due to pumping.  相似文献   

A continuous and mechanistic representation of calcite reaction-controlled kinetics in dilute solutions at 25°C and 1 atm total pressure     

Takeshi Arakaki  Alfonso Mucci 《Aquatic Geochemistry》1995,1(1):105-130

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Ecologic and taxonomic diversification in the Mesozoic brackish-water bivalve faunas in Japan, with emphasis on infaunalization of heterodonts     

Yasuo Kondo  Takeshi Kozai  Naoki Kikuchi  Kazuhiro Sugawara 《Gondwana Research》2006,10(3-4):316-327

Mesozoic brackish-water bivalve faunas in Japan diversified in three steps: at the beginning of the Early Jurassic, Early and Late Cretaceous. The Hettangian Niranohama Fauna in northeastern Honshu represents the establishment of a heterodont-dominated brackish-water fauna that persisted until the early Late Cretaceous. No similar composition is known from the Triassic. The infauna consists mostly of non-siphonate and some short-siphonate heterodonts, while the epifauna is represented by diverse pteriomorphian families. In the Early Cretaceous Tetori Group in central Honshu, the long-siphonate heterodonts Tetoria (Corbiculidae) and the semi-infaunal soft-bottom oyster Crassostrea appeared. The evolutionary diversification of the latter, known as the most important element of modern brackish-water faunas, may thus originate at that time. In the early Late Cretaceous (Cenomanian) of the Goshoura and Mifune Groups in west Kyushu, several euryhaline deep-burrowing heterodont families, such as Veneridae and Tellinidae, further diversified in the brackish and marine environments. The Late Cretaceous is characterized by massive shell biolithic beds in which large Crassostrea species are common, a feature common for Cenozoic brackish-water faunas. The long-term changes in the composition of the brackish-water faunas in Japan represents thus an evolutionary record, irrespective of the severe physiological and environmental conditions imposed on the highly conservative nature of the fauna.  相似文献   

Slip-weakening distance in dynamic rupture of in-slab normal-faulting earthquakes   总被引：1，自引：0，他引：1  

Takeshi Mikumo  Yuji Yagi 《Geophysical Journal International》2003,155(2):443-455

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Measuring the k–S–p relations on DNAPLs migration     

Masashi Kamon  Kazuto Endo  Takeshi Katsumi 《Engineering Geology》2003,70(3-4):351-363

Migration characteristics of dense non-aqueous phase liquids (DNAPLs) in the subsurface can be expressed as a water–DNAPL two-phase system based on mainly the k–S–p relations, which describe the relations among relative permeability (k), degree of water saturation (S), and capillary pressure head (p). The aims of this research are to develop an experimental system with new type of probes, such as the electrical conductivity probe for measuring the degree of water saturation and the hydrophilic and hydrophobic tensiometer for measuring the pore water and DNAPL pressures, and also to estimate the results obtained from the developed experimental system. From these tests, the excellent k–S–p relations were obtained and the efficiency and validity of this developed experimental system have been confirmed in terms of the concept of the scaling coefficient calculated by interfacial tensions.  相似文献