Identification of the fronts from the Kuroshio Extension to the Subarctic Current using absolute dynamic topographies in satellite altimetry products     

Hideyuki Nakano  Hiroyuki Tsujino  Kei Sakamoto  Shogo Urakawa  Takahiro Toyoda  Goro Yamanaka 《Journal of Oceanography》2018,74(4):393-420

The climatologies and variabilities of the fronts associated with the Kuroshio Extension (KE), the Kuroshio Extension Northern Branch (KENB), the flow along the Subarctic Boundary (SAB), and the Subarctic Current (SAC) are identified by a new method based on the absolute dynamic height product from the archiving, validation, and interpretation of satellite oceanographic data (the AVISO product). The fronts are detected by examining the specific contour values of the absolute dynamic topography (ADT) in the AVISO product. The (time-varying) specific contour values are decided from the local maxima of the averaged surface geostrophic velocity along the ADT. Assuming the specific contours as the front locations, we obtain an occurrence frequency map of the four front locations, and determine the monthly variability of the fronts over the 1993–2015 period. The results are validated by hydrographic observations. The KE and KENB east of the Shatsky Rise migrate southward several times at a speed of ~ 0.2 cm s^?1, while the SAB and SAC are mostly stationary.  相似文献   

Development of a new operational system for monitoring and forecasting coastal and open-ocean states around Japan     

Hirose  Nariaki  Usui  Norihisa  Sakamoto  Kei  Tsujino  Hiroyuki  Yamanaka  Goro  Nakano  Hideyuki  Urakawa  Shogo  Toyoda  Takahiro  Fujii  Yosuke  Kohno  Nadao 《Ocean Dynamics》2019,69(11):1333-1357

We developed a new system to monitor and forecast coastal and open-ocean states around Japan for operational use by the Japan Meteorological Agency. The system consists of an eddy-resolving analysis model based on four-dimensional variational assimilation and a high (2-km) resolution forecast model covering Japanese coastal areas that incorporates an initialization scheme with temporal and spatial filtering. Assimilation and forecast experiments were performed for 2008 to 2017, and the results were validated against various observation datasets. The assimilation results captured well the observed variability in sea surface temperature, coastal sea level, volume transport, and sea ice. Furthermore, the volume budget for the Japan Sea was significantly improved by the use of the 2-km resolution forecast model compared with the 10-km resolution analysis model. The forecast results indicate that this system has a predictive limit longer than 1 month in many areas, including in the Kuroshio current area south of Japan and the southern Japan Sea. In the forecast results of case studies, the 2017 Kuroshio large meander was well predicted, and warm water intrusions accompanying Kuroshio path variations south of Japan were also successfully reproduced. Sea ice forecasts for the Sea of Okhotsk largely captured the evolution of sea ice in late winter, but sea ice in early winter included relatively large errors. This system has high potential to meet operational requirements for monitoring and forecasting ocean phenomena at both meso- and coastal scales.

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Timing of multiple hydrothermal events in the iron oxide–copper–gold deposits of the Southern Copper Belt,Carajás Province,Brazil     

Carolina?P.?N.?MoretoEmail author  Lena?V.?S.?Monteiro  Roberto?P.?Xavier  Robert?A.?Creaser  S.?Andrew?DuFrane  Gustavo?H.?C.?Melo  Marco?A.?Delinardo da Silva  Colombo?C.?G.?Tassinari  Kei?Sato 《Mineralium Deposita》2015,50(5):517-546

The Southern Copper Belt, Carajás Province, Brazil, hosts several iron oxide–copper–gold (IOCG) deposits, including Sossego, Cristalino, Alvo 118, Bacuri, Bacaba, Castanha, and Visconde. Mapping and U–Pb sensitive high-resolution ion microprobe (SHRIMP) IIe zircon geochronology allowed the characterization of the host rocks, situated within regional WNW–ESE shear zones. They encompass Mesoarchean (3.08–2.85 Ga) TTG orthogneiss, granites, and remains of greenstone belts, Neoarchean (ca. 2.74 Ga) granite, shallow-emplaced porphyries, and granophyric granite coeval with gabbro, and Paleoproterozoic (1.88 Ga) porphyry dykes. Extensive hydrothermal zones include albite–scapolite, biotite–scapolite–tourmaline–magnetite alteration, and proximal potassium feldspar, chlorite–epidote and chalcopyrite formation. U–Pb laser ablation multicollector inductively coupled mass spectrometry (LA-MC-ICP-MS) analysis of ore-related monazite and Re–Os NTIMS analysis of molybdenite suggest multiple Neoarchean (2.76 and 2.72–2.68 Ga) and Paleoproterozoic (2.06 Ga) hydrothermal events at the Bacaba and Bacuri deposits. These results, combined with available geochronological data from the literature, indicate recurrence of hydrothermal systems in the Southern Copper Belt, including 1.90–1.88-Ga ore formation in the Sossego–Curral ore bodies and the Alvo 118 deposit. Although early hydrothermal evolution at 2.76 Ga points to fluid migration coeval with the Carajás Basin formation, the main episode of IOCG genesis (2.72–2.68 Ga) is related to basin inversion coupled with Neoarchean (ca. 2.7 Ga) felsic magmatism. The data suggest that the IOCG deposits in the Southern Copper Belt and those in the Northern Copper Belt (2.57-Ga Salobo and Igarapé Bahia–Alemão deposits) do not share a common metallogenic evolution. Therefore, the association of all IOCG deposits of the Carajás Province with a single extensive hydrothermal system is precluded.  相似文献   

Effects of polychlorinated biphenyls on liver function and sexual characteristics in Japanese medaka (Oryzias latipes)     

Nakayama K  Sei N  Handoh IC  Shimasaki Y  Honjo T  Oshima Y 《Marine pollution bulletin》2011,63(5-12):366-369

The effects of polychlorinated biphenyls (PCBs) on liver function and their differences between sexes were analyzed in Japanese medaka (Oryzias latipes) exposed to PCB126 or Kanechlor-400 (KC-400) using microarray. PCB exposure induced vitellogenin 1 expression in female medaka while suppressing choriogenin genes, which suggests that the effects of PCBs on estrogen-responsive genes do not occur directly through an estrogen receptor-mediated pathway. Reduction of androgen receptor alpha expression was also observed, and the gene expression pattern in PCB-exposed males changed to become more similar to that of females. Furthermore, changes in glycolysis-related genes indicate that PCB exposure might enhance glucose production via gluconeogenesis in the liver of medaka. Taken together, our results suggest that PCBs disrupt the endocrine system, especially androgen function, and may have the potential to cause demasculinizing effects. Additionally, induction of gluconeogenesis might be a response to maintain glucose levels consumed as a result of PCB exposures.  相似文献   

Effects of Recharge Wells and Flow Barriers on Seawater Intrusion   总被引：2，自引：0，他引：2  

Roger Luyun Jr.  Kazuro Momii  Kei Nakagawa 《Ground water》2011,49(2):239-249

The installation of recharge wells and subsurface flow barriers are among several strategies proposed to control seawater intrusion on coastal groundwater systems. In this study, we performed laboratory‐scale experiments and numerical simulations to determine the effects of the location and application of recharge wells, and of the location and penetration depth of flow barriers, on controlling seawater intrusion in unconfined coastal aquifers. We also compared the experimental results with existing analytical solutions. Our results showed that more effective saltwater repulsion is achieved when the recharge water is injected at the toe of the saltwater wedge. Point injection yields about the same repulsion compared with line injection from a screened well for the same recharge rate. Results for flow barriers showed that more effective saltwater repulsion is achieved with deeper barrier penetration and with barriers located closer to the coast. When the flow barrier is installed inland from the original toe position however, saltwater intrusion increases with deeper barrier penetration. Saltwater repulsion due to flow barrier installation was found to be linearly related to horizontal barrier location and a polynomial function of the barrier penetration depth.  相似文献   

Experimental Constraints on the Thermal Peak of a Granulite from McIntyre Island, Enderby Land, East Antarctica     

Toshisuke Kawasaki  Kei Sato  Yoichi Motoyoshi 《Gondwana Research》2002,5(4):749-756

High-pressure experiments have been carried out at 11-22 kbar and 900-1200°C using a piston cylinder apparatus to constrain the thermal peak condition of a granulite characterized by the mineral assemblage of orthopyroxene+sillimanite+quartz from McIntyre Island, Enderby Land, East Antarctica. The bulk composition of the starting material is 85 wt.% McIntyre granulite+15 wt.% sillimanite. At 11 kbar, orthopyroxene, sillimanite and quartz are stable below 1000°C. At 1050°C sillimanite does not appear, and sapphirine coexists with orthopyroxene and quartz. These experimental results indicate that the McIntyre granulite has undergone the ultra high-temperature metamorphism at 1000-1050°C represented by the diagnostic mineral assemblage of orthopyroxene, sillimanite and quartz.  相似文献   

Iron partitioning in pyrolitic lower mantle     

Ryosuke Sinmyo  Kei Hirose 《Physics and Chemistry of Minerals》2013,40(2):107-113

The partitioning of iron between Mg-rich perovskite (Pv) and ferropericlase (Fp) was investigated for a pyrolitic bulk composition over a wide range of simulated lower-mantle pressures and temperatures from 28 to 114 GPa and from 1,900 to 2,300 K, in a laser-heated diamond anvil cell (DAC). The recovered DAC samples are chemically homogeneous, indicating a relatively small temperature gradient during laser heating. The chemical compositions of coexisting Pv, Fp, and Ca-rich perovskite (CaPv) were determined by energy-dispersive X-ray spectroscopy (EDS) using an EDS instrument attached to a transmission electron microscope. Our results demonstrate that at pressures above 90 GPa, Pv becomes more Fe-rich with increasing pressure, which is likely due to the effects of high-spin to low-spin crossover of Fe³⁺ in Pv. We highlight that such a change in Fe–Mg partitioning between Pv and Fp should have a strong influence on the physical properties of the deep lower mantle.  相似文献   

In situ X-ray diffraction measurements of the <Emphasis Type="Italic">fcc</Emphasis>–<Emphasis Type="Italic">hcp</Emphasis> phase transition boundary of an Fe–Ni alloy in an internally heated diamond anvil cell     

Tetsuya?KomabayashiEmail author  Kei?Hirose  Yasuo?Ohishi 《Physics and Chemistry of Minerals》2012,39(4):329-338

The phase transition boundary between the face-centered cubic (fcc) structure and hexagonal close-packed (hcp) structure in an Fe–Ni alloy was determined at pressures from 25 to 107 GPa by using an internally resistive-heated diamond anvil cell (DAC), combined with in situ synchrotron X-ray diffraction measurements. The fcc–hcp phase transition boundary in Fe–9.7 wt% Ni is located at slightly lower temperatures than that in pure Fe, confirming the previous understanding that the addition of Ni expands the stability field of the fcc phase. The dP/dT slope of the boundary was determined to be 0.0426 GPa/K, which is slightly larger than that of pure Fe. The pressure interval of the two-phase region is about 6 GPa at a constant temperature, implying that the previous estimates by laser-heated DAC experiments of 10–20 GPa were overestimated. The two-phase region of fcc + hcp would be limited to a pressure of about 120 GPa even in Fe–15 wt%Ni, excluding the possibility of the existence of the fcc phase in the inner core if the simple linear extrapolation of the two-phase region is applied. The pressure and temperature dependences of the c/a axial ratio of the hcp phase in Fe–9.7 wt% Ni are generally consistent with those in pure Fe, suggesting that Ni has minor effects on the c/a ratio.  相似文献   

Groundwater geochemistry of a nitrate-contaminated agricultural site   总被引：1，自引：0，他引：1  

Hiroki Amano  Kei Nakagawa  Ronny Berndtsson 《Environmental Earth Sciences》2016,75(15):1145

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Decision-theoretic sensitivity analysis for reservoir development under uncertainty using multilevel quasi-Monte Carlo methods     

Takashi Goda  Daisuke Murakami  Kei Tanaka  Kozo Sato 《Computational Geosciences》2018,22(4):1009-1020

At various stages of petroleum reservoir development, we encounter a large degree of geological uncertainty under which a rational decision has to be made. In order to identify which parameter or group of parameters significantly affects the output of a decision model, we investigate decision-theoretic sensitivity analysis and its computational issues in this paper. In particular, we employ the so-called expected value of partial perfect information (EVPPI) as a sensitivity index and apply multilevel Monte Carlo (MLMC) methods to efficient estimation of EVPPI. In a recent paper by Giles and Goda, an antithetic MLMC estimator for EVPPI is proposed and its variance analysis is conducted under some assumptions on a decision model. In this paper, for an improvement on the performance of the MLMC estimator, we incorporate randomized quasi-Monte Carlo methods within the inner sampling, which results in an multilevel quasi-Monte Carlo (MLQMC) estimator. We apply both the antithetic MLMC and MLQMC estimators to a simple waterflooding decision problem under uncertainty on absolute permeability and relative permeability curves. Through numerical experiments, we compare the performances of the MLMC and MLQMC estimators and confirm a significant advantage of the MLQMC estimator.  相似文献