Comparison of the seven large meanders of the Kuroshio     

Sun Xiangping  Wang Yuanpei  Kaneko Ikmo 《海洋学报(英文版)》1992,11(2):189-204

In this paper, a comparison among the seven large meanders of the Kuroshio is made in order to probe into their similarity and differences. The major results are described as follows.1. Although the three phases for the seven large meanders such as their formations, maturity, as well as decline are very similar to one another, each meander has its own trivial difference in detail.2.The paths of the first six large meanders in the mature phase may be classified into ten types: U1, V1, U2, V2, U1', V1', U2', V2',φ and W.3.The seven large meanders may be grouped into two patterns, i. e. , pattern Ⅰ and pattern Ⅱ. Pattern Ⅰ includes the first and the fourth large meanders, and pattern Ⅱ includes the rest of the above meanders.4. Four standards for identifying the large meanders of the Kuroshio are put forward.  相似文献   

Velocity structures and transports of the Kuroshio and the Ryukyu current during fall of 2000 estimated by an inverse technique   总被引：7，自引：0，他引：7  

Xiao-Hua Zhu  Jae-Hun Park  Ikuo Kaneko 《Journal of Oceanography》2006,62(4):587-596

An inverse calculation using hydrographic section data collected from October to December 2000 yields velocity structure and transports of the Kuroshio in the Okinawa Trough region of the East China Sea (ECS) and south of central Japan, and of the Ryukyu Current (RC) southeast of the Ryukyu Islands. The results show the Kuroshio flowing from the ECS, through the Tokara Strait (TK), with a subsurface maximum velocity of 89 cm s⁻¹ at 460 dbar. In a section (TI) southeast of Kyushu, a subsurface maximum velocity of 92 cm s⁻¹ at 250 dbar is found. The results also show the RC flowing over the continental slope from the region southeast of Okinawa (OS) to the region east of Amami-Ohshima (AE) with a subsurface maximum velocity of 67 cm s⁻¹ at 400 dbar, before joining the Kuroshio southeast of Kyushu (TI). The volume transport around the subsurface velocity maximum southeast of Kyushu (TI) balances well with the sum of those in TK and AE. The temperature-salinity relationships found around these velocity cores are very similar, indicating that the same water mass is involved. These results help demonstrate the joining of the RC with the Kuroshio southeast of Kyushu. The net volume transport of the Kuroshio south of central Japan is estimated to be 64∼79 Sv (1 Sv ≡ 10⁶ m³s⁻¹), of which 27 Sv are supplied by the Kuroshio from the ECS and 13 Sv are supplied by the RC from OS. The balance (about 24∼39 Sv) is presumably supplied by the Kuroshio recirculation south of Shikoku, Japan.  相似文献   

Anomalous distribution of suspended matter and some chemical compositions in seawater near the seabed: Transport processes     

Masahiro Kajihara  Katsuhiko Matsunaga  Yoshiaki Maita 《Journal of Oceanography》1974,30(5):232-240

Vertical fine distributions of suspended matter and some chemical compositions in seawater were measured in the layer near the seabed. Distributions of organic suspended matter were almost uniform throughout the layer, but others were anomalous. However, with respect to their peak heights and distribution patterns, the tendency of profiles was the same on the whole. We suggested that these anomalous distributions were primarily caused by the destruction of the large flocculent particle on the seabed and by upward diffusion of disintegrated particles. The similarity of profiles between chemical compositions of dissolved substances and suspended matter of non-dissolved substances, was explained by assuming that pore water in the large particle was simultaneously transported with disintegrated particles after the destruction. An equation for the vertical distribution of suspended matter near the seabed was derived, provided that the rate of destruction of large flocculent particle was in proportion to the current velocity on the seabed. The equation represented the existence of the anomalous distribution, which was continuously changing its pattern. Measurements of vertical profiles of suspended matter showed almost the same tendency with the theory. From the characteristics of the theoretical equation, it was expected that the eddy diffusivity near the seabed was 1050 cm²/sec.  相似文献   

Mesoscale eddy effects on temporal variability of surface chlorophyll a in the Kuroshio Extension     

Shinya Kouketsu  Hitoshi Kaneko  Takeshi Okunishi  Kosei Sasaoka  Sachihiko Itoh  Ryuichiro Inoue  Hiromichi Ueno 《Journal of Oceanography》2016,72(3):439-451

We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow.  相似文献   

Fine-scale structure and mixing across the front between the Tsugaru Warm and Oyashio Currents in summer along the Sanriku Coast,east of Japan     

Sachihiko Itoh  Hitoshi Kaneko  Miho Ishizu  Daigo Yanagimoto  Takeshi Okunishi  Hajime Nishigaki  Kiyoshi Tanaka 《Journal of Oceanography》2016,72(1):23-37

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Temporal changes in the geographic distribution of two clam species <Emphasis Type="Italic">Meretrix lusoria</Emphasis> and <Emphasis Type="Italic">M. petechialis</Emphasis> along the coast of Japan and South Korea     

Shin’ichi Sato  Yoshitaka Kaneko  Hiroshi Torii  Jae-Sang Hong 《Ocean Science Journal》2016,51(3):455-463

The objectives of this study were to distinguish fossil specimens of Meretrix (Bivalvia, Veneridae) using discriminant score and multivariate analysis, and to examine temporal changes in the geographical distributions of M. lusoria and M. petechialis in Japan and South Korea. Fossil shells of Meretrix were collected from Miyagi, Fukui, Aichi and Kumamoto in Japan, and Gimhae, Seosan, Siheung and Ganghwa-do in South Korea. The outside of the right valve was photographed with a digital camera, and ten characteristics of the shell morphology, such as shell height and shell length, were measured using image analysis software and a digital slide caliper. The discriminant score and multivariate analysis of the shell morphology identified all of the examined fossils as M. lusoria, while living individuals collected from the western coast of South Korea were identified as M. petechialis. These results suggest that the fossil shells excavated from the western coast of South Korea are a different species from the living individuals collected from the same areas. Radioactive carbon isotopic results revealed that the ages of the four fossil shells collected from tidal flats in Ganghwa-do ranged between 3,270 ± 30 and 1,830 ± 30 Cal BP. These results suggest that M. lusoria inhabited the western coast of South Korea until at least 2,000 years ago, but was replaced by M. petechialis during the last 2,000 years. Therefore, we propose that either M. petechialis spats were introduced artificially, or planktonic larvae migrated naturally from China to the western coast of South Korea during the last 2,000 years.  相似文献   

Evaluation of radiation-damage halos in quartz by cathodoluminescence as a geochronological tool     

T. Okumura  H. Nishido  S. Toyoda  T. Kaneko  S. Kosugi  Y. Sawada  K. Komuro 《Quaternary Geochronology》2008,3(4):342-345

Detailed quantitative cathodoluminescence (CL) imaging analysis was carried out for radiation-damage halos observed by CL (CL halo) created in natural quartz by implantation of 4 MeV He⁺ ions. The band of CL halo was approximately 14 μm in width and was constant for any He⁺ ion dose. The width of the halo is consistent with the theoretical range of ⁴He ions in quartz. A quantitative response of CL intensity to He⁺ ion dose was obtained, leading to the application of CL halos to geodosimetrical use. The CL intensity increases exponentially in the luminescent band from the implantation surface to the inside, until it reaches a maximum at 14 μm depth, with a rapid decrease beyond this point. This result is as predicted by Bragg's law, although we find some differences between the CL intensity and the theoretical stopping power.  相似文献   

Moho depth variation beneath southwestern Japan revealed from the velocity structure based on receiver function inversion     

Katsuhiko Shiomi  Kazushige Obara  Haruo Sato   《Tectonophysics》2006,420(1-2):205

The Philippine Sea plate is subducting under the Eurasian plate beneath the Chugoku-Shikoku region, southwestern Japan. We have constructed depth contours for the continental and oceanic Mohos derived from the velocity structure based on receiver function inversion. Receiver functions were calculated using teleseismic waveforms recorded by the high-density seismograph network in southwestern Japan. In order to determine crustal velocity structure, we first improved the linearized time-domain receiver function inversion method. The continental Moho is relatively shallow ( 30 km) at the coastline of the Sea of Japan and at the Seto Inland Sea, and becomes deeper–greater than 40 km–around 35°N and 133.8°E. Near the Seto Inland Sea, a low-velocity layer of thickness 10 km lies under the continental Moho. This low-velocity layer corresponds to the subducting oceanic crust of the Philippine Sea plate. The oceanic Moho continues to descend from south to northwest and exhibits complicated ridge and valley features. The oceanic Moho runs around 25 km beneath the Pacific coast and 45 km beneath the Seto Inland Sea, and it extends to at least to 34.5°N. The depth variation of the Moho discontinuities is in good qualitative agreement with the concept of isostasy. From the configurations of both the continental and oceanic Mohos, we demonstrate that the continental lower crust and the subducting oceanic crust overlap beneath the southern and central part of Shikoku and that a mantle wedge may exist beneath the western and eastern part of Shikoku. The southern edge of the overlapping region coincides with the downdip limit of the slip area of a megathrust earthquake.  相似文献   

Long-term measurement of stream flow and salinity in a tidal river by the use of the fluvial acoustic tomography system     

Kiyosi Kawanisi  Mahdi Razaz  Arata Kaneko  Satoshi Watanabe 《Journal of Hydrology》2010,380(1-2):74-81

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Implementation of an optimized Cassegrain system for radio telescopes     

C. M. Holler †  R. E. Hills  M. E. Jones †  K. Grainge  T. Kaneko 《Monthly notices of the Royal Astronomical Society》2008,384(3):1207-1210

We present the antenna design for a radio interferometer, the Arcminute Microkelvin Imager, together with its beam pattern measurement. Our aim was to develop a low-cost system with high aperture efficiency and low ground spill across the frequency range 12–18 GHz. We use a modified Cassegrain system consisting of a commercially available paraboloidal primary mirror with a diameter of 3.7 m, and a shaped secondary mirror. The secondary mirror is oversized with respect to a ray optics design and has a surface that is bent towards the primary near its outer edge using a square term for the shaping. The antennas are simple to manufacture and therefore their cost is low. The design increased the antenna gain by approximately 10 per cent compared to a normal Cassegrain system while still maintaining low contamination from ground spill and using a simple design for the horn.  相似文献