Influence of Kuroshio Flow on the Horizontal Distribution of North Pacific Intermediate Water in the Shikoku Basin     

Yoshihiko Sekine  Shingo Miyamoto 《Journal of Oceanography》2002,58(4):611-616

The influence of the Kuroshio flow on the horizontal distribution of North Pacific Intermediate Water (NPIW) in the Shikoku Basin is examined based upon observational data collected by the training vessel “Seisui-maru” of Mie University together with oceanographic data compiled by the Japan Oceanographic Data Center (JODC). Although it has been stated that the NPIW with salinity less than 34.2 psu had been confined to the south of the Kuroshio main axis along the PT (KJ) Line on the eastern side of the Izu Ridge, a similar tendency can be detected on the western side of the Izu Ridge. Namely, the NPIW on the southern side of the Kuroshio main axis in the Shihoku Basin does not indicate a tendency to go northward across the Kuroshio main axis without an increase in salinity of more than 34.2 psu. However, the JODC data show that less saline water (<34.2 psu) was present on the northern side of the Kuroshio main axis south of the Kii Peninsula in May 1992. Satellite observed sea surface temperature (SST) data suggested that the Kuroshio approaches the Kii Peninsula after forming a small meander off Kyushu and some intrusions of the NPIW into the northern coastal side of the Kuroshio main axis occurred in this period. It is concluded that intrusion of the NPIW with salinity less than 34.2 psu to the northern coastal side through the Kuroshio main axis occurred during the decay period of the small meander path in May 1992. Based on these observational results, the source of the salinity minimum water on the northern coastal side of the Kuroshio main axis is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Hydrographic structure of the Kuroshio large meander-cold water mass region down to the deeper layers of the ocean     

Haruo Ishii  Yoshihiko Sekine  Yoshiaki Toba 《Journal of Oceanography》1983,39(5):240-250

The hydrographic structure of the region of large meander of the Kuroshio and the large cold water mass, which were formed in 1975, was observed down to the ocean bottom, during three cruises of the R/VHakuho Maru in September 1975, September 1976, and December 1977. The analysis of observed data indicates the following common features: the horizontal gradient of the specific volume anomaly exists down to a 3,500 db surface, corresponding to the existence of baroclinic geostrophic current down to this depth. These facts demonstrate that the current of the Kuroshio is not confined to the upper layer during periods of existence of the large meander. On a T-S diagram, the Kuroshio water and the water in the large cold water mass can be discriminated down to a 5°C surface, but there is evidence of mixing due to conspicuous interleaving between the two water masses, near the thermocline. Below the thermocline, water types defined by points on the T-S diagram can be traced from a deeper level in the Kuroshio water to a shallower level in the cold water mass, indicating that in the deeper layers the Kuroshio water continues to be uplifted toward the center of the cold water mass. The same inference is also obtained from the distribution of dissolved oxygen.  相似文献   

Kinematics of overturning solitary waves and their relations to breaker types     

Takashi Yasuda  Hidemi Mutsuda  Natsuki Mizutani 《Coastal Engineering》1997,29(3-4)

Numerical simulations using a full-nonlinear BIM (Boundary Integral Method) potential-theory wave model are carried out to study the internal velocity and acceleration fields of an solitary wave overturning on a reef with vertical face (submerged breakwater) and their relation to breaker type. The simulations make it clear that the jet size normalized by the incident wave height is uniquely governed by the crown height of the reef, while the jet shape is similar and independent of the size. Further, they reveal that the overall internal kinematics of overturning waves is clearly related to the jet size. As the jet size increases and the breaker type changes from spilling to plunging, the kinematics thus become increasingly different from those of steady waves. Water particles with the greatest velocities or accelerations within the wave converge towards the jet. After the breaking, both of the velocities and accelerations almost simultaneously reach extreme values near locations beneath the jet. Some of the extreme values are closely related to the breaker type and can be uniquely determined by substituting the breaker type index into the regression equations suggested here.  相似文献   

Topographic effect of a marine ridge on the spin-down of a cyclonic eddy with mean flow     

Yoshihiko Sekine 《Journal of Oceanography》1993,49(5):593-606

The topographic effect of a meridional marine ridge on the spin-down of a cyclonic eddy, which is embedded in a zonal mean flow, is examined by use of a two layer numerical model. It is shown that the cyclonic eddy initially given on the eastern flank of the marine ridge decays in a short time. This result is common to all cases with the different volume transports of the mean flow (3070 Sv) and of the cyclonic eddy (1535 Sv). During the decay process, the cyclonic eddy shifts mainly northward into the shallower region, which is different from the dominant westward shift of the isolated cyclonic eddy. If the mean flow across over the marine ridge at the more northern latitude, the cyclonic eddy spins down more rapidly. A mean flow shifts zonal or south-eastward over a western side of the ridge, while it deflects north-eastward over an eastern side. The deflection angle of mean flow over the ridge depends on the intensity of lower layer velocity and density stratification. It is suggested that the topographic effect of the meridional marine ridge on the cyclonic eddy with mean flow is influenced both by the global phenomena that controls the inclination of the mean flow from zonal direction and by the local phenomena that controls the intensity of the topographic effect of the marine ridge.  相似文献   

Why does the Sea Level Difference between Kushimoto and Uragami Show Periods of Large Meander and Non-Large Meander Paths of the Kuroshio South of Japan?     

Yoshihiko Sekine  Kohichi Fujita 《Journal of Oceanography》1999,55(1):43-51

The sea level difference between Kushimoto and Uragami, located to the west and east of the southern tip of the Kii Peninsula, is relatively large in periods of non-large meander path (nLMP) of the Kuroshio south of Japan in comparison with periods of large meander path (LMP). Based on this clear relationship, the sea level difference between Kushimoto and Uragami has been used as an index showing the periods of nLMP and those of LMP of the Kuroshio south of Japan. It has been pointed out that warm and saline Kuroshio water, separated from the main path of the Kuroshio, has a tendency to approach the western area off Kii Peninsula to off Muroto Peninsula in periods of nLMP, while it approaches the eastern area off Kii Peninsula to Omae-zaki in periods of LMP. On the basis of this observational evidences, the dynamic background underlaying the well-known relationship between the Kuroshio path and the sea level difference between Kushimoto and Uragami is examined in the present study, using the temperature and salinity data observed by Wakayama Prefectural Fisheries Experimental Station and Fisheries Research Institute of Mie. It is shown that deviations in vertically integrated specific volume off Kushimoto and Uragami almost equal deviations in observed sea level at Kushimoto and Uragami, respectively. It is also shown that the difference in vertically integrated specific volume between off Kushimoto and off Uragami almost equals the difference in observed sea level between Kushimoto and Uragami. As for the Kuroshio water, the high-temperature contribution is predominant for its specific volume rather than that of high salinity, which yields thermal expansion in comparison with coastal water. Because the difference in vertically integrated specific volume between off Kushimoto and off Uragami almost equals the difference in observed sea level between Kushimoto and Uragami, it is concluded that the relationship between the Kuroshio path and sea level difference between Kushimoto and Uragami is caused by the different approaching of the warm Kuroshio water between in nLMP periods and in LMP periods.  相似文献   

Regeneration dynamics of iron and nutrients from bay sediment into bottom water of Funka Bay,Japan     

Nanako Hioki  Kenshi Kuma  Yuichiroh Morita  Daichi Miura  Atsushi Ooki  Seiji Tanaka  Hiroji Onishi  Tetsuya Takatsu  Naoto Kobayashi  Yoshihiko Kamei 《Journal of Oceanography》2015,71(6):703-714

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A Subaru/Suprime-Cam wide-field survey of globular cluster populations around M87 – II. Colour and spatial distribution     

Naoyuki Tamura †  Ray M. Sharples  Nobuo Arimoto  Masato Onodera  Kouji Ohta  Yoshihiko Yamada 《Monthly notices of the Royal Astronomical Society》2006,373(2):601-612

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Effects of diurnal cycle of surface heat flux on wind-driven flow     

Yoshihiko Ide  Yutaka Yoshikawa 《Journal of Oceanography》2016,72(2):263-280

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A numerical experiment on the anomalous southward intrusion of the Oyashio east of Japan     

Yoshihiko Sekine 《Journal of Oceanography》1988,44(2):60-67

In recent years, anomalous southward intrusions of the Oyashio have been observed frequently from winter to late spring. A barotropic model is used to see the occurrence of the Oyashio intrusion, with special reference to a short time lag between the change in the wind stress in midwinter and the occurrence of the Oyashio intrusion generally in spring of the same year. It is shown that the barotropic response of the ocean to the change in wind stress is fast, and its representative time scale is about 50 days at most. The southward shift of the Oyashio and the subarctic circulation are simulated quantitatively, when the imposed wind stress is changed from the mean wind stress prior to no Oyashio intrusion to that prior to the Oyashio intrusion. It is suggested that the southward intrusion of the Oyashio is a phenomenon connected with the global change in atmospheric circulation.  相似文献   

Spin-up and spin-down processes of the large cold water mass of the Kuroshio south of Japan     

Yoshihiko Sekine  Haruo Ishii  Yoshiaki Toba 《Journal of Oceanography》1985,41(4):207-212

Time variation of the cold water mass of the Kuroshio south of Japan, which was formed in August 1975 and disappeared in August 1980, is studied. Its lifecycle includes several repetitions of spin-down and spin-up processes. The spin-down (or the spin-up) process is accompanied by warming (cooling) of the cold water mass and descending (ascending) motion of the inner water. Expansion of the cold water area is also associated with the spin-up period while shrinking occurs in the spin-down period. The rate of spin-down of the cold water mass is approximately equal to that of the Gulf Stream rings. The spin-up process is not observed in the Gulf Stream rings and the longer lifetime of the cold water mass off Japan, in comparison with the Gulf Stream rings, is due to the existence of the spin-up periods. The spin-up process tends to occur in late spring to summer, and it seems to be related to the seasonal variation in intensity of the Kuroshio.  相似文献