Variation of the sea surface temperature distribution across the Kuroshio in the Tokara Strait     

Yutaka Nagata  Katsuichi Takeshita 《Journal of Oceanography》1985,41(4):244-258

Distribution of the sea surface temperature (SST) across the Kuroshio has been measured in the Tokara Strait by the Kagoshima Prefectural Experimental Fishery Station, using a thermometer installed on boardEmerald-Amami, a ferry that operates regularly between Kagoshima and Naha. The data from 1 October 1978 to 30 September 1981 were analyzed in this paper.A sharp temperature front is usually formed at the northern edge of the current zone of the Kuroshio, and its position is very variable and moves north and south between Satamisaki and Nakanoshima. The northward migration of the front can easily be traced, but the southward migration is obscure in many cases. Some of the southward migrations seem to be understood as arising from the alternate appearance of two different fronts, namely a weakening of the northern front and a strengthening of the southern front, which are associated with the double structure of the Kuroshio front. The temperature contrast across the Kuroshio front is very weak in August through October, and the phase of its seasonal variation lags a few months behind that of temperature itself. Transitions between the states with and without temperature contrast occur suddenly, though the transition times differ year by year. Periodical fluctuations with a period of several tens of days are often observed in the migration region of the Kuroshio front. The fluctuations sometimes look very periodical within limited time periods, but the fluctuations are very changeable in nature from year to year.The results show that continuous observation of the SST distribution across the Tokara Strait yields a good tool for monitoring fluctuations of the Kuroshio path and the occurrence of the Ohsumi Branch Current, at least in the season when a large horizontal temperature contrast exists.  相似文献   

Variability of the sea surface temperature obtained by the statistical analysis of AVHRR imagery     

Yutaka Isoda  Sei-ichi Saitoh 《Journal of Oceanography》1988,44(2):52-59

A simple statistical method based on arithmetic mean and corresponding variance is proposed for analysis of a time series of NOAA-8 satellite Advanced Very High Resolution Radiometer (AVHRR) images. We focused on the characteristics of temporal and spatial variabilities of sea surface temperature depending on mesh sizes used for the statistics. By applying this method to several images of the south Japan Sea in spring of 1984, we could clarify some natures of eddies which cannot be recognized only by one image. They include life time and spatial scale of eddies.  相似文献   

Effects of wave breaking on wave statistics for deep-water random wave train     

Nobuhito Mori   《Ocean Engineering》2003,30(2):658-220

The experimental studies of the breaking effects on wave statistics for deep-water random waves are presented. It is especially focused on the behavior of kurtosis of surface elevations due to wave breaking. Wave breaking suppresses the maximum limit of kurtosis of the surface elevation, although skewness depends on characteristic wave steepness. The mean instantaneous wave steepness of breaking waves defined using the zero-down-crossing method was much lower than expected from the Stokes waves.  相似文献   

Seasonal Variations in the Sea off Sanriku Coast, Japan     

Sachiko Oguma  Toru Suzuki  Yutaka Nagata 《Journal of Oceanography》2002,58(6):825-835

The temperature and salinity data obtained by the Iwate Fisheries Technology Center for the 25-year period from 1971 to 1995 were analyzed to clarify the seasonal variations in the sea off Sanriku, Japan. The variations of three typical waters found in this region, the Tsugaru Current water, the Oyashio water, and the Kuroshio water are discussed in terms, of a T-S scatter diagram referring to the water mass classification proposed by Hanawa and Mitsudera (1986). The mean temperature and salinity fields averaged for each month show clear seasonal variation. Distributions of the Tsugaru Current water and the Oyashio water can barely be distinguished in the fields deeper than 200 m since the Tsugaru Current has a shallow structure; however, the fields at 100 m depth indicate remarkable seasonal variation in the area of the Tsugaru Current. At 100 m depth, the temperature and salinity fronts between the Tsugaru Current water and the Oyashio water gradually disappear in January through April, appear again in May, then become clearest in September. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Biomarkers for endocrine disruptors in three species of Mediterranean large pelagic fish   总被引：2，自引：0，他引：2  

Fossi MC  Casini S  Marsili L  Neri G  Mori G  Ancora S  Moscatelli A  Ausili A  Notarbartolo-di-Sciara G 《Marine environmental research》2002,54(3-5):667-671

The hypothesis that Mediterranean top predator species, such as large pelagic fish, are potentially at risk due to endocrine disrupting chemicals (EDCs), is investigated. The potential estrogenic effects of PHAHs in three fish species of commercial interest, the top predators bluefin tuna (Thunnus thynnus thynnus), swordfish (Xiphias gladius), and Mediterranean spearfish (Tetrapturus belone), were investigated using vitellogenin (Vtg), zona radiata proteins (Zrp) and mixed function oxidases (EROD, BPMO) as diagnostic tools. High induction of Vtg and Zrp was detected by western blot and ELISA techniques in adult males of X. gladius and T. thynnus thynnus, suggesting that these species are at high toxicological risk in the Mediterranean sea. Comparison of BPMO and EROD activities in the three species indicated, both in male and female, much higher MFO activity in bluefin tuna. This data suggests high exposure of this species to lipophilic xenobiotic contaminants in the Mediterranean environment.  相似文献   

90Sr and137Cs contents in the surface waters of the adjacent seas of Japan and the North Pacific during 1969 to 1973     

Yutaka Nagaya  Kiyoshi Nakamura 《Journal of Oceanography》1976,32(5):228-234

The concentrations of⁹⁰Sr and¹³⁷Cs, derived from the radioactive fallout, in the surface layers of the adjacent seas of Japan and the North Pacific were determined radiochemically during 1969 to 1973. The⁹⁰Sr and¹³⁷Cs concentrations in sea water decreased markedly with increase of the depth and below the depth of 1,000 m, the concentrations were approximately uniform. The distribution of⁹⁰Sr in the surface water of the North Pacific in spring of 1970 was approximately uniform, except two regions; rather large low-concentration region between 160°E and 170°W and relatively higher contamination area around 32°N and 146°W.  相似文献   

A Late Winter Hydrography in Hidaka Bay, South of Hokkaido, Japan     

Manabu Shimizu  Yutaka Isoda  Kazumi Baba 《Journal of Oceanography》2001,57(4):385-395

Hydrographic observations in Hidaka Bay, south of Hokkaido, Japan were carried out in late winter 1996 and 1997 to examine the spatial distributions and circulation features of two different water masses, i.e., Coastal Oyashio Water (COW) and Tsugaru Warm Water (TWW), and their modifications. It is known that COW is mostly composed of cold and low-salinity water of the melted drift ice coming from the Okhotsk Sea and flows into Hidaka Bay from winter to spring and TWW with high-salinity continuously supplies from the Tsugaru Strait to the North Pacific. Cold surface mixed layers (<26.2σ_θ, 0–100 m depth) were found mainly over the shelf slope, confirming that anti-clockwise flow of COW was formed. TWW was relatively high in salinity and low in potential vorticity, and had some patch-like water masses with a temperature and salinity maximum in the limited area in the further offshore at the deeper density levels of 26.6–26.8σ_θ. The fine structure of vertical temperature and salinity profiles appeared between TWW and COW is an indication of enhanced vertical mixing (double-diffusive mixing), as inferred from the estimated Turner angles. At a mouth of the Tsugaru Strait in late winter 1997, a significant thermohaline front between TWW and the modified COW was formed and a main path of TWW spreaded south along the Sanriku coast, probably as the bottom controlled flow. Hence, the patch-like TWW observed in late winter is isolated from the Tsugaru Warm Current and then rapidly modified due to a diapycnal mixing. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Shallow temperature inversions in the Pacific Ocean near Japan     

Yutaka Nagata 《Journal of Oceanography》1979,35(3-4):141-150

The statistical properties of shallow temperature inversions in the Pacific Ocean near Japan were investigated using data obtained from. BT observations. In the sea east of Honshu, the Kuroshio front forms the southern boundary of the area where temperature inversions are abundant. Though the occurrence frequency of the temperature inversion layers is very low in the sea south of Honshu, the path of the Kuroshio influences its regional distribution in this region also, and the high occurrence area shifts offshore when the large cold water mass is present off Enshu-nada. The magnitude of the inversion temperature differences in the sea south of Honshu is considerably smaller than that in the sea east of Honshu. The magnitude of inversion thickness has a clear tendency to increase from south to north in the sea east of Honshu, reflecting the higher occurrence frequency of large-scale thick inversion layers in the northern part under the influence of the sub-arctic water mass. The frequency distribution of the inversion thickness in each sub-region (1° square area) in the sea south of Honshu is very similar to that in the region just south of the Kuroshio front in the sea east of Honshu, suggesting that the inversion layers may be generated by similar mechanisms in the sea south of the Kuroshio front.  相似文献   

Environmental pollution and bio-politics: The epistemological constitution in Japan’s 1960s     

Masato Mori   《Geoforum》2008,39(3):1466-1479

This article examines the epistemological reconstitution in Japan—from Eisei (hygiene) to Kankyo (environment and ecology)—in the 1960s, particularly focusing on Yokkaichi city in the Mie prefecture that was infamous for environmental pollution. Post World War II, Yokkaichi port and its petrochemical industrial complexes were regarded as a symbol of Japan’s development. Referred to as ‘a million dollar night’s view’ for its ability to provide light the entire day, it played a central role in the country’s industrial reconstruction. Due to its reputation for ‘nature’-filled countryside, many enjoyed swimming at Yokkaichi despite the presence of the nearby industrial plants. Both these facts imply that people did not realize the risks posed by the dirtiness of the wastewater and the fumes emitted by the plants, an ignorance that may be traced back to the epistemic constitution of hygiene in Japan at the time. Since modernization, the government had adopted the idea of hygiene to control infectious and venereal diseases. The Department of Interior in 1873, and later, the Ministry of Health and Welfare in 1938 were also instituted to discipline human aesthetics through bio-politics. In the 1960s, when diseases of unknown origins began to appear and ‘scientific’ researches made the risks of wastewater and fumes visible, a new idea, Kankyo (which included but went beyond that of hygiene), was implemented to mitigate these risks. This transition saw the landscape of ‘a million dollar night’s view’ being transformed into a symbol of injustice and became a basis for grassroots political acts.  相似文献   

Temporal variability of sedimentation rates and mobile fauna inside and outside a gorgonian garden          下载免费PDF全文

Laura Valisano  Francesca Notari  Mario Mori  Carlo Cerrano 《Marine Ecology》2016,37(6):1303-1314

Paramuricea clavata (Cnidaria, Octocorallia) is an important ecosystem engineer of coralligenous assemblages increasingly threatened by anthropogenic activities and climate changes. As climate warming is predicted to continue in the coming years it is important to hypothesize future scenarios. Here we tested the influence of gorgonian colonies on sedimentation rates and vagile fauna trends, comparing sediments collected by traps inside and outside a gorgonian garden, in a coralligenous community of the Western Ligurian Sea, at 32 m depth, over a period of 1 year. The results indicated that sea fans created a sort of homeostatic effect on the surrounding habitat. We found evidence that where gorgonian colonies were present, the monthly fluctuations of sediments rate were lower than outside a garden. Gorgonian colonies also influenced the distribution of the associated vagile fauna; these organisms were generally more abundant inside than outside the garden. The data collected in this work appear to confirm the role of P. clavata as an ecosystem engineer, affecting biomass and variability of the surrounding habitat at both spatial and temporal scales.  相似文献