Benthic Front and the Yamato Basin Bottom Water in the Japan Sea     

Tomoharu?SenjyuEmail author  Yutaka?Isoda  Takafumi?Aramaki  Shigeyoshi?Otosaka  Shinzo?Fujio  Daigo?Yanagimoto  Takashi?Suzuki  Kenshi?Kuma  Kosuke?Mori 《Journal of Oceanography》2005,61(6):1047-1058

Hydrographic observations have revealed detailed structure of the Bottom Water in the Japan Sea. The Yamato Basin Bottom Water (YBBW) exhibits higher temperatures and lower dissolved oxygen concentrations than those found in the Japan Basin Bottom Water (JBBW). Both Bottom Waters meet around the boundary region between the Yamato and the Japan Basins, forming a clear benthic front. The structure of the benthic front suggests an estuary-like water exchange between both Basins, with the inflow from the Japan Basin passing under the outflow from the Yamato Basin. It is inferred from the property distributions that the JBBW flowing into the Yamato Basin is entrained by the cyclonic circulation in the basin, and modified to become the YBBW. Vertical diffusion and thermal balance in the YBBW are examined using a box model. The results show that the effect of geothermal heating has about 70% of the magnitude of the vertical thermal diffusion and both terms cancel the advection term of the cold JBBW from the Japan Basin. The box model also estimates the turnover time and vertical diffusivity for the YBBW as 9.1 years and 3.4 × 10⁻³ m²s^{− 1}, respectively.  相似文献   

Stokes' expansion of internal deep water waves to the fifth order     

Yoshinobu Tsuji  Yutaka Nagata 《Journal of Oceanography》1973,29(2):61-69

Stokes' expansion is applied to the internal waves of finite amplitude, which propagate on the interface between two layers of infinite thickness. Stream function, wave profile, phase velocity and mass transport velocity are given in the fifth order approximation. It is shown that (a) phase velocity increases with increase of wave steepness, (b) mass transport appears in the direction of the wave propagation in both layers as in the case of the surface waves, and (c) when the density difference is very small, the wave profile is flattened not only at the troughs but also at the crests.  相似文献   

Water wedge advancing along the interface between two homogeneous layers     

Akira Masuda  Yutaka Nagata 《Journal of Oceanography》1974,30(6):289-297

The behavior of the water wedge advancing along the interface between two homogeneous layers is investigated experimentally. The horizontally intruding wedge is strongly influenced by the detailed structure of the interface, even when the interface is sharp enough for its position to be visually determined. Within our experimental range, the intrusion velocity is very slow and depends on the thickness of the interface along which the water wedge intrudes. The wedge length is well described by the relation which is derived using an analogy to the linearly stratified case. The results could be useful for understanding the generation mechanism of the oceanic microstructure.  相似文献   

239, 240Pu,137Cs and90Sr in the central North Pacific     

Yutaka Nagaya  Kiyoshi Nakamura 《Journal of Oceanography》1984,40(6):416-424

^{239, 240}Pu,¹³⁷Cs and⁹⁰Sr concentrations were determined in sea waters from the central and western North Pacific in 1980 and 1982. The results are consistent with those reported earlier for North Pacific waters. The profiles of⁹⁰Sr and¹³⁷Cs show a monotonic decrease with depth, whilst^{239, 240}Pu shows a distinct subsurface maximum at a depth between 400 and 1,000 m. The calculated inventories of these nuclides significantly exceed the global mean fallout inputs for these latitudes. This may be due to local fallout input to the ocean at times of large-scale nuclear weapon tests in the equatorial North Pacific. The existence of measurable amounts of¹³⁷Cs and^{239, 240}Pu in deep waters suggests that these nuclides are transported by sinking particulate matter from the surface to the deep ocean.  相似文献   

Reconstruction of pH in the Surface Seawater over the North Pacific Basin for All Seasons Using Temperature and Chlorophyll-<Emphasis Type="Italic">a</Emphasis>     

Yoshiyuki?NakanoEmail author  Yutaka?W.?Watanabe 《Journal of Oceanography》2005,61(4):673-680

We found a simple function of pH that relates to sea surface temperature (SST, K) and chlorophyll-a (Chl, µg l⁻¹) using measured surface seawater pH, SST and Chl data sets over the North Pacific: pH (total hydrogen scale at 2°C) = 0.01325 SST − 0.0253 Chl + 4.150 (R² = 0.95, p < 0.0001, n = 483). Moreover, evaluating the seasonal variation of pH based on this algorithm, we compared the measured pH with the predicted pH at the observational time series stations in subpolar and subtropical regions. The average of ΔpH (measured - predicted, n = 52) was 0.006 ± 0.022 pH. Therefore, the combination of SST and Chl can allow us to determine the spatiotemporal distribution of pH over the North Pacific. Using the climatological data sets of SST and Chl with our pH algorithms, we have described the seasonal distributions of pH at 25°C (pH₍₂₅₎) and pH in situ temperature (pH_(T)) over the North Pacific surface water.  相似文献   

Spatiotemporal Decreases of Nutrients and Chlorophyll-a in the Surface Mixed Layer of the Western North Pacific from 1971 to 2000     

Yutaka?W.?WatanabeEmail author  Hiroshi?Ishida  Toshiya?Nakano  Naoki?Nagai 《Journal of Oceanography》2005,61(6):1011-1016

Using time series of hydrographic data in the wintertime and summertime obtained along 137°E from 1971 to 2000, we found that the average contents of nutrients in the surface mixed layer showed linear decreasing trends of 0.001∼0.004 μmol-PO₄ l⁻¹ yr⁻¹ and 0.01∼0.04 μmol-NO₃ l⁻¹ yr⁻¹ with the decrease of density. The water column Chl-a (CHL) and the net community production (NCP) had also declined by 0.27∼0.48 mg-Chl m⁻² yr⁻¹ and 0.08∼0.47 g-C-NCP m⁻² yr⁻¹ with a clear oscillation of 20.8±0.8 years. These changes showed a strong negative correlation with the Pacific Decadal Oscillation Index (PDO) with a time lag of 2 years (R = 0.89 ± 0.02). Considering the recent significant decrease of O₂ over the North Pacific subsurface water, these findings suggest that the long-term decreasing trend of surface-deep water mixing has caused the decrease of marine biological activity in the surface mixed layer with a bidecadal oscillation over the western North Pacific.  相似文献   

Evaluation of ecotoxicological effects of endocrine disrupters during a four-year survey of the Mediterranean population of swordfish (Xiphias gladius)     

M. Cristina Fossi  Silvia Casini  Letizia Marsili  Stefania Ancora  Gabriele Mori  Giovanni Neri  Teresa Romeo  Antonella Ausili 《Marine environmental research》2004,58(2-5):425

In this project we investigated the ecotoxicological effects of endocrine disrupters in a four-year survey of the Mediterranean population of swordfish (Xiphias gladius). In the Mediterranean environment, top predators, such as swordfish, accumulate high concentrations of polyhalogenated aromatic hydrocarbons (PHAHs) and toxic metals, potentially incurring high toxicological risk. The effects of organochlorines and trace elements (Hg, Cd and Pb) in 192 swordfish specimens, caught in the Strait of Messina, Sicily, Italy, were investigated using vitellogenin (Vtg), zona radiata proteins (Zrp) and CYP1A (BPMO, EROD) activities. Vtg and Zrp were found to be dramatically induced in some adult male specimens, suggesting that this species is highly exposed to estrogens in the Mediterranean Sea. A role of organochlorines in this induction phenomenon is suggested by the statistically significant correlations between Zrp in plasma and PCB concentrations in muscle (p<0.032) and Vtg in plasma and PCB concentrations in liver (p<0.034) of male specimens. Levels of trace elements in liver were in the following ranges: Hg 1–22, Cd 1–28 and Pb 0–1.6 ppm d.w. These data indicate potential reproductive alterations in large pelagic fish and suggest the need for continuous monitoring to avoid reductions in the population of this fish species of high commercial and ecological interest.  相似文献   

Evolutionary tracks of the terrestrial planets     

Takafumi Matsui  Yutaka Abe 《Earth, Moon, and Planets》1987,39(3):207-214

On the basis of the model proposed by Matsui and Abe, we will show that two major factors — distance from the Sun and the efficiency of retention of accretional energy — control the early evolution of the terrestrial planets. A diagram of accretional energy versus the optical depth of a proto-atmosphere provides a means to follow the evolutionary track of surface temperature of the terrestrial planets and an explanation for why the third planet in our solar system is an aqua-planet.  相似文献   

The importance of heating duration for Raman CM thermometry: evidence from contact metamorphism around the Great Whin Sill intrusion,UK          下载免费PDF全文

H. Mori  N. Mori  S. Wallis  R. Westaway  C. Annen 《Journal of Metamorphic Geology》2017,35(2):165-180

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Changes in the lower limit of mountain permafrost between 1973 and 2004 in the Khumbu Himal, the Nepal Himalayas   总被引：2，自引：0，他引：2  

Kotaro Fukui  Yoshiyuki Fujii  Yutaka Ageta  Katsuhiko Asahi 《Global and Planetary Change》2007,55(4):251-256

Because the Khumbu Himal of the Nepal Himalayas lacks long-term climate records from weather stations, mountain permafrost degradation serves as an important indicator of climate warming. In 1973, the permafrost lower limit was estimated to be 5200–5300 m above sea level (ASL) on southern-aspect slopes in this region. Using ground-temperature measurements, we examined the mountain permafrost lower limit on slopes with the same aspect in 2004. The results indicate that the permafrost lower limit was 5400–5500 m ASL in 2004. The permafrost lower limit was estimated to be 5400 to 5500 m on slopes with a southern aspect in the Khumbu Himal in 1991 using seismic reflection soundings. Thus, it is possible that the permafrost lower limit has risen 100–300 m between 1973 and 1991, followed by a stable limit of 5400 to 5500 m over the last decade. An increase in mean annual air temperature of approximately 0.2 to 0.4 °C from the 1970s to the 1990s has indicated a rise in the permafrost lower limit of 40 to 80 m at the Tibetan Plateau. The rise in the mountain permafrost lower limit in the Khumbu Himal exceeds that of the Tibetan Plateau, suggesting the possibility of greater climate warming in the Khumbu Himal.  相似文献