The extinction coefficients in mid- and farinfrared of silicate and iron-oxide minerals of interest for astronomical observations     

Chiyoe Koike  Hiroichi Hasegawa  Noriaki Asada  Takeshi Hattori 《Astrophysics and Space Science》1981,79(1):77-85

Extinction measurements were made for some silicate and iron-oxide mineral grains in mid- and far-infrared region. For far-infrared region, high temperature magnesium silicates such as olivine and pyroxenes show the absorption spectra of steep dependence as ^–3 ( being the wavelength) with some peak structure, but the spectrum of magnetite shows ^–1 dependence.  相似文献   

Nutrient regeneration at bottom after a massive spring bloom in a subarctic coastal environment,Funka Bay,Japan     

Isao Kudo  Takeshi Yoshimura  Choon-Weng Lee  Mitsuru Yanada  Yoshiaki Maita 《Journal of Oceanography》2007,63(5):791-801

Nutrient regeneration and oxygen consumption after a spring bloom in Funka Bay were studied on monthly survey cruises from February to November 1998 and from March to December 1999. A high concentration of ammonium (more than 4 μmol l⁻¹) was observed near the bottom (80–90 m) after April. Phosphate and silicate gradually accumulated and dissolved oxygen decreased in the same layer. Salinity near the bottom did not change until summer, leading to the presumption that the system in this layer is semi-closed, so regenerated nutrients were preserved until September. Nitrification due to the oxidation of ammonium to nitrate was observed after June. Nitrite, an intermediate product, was detected at 4–7 μmol L⁻¹ in June and July 1999. Assuming that decomposition is a first order reaction, the rate constant for decomposition of organic nitrogen was determined to be 0.014 and 0.008 d⁻¹ in 1998 and 1999, respectively. The ammonium oxidation rate increased rapidly when the ambient ammonium concentration exceeded 5 μmol L⁻¹. We also performed a budget calculation for the regeneration process. The total amount of N regenerated in the whole water column was 287.4 mmol N m⁻² in 4 months, which is equal to 22.8 gC m⁻², assuming the Redfield C to N ratio. This is 34% of the primary production during the spring bloom and is comparable to the export production of 25 gC m⁻² measured by a sediment trap at 60 m (Miyake et al., 1998).  相似文献   

Dynamics of elastically moored floating objects     

Tokuo Yamamoto  Akinori Yoshida  Takeshi Ijima 《Applied Ocean Research》1980,2(2):85-92

The two-dimensional problem of wave transformation by, and motions of, moored floating objects is solved numerically as a boundary value problem by direct use of Green's identity formula for a potential function. The cross-sectional shape of the floating object, the bottom configuration and the mooring arrangements may be all arbitrary. For a given incident wave, the three modes of body motion, the wave system and mooring forces are all solved at the same time. A laboratory experiment is conducted to verify the theory. Generally good agreements between the theory and experiments are obtained as long as the viscous damping due to flow separation is small. A numerical experiment indicates that a conventional sluck mooring is to worsen the wave attenuation by a floating breakwater and that a properly arranged elastic mooring can considerably improve the wave attenuation by a floating breakwater.  相似文献   

Origin and decomposition of sinking particulate organic matter in the deep water column inferred from the vertical distributions of its δN, δ and δ     

Takeshi Nakatsuka  Nobuhiko Handa  Naomi Harada  Tatsuhiro Sugimoto  Shigemi Imaizumi   《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12)

Sinking particles were analyzed for their nitrogen isotopic ratio δ¹⁵N) of total particulate nitrogen (PN), stable carbon isotopic ratio (δ¹³C) and radioactive isotopic ratio (δ¹⁴C) of total particulate organic carbon (POC), at three different latitudinal (temperate, subpolar and equatorial) and geomorphological (trench, proximal abyssal plain and distal abyssal plain) sites in the western North Pacific Ocean using year-long time series sediment trap systems, to clarify the common vertical trends of the isotopic signals in deep water columns. Although the δ¹⁵N and δ¹³C values of sinking particulate organic matter (POM) were partly affected by the resuspension of sedimentary POM from the sea floor, especially in the trench, the changes in δ¹⁵N and δ¹³C values owing to the resuspension could be corrected by calculation of the isotopic mass balance from δ¹⁴C of sinking POC. After this correction, common downward decreasing trends in δ¹⁵N and δ¹³C values were obtained in the deep water columns, irrespective of the latitudes and depths. These coincidental isotopic signals between δ¹⁵N and δ¹³C values provide new constraints for the decomposition process of sinking POM, such as the preferential degradation of ¹⁵N- and ¹³C-rich compounds and the successive re-formation of the sinking particles by higher trophic level organisms in the deep water column.  相似文献   

Baroclinic eddies south of Cheju Island in the East China Sea   总被引：3，自引：0，他引：3  

Tetsuo Yanagi  Takanori Shimizu  Takeshi Matsuno 《Journal of Oceanography》1996,52(6):763-769

The detailed structures of baroclinic eddies, that is, an anticlockwise circulation in the upper layer and a clockwise one in the lower layer south of Cheju Island in the East China Sea have been revealed by intensive field observation. Such baroclinic eddies are accompanied by the southward spreading of the Yellow Sea Bottom Cold Water.  相似文献   

A nonlinear wave profile correction of the diffraction of a wave by a long breakwater: Fixed point approach     

T.S. Jang  S.H. Kwon  Takeshi Kinoshita  B.J. Kim 《Ocean Engineering》2007,34(3-4):500-509

The authors of the present paper have suggested an iterative scheme to calculate the nonlinear wave profiles [Jang and Kwon, 2005. Application of nonlinear iteration scheme to the nonlinear water wave problem: Stokes wave. Ocean Engineering 32, 1862–1872]. The scheme was shown to be good for estimating nonlinear wave profiles. In the study, the iterative scheme is applied to the wave-diffraction problem by a long breakwater to calculate a diffracted wave by the breakwater. The iterative solution of diffraction was compared with the linear solution of Sommerfeld, 1896. [Mathematische Theoried der Diffraction. Mathematical Annals 47, 317–374]. For a small wave slope, the two solutions were in good agreement. However, the scheme enabled us to observe the nonlinear behaviors of a beating phenomenon and of wave profile such as Stokes’ wave for a relatively large wave slope: as the wave slope becomes larger, we can examine the nonlinear wave characteristics of the actual shapes of waves, i.e., the crests are steeper and the troughs are flatter.  相似文献   

Interannual salinity variations in the Tsushima Strait and its relation to the Changjiang discharge   总被引：2，自引：0，他引：2  

Tomoharu Senjyu  Hirofumi Enomoto  Takeshi Matsuno  Sigeaki Matsui 《Journal of Oceanography》2006,62(5):681-692

Interannual salinity variations in the Tsushima Strait are investigated on the basis of historical hydrographic data. The EOF analysis revealed that the most dominant mode is the in-phase salinity variation between the eastern and western channels. The time coefficients of the EOF first mode in summer show a negative correlation with the Changjiang discharge, which indicates that salinity in the Tsushima Strait tends to decrease over summer, related to a large discharge of the Changjiang. The eigenvectors of the first mode are larger in the eastern channel than those in the western channel, though the low salinity water mainly flows through the western channel. This is because the low salinity water spreads into the eastern channel as well as the western channel over summers with a large discharge of the Changjiang. The out-of-phase salinity variation between the channels is extracted as the EOF second mode; this is the predominant variation in the western channel. The time coefficients of the second mode in summer show no significant correlations to the volume transports through the western channel and the transport differences between channels. A relationship between the EOF second mode and variations in the wind stress over the East China Sea is suggested.  相似文献   

An Ecosystem Model Including Nitrogen Isotopes: Perspectives on a Study of the Marine Nitrogen Cycle     

Chisato?YoshikawaEmail author  Yasuhiro?Yamanaka  Takeshi?Nakatsuka 《Journal of Oceanography》2005,61(5):921-942

We have developed an ecosystem model including two nitrogen isotopes (¹⁴N and ¹⁵N), and validated this model using an actual data set. A study of nitrogen isotopic ratios (δ¹⁵N) using a marine ecosystem model is thought to be most helpful in quantitatively understanding the marine nitrogen cycle. Moreover, the model study may indicate a new potential of δ¹⁵N as a tracer. This model has six compartments: phytoplankton, zooplankton, particulate organic nitrogen, dissolved organic nitrogen, nitrate and ammonium in a two-box model, and has biological processes with/without isotopic fractionation. We have applied this model to the Sea of Okhotsk and successfully reproduced the δ¹⁵N of nitrate measured in seawater and the seasonal variations in δ¹⁵N of sinking particles obtained from sediment trap experiments. Simulated δ¹⁵N of phytoplankton are determined by δ ¹⁵N of nitrate and ammonium, and the nitrogen f-ratio, defined as the ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation. Detailed considerations of biological processes in the spring and autumn blooms have demonstrated that there is a significant difference between simulated δ¹⁵N values of phytoplankton, which assimilates only nitrate, and only ammonium, respectively. We suggest that observations of δ ¹⁵N values of phytoplankton, nitrate and ammonium in the spring and autumn blooms may indicate the ratios of nutrient selectivity by phytoplankton. In winter, most of the simulated biogeochemical fluxes decrease rapidly, but nitrification flux decreases much more slowly than the other biogeochemical fluxes. Therefore, simulated δ¹⁵N values and concentrations of ammonium reflect almost only nitrification. We suggest that the nitrification rate can be parameterized with observations of δ¹⁵N of ammonium in winter and a sensitive study varying the parameter of nitrification rate.  相似文献   

Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core,and selected auxiliary records     

Mike Walker  Sigfus Johnsen  Sune Olander Rasmussen  Trevor Popp  Jørgen‐Peder Steffensen  Phil Gibbard  Wim Hoek  John Lowe  John Andrews  Svante Björck  Les C. Cwynar  Konrad Hughen  Peter Kershaw  Bernd Kromer  Thomas Litt  David J. Lowe  Takeshi Nakagawa  Rewi Newnham  Jakob Schwander 《第四纪科学杂志》2009,24(1):3-17

The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene–Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in δ¹⁸O, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi‐parameter annual layer counting provides an age of 11 700 calendar yr b2 k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene–Holocene boundary have also been recognised. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Reply to comment on ‘Yamada H,Nakamura F,Watanabe Y,Murakami M and Nogami T. 2005. Measuring hydraulic permeability in a streambed using the packer test. Hydrological Processes 19: 2507–2524’     

Hiroyuki Yamada  Futoshi Nakamura  Yasuharu Watanabe  Marie Murakami  Takeshi Nogami 《水文研究》2008,22(17):3545-3545

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