Grain size,La/Yb and Th/Sc of settling particles in the western North Pacific: Evidence for lateral transport of small Asian loess     

Nobuhiro Maeda  Shinichiro Noriki  Hisashi Narita 《Journal of Oceanography》2007,63(5):803-812

To understand the transport process of lithogenic particles in the ocean, we measured the grain size distributions of lithogenic particles and measured the opal, La, Yb, Th, and Sc concentrations of the settling particles collected from time-series sediment traps at Sta. KNOT (44°N, 155°E, water depth 5320 m) from June 2002 to May 2004. The annual mean lithogenic particle flux observed at the lower sediment trap (5100 m) was twice as high as that at the upper sediment trap (770 m). The contribution of Asian loess estimated by the La/Yb and the Th/Sc ratios in the lower layer was greater than that in the upper layer. The fluxes of small lithogenic particles with sizes of 3–4 μm at the lower layer (5 to 65 mg/m²/day) were approximately four times larger than that at the upper layer (0.6 to 27 mg/m²/day). These results indicate that the horizontal addition of small particle sizes of Asian loess is a main factor in the increase of lithogenic particles at the lower layer. The temporal variations in the small lithogenic particle flux at the lower layer had a positive correlation with those at the upper layer (r = 0.71). The small lithogenic particle fluxes showed a strong positive correlation with the opal fluxes (r = 0.9). We therefore conclude that the small lithogenic particles were laterally transported and scavenged by the formation of aggregates with opal.  相似文献   

Anomalous Large Scavenging of 230Th and 231Pa Controlled by Particle Composition in the Northwestern North Pacific     

Hisashi Narita  Ryota Abe  Kazuhisa Tate  Young-Ill Kim  Koh Harada  Shizuo Tsunogai 《Journal of Oceanography》2003,59(5):739-750

We report the role of particle composition and lateral particle movement that influences the oceanic distribution of ²³¹Pa and ²³⁰Th. Settling particles were collected during sediment trap experiments. These and surface sediments were obtained from five stations along 38 to 44°N in the northwestern North Pacific. The high total mass flux and seasonal variations in the marginal area of the western North Pacific are controlled by the supply of lithogenic materials and primary productivity. The high content of the lithogenic material in the settling particles in this area contributes to ²³⁰Th_ex fluxes that exceed the local rate of supply. The lithogenic materials are important as a carrier of ²³⁰Th and contribute to the fractionation between ²³⁰Th and ²³¹Pa in the ocean, as the ²³¹Pa_ex/²³⁰Th_ex ratio in the settling particles decreases with increasing ²³²Th concentration. The ²³¹Pa_ex/²³⁰Th_ex ratio in the settling particles collected in the abyssal basin decreases with water depth, which indicates that lateral transport of the lithogenic particles from the marginal area and/or shallower depth plays an important role in determining the ²³¹Pa_ex/²³⁰Th_ex ratio in a population of settling particles and remineralization. This indicates that lateral redistribution of particles and sediment focusing influence the ²³¹Pa_ex/²³⁰Th_ex ratios in surface sediments. Thus, the observations reported here mean that the use of the sediment ²³¹Pa_ex/²³⁰Th_ex ratio as a paleoproductivity proxy will be problematic in the northwestern North Pacific. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The tsunami of 3 February 1605     

Hisashi Miyoshi  Kaname Satoh  Yoshinobu Tsuji 《Journal of Oceanography》1989,45(3):174-180

Whether the origins of the tsunami of 3 February 1605 were separated ones or a joined one, is one of the most important problems for Japanese society. When the marine knowledge has not been popularized, it has been considered that the damage pattern on Hachijo Island (including Kojima) was an important key to solving this question.It resembles the situation that the reports concerning the tsunami of 1 April 1946 were introduced to Japanese society under an internal disturbance just after the war, and we overlooked the most important consideration on the combination of tsunami and storm waves caused by the trade wind, and received this tsunami as an extraordinarily huge one.We studied the statistics of recent wind directions around Hachijo Island in January and February 1973, 1974, 1977, 1983, 1984, 1985, 1986 and 1987. And we believed that the probability was high that we could explain well that the damage pattern on Hachijo Island in 1605 was due to the combination of tsunami and storm waves caused by the monsoon.We need not, therefore, look back the damage pattern on Hachijo Island when we consider the fact that the necrologies of many temples in Shizuoka Prefecture record no death on 3 February 1605, proves to be the key to infer that the origins were separated ones.  相似文献   

The high frequency spectrum of wind-generated waves     

Hisashi Mitsuyasu  Tadao Honda 《Journal of Oceanography》1974,30(4):185-198

The high frequency part (10 Hz50 Hz) of the one-dimensional wave spectrum was measured in a wind-wave channel under accurately controlled conditions. The results are compared with the spectral forms for the capillary range that have been proposed recently byPierson andStacy (1973) andToba (1973). In a general sense, fairly good agreement is found between the present results and those ofPierson andStacy (1973) and ofToba (1973). The spectrum in the capillary range is clearly wind speed dependent, and the spectral density in that range increases with increasing wind speed.However, closer examination shows systematic deviations of the present results from those previously proposed, particularly for high speed winds.  相似文献   

A Transit of Venus Possibly Misinterpreted as an Unaided-Eye Sunspot Observation in China on 9 December 1874     

Hayakawa  Hisashi  Sôma  Mitsuru  Tanikawa  Kiyotaka  Willis  David M.  Wild  Matthew N.  Macdonald  Lee T.  Imada  Shinsuke  Hattori  Kentaro  Richard Stephenson  F. 《Solar physics》2019,294(9):1-13

Solar Physics - Large sunspots can be observed with the unaided eye under suitable atmospheric seeing conditions. Such observations are of particular value because the frequency of their appearance...  相似文献   

Historical Auroras in the 990s: Evidence of Great Magnetic Storms     

Hisashi Hayakawa  Harufumi Tamazawa  Yurina Uchiyama  Yusuke Ebihara  Hiroko Miyahara  Shunsuke Kosaka  Kiyomi Iwahashi  Hiroaki Isobe 《Solar physics》2017,292(1):12

A significant carbon-14 enhancement has recently been found in tree rings for the year 994, suggesting an extremely strong and brief cosmic ray flux event. The origin of this particular cosmic ray event has not been confirmed, but one possibility is that it might be of solar origin. Contemporary historical records of low-latitude auroras can be used as supporting evidence of intense solar activity around that time. We investigate previously reported as well as new records that have been found in contemporary observations from the 990s to determine potential auroras. Records of potential red auroras in late 992 and early 993 were found around the world, i.e. in the Korean Peninsula, Saxonian cities in modern Germany, and the Island of Ireland, suggesting the occurrence of an intense geomagnetic storm driven by solar activity.  相似文献   

Comparison of four ensemble methods combining regional climate simulations over Asia     

Jinming Feng  Dong-Kyou Lee  Congbin Fu  Jianping Tang  Yasuo Sato  Hisashi Kato  John L. Mcgregor  Kazuo Mabuchi 《Meteorology and Atmospheric Physics》2011,111(1-2):41-53

A number of uncertainties exist in climate simulation because the results of climate models are influenced by factors such as their dynamic framework, physical processes, initial and driving fields, and horizontal and vertical resolution. The uncertainties of the model results may be reduced, and the credibility can be improved by employing multi-model ensembles. In this paper, multi-model ensemble results using 10-year simulations of five regional climate models (RCMs) from December 1988 to November 1998 over Asia are presented and compared. The simulation results are derived from phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia. Using the methods of the arithmetic mean, the weighted mean, multivariate linear regression, and singular value decomposition, the ensembles for temperature, precipitation, and sea level pressure are carried out. The results show that the multi-RCM ensembles outperform the single RCMs in many aspects. Among the four ensemble methods used, the multivariate linear regression, based on the minimization of the root mean square errors, significantly improved the ensemble results. With regard to the spatial distribution of the mean climate, the ensemble result for temperature was better than that for precipitation. With an increasing number of models used in the ensembles, the ensemble results were more accurate. Therefore, a multi-model ensemble is an efficient approach to improve the results of regional climate simulations.  相似文献   

Crustal anorthosite formation by deep-seated hydrothermal circulation beneath fast-spreading axis: Constraints from chronological approach,Sr isotope,and fluid–chromite inclusion investigation     

Norikatsu Akizawa  Akira Miyake  Yohei Igami  Akira Tsuchiyama  Hisashi Asanuma  Tetsu Kogiso  Shigeyuki Wakaki  Tsuyoshi Ishikawa  Shoji Arai  Jiwon Eom  Hodaka Kawahata  Takahiro Aze  Yusuke Yokoyama 《Island Arc》2021,30(1):e12423

Hydrothermal circulation beneath the spreading axis plays a significant role in the exchange of energy and mass between the solid Earth and the oceans. Deep-seated hydrothermal circulation down to the crust/mantle boundary in the fast-spreading axis has been introduced by a number of studies regarding geological investigations and numerical models. In order to assess a reaction between hydrothermal fluid and host rock around the crust/mantle boundary, we conducted bulk trace element and Sr isotope analyses with a series of in situ investigations for crustal anorthosite, a reaction product between hydrothermal fluid and gabbro in the lowermost crustal section along Wadi Fizh, northern Oman ophiolite. In addition, we conducted titanite U–Pb isotope analyses to evaluate timing of the crustal anorthosite formation in the framework of the evolutional process of the Oman ophiolite. We estimated the formation age of the crustal anorthosite at 97.5 Ma ± 5.0 Ma, overlapping with the timing of the crust formation in the paleo spreading axis. The crustal anorthosite shows high-Th/U ratio (~2.5) and high-initial ⁸⁷Sr/⁸⁶Sr ratio (0.7050) due to seawater-derived hydrothermal fluid ingress into the precursor gabbro. With using analytical technique of micro-excavation at cryo-temperature, we detected Cl from a few micrometer-sized inclusion of aqueous fluid and chromite grains. The solubility of Cr was enhanced by complexation reactions with Cl in the hydrothermal fluid. Regarding reconstructed three-dimensional mass distribution of the inclusion and chromite composition, maximum Cr content of parental fluid was estimated at ~69 000 μg/g. The exceptionally high-Cr content was achieved locally by leaking of fluid and synchronous chromite crystallization during fluid entrapment. Presence of the deep-seated hydrothermal circulation could be assigned to the segment end, where cold seawater penetrates into the lowermost crust and extract heat along widely spaced network-like fluid channel.  相似文献   

Food sources of benthic animals on intertidal and subtidal bottoms in inner Ariake Sound,southern Japan,determined by stable isotopes     

Hisashi Yokoyama  Tomoko SakamiYuka Ishihi 《Estuarine, Coastal and Shelf Science》2009

To evaluate the relative importance of possible food sources, including riverine particulate organic matter, reeds, benthic microalgae, seaweeds, cultured laver (Porphyra) and coastal phytoplankton, for commercial bivalves and co-occurring benthic animals, 73 macrofaunal species were collected from intertidal and subtidal soft bottoms in the inner part of Ariake Sound, Kyushu, southern Japan, and their isotopic compositions were analyzed. The results revealed that (1) both intertidal and subtidal food webs were constituted of 3 trophic levels, (2) suspension-feeding bivalves utilize a mixture of benthic microalgae and coastal phytoplankton, and omnivores and carnivores incorporate benthic microalgae and phytoplankton through their intermediate prey, and (3) 3 bivalves (Scapharca kagoshimensis, Modiolus metcalfei and Atrina lischkeana) inhabiting both intertidal and subtidal bottoms showed similar seasonal fluctuations, suggesting no difference in the diet composition among the species and between the 2 habitats. We conclude that a large biomass of benthic microalgae which was approximately equal to that of phytoplankton and the strong tidal currents that would resuspend benthic microalgae and transport them to subtidal bottom areas account for the benthic microalgal and phytoplankton based trophic structure in the inner part of Ariake Sound.  相似文献   

New records of three <Emphasis Type="Italic">Paraprionospio</Emphasis> species (Polychaeta: Spionidae) from Korean waters     

Hisashi Yokoyama  Jin-Woo Choi 《Ocean Science Journal》2010,45(1):55-61

The spionid polychaete Paraprionospio pinnata (Ehlers 1901) has been widely reported from Korean waters. We examined some specimens belonging to the genus Paraprionospio that had been collected from Korean waters, and identified them as Paraprionospio coora Wilson, 1990, Paraprionospio cordifolia Yokoyama, 2007 and Paraprionospio patiens Yokoyama, 2007, which are new to the fauna of Korea. The present study suggests misidentification of the specimens that have been previously reported as P. pinnata from Korean waters.  相似文献