Beryllium-7 Deposition and Its Relation to Sulfate Deposition   总被引：2，自引：0，他引：2  

Yasuhito Igarashi  Katsumi Hirose  Makiko Otsuji-Hatori 《Journal of Atmospheric Chemistry》1998,29(3):217-231

Deposition of ⁷Be, a cosmogenic radionuclide, was observed at the Meteorological Research Institute in Tsukuba, Japan from 1986 to 1993 and compared with those of several chemical species observed in Tsukuba over the same period. We found a correlation between the monthly depositions of ⁷ Be and SO ₄ ² -, a major acidic species. The correlation was especially strong for late spring and fall, when both species had high depositional fluxes. This correlation was also observed in precipitation samples collected daily in 1992 at the same site. The cause of this correlation is discussed in connection with the fact that the stratospheric aerosol is composed largely of SO ₄ ² -. ⁷ Be is produced in the upper atmosphere, and detection of ⁷Be, especially in spring and fall in Japan, can be regarded as detection of stratospheric aerosol. However, we conclude that the bulk of the SO ₄ ² - observed did not have a stratospheric or an upper tropospheric origin. The correlation, therefore, may present a new question regarding acidic deposition: Why does the deposition of stratospheric aerosol in Japan coincide with that of nss-SO ₄ ² - originally from anthropogenic sources on the Earth's surface?  相似文献   

Submarine flank eruption preceding caldera subsidence during the 2000 eruption of Miyakejima Volcano, Japan     

Takayuki Kaneko  Atsushi Yasuda  Taketo Shimano  Setsuya Nakada  Toshitsugu Fujii  Toshihiko Kanazawa  Azusa Nishizawa  Yoshihiro Matsumoto 《Bulletin of Volcanology》2005,67(3):243-253

During the early part of a seismic swarm preceding eruption and caldera formation at Miyakejima Volcano, discoloured sea surfaces were observed 1.5 km off the western coast of Miyakejima on 27 June 2000. A later survey of the area using a multi-beam side scan sonar and a remotely operated small submarine revealed four craters of 20–30 m diameter aligned east-west in a 100×10–30 m area on the seafloor, with hot water at 140°C being released from one of the centres. Each crater consists of submarine spatter overlain in part by scoria lapilli. Dredged spatter from the craters was fresh, and there was no evidence of activity of marine organisms on the spatter surface, indicating that the discoloured sea surface resulted from magmatic eruption on the seafloor. This eruption occurred when a westward-propagating seismic swarm, initiated beneath Miyakejimas summit, passed through the area. Finding new magma on the seafloor demonstrates that this seismic swarm was associated with intruding magma, moving outward from beneath Miyakejima. Submarine spatter shows flattened shapes with a brittle crust formed by cooling in water, and its composition is aphyric andesite of 54 wt% SiO₂. The spatter is similar in whole rock and mineral composition to spatter erupted in 1983. However, the wide range of Cl in melt inclusions in plagioclase of the 27 June submarine spatter shows that it is not simply a remnant of the 1983 magma, which has only high Cl melt inclusions in plagioclase. The mixed character of melt inclusions suggests involvement of a magma with low Cl melt inclusions. The magma erupted explosively on 18 August from Miyakejimas summit, considered as the second juvenile magma in this eruption, contains low Cl melt inclusions in plagioclase. Based on these observations and the eruption sequence, we present the following model: (1) A shallow magma chamber was filled with a remnant of 1983 magma that had evolved to a composition of 54–55 wt% SiO₂. (2) Injection of the 18 August magma into this chamber generated a mixed magma having a wide range of Cl in melt inclusions contained plagioclase. The magma mixing might have occurred shortly before the submarine eruption and could have been a trigger for the initiation of the removal of magma from the chamber as an extensive dyke, which eventually led to caldera subsidence.Editorial responsibility: S Nakada, T Druitt  相似文献   

A high-resolution climatic change since the Late Glacial Age inferred from multi-proxy of sediments in Qinghai Lake   总被引：12，自引：3，他引：9  

Ryo Matsumoto 《中国科学D辑(英文版)》2005,48(6):742-751

The study of climatic changes since the Late Glacial Age has become one of the hotspots of the PAGES in recent years.Deep-sea cores from the high-latitude area show that the climate was very unstable during the transitional period from the Late Glacial Age to the Holocene[1,2],which has also been testified by the geological records from ocean sediments,ice cores and terrestrial sections in different latitudes of the earth[3—8].What’s more,climatic instability also ex-isted in the Holoce…  相似文献   

Role of metal-organic complexes in the marine environment: A comparison of the copper and ligand titration methods     

Katsumi Hirose  Yukio Sugimura 《Marine Chemistry》1985,16(3):239-247

The differences in quality of the conditional stability constants deduced from ligand titration and metal titration methods are theoretically examined. The ecological role of the metal-organic complexes in seawater was considered on the basis of the concept of the metal buffering capacity index which is calculated from the conditional stability constant and the organic ligand concentration. The results of theoretical examination of the effect of metal contamination on the uptake of metals by phytoplankton indicate that the ecological significance of metal-organic complexes is essentially in the metal-buffering action. This means that the activities of free metal ions are maintained at a native constant level against relatively small perturbations by the addition or uptake of metals in the marine environment.  相似文献   

Seasonal differences in catches of leptocephali in the East China Sea and Suruga Bay, Japan   总被引：2，自引：0，他引：2  

Gen Minagawa  Michael J. Miller  Yobuo Kimura  Shun Watanabe  Akira Shinoda  Jun Aoyama  Katsumi Tsukamoto 《Estuarine, Coastal and Shelf Science》2007,71(3-4):730-740

The species composition, distribution, and size of eel larvae, or leptocephali, caught near the continental shelf in subtropical and temperate regions of East Asia were compared between two seasons (May–Jun and Oct–Dec) to learn about the seasonality of reproduction of marine eels. There was greater species richness and evidence of spawning by more species of marine eels during the late autumn surveys in both the East China Sea (ECS) and in Suruga Bay along the east coast of Japan. Small leptocephali <10 mm TL and a wide range of sizes of various taxa were collected during both seasons along the outer edge of the continental shelf in the ECS, indicating that some marine eels may spawn there all year. The lack of small leptocephali during the spring survey in Suruga Bay suggested that most eels have a clear seasonal cycle of summer or autumn spawning at the higher latitudes of coastal Japan where there is much greater fluctuation of water temperature throughout the year than in the ECS. At lower latitudes such as in the ECS, and in tropical areas where water temperatures are higher and more constant, some marine eels may spawn all year round.  相似文献   

Sedimentation rate and heavy metal pollution in sediments in Harima Nada (Harima Sound), Seto Inland Sea     

Akira Hoshika  Takayuki Shiozawa  Eiji Matsumoto 《Journal of Oceanography》1983,39(2):82-87

Sedimentation rates were determined with the²¹⁰Pb technique in six sediment cores from Harima Nada (Harima Sound), Seto Inland Sea. The rate of deposition varies from 0.11 g cm^–2y^–1 in the northern part to 0.33 g cm^–2 y^–1 in the southern part of the basin. A marked increase in copper and zinc content was observed above a depth in the core corresponding to about 1900 A.D. as a result of increasing human activities. Anthropogenic input of copper and zinc decreased slightly after 1970. Natural background levels of copper and zinc in the sediment in this sound are 11–16 ppm and 100–120 ppm, respectively. The total amounts of anthropogenic copper and zinc in the sediments were estimated to be 110–180g cm^–2 and 610–1,280g cm^–2, respectively. These values constitute 40–50% of the total sedimentary input of copper and zinc in the sediments since about 1900 A.D.  相似文献   

Estimating Chlorophyll-<Emphasis Type="Italic">a</Emphasis> Vertical Profiles from Satellite Data and the Implication for Primary Production in the Kuroshio Front of the East China Sea     

Eko?Siswanto  Joji?IshizakaEmail author  Katsumi?Yokouchi 《Journal of Oceanography》2005,61(3):575-589

An algorithm was evaluated for estimating primary production in the Kuroshio front of the East China Sea. The algorithm involves three principal inputs: chlorophyll-a (Chl-a) vertical profile, water column photosynthetic parameter and underwater irradiance parameter. We construct empirical models for estimating those three inputs from sea surface variables accessible by means of satellite remote sensing. Types of Chl-a vertical profile were closely associated with water mass features, and sea surface temperature seemed to be a potential variable to distinguish profile types. The consequence of the deep Chl-a maximum (DCM) presence was investigated by comparing the vertically non-uniform Chl-a profile against the uniform Chl-a profile in terms of the integrated biomass and primary production estimates. Since the DCM in the frontal region occurred in a relatively shallow layer with relatively high light level, allowing intensive photosynthetic processes to take place in the DCM layer. In contrast, as the DCM in the Kuroshio region occurred in the low-light, deep layer, it contributed less to the integrated primary production. We inferred that the DCM formation is more important in the frontal region than in the Kuroshio region, as they potentially contributed within 30.9% (±9.1%) and 20.9% (±5.4%) to the integrated primary production in the frontal and the Kuroshio regions, respectively. Such different degrees in the DCM contribution was then revealed by the higher integrated primary production in the frontal region than in the Kuroshio region.  相似文献   

Gravity field derived from the altimetric geoid and its implications for the origin,driving force and evolution of microplate-type marginal basins in the southwestern Pacific     

Takeshi Matsumoto 《Marine Geophysical Researches》1996,18(2-4):147-161

The thickness anomaly of lithosphere in the North Fiji Basin, Lau Basin and the surrounding area was obtained from gravity data derived by satellite altimetry, using crustal thickness determined by available seismic refraction studies. It was revealed that the North Fiji Basin is an isolated asthenospheric dome and that the lithospheric thickness is about 50km less than that of the surrounding area. Such a lithospheric structure and surface topographic feature suggest a plume-like mantle upwelling beneath these basins. The result of numerical simulation shows the possibility of opening of the back-are area and change of subduction polarity which occurred at the first stage of the evolution of the North Fiji Basin. As the lifetime of the southwestern Pacific marginal basins is limited to some 10 million years in most cases, the heat source (plume) which initiates these marginal basins might be sporadic, and their expansion will end when the heat source is wholly consumed.  相似文献   

Active oceanic spreading in the northern North Fiji Basin: Results of the NOFI cruise of R/V L'Atalante (newstarmer project)   总被引：1，自引：0，他引：1  

Yves Lagabrielle  Etienne Ruellan  Manabu Tanahashi  Jacques Bourgois  Georges Buffet  Giovanni de Alteriis  Jérôme Dyment  Jean Goslin  Eulàlia Gràcia-Mont  Yo Iwabushi  Philip Jarvis  Masato Joshima  Anne-Marie Karpoff  Takeshi Matsumoto  Hélène Ondréas  Bernard Pelletier  Olivier Sardou 《Marine Geophysical Researches》1996,18(2-4):225-247

The South Pandora and the Tripartite Ridges are active spreading centers located in the northern part of the North Fiji Basin. These spreading centers were surveyed over a distance of 750 km during the NOFI cruise of R/V L'Atalante (August–September 1994) which was conducted in the frame of the french-japanese Newstarmer cooperation project. SIMRAD EM12-dual full coverage swath bathymetric and imagery data as well as airgun 6-channel seismic, magnetics and gravity profiles were recorded along and offaxis from 170°40 E to 178° E. Dredging and piston coring were also performed along and off-axis. The axial domain of the South Pandora Ridge is divided into 5 first-order segments characterized by contrasted morphologies. The average width of the active domain is 20 km and corresponds either to bathymetric highs or to deep elongated grabens. The bathymetric highs are volcanic constructions, locally faulted and rifted, which can obstruct totally the axial valley. The grabens show the typical morphology of slow spreading axes, with two steep walls flanking a deep axial valley. Elongated lateral ridges may be present on both sides of the grabens. Numerous volcanoes, up to several kilometers in diameter, occur on both flanks of the South Pandora Ridge. The Tripartite Ridge consists of three main segments showing a sigmoid shape. Major changes in the direction of the active zones are observed at the segment discontinuities. These discontinuities show various geometrical patterns which suggest complex transform relay zones. Preliminary analysis of seismic reflection profiles suggest that the Tripartite Ridge is a very young feature which propagates into an older oceanic domain characterized by a significant sedimentary cover. By contrast, a very thin to absent sedimentary cover is observed about 100 km on both flanks of the South Pandora Ridge active axis. The magnetic anomaly profiles give evidence of long and continuous lineations, parallel to the South Pandora Ridge spreading axis. According to our preliminary interpretation, the spreading rate would have been very low (8 km/m.y. half rate) during the last 7 Ma. The South Pandora and Tripartite Ridges exhibit characteristics typical of active oceanic ridges: (1) a segmented pattern, with segments ranging from 80 to 100 km in length; (2) an axial tectonic and volcanic zone, 10 to 20 km wide; (3) well-organized magnetic lineations, parallel to the active axis; (4) clear signature on the free-air gravity anomaly map. However, no typical transform fault is observed; instead, complex relay zones are separating first-order segments.  相似文献   

Sedimentation rates in Funka Bay,HokkaidÔ     

Eiji Matsumoto  Shigeko Togashi 《Journal of Oceanography》1980,35(6):261-267

Undisturbed sediment cores were collected by a modified gravity corer from Funka Bay. The sedimentation rate is determined by both²¹⁰Pb and pumice chronological methods. The sedimentation rates by²¹⁰Pb method are concordant with those by pumice methods. The derived rate varies from 0.06 to 0.22 g cm^–2 y^–1, and an average is 0.09 g cm^–2 y^–1.  相似文献