Japan Agency for Marine-Earth Science and Technology

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    47911 research outputs found

    Changes in earth's energy flows and clouds in 228-year simulation with a high resolution AGCM

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    Wet and dry basalt magma evolution at Torishima volcano, Izu-Bonin arc, Japan: the possible role of phengite in the downgoing slab

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    The arc-front volcanoes of Sumisu (31?5°N, 140°E) and Torishima (30?5°N, 140?3°E) in the central Izu?Bonin arc are similar in size and rise as relatively isolated edifices from the seafloor. Together they provide valuable along-arc information about magma generation processes. The volcanoes have erupted low-K basalts originating from both wet and dry parental basaltic magmas (low-Zr basalts and high-Zr basalts, respectively). Based on models involving fluid-immobile incompatible element ratios (La/Sm), the parental basalts appear to result from different degrees of partial melting of the same source mantle (?20% and ?10% for wet and dry basalt magmas, respectively). Assuming that the wet basalts contain greater abundances of slab-derived components than their dry counterparts, geochemical comparison of these two basalt types permits the identification of the specific elements involved in fluid transport from the subducting slab. Using an extensive set of new geochemical data from Torishima, where the top of the downgoing slab is about 100 km deep, we find that Cs, Pb, and Sr are variably enriched in the low-Zr basalts, which cannot be accounted for by fractional crystallization or by differences in the degree of mantle melting. These elements are interpreted to be selectively concentrated in slab-derived metasomatic fluids. Variations in K, high field strength element and rare earth element concentrations are readily explained by variations in the degree of melting between the low- and high-Zr basalts; these elements are not contained in the slab-derived fluids. Rb and Ba exhibit variable behaviour in the low-Zr basalts, ranging from immobile, similar to K, to mildly enriched in some low-Zr basalts. We suggest that the K-rich mica, phengite, plays an important role in determining the composition of fluids released from the downgoing slab. In arc-front settings, where slab depth is ?100 km, phengite is stable, and the fluids released from the slab contain little K. In back-arc settings, however, where the slab is at 100?140 km depth, phengite is unstable, and K-rich fluids are released. We conclude that cross-arc variations in the K content of arc basalts are probably related to differing compositions of released fluids or melts rather than the widely held view that such variations are controlled by the degree of partial melting.http://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr02-16/

    Role of Acid Mobilization in Iron Solubility of Smaller Mineral Dust Aerosols

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    Poster abstract A21A-0013 presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec

    The vertical structure of the surface wave radiation stress for circulation over a sloping bottom as given by thickness-weighted-mean theory

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    Previous attempts to derive the depth-dependent expression of the radiation stress have led to a debate concerning (i) the applicability of the Mellor approach to a sloping bottom, (ii) the introduction of the delta function at the mean sea surface in the later papers by Mellor, and (iii) a wave-induced pressure term derived in several recent studies. The authors use an equation system in vertically Lagrangian and horizontally Eulerian (VL) coordinates suitable for a concise treatment of the surface boundary and obtain an expression for the depth-dependent radiation stress that is consistent with the vertically integrated expression given by Longuet-Higgins and Stewart. Concerning (i)-(iii) above, the difficulty of handling a sloping bottom disappears when wave-averaged momentum equations in the VL coordinates are written for the development of (not the Lagrangian mean velocity but) the Eulerian mean velocity. There is also no delta function at the sea surface in the expression for the depth-dependent radiation stress. The connection between the wave-induced pressure term in the recent studies and the depth-dependent radiation stress term is easily shown by rewriting the pressure-based form stress term in the thickness-weighted-mean momentum equations as a velocity-based term that contains the time derivative of the pseudomomentum in the VL framework

    Metadata Publication and Search System in JAMSTEC

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    Poster PS6-09, 1st ICSU World Data System Conference: Global Data for Global Science (September 3-6, 2011, Kyoto, Japan

    Structure and dynamics of the sudden acceleration of Kuroshio off Cape Shionomisaki

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    A sudden acceleration of the Kuroshio jet appears off Cape Shionomisaki in the high-resolution (horizontal resolution of 1/36°) JCOPE 2 ocean reanalysis data. Using this dataset, we investigated the structure of the Kuroshio acceleration. The increase in the velocity of the current is accompanied by a downstream flow separation from the coast and an outcrop of cold temperature inshore. The acceleration of Kuroshio appears when it takes a near-shore path. Cape Shionomisaki amplifies the responses to the Kuroshio flow by creating the zonal velocity acceleration toward the downstream region when the Kuroshio flows closer to the coast. The Kuroshio acceleration coincided with the topographic ridge on the continental shelf near Cape Shionomisaki. This relation suggests that the dynamics of the acceleration is linked to the topographic feature. We proposed an explanation of the Kuroshio acceleration using a hydraulic control theory. An analytical solution was applied to the coastal topography around the Kii Peninsula. The solution captured some aspects of the Kuroshio acceleration

    Geometry of the Philippine Sea plate subducting beneath the westernmost Nankai Trough

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    SSS035-06発表要旨 / 日本地球惑星科学連合2011年大会(2011年5月22日~5月27日, 幕張メッセ国際会議場) / 日本惑星科学連合の許諾に基づき本文ファイルを掲


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