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Th and 
Th distributions in mid-latitudes of the North Pacific Ocean; Effect of bottom scavengingOkubo, Ayako; Obata, Hajime*; Gamo, Toshitaka*; Yamada, Masatoshi*
Earth and Planetary Science Letters, 339-340, p.139 - 150, 2012/07
Times Cited Count：39 Percentile：72.16(Geochemistry & Geophysics)Vertical distributions of total Th and dissolved Th were determined in the mid-latitudes of the North Pacific Ocean. Th in the Pacific Ocean have been described well using the reversible-scavenging model. However, we observed the depletion of total Th. The enhanced vertical eddy diffusion derived from the complex topography of the western Pacific Ocean might promote bottom scavenging and transport of the low Th in deep water to the upper layers.
Th in the Pacific Ocean and their relation to advection and diffusionOkubo, Ayako; Obata, Hajime*; Gamo, Toshitaka*; Yamada, Masatoshi*
no journal, ,
We investigated the vertical distribution of total Th in mid latitudes of the Pacific Ocean. The west to east section of Th shows a strong gradient in the deep waters around 170 degree east and 110 degree west. At depths of 2000 to 4000 m and 4000 m to bottom within the time-scale of scavenging residence time of Th, the horizontal eddy diffusion could reach 1100 to 1400 km and 400 to 700 km, respectively. The horizontal eddy diffusion transport is too weak to affect Th distribution in the deep layers between each station in this study area.
Obata, Hajime*; Miwa, Kazuji*; Kondo, Yoshiko*; Gamo, Toshitaka*; Otosaka, Shigeyoshi; Suzuki, Takashi
no journal, ,
Distributions chemical species of iodine (iodide, iodate and organic iodine) in seawater were investigated in the Chukchi Sea and Bering Sea, Arctic northern marginal seas. 
I, which is a good tracer for anthropogenically released iodine to the marine environments, were also revealed by this study. Iodide concentrations in seawater often increased toward the seafloor. This tendency was remarkable with iodide and organic iodine, indicating that these iodine species are released from the sediments of the continental shelf. Concentrations of I ranged from 0.79 to 2.89
10
atom/L. While this level was several times higher than those in the North Pacific, significant increase of I concentration due to seawater inflow from the North Atlantic was not observed. Considering latitudinal range of this study area, it can be estimated that most I detected by this study was derived by atmospheric deposition of I originates from Europe.
