title: Southward spreading of the Fukushima-derived radiocesium across the Kuroshio Extension in the North Pacific.
abstract: The accident of the Fukushima Dai-ichi nuclear power plant in March 2011 released a large amount of radiocesium into the North Pacific Ocean. Vertical distributions of Fukushima-derived radiocesium were measured at stations along the 149°E meridian in the western North Pacific during the winter of 2012. In the subtropical region, to the south of the Kuroshio Extension, we found a subsurface radiocesium maximum at a depth of about 300 m. It is concluded that atmospheric-deposited radiocesium south of the Kuroshio Extension just after the accident had been transported not only eastward along with surface currents but also southward due to formation/subduction of subtropical mode waters within about 10 months after the accident. The total amount of decay-corrected (134)Cs in the mode water was an estimated about 6 PBq corresponding to 10-60% of the total inventory of Fukushima-derived (134)Cs in the North Pacific Ocean.
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natushima-cho, Yokosuka, Kanagawa 237-0061, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kumamoto
authors.affiliation: 1] Geochemical Research Department, Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan [2].
authors.forename: Michio
authors.initials: M
authors.lastname: Aoyama
authors.affiliation: Low Level Radioactivity Laboratory, Kanazawa University, Wake, Nomi, Ishikawa 923-1224, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Hamajima
authors.affiliation: National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba 263-8555, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Aono
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natushima-cho, Yokosuka, Kanagawa 237-0061, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Kouketsu
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natushima-cho, Yokosuka, Kanagawa 237-0061, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Murata
authors.affiliation: Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natushima-cho, Yokosuka, Kanagawa 237-0061, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawano