title: Vertical distribution of236U in the North Pacific Ocean.
abstract: The first extensive study on236U in the North Pacific Ocean has been conducted. The vertical distribution of236U/238U isotopic ratios and the236U concentrations were analysed on seven depth profiles, and large variations with depth were found. The range of236U/238U isotopic ratios was from (0.09 ± 0.03) × 10-10to (14.1 ± 2.2) × 10-10, which corresponds to236U concentrations of (0.69 ± 0.24) × 105atoms/kg and (119 ± 21) × 105atoms/kg, respectively. The variations in236U concentrations could mainly be attributed to the different water masses in the North Pacific Ocean and their formation processes. Uranium-236 inventories on the water column of each sampling station were calculated and varied between (3.89 ± 0.08) × 1012atoms/m2and (7.03 ± 0.50) × 1012atoms/m2, which is lower than in former studies on comparable latitudes in the North Atlantic Ocean and the Sea of Japan. The low inventories of236U found for the North Pacific Ocean in this study can be explained by the lack of additional input sources of artificial radionuclides, apart from global and regional/local fallout. This study expands the use of236U as oceanographic circulation tracer to yet another ocean basin and shows that this isotope can be used for tracing circulation patterns of water masses in the Pacific Ocean.
authors.affiliation: Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan. Electronic address: rosmarie_eigl@yahoo.de.
authors.forename: R
authors.initials: R
authors.lastname: Eigl
authors.affiliation: VERA-Laboratory, Faculty of Physics - Isotope Research, University of Vienna, Währinger Str. 17, 1090 Vienna, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Steier
authors.affiliation: Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sakata
authors.affiliation: Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Sakaguchi
mesh_terms: D007564:Japan; D010140:Pacific Ocean; D011834:Radiation Monitoring; D011847:Radioactive Fallout / Q000032:analysis*; D014501:Uranium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D011847:Radioactive Fallout; D014875:Water Pollutants, Radioactive; D014501:Uranium