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Vertical Profiles of Ra-226 and Ra-228 Activity Concentrations in the Western Subarctic Gyre of the Pacific Ocean

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Title: Vertical Profiles of Ra-226 and Ra-228 Activity Concentrations in the Western Subarctic Gyre of the Pacific Ocean
Authors: Tazoe, Hirofumi Browse this author
Obata, Hajime Browse this author
Hara, Takuya Browse this author
Inoue, Mutsuo Browse this author
Tanaka, Takahiro Browse this author
Nishioka, Jun Browse this author →KAKEN DB
Keywords: radium-228
Subarctic Gyre of the Pacific Ocean
vertical flux
lateral transport
Issue Date: 31-May-2022
Publisher: Frontiers Media
Journal Title: Frontiers in Marine Science
Volume: 9
Start Page: 824862
Publisher DOI: 10.3389/fmars.2022.824862
Abstract: The vertical activity concentration distributions of the radium isotopes, Ra-226 and Ra-228, which are useful as radiotracers, were obtained for the first time in the western Subarctic Pacific Gyre (WSAG). It was possible to detect short-lived Ra-228 present from the surface to 400 m depth by analyzing large seawater samples. Low Ra-228 and high Ra-226 activity concentrations in the surface layer in the WSAG were strongly influenced by upwelled deeper water with nutrients. The activity concentration distribution of Ra-226 especially was in good agreement with the silicate concentration distribution, which was consistent with previous reported findings. These distributions were uniform from the surface to 100 m of the dichothermal layer due to vertical mixing in winter. Ra-228 activity concentration decreased with water depth below the pycnocline and reached the undetectable level at 600 m which was within the oxygen minimum layer. Estimations of vertical fluxes of Ra-228 and nitrate according to Ra-228 decay indicated that the vertical transport by eddy diffusion was a minor process for the Ra-228 and nitrate fluxes, and lateral transport mainly affected Ra-228 in the intermediate warm water, that is, the mesothermal layer below the main pycnocline. Vertical mixing or submarine underground water and lateral transport to the WSAG could yield this Ra-228 in the intermediate depth.
Type: article
Appears in Collections:低温科学研究所 (Institute of Low Temperature Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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