EGU21-14045, updated on 04 Mar 2021
https://doi.org/10.5194/egusphere-egu21-14045
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Long term variation of 137Cs inventory in the global ocean from 1957 to 2018

Yayoi Inomata1 and Michio Aoyama2
Yayoi Inomata and Michio Aoyama
  • 1Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan (yinomata@se.kanazawa-u.ac.jp)
  • 2Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba, Japan (michio.aoyama@ied.tsukuba.ac.jp)

The spatial and temporal variations in 137Cs concentrations in the surface seawater in the global ocean from 1957 to 2018 were analyzed by using the ''HAM database - global 2018'' and “IAEA-MARIS database” in order to understand the behaviors of 137Cs originated atmospheric weapons tests, nuclear fuel reprocessing plants, and nuclear power plant accidents at Chernobyl and Fukushima. The global ocean was divided into 37 boxes. The 0.5yr average value of 137Cs, apparent half residence times (Tap), and 137Cs inventory in each box was estimated. The 0.5yr average value of 137Cs in each oceanic region (box) indicate that 137Cs decreased exponentially from 1970 to 2010 in the Pacific Ocean (PO), Indian Ocean (IO), and Atlantic Ocean (AO), except for the Arctic Ocean, North Atlantic Ocean and its marginal sea due to the discharge of 137Cs from the nuclear fuel reprocessing plants. The geographical difference of 137Cs activity concentrations in the global ocean become to be small in the year of 2010. The temporal variation of 137Cs column inventory suggests that 137Cs derived from the large scale atmospheric weapon tests exist largely in the subtropical NPO, equatorial PO, and subtropical SPO (25°N-25°S). 137Cs transport from the PO to the IO occurs in the region from 0°-15°S via Indonesian through flow. The signature of 137Cs transport from the IO to the AO is also detected. The 137Cs inventory in the surface seawater in the year 2010 is estimated to be 57±17 PBq. Considering that the radioactive decay 137Cs are estimated to be 347 PBq, the 137Cs existed into the ocean interior is estimated to 173±52 PBq. These indicate that about 30% of 137Cs released into the surface seawater have been transported into the ocean interior in 2010. The 137Cs inventory in 2011 in the surface seawater in the global ocean were 69±15 PBq. The 137Cs released by the Fukushima Nuclear Power Plant 1 accident increased to 16.5±4.8 PBq and this value is in good agreement with previous studies.

How to cite: Inomata, Y. and Aoyama, M.: Long term variation of 137Cs inventory in the global ocean from 1957 to 2018, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14045, https://doi.org/10.5194/egusphere-egu21-14045, 2021.

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