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| Titel |
137Cs and 134Cs activity in the North Pacific Ocean water from 1945 to 2020 by eddy-resolving ROMS |
| VerfasserIn |
Takaki Tsubono, Kazuo Misumi, Daisuke Tsumune, Michio Aoyama, Katsumi Hirose |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147963
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| Publikation (Nr.) |
 EGU/EGU2017-12185.pdf |
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| Zusammenfassung |
| We conducted the simulation of 137Cs activity in the North Pacific Ocean (NPO) water
from 1945 to 2020, before and after the Fukushima Dai-ichi Nuclear Power Plant
(1F NPP) accident. Using the Regional Ocean Model System (ROMS) with high
resolution (1/12∘-1/4∘ in horizontal, 45 levels in vertical), of which domain was
the NPO, we preliminarily estimated a factor multiplying the total 134Cs fluxes,
which have been estimated for the atmospheric deposition and the direct discharge
from the accident. The direct comparison of the observed and calculated 134Cs
showed that the total 134Cs flux was 1.6 times greater than the previous estimates. We
re-calculated the 134Cs activityies in the NPO water using the flux multiplied by 1.6
and confirmed the improvement of the simulation by the multiplied flux, which
suggested that 134Cs and 137Cs inventories in the NPO increase by about 16PBq,
respectively, due to the accident. For the hindcast and forecast of the 137Cs activityies in
the NPO water, we calculated the 137Cs activityy in the NPO water from 1945 to
2020 by using the global fallout flux due to atmospheric nuclear weapons’ tests and
the Chernobyl accident and the estimated fluxes of the 1F NPP accident. For the
calculation, five ensemble calculations of 137Cs activity were conducted by moving the
start period of the input flux for one year. The 137Cs activity in the surface water
showed that the plume due to the 1F NPP accident with relatively higher activity
than 5 Bq m−3, which was lower than that in 1985, was transported to the western
area of 135∘W in 2015. The peak year of the 137Cs activity can be estimated from
the hindcast and forecast. The 137Cs activity in the surface water north of 30∘N
shows that the 137Cs peak in 2011 occurs up to 180∘, but the peak from 2012 to
2017 is distributed from near 180∘ to 90∘W. The total inventory of 137Cs in the
NPO increased up to 77 PBq in 2011 and gradually decreased to 61PBq in 2018 by
transport outside of the domain, which is almost the same as that in Dec. 2010.
The whole amount of 137Cs in the subsurface layer ( 200-600m depth ) is larger
than that in the surface layer ( 0-200m depth) since the 1F NPP accident except
2011. |
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