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| Titel |
137Cs off Fukushima Dai-ichi, Japan – model based estimates of dilution and fate |
| VerfasserIn |
H. Dietze, I. Kriest |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 8, no. 3 ; Nr. 8, no. 3 (2012-06-05), S.319-332 |
| Datensatznummer |
250005628
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| Publikation (Nr.) |
 copernicus.org/os-8-319-2012.pdf |
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| Zusammenfassung |
In the aftermath of an earthquake and tsunami on 11 March 2011 radioactive
137Cs was discharged from a damaged nuclear power plant to the sea off
Fukushima Dai-ichi, Japan. Here we explore its dilution and fate with a
state-of-the-art global ocean general circulation model, which is
eddy-resolving in the region of interest. We find apparent consistency
between our simulated circulation, estimates of 137Cs discharged ranging
from 0.94 p Bq (Japanese Government,
2011) to 3.5 ± 0.7 p Bq
(Tsumune et al., 2012), and measurements by Japanese authorities and the power
plant operator. In contrast, our simulations are apparently inconsistent with
the high 27 ± 15 p Bq discharge estimate of Bailly
du Bois et al. (2012).
Expressed in terms of a diffusivity we diagnose, from our simulations, an
initial dilution on the shelf of 60 to 100 m2 s−1. The
cross-shelf diffusivity is at 500 ± 300 m2 s−1 significantly
higher and variable in time as indicated by its uncertainty. Expressed as an
effective residence time of surface water on the shelf, the latter estimate
transfers to 43 ± 16 days.
As regards the fate of 137Cs, our simulations suggest that activities up
to 4 mBq l−1 prevail in the Kuroshio-Oyashio Interfrontal
Zone one year after the accident. This allows for low but detectable 0.1 to
0.3 m Bq l−1 entering the North Pacific Intermediate Water
before the 137Cs signal is flushed away. The latter estimates concern
the direct release to the sea only. |
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