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| Titel |
Short-term dispersal of Fukushima-derived radionuclides off Japan: modeling efforts and model-data intercomparison |
| VerfasserIn |
I. I. Rypina, S. R. Jayne, S. Yoshida, A. M. Macdonald, E. Douglass, K. Buesseler |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-24), S.4973-4990 |
| Datensatznummer |
250018356
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| Publikation (Nr.) |
 copernicus.org/bg-10-4973-2013.pdf |
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| Zusammenfassung |
| The Great East Japan Earthquake and tsunami that caused a loss of power at
the Fukushima nuclear power plants (FNPP) resulted in emission of radioactive
isotopes into the atmosphere and the ocean. In June of 2011, an international
survey measuring a variety of radionuclide isotopes, including 137Cs,
was conducted in surface and subsurface waters off Japan. This paper presents
the results of numerical simulations specifically aimed at interpreting these
observations and investigating the spread of Fukushima-derived radionuclides
off the coast of Japan and into the greater Pacific Ocean. Together, the
simulations and observations allow us to study the dominant mechanisms
governing this process, and to estimate the total amount of radionuclides in
discharged coolant waters and atmospheric airborne radionuclide fallout. The
numerical simulations are based on two different ocean circulation models,
one inferred from AVISO altimetry and NCEP/NCAR reanalysis wind stress, and
the second generated numerically by the NCOM model. Our simulations determine
that > 95% of 137Cs remaining in the water within
~600 km of Fukushima, Japan in mid-June 2011 was due to the direct
oceanic discharge. The estimated strength of the oceanic source is
16.2 ± 1.6 PBq, based on minimizing the model-data mismatch. We cannot
make an accurate estimate for the atmospheric source strength since most of
the fallout cesium had left the survey area by mid-June. The model explained
several key features of the observed 137Cs distribution. First, the
absence of 137Cs at the southernmost stations is attributed to the
Kuroshio Current acting as a transport barrier against the southward
progression of 137Cs. Second, the largest 137Cs concentrations were
associated with a semi-permanent eddy that entrained 137Cs-rich waters,
collecting and stirring them around the eddy perimeter. Finally, the
intermediate 137Cs concentrations at the westernmost stations are
attributed to younger, and therefore less Cs-rich, coolant waters that
continued to leak from the reactor in June of that year. |
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