References

Ocean Science

Ocean Sci.

1812-0792

Copernicus Publications

Göttingen, Germany

10.5194/os-8-319-2012

137Cs off Fukushima Dai-ichi, Japan – model based estimates of dilution and fate

Dietze

¹ Kriest

IFM-GEOMAR, Leibniz Institute of Marine Sciences, Düsternbrooker Weg 20, 24105 Kiel, Germany

05 06 2012

8 3 319 332

2012

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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.

References 1

Antonov, J. I., Locarnini, R. A., Boyer, T. P., Mishonov, A. V., Garcia, H. E., and Levitus, S.: World Ocean Atlas 2005, Volume 2: Salinity. NOAA Atlas NESDIS 62, U.S. Government Printing Office, Washington, DC, 182 pp., 2006.

Bailly du Bois, P., Laguionie, P., Boust, D., Korsakissok, I., Didier, D., and Fiévet, B.: Estimation of marine source-term following Fukushima Dai-ichi accident, Journal of Environmental Radioactivity, <a href="http://dx.doi.org/10.1016/j.jenvrad.2011.11.015">https://doi.org/10.1016/j.jenvrad.2011.11.015</a>, in press, 2012.

Buesseler, K. O., Aoyama, M., and Fukasawa, M.: Impacts of the Fukushima Nuclear Power Plants on marine radioactivity, Environ. Sci. Technol., 45, 9931–9935, <a href="http://dx.doi.org/10.1021/es202816c">https://doi.org/10.1021/es202816c</a>, 2011.

Buesseler, K. O., Jayne, S. R., Fisher, N. S., Rypina, I. I., Baumann, H., Baumann, Z., Breier, C. F., Douglass, E. M., George, J., Macdonald, A. M., Miyamoto, H., Nishikawa, J., Pike, S. M., and Yoshida, S: Fukushima-derived radionuclides in the ocean and biota off Japan, P. Natl. Acad. Sci. USA, 109, 5984–5988, <a href="http://dx.doi.org/10.1073/pnas.1120794109">https://doi.org/10.1073/pnas.1120794109</a>, 2012.

Capet, X., Campos, E. J., and Pavia, A. M.: Submesoscale activity over the Argentinian shelf, Geophys. Res. Lett., 35, 1–5, <a href="http://dx.doi.org/10.1029/2008GL034736">https://doi.org/10.1029/2008GL034736</a>, 2008.

Dietze, H. and Kriest, I.: Tracer distribution in the Pacific Ocean following a release off Japan – what does an oceanic general circulation model tell us?, Ocean Sci. Discuss., 8, 1441–1466, <a href="http://dx.doi.org/10.5194/osd-8-1441-2011">https://doi.org/10.5194/osd-8-1441-2011</a>, 2011.

Dietze, H., Matear, R. J., and Moore, T. J.: Nutrient supply to anticyclonic meso-scale eddies off western Australia estimated with artificial tracers released in a circulation model, Deep-Sea Res. I, 56, 1440–1448, <a href="http://dx.doi.org/10.1016/j.dsr.2009.04.012">https://doi.org/10.1016/j.dsr.2009.04.012</a>, 2009.

Ducet, N. and LeTraon, P. Y.: A comparison of surface eddy kinetic energy and Reynolds stresses in the Gulf Stream and the Kuroshio Current systems from merged TOPEX/Poseidon and ERS-1/2 altimetric data, J. Geophys. Res., 106, 16603–16622, 2001.

Fratantoni, D. M.: North Atlantic surface circulation during the 1990's observed with satellite-tracked drifters, J. Geophys. Res., 106, 22067–22093, 2001.

Griffies, S. M., Gnanadesikan, A., Dixon, K. W., Dunne, J. P., Gerdes, R., Harrison, M. J., Rosati, A., Russell, J. L., Samuels, B. L., Spelman, M. J., Winton, M., and Zhang, R.: Formulation of an ocean model for global climate simulations, Ocean Sci., 1, 45–79, <a href="http://dx.doi.org/10.5194/os-1-45-2005">https://doi.org/10.5194/os-1-45-2005</a>, 2005.

Griffies, S. M. and Hallberg, R. W.: Biharmonic friction with a Smagorinsky-like viscosity for use in large-scale eddy-permitting ocean models, Mon. Weather Rev., 128, 2935–2946, 2000.

Houghton, R. W., Hebert, D., and Prater, M.: Circulation and mixing at the New England shelfbreak front: Results of purposeful tracer experiments, Prog. Oceanogr., 70, 289–312, <a href="http://dx.doi.org/10.1016/j.pocean.2006.05.001">https://doi.org/10.1016/j.pocean.2006.05.001</a>, 2006.

Institut de Radioprotection et de sûreté nucléaire: Impact on the marine environment of radioactive releases following the nuclear accident at Fukushima Dai-ichi 13th of May 2011, 2011.

Japanese Government, Report of Japanese Government to the IAEA ministerial conference on nuclear safety: The accident at TEPCO's Fukushima nuclear power stations, Nuclear Emergence Response Headquaters, Government of Japan, 2011.

Large, W. G., McWilliams, J. C., and Doney S. C.: Oceanic vertical mixing: a review and a model with a nonlocal boundary layer parameterization, Rev. Geophys., 32, 363–403, 1994.

Ledwell, J. R., Watson, A. J., and Law, C. S.: Mixing of a tracer in the pycnocline, J. Geophys. Res., 103, 21499–21529, 1998.

Liu, N., Eden, C., Dietze, H., Wu, D., and Lin, X.: Model-based estimate of the heat budget in the East China Sea, J. Geophys. Res., 115, C08026, <a href="http://dx.doi.org/10.1029/2009JC005869">https://doi.org/10.1029/2009JC005869</a>, 2010.

Locarnini, R. A., Mishonov, A. V., Antonov, J. I., Boyer, T. P., Garcia, H. E., and Levitus, S.: World Ocean Atlas 2005, Volume 1: Temperature, NOAA Atlas NESDIS 61, U.S. Government Printing Office, Washington, DC, 182 pp., 2006.

Morino, Y., Ohara, T., and Nishizawa, M.: Atmospheric behavior, deposition, and budget of radioactive materials from the Fukushima Daiichi nuclear power plant in March 2011, Geophys. Res. Lett., 38, L00G11, <a href="http://dx.doi.org/10.1029/2011GL048689">https://doi.org/10.1029/2011GL048689</a>, 2011.

Nakanishi, T., Aono, T., Yamada, M., and Kusakabe, M.: Temporal and spatial variations of 137Cs in the waters off a nuclear fuel reprocessing facility in Rokasho, Aomori, Japan, Journal of Radioanalytical and Nuclear Chemistry, 283, 831–838, <a href="http://dx.doi.org/10.1007/s10967-009-0422-y">https://doi.org/10.1007/s10967-009-0422-y</a>, 2010.

Niiler, P. P., Maximenko, N. A., Panteleev, G. G., Yamagata, T., and Olson, D. B.: Near-surface dynamical structure of the Kuroshio Extension, J. Geophys. Res., 108, 3193, <a href="http://dx.doi.org/10.1029/2002JC001461">https://doi.org/10.1029/2002JC001461</a>, 2003.

Oke, P. R., Schiller, A., Griffin, D. A., and Brassington, G. B.: Ensemble data assimilation for an eddy-resolving ocean model of the Australian region, Q. J. Roy. Meteorol. Soc., 131, 3301–3311, <a href="http://dx.doi.org/10.1256/qj.05.95">https://doi.org/10.1256/qj.05.95</a>, 2005.

Okubo, A.: Oceanic diffusion diagrams, Deep-Sea Res., 18, 789–802, 1971.

Orre, S., Gao, Y., Drange, H., and Deleersnijder, E.: Diagnosing ocean tracer transport from Sellafield and Dounreay by equivalent diffusion and age, Adv. Atmos. Sci., 25, 805–814, <a href="http://dx.doi.org/10.1007/s00376-008-0805-y">https://doi.org/10.1007/s00376-008-0805-y</a>, 2008.

Park, J. H., Chang, B. U., Kim, Y. J, Seo, J. S., Choi, S. W., and Yun, J. Y.: Determination of low 137Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method, J. Environ. Radioactivity, 99, 1815–1818, <a href="http://dx.doi.org/10.1016/j.jenvrad.2008.07.006">https://doi.org/10.1016/j.jenvrad.2008.07.006</a>, 2008.

Qiao, F. L., Wang, G. S., Zhao, W., Zhao, J. C., Dai, D. J., Song, Y. J., and Song, Z. Y.: Predicting the spread of nuclear radiation from the damaged Fukushima Nuclear Power Plant, Chinese Science Bulletin, 56, 1890–1896, <a href="http://dx.doi.org/10.1007/s11434-011-4513-0">https://doi.org/10.1007/s11434-011-4513-0</a>, 2011.

Stohl, A., Seibert, P., Wotawa, G., Arnold, D., Burkhart, J. F., Eckhardt, S., Tapia, C., Vargas, A., and Yasunari, T. J.: Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition, Atmos. Chem. Phys., 12, 2313–2343, <a href="http://dx.doi.org/10.5194/acp-12-2313-2012">https://doi.org/10.5194/acp-12-2313-2012</a>, 2012.

Sundermeyer, M. A. and Price, J. F.: Lateral mixing and the North Atlantic Tracer Release Experiment: Observations and numerical simulations of Lagrangian particles and a passive tracer, J. Geophys. Res., 103, 21481–21497, 1998.

Torgersen, T., DeAngelo, E., and O'Donnell, J.: Calculations of horizontal mixing rates using 222Rn and the controls on hypoxia in Western Long Island Sound, Estuaries, 20, 328–345, 1997.

Tsumune, T., Tsubono, T., Aoyama, M., and Hirose, K.: Distribution of oceanic 137Cs from the Fukushima Dai-ichi Nuclear Power Plant simulated numerically by a regional ocean model, J. Environ. Radioactivity, <a href="http://dx.doi.org/10.1016/j.jenvrad.2011.10.007">https://doi.org/10.1016/j.jenvrad.2011.10.007</a>, in press, 2012.

Uchida, H., Imawaki, S., and Hu, J.-H.: Comparison of Kuroshio surface velocities derived from satellite altimeter and drifting buoy data, J. Oceanogr., 54, 115–122, 1998.

Uppala, S. M., Kallberg, P. W., Simmons, A. J., Andrae, U., Bechtold, V. D., Fiorino, M., Gibson, J. K., Haseler, J., Hernandez, A., Kelly, G. A., Li, X., Onogi, K., Saarinen, S., Sokka, N., Allan, R. P., Andersson, E., Arpe, K., Balmaseda, M. A., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Caires, S., Chevallier, F., Dethof, A., Dragosavac, M., Fisher, M., Fuentes, M., Hagemann, S., Holm, E., Hoskins, B. J., Isaksen, L., Janssen, P. A. E. M., Jenne, R., McNally, A. P., Mahfouf, J.-F., Morcrette, J.-J., Rayner, N. A., Saunders, R. W., Simon, P., Sterl, A., Trenberth, K. E., Untch, A., Vasiljevic, D., Viterbo, P., and Woollen, J.: The ERA-40 re-analysis, Q. J. Roy. Meteorol. Soc., 131, 2961–3012, <a href="http://dx.doi.org/10.1256/qj.04.176">https://doi.org/10.1256/qj.04.176</a>, 2005.

Yasuda, I., Okuda, K., and Shimizu, Y.: Distribution and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio Interfrontal Zone, J. Phys. Oceanogr., 26, 448–465, 1995.

Zhai, X. and Greatbatch, R. J.: Inferring the eddy-induced diffusivity for heat in the surface mixed layer using satellite data, Geophys. Res. Lett., 33, L24607, <a href="http://dx.doi.org/10.1029/2006GL027875">https://doi.org/10.1029/2006GL027875</a>, 2006.