Simulation of dispersion of Cs in the ocean discharged from the Fukushima Dai-ichi Nuclear Power Plant

Kawamura, Hideyuki  ; Kobayashi, Takuya ; Furuno, Akiko   ; Usui, Norihisa*; Kamachi, Masafumi*

Numerical experiments on oceanic dispersion of Cs discharged from the Fukushima Dai-ichi Nuclear Power Plant were carried out with an oceanic dispersion model SEA-GEARN developed in Japan Atomic Energy Agency. High quality oceanic reanalysis data was input to the SEA-GEARN, which was calculated by MOVE system developed in Meteorological Research Institute, Japan Meteorological Agency. Although a large portion of results in the numerical experiments was good agreement with observed surface Cs concentration in the northern Pacific Ocean, the calculated concentration was underestimated in some area. It is suggested that Cs was distributed in the wide area of the northern Pacific Ocean due to deposition of Cs released into the atmosphere, which concentration was low on the whole. On the other hand, Cs directly discharged into the ocean was carried to the east along the Kuroshio extension dispersing by mesoscale eddies.