Investigation of Transport Paths and Times of Fukushima Nuclear Pollutants in the North Pacific Surface Using Surface Drifting Buoys

Based on the statistics of all surface drifting buoys of 1979-2011, the transport paths and times of Fukushima nuclear pollutants in the North Pacific surface have been studied. We examined the trajectories of surface drifting buoys that passed by the pre-defined source region of nuclear pollutants (totally 176 buoys) one by one to identify typical buoy trajectories in the North Pacific surface. Results show that there are three types of drifting trajectories for these 176 buoys. 80% (141) of 176 surface drifting buoys moved eastward along with Kuroshio and Kuroshio-extension currents, and only 20% moved southward. However, among 141 buoys that traveled along with the Kuroshio and Kuroshio-extension currents, only 13 finally reached the easternmost area of the North Pacific. Among the 35 buoys southward, only 5 turned their directions westward and entered the South China Sea through the Luzon Strait. Among the 5 buoys reaching the east coast of China, 1 buoy was found to travel with the Subtropical circulation branch at the central Pacific and formed its relatively longer trajectory and other 4 were brought into the South China Sea by local eddy-associated circulations.