The discovery of extremely high radiation levels in the ocean adjacent to the Fukushima plant is the latest development in the crisis. The measurement site is located several kilometers north of the reactors, yet the prevailing currents over the past week have been to the south. This suggests more widespread contamination of the coastal waters. And more contamination is threatened by the radiation cesspools adjacent to the ocean that are under scrutiny at the moment.
Fields from the real-time global ~6-10 km data-assimilating ocean models HYCOM and NCOM run by the Naval Research Laboratory are shown below. The currents are oriented so as to move contamination southward toward the swift Kuroshio western boundary current (at the southeast corner of the maps) that then channels waters northward. Fortunately the ocean is very efficient at mixing contaminants and it is expected that radiation would get substantially diluted along its path. But the intermittent nature of the releases makes it difficult to assess the magnitude of the problem. Colleagues at JAMSTEC in Yokohama are sampling the water at distances offshore and continue to provide more refined measurements in the near future.