The radioactive ocean plume from the Fukushima nuclear plant disaster in 2011 is slowly drifting across the ocean, following the inevitable currents and tides of the Earth's waters. Now, scientists have discovered that this plume will reach U.S. shores within three years from the date of the incident. (Photo : Flickr/Mike Baird)

The radioactive ocean plume from the Fukushima nuclear plant disaster in 2011 is slowly drifting across the ocean, following the inevitable currents and tides of the Earth's waters. Now, scientists have discovered that this plume will reach U.S. shores within three years from the date of the incident.

Atmospheric radiation was detected on the U.S. west coast within days of the incident. Yet the radioactive particles in the ocean plume take significantly longer to travel the same distance. In order to find out exactly how long, though, researchers decided to perform a few calculations.

The scientists employed a range of ocean simulations in order to track the path of the radiation from the Fukushima incident.  After examining the data, the researchers were able to track where this plume would likely travel through the world's oceans for the next 10 years. More specifically, they discovered that the west coast of the U.S. will see a measurable increase in radioactive material about three years after the event. They also found that these concentrations of material, though, quickly drop below World Health Organization safety levels as soon as they leave Japanese waters.

The ocean itself is responsible for this drop in concentration. Two energetic currents, called the Kuroshio Current and the Kurushio Extension, accelerated the dilution of the radioactive material. Eddies and whirlpools continue this dilution process and direct the materials to different areas along the U.S. west coast rather than pushing it into one specific area.

"Although some uncertainties remain around the total amount released and the likely concentrations that would be observed, we have shown unambiguously that the contact with the north-west American coasts will not be identical everywhere," said Vincent Rossi, one of the researchers, in a news release. "Shelf waters north of 45°N will experience higher concentrations during a shorter period, when compared to the Californian coast. This late but prolonged exposure is due to the three-dimensional pathways of the plume. The plume will be forced down deeper into the ocean toward the subtropics before rising up against along the southern Californian shelf."

While quite a bit of the material will make it to California, though, most of it will stay in the North Pacific, with very little crossing south of the Equator in the first decade. Eventually, this material will spread into other ocean basins over a number of decades.

Want to see the plume for yourself? You can track the path of the radiation by clicking on an area of the ocean to examine how it's moving across the ocean. Check out the map here.

The findings are published in the journal Oceanographic Research Papers.