AsianScientist (Oct. 23, 2013) – The radioactive ocean plume from the 2011 Fukushima nuclear plant disaster will reach the US in 2014, according to a study published in the journal Deep Sea Research Part 1.
While atmospheric radiation was detected on the US west coast within days of the incident, the radioactive particles in the ocean plume (likely to be harmless) take longer to travel the same distance. Researchers from the Australian Research Council’s (ARC) Center of Excellence for Climate System Science used a range of ocean simulations to track the path of the radiation from the Fukushima incident. The models showed where it would likely travel through the world’s oceans for the next ten years.
“Observers on the west coast of the United States will be able to see a measurable increase in radioactive material three years after the event,” said the author of the study, Dr. Erik van Sebille. “However, people on those coastlines should not be concerned as the concentration of radioactive material quickly drops below World Health Organization’s (WHO) safety levels as soon as it leaves Japanese waters,” he said.
Two energetic currents off the Japanese coast – the Kuroshio Current and the Kurushio Extension – are primarily responsible for accelerating the dilution of the radioactive material, taking it well below WHO safety levels within four months.
Eddies and giant whirlpools – some tens of kilometers wide – and other currents in the open ocean continue this dilution process and direct the radioactive particles to different areas along the US west coast.
“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 another study author, Dr. Vincent Rossi.
“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 again along the southern Californian shelf,” he said.
Interestingly, the great majority of the radioactive material will stay in the North Pacific, with very little crossing south of the Equator in the first decade. Eventually over a number of decades, a measurable but otherwise harmless signature of the radiation will spread into other ocean basins, particularly the Indian and South Pacific oceans.
“Australia and other countries in the Southern Hemisphere will see little if any radioactive material in their coastal waters and certainly not at levels to cause concern,” said Dr. Sebille.
The article can be found at: Rossi V et al. (2013) Multi-decadal Projections Of Surface And Interior Pathways Of The Fukushima Cesium-137 Radioactive Plume.
Source: Adrift; Photo: Moondusty/Flickr/CC.
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