Radioactive Iodine Detected Near Bermuda

August 23, 2017

Radioactive iodine from nuclear reprocessing plants in the United Kingdom and France has been detected in the ocean near Bermuda, with researchers saying they “believe the radioactivity levels are extremely low and present no danger.”

A BBC story said “Radioactive iodine from nuclear reprocessing plants in the UK and France has been detected deep in the waters near Bermuda.

“Scientists say the contaminants take a circuitous route travelling via the Arctic Ocean and down past Greenland. Researchers believe the radioactivity levels are extremely low and present no danger.

“However, scientists can use the iodine to accurately map the currents that transport greenhouse gases.

“One scientific consequence that arose from the testing of nuclear bombs in the atmosphere in the 1950s was that their radioactive fallout provided a powerful global tracer of water circulation and deep-ocean ventilation.

“Other sources of radioactive material for scientists to track water movements have been the nuclear reprocessing plants at Sellafield in the UK and at La Hague in France.

“Contaminants have been legally released from these sites for more than 50 years. One in particular, Iodine-129 [129I], has been very useful for scientists tracing the ocean currents that help pull down greenhouse gases into the waters.

“What we have found is that by tracing radioactive iodine released into the seas off the UK and France, we have been able to confirm how the deep ocean currents flow in the North Atlantic,” said lead researcher Dr John Smith from the Bedford Institute of Oceanography, in Canada.

“This is the first study to show precise and continuous tracking of Atlantic water flowing northward into the Arctic Ocean off Norway, circulating around the arctic basins and returning to the Nordic seas in what we call the ‘Arctic loop’, and then flowing southward down the continental slope of North America to Bermuda at depths below 3000 metres.

“Scientists have used other molecules as tracers, specifically chlorofluorocarbons that were once used in refrigeration. But 129I, which has a half-life of 15.7 millions years, retains the initial imprint of its input history over a long period of time.

“Another advantage for researchers is that 129I is relatively easy to detect at extremely low levels.

“In many ways this is a bit like the old ‘stick in a stream’ game we used to play as kids,” said Dr Smith.

“What people call ‘pooh sticks’ in England, where you would drop a buoyant object in the water and observe where it comes out. Of course, it would be much better if these markers were not in the ocean at all, but they are, and we can use them to do some important environmental science.”

“This new study is part of an international project called GEOTRACES that uses geochemical markers to follow ocean currents.

John N. Smith, Bedford Institute of Oceanography, Fisheries and Oceans Canada in Dartmouth, Nova Scotia, Canada, said, “Since their introduction into the environment from atmospheric nuclear weapons tests in the 1950s, artificial radionuclides have proven to be useful global tracers of water circulation and deep ocean ventilation.

“Skilful applications of radionuclide tracers are favoured by strong, rapidly time varying sources and accurate knowledge of their input functions, conditions that are satisfied by discharges from the Sellafield, UK and La Hague, France nuclear fuel reprocessing plants and the 2011 Fukushima, Japan nuclear reactor accident.

“Discharges of 129I and 137Cs from European reprocessing plants are transported through the Nordic Seas and Arctic Ocean and are then injected into Denmark Strait Overflow Water south of Greenland which flows equatorward and supplies the deep waters of the North Atlantic.

“During the past 35 years, time series measurements along this northern arm of the global overturning circulation have revealed that radioactive tracers from the North Sea take about 10 years to reach the North Pole, an additional 5 years to return to the Nordic and Labrador Seas and a further 8 years to reach deep ocean locations off Bermuda.

“Recent measuirements of 129I in the Arctic and North Atlantic Oceans have been used in conjunction with new models based on transit time distributions [TTDs] to provide more precise estimates of transit times and mixing rates for flow along deep ocean circulation pathways.

“Results from the 2015 GEOTRACES studies in the Canada Basin reveal that Atlantic Water flow through the western arctic basins has a strong advective component while downstream flow in the Nordic and Labrador Seas and Deep Western Boundary Current on Line W off Cape Cod reflects significant modification of the same water masses through mixing.

“129I is particularly well suited for studying global ocean circulation, because unlike gas ventilation tracers that undergo ocean atmosphere exchange in surface waters, 129I levels undergo little modification other than by mixing once 129I is discharged into the ocean.”

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  1. zzzzz says:

    Fascinating: Bernews, thank you for publishing this.