Radioactive contaminants have legally released for more than half a century from the nuclear plants at Sellafield UK and La Hague France. Scientists have recently begun to use the radioactive 129iodine (129I) as a way of tracking the movement of ocean currents.
The radioactivity levels found in the North Atlantic are extremely low and not considered dangerous.
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 and then flowing southward down. The continental slope of North America to Bermuda at depths below 3000 m said lead researcher Dr John N. Smith Bedford Institute of Oceanography, Canada.
Chlorofluorocarbons undergo ocean-atmosphere exchange
The research is part of the international GEOTRACES project. Aims to use geochemical markers to follow ocean currents. To provide precise estimates of transit times and mixing rates in the North Atlantic and Arctic Oceans. So far, the 129I measured as far south as Puerto Rico. But the researchers assume that it will continue to flow southward into the South Atlantic. Eventually spread throughout the global ocean.
These currents have previously been studied using dissolved Chlorofluorocarbons. The molecules used in fridges until banned in 1989.
However, CFCs undergo ocean-atmosphere exchange. The surface water is continually replenished with CFCs during the arctic leg of the journey. The 129I plume retains the initial imprint of its input history over a long period of years. Further, 129I is relatively easy to detect at extremely low levels. Using accelerator mass spectrometry methods which gives us a large measurement advantage in terms of the signal to noise ratio.
Since we know exactly where the 129I comes from and when it entered the ocean, for the first time we can be absolutely sure that detecting an atom in a particular place is as a specific result of the currents.”
The advantage of using 129I as transient tracer in oceanography. The long half-life (15.7 My) of this isotope compared to the circulation times. The fact that largely soluble in seawater. Now, major efforts devoted to find other artificial radionuclides with similar sources and behavior than 129I, 236U, 237Np.