Spread of Pollution from a Bottom Source in the Norwegian Sea

Simulations of the spread of radioactive contamination (RC) with cesium-137 (Cs-137) as a passive impurity were performed using the Institute of Numerical Mathematics Ocean Model (INMOM) to assess the radiation threat from the Komsomolets nuclear submarine (NS) on the northeastern slope of the Norwegian Sea at a depth of 1680 m caused by the possible leakage of radionuclides from the reactor compartment into the surrounding sea water. These simulations have shown that RC in the bottom layer generally spreads along the depth slope to the north and south of the source. Such a variability of the direction of RC transport is caused by the variability of the bottom current velocities, which is confirmed by the data of field measurements. As the distance from the source increases, the concentration of RC significantly decreases due to dilution in the surrounding waters. In the interior of the sea, the concentration is several orders of magnitude lower than in the source. The inflow of RC into surface waters due to turbulent mixing and convective motions of waters in the complex three-dimensional structure of circulation in the Norwegian Sea is simulated. It is shown that the excess of the surface concentration of RC over the bottom one observed in the measurements cannot be associated with emissions from the Komsomolets. The near-surface concentration of RC is most likely caused by the spread of RC from nuclear processing plants in northern Europe. In general, it has been shown that the currently possible RC from the Komsomolets does not exceed the background level of radioactive contamination of the waters of the Norwegian Sea.