Oceanic general circulation model for the assessment of the distribution of 137Cs in the world ocean

An Oceanic General Circulation Model (OGCM) incorporating advection and diffusion models for the calculation of the distribution of radionuclides in the global ocean has been developed. Calculations of 137Cs in seawater profiles were carried out using global and local fallout data from past atmospheric nuclear tests and compared with experimental data obtained from the 1960s to the 1990s at 152 sites, mainly in the Pacific and Atlantic Oceans, in order to verify the model and to find optimum horizontal and vertical diffusion coefficients. A reasonable agreement between the calculated and observed 137Cs water profiles was found using the values of 1.3×108 and 0.3 cm2 s−1 for the horizontal and vertical diffusion coefficients, respectively. It is expected that the developed model will be useful for the long-term environmental assessment of radioactive discharges from nuclear facilities on a global scale. This model also can be applied in the calculation of the dispersion of non-radioactive contaminants, which behave like conservative tracers in the open ocean.