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90Sr and 137Cs as tracers of oceanic eddies in the sea of Japan/East sea

Hirose, Katsumi, Povinec, Pavel P.
Journal of environmental radioactivity 2020 v.216 pp. 106179
cesium radioisotopes, diffusivity, models, radioactivity, strontium, temporal variation, tracer techniques, Sea of Japan
Vertical distributions of ⁹⁰Sr and ¹³⁷Cs in Sea of Japan/East Sea (SOJ/ES) water in the period of 1977–2010 exhibited a typical diffusion shape with surface/subsurface maxima and decreasing values with increasing depth. Apparent vertical diffusion coefficients (AVDCs) and apparent initial surface fluxes (AIFs) of ⁹⁰Sr and ¹³⁷Cs, which were estimated using a curve-fitting method from a vertical diffusion model, showed temporal and spatial variability. A diffusion depth introduced for understanding of vertical movements of ⁹⁰Sr and ¹³⁷Cs in the SOJ/ES well correlated with corresponding AIFs, suggesting that spatial variations of the ⁹⁰Sr and ¹³⁷Cs inventories have been governed by oceanic conditions such as changes in AVDCs, which may be related with eddy field, characterizing the SOJ/ES. The temporal changes of the AVDCs suggest that the production of eddies increased during the 2000s comparing with that in the 1990s. These observations represent the first applications of radionuclides as tracers in production of oceanic eddies.