Lagrangian simulation and tracking of the mesoscale eddies contaminated by Fukushima-derived radionuclides

Abstract. A Lagrangian methodology is developed to simulate, track, document and analyze the origin and history of water masses in ocean mesoscale features. It aims to distinguish whether water masses inside the mesoscale eddies originated from the main currents in the Kuroshio–Oyashio confluence zone. By computing trajectories for a large number of synthetic Lagrangian particles advected by the AVISO velocity field after the Fukushima accident, we identify and track the mesoscale eddies which were sampled in the cruises in 2011 and 2012 and estimate their risk of being contaminated by Fukushima-derived radionuclides. The simulated results are compared with in situ measurements, showing a good qualitative correspondence.