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

Sergey V Prants,Michael Y Uleysky,Maxim V Budyansky

doi:10.5194/os-13-453-2017

Abstract

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.

Highlights

High tsunami waves after the Tohoku earthquake on 11 March 2011 damaged the cooling system of the Fukushima Nuclear Power Plant (FNPP)
Radionuclides were released from the FNPP through two major pathways: direct discharges of radioactive water and atmospheric deposition onto the North Pacific Ocean
Being motivated by the problem of identification of Fukushima-contaminated waters in the core and at the periphery of persistent mesoscale eddies in the area, we develop in this paper a specific Lagrangian technique designed to distinguish water masses of a different origin inside the eddies with a risk of being contaminated

Summary

Introduction

High tsunami waves after the Tohoku earthquake on 11 March 2011 damaged the cooling system of the Fukushima Nuclear Power Plant (FNPP). Due to lack of electricity, it was not possible to cool nuclear reactors and the fuel storage pools that caused numerous explosions at the FNPP (for details see Povinec et al, 2013). The Fukushima accident was classified at the maximum level of 7, similar to the Chernobyl accident which happened in 1986 in the former Soviet Union. Radionuclides were released from the FNPP through two major pathways: direct discharges of radioactive water and atmospheric deposition onto the North Pacific Ocean. Indirect estimation of that deposition is in the range 6.4–35 PBq (Kumamoto et al, 2014).

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Conclusion