Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima

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Video in TIB AV-Portal: Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima

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Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima
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2012
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English

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Abstract
A sequence of global ocean circulation models, with horizontal mesh sizes of 0.5°, 0.25° and 0.1°, are used to estimate the long-term dispersion by ocean currents and mesoscale eddies of a slowly decaying tracer (half-life of 30 years, comparable to that of 137Cs) from the local waters off the Fukushima Dai-ichi Nuclear Power Plants. The tracer was continuously injected into the coastal waters over some weeks; its subsequent spreading and dilution in the Pacific Ocean was then simulated for 10 years. The simulations do not include any data assimilation, and thus, do not account for the actual state of the local ocean currents during the release of highly contaminated water from the damaged plants in March–April 2011. An ensemble differing in initial current distributions illustrates their importance for the tracer patterns evolving during the first months, but suggests a minor relevance for the large-scale tracer distributions after 2–3 years. By then the tracer cloud has penetrated to depths of more than 400 m, spanning the western and central North Pacific between 25°N and 55°N, leading to a rapid dilution of concentrations. The rate of dilution declines in the following years, while the main tracer patch propagates eastward across the Pacific Ocean, reaching the coastal waters of North America after about 5–6 years. Tentatively assuming a value of 10 PBq for the net 137Cs input during the first weeks after the Fukushima incident, the simulation suggests a rapid dilution of peak radioactivity values to about 10 Bq m−3 during the first two years, followed by a gradual decline to 1–2 Bq m−3 over the next 4–7 years. The total peak radioactivity levels would then still be about twice the pre-Fukushima values.
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Our study deals with 1 of the consequences of disastrous earthquake and subsequent tsunami that hit Japan in March 2011 cost by explosions and
now dance in the Fukushima-Daiichi nuclear power plants large amounts of radioactive material including long-living isotopes such as cesium-137 they're released into the environment contaminated waters and the Pacific Ocean by it was for a position and it sort of world in the weeks after the catastrophe
in this study we investigate the long-term fate of these waters in the Pacific Ocean using numerical model experiments the model simulates the ocean current over Hairer solution and thus captures much of the intense flows along the curfew to simulate the
dispersal of the contaminated water and ocean currents we use an idea trees of behaving like a guy with a half 30 years which injected into the coastal waters off Fukushima we want to emphasize that our approach is restricted to physical spreading and the smaller sample possible biological effects
for example adhesion of isotopes singing organic matter know the someone assimilate
any ocean data that we do not account for the actual state of the local currents at the time release however the initial state turned out to be of minor importance for the trace spreading after 2 to 3 years the following animation
shows spread of all die at the ocean surface the color represents the concentration of the tracer relative to the initial concentration in because the area of Fukushima at the end the injection period the trace and waits the highly energetic curfew machine within the 1st weeks after the release and starts from memory
only due to guineas dominating the flow field in this area after 1 year maximum concentrations on you by 2 orders of magnitude and already crossed the daytime further heading east the southern edge of the trace plot bridges the hawaiian islands after about 2 years whether knowledge has begun to enter the Bering Sea meanwhile concentrations near Japan has been dropping significantly due to replace them by less contaminated water through a few separating the main clause into a northern and a southern part after 4 years the maximum concentration has struck by 3 orders of magnitude in the antennal lobe Pacific is filled with a certain amount of tracer when the peak concentration reaches the North American coast of about 5 to 6 years it has been diluted by 4 orders of magnitude the concentration levels from now on tend to homogenize over the entire basin
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