[Source: Nature Geoscience, full page: (LINK). Abstract, edited.]
Dynamics and early post-tsunami evolution of floating marine debris near Fukushima DaiichiDynamics and early post-tsunami evolution of floating marine debris near Fukushima Daiichi
John Philip Matthews, Lev Ostrovsky, Yutaka Yoshikawa, Satoru Komori & Hitoshi Tamura
Nature Geoscience (2017) / doi:10.1038/ngeo2975
Received 23 February 2017 – Accepted 23 May 2017 – Published online 03 July 2017
The devastating tsunami triggered by the Tōhoku-Oki earthquake of 11 March 2011 caused a crisis at the Fukushima Daiichi nuclear power station where it overtopped the seawall defences. On retreating, the tsunami carried loose debris and wreckage seaward and marshalled buoyant material into extensive plumes. Widespread concern over the fate of these and numerous other Tōhoku tsunami depositions prompted attempts to simulate debris dispersion throughout the wider Pacific. However, the effects of locally perturbed wind and wave fields, active Langmuir circulation and current-induced attrition determine a complex and poorly understood morphology for large floating agglomerations. Here we show that the early post-tsunami evolution of marine-debris plumes near Fukushima Daiichi was also shaped by near-surface wind modifications that took place above relatively calm (lower surface roughness) waters covered by surface films derived from oil and other contaminants. High-spatial-resolution satellite tracking reveals faster-than-expected floating-debris motions and invigorated plume evolution within these regions, while numerical modelling of turbulent air flow over the low-drag, film-covered surface predicts typically metre-per-second wind strengthening at centimetric heights, sufficient to explain the observed debris-speed increases. Wind restructuring probably stimulates the dispersion of flotsam from both biological and anthropogenic sources throughout a global ocean of highly variable surface roughness.
Keywords: Tsunami; Earthquakes; Japan; Nuclear Events; Environmental Disasters; Environmental Pollution.