Numerical simulations of debris drift from the Great Japan Tsunami of 2011 and their verification with observational reports

• Published in: Marine pollution bulletin Vol. 132; pp. 5 - 25
• Main Authors: Maximenko, Nikolai, Hafner, Jan, Kamachi, Masafumi, MacFadyen, Amy
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2018; Elsevier BV
• Subjects: Boats; coasts; Computer simulation; Data analysis; Debris; Debris pathways; Debris reports; Detritus; Drift; Garbage; Hawaii; Japan; Marine debris drift; Marine pollution; Mathematical models; Microplastics; Model calibration/validation; Model-data comparison; New methods; Numerical modeling; Ocean models; Ocean surface circulation; Oceanography; plastics; Scaling; Sensitivity to windage; Solutions; Tsunami debris; Tsunamis; water pollution; Wind; Japan; Hawaii; Numerical modeling; Data analysis; Model calibration/validation; New methods; Marine debris drift; Tsunami debris; Debris pathways; Ocean surface circulation; Sensitivity to windage; Model-data comparison; Debris reports
• ISSN: 0025-326X; 1879-3363; 1879-3363
• DOI: 10.1016/j.marpolbul.2018.03.056

A suite of five ocean models is used to simulate the movement of floating debris generated by the Great Japan Tsunami of 2011. This debris was subject to differential wind and wave-induced motion relative to the ambient current (often termed “windage”) which is a function of the shape, size, and buoyancy of the individual debris items. Model solutions suggest that during the eastward drift across the North Pacific the debris became “stratified” by the wind so that objects with different windages took different paths: high windage items reached North America in large numbers the first year, medium windage items recirculated southwest toward Hawaii and Asia, and low windage items collected in the Subtropical Gyre, primarily in the so-called “garbage patch” area located northeast of Hawaii and known for high concentrations of microplastics. Numerous boats lost during the tsunami were later observed at sea and/or found on the west coast of North America: these observations are used to determine optimal windage values for scaling the model solutions. The initial number of boats set adrift during the tsunami is estimated at about 1000, while about 100 boats are projected to still float in year 2018 with an e-folding decay of 2 to 8 years. [Display omitted] •Five ocean models are used to simulate drift of debris from 2011 tsunami in Japan.•Model solutions are compared with reports from the ocean and from the US/Canada west coast.•At optimal windage models successfully reproduce observed influx peaks.•Initial number of tsunami boats is estimated to be about 1000.•Number of boats floating in 2018 is estimated to be about 100.