Characteristics of drift and beaching of floating marine litter in the Japan Sea are examined numerically
using the reanalysis data of the Japan Sea Forecasting System of Kyushu University. The residence time of
model marine litter deployed uniformly over the surface of the Japan Sea strongly depends on the buoyancy
ratio. However, almost all litter beaches or flows out through straits within 3 years. Experiments
with inputs of litter imposed at large cities and the Tsushima Straits as well as river basins of the Japan
Sea exhibit a good agreement with beach surveys with regard to country ratios of beached litter along the
Japanese coast in cases of lighters. In a case of lighter, almost all lighters originating from Japan beach
along the Japanese coast, while almost all lighters originating from a country surrounding the Japan
Sea except Japan beach along the coast of that country and the Japanese coast