Abstract
Coastal marginal seas and estuaries are generally dumpsites for wastewater from sewage and power plants. For an urgent assessment of dilution and dispersal of toxic materials due to accidental leakage, we develop an offline passive tracer model by exploiting oceanic reanalysis products and analyze differences in spatiotemporal variability of the leaked tracers in an estuary and a continental shelf margin on the Pacific side of Japan. In the estuary, the northeastward through flow affects the dispersal, while the month-long transport is dominated rather by inter-seasonal variability of wind-driven Ekman flow and counter-clockwise local circulations associated with the cold-dome density structure. On the marginal coast, the Kuroshio and resultant secondary recirculation readily entrain the tracer, leading to immediate transport mostly in the alongshore direction. The seasonal difference in the tracer dispersal is apparent such as sporadic offshore tracer eruption episodes, depending on the locations of the Kuroshio path.
