| Summary: | Detailing the distribution of past and future plastic debris in the marine environment has become a pressing challenge. Plastic pollution poses a potential threat to marine organisms and the marine environment as a whole. Previous studies using Lagrangian particle models have identified five garbage patches within subtropical ocean gyres, with the possibility of a sixth garbage patch within the Barents Sea. We present the first coarse resolution three-dimensional plastic distribution model to use an Eulerian approach. It considers seven plastic components, three of them buoyant and four non-buoyant, based upon real world plastic types. Our control results support the observations of positively buoyant plastic accumulations within the five garbage patches. However, there is no evidence of a sixth garbage patch in the Barents Sea. Meanwhile, our simulations reveal previously unreported accumulations of plastic in the East Siberian Sea and the Gulf of Guinea. The negatively buoyant plastic tends to accumulate within the deepest regions of the sea floor, loosely following the bathymetry. In two further experiments, we introduce idealised plastic removal rates to simulate the proportion of plastics that are sequestered within sediments once they reach the sea floor. The results of the simulations show that substantial quantities of plastic debris are subject to vertical transport in the ocean and are therefore present throughout the water column as well as on the sea floor. A final experiment, focusing solely on neutrally buoyant plastics, shows the potentially ubiquitous presence of small micro- and nanoplastics in the water column.
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