Fate and 3D distribution of marine litter in the western Mediterranean basin from offshore to coast

This study presents a methodology aimed at advancing our understanding of plastic dispersion, accumulation, and stranding within the western Mediterranean basin. The approach is multi-scaled and employs the Ocean General Circulation Model NEMO coupled with the Lagrangian particle tracking simulator OceanParcels to simulate the 3D movement of plastic particles at large, mesoscale, and small scales. On a large scale, the methodology will examine the influence of major coherent current structures, such as the Northern Current to identify potential hotspots where plastics accumulate, strand, or settle on the seafloor and link them with climate indices. This large-scale perspective is essential to understand broad patterns of plastic distribution across the Mediterranean basin. Then, focusing on the mesoscale, plastic particles movement within an ocean eddy will be modelled, exploring the vertical and horizontal dynamics. This mesoscale analysis enables us to investigate how particles are trapped or redistributed within these features, shedding light on transport barriers effects. Lastly, the study narrows down to the small scale, where factors like wind and wave interactions are incorporated to enhance the model accuracy in simulating plastic and biomedia stranding events. This final stage will focus on biomedia (floating plastic discs used for wastewater treatment) stranding events to bridge model predictions with available observations from NGOs and citizen science efforts. The combined multi-scale approach will provide a comprehensive model for understanding plastic 3D dynamics from offshore to coast, enhancing targeted mitigation strategies in the Mediterranean Sea.