Global ocean beaching pathways of surface drifters

While millions of metric tons of plastic enter the ocean each year, substantial amounts also continuously wash ashore. In this study we use observations from NOAA's Global Drifter Program to study the pathways by which surface-floating material leaves the open ocean and beaches along coastlines. We analyze trajectories of undrogued drifters as a proxy for buoyant plastic debris and find that approximately 20% of undrogued drifters beach within one year of losing their drogue. Beaching is highly heterogeneous, occurring in distinct coastal hotspots that are connected to large regions of the open ocean. By identifying coherent beaching watersheds, we show that a substantial portion of the ocean surface can produce beaching drifters. We further show that beaching probability depends strongly on coastal winds. For example, drifters are far more likely to beach under onshore winds, and beaching probability increases with the magnitude of the onshore wind component. These results provide insight into global beaching pathways and can be used to improve how beaching is parameterized in large-scale models of plastic debris.