Quantifying the influence of submesoscale processes on measured transport of floating plastic in the Great Pacific Garbage Patch

Abstract

The Great Pacific Garbage Patch (GPGP) is known for accumulating floating plastic, but little is known on the dominating mechanisms that form its heterogeneity. Submesoscale processes are likely the main drivers of such heterogeneity, especially if their effect on transport is object-specific. This hypothesis is investigated by analysing shipboard remote sensing and metocean data. By developing a Particle Tracking Velocimetry (PTV) methodology, floating plastic’s velocities are derived from GoPro and drone data collected during The Ocean Cleanup’s operational and research campaigns. Research findings show that surface currents, without additional forcings, cannot fully account for more than half of the variance in floating plastic transport within the North-West region of the GPGP. This suggests that leeway, an important factor in floating plastic transport, is likely a non-negligible component for most items in the area, with varying leeway rates observed across the sample. Furthermore, an analysis on submesoscale accumulation indicates that density fronts may contribute to creating heterogeneity at smaller scales. Notably, two episodes demonstrate higher floating plastic accumulation along density fronts than in the surrounding environment. In summary, this study sheds light on the crucial role of submesoscale processes in shaping the heterogeneity of the Great Pacific Garbage Patch. Understanding these mechanisms can lead to more effective strategies for mitigating plastic pollution and its environmental impacts.