Transient Attracting Profiles in the Great Pacific Garbage Patch

Anthropogenic impact on the ocean and marine wildlife has never been as pointless as marine debris. Nevertheless, great efforts must be taken to estimate pathways and accumulation zones of marine litter in order to clean the most polluted areas of the sea. The present study intends to introduce a modern hydrodynamical concept to this debate. TRansient Attracting Profiles (TRAPs) act like short-term attractors on the ocean surface and have shown their potential to predict pathways of material transport in previous experiments. Here, I explore the occurrence of these profiles in the North Pacific subtropical gyre, a large-scale convergence zone that is known to entail a major accumulation region for floating debris, the Great Pacific Garbage Patch. There, I compute TRAPs upon daily snapshots of near-surface geostrophic velocity and create an unprecedented large dataset of approximately 4.5 million TRAP objects. With this record, I am able to provide a first characterisation of these structures at the mesoscale. I study their propagation, evaluate their persistency and uncover a driving mechanism behind the formation of TRAPs. Analysing their impact on nearby floating drifters allows me to reveal a signature of hyperbolic transport around these structures. I show that drogued drifters take around 7 days and undrogued ones around 5 days to pass by a TRAP, suggesting that these structures are most likely to organise transport if they are persistent. Throughout the thesis, I present a series of such findings that can be of particular interest to offshore cleanup operators.