Session: 06-07-01 Metocean, Measurement and Data Interpretation

Submission Number: 156573

Impact of Wave-Induced Drift Amplification on the Dispersal of Plastics in the Great
Pacific Garbage Patch 

The Great Pacific Garbage Patch (GPGP) constitutes the largest area of floating plastic accumulation in the oceans [Lebreton et al., 2018]. Dispersal models are created to understand better the surface and vertical distribution of plastics in the oceans [Klink et al., 2022] to optimize the cleanup operation. These models account primarily for the sources of plastics (location and quantity) and their Lagrangian transport. The transport models include the sea-surface current, wind, and wave-induced drift contributions. As a first approximation, the contribution of the waves on the plastic transport is the Stokes drift [Onink et al., 2019], which corresponds to the wave-induced drift of a neutrally buoyant, infinitely small object. However, recent studies have shown that plastics’ size, shape, and density can impact their wave-induced drift, often amplifying this drift compared to the Stokes drift. To model this amplification, empirical correlations have been found in experimental and numerical studies [Calvert et al., 2021] [Rakotonirina et al., 2023]. The present study aims to first implement such correlations in the wave model WW3 by modifying the Stokes drift formulation using the directional wave energy spectrum components. This gives access to the wave-induced drift velocity components for different plastic characteristics and the nominal Stokes drift. As a second step, a 10-year regional wave model of the North-East Pacific Ocean bounding the GPGP is run, allowing for a first comparison of the impact of the wave-induced drift amplification on the velocity magnitudes and resulting circulation. Finally, the resulting drifts from the regional wave model are used in the ADVECT plastic dispersal model to compare the influence of the different resulting wave-induced drifts on regional plastic accumulation.

Presenting Author: Andriarimina Rakotonirina The Ocean Cleanup

Presenting Author Biography: Computational Scientist at The Ocean Cleanup, Rotterdam, The Netherlands for the past 5 years
2018-2020: Medior Scientist at Deltares, Delft, The Netherlands
2016-2018: Post-doc at the University of British Columbia, Canada in computational multiphase flow
PhD in Computational Physics at Ecole Normale Superieure de Lyon, France