The effect of ocean model tidal-forcing and spatial resolution on virtual particle dispersion and accumulation at the ocean surface

Understanding the pathways of floating material (e.g. larvae, plastics, oil) at the surface ocean is important to improve our knowledge on the surface circulation and for its ecological and environmental impacts.  For example, knowing where floating plastic and oil spills accumulate in the surface ocean can help ocean clean-up strategies.  One of the main methods of research is virtual particle simulations, which simulate the dispersion of floating material in the Ocean.  

 

Previous studies have tried to understand the surface dispersion and accumulation via these numerical simulations. To define the circulation, the velocity outputs of ocean general circulation models are needed. Oceanic models have improved in the past years, but many still do not fully represent the ocean dynamics at the fine-scales (below 100 km).  The spatial resolution of ocean models and whether they include a tidal-forcing are two important model parameterizations that can determine how well the ocean dynamics are represented at the fine-scales. In this study we try to answer: How do these model characteristics affect the dispersion and accumulation of virtual particles at the ocean surface?

 

To answer this, we use the ocean surface velocity outputs of different NEMO simulations to simulate the trajectories of virtual particles, and we evaluate the impact of different NEMO simulations’ spatial resolution and the presence or not of a tidal-forcing. As tidal-forcing has a big impact on the ocean model’s representation of internal tides and waves, we focus on a region where there is a high internal-tide signal: the Azores Islands.  We evaluate these impacts by looking at whether there is a difference in particles’ accumulation and dispersion in the different model scenarios.