Vertical mixing strategies in the Opendrift platform: analytical solution and Random Walk scheme

Predicted scenarios for microplastic displacement in the ocean is still a challenging task, where particle trajectory evolution is based on stochastic strategies at each timestep. The Opendrift platform presents a microplastic trajectory evolution solution using two strategies for turbulent vertical mixing. This work simulated microplastic particles emission in the Rio de Janeiro region (Guanabara Bay) and observed its depth over one year. Attentive to subtle differences, a statistical analysis was proposed to observe how particles are affected by the strategies individually. The preliminary observations showed no significant modification on the surface, but the depth had important motion modification. A dispersion was observed in XY coordinates of each particle using statistical analysis. The results demonstrated significant individual movement of microplastic particles. This study encourages the need for a protocol to decide which strategy to be used in computational simulations so that monitoring tasks can have optimum efficiency.