Validation of a Lagrangian model for large-scale macroplastic tracer transport using mussel-peg in NW Spain (Ría de Arousa)

Marine debris is a growing problem in recent years due to population growth around the world. The incorrect management of plastic waste causes these bodies reach the seas and oceans, becoming a worldwide problem. Once they reach the seas and oceans, they begin a long period of degradation, moving from a macro state (plastics whose diameter is greater than 0.5 cm) to a micro state (diameter less than 0.5 cm). The microplastics spread throughout the oceans, entering the food chain of marine species and, subsequently, of humans. Therefore, it is important to stop the problem while it remains at the macroscale. In this work, a validation of a recently developed Lagrangian computational model to track the movement of macro plastics in seas and oceans is presented. This validation is performed on a regional scale, in the Ría de Arousa, one of the most important estuaries for mussel cultivation in northwestern Spain. During mussel cultivation in rafts, a type of floating plastic stick are released, the mussel-pegs. The potential of this study is that we can compare the accumulation results of the model with the accumulation data collected on the Galician beaches. In a general framework, the influence of wind on the spatial distribution of the accumulations given by the model was observed. For the monitoring data, similar results were found for the accumulation trends over the entire total period. For the monthly representation, some discrepancies were observed. These differences can be attributed to particular synoptic situations, poor reproduction of the coastline or to the very orientation of the study area with respect to the intertidal dynamics.

Nonperfect mixing affects synchronization on a large number of chemical oscillators immersed in a chemically active time-dependent chaotic flow

The problem of synchronization of finite-size chemical oscillators described by active inertial particles is addressed for situations in which they are immersed in a reacting nonstationary chaotic flow. Active substances in the fluid will be modeled by Lagrangian particles closely following the fluid streamlines. Their interaction with the active inertial particles as well as the properties of the fluid dynamics will result in modifying the synchronization state of the chemical oscillators. This behavior is studied in terms of the exchange rate between the Lagrangian and inertial particles, and the finite-time Lyapunov exponents characterizing the flow. The coherence of the population of oscillators is determined by means of the order parameter introduced by Kuramoto. The different dynamics observed for the inertial particles (chemical oscillators) and Lagrangian particles (describing chemicals in the flow) lead to nonlinear interactions and patches of synchronized regions within the domain.

Mixing of spherical bubbles with time-dependent radius in incompressible flows

The motion of contracting and expanding bubbles in an incompressible chaotic flow is analyzed in terms of the finite-time Lyapunov exponents. The viscous forces acting on the bubble surface depend not only on the relative acceleration but also on the time dependence of the bubble volume, which is modeled by the Rayleigh-Plesset equation. The effect of bubble coalescence on the coherent structures that develop in the flow is studied using a simplified bubble merger model. Contraction and expansion of the bubbles is favored in the vicinity of the coherent structures. Time evolution of coalescence bubbles follows a Lévy distribution with an exponent that depends on the initial distance between bubbles. Mixing patterns were found to depend heavily on merging and on the time-dependent volume of the bubbles.

Lagrangian coherent structures along atmospheric rivers

We show that filamentous Atmospheric Rivers (ARs) over the Northern Atlantic Ocean are closely linked to attracting Lagrangian Coherent Structures (LCSs) in the large scale wind field. The detected LCSs represent lines of attraction in the evolving flow with a significant impact on all passive tracers. Using Finite-Time Lyapunov Exponents, we extract LCSs from a two-dimensional flow derived from water vapor flux of atmospheric reanalysis data and compare them to the three-dimensional LCS obtained from the wind flow. We correlate the typical filamentous water vapor patterns of ARs with LCSs and find that LCSs bound the filaments on the back side. Passive advective transport of water vapor in the AR from tropical latitudes is potentially possible.