5 Conclusions
This work identified the transport routes from the Equatorial Atlantic to the YP using Lagrangian experiments correlated to the cLCS. We used climatological currents from HYCOM and the most recurrent surface current patterns obtained from the climatological SOMs analysis for those experiments. The cLCS were calculated for the entire domain, and the transport barriers were determined, emphasizing the CS to interpret the distribution of particles in that area. We delimited ten strategic areas based on transport barriers, for which the area adjacent to the YP east coast was studied in detail.
We found that the SOMs reproduce the characteristic patterns of surface currents climate variability while the cLCS identified recurrent trajectories and persistent transport barriers, as confirmed with Lagrangian particle release experiments. The cLCS show a yearly persistence indicating mesoscale patterns in surface transport and a surface transport barrier isolating the continental shelf from circulation beyond the shelf break. Integrating these results with the Lagrangian experiments, we found that the cLCS determine particle trajectories since they function as transport pathways and transport barriers. When the cLCS act as transport barriers, particles are restrained from reaching specific areas unless there is windage to debilitate or completely erase the cLCS transport barriers due to currents.
Our results show that wind is a needed condition for particle confluence within different regions of the CS, either representative of the effect of windage or Stokes drift. For the regions of the Yucatan Channel, Honduras-Jamaica Central Channel, Honduras-Jamaica East Channel, and Jamaica-Haiti Channel, the 1% windage is necessary, while the 2% windage is needed for the particles to reach Quintana Roo, Mexico, Honduras-Jamaica West Channel, Southern Lesser Antilles, and Central America. From the Equatorial Atlantic region, the particles will take approximately four to eight months to reach the YP and will be influenced by the atmosphere phenomena and the space-time cLCS variability, being the Honduras-Jamaica West Channel, the main passage of particles transported towards the peninsula. The particles released during the autumn-winter months with a 1% windage are those that reach Quintana Roo, Mexico coasts in the spring of the following year, while the particles released in the spring months with a 2% windage are those that reach this zone in the summer months of the same year. The higher arrival of sargassum to the Mexican Caribbean in the summer months reaffirms the importance of the 2% windage for particles to arrive in this area.
This spatio-temporal particle distribution is similar whether using the HYCOM climatological data or the current patterns obtained with the SOMs. In addition to the hydrodynamics that determines the trajectory of particulate matter in the ocean, another important result is the representation of ocean climate by SOMs. The seasonality in the surface circulation is clearly illustrated by the BMUs distribution. From a numerical model perspective, the SOMs approach, together with the cLCS and its interaction with the large-scale dynamical atmospheric circulation features, can be applied to study and improve the representation of physical processes and approximate particulate matter transport and distribution on the sea surface. Atmospheric phenomena such as the easterly waves, anticyclonic cold fronts, Caribbean Low-Level Jet, the trade winds, and the ITCZ influence particle distribution, confluence, and aggregation. A more detailed study is required to determine the influence on windage of each of these phenomena.
Forecasting particle matter trajectories on the ocean still requires further studies to reproduce the transport accurately, incorporating other processes, such as degradation, growth, mortality, etc.. Nevertheless, this study is an advance in implementing different analysis methods of the interaction between different processes that determine ocean surface dynamics and their effect on particle transport.