Figure 6. Lagrangian experiments results. According to the release month, the maps show the annual accumulated particle density using the HYCOM climatology, (a) with 1% and (b) 2% windage. The color indicates the accumulated particle density, and the gray line is the 200 m isobath.
We included a 2% windage to the Lagrangian experiments to approximate either strong windage or a combination of windage and Stokes drift (Clarke & Van Gorder, 2018). The results are shown in Figure 6b. We found that particles remain near the coastal zone from Brazil to the Lesser Antilles, covering the CS and reaching the GoM regardless of the release month. Under 1% windage, a high concentration of particles follows the LC between October to April. Still, under 2% windage, this stops occurring as the particles are advected further south before entering the LC. Nevertheless, a large concentration of particles reaches the northern coast of Mexico and Texas during March and April. Particles released between June and August with 2% windage remain in the NERR and leave the domain eastward, while those released from September to November enter the CS through the Lesser Antilles southern area, reaching the coasts of Nicaragua and the coasts of Central America. The particle’s distribution and trajectories are associated with seasonal atmospheric variability. The periods of maximum particle accumulation coincide with the latitudinal displacement of the ITCZ (Aliaga Nestares et al., 2022; Haffke et al., 2016; Henke et al., 2012; Skliris et al., 2022), which gives rise to significant wind variability in the study area. When the ITCZ is in its southernmost location (~3o N) from February to March, the wind intensifies in the Caribbean area, causing the particles to move towards the southern region of the Caribbean basin and on the NBC between October and January. This period corresponds to a weakening of the cCLS in the Caribbean (Figure S2 in Supplementary Information). On the other hand, during the summer months (June to September), the windage intensity decreases in the Caribbean due to a northern displacement of the ITCZ (~11o N), allowing the particles to advect towards the center and north of the Caribbean basin. This particle’s distribution is expected due to the change of direction of the trade winds (Orfila et al., 2021). During these months, the cLCS intensified in the Yucatan Channel, Honduras, Panama, Colombia, and Venezuela, as well as in the Lesser Antilles region (Figure S2 in Supplementary Information). It should be noted that with 2% wind, in addition to the particles that enter the Caribbean, the highest particle density is found in the NERR region.
When adding 1% or 2% windage in the Lagrangian experiments, we obtained similar results whether the currents were from the HYCOM climatology (Figure 6) or the SOMs patterns (Figure 7). These results indicate that using the current patterns obtained with the SOMs are an adequate approximation to the currents’ climatology, thus validating their use to calculate particle displacement, as suggested in Meza-Padilla et al. (2021). Comparing the results using 1% and 2% wind, we found that particles move from the Equatorial Atlantic to the CS. Some particles enter the GoM and exit through the Straits of Florida. It is observed that with 1% windage, the easterly winds displace the particles further south so that more particles enter the CS, covering the CS basin with the largest accumulation of particles near the Greater Antilles coast (Caribbean northern region). The 1% windage also allows particles to reach areas with intense cLCS, such as the Yucatan Current, where particles follow the LC and exit through the Florida Strait. When including 2% windage, particles are distributed further into the southern Caribbean region, where the cLCS lead to previously unreached areas, such as the Central America region. Also, including 2% windage results in stranded particles at the coast or allows them to leave areas with strong cLCS. This occurs in the western Caribbean, where particles are stranded before entering the Yucatan Current and into the LC, and those entering the LC are displaced into the western GoM.