3.2.1 North Equatorial Atlantic without wind
To understand the surface currents’ Lagrangian transport, we used surface current velocity data to integrate the trajectories of particles released each third day and looked at the annual accumulated density of particles (Figure 4). When released between June and November, the distribution of particles shows that they tend to remain outside the CS and move towards the northeast. Notably, during this period, particles released in June and July remain in the NERR, and there is no significant increase in particle density in the North Equatorial Atlantic (NEA) areas. For particles released in September to November, the particles that can enter the CS leave to the North Atlantic by the northern arc of the Lesser Antilles. In contrast, particles released between December and May enter the CS, and while some leave to the North Atlantic, those remaining lead to the maximum particle density within the CS. This maximum density is located in the Lesser Antilles and the southern region of the Great Antilles.
The displacement and distribution of particles are associated with the ocean currents’ seasonality (Athié et al., 2020; De Souza & Robinson, 2004; Holt & Proctor, 2008) and, therefore, with the cLCS location (Figure 2). Analyzing the particle distribution, we found that particles take approximately 8 to 10 months to reach Florida from the Equatorial Atlantic. We also found that particles reach the Yucatan Peninsula (YP) and the GoM in about 6-7 months when released between October and January (Figure 4). Between May and August, the particles are spatially limited about 150 km offshore from Brazil to the YP, corresponding with the months the cLCS intensifies (Figures S2 in Supplementary Information and 4). Considering that cLCS have been shown to identify critical oceanic kinematics aptly, the cross-cLCS transport is often limited, and particle attraction causes flow along cLCS (Duran et al., 2018), our findings confirm that the cLCS act as transport routes and hydrodynamic barriers, limiting the movement of particles towards the coast. This highlights the influence of the continental shelf on ocean dynamics, where the transport is constrained not only by bathymetry but also by the Earth’s rotation, leading currents to move along isobaths and inhibiting flow from crossing isobaths (vorticity conservation) (Brink, 2016).