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).