3.2.2 North Equatorial Atlantic with wind
Previous studies have shown the importance of wind over surface currents (Allshouse et al., 2017; Clarke & Van Gorder, 2018) related to the transport of particles (Johns et al., 2020; Kwon et al., 2019; Laxague et al., 2018; Lodise et al., 2019), we proceeded to include wind in the Lagrangian experiments. Lumpkin & Pazos (2007) found that near-surface drifters have a windage factor effect of ~1% in the wind direction, while drifters at 15 m depth have a windage effect factor one order of magnitude smaller. Later, Lumpkin et al. (2013) showed that this difference could be attributed to the combination of the surface wind drag, the vertical shear of wind-driven currents above 15 m depth, and the wave-induced Stokes drift, which was shown to be important by Clarke & Van Gorder (2018). Here we included the direct wind momentum transfer to floating material as windage (Putman et al., 2020) by adding 1% of the wind. To incorporate the effect of Stokes drift, as Clarke & Van Gorder (2018) suggested from analyzing large times series of observations, we included an additional 1% of the wind to the current velocity. As such, we study wind’s influence at the surface by adding 1% of the wind and, in other experiments, by adding 2% of the wind. The latter may represent the effect of strong windage or the joint effect of windage and Stokes drift. Similar approximations have been applied by Putman et al. (2020), Johns et al. (2020), and Kwon et al. (2019).
Our results show that 1% windage is enough for the particles to remain in the CC and reach the GoM independently of the particle release month (Figure 6a). The 1% windage allows the particles to either approach the strong cLCS or to cross them so that they are advected towards the CS and follow their path into the GoM. The largest accumulation of particles near the northern CS and YP coast occurs for particles released between October and March, when the particles also reach the Florida coast, including the US Atlantic coast. The results suggest that the wind is a key factor for accumulating particles in coastal regions and that cLCS act as transport paths that cause particles to travel greater distances. Important to notice is that the particles released from September to January start entering the region of Central America, particularly the coastal zone of Costa Rica, Panama, and Colombia.