Figure 9. Climatological Lagrangian Coherent Structures (cLCS) at the
western Caribbean Sea. Colors indicate the strength of attraction, with
red indicating the strongest attraction of nearby parcels; white
indicates isolated regions or low stirring activity. Panel (a) are the
annual and (b) the monthly cLCS for the Caribbean basin and the Yucatan
Peninsula region, respectively.
The persistence of strong cLCS throughout the year efficiently prevents
particles from reaching zone 2 without the influence of wind (Figure 8).
However, the isolation of region 2 changes with the wind: some particles
enter zone 2 with 1% windage, and considerably more enter zone 2 with
2% windage (Figure 8). The persistent Yucatan Current transport barrier
is debilitated when cLCS are computed with currents plus 1% windage,
and it is completely erased when cLCS are computed with currents plus
2% windage (Figure 10). Also notable is that with 2% windage, the zone
4 cLCS tend to converge while directing towards the Mexican coast from
about 84oW to 86oW in the vicinity
of 18oN, a feature absent in the cLCS computed from
only currents (Figure 10, cf. left and right panels). Independent
experiments using an instantaneous velocity from HYCOM by Lara-Hernández
et al. (2023) show that with 2% windage, trajectories reaching the
Mexican Caribbean coast move along these strongly attracting cLCS while
approaching the coast and then spread along the coastline (Text S2 and
figure S6). This constitutes an additional independent confirmation that
cLCS identifies and extracts the predominant transport patterns from the
instantaneous velocity.