1 Introduction
Ocean currents are a major factor in the movement of suspended material
over large distances along ocean basins. The conveyance of suspended
material by currents as a main transport mechanism is critical for
ecosystems as they determine the connectivity of some marine populations
inhabiting the benthic or pelagic environments (e.g., Bryan-Brown et
al., 2017; Sanvicente-Añorve et al., 2014, 2018). Ocean currents also
transport contaminant materials derived from anthropogenic activities
(Dow, 1999; Pohl et al., 2020; Zaborska et al., 2017), eventually
reaching the coast, accumulating in remote places, or sinking to the
ocean bottom. Considering the importance of currents in transporting
living and non-living suspended material, it is crucial to understand
their kinematics. For the Tropical Atlantic, different authors have
described the surface currents (Johns et al., 2014; Lumpkin & Garzoli,
2005; Müller-Karger et al., 1989), while others have characterized the
climatological surface currents from the western tropical Atlantic to
the Gulf of Mexico (GoM) (Andrade & Barton, 2000; Gordon, 1967; Johns
et al., 2002; Muller-Karger et al., 1988, 1995; Romanou et al., 2004;
Zavala-Hidalgo et al., 2014). Recently, studies have focused on
understanding the sargassum transport routes from the Equatorial
Atlantic through the Caribbean Sea (CS) and into the GoM (Athié et al.,
2020; Beron-Vera et al., 2022; Orfila et al., 2021; Ortiz-Royero et al.,
2013; Otero et al., 2016; Putman et al., 2018, 2020). This is due to the
emergence of a new sargassum generation area in the tropical Atlantic
(Gower et al., 2013; Wang & Hu, 2017), resulting in substantial
environmental, social, and economic effects across the Caribbean region.
Besides sargassum, understanding the currents system from Equatorial
Atlantic to the GoM is relevant for plastics (Law et al., 2010),
nutrients (Williams & Follows, 2003), and organisms (Sanvicente-Añorve
et al., 2019), as the results indicate the fundamental role of the North
Brazil and Guyana currents (Johns et al., 2014), establishing the
connectivity between the western Atlantic and the Caribbean
(Andrade-Canto & Beron-Vera, 2022; Muller-Karger et al., 1988, 1995).
The Equatorial Atlantic
to the GoM currents system has a clear seasonal variability. During the
summer and fall, a significant part of the North Brazil Current (NBC)
retroflects and merges into the eastward-flowing North Equatorial
Countercurrent (NEC), which then intensifies. In spring, the NEC weakens
and superficially reverses. In some cases, the NBC and the western
boundary current to the north intensify simultaneously, forming part of
the North Atlantic large-scale gyre moving northwestward to the CS
(Garzoli et al., 2003; Johns et al., 2003). The current dynamics in the
CS are dominated by a primary jet that forms the Caribbean Current (CC)
as water is transported through the southern region of the Lesser
Antilles by a boundary current along the South American coasts (Rhein et
al., 2005), continuing to flow northwestward through the CS on to the
Yucatan Channel. The southern CS has small recirculation gyres off
Panama and south of the Yucatan Channel interacting with the bathymetry,
while the slower northern jet is dominated by mesoscale anticyclones
(Chérubin & Richardson, 2007). In addition to ocean currents,
atmospheric forcing influences surface transport, partly determining the
trajectory of near-surface material (Johns et al., 2020; Müller-Karger
et al., 1989; Putman et al., 2018). The atmospheric variability in the
region is dominated mainly by the easterly winds, which in turn are
modulated by the Intertropical Convergence Zone (ITCZ) migration, cold
fronts’ arrival, and the Caribbean Low-Level Jet (CLLJ) variability.
This atmospheric dynamic results in two climatic seasons, a windier and
drier season from December to March and the wet season from August to
November, regulated by the location of the ITCZ. May-June and
September-October are considered a transition period between seasons
since easterlies tend to weaken, coinciding with the intensification and
bi-modal variability of the CLLJ (García-Martínez & Bollasina, 2020;
Hidalgo et al., 2015; Orfila et al., 2021).
While the mentioned
studies characterize the ocean currents system or the atmospheric
variability in the region, the interaction of wind, waves, and surface
currents dictate transport routes of floating matter in the ocean’s
surface layer. As such, this study aims to characterize sea-surface
current patterns and assess the effect of surface currents and wind
interaction on the displacement of floating particles. We utilized
Self-Organizing Maps (SOMs) and climatological Lagrangian Coherent
Structures (cLCS) to identify the primary transport routes and transport
barriers in the region stretching from the western tropical Atlantic to
the Central Subtropical Atlantic, including the entrance to the GoM and
the Yucatan Peninsula (YP). We used synthetic surface drifters to
compute the probability of arrival at select locations within the CS
with an emphasis on the eastern coast of the YP, where we also included
the effect of wind over the drifters. The results show how the windage
plays a key role in advecting particles to some areas along the CS but
also provide insight into using SOMs to represent climatological
conditions for particle dispersal. This paper is organized as follows:
section two describes the data and methods; section three presents the
results, describing preferential routes for different combinations of
wind and currents, persistent attraction zones and transport barriers,
and the modulation of transport barriers by the wind. We summarize our
main findings in section four.