Lagrangian Coherent Structures for Mapping Mesoscale Circulation in the Western Equatorial Atlantic
2025
Yuri Onça Prestes | Renan Peixoto Rosário | Marcelo Rollnic
Lagrangian Coherent Structures (LCSs) in the mesoscale circulation of the Western Equatorial Atlantic (WEA), a region governed by the North Brazil Current (NBC) and its retroflection, are analyzed. Observations from 63 surface drifters deployed between 2018 and 2019 were combined with ocean analysis/forecast fields. The Finite-Time Lyapunov Exponent (FTLE) was computed using 15- and 90-day integrations to identify transport barriers and persistent structures. FTLE ridges showed strong seasonal correspondence with drifter trajectories, with 34&ndash:74% of drifter positions lying within 0.25°: of attracting or repelling LCSs. Characteristic FTLE magnitudes reached ~0.3 d&minus:1, implying particle separation e-folding times of approximately 3.3 days. Spatial agreement between drifter-derived and model-based FTLE fields exhibited similar variability across seasons, with the highest correspondence during periods of intensified frontal activity. These results indicate that a substantial portion of the observed drifter motion follows or remains close to FTLE-defined pathways, supporting the robustness of the Lagrangian structures identified in the WEA. Overall, the study provides the first quantitative LCS-based characterization of mesoscale transport in this region, revealing recurrent eddies, instability zones, and flow boundaries associated with the NBC system and its interaction with the North Equatorial Countercurrent.
Показать больше [+] Меньше [-]Библиографическая информация
Эту запись предоставил Multidisciplinary Digital Publishing Institute