Modelagem numérica da constituição e dinâmica da corrente norte do Brasil

Abstract

The North Brazil Current (NBC) is a western boundary current of the Atlantic Ocean that plays a key role in interhemispheric communication. This current is formed by the contribution of both the North Brazil Subcurrent (NBS), originating from a southern branch of the South Equatorial Current (SECs) around 15°S, and the central branch of the South Equatorial Current (SECc), approximately between 2°S and 4°N. Despite its relevance, there are still gaps in the literature regarding the quantification of these contributions and the dynamics associated with the formation of the NBC. Therefore, the present study aimed to analyze the dynamics and constitution of the NBC through numerical modeling. One tool used was OpenDrift, a software package designed for modeling the trajectories of particles and substances in the ocean. The backward method (regression in time) was applied, which allows tracing the origin of one or more particles. For model input, current data from Copernicus Marine Data were used, based on a daily reanalysis dataset, considering the period from 1993 to 2021 for generating current maps and from 2024 to 2025 for particle dispersion maps. The study area was delimited by the coordinates 55°W to 25°W and 20°S to 15°N, encompassing the distribution and influence region of the Brazilian North Atlantic Convergence (BNCC). For the construction of current maps, the temporal average of the entire available period (1993–2021) was used, totaling 28 years of data. For the particle dispersion maps, the period adopted moderately reflects the seasonality of the BNCC, with simulations performed between February and June 2024, a period of lower current intensity, and between July 2024 and January 2025, a period characterized by higher intensity. The particle launch point was defined in the approximate regions of 46°W and 2°S, in the terminal region of influence of the North Brazil Current (NBC). Reverse simulations performed at three depth ranges (0–50 m, 50–150 m, and 150–250 m) indicated that, at the surface, the CSEc plays a primary role in the formation of the NBC. Between 50 and 150 m, a significant increase in the subsurface transport of the North Brazil Current (NBC) is observed, while between 150 and 250 m the dynamics of the NBC are mainly responsible for the formation of the NBC. The limitations of the study are associated with the dependence on the quality of the data used. Even so, the results obtained were overwhelming, confirming the vision of the backward method and OpenDrift for particle tracking, as well as its application in the study of the dynamics and constitution of the North Brazil Current.