Flow-topography and biophysical interactions in a continental margin in the southwestern tropical atlantic

Abstract

This work investigates flow-topography interactions (FTIs) and the resulting biophysical interactions (BPI) in the Southwestern Tropical Atlantic (SWTA). Using a combination of hydrodynamic data, temperature time-series analysis, and ecosystemic acoustic data recorded in the Southern Pernambuco Continental Margin, the research offers an integrated understanding of the region's dynamic processes. Chapter 3 examines the shelf-break dynamics in the SWTA, using data from the Multiple Rectangles Transect (MRT) experiment. The analysis revealed the importance of tidal forcing to cross-shelf current variability and its possible impacts on the previously reported uplift in SBS. The role of the North Brazil Undercurrent (NBUC) as the main driver of the uplift was also highlighted, particularly during periods of increased current velocity. Chapter 4 focuses on biological interactions along the continental slope in the SWTA, examining how the NBUC influences the distribution of micronekton (e.g., Myctophidae), particularly their diel vertical migration patterns. Data from MRT revealed that micronekton avoids areas of high current velocities while taking advantage of nutrient-rich waters. This chapter emphasizes how physical structures like the NBUC shape biological distributions, revealing important links between oceanographic processes and biological patterns in the region. Chapter 5 explores temperature variability within the Zieta submarine valley. Time-series analysis showed that variability in the valley is driven by external and remote forces, such as Rossby waves and internal wave propagation induced by wind shear. These processes significantly impact the entry of cooler waters into the valley and consequently onto the shelf, linking valley-slope interactions to broader SWTA dynamics. Through these analyses, this work provides a comprehensive understanding of FTI, offering new insights into how these processes influence ocean circulation, biological distributions, and marine ecosystem dynamics in a region that remains underexplored. The findings contribute to the growing body of knowledge on western boundary systems and underscore the need for continued monitoring and high-resolution studies to fully capture the temporal and spatial variability of FTI in low latitude regions.