The hydrodynamics of a low-latitude submarine canyon: implications for circulation pattern and dispersion of suspended particles

Submarine canyons provide a conduit for continental shelf-slope exchange through topographically induced processes, such as downward and upward flows, which impact the ecosystems nearby, natural resources, and sedimentary processes. This paper aims to analyze the Natal Canyon hydrodynamics, in the Brazilian Northeast Margin, and its effects on the suspended particles. For this purpose, a simulation using the Coastal and Regional Ocean Community model was built and validated with in situ data. Furthermore, a 3D particle-tracking numerical experiment was built with the velocity field of the oceanic simulation using the Ichthyop model for 3 different positions: on the southern canyon’s rim, on the canyon’s head, and in the current pathway on slope. Circulation within the Natal Canyon is characterized by a semi-permanent anticyclonic pattern, which intensifies during periods of stronger boundary current flow. While this circulation promotes upward water movement, its effect is largely suppressed by the strong regional thermohaline stratification. In all scenarios simulated, the current is strong enough to carry most of the suspended particles (~95%) northward. Although the general westward canyon transport, the current is not enough strong to avoid entrapment of particles (~2%) into the canyon. A small part of the particles (<2%) reaches the middle shelf through the canyon’s head and the coastal current. The results indicate that the Natal Canyon dynamic is wind-driven and is favorable to downward flow. This context impacts the suspended particles and may explain the starved-shelf condition in low latitudes shelves as in the eastern margin of Rio Grande do Norte-Brazil. Therefore, the western boundary current interactions with the margin physiography and submarine canyons control the morpho-sedimentary conditions and affect ecosystems on the Brazilian eastern shelf