Influência da fisiografia da margem continental do RN na circulação de correntes de contorno oeste

Abstract

Western boundary currents (WBC) affect the global ocean circulation, climate, and produce localized impact along their interactions with margins of ocean basins. This study analyses the response of WBCs over the interactions with corn of southwest Atlantic Equatorial Margin, particularly in the North and East sectors of Rio Grande do Norte (RN) on northeastern Brazil, based on geomorphological bathymetric characterization of the margin, in situ currents measurements on Northern shelf, and ocean currents simulation using the CROCO model. The RN margin provides a critical pathway to the WBC along the East and North sectors which are narrow and retracted shelf (up to 40 km offshore), and steep upper continental slopes (1:11), separated by the Touros High with low topographic gradient whose shelf length reaches 80 km in the offshore direction. The results indicate that the interaction of the Northern Brazilian Undercurrent (NBUC) with the RN northern margin physiography produces a recirculating current region due to velocity shear. Eddies and meanders are evident in February and August, with meander predominance in the latter month due to increased wind intensity eastward. The accelerated core position of NBUC (> 1.0 m.s - ¹) coincided with the upper slope region of Touros High in both months, confirming the interaction of the margin with the NBUC. In addition, the northern slope region showed the lowest velocity of the study area (~ 0.1m.s- ¹) due to the change of direction from the N-S to EW margin. This contrast resulted in the velocity shear that caused the vortices. Thus, the lower topographic gradient of the upper slope of the Touros High, the change of shelf direction and the intensity of the winds resulted in the formation of these features on a regional scale. The presence of these oceanic events near the northern shelf slope could explain the ecological and sedimentation differences in the Holocene between the eastern and northern shelves.