Morphological Characteristics of an Open Shelf Ridge at Rio Grande do Norte Continental Shelf, NE Brazil.

Cabral, A.P. and Noernberg, M.A., 2024. Morphological characteristics of an open shelf ridge at Rio Grande do Norte continental shelf, NE Brazil. Journal of Coastal Research, 40(6), 1166–1181. Charlotte (North Carolina), ISSN 0749-0208. This paper describes for the first time the occurrence of an open shelf ridge (OSR) in the South Atlantic Ocean, evidencing morphological differences with respect to occurrences in other regions. The unique configuration of this OSR derives from the characteristics of the shallow continental shelf frontal to the Calcanhar Cape, Rio Grande do Norte State, Brazil, where it is located. It is a shallow, narrow, stepped shelf with an escarpment corresponding to a drowned shoreline around the 35 m isobath. There are extensive siliciclastic and carbonate sand deposits, sand ribbons, subaqueous dune fields, coral reefs, and calcareous algae patches. The high transparency of the water allows the use of multitemporal optical satellite images from remote sensors in the bathymetric modeling and morphodynamic description, in conjunction with echo sounder surveys, in situ sampling, and modeling. The metocean conditions of the region were determined from current and wind data obtained in situ, as well as data from the Hybrid Coordinate Ocean Model (HYCOM) and Regional Ocean Modeling System (ROMS) numerical models. Combining these data allowed the identification, characterization, and analysis of the metocean patterns over the OSR. Superimposed onto the OSR, there is a field of asymmetric subaqueous dunes transverse to the ridge axis with wavelengths between 150 m and 2 km and heights between 2.5 m and 9 m, with a tendency for sediment transport offshore northwestward of the OSR crest. The synergistic effect of the dominant NE winds and the North Brazil Current with tidal currents drives the main metocean forcings. The hydrodynamic pattern for the main sedimentary deposit areas is described, and the effect of the OSR on general subaqueous dune field configuration is presented. [ABSTRACT FROM AUTHOR]