CoAuthors

Claudia Gloria Simionato ((1) Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias de la Atmósfera y los Océanos. Buenos Aires, Argentina. (2) CONICET – Universidad de Buenos Aires. Centro de Investigaciones del Mar y la Atmósfera (CIMA)., Argentina); Martín Saraceno ((1) Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias de la Atmósfera y los Océanos. Buenos Aires, Argentina. (2) CONICET – Universidad de Buenos Aires. Centro de Investigaciones del Mar y la Atmósfera (CIMA)., Argentina); Marisol Osman ((1) Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias de la Atmósfera y los Océanos. Buenos Aires, Argentina. (2) CONICET – Universidad de Buenos Aires. Centro de Investigaciones del Mar y la Atmósfera (CIMA)., Argentina); Leandro Baltasar Diaz ((1) Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias de la Atmósfera y los Océanos. Buenos Aires, Argentina. (2) CONICET – Universidad de Buenos Aires. Centro de Investigaciones del Mar y la Atmósfera (CIMA)., Argentina)

The present study focuses on the regional impacts that large scale perturbations propagating in the global ocean have upon the Southwestern Atlantic circulation. The analysis is based on the ocean reanalysis ORAP5.0 data, which extends from 1979 to 2013 and was satisfactorily validated in the region by Bodnariuk et al., (2021, 2022) based on altimetry data. In particular, the study addresses the influences of remote perturbations upon the variability of the Latitude of Separation of the Brazil Current (LSBC) and the exportations of shelf waters at the continental shelf-breaks of northern Argentina, Uruguay and southern Brazil (hereafter referred to as Northern Shelf). The LSBC, i.e. the northern boundary of the Confluence Region between the Brazil and Malvinas, presents variability at a wide range of timescales, ranging from high-frequency cycles to low-frequency interannual modulations that represent a large portion of the total variance. A statistical analysis based on Singular Spectrum Analysis (SSA) of the LSBC series allows the detection of different pseudo-periodicities that characterize its temporal variability on interannual timescales. Three pseudo-cycles of approximately 2, 4 and 10 years are directly associated to the interaction of the Brazil Current with incoming Rossby waves. These waves are identified based on correlation maps built upon LSBC pseudo-cycles to highlight only those propagating perturbations that force regional variability. Furthermore, propagating patterns are tracked to their respective sources to deepen the understanding of global oceanic teleconnections and identify their origins. Validation of Rossby waves presence and general characteristics is performed by comparing the abovementioned correlation maps with those built on the basis of satellite altimetry data. According to the results of the study, the origin is generally associated to characteristic processes that occur in each ocean basin and that have been considerably discussed in the literature, such as ENSO and the Indian Ocean Dipole. Remarkably, the propagating waves (first baroclinic mode) take many years to traverse and connect the different ocean basins, which suggests that the LSBC modulations could be potentially predicted. These modulations are suggested to be directly related to incoming Rossby waves that impact the Brazil Current transport upon interaction with the shelf-break. Transport changes, in turn, impacts the shelf water exportation by inducing displacements of the large-scale water exchange sites along the shelf-break of the Northern Shelf. Interannual modulation of water exportation might have major consequences in the fertilization of oceanic waters and consequently on biological activity in the area. A thorough understanding of the processes modulating water exchanges could potentially contribute to the administration of natural resources and fisheries in the region. Furthermore, it could also provide valuable clues to the remarkably large primary productivity observed in the Southwestern Atlantic Ocean. Further investigation of the water exchanges between the shelf and the ocean at higher resolution are envisaged in the near future based on SWOT altimetry data. This new dataset could significantly contribute to the study of regional dynamics, particularly the observation of submesoscale processes that have been reported to control water exchanges (e.g. local circulation around small-scale topographic indentations).



References

Bodnariuk, N., Simionato, C. G., Saraceno, M., Osman, M., & Diaz, L. B. (2021). Interannual
Variability of the Latitude of Separation of the Brazil Current: Teleconnections and ceanic ORossby Waves Propagation. Journal of Geophysical Research: Oceans.
https://doi.org/10.1029/2021jc017557

Bodnariuk, N., Simionato, C. G., Saraceno, M., Osman, M., & Diaz, L. B. (2022). Water exchanges between the Northern Argentinean Shelf and the open ocean on interannual timescales: remote influences. https://doi.org/10.1029/2022JC018517