Interannual Variability of the Latitude of Separation of the Brazil Current: Teleconnections and Oceanic Rossby Waves Propagation.

The latitude of separation of the Brazil Current (LSBC) variability is analyzed with a view to unveiling the physical mechanisms that modulate the turning point of the Brazil Current at low frequencies. The global ocean reanalysis ORAP5.0 spanning the period 1979–2013 is employed for this purpose. Three characteristic periodicities of the LSBC variability are found on the basis of a Singular Spectrum Analysis: 2, 4 and 10 years. Lagged sea surface height (SSH) correlation maps relate these modulations to Rossby wave propagation. According to these maps, the biennial signal might be triggered by the Atlantic Niño and the Indian Ocean Dipole. In the last case, SSH anomalies propagate around the southern tip of Africa, connecting the Indian and Atlantic oceans. Correlation maps suggest that the 4‐year signal is triggered by both the Atlantic Niño and the ENSO in the equatorial Pacific Ocean. The ENSO‐related anomalies travel through the Indonesian Throughflow along the western Australian coast, where Rossby waves are excited. These anomalies propagate to the eastern coast of Madagascar and feed into the Agulhas Current, eventually leaking into the Atlantic basin. Finally, the decadal signal is associated to the leading mode of decadal variability of the South Pacific Ocean. SSH propagating patterns derived from ORAP5.0 data are also obtained with satellite altimetry during the overlapping period (1993–2013), which strengthens confidence in our results. The association of the LSCB modulations to characteristic climate variability modes suggests that the position of the LSCB could be predicted. Plain Language Summary: The latitude of separation of the Brazil Current (LSBC) from the slope has profound implications on the exportation of shelf waters to the open ocean and potentially on the fertilization of the ocean. In this sense, understanding the mechanisms that drive its variability is relevant. The LSBC presents many different timescales of variability ranging from days and weeks to years. In this work we study the low‐frequency LSBC modulations, which are not yet completely understood. We found that three distinct periodicities characterize the LSBC temporal variability and that they are directly associated to the interaction of the Brazil Current with incoming ocean waves, known as Rossby waves, that traverse the Atlantic Basin. Waves are the fundamental mechanism through which the ocean can carry information from one region to another. In our article we aim to identify the regions that excite the waves. According to our results, the origin is associated to characteristic processes that occur in each ocean basin and that have been considerably discussed in the literature, such as the ENSO phenomenon, the Indian Ocean Dipole, among others. Remarkably, the waves take years to traverse and connect the different ocean basins, which suggests that the LSBC could be predicted. Key Points: The interannual variability of the latitude of separation of the Brazil Current is modulated at three distinctive periodicities: 2, 4 and 10 yearsInterannual modulations are associated to Rossby waves in the Atlantic basinRossby waves are excited by leading climate modes of variability characteristic of each ocean basin [ABSTRACT FROM AUTHOR]