INTERANNUAL VARIABILITY OF THE LATITUDE OF SEPARATION OF THE BRAZIL CURRENT: TELECONNECTIONS AND OCEANIC ROSSBY WAVES PROPAGATION

BODNARIUK, NICOLÁS; SIMIONATO, CLAUDIA G.; SARACENO, MARTÍN; OSMAN, MARISOL; DIAZ, LEANDRO

JOURNAL OF GEOPHYSICAL RESEARCH

AMER GEOPHYSICAL UNION

Año: 2021 vol. 126 p. 1 - 24

0148-0227

The latitude of separation of the Brazil Current (LSBC) is analyzed with a view to unveiling the physical mechanisms that modulate its turning point at low frequencies. The global ocean reanalysis ORAP5.0 and the atmospheric reanalysis ERA-Interim spanning the period 1979-2013 are employed for this purpose. Three characteristic periodicities of the LSBC variability are found on the basis of a Singular Spectrum Analysis (SSA): 2, 4 and 10 years. Lagged Sea Surface Height (SSH) correlation maps relate these modulations to Rossby wave propagation in the Atlantic basin and the World Ocean. According to these maps, the biennial signal might be triggered by two different modes of variability: the Subtropical South Atlantic Dipole (SSAD) 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-years signal is triggered by both the SSAD 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 at 2, 4 and 10 years derived from ORAP5.0 data are also obtained with satellite altimetry absolute dynamic topography (ADT) during the overlapping period (1993-2013), which strengthens confidence in our results.