Southern Ocean Origin of Multidecadal Variability in the North Brazil Current

Abstract

A new mode of multidecadal variability in the Southern Ocean, the so-called Southern Ocean Mode (SOM), has recently been discovered by Le Bars et al. (2016) in the strongly eddying version of the Parallel Ocean Program (POP). This mode has a corresponding period of 40 - 50 years and affects the variability in the Atlantic Meridional Overturning Circulation (AMOC) and the North Brazil Current (NBC). Using multi-channel singular spectral analysis on the POP output, also multidecadal variability was found in the NBC. This result suggests a teleconnection between the Southern Ocean and the NBC. The northward propagating multidecadal signal is clearly visible in SSH in the Southern Ocean, but submerges at 40°S. Anomalies in ocean heat content and temperature are observed between 40° - 5°S, at depths up to 1 km, and re-emerge near the equator where the anomalies propagate towards the NBC. This provides the evidence that the multidecadal signal found in the NBC has a Southern Ocean origin, and hence connected to the SOM.