Variability of the Deep Western and Eastern Boundary Currents and their relationship to the Meridional Overturning Circulation at 34.5°S

Variations in the Meridional Overturning Circulation (MOC) are known to have connections to a wide range of societally important quantities including coastal sea level, precipitation patterns, heat waves, and hurricane intensification. Significant efforts have been undertaken over the past few years to advance our knowledge of the MOC structure and variability, however there are many aspects of this complex system that are still poorly understood. One area where progress is being made in the study of the MOC structure and pathways is at 34.5°S in the South Atlantic. Using several years of daily observations from moored instruments, the relationship between the basin-wide MOC upper limb and the deep flows associated with the lower MOC limb are described. The Deep Western and Eastern Boundary Currents at 34.5°S share some similarities, however both the spatio-temporal structure and the water mass properties carried in the two flows are distinct. Variability in the Deep Western and Eastern Boundary Currents greatly exceeds that of the upper limb of the MOC, illustrating the strength of the deep recirculation cells in both the Argentine and Cape Basins. Both deep boundary currents exhibit significant baroclinic and barotropic variations, and there is no significant correlation between these two flow components in either deep boundary current. These and other characteristics of the variability of these flows will be discussed, along with the implications and recommendations for long-term observation of these key flows.