On the Role of Southern Ocean Mesoscale Dynamics on the Circulation and Meridional Overturning in the South Atlantic

The currents in the Southern Ocean, connecting all major ocean basins, transport and substantially mix the imprints of regional water masses. Their strongly eddying nature and frontal dynamics thus not only determine processes in the Southern Ocean itself but also influence the circulation and dynamics in the adjacent basins. We here use coarse global ocean general circulation model configurations with high-resolution, mesoscale resolving 1/10° nests covering the South Atlantic and western Indian oceans to investigate the impact of the mesoscale in the Southern Ocean on the circulation and meridional overturning in the South Atlantic. Two configurations varying in the location of their southern nest boundary, allow to systematically isolate the impact of mesoscale processes in the Southern Ocean sector. Explicitly restricting the nested area to north of 50° S, thereby excluding the Southern Ocean, leads to a substantial weakening of the Malvinas Current in strength and variability compared to the second configuration which incorporates the Southern Ocean to 63° S. In contrast to considerable changes in the local circulation, the South Atlantic meridional overturning strength is not significantly altered. We will specifically focus on the role of the Agulhas Current system, as an important player in the connectivity between the Indian and Atlantic oceans, in transmitting Southern Ocean variability into the Atlantic basin.