Past to future South Atlantic meridional overturning circulation: pathways and low-frequency variability

Abstract

Considering the need to understand the role of the ocean in climate change projections and the need for diagnosis and evaluation of these projections to account for internal variability, we will investigate the pathways, which compose the upper limb of the Meridional Overturning Circulation in the South Atlantic sector. This region is the focus of the Brazilian contribution for the project PaCMEDy (Paleo- Constraints on Monsoon Evolution and Dynamics, FAPESP - No. 2015/50686-1). The upper limb of the South Atlantic Meridional Overturning Circulation (SAMOC) depicts northward advection of waters starting at the Southeastern corner of the basin which brings Pacific and Indian Ocean contributions through the 1) Benguela Current; 2) Southern branch of the South Equatorial Current; 3) North Brazil Undercurrent; 4) North Brazil Current system all the way into the Northern hemisphere and the polar region in order to compensate the deep-water formation. The spatio-temporal evolution of the flow is addressed, with focus on the lowfrequency variability and response to climate change, as well as possible modulating factors. Also to be explored is the connection of the SAMOC upper limb to the South Atlantic Subtropical Gyre, as its Northeastern boundary. Since these systems are closely coupled, our hypothesis is that the anticyclonic circulation of the subtropical gyre may reflect variations in the upper limb flow structure and vice versa. Given this circumstance, the interplay between these large-scale oceanic features is analyzed. (AU)