Precessionally-driven Upwelling strength at Northern Benguela Upwelling System

The Benguela Upwelling System (BUS) is a highly productive upwelling region that plays a critical role in the global carbon cycle. The intensity of the BUS is influenced by changes in trade winds, which in turn control regional primary productivity and the sequestration of atmospheric CO₂. The dynamic of the BUS is then linked to the wind-driven circulation of the South Atlantic Subtropical Gyre (SASG), which is part of the upper branch of the Atlantic Meridional Overturning Circulation (AMOC) that transports heat from the subtropics towards the North Atlantic contributing to global energy distribution. The position of the Intertropical Convergence Zone (ITCZ) relative to the strength of the trade winds compensates for the asymmetrical inter-hemispheric energy balance, which is closely connected to BUS activity. However, understanding the long-term dynamics of the BUS connected to AMOC variability and its implications for the carbon budget on the orbital scale remains elusive due to a lack of high-resolution records spanning the Late Pleistocene. Here we present a 365 ka-long upper ocean stratification (∆δ¹⁸O) reconstruction from the northern BUS based on the δ¹⁸O gradient between planktic foraminifera G. bulloides and G. inflata. We examine the vertical carbon transfer (∆δ¹³C_Upper) based on the same species, as well as between G. inflata and C. wuellerstorfi (∆δ¹³C_Lower). Spectral analysis performed on the ∆δ¹⁸O record reveals precessionally-paced periods of stratification decrease related to the intensification and offshore expansion of the upwelling cell. Precessionally-paced ∆δ¹⁸O and both ∆δ¹³C records spike following the austral summer insolation maxima, revealing a robust link between the intensification of the BUS, wind strength, the AMOC, and the decrease of global atmospheric CO₂ during positive precession.