Warming-Induced Intensification of the Angolan Oxygen Minimum Zone Over the Past 43,000 Years

Deoxygenation and expansion of the Oxygen Minimum Zones (OMZs) are among the most significant threats for the oceans posed by ongoing global warming. However, current knowledge of the underlying drivers is limited by short and sparse instrumental records, constraining the ability of models to project the future behavior of OMZs under global change. In this study, we used a multi-proxy approach to reconstruct the dynamics of the shallow OMZ in the eastern subtropical South Atlantic, aiming to identify the main drivers of its variability through time. Our results reveal a gradual intensification of the shallow OMZ off Angola from ∼43 to ∼25 kyr BP, followed by persistently low oxygen conditions thereafter, primarily driven by progressive warming of the subtropical South Atlantic. The warming-induced reduction in oxygen solubility and decreased ventilation due to enhanced upper ocean stratification dominated over the influence of regional upwelling and remote physical–biogeochemical processes in the Southern Ocean. Our findings support model projections and observational data that highlight the dominance of warming-related processes as key drivers of tropical OMZ expansion. These mechanisms are likely to play a central role in the future intensification of OMZs as ocean temperatures continue to rise under ongoing global climate change.