Orbital-to-millennial-scale coupled evolution of dust input， productivity， and redox conditions in the Southern Ocean over the past 160 kyr

The Scotia Sea is a key region for atmosphere-ocean-ice interactions in the Southern Ocean. Its atmospheric and oceanic processes， together with the associated biogeochemical processes， closely link dust input， productivity， and redox conditions in the sedimentary record. Therefore， a key challenge lies in how to effectively decouple and identify the dominant environmental signals in this region. This study utilizes high-resolution elemental and physical property data from sediment cores collected at IODP Site U1537， applying principal component analysis （PCA） to systematically reconstruct the environmental evolution of the Scotia Sea over the past 160 kyr. The results indicate that terrigenous dust primarily dominates sediment composition， with its input regulated by Antarctic climate and sea-level changes. Siliceous productivity appears to be controlled primarily by changes in sea-ice extent and the intensity of wind-driven upwelling， rather than by iron fertilization， on both orbital and millennial scales. Deep-ocean redox conditions， inferred from Mn/Al， reveal a strong coupling between bottom water ventilation and productivity， factors that together modulate atmospheric CO₂. During MIS 5e and the Holocene Climatic Optimum， minimal dust input， rapid sea-ice retreat， and enhanced Antarctic Circumpolar Current （ACC） collectively promoted productivity and deep ventilation， coinciding with atmospheric CO₂ approaching 300 ppm. This study reveals the coupled evolution of dust， productivity， and redox conditions on orbital to millennial scales， offering new insights into Southern Ocean physical-chemical-biological interactions.