Wind and buoyancy controls on surface productivity and bottom current strength in the Pacific Antarctic seasonal sea-ice zone since 300 ka

Whether upwelling-driven surface productivity and bottom current strength respond coherently to climatic forcing remains unclear, limiting geological constraints on Southern Ocean surface–deep linkage across glacial-interglacial cycles. Here, we reconstructed ~300 kyr of productivity and bottom current strength in the Pacific Antarctic seasonal sea-ice zone (SIZ), based on multi-proxy data from core ANT36/A3–08, using a chronology constrained by core-top radiocarbon, tephrostratigraphy, and orbital-scale geochemical correlation. Through glacial-interglacial cycles, productivity and bottom current strength covary, with higher values during interglacials and lower during glacials. This pattern is consistent with large-scale vertically coupled responses to meridional shifts of Southern Hemisphere Westerly Winds (SWW), which modulate surface upwelling and bottom currents along the Pacific Antarctic margin. Superimposed on this orbital-scale pattern are transient anomalies driven by buoyancy and atmospheric forcing. At the MIS 6/5 transition, meltwater-induced stratification counteracted the expected SWW-driven intensification, producing muted increases in productivity and bottom current strength, despite a pronounced poleward shift of SWW. During MIS 2, both records intensified briefly, coinciding with heightened variability in the Amundsen Sea Low (ASL). Stronger ASL variability likely enhanced sea-ice divergence and intermittent polynya formation, thereby strengthening brine rejection. Together, these paired productivity and bottom current signals are interpreted to reflect changes in upper-limb upwelling and lower-limb deep renewal at the Pacific Antarctic margin, providing a site-scale imprint of broader Southern Ocean overturning adjustments and highlighting sensitivity to future SWW shifts and increasing Antarctic meltwater input.