A shift in ocean circulation drives variations in paleoproductivity in the North Pacific Ocean

The reconstruction of past marine biological productivity and its relationship with ocean circulation and climate change is crucial for understanding Earth's climate system. Episodes of high productivity induce chemical and mineralogical changes in Fe-Mn crusts, which are used to reconstruct past marine carbon cycling. Nevertheless, our knowledge of past changes in export production in the North Pacific and its relationship with phosphorus (P) cycling and ocean circulation remains limited. We present time-series bioactive element compositions and Ba/Mn ratios from a Fe-Mn crust sample (CXD31) recovered from the North Pacific. The crust age model is established via integration of magnetic scanning, analyses of beryllium isotopes and cobalt flux, showing a growth rate of 3.3 ± 1.8 mm/Myr. Concentrations of Ba, Cu, Ni, and Zn covary with benthic foraminiferal δ13C through time. A long-term trend in Ba/Mn ratios shows a decrease from 23 Myr to present, consistent with an overall decline in paleoproductivity as the CXD31 moved northwestward with the Pacific plate during this period. Ba/Mn ratios and P concentrations peak during high-productivity intervals, which we attribute to changes in ocean circulation (∼22.5, ∼16–12, and ∼2.7 Myr). Specifically, we propose that enhanced productivity and P accumulation were partly driven by the cessation of North Pacific Deep Water (NPDW) formation, followed by intensification of oxygen-rich Antarctic Bottom Water (AABW). Additionally, strengthened Antarctic Intermediate Water (AAIW) and increased aeolian dust input further enhanced productivity during high-productivity periods, suggesting a strong relationship among marine paleoproductivity, the biogeochemistry cycle of P and Ba, and ocean circulation.