Iron fertilization of the North Pacific did not drive long-term Pliocene to Quaternary cooling

While several hypotheses exist to explain the development of large-scale perennial Northern Hemisphere ice sheets in the late Pliocene and early Pleistocene, the prevailing view is that a decline in atmospheric carbon dioxide (CO2) drove this substantial change in late Neogene climate. However, the primary mechanism responsible for this reduction in CO2 has yet to be fully explored. Mineral dust-derived iron enhancement of ocean organic carbon production and export to the deep ocean and marine sediments has previously been invoked to explain reductions in atmospheric CO2 on multiple timescales. Here we test the hypothesis that iron fertilization of the Pliocene subarctic North Pacific affected atmospheric CO2, and in turn drove the formation of Northern Hemisphere ice sheets. By compiling Pliocene dust and export productivity proxy datasets from across the North Pacific and then progressively filtering for the most reliable records, we find that there is no relationship between North Pacific dust flux and export production in the Pliocene. Finally, we apply these new composites to assess previously proposed drivers of Pliocene Asian dust dynamics as well as North Pacific Ocean circulation and biogeochemistry.