Equatorial Pacific dust fertilization and source weathering influences on Eocene to Miocene global CO2 decline

Abstract

Stimulation of the biological pump by iron-bearing dust in the eastern equatorial Pacific Ocean plays an important role in long-term carbon sequestration, yet past dust fertilization and its impact on CO2 perturbations over major climate transitions remain debated. Here, we integrate proxies of dust input, source-region weathering, and biological pump activity from late Eocene to early Miocene sediments of Integrated Ocean Discovery Program Hole U1333, which includes the Eocene-Oligocene Transition (~34 million years ago) when a major ice sheet was first established on Antarctica. We find that intensified chemical weathering in the large central Asian dust source region enhanced atmospheric CO2 removal at ~34 Ma. Superimposed dust fertilization and biological pump action amplified this CO2 removal before ~34 Ma, while weakening of this amplification process helped to moderate the CO2 decline after that time. The observed inter-linked, counteracting processes with different timescales illustrate the complexity of carbon cycle feedbacks associated with major climate changes.