Coupling between the Cenozoic west Pacific subduction initiation and decreases of atmospheric carbon dioxides

At the beginning of the Cenozoic, the atmospheric CO 2 concentration increased rapidly from ~2000 ppmv at 60 Ma to ~4600 ppmv at 51 Ma, which is 5–10 times higher than the present value, and then continuous declined from ~51 to 34 Ma. The cause of this phenomenon is still not well understood. In this study, we demonstrate that the initiation of Cenozoic west Pacific plate subduction, triggered by the hard collision in the Tibetan Plateau, occurred at approximately 51 Ma, coinciding with the tipping point. The water depths of the Pacific subduction zones are mostly below the carbonate compensation depths, while those of the Neo-Tethys were much shallower before the collision and caused far more carbonate subducting. Additionally, more volcanic ashes erupted from the west Pacific subduction zones, which consume CO 2 . The average annual west Pacific volvano eruption is 1.11 km 3 , which is higher than previous estimations. The amount of annual CO 2 absorbed by chemical weathering of additional west Pacific volcanic ashes could be comparable to the silicate weathering by the global river. We propose that the initiation of the western Pacific subduction controlled the long-term reduction of atmospheric CO 2 concentration.