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

At the beginning of the Cenozoic, the atmospheric CO2 concentration increased rapidly from similar to 2000 ppmv at 60 Ma to similar to 4600 ppmv at 51 Ma, which is 5-10 times higher than the present value, and then continuous declined from similar to 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 CO2. The average annual west Pacific volvano eruption is 1.11 km(3), which is higher than previous estimations. The amount of annual CO2 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 CO2 concentration.

Automated summary

During the early Cenozoic, the atmospheric CO2 concentration experienced a rapid increase, reaching values 5-10 times higher than present levels, followed by a continuous decline. The cause of this phenomenon remains uncertain. This study suggests that the initiation of west Pacific plate subduction, triggered by collision in the Tibetan Plateau, coincided with this tipping point. The subduction zones in the Pacific had deeper water depths, resulting in less carbonate subduction, while the Neo-Tethys had shallower depths, leading to more carbonate subduction. Furthermore, the west Pacific subduction zones had higher volcanic ash emissions, which helped consume CO2.