1238 / 2024-09-20 18:29:34

Cold subduction shaped permanent oxygenation of the Earth’s atmosphere

Oxygenation Event, Cold subduction, COPSE geochemical model, Carbon-sulfur cycles

Session 42 - Deep-time ocean and climate changes: insights from models and proxies

The Earth own its oxygenated atmosphere via two macro steps in the Paleoproterozoic and Neoproterozoic-to-Paleozoic eras, yet a key trigger and feedback that the Earth-surface system keeping permanent oxygenation remains speculative. Here we ascribe the rise and permanent maintenance of atmospheric oxygen to long-term development of cold deep subduction zones, which facilitated mantle sequestration of the main reduced sinks of molecular oxygen, i.e., sedimentary organic carbon and pyrite. We quantitatively constrain the effects of cold deep subduction on pO₂ utilizing a modified COPSE biogeochemical model that incorporates secular variation of the thermobaric ratios of global metamorphic rocks. We find that our model can adequately reproduce the atmospheric oxygenation trajectory when driven solely by normalized efficiency of cold deep subduction spanning Earth’s history, alongside reasonable reconstructions of atmospheric carbon dioxide level, seawater sulfate concentration, sedimentary phosphorus abundance and marine redox. Our finding highlights the dominant control of net carbon flux between Earth’s interior and exterior on permanent atmospheric oxygenation despite short-term influences from other factors in play.