Excitable Dynamics of Neoproterozoic to Early Paleozoic Atmospheric and Ocean Oxygen

The geochemical carbon isotope and redox proxy record indicates that Earth’s surface oxygenation involved a prolonged period of extreme variability in atmospheric and oceanic oxygen, spanning from the early Neoproterozoic to the early Paleozoic. This variability has been linked to external tectonic and evolutionary forcings, as well as to internal nonlinear feedbacks related to the redox-sensitivity of marine phosphorus burial. Here we introduce a multitimescale dynamical systems framework to examine the stability of the coupled biogeochemical cycles of phosphorus, carbon, and oxygen. Our analysis reveals the criteria for system stability, and identifies an “excitable” regime where small forcings can trigger ocean oxygenation and anoxic events. We suggest that transitions through stable, excitable and oscillatory regimes can explain the Neoproterozoic to Paleozoic geochemical record, and that dynamical constraints at the Earth system level account for more of these patterns and trends than has been previously recognized.