Insights from a dynamical system approach into the history of atmospheric oxygenation.

Atmospheric oxygen levels are traditionally viewed to have been relatively stable throughout Earth's history with several-step increases. Emerging evidence, however, suggests extremely dynamic atmospheric oxygen levels through large swaths of Earth's history. Here, we provide a new perspective on atmospheric oxygen evolution using a dynamical analysis to explore the relative importance of previously proposed feedbacks on the global oxygen and carbon cycles. Our results from a stochastic analysis of oxygen mass balance in this framework suggest there are multiple steady states for atmospheric oxygen, but only three stable states. One stable state under anoxic conditions (<10 -5 present atmospheric level (PAL)), one at low (~10 -3 to 10 -2 PAL), and one near modern value atmospheric oxygen levels. Our findings also suggest two unstable states (tipping points) for atmospheric oxygen: one around 10 -5 and another one around 10 -1 PAL.