A climate threshold for ocean deoxygenation during the Early Cretaceous.

Oceanic anoxic events (OAEs) are historical intervals of global-scale ocean deoxygenation associated with hyperthermal climate states and biological crises. Massive volcanic carbon dioxide (CO) emissions frequently associated with these events are thought to be a common driver of ocean deoxygenation through several climate-warming-related mechanisms. The Early Cretaceous OAE1a is one of the most intense ocean deoxygenation events, persisting for more than 1 Myr (refs.