Reconstructing ocean oxygenation over the Phanerozoic is essential for understanding the evolution and extinction patterns of marine life. While previous studies have largely focused on long-term geological processes—including weathering and burial—that influence atmospheric and oceanic oxygen levels, the contributions of shorter-term biogeochemical and physical ocean processes have often been oversimplified or overlooked. These dynamic processes—including changes in ocean circulation, phosphorus inventory, and animal body size—can significantly modulate long-term trends in both ocean and atmospheric oxygen levels. In this study, we utilize the Community Earth System Model (CESM) coupled with an offline diagnostic biogeochemistry model to disentangle the relative contributions of these shorter-term ocean processes and long-term geological processes over the Phanerozoic. Our findings highlight the importance of integrating both short-term and long-term mechanisms to reconstruct historical ocean oxygen levels. The reconstructed oxygenation history aligns well with multiple proxy records, providing new insights into the complex interactions that have shaped the evolutionary history of marine ecosystems.

ocean oxygenation, ocean circulation, body size