The California Current System (CCS) supports a wide array of ecosystem services with hypoxia historically occurring in near-bottom waters. Limited open ocean data coverage hinders the mechanistic understanding of CCS oxygen variability. We compared three models with different horizontal resolutions and complexities and found that regions of high dissolved oxygen (DO) variability deepened with distance to the coast, mainly driven by water mass variation in the surface 100 meters with remineralization important below 200 meters. We illustrate how oxygen anomalies are transported from the coastal areas into the open ocean where they are downwelled to 200-400 m and propagated Southwest on decadal timescales as part of the large-scale circulation. Pacific Decadal Oscillation was the climate variability mode most closely linked to DO anomalies. We suggest that increased sampling at subsurface near the shelf break and within the regions of water mass formation would help further elucidate mechanisms driving DO anomalies.