Geoengineered Ocean Vertical Water Exchange Can Accelerate Global Deoxygenation

Ocean deoxygenation is a threat to marine ecosystems. We evaluated the potential of two ocean intervention technologies, that is, “artificial downwelling (AD)” and “artificial upwelling (AU),” for remedying the expansion of Oxygen Deficient Zones (ODZs). The model‐based assessment simulated AD and AU implementations for 80 years along the eastern Pacific ODZ. When AD was simulated by pumping surface seawater to the 178–457 m‐depth range of the ODZ, vertically integrated oxygen increased by up to 4.5% in the deployment region. Pumping water from 457 m depth to the surface (i.e., AU), where it can equilibrate with the atmosphere, increased the vertically integrated oxygen by 1.03%. However, both simulated AD and AU increased biological production via enhanced nutrient supply to the sea surface, resulting in enhanced export production and subsequent aerobic remineralization also outside of the actual implementation region, and an ultimate net decline of global oceanic oxygen. Key Points Artificial downwelling (AD) and upwelling (AU) in the eastern Pacific oxygen deficient region are simulated in a global model Both technologies can effectively mitigate local expansion of intermediate‐depth oceanic oxygen deficient zones under climate change Global deoxygenation is however enhanced due to increased export production and aerobic respiration resulting from AD and AU