Frölicher, T. L., Aschwanden, M. T., Gruber, N., Jaccard, S. L., Dunne, J. P., & Paynter, D. (2020). Contrasting Upper and Deep Ocean Oxygen Response to Protracted Global Warming. Global Biogeochemical Cycles, 34 (8), e2020GB006601. https://doi.org/10.1029/2020GB006601
It is well established that the ocean is currently losing dissolved oxygen (O2) in response to ocean warming (the solubility of O2 decreases with increasing seawater temperature resulting in less O2 available to marine life). However, the long‐term equilibrium response of O2 to a warmer climate is neither well quantified nor understood. In this study, multimillennial global warming simulations with a comprehensive Earth system model was used to show that the equilibrium response in ocean O2 differs fundamentally from the ongoing transient response. The deep ocean is better ventilated and oxygenated compared to preindustrial conditions, even though the deep ocean is substantially warmer. In contrast, O2 in most of the upper tropical ocean is substantially depleted. This study emphasizes the millennial‐scale impact of global warming on marine life, with some impacts emerging many centuries or even millennia after atmospheric CO2 has stabilized.
Policy relevant message:
The impact of global climate change on marine life not only is already clearly visible and well recorded, but the millennial‐scale impact of global warming will also emerge many centuries or even millennia after atmospheric CO2 has stabilized.