Physical mechanisms driving oxygen subduction in the global ocean

• Published in: Geophysical Research Letters
• Main Authors: Portela, Esther, Kolodziejczyk, Nicolas, Vic, Clement, Thierry, Virginie
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2020
• Subjects: oxygen subduction; ocean ventilation; mode waters; oxygen difussion; Southern Ocean; North Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00645/75670/76537.pdf; https://archimer.ifremer.fr/doc/00645/75670/76538.pdf; https://doi.org/10.1029/2020GL089040; https://archimer.ifremer.fr/doc/00645/75670/

Future changes in subduction are suspected to be critical for the ocean deoxygenation predicted by climate models over the 21st century. However, the drivers of global oxygen subduction have not been fully described or quantified. Here, we address the physical mechanisms responsible for the oxygen transport across the late winter mixed layer base and their relation with water‐mass formation. Up to 70% of the global oxygen uptake takes place during Mode Water subduction mostly in the Southern Ocean and the North Atlantic. Te driving mechanisms are (i) the combination of strong currents with large mixed‐layer‐depth gradients at localized hotspots and (ii) the wind‐driven vertical velocity within the Subtropical gyres. Oxygen diffusion, despite being underestimated in this study, is likely to play and important role in the global ocean oxygenation. The physical mass flux dominates the total oxygen subduction while the oxygen solubility plays a minor role in its modulation. Key points Up to 70% of the global oxygen uptake occurs during Mode Water subduction,driven by lateral induction and vertical velocity Oxygen diffusion, despite large uncertainties, is likely to play an important role in the global oxygen uptake Total oxygen subduction is driven by the mass flux, with little contribution of the meridional variability of oxygen concentration