Abstract
Future changes in subduction are suspected to be critical for the ocean
deoxygenation pre- dicted by climate models over the 21 st century.
However, the drivers of global oxygen subduction have not been fully
described or quantified. Here, we address the physical mech- anisms
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 At- lantic. This oxygen subduction is
driven by the combination of strong currents with large
mixed-layer-depth gradients at localized hot-spots and by the
wind-driven vertical velocity within the Subtropical gyres. Although
oxygen diffusion, often neglected, is uncertain, it is likely to be
important for the global oxygenation. The physical mass flux dominates
the total oxygen subduction while the oxygen solubility plays a minor
role in its modulation.