Vertical mixing is often regarded as the Achilles' heel of ocean models. In particular, few models include a comprehensive and energy-constrained parameterization of mixing by internal ocean tides. Here, we present an energy-conserving mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static two-dimensional maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three-dimensional map of dissipation which compares well with available microstructure observations and with upper-ocean finestructure mixing estimates. This relative agreement, both in magnitude and spatial structure across ocean basins, suggests that internal tides underpin most of observed dissipation in the ocean interior at the global scale. The proposed parameterization is therefore expected to improve understanding, mapping and modelling of ocean mixing.

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.