A new estimate of ocean oxygen utilization points to a reduced rate of respiration in the ocean interior.

The Apparent Oxygen Utilization (AOU) is a classical measure of the amount of oxygen respired by biological processes in the ocean interior. We show that the AOU systematically overestimates the True Oxygen Utilization (TOU) in 6 coupled circulation- biogeochemical ocean models, due to atmosphere--ocean oxygen disequilibrium in the subduction regions, consistent with prior work. We develop a new approach that we call Evaluated Oxygen Utilization (EOU), which approximates the TOU at least twice as well as AOU in all 6 models, despite large differences in the physical and biological components of the models. Applying the EOU approach to a global observational dataset leads to an estimated biological oxygen consumption rate that is by 25 percent lower than that derived from AOU-based estimates. [ABSTRACT FROM AUTHOR]