A novel estimate of ocean oxygen utilisation points to a reduced rate of respiration in the ocean interior

[摘要] The Apparent Oxygen Utilisation (AOU) is a classical measure of the amount ofoxygen respired in the ocean's interior. We show that AOU systematicallyoverestimates True Oxygen Utilisation (TOU) in 6 coupledcirculation-biogeochemical ocean models. This is due to atmosphere–oceanoxygen disequilibria in the subduction regions, consistent with previouswork. We develop a simple, new, observationally-based approach which we callEvaluated Oxygen Utilisation (EOU). In this approach, we take into accountthe impact of the upper ocean oxygen disequilibria into the interior,considering that transport takes place predominantly along isopycnalsurfaces. The EOU approximates the TOU with less than half of the bias of AOUin all 6 models despite large differences in the physical and biologicalcomponents of the models. Applying the EOU approach to a global observationaldataset yields an oxygen consumption rate 25% lower than that derivedfrom AOU-based estimates, for a given ventilation rate.

[学科分类] 地球化学与岩石