Mechanisms of low-frequency oxygen variability in the North Pacific

These hypotheses are tested by contrasting O-2 anomalies with the heave-induced component of variability calculated from potential density anomalies. Isopycnal heave is the leading control on O-2 variability in the tropics, but heave alone cannot fully explain the amplitude of tropical O-2 variability, likely indicating reinforcing changes from the biological O-2 consumption. Midlatitude O-2 variability indeed reflects ocean ventilation downstream of the subduction region where O-2 anomalies are correlated with the depth of winter mixed layer.

These mechanisms, synchronized with the PDO, yield a basin-scale pattern of O-2 variability that are comparable in magnitude to the projected rates of ocean deoxygenation in this century under "unchecked" emission scenario.