Increasing number of evidences suggest that the tropical Pacific Oxygen Minimum Zone (OMZ) has expanded in the last several decades. This has attracted lots of attention because global warming is hypothesized to cause ocean deoxygenation. Our calculation attribute this to the reddening of dominant climate mode, ENSO cycle. An interesting aspect of this problem is the compensation between solubulity and respiration effects, both of which correlate well with ENSO (red=ElNino, blue=La Nina) as shown below. As such the net oxygen change depends on subtle balance between the two components.
Ito T. and C. Deutsch, (2013), “Variability of the Oxygen Minimum Zone in the tropical North Pacific during the late 20th century”, submitted to Global Biogeochemical Cycles. (Manuscript)