Using Triple Isotopes of Dissolved Oxygen to Evaluate Global Marine Productivity

Since the triple isotopic composition of dissolved O2 (¹⁷Δ) was introduced as a natural tracer of photosynthetic gross O2 production (GOP) over 10 years ago, observations of ¹⁷Δ have been used to constrain marine productivity throughout the global ocean. This incubation-independent approach has several advantages: It allows the determination of production free from containment artifacts and reduces logistical hurdles that can make obtaining productivity with traditional incubation-dependent methods difficult. As such, GOP estimates derived from ¹⁷Δ have been used to give insight into potential biases in incubation-based approaches and to evaluate satellite-based estimates of production at the regional scale. With increased use, we have also learned more about the potential biases and uncertainties of this approach, some of which have been addressed by recent method improvements. We recap the major advances the ¹⁷Δ method has brought to improved understanding of biological carbon cycling, from incubation bottles to ocean basins.