Net community production in a productive coastal ocean from an autonomous buoyancy-driven glider

Net community production (NCP), an analog of carbon export out of the surface ocean, is often estimated using budgets of dissolved oxygen. Accurate estimates of oxygen-based NCP, especially in dynamic coastal regions, require constraints on vertical transport of water with O2 out of equilibrium with the atmosphere, non-steady state change in the oxygen inventory, heating/cooling-driven O2 disequilibrium, and the rate of bubble injection from wave activity. The latter two are typically evaluated by using discrete measurements of the O2/Ar ratio in lieu of O2 only. Because sophisticated sampling and measurement techniques are required to make these measurements, they are often limited in spatiotemporal resolution. However, high-resolution estimates of NCP may be useful in determining small-scale patchiness in export. In this study, we calculated high-resolution NCP in coastal Southern California using dissolved oxygen measurements made by an autonomous buoyancy-driven Slocum glider and an empirical relationship derived using discrete measurements of O2/Ar in the surface mixed layer to remove the influence of bubble injection, which accounted for ~1/4 of the O2 supersaturation observed. Using estimates of vertical transport from wind-speed based parameterizations, previously validated using a 7Be budget, we were able to correct for the physical biases to the signal, which are known to significantly influence dissolved oxygen budgets in this region. Our results agree well with previously published NCP estimates for the study area, but also reveal higher-frequency variability that discrete sampling was unable to resolve, suggesting that this approach may be useful in other regions with well-constrained vertical transport rates.