Correcting oceanic O 2 /Ar‐net community production estimates for vertical mixing using N 2 O observations

The O 2 /Ar approach has become a key method to estimate oceanic net community production (NCP). However, in some seasons and regions of the ocean, strong vertical mixing of O 2 ‐depleted deepwater introduces a large error into O 2 /Ar‐derived NCP estimates. In these cases, undersaturated‐O 2 /Ar observations have for all intents and purposes been ignored. We propose to combine underway O 2 /Ar and N 2 O observations into a composite tracer that is conservative with respect to the influence of vertical mixing on the surface biological O 2 inventory. We test the proposed method with an ocean observing system simulation experiment (OSSE) in which we compare N 2 O‐O 2 /Ar and O 2 /Ar‐only gas flux estimates of NCP to the model‐simulated true NCP in the Southern Ocean. Our proof‐of‐concept simulations show that the N 2 O‐O 2 /Ar tracer significantly improves NCP estimates when/where vertical mixing is important.