Correcting oceanic O-2/Ar-net community production estimates for vertical mixing using N2O observations

摘要

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 N2O 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 N2O-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 N2O-O-2/Ar tracer significantly improves NCP estimates when/where vertical mixing is important.