资源环境科技发展态势分析平台

At depth, O₂ depleted because of organic matter remineralization is generally estimated based on apparent oxygen utilization (AOU). However, AOU is an imperfect measure of oxygen utilization because of O₂ air-sea disequilibrium at the site of deep-water formation. Recent methodological and instrumental advances have paved the way to further deconvolve processes driving the O₂ signature. Using numerical model simulations of the global ocean, we show that measurements of the dissolved O₂/Ar ratio, which so far have been confined to the ocean surface, can provide improved estimates of oxygen utilization, especially in regions where the disequilibrium at the site of deep-water formation is associated with physical processes. We discuss applications of this new approach and implications for current tracers relying on O₂ such as remineralization ratios, respiratory quotients and preformed nutrients. Finally, we propose a new composite geochemical tracer, [O₂]^*_bio combining dissolved O₂/Ar and phosphate concentration. Being insensitive to photosynthesis and respiration, the change in this new tracer reflects gas exchange at the air-sea interface at the sites of deep-water formation.