Global upper ocean oxygen budget and an observational constraint on the biological pump

Abstract

Abstract One mechanism by which the ocean absorbs and sequesters CO2 is through the fixation of inorganic carbon by biological production and its subsequent transport to the deep ocean, a process known as the biological carbon pump. Although the importance of the biological carbon pump in the global carbon cycle has long been recognized, estimation of its actual contribution to global ocean carbon uptake remains highly uncertain, challenging the observational constraints of current Earth system model simulations. Here we quantify global annual ocean carbon sequestration via the biological carbon pump by using dissolved oxygen data to estimate net biological oxygen production from an upper ocean oxygen budget calculation, leveraging the substantial increase in observational data provided by the recent expansion of Biogeochemical-Argo. The upper ocean oxygen budget, based on observational data, reveals a global balance between net oxygen removal due to physical processes (air–sea exchange, advection, and diffusion) and net oxygen production driven by biological activities. We converted the derived annual net biological oxygen production into annual net community production using the photosynthetic oxygen:carbon ratio, and inferred an estimated global oceanic carbon uptake by the biological pump of 6.15 ± 0.75 Pg C y− 1.