What the flux? Assessing the global ocean biological carbon pump

CO2 taken up from the atmosphere by biological processes in the ocean is transferred into the deep ocean's "twilight zone" mostly in the form of sinking particles. Without this "biological carbon pump", atmospheric CO2 would be 50% higher than it already is. Despite its importance, our understanding of this pump is currently limited due to the scarcity of ship-board observations, in particular of how particulate organic carbon (POC) fluxes vary both spatially and seasonally. However, now a growing network of underwater robots are opening the door for long-term, high resolution observations of these sinking particles. Biogeochemical-Argo floats (https://biogeochemical-argo.org/) are unmanned autonomous vehicles that make measurements over years, to depths of 1000 m, including optical backscatter data which can be used to estimate POC fluxes. The global scale of the float network will allow important, currently unresolved, questions to be addressed, such as: What is the global spatial pattern of fluxes? (Marsay et al., 2015); How do fluxes vary seasonally? (Briggs et al., 2020); How might these patterns change in the future? (Canadell et al., 2021 - Section 5.4.4.2). Filling this knowledge gap using these new data will allow better predictions of how this important planetary carbon flux is affected by both natural variability and climate change.