Disparities in ocean carbon sink estimates derived from observations and models raise questions about our ability to accurately assess its magnitude and trend. Surface ocean pCO2-data based carbon uptake inferences are systematically higher than estimates based on global ocean biogeochemical models. River carbon inputs and carbon burial in sediments contribute largely to this difference. Hence, it is critical to accurately constrain riverine carbon inputs (in the form of inorganic and organic carbon) and burial of organic and inorganic carbon in oceanic sediments. These are non-trivial task because part, but not all, of the organic carbon delivered by rivers is degraded to inorganic carbon and because of carbonate-system re-equilibrations, including calcium carbonate precipitation and dissolution. The Planchat et al. paper presents a simple conceptual model and explores its value using full scale ocean biogeochemical models. The resulting framework is useful for future model intercomparisons and for revising pre-industrial air-sea carbon fluxes when new carbon and alkalinity budgets become available.