Here, "active" refers to carbon in the ocean, atmosphere, and terrestrial biosphere, including peatland and permafrost. Sea level variations on glacial–interglacial timescales distinguish two fundamentally different domains of seafloor on which carbon burial has occurred: surfaces fringing the continents that emerged as ice sheets grew, and the permanently submerged surfaces of continental slopes and the deep sea. The modern fluxes are highly uncertain. Ranges in parentheses show the values found in the literature, above which representative modal values are shown. The total carbon inventory in the pre-industrial ocean, atmosphere, and biosphere is estimated to have been ∼41 000 PgC, 93 % of which was located in the ocean (Hain et al., 2014). Red arrows highlight fluxes that remove or supply alkalinity to the ocean, in addition to carbon.

• Hain, M. P., Sigman, D. M., and Haug, G. H.: (2014). "The Biological Pump in the Past". In: Treatise on Geochemistry, Second Edition, Turekian, H. D. H. and Karl, K., Elsevier (Eds.), Oxford, 485–517.