Transport of heat, CO2 and O2 by the Atlantic’s thermohaline circulation

We estimate transport of heat, CO2 and O2 by the Atlantic’s thermohaline circulation using an approach based on differences in the chemical and physical characteristics of North Atlantic Deep Water (NADW), Antarctic Intermediate Water (AAIW), and the northward return flow across the equator. The characteristics of the return-flow waters are constrained by imposing conservation of phosphate in the North Atlantic as a whole. Based on a total equatorial return flow of 13 x 106 m3 s-1, we find that the Atlantic north of the equator is a source of 7.7 ± 1.4 x 1014 W to the atmosphere, a sink of 0.51 ± 0.21 x 1014 mol of O2, and preindustrially was a sink of 0.33 ± 0.15 x 1014 mol of CO2. Uptake of O2 and CO2 by the North Atlantic is driven mainly by thermal, as opposed to biological processes.