Global Eddy Subduction Carbon Pump From Argo Floats

The eddy subduction pump, part of the biological pump, transports carbon-rich surface filaments downward via kilometer-scale turbulence in frontal regions, over days to weeks. Because of its spatial and temporal scales, this pump has been challenging to observe and quantify. Prior studies assessed the eddy subduction pump but were geographically limited. We introduce a detection algorithm that identifies subduction events using colocated anomalies in apparent oxygen utilization, absolute salinity, and optical backscattering. We apply it to 126,591 biogeochemical Argo profiles collected by 941 floats. The algorithm identifies 1,333 carbon subduction events concentrated in springtime hotspots of high eddy kinetic energy in the Southern Ocean and the subpolar North Atlantic. We estimate a global particulate organic carbon export flux below 200 m of 0.05 [(Formula presented.) –0.28] Pg C (Formula presented.). About two-thirds of this export occurs in the Southern Ocean (40%) and the North Atlantic (25%). Less than 25% of this flux enters water masses that remain isolated from the atmosphere for at least 50 years. Including dissolved organic carbon yields a total organic carbon export of 0.09 [0.01–0.51] (Formula presented.), less than 5% of the total organic carbon exported by the biological pump and an order of magnitude smaller than previous estimates. Although difficult to resolve in Earth system models, the eddy subduction pump appears to be a secondary term in global carbon budgets.