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Eddy-driven subduction exports particulate organic carbon from the spring bloom

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Science  10 Apr 2015:
Vol. 348, Issue 6231, pp. 222-225
DOI: 10.1126/science.1260062

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Down with atmospheric carbon dioxide

How does the ocean move carbon from surface waters to its deep interior? Current understanding is that carbon dioxide is removed from the atmosphere by phytoplankton that are eaten, and in turn their predators die and sink into deep water and seafloor sediments. In addition to this route, Omand et al. show that downwelling caused by ocean eddies 1 to 10 km across can deliver much of the carbon produced in spring to the deep sea. The eddies entrain small particles and dissolved organic carbon to augment the flux of large sinking particles.

Science, this issue p. 222

Abstract

The export of particulate organic carbon (POC) from the surface ocean to depth is traditionally ascribed to sinking. Here, we show that a dynamic eddying flow field subducts surface water with high concentrations of nonsinking POC. Autonomous observations made by gliders during the North Atlantic spring bloom reveal anomalous features at depths of 100 to 350 meters with elevated POC, chlorophyll, oxygen, and temperature-salinity characteristics of surface water. High-resolution modeling reveals that during the spring transition, intrusions of POC-rich surface water descend as coherent, 1- to 10-kilometer–scale filamentous features, often along the perimeter of eddies. Such a submesoscale eddy-driven flux of POC is unresolved in global carbon cycle models but can contribute as much as half of the total springtime export of POC from the highly productive subpolar oceans.

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