Winter deep convection rapidly delivers organic carbon below 1,000 meters, study finds

A Science Advances study led by the Institute of Marine Sciences (ICM-CSIC) and the Barcelona Supercomputing Center finds that large-scale winter sinking of surface water can rapidly deliver nutrient-rich organic particles to depths of more than 1,000 meters, phys.org reported. In the subpolar North Atlantic, cold winter winds cool surface water until it densifies and sinks in deep convection, a process that helps drive long-lived ocean currents and carbon storage. The authors describe this underwater cascade as a mechanical shortcut that carries living microalgae and organic debris farther and faster than gravity-driven sedimentation, though the pathway is intermittent and regional. The team combined Biogeochemical-Argo float data near 1,000 meters with marine physics and biogeochemistry simulations on BSC supercomputers. Floats detected chlorophyll peaks in the Labrador and Irminger seas during intense surface-water sinking between 2014 and 2017. Lead author Martí Galí said finding surface-typical chlorophyll at that depth was a surprise because it would normally have broken down earlier, and that the data help quantify a little-known carbon source while expanding the use of robots as deep-ocean observers. The paper is listed as Convection injects labile particulate organic carbon to the deep ocean, DOI: 10.1126/sciadv.aee6883.