Simulated Changes in the Particulate Carbon Export Efficiency due to Diel Vertical Migration of Zooplankton in the North Atlantic

Diel vertical migration (DVM) of zooplankton has been recognized to influence the biological pump by releasing carbon and nutrients at depth. However, uncertainties regarding the magnitude, spatial occurrence, and variability of this "active transport," as well as its impact on the carbon export, remain. To tackle these questions, a cost-effective parameterization of the DVM is included into a regional biogeochemical model simulating the North Atlantic. In addition to a reference simulation in which no DVM is simulated, two relative biomasses of migrating zooplankton (30% and 60%) have been tested. It leads to an active to passive export ratio in agreement with published estimations and to an increase in the carbon export efficiency at 1,000 m between 20% and 40%. However, this effect is partially canceled out by a simulated primary production decrease. DVM differently impacts contrasted North Atlantic regions with the largest effect on export efficiency found in the subtropical area