| The role of eddies in the cancellation of the Deacon Cellis studied using the results of the ″OCCAM″ global, eddy-permitting ocean general circulation model.When integrated on density surfaces,in the Eulerian mean velocity field a wind driven overturning recirculation remains that crosses density surfaces.Including eddy transports this recirculation is not completely canceled, but strongly reduced and moved to shallower levels.When annual mean velocities are used,North Atlantic Deep Water is subject to recurrent upwelling anddownwelling through the density surface that divides the upper and lower branch of the thermohaline circulation.There is a strong latitudinal shift between the first and last upwelling. The latitudinal extent of this shiftis equal to the latitudinal extent of the Deacon cell.When eddy contributions are included, recurrent upwelling and downwelling through the critical density surface has not disappeared,due to drift and the Veronis effect, but the latitudinal shift between first and last upwelling is absent.We discuss the role of eddies in supplying the Ekman flow. It is shown that eddy-transports in the surface layerreduce the Ekman flow by more than 50%. This compensation is found to hold locally and nearly everywherein the Southern Ocean. Nevertheless, with or without eddy transports included,in both cases 10 Sv of NADW upwells in the Southern Ocean where it becomes lighter through surfacebuoyancy loss. The insensitivity to the inclusion of eddy transports of the amount of NADW that upwells in the Southern Oceanis discussed in the light of previous theories. |
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