Integral Effects of Deep Convection

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Abstract
The large-scale, integral effect of convective elements (plumes) constituting an open-ocean chimney is investigated both theoretically and with a plume-resolving numerical model. The authors consider an initially homogeneous “patch” of ocean of depth H, with Coriolis parameter f, in which buoyancy is lost from the surface at a rate B. Both vorticity constraints on the convection patch and model analyses imply that, irrespective of the details of the plumes themselves, the mean vertical transport resulting from their action must be vanishingly small. Plumes are best thought of as mixing agents, which efficiently homogenize properties of the chimney. Scaling laws are derived from dynamical arguments and tested against the model. Using an expression for the vertical mixing timescale, they relate the chimney properties, the strength of the geostrophic rim-current setup around it, and its breakup timescale by baroclinic instability to the external parameters B, f, and H. After breakup, the instability... Abstract The large-scale, integral effect of convective elements (plumes) constituting an open-ocean chimney is investigated both theoretically and with a plume-resolving numerical model. The authors consider an initially homogeneous “patch” of ocean of depth H, with Coriolis parameter f, in which buoyancy is lost from the surface at a rate B. Both vorticity constraints on the convection patch and model analyses imply that, irrespective of the details of the plumes themselves, the mean vertical transport resulting from their action must be vanishingly small. Plumes are best thought of as mixing agents, which efficiently homogenize properties of the chimney. Scaling laws are derived from dynamical arguments and tested against the model. Using an expression for the vertical mixing timescale, they relate the chimney properties, the strength of the geostrophic rim-current setup around it, and its breakup timescale by baroclinic instability to the external parameters B, f, and H. After breakup, the instability...

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