Convective elements that carry fluid particles vertically over distances comparable to the depth of the ocean The horizontal scale is about 1 km, and they are driven by intense cooling at the sea surface that reaches ~1000 W m-2 They are ascending and descending currents that can reach speeds in excess of ~10 cm s-1 Plumes penetrate most of the water column and efficiently homogenize its properties, forming deep, cold mixed layers called chimneys The chimneys are maintained close to neutrality, geostrophically adjust, and break up into fragments called cones on a time scale of a few days The cones have a spatial scale of several kilometers See Jones and Marshall (1993)