Slantwise convection: A candidate for homogenization of deep newly formed dense waters

Abstract

Observations between 1000 and 2750 m, from a site in the 2800‐m deep part of the western basin of the Mediterranean Sea located in between the Provençal and Algerian subbasins, indicate large variations in water mass properties and stability that are associated with, but not directly caused by, dense‐water formation to the north of the site. These variations are apparently dominated by local convection induced by small‐scale eddies and propagation of inertial waves in stratified and homogeneous layers. Hereby is the horizontal component of Coriolis parameter important, governing slantwise, tilted convective mixing. This mixing creates marginally stable deep waters that are as spicy as near‐surface waters. It is found across some 200–400 m thick layers, which thickness is beyond the typical vertical buoyancy scale relevant for double diffusion. The observed convection is hypothesized to be important for dense‐water formation away from near‐surface sources, modifying the ocean's lower half.