Effect of Rϱ on double diffusive interleaving

Abstract

The role of the density ratio during double diffusive interleaving is investigated experimentally. A sharp vertical front is created by lifting a barrier separating two stratified compartments of different T- S composition but similar density. The environment is either stably stratified in both components or double diffusively stratified in the diffusive sense. Interleaving layers driven entirely by double diffusive processes start to form and to propagate horizontally. The observed thickness of the intrusions agrees well with the predicted vertical scale of Ruddick and Turner [ Deep-Sea Research, 26, 903–913 (1979)] when the stratification is doubly stable, and is found to be smaller in the diffusive case, as can be predicted from Linden's [ Deep-Sea Research, 23, 895–908 (1976)] formula. The cross-frontal flux is independent of the stability of the environment except when the environment is double diffusively stratified in the diffusive sense and the gradient of the unstable component is at least 66% that of the stable component. In this latter case the cross-frontal flux is larger than for a double stable environment, as an extra source of potential energy is already present in the unstably stratified component. A parametrization of the cross-frontal flux is given in terms of the vertical finger flux. These results are applied to oceanic Meddies and to the survival of the core region of a Meddy against lateral intrusions.