The dynamics of intrusions into a thermohaline stratification

Abstract

Physical and numerical experiments were performed for a linearly stratified heat—salt system, uniformly heated at one endwall. The initial stratification was in the diffusive sense. Intrusions formed at the heated endwall and propagated out into the interior fluid. Three classes of flow were identified, based upon the gravitational stability ratio, Rp, and a lateral stability parameter, R1, For R1 > 1, a vertical lengthscale for the initial intrusion thickness was developed which agreed well with that observed in the physical experiments. In all cases, a region of salt fingering developed due to gradient reversal at the heated endwall. Two very distinct merging processes were observed depending on the specific flow class. The first process occurred under conditions of high gravitational and lateral stability, and appeared to be controlled by horizontal motions induced by the intrusions. The second process was observed under less stable conditions and was a result of vertical motions at the heated endwall within the intrusions themselves. In the least stable class of flow (low gravitational and lateral stability), the intrusions were found to be self-perpetuating in the sense that they continued to propagate following removal of the endwall heat flux.