Turbulence in Strongly Stratified Flows

Laboratory experiments in the early 1970's ({\em e.g.}, Lin \& Pao, {\em Ann.\ Rev. Fluid Mech.}, {\bf 11}, 1979) revealed quasi-horizontal vortices in wakes of objects moving through stably-stratified fluids. These results suggested new flow dynamics, in addition to internal waves, in flows strongly affected by stable density stratification, conditions which often occur, {\em e.g.}, in the atmosphere and oceans. In the past ten years theoretical analyses, numerical simulations, laboratory experiments and some field studies have led to a much better understanding of these flows and, in particular, how they can provide pathways to three-dimensional turbulence. In this talk some of the results of this research will be discussed.