Open questions in turbulent stratified mixing: Do we even know what we do not know?

Abstract

Understanding how turbulence leads to the enhanced irreversible transport of heat and other scalars (such as salt and pollutants) in density-stratified fluids is a fundamental and central problem in geophysical and environmental fluid dynamics. There is a wide range of highly important applications, an important example being the description and parameterization of diapycnal transport in the world's oceans, a key area of uncertainty in climate modeling. Recently, possibly due to the proliferation of data obtained through direct observation, numerical simulation, and laboratory experimentation, there has been an explosion in research activity directed at improving community understanding, modeling, and parametrization of the subtle interplay among energy conversion pathways, turbulence, and irreversible mixing in density-stratified fluids. However, there are still leading-order open questions and areas of profound uncertainty concerning this interesting and important research challenge.