The formation and mixing of a reverse density stratification.

Northern lakes are typically ice-covered during the winter months. Under the ice, these lakes can also become `reverse stratified' due to the temperature of maximum density of lake water being above its freezing point. Field studies of a brackish lake in Northern Alberta have recorded temperature profiles within the water column over several years and have demonstrated the formation of such a stratification. In addition, these measurements identify several interesting structural features to the density stratification for which we do not yet have an explanation. We have developed a theoretical framework to estimate the heat fluxes for in this regime.

This presentation will discuss an idealize fluid-mechanics problem for convection near the temperature of maximum density of lake water, using direct numerical simulations. We will demonstrate how a nonlinear equation of state modifies the transport and mixing of an unsteady density stratification. We then related these results back to laboratory and field measurements, with a particular focus on the distribution of the density field.