Double-Diffusive Interleaving. Part I: Linear Stability Analysis

Abstract Quasi-horizontal interleaving between water masses is frequently observed in the frontal regions between different water masses where there are significant compensating isopycnal gradients of temperature and salinity. It is believed that these intrusions are driven by double-diffusive convection which transports salt, heat and density across sharp, quasi-horizontal interfaces (i.e., across regions of large vertical property gradients). Stern and other investigators have parameterized the vertical flux of salt in these intrusions by an eddy diffusivity multiplied by the vertical gradient of salinity, whereas laboratory experiments show that sharp interfaces tend to occur by double-diffusive convection and that the vertical fluxes of properties depend on the property contrasts across the interfaces. In this paper it is assumed that the vertical fluxes of double-diffusive convection are proportional to the salinity contrast across the sharp interfaces that occur between the quasi-horizontal intrusio...