Layering and double-diffusion style convection in Europa's ocean

We assess the effects of fluid composition and depth-dependent hydrostatic pressure on dynamics in a europan ocean primarily composed of aqueous Na2SO4 and MgSO4, for both a saturated and a dilute ocean. We observe a salinity- and pressure-dependent check on buoyancy in putative upwellings, which could act as a mechanism for storing heat in the ocean's base. Uptake of salt to a warmed parcel of water from the seafloor environment causes upwellings to lose buoyancy before reaching the base of the overlying ice, implying a tendency toward ocean stratification. We make an analogy to double-diffusive convecting systems observed in the Red Sea and elsewhere in Earth's waters. Using currently understood parameterizations for onset and stability, we estimate a range of temperatures and salinities for which double-diffusive convection may occur in Europa's ocean. In the Red Sea, boundary layers separating convecting zones have been observed to move upward as the lower layer acquires heat and salt. We examine the possibility of stratification and double-diffusive convection as mechanisms for heat storage in Europa's ocean, and possible correlation with recently inferred changes in ice surface alteration style over the last 30-80 Myr.