Convection in Thin Shells of Icy Satellites: Effects of Latitudinal Surface Temperature Variations

Abstract

AbstractWe use three‐dimensional numerical experiments of thin shell convection to explore what effects an expected latitudinal variation in solar insolation may have on a convection. We find that a global flow pattern of upwelling equatorial regions and downwelling polar regions, linked to higher and lower surface temperatures (Ts), respectively, is preferred. Due to the gradient in Ts, boundary layer thicknesses vary from equatorial lows to polar highs, and polar oriented flow fields are established. A Hadley cell‐type configuration with two hemispheric‐scale convective cells emerges with heat flow enhanced along the equator and suppressed poleward. The poleward transport pattern appears robust under a range of basal and mixed heating, isoviscous and temperature‐dependent viscosity, vigor of convection, and different degrees of Ts variations. Our findings suggest that a latitudinal variation in Ts is an important effect for convection within the thin ice shells of the outer satellites, becoming increasingly important as solar luminosity increases. Variable Ts models predict lower heat flow and a more compressional regime near downwellings at higher latitudes, and higher heat flow and a more extensional regime near the equator. Within the ice shell, Hadley style flow could lead to large‐scale anisotropic ice properties that might be detectable with future seismic or electro‐magnetic observations.