Tidally heated convection: Constraints on Europa's ice shell thickness

Abstract

The thickness of Europa's ice shell is constrained with numerical experiments of thermal convection, including heterogeneous tidal heating. Thermal convection occurs in the stagnant lid regime with most of the tidal heating located in the bottom half of the layer. The addition of tidal heating mainly results in the increase of the temperature of the well-mixed interior and in the decrease of the heat flux at the base of the ice layer. In many simulations, the ice in hot plumes is heated up to its melting point. This induces episodic upwellings (0.5 Ma) of partially molten ice up to the base of the conductive lid, with possible implications for the formation of lenticulae and chaos regions. The thickness of the convective ice shell in equilibrium with the heat flow from the silicate core is estimated to be about 20-25 km. Tidal dissipation and surface temperature variations create lateral variations of the ice shell thickness of about 5 km, with maxima near the equator at the Jovian and anti-Jovian points and minima at midlatitudes. Surface heat flux is about 35-40 mW.m-2 ; it is almost constant all over Europa's surface, even though the tidal dissipation rate is four times larger at the poles than at the equator. Copyright 2003 by the American Geophysical Union.