Tidal resonance in icy satellites with subsurface oceans

Tidal dissipation is a major heat source for the icy satellites of the giant planets. Several icy satellites likely possess a subsurface ocean underneath an ice shell. Previous studies of tidal dissipation on icy satellites, however, have either assumed a static ocean or ignored the effect of the ice lid on subsurface ocean dynamics. In this study, we examine inertial effects on tidal deformation of satellites with a dynamic ocean overlain by an ice lid based on viscoelasto-gravitational theory. Although ocean dynamics is treated in a simplified fashion, we find a resonant configuration when the phase velocity of ocean gravity waves is similar to that of the tidal bulge. This condition is achieved when a subsurface ocean is thin (<1 km). The enhanced deformation (increased h2 and k2 Love numbers) near the resonant configuration would lead to enhanced tidal heating in the solid lid. A static ocean formulation gives an accurate result only if the ocean thickness is much larger than the resonant thickness. The resonant configuration strongly depends on the properties of the shell, demonstrating the importance of the presence of a shell on tidal dissipation.