Internal Tides on Europa and Implications for Surface Deformation

Ocean worlds possess fascinating and mysterious subsurface environments shaped by a variety of processes, including tides. Most models of the tidal response of Europa, a key measurement of the Europa Clipper mission, assume an ocean of constant density. Yet, the density structure of Europa's ocean is unknown. We simulate how density stratification alters Europa's tidal response to eccentricity-forcing using a three-dimensional general circulation model. In particular, we determine how different oceanic density gradients permit and affect the generation of internal tides, and the corresponding displacement of the ocean surface. We find that, in general, a more steeply stratified ocean supports larger internal tides, with particular density gradients producing a resonant internal tide response. If the internal tide response is resonant, Europa's tidal deformation magnitude can be altered by a few meters. The tidal phase lag also increases, causing the ocean's effective tidal quality factor, $Q$, to vary by several orders of magnitude.