Icy moon oceans

Europa and Enceladus, icy moons of Jupiter and Saturn, host deep oceans beneath thick ice shells and essentially no atmosphere. These hidden oceans are among the most promising places to search for extraterrestrial life within our solar system, potentially sustained by hydrothermal activity at the seafloor. From a physical standpoint, they are also striking ocean systems: geothermally heated, strongly influenced by rotation, and completely insulated from the surface by ice.

I explore how ocean circulation operates under these extreme boundary conditions using a range of numerical models, including NASA’s ROCKE-3D model and Oceananigans. Across these simulations, the oceans exhibit vigorous overturning and energetic eddies that transport heat from the seafloor to the ice shell and from equator to poles. Unlike Earth’s oceans, circulation on icy moons is strongly shaped by rotation-axis-aligned convection, giving rise to large-scale states with warm poles and a colder equator.

A key theme of this work is the role of boundary layers at the ocean–seafloor and ice–ocean interfaces. While much previous research has focused on interior convection, high-resolution simulations show that boundary layers can fundamentally reorganize the large-scale flow. As boundary-layer effects strengthen, high-latitude zonal jets weaken, the equatorial region becomes dynamically active, and the circulation shifts from plume-dominated regimes to roll-like convective structures. These transitions are accompanied by systematic changes in meridional heat transport and overturning that depend on rotation rate and ocean geometry.

Beyond their astrobiological importance, ice-covered oceans provide a natural laboratory for testing general circulation models under conditions far removed from Earth’s climate. They follow the same basic physical principles of stratification, mixing, and overturning, but are forced primarily by tidal heating and constrained by thick ice shells. Modeling such systems pushes existing parameterizations to their limits and motivates new approaches. For example, tensor-based frameworks developed to represent convection aligned with the rotation axis on icy moons closely parallel challenges in representing slope-aligned descent of Antarctic Bottom Water in Earth system models.