Coupling ice-ocean interface models with global-scale ice shell evolution models applied to Jovian moon Europa

Abstract

The astrobiological potential of the Jovian moon Europa has long been acknowledged [1]. Europa’s surface, icy shell, likely salty ocean, and silicate mantle play a key role in determining Europa’s habitability. In particular, the icy shell may harbor cracks and pockets filled with brine that could be niches for sustaining life. One major question is how and to which degree brines are incorporated into the ice shell and how they evolve. Global models of the ice shell resolving spatial scales of several hundred meters to kilometers are able to constrain the long term evolution of solid salt intrusions [e.g. 2] and potentially brines. Two-phase extensions in global models, however, have so far only been applied to pure water ice shells [3]. Since global ice shell models cannot capture the intake of brine at the ice-ocean interface due to the large scales they act on, they rely on boundary conditions that incorporate the physics of the interface. Meso-scale models of the ice-ocean interface [4, 5] operate on length scales of centimeters to meters. The transition between ice and seawater is treated as a mush containing a mix of solid and high-salinity brine, typically assumed to be in thermodynamic equilibrium [6]. Modern mushy-layer models [7] provide insight into the distribution of salt impurities [8]. We review inter-solver coupling strategies and discuss applicability to the coupling of the meso-scale ice-ocean interface and the planetary-scale convection. We propose a spatial homogenization of meso-scale simulation outputs and a Gauss-Seidel subcycling approach [9] to embed the fast into long-term variations. This work will lay the foundation for physically consistent scale-coupled evolution models of the cryohydrosphere of icy moons.