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The effect of ocean heat transport on Enceladus’s ice geometry under different salinities

Presentation #509.07 in the session Icy Moons Interior and Ice Shell (Oral Presentation)

Published onOct 23, 2023
The effect of ocean heat transport on Enceladus’s ice geometry under different salinities

Observational data suggest that the ice shell on Enceladus is thicker at the equator than at the pole, indicating an equator-to-pole ice flow. In addition, the ice shell shows a hemispheric asymmetry with thinner ice at the south pole than the north pole. The ice geometry on Enceladus is controlled by the ice flow and the freezing and melting of the ice shell, the latter of which is modulated by the ocean heat transport. Here we use a numerical ocean model to study the ice-ocean interaction and ocean circulation on Enceladus with different salinities. We find that salinity fundamentally determines the ocean stratification. A stratified layer forms in the low salinity ocean, blocking vertical convection and enhancing the meridional ocean heat transport. However, in the absence of tidal heating in the ice shell, the ocean heat transport is found to always be equatorward, resulting in freezing at the pole and melting at lower latitudes, which cannot maintain the ice shell geometry against the equator-to-pole ice flow. Consistent with previous work, the simulation results therefore suggest that either the ice shell on Enceladus is not in an equilibrium state, or tidal dissipation in the ice shell is important in maintaining the observed equator-to-pole ice thickness gradient. The simulations also reveal a positive feedback loop between cross-equatorial ocean heat transport and ice melting, which can result in spontaneous symmetry breaking between the two hemispheres. This feedback may play a role in the observed interhemispheric asymmetry in the ice shell.

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