Overturning Ocean Circulations in Ocean Worlds
Abstract
Liquid water oceans within our solar system provide intriguing laboratories for the coupled interaction between physical, chemical and biological processes needed to support life. Both the ocean's stratification and its ability to distribute heat and tracers along and across density surfaces is critical for understanding the relationship between a global ocean and the planetary energy budget, including the dissipation of tidal heating and the transport of geothermal heat from the interior to the ice surface. Similar to Earth's ocean, the circulation dynamics of oceans such as those on Enceladus, Europa, and Titan and the subsequent heat and salt distributions are likely to be controlled by processes occurring at the ocean boundaries. Variations in the ice shell thicknesses of these bodies, which were recently inferred from Cassini observations for Enceladus and Titan, are valuable diagnostics for distinguishing circulation properties of various ocean worlds. Here, we focus on horizontal convection driven by equator-to-pole buoyancy differences that could be caused by latitudinal ice transport at the ocean surface, as well as the impact of a freshwater layer formed by ice melting, and the consequences of an imposed surface slope due to varying ice thickness.
We expand on work by Zhu et al. (2017), which found that freshwater fluxes associated with meridional ice transport on Europa could, depending on the circulation regime, result in a stratified ocean. Now, with an idealized residual circulation model, based on the water mass transformation approach, we can conduct a broader exploration of vertically stratified ocean configurations. We consider the impact of varying freshwater fluxes, changing both the region where melt occurs and the intensity of the buoyancy forcing. We find that even without geothermal heating in the deeper ocean it is possible to trigger a large-scale overturning circulation. We hope to utilize this model to advance our understanding of coupled ice-ocean interactions on ocean worlds, in order to help constrain the thermal and compositional evolution of these worlds.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P52B..07L
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHERE;
- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6221 Europa;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6282 Enceladus;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS