Ancient Mars Climate With a Polar Ocean and Ice Sheet Dynamics

Abstract In this article, we study the conditions required to maintain a stable ocean on Mars 3 Ga using a new suite of simulations. These simulations couple a 3D Global Climate Model with ocean dynamics and ice sheet flow. The model includes the main processes of the atmosphere/hydrosphere/cryosphere to investigate Mars' ancient climate. The results show that the total water content required to maintain an ocean is m, global equivalent layer, half in the ocean, half in the ice sheet. This number seems plausible if a significant amount of water has been absorbed by the ground. This could be in the form of mineral alteration, or in a deep porous reservoir. In addition, the results show that the equilibrium mass flux from the ice sheet adjacent to the northern ocean is kg/y with a very low sliding velocity (1 m/y), except for few warm regions in the lowest altitudes that could reach up to 300 m/y. Finally, the global atmosphere/hydrosphere/cryosphere equilibrium should be reached in a few 100 ky. This indicates that the ocean will have a stabilizing feedback on timescales longer than this. An extensive sensitivity study of the ice sheet was performed. This included the effects of a geothermal heat flux, viscosity and basal drag. Finally, we studied the possible effects of planetary obliquity and a reduced ocean extent.