A reanalysis of water abundances in the Martian atmosphere at high obliquity

Abstract

We take a new look at expected atmospheric water vapor abundances on Mars during periods of high obliquity using the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model. For the first time, the sublimation and burial of the present‐day residual polar caps beneath a sublimation lag is considered as the planet shifts from lower to high (45°) obliquity periods. Following the elimination of the polar deposits, the only sources for atmospheric water at high obliquity are the low latitude ice deposits emplaced prior to elimination of the polar source. Annual average water vapor abundances are predicted to be only ∼20–80 prμm during extended periods of high obliquity, one to two orders of magnitude less than previous estimates. This has implications for the climate history of the planet as it suggests that during extended periods of high obliquity, there is not a significant greenhouse warming effect from elevated atmospheric water vapor.