Martian atmospheric collapse: Idealized GCM studies
Global energy balance models of the Martian atmosphere predict that, for a range of total CO_2 inventories, the CO_2 atmosphere may condense until a state with a permanent polar cap is reached. This process, which is commonly referred to as atmospheric collapse, may limit the time available for physical and chemical weathering. The global energy balance models that predict atmospheric collapse represent the climate using simplified parameterizations for atmospheric processes such as radiative transfer and atmospheric heat transport. However, a more detailed representation of these atmospheric processes is critical when the atmosphere is near a transition, such as the threshold for collapse. Therefore, we use the Mars Weather Research and Forecasting (MarsWRF) general circulation model (GCM) to investigate how the explicit representation of meridional heat transport and more detailed radiative transfer affects the onset of atmospheric collapse. Using MarsWRF, we find that previous energy balance modeling underestimates the range of CO_2 inventories for which the atmosphere collapses and that the obliquity of Mars determines the range of CO_2 inventories that can collapse. For a much larger range of CO_2 inventories than expected, atmospheric heat transport is insufficient to prevent the atmospheric collapse. We show that the condensation of CO_2 onto Olympus Mons and adjacent mountains generates a condensation flow. This condensation flow syphons energy that would otherwise be transported poleward, which helps explain the large range of CO_2 inventories for which the atmosphere collapses.
© 2014 Elsevier B.V. Received 10 June 2013, Revised 23 November 2014, Accepted 25 November 2014, Available online 4 December 2014 We have benefited from numerous conversations with Andrew Ingersoll and Aaron Wolf, of Caltech, and Itay Halevy, of the Weizmann Institute of Science. Additionally, the comments from the two anonymous reviewers greatly improved this paper. The simulations were performed on Caltech's Division of Geological and Planetary Sciences Dell cluster as well as the Pleiades supercomputer at the NASA Advanced Supercomputing Division at NASA's Ames Research Center. The NASA Mars Fundamental Research program, under grant NNH07ZDA001N, funded this research.