Recent Ice Ages on Mars: The role of radiatively active clouds and cloud microphysics

Jean-Baptiste Madeleine (1, 2, 3) , James W. Head (3) , François Forget (2) , Thomas Navarro (1) , Ehouarn Millour (1) , Aymeric Spiga (1, 2) , Arnaud Colaïtis (1) , Anni Määttänen (4) , Franck Montmessin (4) , James L. Dickson (3)

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
2 IPSL - Institut Pierre-Simon-Laplace
3 Department of Geological Sciences [Providence]
4 PLANETO - LATMOS

Global Climate Models (GCMs) have been successfully employed to explain the origin of many glacial deposits on Mars. However, the Latitude Dependent Mantle (LDM), a dust-ice mantling deposit that is thought to represent a recent "Ice Age", remains poorly explained by GCMs. We reexamine this question by considering the effect of radiatively active water-ice clouds (RACs) and cloud microphysics. We find that when obliquity is set to 35°, as often occurred in the past 2 million years, warming of the atmosphere and polar caps by clouds modifies the water cycle and leads to the formation of a several centimeter-thick ice mantle poleward of 30° in each hemisphere during winter. This mantle can be preserved over the summer if increased atmospheric dust content obscures the surface and provides dust nuclei to low-altitude clouds. We outline a scenario for its deposition and preservation that compares favorably with the characteristics of the LDM.

Mots clés: Climate; Glaciation; Mars; Paleoclimate; Climate model; Clouds

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

Jean-Baptiste Madeleine, James W. Head, François Forget, Thomas Navarro, Ehouarn Millour, et al.. Recent Ice Ages on Mars: The role of radiatively active clouds and cloud microphysics. Geophysical Research Letters, 2014, 41 (14), pp.4873-4879. ⟨10.1002/2014GL059861⟩. ⟨hal-01023522⟩