Katabatic jumps in the Martian northern polar regions

• Published in: Icarus
• Main Authors: Spiga, Aymeric, Smith, Isaac
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Planetary Science Institute Tucson (PSI)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology; Loewe; Antarc*
• Online Access: https://hal.sorbonne-universite.fr/hal-01643458; https://hal.sorbonne-universite.fr/hal-01643458/document; https://hal.sorbonne-universite.fr/hal-01643458/file/draft.pdf; https://doi.org/10.1016/j.icarus.2017.10.021

International audience Martian polar regions host active regional wind circulations, such as the downslope katabatic winds which develop owing to near-surface radiative cooling and sloped topography. Many observations (stratigraphy from radar profiling, frost streaks, spectral analysis of ices) concur to show that aeolian processes play a key role in glacial processes in Martian polar regions. A spectacular manifestation of this resides in elongated clouds that forms within the polar spiral troughs, a series of geological depressions in Mars’ polar caps. Here we report mesoscale atmospheric modeling in Martian polar regions making use of five nested domains operating a model downscaling from horizontal resolutions of twenty kilometers to 200 m in a typical polar trough. We show that strong katabatic jumps form at the bottom of polar troughs with an horizontal morphology and location similar to trough clouds, large vertical velocity (up to +3 m/s) and temperature perturbations (up to 20 K) propitious to cloud formation. This strongly suggests that trough clouds on Mars are caused by katabatic jumps forming within polar troughs. This phenomena is analogous to the terrestrial Loewe phenomena over Antarctica’s slopes and coastlines, resulting in a distinctive “wall of snow” during katabatic events. Our mesoscale modeling results thereby suggest that trough clouds might be present manifestations of the ice migration processes that yielded the internal cap structure discovered by radar observations, as part of a “cyclic step” process. This has important implications for the stability and possible migration over geological timescales of water ice surface reservoirs—and, overall, for the evolution of Mars’ polar caps over geological timescales.