Surface airflow patterns at a barchan dune field in Hellespontus Montes, Mars

Abstract

Mobile barchan dunes are well-developed in a crater in the Hellespontus Montes region on Mars. Previous studies of their temporal evolution show that the barchans maintain their shape and migrate in a uniform pattern. Whereas barchans are typically associated with unidirectional wind regimes, the crater experiences seasonal changes in wind regime, driven by large-scale circulation patterns. Using a multi-scale modelling approach we demonstrate that the effect of upwind mesas are minimal to steering regional wind conditions, beyond the extent of the mesas themselves which limits the effect on the development and maintenance of barchan dunes further downwind. The results of high resolution CFD modelling showed individual barchan dunes had the capability to locally steer oblique wind flows along the orientation of the barchan dunes. We hypothesise that this ability of barchan dunes to ‘steer’ near surface local wind flows, combined with the uni-directional source of sediment at the site allows barchan morphology to persist in Hellespontus Montes, despite being subject to a range of incident wind directions.