What is the fate of snow trapped in dunes?
thesisposted on 14.05.2019, 00:00 authored by John Westenhoff
Active sand dune fields in cold climate regions commonly incorporate snow and ice from winter precipitation into their internal structure. Sediment transported by dune movement can bury snow, protecting it from solar input and warming. The hydrological importance of this system is not well studied, in particular the ability of such a system to trap and preserve ice that may be later be as stored groundwater. This ice trap may be important for understanding desert ecosystems on Earth, but may also represent an analog mechanism for buildup of ice below the mid-latitude surface of Mars. Electrical Resistivity Tomography (ERT) imaging was used to investigate the depths of a dune for ice layers in the Red Desert, Wyoming. Data loggers were used to monitor the temperatures and moisture contents of the subsurface surrounding directly observed ice lenses within the dune. The ERT survey revealed that subsurface ice lenses are not incorporated into the dune over long periods. This was consistent with the results of two consecutive seasons of data logger data, which revealed a three-stage life cycle of the ice lens, with eventual complete disappearance of ice in the dune by the end of the warm seasons. Nuclear Magnetic Resonance (NMR) logging revealed an increasing water content of the dune with depth under ice lenses. This transport and entrapment mechanism for protected snow represents a possible explanation for observations of shallow subsurface ice at mid latitudes on Mars.