Sublimation and ice condensation in hyperarid soils: Modeling results using field data from Victoria Valley, Antarctica

Most soils of the Dry Valleys of Antarctica are ice-cemented within a few decimeters of the ground surface despite the hyperarid conditions. This fact brings into question current sublimation models since they indicate that water vapor in soils is being lost at rates that would rid them of ice to at least several meters in less than a few thousand years, and yet most ice-rich soils in the Dry Valleys are much older. In this paper, we explore mechanisms that slow or may reverse ice loss from the soil to the atmosphere and incorporate them into a sublimation model that uses high- resolution climate and soil temperature data from 2002 to 2005 in Victoria Valley, where the surface is similar to 10 ka old and the soil is ice-cemented 0.22 m below the surface. According to this model, ice currently sublimates 0.22 mm a(-1), which corresponds to a descent of the ice cement boundary of similar to 1.2 mm a(-1). Water vapor condenses in the upper dry soil during the winter but is lost completely to the atmosphere during the austral summer. Some water vapor diffuses downward into the frozen soil, condensing at rates of 0.02 - 0.09 mm a(-1). Snow cover in the summer temporarily reverses the vapor transport and reduces the annual ice loss. Hence while snow slows long-term sublimation, the dearth of data on the duration and timing of snow cover prevent us from quantifying this effect and from assessing the potential of snowmelt to offset water loss from the soil.