ABSTRACT: Surface controls on aeolian sand transport in a cold-climate dunefield.

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In cold-climate dunefields dramatic changes in surface conditions control the speed of wind required to initiate sand transport (entrainment threshold). Complex and interacting factors include ground freezing, snow cover, variable soil moisture, and seasonal changes in vegetation. Since entrainment threshold forms the basis of formulas used to estimate sand transport and landform morphodynamics, a reliable predictive model relating threshold to meteorological conditions is critical. To resolve this, we initiated a research project in 2008 with a study site located in the Bigstick Sand Hills of Saskatchewan. Data are collected by an erosion monitoring system every 5 minutes. This system measures: saltating sand, sand flux, wind speed and direction, air and ground temperature, soil moisture, relative humidity, solar radiation, and precipitation. Two sites (vegetated and bare sand) are simultaneously monitored to isolate the influence of vegetation growth and dormancy. In addition, a digital camera records photographs of surface conditions. Preliminary results reveal that the entrainment threshold varies between 5-9 m/s (measured at 2 m height). Variability occurs at sub-hour timescales throughout the day and has strong correlations with snow cover and ground freezing, and weak correlations with solar radiation and air temperature. As expected, these data demonstrate that entrainment threshold cannot be considered constant. Thus, with the creation of an empirical model, the accuracy of sand transport equations will be substantially improved, and this research will provide essential insight into how surface conditions can affect the morphodynamics of cold-climate dunefields.

Bibliography of Canadian Geomorphology