TLS in Aeolian Environments: Elucidating Process-Form Feedbacks in Dusty Deserts

Abstract:

Playas (or salt pans) have the potential to be major dust and evaporation sources, modifying weather, climate and posing a health risk, but model predictions are confounded by the temporal and spatial heterogeneity of these surfaces. Playas are typically crusted and the shape of these crusts changes through time. Here we show examples of playa crusts monitored by terrestrial laser scanning (TLS) over hours, days, months and years, detecting changes of up to 30 mm/week. This modifies the aerodynamic roughness by as much as 3 mm/week which can change dust emission potential by 350%. Along with surface elevation, we also use TLS to infer relative surface moisture patterns. This novel use of TLS enables the detection of feedbacks between surface roughness, moisture and pattern development. During periods of low temperature and high relative humidity (typically winter evenings), atmospheric, subsurface and surface interactions lead to changes in inter-pore moisture which help to modify roughness, particularly where polygonal ridges have been initiated. On closed, flat surfaces or during warmer spring conditions, these changes are less noticeable. The high resolution and moisture sensitive capabilities of TLS enable us to identify these interactions and feedbacks for the first time.