Scale-Dependent Coupling Between Aeolian Form And Flow

Andrew Lewis Gunn, University of Pennsylvania


Where there are erodible and durable grains and sufficiently strong winds to move them, erosion and deposition produces dunes. Dune fields are a coarsening pattern that defines large swaths of planetary landscapes. They exchange momentum and heat with the atmosphere, which in turn alters winds, creating a coupling between flow and form at the planetary surface. In this dissertation I investigate how surface properties of dune fields alter the winds that produce them, what conditions are necessary for dune growth and if it saturates, and how dune fields may respond to changing climate in the near future. These studies use a blend of scientific methods and are framed as problems in dynamics; investigations of non-uniformity, non-stationarity, saturation and thresholds. I show how the atmospheric boundary layer’s response to the roughness and low thermal inertia of dune fields creates spatial and temporal heterogeneity in dune-field activity, respectively. I argue that Earth’s dune coarsen indefinitely, predict that they will become less active during this century, and put bounds on the requisite winds and grain properties for their existence on bodies in the Solar System. This dissertation offers novel and generic contributions to the field of aeolian geomorphology applicable at the dune-field scale.