Greedy parabolics: How effectively do parabolic dunes steer incident wind flow?

Parabolic dunes are U or V shaped aeolian landforms that form on pre-existing sand deposits. Their morphology consists of an upwind deflation basin, bordered by often-vegetated trailing arms and a downwind depositional lobe. The orientation of parabolic dunes commonly aligns and is attributed to prevailing or the resultant wind direction. As a result, the orientation of parabolic dunes stabilised by vegetation growth has been used as a proxy for wind direction during past climates in a number of studies. However, the effectiveness of the morphology of parabolic dunes to steer incident wind flow remains unquantified. By systematically modelling near surface wind flow using 3D Computational Fluid Dynamics over three parabolic dunes for a range of incident wind directions, we demonstrate that parabolic dunes are capable of steering incident wind flow so that it aligns with the deflation basin of the parabolic dune. These results thereby question the validity of using vegetated parabolic dunes as a proxy for paleo wind conditions. Quantifying the ability of parabolic dunes to steer incident wind flows is important not only for the identification of paleo-wind directions but also to better understand how the orientation of parabolic dunes and overall dune evolution is likely to change in the future.