Direct validation of dune instability theory

Abstract

Modern dune fields are valuable sources of information for the large-scale analysis of terrestrial and planetary environments and atmospheres, but their study relies on understanding the small-scale dynamics that constantly generate new dunes and reshape older ones. Here we designed a landscape-scale experiment at the edge of the Gobi desert, China, to quantify the development of incipient dunes under the natural action of winds. High-resolution topographic data documenting 42~months of bedform dynamics are examined to provide a spectral analysis of dune pattern formation. We identified two successive phases in the process of dune growth, from the initial flat sand bed to a meter-high periodic pattern. We focus on the initial phase, when the linear regime of dune instability applies, and measure the growth rate of dunes of different wavelengths. We identify the existence of a maximum growth rate, which readily explains the mechanism by which dunes select their size, leading to the prevalence of a 15~m-wavelength pattern. We quantitatively compare our experimental results to the prediction of the dune instability theory using transport and flow parameters independently measured in the field. The remarkable agreement between theory and observations demonstrates that the linear regime of dune growth is permanently expressed on low-amplitude bed topography, before larger regular patterns and slip faces eventually emerge. Our experiment underpin existing theoretical models for the early development of eolian dunes, which can now be used to provide reliable insights into atmospheric and surface processes on Earth and other planetary bodies.

36 pages, 19 figures (supplementary material included)

References in corpus (14)

• A Continuum Saltation Model for Sand Dunes
• A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples
• Selection of dune shapes and velocities. Part 1: Dynamics of sand, wind and barchans
• Minimal Model for Sand Dunes
• Minimal size of a barchan dune
• A unified model of ripples and dunes in water and planetary environments
• Flux saturation length of sediment transport
• Giant ripples on comet 67P/Churyumov-Gerasimenko sculpted by sunset thermal wind
• Field evidence for the upwind velocity shift at the crest of low dunes
• Profile measurement and simulation of a transverse dune field in the Lençóis Maranhenses
• Incipient bedforms in a bidirectional wind regime
• Spatial and temporal development of incipient dunes
• Periodicity in fields of elongating dunes
• Dune initiation in a bimodal wind regime

Cited by in corpus (7)

• Local Wind Regime Induced by Giant Linear Dunes: Comparison of ERA5-Land Reanalysis with Surface Measurements
• Coevolving aerodynamic and impact ripples on Earth
• Coexistence of two dune growth mechanisms in a landscape-scale experiment
• Field evidence for the initiation of isolated aeolian sand patches
• Basal pressure variations induced by a turbulent flow over a wavy surface
• From lab to landscape-scale experiments for the morphodynamics of sand dunes
• Modeling the dynamics of aeolian meter-scale bedforms induced by bed heterogeneities