Numerical modeling of aeolian-dune development in carbonate island settings: exploring last interglacial environmental conditions on coastal dune morphology in The Bahamas and Turks and Caicos

Abstract This paper presents an adaptation to the Aeolian Surface Model (ASM) framework, modified to account for variable surface properties and sediment transport limitations present in coastal carbonate-dune environments. The model simulates the formation of three fossilized dune morphologies, inspired by the lithified aeolianites of late Pleistocene age across The Bahamas and Turks and Caicos Islands: compound-dune ridges, elongate parabolic dunes, and transgressive sandsheets. The ASM is a reduced-complexity numerical model that represents interactions between individual bedforms and larger topographic features to produce dune-scale and landscape-scale aeolian geomorphology. Two critical-shear-stress functions were introduced as thresholds for sediment transport and envisioned as a combined expression of moisture, carbonate cementation, and vegetation, three co-varying environmental factors that govern stabilization in coastal carbonate-dune systems. One shear-stress function remains static, which establishes the spatially variable surface roughness, while the other adjusts dynamically to prior change in bed elevation, representing the feedbacks between surface change and sediment mobility within bedforms that can arise from vegetation growth, moisture retention, or carbonate cementation. By altering these critical-shear-stress functions, the model reproduces distinct morphologies: the highest values of critical shear stress yields compound ridges, and uniform mobility forms the transgressive morphology. The elongate parabolic dune morphology was produced by moderate stabilization along with adjusting two additional boundary conditions: decreased sediment availability and expanded areas of contiguous surface stabilization. When integrated with regional geological context, numerical experiments using the ASM provide tools to interpret the environmental controls and feedbacks that shape coastal aeolian landscapes. The presence of multiple dune morphologies on individual islands likely reflects spatial or temporal variability in sediment mobility, driven by environmental factors such as carbonate-platform exposure, sediment supply, and stabilizing influences like vegetation and cementation. The ASM proves useful for testing hypotheses, exploring environmental boundary conditions, and guiding future refinements for paleo-reconstructions of aeolian landscape evolution.