The distribution of Earth’s wind-blown sand dunes

Andrew Gunn 

Sand dunes develop when there is a source of sediment and wind capable of saltating that sediment. Dune morphology and occurrence can then be used to infer the distribution of sediment sources and climate conditions during their formation. This is particularly useful for inference of past climate from relict dunes or the sedimentary record, and for climate conditions where direct observation is challenging on Earth or other planets. However, to date, there has been no complete and accurate global map of the occurrence of Earth's sand dunes with distinguishable morphologies. Here we present that map and use it to demonstrate quantitatively that in arid environments dune presence is mostly explained by convergent transport and source proximity, whereas in more humid climates wind strength is an additional constraint. By limiting our analysis to dunes with morphologies discernible from global publicly available imagery and topographic data, we produce a consistent dataset which can be used to infer myriad aspects of geology and climate, and improve understanding of processes in, and development of, aeolian landscapes. We provide an example, using the orientation of barchan dunes, to demonstrate a trade-off between inference of sediment and wind characteristics.