Decoupling of Rub’ al Khali Quaternary dune record and paleoclimate

The climate history of wind-blown dune fields is commonly determined by dune morphology, stratigraphy and age. These properties in the Rub’ al Khali have been used to interpret climate history relevant to human dispersal and monsoon variability during the glacial cycles. An underlying assumption of some of these interpretations is that the time it takes dunes to respond to a change in climate is shorter than the time over which climate changes. Here we show that this assumption does not always hold. We do this by comparing the bedform reconstitution time T_r (i.e., the time taken for sand to be completely reworked within a dune) to a climate persistence time T_c (i.e., how long dune-relevant wind properties stay the same). T_r is found using modern wind reanalysis and topography data, and T_c using paleoclimate simulations. Where T_r>T_c, climate varies too fast to be recorded in dune properties. In some areas of the Rub’ al Khali, T_r is longer than the time between glacial cycles, so dune properties and modern climate are decoupled. We extend this case study to a general theory to assess if wind-blown dunes properties can be used to interpret past climate.