Dunes as lndicators of Climatic Change

Relatively simple geometrical patterns of sand-dune morphology in modern sand seas can be used to infer past climatic change, including changes in the direction of prevailing winds and to a lesser extent, of long-term humidity. After time spans of several millenia since they were formed, especially the larger (mega) dunes of many areas are out of equilibrium with modern wind systems, and as a result their original morphology has been altered. The reason for these changes in wind direction is associated with the growth and collapse of Northern Hemisphere glaciations, which had a periodicity of about 100 ka during the later Quaternary, and the effect that they had on global wind systems. The Emirates, situated in the path of an important sand-transporting wind, is in an ideal location for showing these effects. The Arabian Gulf dried out during the last and earlier glaciations, and had carbonate-rich dunes migrating over its exposed floor; that supply of sand ceased with each post-Glacial flooding, causing deflation of dunes immediately down wind of the new coast. Gypsum-rich plant-root moulds indicate proximity to a desert water table, which could signal a change from interglacial humidity to a more arid climate.