LINEAR DUNES: ARE THEY A PRODUCT OF GLACIAL WIND REGIMES?

Dunes of linear (longitudinal, seif) types are very widespread in deserts worldwide. Today, large areas of these dunes are stabilized by vegetation, or are being actively reworked in modern wind regimes. Many large linear dunes are today out of equilibrium with modern wind regimes, as indicated by comparison of dune trends with the directions of modern sand moving winds.

An examination of published OSL and TL ages for these dunes from deserts in the Middle East, Arabia, Australia, the western and southern Sahara, the Kalahari and Namibia suggests that the cores of most of these dunes are older than 10,000 years. In many cases, large linear dunes were actively reworked (or formed) during the Last Glacial Maximum. A trend of decreasing linear dune size with time is evident from some areas (e.g. Mauritania, Namibia, Arabia).

Modeling of the winds necessary to form many linear dunes suggests strongly that many linear dunes formed during periods when seasonal high-pressure cells in sub tropical latitudes were intensified and monsoon circulations were absent or much reduced in strength. This conforms to climate model results for glacial stages.