HOW MUCH SAND IS THERE IN DESERT SAND SEAS AND DUNEFIELDS?

Estimating the volume of sediment in inland sand seas and dune fields is important for understanding their long-term development and their role in global geo-cycles. The volume of sand in an area is best represented by the equivalent sand thickness (EST), the depth of sand that would exist of the dunes were leveled and the intervening interdune areas filled by sand. The availability of high-resolution digital elevation datasets (e.g. ASTER DEM) provides a spatially consistent means to estimate EST and, in combination with GIS mapping of dune field area, total sand volume.

A data set comprising 2094 dune height and spacing measurements for the full range of dune morphologic types was derived from ASTER DEM tiles by Gunn et al. (2021). Mean EST is estimated as 40% of the mean dune height in an area and ranges from 3.65 m in the SW Kalahari to as much as 43.63 m in the Badain Jaran sand sea of NW China. The global mean sand EST is 16.03 m, compared to 14.5 m (Wilson 1973).

The volume of sand in a given dune area is the product of mean EST and area. The sampled sand seas and dune fields total an area of 3.44 x 10⁶ km³, or 49% of the global area of dunes (7 x 10⁶ km³) mapped by Lancaster et al. (2017). They contain an estimated 4.88 x 10⁴ km³ of sand, about 25% of which is contained in the Rub al Khali and adjacent areas. Extrapolating, the global total dune sand volume is in the order of 1 x 10⁵ km³. This compares with the 7 x 10⁴ km³estimate of Wilson (1973).