Long-term measurements of aeolian transport directional variations over a zibar surface in the northern Kumtagh Sand Sea

Abstract

Zibars are aeolian bedforms created by armoring of the surface by coarse grains. The existence and movement of these grains strongly influence zibar morphodynamics. Although aeolian sediment transport has been investigated for arid surface processes with a range of grain sizes, the measurement durations were short, making it difficult to establish the relationship between microscopic aeolian transport processes and macroscopic geomorphological processes. In the present study, we conducted field observations of aeolian sediment transport above a zibar in northern China's Kumtagh Sand Sea with a segmented sand trap. During six measurement periods throughout 2014, the sampler collected 314.76 kg of sediments within 1 m above the ground. The directional variation indicated that about 52.5% of the sediments came from the north, northeast, and northwest; the southeast provided the least sediments. The strongest aeolian transport occurred between August and October; the weakest was in winter. The aeolian sediment flux decreased with height, and 54% of particles were transported within 0.1 m above the ground. The transport profiles fit an exponential decay function. The flux's directional variation resulted from the combined effects of sediment availability and wind regime, so the calculated net transport differed from the drift potential. The seasonal and directional variations of aeolian transport significantly affect the morphodynamic process of zibars. The trend and the internal sedimentary structure of zibars were closely related to the aeolian transport process.