External supply of dust regulates dust emissions from sand deserts

•External dust supply is an important dust contributor to sand deserts.•Dust density current leads to dust deposition on sand desert surfaces.•Human activities or climatic changes regulate dust processes of sand deserts.

Dust emission from the sand desert is an important contributor to long-term atmospheric dust loading. The source of desert dust has been previously attributed to the aeolian abrasion of sand grains during wind-blown sand activities. The abrasion rate, however, tends to decrease as the grain roundness increases with abrasion time, and shows unable to produce an adequate supply of dust to support long-term dust emission. Here we show that an external dust supply is also an important dust contributor to the sand desert, and that dust emission from the sand desert will occur if an external dust supply is available and diminish if the external supply is cut off. Our results relate the dust emission from sand deserts to an external dust supply resulting from disturbed processes or changed hydrological processes caused by climate changes or human activities, and also suggest that the dust emission rate of natural sand deserts can actually increase with external dust supply resulting from human activities or climatic changes, rather than with wind energy alone, as is commonly perceived.