Optical dating reveals that the height of Earth’s tallest megadunes in the Badain Jaran Desert of NW China is increasing

The Badain Jaran Desert (BJD) in NW China is well known for its unique landscape of megadunes coexisting with permanent lakes. The megadunes are already the tallest sand dunes on earth, and some of them are up to 400 m high. However, it is unclear whether or not the height of the megadunes is continuing to increase under present climatic and environmental conditions. In order to determine the growth status of the megadunes, we collected 26 samples from the windward slopes of two megadunes for optically stimulated and infrared stimulated luminescence dating. The results show that the thickness of the modern eolian sand layers increases from the lower part of the windward slopes, with a thickness of less than 1 m, to more than 2 m in the middle, and to 9 m in the upper part. This indicates that the height of the megadunes is continuing to increase under modern conditions. The surface sediments from the base of the windward slope and the adjacent lake basin have relatively old ages of 6–7 ka, indicating that these areas are eroding. The recent eolian sands of the upper part of the megadunes likely originated from the base of the dunes or from the lake basin. The megadunes in the BJD are currently becoming increasingly high and steep due to the upward migration and accumulation of sand particles. Increased humidity and a weakened wind regime in northern China, related to ongoing climatic warming, are likely the main factors in maintaining the growth of the megadunes.