干旱区生态环境知识资源中心

The Siberian High (SH) and the westerlies interact in the central-east Asia and jointly influence the aeolian variations in the Northern Hemisphere. However, the spatiotemporal variations of the two climatic systems, as well as their interaction, are still unclear. Here, we present a reconstruction of the variation of two systems during the past 1200 kyr based on grain-size analyses of multiple aeolian sequences from central-east Asia along the path of the westerlies and from the area downwind of the SH. The results show that the SH and the resulting winds exhibited a stepwise enhancement at 900,700 and 300 ka, and that the SH expanded significantly towards western China at 300 ka. In addition, the westerlies dominated western China as far east as the Badain Jaran area during 1200-500 kyr with an enhancement at 900 ka, and then gradually weakened following a striking enhancement at 500 ka; subsequently, their influence on aeolian activity in western China progressively decreased and was replaced by an enhanced SH at 300 ka. With the gradual increase of the SH at 700 and 300 ka, its influence reached the altitude of the westerlies and thus significantly affected the westerlies dust size. The mid-Pleistocene uplift of the Tibetan Plateau (1200-600 kyr) intensified the SH and resulted in the blocking of the westerlies, weakening the wind strength and producing dry conditions in western China at 500 ka. Increasing global ice volume is also responsible for the variations and interplay of SH and westerlies, especially at 300 ka.