Distribution and fate of Tibetan Plateau loess

Abstract

The Tibetan Plateau (TP) hosts the largest alpine ecosystem in the world, and aeolian loess is an essential component of this ecosystem and landscape. However, little is known of loess distribution and fate, owing to the climate and landscape varying dramatically between Quaternary glacial and interglacial cycles. Recent research suggests that the interior Tibetan loess did not start to accumulate until ∼14 ka, when climate warming and wetting resulted in an increase in vegetation cover, enabling dust trapping. In this study, our extensive aeolian profile review and age analysis demonstrate that loess thickness and basal ages on the TP are very different regardless of terrain and landscape. According to loess distribution, thickness, and basal ages, we divided the TP into three zones: Zone I (western TP) and Zone III (eastern TP) are the dust source and sink areas, respectively, and Zone II (central TP) is transitional. The central TP became a dust source zone during the last glacial stage but turned into a dust sink during the last deglaciation and Holocene. The modeling results confirm that each zone has its own role in dust fixation and deflation and that these three zones are systematically interlinked by dust. Glacial-interglacial precipitation and vegetation cover changes controlled the switch in Zone II (central TP). We demonstrate that dust on the TP must have experienced enhanced excavation from west to east during the past glacial periods. During the next glacial period, the eastern TP loess may continue to accumulate, but the central TP loess will be eroded after vegetation degradation and removal, leading to a serious ecological disaster. This study provides insights into Tibetan loess accumulation patterns on a large spatial scale, improving the understanding of the past of Tibet loess and enabling predictions regarding future Tibet loess.