Geomorphic response to climatic and environmental changes along a Central Asian transect during the Holocene

Abstract

This paper discusses the geomorphic response to late Quaternary climatic changes, and to some extent, human impact, along an Asian transect running from Eastern Siberia via Mongolia and Tibet to India. The prevailing aridity of the Asian interior is controlled by distance from oceans and the existence of high mountain ranges, modifying the circulation of air masses. Another factor is the existence of permafrost expanding to the temperate zone. The contrasting characteristic of continentality are expressed in the asymmetry of present-day slope processes caused by differences in temperature and humidity. Differences in altitude generate altitudinal and horizontal zones. Late Quaternary climatic changes are reflected in latitudinal and altitudinal shifts in upper and lower tree lines, the snow line and the permafrost limit. The warming trend in the early Holocene, gave way to cooling in the last 3–5 ka BP. This was accompanied by a rise in humidity which started (ca. 10 ka BP) in the southern part under monsoonal influences and later (8–7 ka BP) in the northern part under the influence of westerlies. Increased aridity was more or less coincident with the later cooling trend across Asia. In recent millennia, this has been accompanied by deforestation, cultivation and overgrazing, which have in turn, caused accelerated runoff and soil erosion.