摘要
By means of survey of literature through compilations of sedimentological,biogeological and geomorphologic data,the inland lake level changes in arid or semi arid mainland Asia at 6 and 18 ka B.P.have been reconstructed.The results showed that the lakes from western and northwestern Asia were characterized by very high water levels at 18 ka B.P.,but low or intermediate water stands at 6 ka B.P.The high lake level in this region was associated with the southward displacement of westerlies,therefore,the extent of the high lake stand indicated the southern flank of westerlies during the glaciation.Conversely,the lakes from the eastern and southern Asia registered comparative low levels at 18 ka B.P.and significantly high one at 6 ka B.P.The lowering of lake level at 18 ka B.P.was caused by the weakened summer monsoon and the high lake level at 6 ka B.P.by the enhanced summer monsoon induced by the enlarged thermal contrast between land and ocean.The extent of high lake levels indicated the northern boundary of monsoon expansion.Between the above two regions,there is a climatic transitional zone in the Central Asia where the lake behavior was close to that in southeastern Asia at 6 ka B.P.but became similar to that in northwestern Asia at 18 ka B.P.Thus this zone became a transitional sector from the monsoon to the westerlies.
基金
the National Natural Science Foundation of China(GrantNo.49201005)
