青藏高原全新世气候环境变化的冰川、冰缘和湖泊沉积记录

全新世是地球历史上最新的一个间冰期,历时已有一万余年。期间,伴随着气候与环境的快速变化,人类文明也呈现出快速的演化,当前全球气候变暖导致人类生存环境的急剧变化已引起全球各国政府和科学家的广泛而深刻的关注和研究。然而,全新世期间曾多次出现气候波动阶段,对全新世这一间冰期气候与环境变化过程和机制的研究就有着十分重要的意义,可为现代气候变暖及其影响提供科学借鉴。地处中低纬度的青藏高原这一高耸的巨大地块,堪称"地球第三极",是一个集冰川、多年冻土、湖泊同时共存的特殊区域,受人类活动直接影响较弱,其冰川进退变化、多年冻土形成与消融、湖泊扩张与萎缩的变化过程则敏感地记录着气候与环境的自然变化。在多年对青藏高原冰川、冰缘和湖泊沉积与地貌的考察研究资料基础上,把冰川进退、冰缘地貌的发育和湖泊连续沉积的记录进行综合分析、相互对比印证,指出青藏高原全新世间冰期气候与环境变化的不稳定性,期间明显存在着千年和百年的波动变化,在距今8000～8500年、6000～5500年、4000～4500年左右、3000～2000年左右以及600～100年都存在明显的冷期。因此,在青藏高原,全新世气候存在着较大幅度的波动,从冰川前进幅度所需零平衡线下降值和多年冻土下界下降幅度来大致估算,温度的波动幅度至少也在3.5～5.0℃左右,甚至更大。

GEOLOGICAL RECORDS FOR HOLOCENE CLIMATIC AND ENVIRONMENTAL CHANGES DERIVED FROM GLACIAL,PERIGLACIAL AND LAKE SEDIMENTS ON QINGHAI-TIBETAN PLATEAU

Holocene is called as an epoch of interglacial with a time period of about 10000 years.With strong climate fluctuations during this epoch,human civilization has emerged and dramatically advanced.However,climate warming at present day has drawn all governments and scientists concerns over the world to pay great attention to this situation.IPCC has published several versions of evaluation about climate warming and its impact on human society.However,climate fluctuated frequently in tens-year,century or millenary cycles during Holocene period.Therefore,processes and mechanics of climate fluctuation during the Holocene period are basic scientific problems which needs to be well understood for predicting and modeling climate changes and its impact in the future.As glaciers,permafrost and lakes existed simultaneously,Qinghai-Tibetan Plateau is a very sensitive place for natural climate changes due to rare human activities on the Plateau,which is called as the third pole of the earth despite its low and middle latitude.Based on lot of data about glacier advances and retreats,periglacial geomorphological phenomena and lake sediment records on the Qinghai-Tibetan Plateau,the evidence of Holocene climate fluctuations has been summarized.It is revealed that the climate and environment on the Qinghai-Tibetan Plateau in Holocene was unstable and experienced several warm-cold fluctuations.Several cold periods in Holocene,e.g.around 8000～8500aB.P.,6000～5500aB.P.,4000～4500aB.P.,3000～2000aB.P.and 600～100aB.P.(Little Ice Age),have been revealed.The lower limit of permafrost on the northeastern margin of the Plateau declined about 700～800m in these cold periods except of Little Ice Age,which means the annual mean air temperature would be dropped about 3.5～5.0℃ even more.