青藏高原中西部湖泊生物标志物记录的过去两千年气候变化

Climatic Changes During the Past 2000 Years Based on Lake Biomarkers from the Central and Western Tibetan Plateau

  • 摘要: 以青藏高原中西部湖泊达则错和阿翁错为研究对象,通过分析湖泊沉积物岩芯中GDGTs、长链不饱和烯酮与叶蜡化合物单体氢同位素等生物分子标志物获得过去2000 a以来青藏高原中西部定量的温度与降水同位素记录,以期探讨晚全新世以来不同时段青藏高原气候变化区域特征,并揭示过去2000 a季风与西风对青藏高原影响范围的变化.结果表明:(1)青藏高原气候变化存在强烈的区域性特征,两个湖泊均存在中世纪暖期(MWP),但是暖期持续的时间有所不同,高原西部(阿翁错) MWP持续时间明显长于高原中部(达则错);达则错有明显的小冰期(LIA)降温,阿翁错没有发现明显的LIA,可能受样品分辨率低的影响;过去200 a达则错温度有缓慢降低趋势,可能是冰融水补给湖泊温度变化滞后于气候变化的表现.(2)过去2000 a印度夏季风在青藏高原的最北界线可能发生了北移,在距今1000~2000 a,夏季风边界线位于阿翁错以北、达则错以南;但在过去1000 a印度季风边界线移动到阿翁错和达则错以北.

     

    Abstract: Based on the analysis of bio-molecular markers (including GDGTs,long chain alkenone and leaf waxes) in lake sediments,Dagze Co on the central Tibetan Plateau (TP) and Aweng Co on the Western TP were selected to investigate climate changes during the past 2000 years.Quantitative temperature records and precipitation isotope records on the west and central TP had been obtained to investigate the regional patterns of climate changes during the past 2000 years,and to understand the influence of monsoon and westerly jet on the climate changes on TP.The results were achieved as follows:(1) there were strong regional characteristics of climate change on the TP.Both lakes had a Medieval Warm Period (MWP),but the duration of the MWP in the western plateau (Aweng Co) was obviously longer than that in the middle TP (Dagze Co).Dagze Co had a significant Little Ice Age (LIA) cooling,which did not find in the Aweng Co.This may be affected by the low resolution of the Aweng Co sediments.During the past two hundred years,there was a slightly cooling trend in Dagze Co,and the infusion of glacial meltwater may be the reason which delayed the temperature change in the ice melting lake.(2) During the late Holocene,the boundary of the summer monsoon on the TP may have changed.During the 1000~2000 cal.yr BP,the boundary of the summer monsoon located in the north of Aweng Co and the south of Dagze Co;whereas during the past 1000 years the boundary moved to the north of Aweng Co and Dagze Co.

     

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