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

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.