西宁黄土白云石和碳同位素记录的轨道尺度季风气候变化  

THE MONSOON VARIATIONS AT ORBITAL TIMESCALE REVEALED BY DOLOMITE CONTENT AND STABLE CARBON ISOTOPIC COMPOSITION OF LOESS FROM XINING(NORTHEASTERN QINGHAI-TIBETAN PLATEAU)

作　　者：王素素 鹿化煜[1] 王珧[1] 王先彦[1] 张肖剑 王晓勇[1] Wang Susu;Lu Huayu;Wang Yao;Wang Xianyan;Zhang Xiaojian;Wang Xiaoyong(School of Geography and Ocean Science,Nanjing University,Nanjing 210023,Jiangsu)

机构地区：[1]南京大学地理与海洋科学学院,江苏南京210023

出　　处：《第四纪研究》2020年第6期1453-1463,共11页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41690111、41888101和41920104005);国家重点研发计划项目(批准号:2016YFE0109500)共同资助。

摘　　要：第四纪轨道尺度东亚季风变化的主控周期及其驱动机制还没有一致的认识,高纬地区冰量和低纬岁差变化如何驱动季风气候变化没有定论。沉积过程连续、堆积速率快的黄土-古土壤序列是揭示轨道时间尺度季风气候变化的良好材料。我们选择青藏高原东北部西宁泮子山黄土堆积上部的60 m作为研究对象,通过钻探取样和分析最近280 ka以来黄土-古土壤序列的磁化率、碳酸盐含量、白云石含量、碳酸盐碳同位素等古气候代用指标,探讨青藏高原东北部东亚夏季风气候的变化规律和控制因素。利用频谱和小波分析方法对季风气候变化的时间序列进行分析。结果显示,最近280 ka以来东亚夏季风变化具有轨道尺度的变化周期,并与高纬冰量和北半球温度变化有一定的联系;同时,西宁黄土古气候时间序列具有显著23 ka的岁差周期,表明低纬过程对东亚季风的重要作用。岁差调制的低纬太阳辐射变化可能是驱动青藏高原东北部轨道尺度季风降水变化的主导因素,高纬冰量和温度变化对轨道尺度的季风变化也有一定的影响。East Asian summer monsoon(EASM)is an important component of Earth's climate system,which significantly influences the production and life of billion-plus populations over East Asia.East Asian monsoon variability and associated forcing mechanisms are the focus and frontier of Earth system science.Orbital timescale variability and forcing mechanisms of the EASM from paleoclimatic reconstructions still remain elusive.Previous studies revealed that precession-band variance is not the dominated frequency in loess records,while eccentricity-band is missing in high-resolution speleothem records.Whether loess deposit can record monsoon variability on a precession timescale largely depends on sedimentation rate and post-depositional processes that can attenuate the variability of the loess proxies.In this study,we chose the upper 60 m of the loess core located at Panzishan(PZS)(36.649°N,101.844°E;2728 m a.s.l.),Xining Basin in the northeastern Qinghai-Tibetan Plateau,where the dust sedimentation rate is high.A total of 272 samples were taken at an interval of 20 cm in this section.The depth-age model was constructed based on linear interpolations,and detail correlations between the grain size variations of the loess and the grain size time series of Luochuan.We present the grain size distribution,magnetic susceptibility,carbonate content,dolomite content and δ^(13)C of carbonate of the loess-paleosol samples to reconstruct the EASM changes at Xining.The carbonate content and dolomite content are negatively related to rainfall.The δ^(13)C of loess carbonate is related to soil respiration flux which was determined by the EASM intensity,therefore it is an ideal proxy of EASM in the northeastern Qinghai-Tibetan Plateau.Compared with magnetic susceptibility,carbonate content,dolomite content and δ^(13)C can detect the same order of wet events during the last 280 ka.Our results show that these proxy records exhibit significant orbital timescale fluctuations,and linking the EASM with the high-latitude ice sheets in Northern

关 键 词：东亚季风 青藏高原东北部 黄土碳同位素 岁差 低纬驱动 

分 类 号：P532[天文地球—古生物学与地层学] P534.631[天文地球—地质学]