郑州邙山黄土碳酸盐和白云石含量记录的80 ka以来季风降水变化及驱动机制  

East Asian monsoon precipitation variations over the past 80 ka revealed by carbonate and dolomite content in loess deposit at Zhengzhou(Central China)and forcing mechanism

作　　者：邵可涵 鹿化煜[1] 陈久毅 顾心婕 褚博文 伍江 弋双文[1] Shao Kehan;Lu Huayu;Chen Jiuyi;Gu Xinjie;Chu Bowen;Wu Jiang;Yi Shuangwen(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1622-1630,共9页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41690111);国家级大学生创新创业训练计划支持项目(批准号:G201910284139);国家重点研发计划项目(批准号:2016YFE0109500)共同资助。

摘　　要：揭示东亚季风气候精细变化过程和区域差异,是第四纪古气候学研究的重要内容。本文以季风影响显著的中原郑州黄土堆积上部31 m为研究对象,基于高密度光释光独立定年和619份样品的碳酸盐、白云石含量、磁化率测试,重建了约80 ka以来东亚季风降水/季风强度变化过程。黄土碳酸盐、白云石含量时间序列显示,末次间冰期末期以来,中原地区发生过数次季风降水增强事件,每次降水增强期持续时间短于岁差、偏心率等轨道周期,表明存在亚轨道时间尺度季风快速变化现象。中原黄土碳酸盐/白云石含量主要受土壤呼吸CO2的影响,土壤呼吸CO2含量由季风降水和土壤温度控制,因此,碳酸盐/白云石含量是东亚夏季风强度的良好替代指标。中原地区千年时间尺度的季风湿润和干旱事件与其他地区黄土、石笋记录具有同步性,证实在东亚季风降水核心区、中心区和边缘区千年时间尺度干湿变化的同步性,支持季风环流大空间同步增强的模式。这一季风降水型式与现代观测到的"南涝北旱"的"+-+"三极型季风降水分布不同,可能表明不同时间尺度季风降水型式有明显区别。进一步分析表明,季风降水增强/减少事件存在约22 ka和约1.6 ka的周期,表明低纬太阳辐射、大洋环流和高纬度冷事件对东亚季风的联合驱动作用。In order to fully understand East Asian monsoon variation and their regional heterogeneity at orbital to suborbital timescales,we investigate a loess-paleosol sequence(34.95°N,113.38°E)at Mangshan,Zhengzhou,Central China,which is located in monsoon central region and has a high dust accumulation rate,therefore an ideal paleoclimatic record for reconstructing the monsoon variations since the last interglaciation.We sampled upper 31 m of this loess-paleosol section at 5 cm interval(total 619 samples are obtained)and carried out analyses for carbonate and dolomite contents,using Fourier transform infrared spectroscopy.Magnetic susceptibility which is regarded as a summer monsoon proxy is also measured.On the basis of more than 100 optically stimulated luminescence(OSL)dating ages,as well as the Bacon modelling,an independent and high-resolution timescale for the loess deposition over the past ca.80 ka is established.The carbonate and dolomite contents in the loess are controlled by soil CO2 respiration,and speed of soil CO2 respiration is dominated by local precipitation and soil temperature,therefore,carbonate and dolomite content of the loess deposit can be used as proxy indicators of the East Asian summer monsoon intensity.Based on the newly obtained timescale and the paleoclimatic proxies,our records show that there are around twenty monsoon strengthened events during which there are more precipitation,and these monsoon changes have significantly influenced regional hydroecology during Late Quaternary.The synchronous variations between the monsoon rainfall in Zhengzhou and that in western Chinese Loess Plateau,and the monsoon core region,supporting consistent variations in the monsoon precipitation at millennial timescale in the monsoon core,central and marginal regions in East Asia.Our results suggest that East Asian monsoon variations are synchronous in a large-scale region at millennial timescale.Our new record does not support the"south flood and north drought"monsoon rainfall pattern dubbed"the sandwich m

关 键 词：东亚季风 千年尺度 季风降水事件 黄土碳酸盐和白云石 中原黄土 高纬和低纬联合驱动 

分 类 号：P532[天文地球—古生物学与地层学] P597.2[天文地球—地质学]