Comparison of paleotemperature reconstructions using microbial tetraether thermometers of the Chinese loess-paleosol sequence for the past 350000 years
Comparison of paleotemperature reconstructions using microbial tetraether thermometers of the Chinese loess-paleosol sequence for the past 350000 years
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DOI：
10.1007/s11430-016-9035-y
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发表时间：
2017-04
期刊：
影响因子：
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通讯作者：
Chang Tang;Huan Yang;X. Dang;S. Xie
中科院分区：
文献类型：
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作者：
Chang Tang;Huan Yang;X. Dang;S. Xie
最近提出的全球和本地校准的基础上重建的年平均气温（MAT）的5-和6-甲基brGDGT很少被应用到中国LPS，离开这些校准的适用性不清楚。本文采用改进的色谱分析方法，分析了华北地台南部渭南剖面35万年来198个黄土-古土壤样品。6-甲基brGDGT占总brGDGT的主要比例，这表明渭南LPS中大多数土壤样品的碱性条件。MBT′ 6 ME和MBT′ 5 ME的非耦合剖面变化表明它们分别对不同的环境因子，可能是土壤pH（或土壤湿度）和温度的响应。这一区别进一步证实，温度和季风降水在CLP的最后四个冰消期的阶段。测试的六个校准的温度估计值显示出类似的趋势，但幅度显着不同。土壤湿度影响了全球MBT′/CBT、全球MATmr和中国局部SSM（逐步选择法）的校正结果，导致晚全新世温度明显偏低。相反，干燥的气候对全球MBT′ 5 ME校准没有影响。在这6个基准中，只有中国局部SSM和全球MATmr两个基准的温度变化幅度与其他独立的代用数据一致。最近提出的本地校准的基础上5-和6-甲基brGDGT华北产量的温度变化的幅度是远远大于其他方法确定的结果。这6种标定方法在MAT重建中均存在不足，部分原因在于渭南LPS中的brGDGT分布与用于建立这些标定方法的现代土壤的brGDGT分布不一致。
The recently proposed global and local calibrations for the mean annual air temperature (MAT) reconstruction on the basis of 5- and 6-methyl brGDGTs have rarely been applied to the Chinese LPS yet, leaving the applicability of these calibrations unclear. Here, we used the improved chromatography method to analyze 198 loess-paleosol samples from the Weinan section in the southern CLP for the past 350 kyr. The 6-methyl brGDGTs comprise a major proportion of total brGDGTs, pointing to alkaline conditions for most soil samples from the Weinan LPS. The decoupled profile variation of MBT′6MEand MBT′5MEsuggests their response to different enviromental factors, possibly soil pH (or soil moisture) and temperature, respectively. This discrimination further corraborates that temperature and monsoonal precipitation were not in phase during the last four deglaciations on the CLP. Temperature estimates for the six calibrations tested show similar trends but remarkably differ in amplitudes. The soil moisture appears to affect the global MBT′/CBT calibration, the global MATmrcalibration (a calibration based on the multiple linear regression) and the Chinese local SSM (Stepwise Selection Method) calibration, resulting in a significant underestimation of late Holocene temperature. In contrast, the dry climate has no effect on the global MBT′5MEcalibration. Of the six calibrations, only the Chinese local SSM calibration and global MATmrcalibration produce temperature variation amplitude over the past 350 ka that is consistent with other independent proxy data. The recently proposed local calibrations based on 5- and 6-methyl brGDGTs for North China yield the amplitude of temperature changes that is much larger than the results determined by other approaches. All the six calibrations have their own weakness in the MAT reconstruction, due partly to the inconsistency between the brGDGT distribution in the Weinan LPS and the modern soils used to establish these calibrations.