Quantitative paleorainfall reconstruction from the Chinese Loess Plateau using 10Be and magnetic susceptibility

利用 10Be 和磁化率定量重建中国黄土高原古降雨

• 批准号: 0902633
• 负责人: Warren Beck
• 金额: $ 39.97万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0902633&HistoricalAwards=false
• 关键词: Quantitative; paleorainfall; reconstruction; Chinese; Loess

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This grant improves our understanding of the hydrologic variability associated with the Asian Monsoon system in response to precessional forcing. The work generates quantitative paleorainfall reconstructions from sediments collected from the Chinese Loess Plateau region using new methods. These records provide a quantitative measure of the strength of the Asian Monsoon in a form that can be used by climate models (e.g. rainfall in mm/yr). The work focuses on the periods 80-145 kaBP and Marine Isotope Stage 11 (340-420 kaBP). Between 80-145kaBP monsoon intensity appears to have been strongly influenced by insolation forcing at precessional periods as a result of high eccentricity. During MIS 11, precessional forcing of climate is likely to have been reduced because of low eccentricity. Stable isotope records from Chinese speleothems confirm the presence of abrupt and substantial changes in precipitation between 80-145 kaBP that are highly correlated with changes in low latitude northern hemisphere summer insolation. While these stalagmite records provide well-dated high-resolution records that are clearly related to regional hydrologic changes, translating these records into a form that is easily imported into climate models is more difficult because temperature, water/rock interactions, fractionation effects during moisture transport or during speleothem precipitation, as well as moisture source effects all can influence the stable isotopes recorded in a stalagmite. Quantitative paleorainfall records are generated and used to derive an 80-ka long rainfall record from the Loess Plateau. Precipitation amount on the Loess Plateau is highly correlated with the speleothem del-18O records from Dongge and Hulu caves in S.E. China, which are widely regarded as a robust record of Asian Monsoon intensity.This study is being conducted in collaboration with the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, in Xi'An China. They will provide logistical support for the fieldwork and magnetic susceptibility measurements. 240 samples will be measured for 10Be and magnetic susceptibility at circa 500 year resolution, with higher sample resolution across boundaries showing a high rate of change of precipitation. OSL dating will be used to generate an age model which, where possible, will be fine tuned by correlation with U/Th dated speleothem isotope records. 10Be sample preparation and accelerator mass spectrometer measurements will be made at the NSF-Arizona AMS facility at the University of Arizona. Part of the work will be conducted by a graduate student at the University of Arizona, as part of a PhD project, providing educational and training opportunities for this student. By providing high-resolution paleoclimate records in a format easily incorporated into climate models, the broader impacts of this proposal help define how precessional forcing influences the Asian Monsoon intensity, leading to a better understanding of the causes of abrupt climate change. These results may also help deconvolve the competing influences that control speleothem del-18O records.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这项资助提高了我们对亚洲季风系统响应岁差强迫的水文变异性的理解。利用新方法对中国黄土高原区沉积物进行定量古降水重建。这些记录以气候模式可以使用的形式（例如以毫米/年为单位的降雨量）提供了亚洲季风强度的定量测量。重点研究80 ~ 145kabp和海相同位素第11阶段（340 ~ 420kabp）。80-145kaBP之间的季风强度似乎受到高偏心率引起的进动期日照强迫的强烈影响。在MIS 11期间，由于偏心率低，气候的岁差强迫可能已经减弱。中国岩洞的稳定同位素记录证实了80 ~ 145 kaBP期间降水的突变和实质性变化，与北半球低纬度夏季日照的变化高度相关。虽然这些石笋记录提供了与区域水文变化明显相关的年代确定的高分辨率记录，但将这些记录转化为易于导入气候模式的形式更为困难，因为温度、水/岩石相互作用、水分输送或洞穴降水过程中的分馏效应以及湿气源效应都会影响石笋中记录的稳定同位素。生成了定量的古降水记录，并用于推导黄土高原80 ka长的降水记录。黄土高原降水与中国东南东歌洞和葫芦洞delo - 18o记录高度相关，后者被广泛认为是亚洲季风强度的可靠记录。本研究与中国科学院西安地球环境研究所黄土与第四纪地质国家重点实验室合作进行。他们将为实地工作和磁化率测量提供后勤支持。240个样品将以大约500年的分辨率测量10Be和磁化率，样品分辨率越高，表明降水变化率高。OSL定年将用于生成一个年龄模型，在可能的情况下，该模型将通过与U/Th定年的洞穴同位素记录的相关性进行微调。样品制备和加速器质谱仪测量将在亚利桑那大学的NSF-Arizona AMS设施进行。部分工作将由亚利桑那大学的一名研究生进行，作为博士项目的一部分，为该学生提供教育和培训机会。通过提供一种易于纳入气候模型的格式的高分辨率古气候记录，该建议的更广泛影响有助于定义岁差强迫如何影响亚洲季风强度，从而更好地理解气候突变的原因。这些结果也可能有助于反卷积控制del-18O记录的洞穴的竞争影响。