Pilot Project: Reconstructing tropical North American climate with the sedimentary record of Lake Chalco, Mexico

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。该项目研究了墨西哥中部查尔科湖的沉积序列，以开发约50KYR的北美热带陆地气候变异性记录。该项目使用了反映水文和热力变化的指标，特别侧重于从末次冰川盛期到全新世的过渡。该项目是与墨西哥自治大学合作的，后者在钻探计划的第一阶段回收了约100米的钻芯。随后的钻探可能会将其延长100米，将包括前两次间冰期在内的记录回溯到约300ka。这一试点项目的重点是早先回收的岩心最上面的50米。这些分析包括X射线荧光岩心扫描和一系列有机地球化学分析，包括50ka以来约1000年分辨率的MBT(古温度)、生物标志物del-D(干旱)、木质素和生物标志物del-13C(植被响应)。这项工作为这个网站提供了一个“概念证明”，并提供了一个独特的信息，关于一个气候记录稀少的地区自MIS3中期以来的过去温度和降水量。中国铝业的气候记录应该能为区域应对过去耦合气候系统的变化提供洞察力。南极冰芯最近的研究记录了中更新世大气二氧化碳浓度和气候变化的显著差异(EPICA 2005，Siegenthaler，2005)，但跨越这一时间间隔的高分辨率大陆记录在全球范围内很少见，在北美也没有。中国铝业的完整记录有可能提供独特的信息，填补这一关键空白，提高我们对当前间冰期及其未来进程的了解。该项目通过研究生和本科生的直接支持，为培养下一代地球科学家做出了贡献。这项研究还促进了美国和墨西哥科学界之间的国际合作；墨西哥学生将来到大湖天文台从事这一项目。对科学界的广泛影响包括重建墨西哥中部过去35个基年的气候历史，以及验证MBT古温度指标在墨西哥湖泊系统中的应用。现代全球气候变化预测的气温上升将对下个世纪的自然系统和人类人口产生重大影响。更好地了解气候系统过程以及它们如何反映在地球化学替代记录中，有助于模拟未来的气候趋势。经过严格调查的替代物的适当应用，提供了目前在仪器记录之外的时间尺度上可获得的关于古气候估计的最佳信息。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project examines a sedimentary sequence from Lake Chalco (Central Mexico) to develop a ~50 kyr record of terrestrial climate variability in the North American tropics. The project uses proxies that reflect hydrological and thermal variability, focusing in particular on the transition from the Last Glacial Maximum to the Holocene. This project is in cooperation with the Autonomous University of Mexico who, in the first phase of a drilling program, recovered a ~100 m drill core. Subsequent drilling may extend this by 100 m, providing a record back to ~300 ka that includes the previous two interglacials. This pilot project focuses on the uppermost 50 m of the core recovered earlier. The analyses include x-ray fluorescence core scanning for major elemental composition at an average resolution of ~20 years through the 50 m section, as well as a series of organic geochemical analyses, including MBT (paleotemperature), biomarker del-D (aridity) and lignins and biomarker del-13C (vegetation response) at ~1000 year resolution since 50 ka. This work provides a 'proof of concept' for this site and a unique level of information on past temperatures and precipitation since mid-MIS 3 in a region where climate records are sparse. The climate record from Chalco should provide insights on regional responses to past changes in coupled climate systems. Recent work in Antarctic ice cores documents significant differences in atmospheric pCO2 and climate change over the Middle Pleistocene (EPICA 2005, Siegenthaler, 2005), but high-resolution continental records spanning this interval are rare globally and absent in North America. The full Chalco record has the potential to provide unique information that fills this critical gap, improving our understanding of our present interglacial and its future course.This project contributes to the training of the next generation of geoscientists through the direct support of graduate and undergraduate students. This study also fosters international collaboration among scientific communities in the U.S. and Mexico; Mexican students will come to the Large Lakes Observatory to work on this project.Broader impacts to the scientific community include a reconstruction of the climate history of central Mexico spanning the past 35 kyr, and a validation of the application of the MBT paleotemperature proxy in lacustrine systems of Mexico. Increasing temperatures predicted by modern global climate change will significantly impact natural systems as well as human populations in the coming century. Gaining a better understanding of climate system processes and how they are reflected in geochemical proxy records can help in modeling future climate trends. Appropriate application of rigorously investigated proxies provides the best information about paleoclimate estimates currently available on timescales beyond the existence of instrumental records.