MexiDrill: The Basin of Mexico Drilling Program

摘要了解过去导致全球气候快速变化的机制是古气候研究的关键问题，也是评估当前和未来气候变化影响的关键。特别是，热带在气候变化中的作用仍然知之甚少。这笔赠款将为明尼苏达大学德卢斯分校和双城分校提供资金，用于从墨西哥城南郊的Chalco湖回收钻芯。这些湖泊沉积物有可能提供50万年的北美气候记录。Chalco湖的核心与地球上人口最密集的城市中心之一墨西哥城直接相关，墨西哥城拥有约2000万人口。该项目计划在墨西哥（博物馆和移动教室）和明尼苏达州（“Flyover Country”移动应用程序）现有项目的基础上，提高公众的科学素养和参与度，并为当地K-12教师组织研讨会。包括一项评估更广泛影响的有力计划。该项目将通过将学生和博士后研究人员纳入钻探项目，为培养下一代地球科学家做出贡献。该项目将促进美国、欧洲和墨西哥科学界在Chalco盆地钻探和持续科学调查期间的联系。虽然该提案的重点是恢复环境记录，但其他小组对利用核心或钻孔进行一系列研究感兴趣，包括火山历史和危害，地震监测和地震危害建模，以及水文监测和教学工具。目前的赠款中没有为这些相关项目提供资金。本项目资助从墨西哥盆地墨西哥城南郊的Chalco湖盆地350米湖相沉积序列中回收钻芯。这些沉积物有可能提供50万年的北美气候记录。这将是一个独特的气候档案，可以发展成为北美古气候研究的“类型序列”。Chalco非常适合于重建和研究北美季风（NAM）的年际变化和新热带地区的水文变化。正在进行的工作表明，该系统记录了环境对米兰科维奇尺度和千年尺度气候强迫的响应。为了评估低纬度在引发和传播全球气候突变方面的相对作用，仍然需要有关热带突变的地理分布、模式和时间的信息，特别是有助于确定热带辐合带（ITCZ）变率性质的记录。Chalco盆地的降水是由ITCZ的位置和NAM的强度决定的。日晒后ITCZ位置的长期（轨道）变化。然而，全新世古气候记录显示，由于海洋强迫（如大西洋经向翻转，AMO和太平洋年代际涛动，PDO）的影响，不干运动热带核心和其北缘之间的降水强度呈反相模式。Chalco盆地的记录可以与北部和南部已有的长期记录进行比较，以确定这种与AMO和PDO强迫的反相关系是否存在于早期间冰期。

Non-Technical AbstractUnderstanding mechanisms that caused rapid global climate changes in the past is a key problem in paleoclimate research, and is critical for evaluating impacts of ongoing and future climate change. In particular, the role of the tropics in climate shifts remains poorly understood. This grant will provide funding to the University of Minnesota at two campuses: Duluth and Twin Cities, in order to recover a drill core from Lake Chalco, on the southern outskirts of Mexico City. These lake sediments have the potential to provide a half-million year record of North American climate. The core from Lake Chalco is directly relevant to one of the most densely populated urban centers on our planet, Mexico City, home to ~20 million people. The project includes plans to increase public scientific literacy and engagement, building on existing programs in Mexico (museums and mobile classrooms) and Minnesota ("Flyover Country" mobile app), and to organize workshops for local K-12 teachers. A robust plan for evaluation of Broader Impacts is included. This project will contribute to the training of the next generation of geoscientists through the inclusion of students and postdoctoral researchers in the drilling project. This project will foster ties among scientific communities in the U.S., Europe and Mexico, both during drilling and continuing scientific investigations of the Chalco Basin. While the focus of this proposal is recovery of an environmental record, other groups have interest in utilizing the core or the boreholes for a range of studies including volcanic history and hazards, seismic monitoring and earthquake hazard modeling, as well as hydrological monitoring and teaching tools. No funding is provided for these related projects in the current grant.Technical AbstractThis grant provides funding to recover a drill core from a 350m lacustrine sedimentary sequence contained in the Lake Chalco basin on the southern outskirts of Mexico City in the Basin of Mexico. These sediments have the potential to provide a 500,000 year record of North American climate. This will be a unique climate archive that could develop into the "type sequence" for paleoclimate studies in North America. Chalco is well suited for reconstruction and investigatation of interannual through orbital-scale variations in the North American Monsoon (NAM) and hydrologic variations of the neotropics. Ongoing work indicates that the system records environmental responses to both Milankovitch- and millennial-scale climate forcing. In order to evaluate the relative role of low latitudes in initiating and propagating abrupt global climate changes, information regarding the geographical distribution, patterns and timing of abrupt changes in the tropics is still needed, particularly records to help define the nature of variability in the Intertropical Convergence Zone (ITCZ). Precipitation over the Chalco Basin is determined by the position of the ITCZ and the strength of the NAM. Long-term (orbital) variations in the position of the ITCZ follow insolation. However, Holocene paleoclimatic records show an antiphase pattern in precipitation intensity between the tropical core of the NAM and its northern margins in response to ocean forcing (e.g. Atlantic Meridional Overturn, AMO, and Pacific Decadal Oscillation, PDO). A record from the Chalco basin can be compared with existing long term records to the North and to the South to determine if this antiphase relationship to AMO and PDO forcing existed in earlier interglacials.