Collaborative Research: Glacial Lake Ojibway Chronology to Test the 8,200 yr Cold-Event Trigger

我们对导致气候突变的事件的理解存在根本性的差距，即8,200年一遇的冷事件。假设的触发因素是融水突然进入高纬度地区，但只有为其他目的进行的初步研究提供了触发因素及其源区的证据。本项目的目的是确认或修改劳伦泰德融水排放事件和8,200年冷事件之间的阶段。长期目标是了解冰盖和气候变化之间相互作用的性质。一个核心假设是，冰川湖Ojibway中冰川大坝的崩溃是一个多步骤的过程，持续了几个世纪。这项工作的基本原理是，一个良好的约束年龄分配的冰川湖排水将允许更详细的建模实验或强制重新考虑的作用，融水不仅在这种气候变化，但也较早的事件，如新仙女木。有限的放射性碳年代的覆盖海洋贝壳目前只能提供一个年轻的支架上的排水年表。该湖相序列的直接和重复测年以及现代对比技术将把最终的排水事件（或事件）置于绝对时间中。最年轻的地层部分目前只在少数地方出现，描述各不相同。在一个单一的灾难性湖泊排水模型，这个序列不应该显示这种变化。通过生成新的合成韵律层序列并将其与现有序列进行比较，应该可以描述融水排出的性质。古地磁长期变化地层学，结合通过X射线荧光扫描产生的地球化学数据，将有助于评估韵律层和韵律层厚度相关性的年度性质。这项工作是原创的，因为它将把劳伦泰德冰盖的最后阶段的事件放入一个高分辨率的时间尺度。预期的产品是一个融水触发的8,200年的事件通过每年解决记录的测试，和一个关键的除了越来越多的时间限制，高分辨率记录冰退缩和晚冰期paleohydrologic.Broader影响：奥吉布韦湖纹是一个时间序列，连接发现和教学。数据序列通常用于指导气候变率、光谱分析和地质年代学等主题。这些特殊的记录有助于从入门到研究生水平的这些概念的教学。该奖项通过辛辛那提大学和Mercyhurst学院的本科生和研究生研究项目直接支持感兴趣的学生。在Mercyhurst学院，这些数据通过开发一个新的实验室项目来加强基础设施，该项目强调通过研究进行教学。这项工作有助于重新引入数据的效用，并为下一代冰川消退模型建立一个框架。这一贡献是重要的，因为它产生了一个新的年代框架，以了解劳伦泰德冰盖和淡水通量的作用，北大西洋的气候突变。结果将公布并提交给国家地球物理数据中心，以便随时向世界各地的专家提供。

There is a fundamental gap in our understanding of the events leading up to the abrupt climate change known as the 8,200 yr cold event. The assumed trigger is the sudden introduction of meltwater into high latitudes, yet only preliminary studies undertaken for other purposes have provided evidence for the trigger and its source area. The objective of this project is to confirm or revise the phasing between Laurentide meltwater drainage events and the 8,200 yr cold event. The long-term goal is to understand the nature of interactions between ice sheets and climate change. It is a central hypothesis is that the break-up of the glacier dam holding in glacial Lake Ojibway was a multi-stepped process operating over centuries. The rationale for this work is that a well-constrained age assignment for the glacial lake drainage will either allow for more detailed modeling experiments or force reconsideration of the role of meltwater in not only this climatic shift, but also earlier events such as the Younger Dryas. Limited radiocarbon dates on overlying marine shells currently provide only a younger bracket on the drainage chronology. Direct and replicated dating of this lacustrine sequence as well as modern correlation techniques will place the final drainage event (or events) into absolute time. The youngest portion of the stratigraphy is currently only represented in a few places, and descriptions vary. In the model of a single catastrophic lake drainage, this sequence should not display this variation. By generating new synthetic rhythmite sequences and comparing them to existing ones, it should be possible to describe the nature of meltwater expulsion. Paleomagnetic secular variation stratigraphy, combined with geochemical data generated via X-ray fluorescence scanning, will help to assess the annual nature of the rhythmites and rhythmite thickness correlations. This work is original because it will place the events of the final stages of the Laurentide Ice Sheet into a high resolution time scale. The expected product is a test of a meltwater trigger of the 8,200 year event via annually resolved records, and a critical addition to a growing body of temporally constrained, high resolution records of ice retreat and late-glacial paleohydrology.Broader Impacts: The Lake Ojibway varves are a time-series that connect discovery and teaching. Data sequences are commonly used to instruct topics such as climate variability, spectral analysis, and geochronology. These particular records aid teaching of these concepts from the introductory to graduate level. This award directly supports interested students via undergraduate and graduate research projects at both the University of Cincinnati and Mercyhurst College. At Mercyhurst College, these data enhance infrastructure via the development of a new laboratory program emphasizing teaching through research. This work helps reintroduce the data's utility and establish a framework for the next generation of deglaciation models. This contribution is significant because it generates a new chronological framework to understand the roles of the Laurentide Ice Sheet and of freshwater flux to the North Atlantic in abrupt climate change. Results will be published and submitted to the National Geophysical Data Center, so that they will be readily available to experts worldwide.