Developing a high-resolution Holocene paleo-geomagnetic reconstruction from northern North Atlantic sediments to place the historical geomagnetic field in perspective

从北大西洋北部沉积物中进行高分辨率全新世古地磁重建，以透视历史地磁场

基本信息

批准号：
1645411
负责人：
Joseph Stoner
金额：
$ 25万
依托单位：
Oregon State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1645411&HistoricalAwards=false
关键词：
Developing resolution Holocene paleo geomagnetic

项目摘要

In contrast with the geomagnetic field during historical times, the geomagnetic field during prehistoric (paleo) times is poorly described. As a result it is difficult to know the context in which to place the historical record of the geomagnetic field including features that have changed and those that have persisted. Some researchers have considered historical times to be anomalous, but if so, how anomalous? Should we be concerned about what future changes may bring or are historical behaviors that have gained attention just part of normal background variability. With better data and data analysis approaches our understanding of the prehistoric (paleo)-geomagnetic field has improved substantially over the last decade. Scientists are beginning to define paleo-geomagnetic dynamics that happen on thousands of years. But we do not know how these changes relate to historical type variations or whether the rates of change of the geomagnetic field are consistent or uneven. This project will address this through a reconstruction of the paleo-geomagnetic record of the northern North Atlantic from ultrahigh accumulating sediments that allow paleo-geomagnetic records to be developed at sub-centennial resolution through the last 10,000 years. The northern North Atlantic is an optimal location because it is a region of extreme geomagnetic sensitivity and one where high quality paleo records with little smoothing can be obtained. The latter is important as most sedimentary records smooth over historically relevant time intervals providing little context. The investigators will scrutinize present records in detail and combine them with new ultrahigh resolution records to provide high quality records with well-constrained uncertainties. This will provide fundamental observations on paleo-geomagnetic changes from a strategic location and of a quality where the interactions between millennial and shorter changes can be evaluated, and as a result, allow the investigators to place modern changes into firmer prehistoric constraints. Additionally, this project will provide an interpretive framework to more completely understand the processes deep within Earth that drive the geomagnetic field and how the geomagnetic shield that protects us from cosmic rays and solar winds varies through time and is likely to do so again; with practical implications for telecommunications, human health, and global ecosystems. Regional stratigraphic master dating curves will be refined. This project will support postdoctoral education continuing an investment in those that we have trained to make sure our initial investment does not fail. Data will be contributed to national databases and used to supplement ongoing big data studies of the geomagnetic field with well-characterized data. Exhibits and presentations on the theme What mud can tell us about Earth's magnetic field will be developed in collaboration with the OSU Marine Geology Repository and delivered to K-12, undergraduate, and adult learner through tours and classes and through the CEOAS booth at the Corvallis Saturday Market.The geomagnetic field is changing; the question is what sort of change is taking place. Some have speculated that a polarity reversal is imminent; others have suggested that such a change, if happening at all, is thousands of years away at the soonest. Much of the ambiguity results from a lack of paleo-context from which to place the historical geomagnetic field. Even though the paleo-record is poorly constrained relative to historical, our understanding of this record is improving and suggests that we are undergoing the latest of a series of millennial scale changes of the field that describe the Holocene, but what happens on shorter timescale analogous to the historical record is essentially unknown. The change that is happening at present is just one example, but whether this is large or small or unique or normal is not known. This project will provide observational constraints on paleo-geomagnetic change from a strategic location and of a quality where the interactions between millennial/centennial and geomagnetic changes on shorter time scales can be evaluated. As a result these observations will provide a paleo-context from which to evaluate historical geomagnetic change. To do this the team will use records from the northern North Atlantic, a location of fundamental paleomagnetic importance for three essential reasons. First, the structure of the modern geomagnetic field, changes observed historically, and paleomagnetic records all point to the northern North Atlantic as a region sensitive to changes in the geomagnetic field's morphology. Second, aggressive glacial erosion of strongly magnetic bedrock, along with a vigorous redistribution system results in paleomagnetic record of high fidelity often accumulating at high rates in both marine and terrestrial (lake) settings. Third, high carbonate production and preservation in marine environments allow for detailed radiocarbon chronologies, while numerous tephra layers enable reservoir ages to be assessed resulting in well constrained chronologies. Exceptional paleo-geomagnetic records that result are capable of uncovering many aspect of the geomagnetic field with unprecedented accuracy and resolution through the Holocene. The present set of records are enlightening; unveiling features never before seen, but are far from perfect, with notable gaps over the last few thousand years, occasional discrepancies between overlapping records (especially with relative paleointensity), and have not been adequately synthesized. Significant improvements are still possible, as concerted efforts to constrain the regions paleoclimatic record have resulted in a large number of sediment cores on and around Iceland/Greenland that retain suitable properties for high fidelity paleomagnetic records. Many of these records have already been dated and some have associated paleomagnetic data (often incompletely assessed) already in place. The investigators will take advantage of these sediment archives and data to support development of a sub-centennial resolution paleo-geomagnetic reconstructions from the northern North Atlantic that overlaps with the historical record and continues through the Holocene with enough observations to constrain and reduce uncertainties in both chronology and paleomagnetic measurables. This paleo-geomagnetic synthesis will provide an interpretive framework to more completely assess past variations required to further our understanding of the geodynamo process controlling the geomagnetic field and the geomagnetic shield and its control on the production of cosmic nuclides; a hinge point for our understanding of processes ranging from solar variability to climate with practical implications for telecommunications, human health, and global ecosystems. Regional stratigraphic master dating curves will be refined. Data will be contributed to national databases (MagIC, NOAA ) providing well constrained data for ongoing spherical harmonic analyses of the geomagnetic field. Exhibits and presentations on the theme "What mud can tell us about Earth's magnetic field" will be developed in collaboration with the OSU Marine Geology Repository and delivered to K-12, undergraduate, and adult learner through tours and classes and through the CEOAS booth at the Corvallis Saturday Market.

与历史时期的地磁领域相比，史前（古）时代期间的地磁领域的描述很差。结果，很难知道在地磁领域的历史记录中，包括已改变的特征和持续存在的背景。一些研究人员认为历史时代是异常的，但是如果是的，那是异常的吗？如果我们担心未来的变化可能会带来什么或是历史行为，而历史行为仅仅是正常背景变异性的一部分。通过更好的数据和数据分析方法，我们对史前（古）地球磁场的理解在过去十年中有了显着改善。科学家开始定义数千年来发生的古磁动力学。但是，我们不知道这些变化与历史类型的变化有何关系，或者是地磁场的变化率是一致的还是不均匀的。该项目将通过重建北大西洋北部北大西洋的古地球磁记录来解决这一问题，从超高积聚的沉积物中，允许在过去10，000年之前以次世纪的分辨率开发古地球磁性记录。北大西洋北部是一个最佳位置，因为它是一个极端的地磁敏感性的区域，并且在其中很少获得平滑的高质量古记录。后者很重要，因为大多数沉积记录在历史上相关的时间间隔内平稳，几乎没有背景。调查人员将详细审查当前记录，并将其与新的超高分辨率记录相结合，以提供具有良好受限不确定性的高质量记录。这将提供对古地球磁性变化的基本观察，从战略位置以及可以评估千禧一代和较短变化之间的相互作用的质量，因此，使研究人员可以将现代变化置于更牢固的史前约束中。此外，该项目将提供一个解释性框架，以更完全理解地球内部深处的过程，这些过程驱动着地磁场，以及如何保护我们免受宇宙射线和太阳风的侵害的地磁盾如何随着时间的流逝而变化，并可能再次这样做；对电信，人类健康和全球生态系统的实际影响。区域地层大师约会曲线将进行完善。该项目将支持博士后教育继续对我们已经培训的人进行投资，以确保我们的初始投资不会失败。数据将介绍国家数据库，并用来补充具有良好特征数据的地磁领域的正在进行的大数据研究。关于Mud可以告诉我们有关地球磁场的展览和演示将与OSU Marine Geology存储库合作开发，并通过旅游和课程以及Corvallis Saturday Market的Ceoas Booth交付给K-12，本科生和成人学习者。地质磁场正在发生变化；问题是发生了什么样的变化。有些人推测极性逆转即将到来。其他人建议，这种变化（如果发生的话）在最快的时间内将有数千年的历史。大部分歧义是由于缺乏古代文化而置于历史地磁领域的原因。尽管相对于历史而言，古记录的限制很差，但我们对这一记录的理解正在改善，并表明我们正在经历描述全新世的一系列千禧年尺度变化的最新变化，但是与历史记录相似的较短时间表上发生的情况本质上是未知的。目前正在发生的变化只是一个例子，但是无论是大还是小还是唯一的还是正常的。该项目将对从战略位置和质量上的古地球磁性变化以及千禧一代/百年纪念和地磁变化之间的相互作用在较短时间尺度上进行评估的质量提供观察性约束。结果，这些观察结果将提供一种古文本，从中可以评估历史地磁变化。为此，团队将使用北大西洋北部的记录，这是一个基本古磁重要性的位置，出于三个基本原因。首先，现代地磁领域的结构在历史上观察到了变化，并且古磁记录都指向北大西洋北部，是对地磁领域的形态变化敏感的地区。其次，强烈磁性基岩的侵略性冰川侵蚀，以及剧烈的重新分布系统，导致海洋和陆地（Lake）设置中的高富达的古磁记录通常以高速度积累。第三，海洋环境中的碳酸盐产生和保存范围允许详细的放射性碳年代学，而许多tephra层可以评估储层年龄，从而产生良好的时间表。结果的特殊古地球磁记录能够通过全新世以前的准确性和分辨率来揭示地磁场的许多方面。目前的记录集很有启发性；揭幕特征从未见过，但远非完美，在过去的几千年中存在显着差距，偶尔在重叠的记录（尤其是相对苍白的大压）之间存在差异，并且没有充分合成。仍然可以进行重大改进，因为限制古气候记录的一致努力导致冰岛/格陵兰岛及其周围的大量沉积物核心保留了适当的特性，以实现高保真性古磁性记录。这些记录中有许多已经过时了，有些记录已经相关的古磁数据（通常不完全评估）已经到位。调查人员将利用这些沉积物档案和数据来支持从北大西洋北部北部大西洋的古磁性重建的开发，这些重建与历史记录重叠，并通过全新世继续进行，并以足够的观察结果来限制和减少年代学和古磁性测量值的不确定性。这种古地球磁合成将提供一个解释性框架，以更完全评估我们对控制地磁场和地磁盾的地球过程的理解所需的过去变化，及其对宇宙核素产生的控制；我们了解从太阳可变性到气候的过程，对电信，人类健康和全球生态系统的实际意义不等。区域地层大师约会曲线将进行完善。数据将介绍国家数据库（Magic，NOAA），为持续的球形磁场的球形谐波分析提供了良好的数据。关于“ Mud可以告诉我们有关地球磁场的内容”的展览和演示将与OSU Marine Geology存储库合作开发，并通过旅游和课程以及Cooas Booth在Corvallis Corvallis Saturday Market上交付给K-12，本科生和成人学习者。