Collaborative Research: Towards an understanding of the Holocene paleomagnetic record through new data (Hawaii/North American) and time series/spherical harmonic model comparisons

合作研究：通过新数据（夏威夷/北美）和时间序列/球谐模型比较来了解全新世古地磁记录

• 批准号: 1215661
• 负责人: Mark Abbott
• 金额: $ 24.66万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1215661&HistoricalAwards=false
• 关键词: Collaborative; Research; Towards; understanding; Holocene

Historical and recent paleomagnetic observations, along with geodynamo modeling studies highlight the importance of non-axisymmetric flux concentrations, not only as an indicator that the mantle has an important influence on the geodynamo, but also that it may act as a potential organizing structure that might control much of the dynamics of the geomagnetic field including paleomagnetic secular variation (PSV). Comparison of specific, well-dated Holocene PSV time series of inclination, declination, and paleointensity at key locations suggest the existence of a relatively simple first order pattern that is most clearly observed over the last four thousand years where the highest quality data are available. Over this time range, the field morphology can be roughly broken into two "modes": The first mode having a dominant flux lobe over North America and the second a dominant flux lobe over Europe. The "North American mode" is consistent with the historically time averaged field. The "European mode" is consistent with the time averaged mid-to-late Holocene field. A new inclination anomaly reconstruction for the NE Pacific region derived from Alaskan, and older Hawaiian and Oregon records, suggests that the influence of this oscillation may extend into the Pacific and continue through the Holocene and possibly beyond. The discovery of such an oscillation would be a significant step toward an understanding of what drives PSV. Unfortunately, available PSV data from North America and the northeast Pacific, because of uncertain chronologies and limited modern relative paleointensity records, are not adequate to fully assess whether the relationship observed persists over longer paleomagnetic time intervals. This three-year study will focus on the North American and northeast Pacific records to improve observational constraints and assess the relationship between data derived PSV time series and continuous spherical harmonic models to inform the interpretation of the PSV record. Data quality, including chronology is a limiting factor in our understanding of the geomagnetic causes of PSV. This will be improved through a synthesis of existing data and radiocarbon dates, and the collection of new cores from classic paleomagnetic sites and other nearby locations with proven sedimentary records, but where modern dating and paleomagnetic practices have yet to be employed.We study the paleomagnetic record for many reasons, with the most fundamental being to understand the past history of Earth's magnetic field. Paleo-geomagnetic observations from rocks, sediments, and archeological artifacts provide fundamental information about geomagnetic field generation process that cannot be obtained from the short historical record. These observations tell us that large amplitude geomagnetic changes in direction and intensity occur over timescales that range from decades to millions of years. Yet our knowledge of the processes and boundary conditions that govern paleo-geomagnetic change are far from complete resulting in significant uncertainty in our understanding of the geomagnetic field and any process controlled by geomagnetic change, from magnetic stratigraphy to space climate. This study is designed to determine if boundary conditions may act as a potential organizing structure that might control much of the dynamics of the geomagnetic field including millennial and centennial scale changes know as paleomagnetic secular variation (PSV). Results will help to differentiate between the contributions of geomagnetic and solar forcing of terrestrial cosmic ray flux and cosmogenic isotope production with practical implications for telecommunications, human health, global ecosystems and climate. The potential linkage between climate change and field morphology is a relatively new topic of research and one that deserves special attention at this time of rapid climate change. Holocene magnetic stratigraphy has a long history, but its usefulness is ultimately limited by how well we know the paleomagnetic record. An understanding of the geomagnetic cause of paleomagnetic change will provide significant new magnetic stratigraphic opportunities. This project will support undergraduate, graduate, and postdoctoral education, providing training in core collection, stratigraphy, paleomagnetic data analysis, environmental magnetic data analysis, geomagnetism, geochronology and paleoclimatology.

历史和最新的古磁观测以及地球模型建模研究突出了非轴对称通量浓度的重要性，不仅是指披风对地震具有重要的影响，还可能充当潜在的组织结构，可能会控制着包括古磁场的动力学，包括古sep sepliation（包括古磁场）。比较特定的，良好的全新世PSV时间序列的倾向，偏斜和在关键位置的古生度表明，存在相对简单的一阶模式，在过去的四千年中，最清楚地观察到了最高质量数据的最高质量数据。在这个时间范围内，田间形态可以大致分为两种“模式”：第一种模式在北美占据主导地位的磁瓣，第二种模式是欧洲占主导地位的通量隆。 “北美模式”与历史上平均的领域一致。 “欧洲模式”与平均中期全新世领地一致。源自阿拉斯加的NE太平洋地区以及夏威夷和俄勒冈州较旧的记录的新的倾斜度异常重建表明，这种振荡的影响可能会延伸到太平洋，并继续穿越全新世乃至超越。这种振荡的发现将是迈向理解驱动PSV的重要一步。不幸的是，由于年代的不确定和有限的现代相对古显微记录，来自北美和东北太平洋的可用PSV数据不足以充分评估在较长的古磁时间间隔内观察到的关系是否持续存在。这项为期三年的研究将重点介绍北美和东北太平洋记录，以改善观察性约束，并评估派生的PSV时间序列和连续球形谐波模型之间的关系，以告知PSV记录的解释。数据质量（包括年表）是我们对PSV的地磁原因理解的一个限制因素。通过综合现有数据和放射性碳日期的综合以及经典的古磁地点和其他附近的其他地方收集的新核心，这些新核心将通过经过验证的沉积记录来改善这一点。但是，在许多原因出于许多原因，我们在许多原因中研究了古磁性记录，这些纪录是最根本的，以了解最基本的领域，以了解地球上的磁性领域。岩石，沉积物和考古文物的古地球磁观测提供了有关地磁野外生成过程的基本信息，这些信息无法从短暂的历史记录中获得。这些观察结果告诉我们，在数十年到数百万年的时间尺度上，方向和强度的大量地磁变化发生。 然而，我们对控制古地球磁变化的过程和边界条件的了解远非完全，从而使我们对地磁场的理解以及从磁层到空间气候控制的地磁变化所控制的任何过程都有明显的不确定性。 这项研究旨在确定边界条件是否可以充当潜在的组织结构，该结构可能控制着千禧一代和百年尺度变化的地磁场的大部分动力学。结果将有助于区分地磁和太阳能对地面宇宙射线通量和宇宙同位素产生的贡献，对电信，人类健康，全球生态系统和气候的实际影响。气候变化与现场形态之间的潜在联系是一个相对较新的研究主题，在这个快速气候变化的时候值得特别关注。全新世磁地层具有悠久的历史，但其有用性最终受到我们了解古磁记录的程度的限制。对古磁变化的地磁原因的理解将为新的磁性地层机会提供大量的机会。该项目将支持本科生，研究生和博士后教育，在核心收集，地层，古磁数据分析，环境磁数据分析，地质磁学，地质磁学，地球人工学和古气候学方面提供培训。