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

历史和最近的古地磁观测以及地球发电机模型研究突出了非轴对称通量集中的重要性，它不仅是地幔对地球发电机有重要影响的指标，而且可能作为一种潜在的组织结构，可能控制包括古地磁长期变化(PSV)在内的地磁场的大部分动力学。对关键地点特定的、年代准确的全新世PSV倾角、偏角和古强度时间序列的比较表明，存在一个相对简单的一级模式，在过去4000年中可以最清楚地观察到，在那里可以获得最高质量的数据。在这个时间范围内，场的形态大致可以分为两个“模”：第一个模在北美上空占主导地位，第二个模在欧洲上空占主导地位。“北美模式”与历史时间平均场是一致的。“欧洲模式”与全新世中晚期的时间平均场相一致。来自阿拉斯加的东北太平洋地区的一个新的倾角异常重建，以及夏威夷和俄勒冈州更早的记录，表明这种振荡的影响可能延伸到太平洋，并持续到全新世甚至更远。这种振荡的发现将是朝着理解PSV驱动因素迈出的重要一步。不幸的是，来自北美和东北太平洋的现有PSV数据，由于不确定的年代学和有限的现代相对古强度记录，不足以充分评估所观察到的关系是否在更长的古地磁时间间隔内持续。这项为期三年的研究将侧重于北美和东北太平洋的记录，以改善观测限制，并评估从PSV时间序列得出的数据与连续球面调和模型之间的关系，以便为PSV记录的解释提供信息。数据质量，包括年表，是我们理解PSV的地磁原因的一个限制因素。这将通过综合现有的数据和放射性碳测年，以及从经典的古地磁遗址和其他附近地点收集新的岩芯来改善这一点，这些地点有证明的沉积记录，但尚未采用现代测年和古地磁实践。我们研究古地磁记录的原因有很多，最根本的是了解地球磁场的过去历史。来自岩石、沉积物和考古文物的古地磁观测提供了有关地磁场产生过程的基本信息，这些信息是从短暂的历史记录中无法获得的。这些观测告诉我们，地磁在方向和强度上的大幅度变化发生在几十年到数百万年的时间尺度上。然而，我们对控制古地磁变化的过程和边界条件的了解还远远不完整，导致我们对地磁场以及从磁性地层学到空间气候的任何受地磁变化控制的过程的理解存在很大的不确定性。这项研究旨在确定边界条件是否可能作为一种潜在的组织结构，可能控制地磁场的大部分动态，包括被称为古地磁长期变化(PSV)的千年和百年尺度变化。这些结果将有助于区分地磁和太阳强迫对地球宇宙射线通量和宇宙成因同位素生产的贡献，对电信、人类健康、全球生态系统和气候具有实际意义。气候变化和田间地貌之间的潜在联系是一个相对较新的研究课题，在气候快速变化的时候值得特别关注。全新世磁性地层学有很长的历史，但其用途最终受到我们对古地磁记录的了解程度的限制。了解古地磁变化的地磁原因将提供重大的新的磁性地层学机会。该项目将支持本科生、研究生和博士后教育，提供岩心采集、地层学、古地磁数据分析、环境磁数据分析、地磁学、地质年代学和古气候学方面的培训。

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.