Transforming our understanding of the geodynamo: A new global synthesis and model of millennial-scale geomagnetic variability for late Pleistocene

改变我们对地球发电机的理解：晚更新世千年尺度地磁变化的新全球综合和模型

• 批准号: NE/R011281/1
• 负责人: Chuang Xuan
• 金额: $ 44.62万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FR011281%2F1
• 关键词: Transforming; our; understanding; geodynamo; new

Earth's magnetic field is essential to life on our planet and to electronic communication technologies upon which modern society depends because it provides protection from harmful cosmic rays and the solar wind that bombard the upper atmosphere. But this invisible protective field is far from constant. Its intensity and direction are always changing both temporally and spatially. On decadal timescales and longer these changes can be attributed to the interaction between Earth's rotation about its axis and convective motion in its molten interior- its geodynamo. Yet our understanding of the geodynamo and the mechanisms by which it drives changes in our magnetic field is primitive. The main problem preventing progress is a lack of a robust data set recording past changes in magnetic field that extends back in time beyond the start of the Holocene geological epoch (~10,000 years ago, ka). For the Holocene, we have a relatively well dated compilation of records, largely from archaeological and lake archives, showing changes in magnetic intensity and direction from a network of sites around the world. This allows us to develop computer models of global magnetic field variability through time, providing a way to transform our understanding of the geodynamo. But we must look beyond the Holocene because we need a longer perspective to study a fuller range of field variability. Earth's magnetic field has lost half its strength since Roman times but much larger changes in intensity occurred during the geological epoch that preceded the Holocene (the Pleistocene). Furthermore, there has not been an undisputed full (180 deg.) change in magnetic field direction or polarity excursion for ~40 kyrs and that event is just one of at least five well-documented excursions that took place during the last ~500 kyrs. We propose to transform our understanding of the geodynamo and the cause of changes in Earth's magnetic field by turning to this Late Pleistocene record of changes in field intensity and direction. Marine sediment drillcores are well-suited to providing the long undisturbed records needed for this purpose but, until now, it has not been possible to date them sufficiently robustly to work globally at the resolution needed. We will: (1) Build a new benchmark record of geomagnetic change for the last ~500 thousand years (kyr) using a suite of exceptional sediment archives recently drilled on the west Iberian Margin. (2) Undertake a comprehensive synthesis of existing high-resolution sedimentary palaeomagnetic records around the globe. (3) Take advantage of the unique chronological constraints of the Iberian Margin sediments, to precisely date the Exp. 339 records at the millennial scale. We will then export that chronology to the synthesized records using geochemical/physical property data sets available to develop a precisely dated global compilation of changes in magnetic field intensity and direction for the last ~500 kyr. This correlation method ensures that we make no assumption about synchronicity of palaeomagnetic change between sites (so that this issue can be studied). (4) Use these new high-resolution and well-dated datasets in collaboration with a leading geomagnetic field modeler to build the first computer models to reconstruct changes in Earth's geomagnetic field through time and space over the last few hundred kyr to overhaul our understanding of the dynamics and causes of geomagnetic variability.

地球磁场对我们星球上的生命和现代社会所依赖的电子通信技术至关重要，因为它提供了保护，使其免受有害的宇宙射线和轰击高层大气的太阳风的影响。但这种无形的保护场远非恒定不变。它的强度和方向总是在时间和空间上变化。在十年或更长的时间尺度上，这些变化可以归因于地球绕轴旋转和其熔融内部对流运动（地球发电机）之间的相互作用。然而，我们对地球发电机及其驱动磁场变化的机制的理解还很原始。阻碍进展的主要问题是缺乏一个强大的数据集来记录过去磁场的变化，这些变化可以追溯到全新世地质时代（约10，000年前，ka）的开始。对于全新世，我们有一个相对较好的记录汇编，主要来自考古和湖泊档案，显示了世界各地遗址网络的磁场强度和方向的变化。这使我们能够开发出全球磁场随时间变化的计算机模型，为改变我们对地球发电机的理解提供了一种方法。但我们必须超越全新世，因为我们需要一个更长远的视角来研究更全面的场变。自罗马时代以来，地球的磁场强度已经下降了一半，但在全新世（更新世）之前的地质时代，强度发生了更大的变化。此外，还没有一个完整的（180度）。磁场方向或极性偏移的变化约为40 kyr，该事件只是过去约500 kyr期间发生的至少五次有据可查的偏移之一。我们建议通过研究晚更新世的磁场强度和方向的变化记录来改变我们对地球发电机和地球磁场变化原因的理解。海洋沉积物岩心非常适合提供这一目的所需的长期未受干扰的记录，但到目前为止，还不可能以所需的分辨率对它们进行充分可靠的日期确定。我们将：（1）利用最近在西伊比利亚边缘钻探的一套特殊沉积物档案，建立一个新的基准记录，记录过去50万年（kyr）的地磁变化。(2)全面综合地球仪周围现有的高分辨率沉积古地磁记录。(3)利用伊比利亚边缘沉积物独特的年代学限制，精确测定Exp. 339个千年记录。然后，我们将使用可用的地球化学/物理性质数据集将该年代表导出到合成记录中，以制定过去~500 kyr磁场强度和方向变化的精确日期全球汇编。这种相关方法确保了我们不对地点之间的古地磁变化的同步性做出任何假设（因此可以研究这个问题）。(4)使用这些新的高分辨率和良好的数据集与领先的地磁场建模师合作，建立第一个计算机模型，以重建过去几百年来地球地磁场在时间和空间上的变化，以彻底改变我们对地磁变化的动力学和原因的理解。

项目成果

Sensor Response Estimate and Cross Calibration of Paleomagnetic Measurements on Pass‐Through Superconducting Rock Magnetometers

穿过式超导岩石磁强计古地磁测量的传感器响应估计和交叉校准

• DOI: 10.1029/2019gc008597
• 发表时间: 2019
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Xuan Chuang;Oda Hirokuni
• 通讯作者: Oda Hirokuni

Integrated Pliocene-Pleistocene magnetostratigraphy and tephrostratigraphy of deep-sea sediments at IODP Site U1424 (Yamato Basin, Japan Sea)

• DOI: 10.1186/s40645-020-00373-9
• 发表时间: 2020-10
• 期刊: Progress in Earth and Planetary Science
• 影响因子: 3.9
• 作者: C. Xuan;Yuxi Jin;S. Sugisaki;Y. Satoguchi;Y. Nagahashi

Multi-Proxy Investigations into Mediterranean Outflow Water Variability and Sedimentary Processes on the West Iberian Margin Through the Late Pleistocene

晚更新世地中海流出水量变化和西伊比利亚边缘沉积过程的多代理研究

• 发表时间: 2021
• 作者: Nichols, M

Additional file 1 of Integrated Pliocene-Pleistocene magnetostratigraphy and tephrostratigraphy of deep-sea sediments at IODP Site U1424 (Yamato Basin, Japan Sea)

IODP站点U1424（日本海大和盆地）深海沉积物综合上新世-更新世磁性地层学和热地层学附加文件1

• DOI: 10.6084/m9.figshare.13064332
• 发表时间: 2020
• 作者: Xuan C

Global and regional geomagnetic variabilities recorded in late Quaternary sediments from the west Iberian Margin

西伊比利亚边缘晚第四纪沉积物记录的全球和区域地磁变化

• DOI: 10.5194/egusphere-egu2020-11984
• 发表时间: 2020
• 作者: Xuan C