Estimating the Character of Paleomagnetic Field Excursions and Surrounding Secular Variation at Equatorial Latitudes (Equatorial W. Atlantic; MIS 1-4)

估计赤道纬度古磁场偏移和周围长期变化的特征（赤道西大西洋；MIS 1-4）

• 批准号: 1547605
• 负责人: Steven Lund
• 金额: $ 22.69万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1547605&HistoricalAwards=false
• 关键词: Estimating; Character; Paleomagnetic; Field; Excursions

Geomagnetic field excursions (e.g., Laschamp Excursion, Blake Event) are intervals of very anomalous magnetic field variability located within one region of the Earth's surface that last for less than a few thousand years. There have been, perhaps, 15 excursions since the last global magnetic field reversal ~780,000 years ago. Excursions must be due to some intermittent and anomalous behavior in the magnetic dynamo situated deep in the Earth's outer core, which generates the Earth's magnetic field. However, we have very little evidence of the pattern of individual excursions in several global regions far apart from one another that would test ideas of dynamo source(s) for excursions. We have no evidence for the relationship of excursions to surrounding normal magnetic field secular variation beyond individual records at isolated localities. Scientists still wonder whether excursions might be aborted global magnetic field reversals - or not. This grant would add significantly to our understanding of what individual excursions really look like around the world and how they relate to normal secular variation. Both of these are key concepts in building more realistic models of dynamo causes of excursions. The regional environmental magnetic correlations and paleomagnetic chronostratigraphic framework that the PI team will develop within the Equatorial Atlantic study region, will also provide significant insight into the space/time pattern of equatorial paleoclimate variability, of keen interest to global climate change policy.This grant will carry out a paleomagnetic study of excursions and surrounding normal secular variation recorded in deep-sea sediments of the Equatorial West Atlantic Ocean over the last glacial cycle (0-71 ka, MIS 1-4). This time interval contains the Mono Lake Excursion (~34 ka, Ex. 3a), the Laschamp Excursion (~41 ka, Ex. 3b) and the Greenland/Norwegian Sea Excursion (~61 ka, Ex. 4a). There are almost no published records of excursions at equatorial latitudes or of excursion records with reproducible secular variation surrounding them. This study also will develop, for the first time, a transect of excursion records and surrounding normal secular variation that extends from ~40°S to ~40°N along a single longitude swath (290°±20°). This transect will provide the first evidence of the detailed space/time pattern of excursions and their relationship to surrounding normal secular variation ever developed over a large, almost hemispheric, region of the Earth.

地磁场漂移(例如，拉尚漂移、布莱克事件)是位于地球表面一个区域内持续不到几千年的非常异常的磁场变化间隔。自78万年前的上一次全球磁场反转以来，可能已经发生了15次漂移。漂移一定是由于位于地球外核深处的磁发电机的某些间歇和异常行为造成的，它产生了地球的磁场。然而，我们几乎没有证据表明，在几个相距遥远的全球地区进行个人短途旅行的模式，这将检验发电机来源(S)进行短途旅行的想法。除了孤立地点的个别记录外，我们没有证据表明漂移与周围正常磁场的长期变化之间的关系。科学家们仍然在想，全球磁场逆转是否会导致短途旅行流产。这笔赠款将大大增加我们对世界各地个人短途旅行的真实情况以及它们与正常的长期变化的关系的了解。这两个概念都是建立更现实的发电机短途旅行原因模型的关键概念。PI小组将在赤道大西洋研究区内建立的区域环境磁对比和古地磁年代地层框架，也将对赤道古气候变异性的时空模式提供重要的洞察，这对全球气候变化政策非常感兴趣。这笔赠款将对上一次冰川周期(0-71ka，MIS1-4)赤道西大西洋深海沉积物中记录的漂移和周围正常的长期变化进行古地磁研究。该时间间隔包含莫诺湖漂移(~34ka，Ex.3A)，拉尚之旅(~41ka，Ex.3b)和格陵兰/挪威海之旅(约61ka，Ex.4A)。几乎没有关于赤道纬度漂移的公开记录，也没有关于其周围有可重复的长期变化的漂移记录。这项研究还将首次建立沿单一经度条带(2 90°±20°)从~40°S到~40°N的漂移记录和周围正常长期变化的样带。这一断面将首次提供详细的漂移空间/时间模式的证据，以及它们与地球上一大片近乎半球的区域所形成的正常的长期变化的关系。