Filling Holes in the Holocene Geomagnetic Field - Tropical East Africa

填补全新世地磁场的空洞 - 热带东非

• 批准号: 1316507
• 负责人: Steven Lund
• 金额: $ 20万
• 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: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1316507&HistoricalAwards=false
• 关键词: Filling; Holes; Holocene; Geomagnetic; Field

This proposal will carry out Holocene paleomagnetic field secular variation (PSV) studies on five lakes from Tropical East Africa (Turkana, Malawi, Tanganyika, Edward, Victoria). We will recover PSV records from at least two sediment cores in each lake and develop a composite PSV directional record from them. We will correlate the directional PSV records from all five lakes and date the records with C14 dating. We will also attempt to reconstruct relative paleointensity variability from each lake. Our preliminary data suggest we can do this for at least one lake, Malawi. This work will permit us to develop a regional group of PSV time series that will characterize field variability in a region where almost nothing is known in high-resolution. A high-resolution relative paleointensity record from Lake Malawi (10°S) would be the first such Holocene record from the Southern Hemisphere. The study will analyze these records and compare them with other global Holocene PSV data to assess geodynamo dynamics. USC researchers have developed a new model of Holocene field variability (PSVMOD2.0), based on a family of Global PSV time series for the last 8000 years. PSVMOD2.0 now has 85 sites around the World, which yield 72 directional PSV time series and 35 paleointensity time series. However, PSVMOD2.0 has no significant data from the African continent and no paleointensity time series from the Southern Hemisphere. This study of African lakes will add significantly to the quality of PSVMOD2.0. The African PSV data will also be used to better assess the timing and regional pattern of Holocene climate change in the studied lakes. PSV has previously been used very effectively as a high-resolution correlation and dating tool in paleoclimate studies. PSVMOD2.0 should become a community database used by a variety of scientists to better understand PSV and geodynamo dynamics. We still do not understand very well how our planetary magnetic field works (and largely the way all planetary magnetic fields and stellar magnetic fields work) under normal conditions. We know that these magnetic fields are generated by flow of electrically conducting fluid below the planetary/stellar surfaces (dynamo action), but current models of these processes (dynamo models) do not adequately describe how these fields really operate (particularly the Earth's magnetic field and our Sun's magnetic field). We need a more complete understanding of how our magnetic field operates under normal conditions to better constrain future dynamo models. The best (and only) way to do that is to reconstruct how our field has varied over the last several thousand years. (Dating errors make this analysis difficult to impossible in older times.) We currently have measured variations in Earth's magnetic field over the last few thousand years over less than half the Earth's surface. This project fills in a big hole in our understanding the central African continent. Better understanding of how the Earth's magnetic field operates normally (last few thousand years) will also give us a better way to assess what the Earth's magnetic field is doing when it 'goes screwy'. These periods are called magnetic field excursions and reversals.

该提案将对来自热带东非（Turkana，Malawi，Malawi，Tanganyika，Edward，Victoria）的五个湖泊进行全新世古磁场世俗变异（PSV）研究。我们将从每个湖泊中的至少两个沉积物核心恢复PSV记录，并从中产生复合PSV定向记录。我们将将所有五个湖泊的定向PSV记录与C14约会的记录相关联。我们还将尝试重建每个湖泊的相对古显度变异性。我们的初步数据表明，我们可以至少在马拉维湖上这样做。这项工作将使我们能够开发一个PSV时间序列的区域群体，该序列将在高分辨率中几乎没有任何知名度的区域中表征现场变异性。来自马拉维湖（10°S）的高分辨率相对古显着记录将是南半球的第一个这样的全新世记录。该研究将分析这些记录，并将它们与其他全球全新世PSV数据进行比较，以评估Geodynamo动力学。在过去的8000年中，USC研究人员基于全球PSV时间序列的家庭开发了一种全新世田可变性（PSVMOD2.0）的新模型。 PSVMOD2.0现在在世界各地拥有85个站点，该站点产生了72个定向PSV时间序列和35个Papetrentize Time序列。但是，PSVMOD2.0没有来自非洲大陆的显着数据，南半球没有古老的时间序列。这项对非洲湖泊的研究将大大增加PSVMOD2.0的质量。非洲PSV数据还将用于更好地评估工作室湖泊全新世气候变化的时机和区域模式。 PSV先前已被非常有效地用作古气候研究中的高分辨率相关性和约会工具。 PSVMOD2.0应该成为许多科学家使用的社区数据库，以更好地了解PSV和Geodynamo动力学。我们仍然不太了解我们的行星磁场在正常条件下如何工作（主要是所有行星磁场和恒星磁场的工作方式）。我们知道，这些磁场是通过在行星/恒星表面（Dynamo Action）下方电动传导流体流动而产生的，但是这些过程的当前模型（Dynamo模型）并不能充分描述这些磁场如何真正运行（部分是地球的磁场和我们的太阳磁场）。我们需要对磁场在正常条件下如何运行的方式有更完整的了解，以更好地限制未来的发电机模型。最好的方法（也是唯一）的方法是重建过去几千年来我们的领域的变化。 （约会误差使得在较旧时难以实现这种分析。）目前，在过去几千年中，在地球表面的一半中，我们已经测量了地球磁场的变化。该项目填补了我们理解中非大陆的一个大漏洞。更好地了解地球磁场的正常运行方式（最近几千年）也将为我们提供更好的方法来评估地球磁场在“拧紧”时所做的事情。这些时期称为磁场偏移和逆转。