Interhemispheric high-frequency geomagnetic field dynamics

最近的直接观测表明，地磁场在上个世纪发生了巨大的变化。北磁极（NMP）位置的变化和偶极子场（即地球磁场的主要组成部分）的迅速减弱最能说明这一点。NMP在历史时期（过去400年）仅限于加拿大的北极地区，最近已经进入北冰洋。直接观测表明，自20世纪70年代初以来，NMP的迁移急剧增加，从9 km/年增加到41 km/年，2003年增加到近60 km/年，而在过去50年中，Resolute湾地磁观测站测量的强度年变化率从约10 nT/年增加到近70 nT/年。此外，NMP最近的迁移发生在北美和西伯利亚两个重要的地磁通量观测区之间。这些磁通量裂片在驱动全新世地磁变率中的作用目前尚不清楚，但可能是关键。同样，最近南半球的卫星观测和地磁模型显示，在过去的几个世纪里，南半球出现了一个重要的磁异常。这个被命名为南大西洋磁异常的异常的起源和原因仍然未知。这些最近的惊人变化导致了以下问题的形成：“我们是否处于大规模地磁变化的初始阶段，甚至是逆转？”以及“这些变化是否与通量叶的动力学有关？”要回答这些基本问题，必须首先把历史记录放在一个更长的地质背景中。我的发现基金项目的长期目标是确定晚第四纪地磁场的高频动力学，特别强调两个半球高纬度地区的突变。

Recent direct observations have demonstrated that the geomagnetic field has undergone dramatic changes over the last century. This is best illustrated by changes in the position of the North Magnetic Pole (NMP) and the rapid decline of the dipole field (i.e, the main component of Earth's magnetic field). The NMP, restricted to the Canadian Arctic during historical times (last 400 yrs), has recently moved into the Arctic Ocean. Direct observations reveal that the migration of the NMP has increased dramatically since the early 1970's from 9 km/yr to 41 km/yr and to almost 60 km/yr in 2003, whereas the annual rate of change in intensity measured at the Resolute Bay geomagnetic observatory has increased from about 10 nT/yr to almost 70 nT/yr over the last 50 years. In addition, the recent migration of the NMP occurs between two important areas of observed geomagnetic fluxes in North America and Siberia. The role of these geomagnetic flux lobes in driving Holocene geomagnetic variability is currently unknown, but maybe key. Similarly, recent satellite observations in the Southern Hemisphere and geomagnetic models reveal an important magnetic anomaly developed over the last centuries in the Southern Hemisphere. The origin and cause of this anomaly, named the South Atlantic Magnetic Anomaly are still unknown. These recent spectacular changes lead to the formulation of the following questions: “Are we in the initial stages of a large-scale geomagnetic change, or even a reversal?” and “are these changes associated with the dynamics of flux lobes?”. To answer these fundamental questions, the historical record must first be placed into a longer geological context. The long-term goal of my Discovery Grant program is to determine the high frequency dynamics of the geomagnetic field during the Late Quaternary with a special emphasis on abrupt changes in the high latitudes of both hemispheres. This research program will provide the first large-scale Holocene interhemispheric study of high latitude geomagnetic field dynamics. In addition, by selecting coring sites with very high sediment accumulation rates, the proposed research will investigate geomagnetic field variability at a temporal resolution that is just beginning to be explored, the centennial to millennial timescales. These observations will: 1) enable testing of hypotheses developed from the historical geomagnetic record, 2) yield invaluable data for geodynamo modelling, and 3) place the current dramatic collapse and migration of the NMP into a detailed geological context. The proposed research will also provide novel data to enhance our understanding of Sun/Earth interactions, as the combination of paleomagnetic and 10Be analysis from the same cores will help decipher the influence of the geomagnetic field on the production rate of cosmogenic isotopes, with practical implications for dating, space weather, telecommunications and climate.