Interhemispheric high-frequency geomagnetic field dynamics

点击翻译按钮获取中文摘要

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.