Persistent Influence of Non‐Dipole Geomagnetic Field on East Asia Over the Past 4,000 Years

• Published in: Journal of geophysical research. Solid earth 2023-12, Vol.128 (12), p.n/a
• Main Authors: Li, Hai, Tang, Jianhui, Gai, Congcong, Zhang, Weijie, Humbert, Fabien, Ni, Youzhong, Chou, Yu‐Min, Liu, Qingsong
• Format: Article
• Language: English
• Subjects: Carbon 14; Cores; Cosmic radiation; Cosmic ray showers; Cosmic rays; Dipoles; Earth; Earth mantle; Earth Sciences; Fluctuations; Geomagnetic field; Geomagnetism; Geophysics; Latitude; Magnetic field; Magnetic fields; Magnetic flux; Magnetic permeability; Magnetic susceptibility; Magnetite; Palaeomagnetism; Paleomagnetism; Radiocarbon dating; Radiometric dating; Sciences of the Universe; Secular variations; Sediment; Sediments; Solar wind; Variation
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1029/2023JB027359

The observed variations in intense geomagnetic flux lobes have a significant impact on regional geomagnetic fields, and produce unique geomagnetic characteristics. To investigate the time‐dependent effect of the Siberian flux lobe on the geomagnetic field in East Asia, we reconstructed a stacked full‐vector paleomagnetic secular variation record (since 2000 BCE) from three sediment cores collected in the Bohai Sea, China. Age models of the studied cores were established through a combination of radiocarbon 14C dating and inter‐profile correlation of mass‐normalized magnetic susceptibility. Rock magnetic results indicate that fine‐grained magnetite is the primary remanent carrier. We found that the paleomagnetic field records in the Bohai Sea correspond more closely with those from the middle latitudes, rather than the low latitudes. This was primarily attributed to the variation of the Siberian flux lobe. This study provides a better understanding of the contrasting patterns of regional geomagnetic fields in East Asia, and emphasizes the significant role played by the Siberian flux intensity lobe in shaping their formation. Plain Language Summary The Earth's magnetic field is in a constant state of flux, both temporally and spatially, and plays a crucial role in protecting our planet from solar wind and cosmic rays. The long‐term variation of the Earth's magnetic field is closely linked with the magnetic flux patch situated at the core‐mantle boundary. However, our understanding of the evolution of magnetic flux patches has been limited by the use of short‐term instrumental data and discrete archeomagnetic data. In this paper, we reconstruct a ∼4,000‐year high‐resolution full‐vector paleomagnetic record from sediments in the Bohai Sea, China. Our findings reveal a clear contrast in the paleomagnetic variations between the middle and low latitudes of East Asia. We proposed that the Siberian flux intensity lobe likely played an important role in the observed paleomagnetic behavior discrepancy between the low‐ and mid‐latitudes of East Asia. Key Points A multi‐decadal resolution paleomagnetic record spanning approximately 4,000 years has been derived from sediments in the Bohai Sea, China The paleomagnetic behavior differs between middle and low latitudes across East Asia, indicating the variation of the Siberian flux lobe The disparity in inclination between the Chinese and Levantine spikes implies that these spikes arise from separate magnetic flux patches