地磁気往復運動中に複数回分解された極性振動
【外部リンク】
http://www.pnas.org/content/early/2018/08/14/1720404115
Multidecadally resolved polarity oscillations during a geomagnetic excursion
Yu-Min Chou, Xiuyang Jiang, Qingsong Liu, Hsun-Ming Hu, Chung-Che Wu, Jianxing Liu, Zhaoxia Jiang, Teh-Quei Lee, Chun-Chieh Wang, Yen-Fang Song, Cheng-Cheng Chiang, Liangcheng Tan, Mahjoor A. Lone, Yongxin Pan, Rixiang Zhu, Yaoqi He, Yu-Chen Chou, An-Hung Tan, Andrew P. Roberts, Xiang Zhao, and Chuan-Chou Shen
PNAS August 20, 2018. 201720404; published ahead of print August 20, 2018.
Significance
A stalagmite-based paleomagnetic record of the post-Blake excursion reveals details of repeated centennial–millennial interhemispheric polarity drifts and saw-tooth inclination oscillations during periods of low geomagnetic field intensity at 100 thousand years before present. One surprisingly abrupt centennial reversal transition occurred in 144 ± 58 years (2σ) and provides unprecedented evidence that raises fundamental questions about the speed of geomagnetic field shifts. Such rapid polarity changes could severely affect satellites and human society in the future if the current geomagnetic field intensity continues to decrease.
Abstract
Polarity reversals of the geomagnetic field have occurred through billions of years of Earth history and were first revealed in the early 20th century. Almost a century later, details of transitional field behavior during geomagnetic reversals and excursions remain poorly known. Here, we present a multidecadally resolved geomagnetic excursion record from a radioisotopically dated Chinese stalagmite at 107–91 thousand years before present with age precision of several decades. The duration of geomagnetic directional oscillations ranged from several centuries at 106–103 thousand years before present to millennia at 98–92 thousand years before present, with one abrupt reversal transition occurring in one to two centuries when the field was weakest. These features indicate prolonged geodynamo instability. Repeated asymmetrical interhemispheric polarity drifts associated with weak dipole fields likely originated in Earth’s deep interior. If such rapid polarity changes occurred in future, they could severely affect satellites and human society.
