Rapid Geomagnetic Oscillations and Centennial Polarity Reversals Identified
The intensity of the Earth’s magnetic field varies continuously and has decreased by 10-15% over the past century, leading to suggestions of a possible impending reversal. However, the transition time and detailed process of a reversal event have remained elusive even though the geomagnetic field had been well known for over two thousand years and the geomagnetic reversals were discovered in igneous rocks a century ago.
Being the leader and corresponding author, Dr. Chuan-Chou Shen (沈川洲), a distinguished professor of the NTU Department of Geosciences, and his team published their newest research findings in the internationally renowned journal, Proceedings of the National Academy of Sciences of the United States of America (PNAS) on August 20. Dr. Shen and his team present a multidecadally resolved geomagnetic record of a stalagmite dating back to 107-91 thousand years ago collected from Sanxing Cave (三星洞) in southern China.
The combined use of the front-end U-Th radioisotopic dating techniques, which boast a precision down to few decades, and high-sensitivity instrumental analysis on the ultra-trace amount of magnetic minerals in stalagmites from southern China has generated results that reveal details of repeated asymmetric inter-hemispheric polarity oscillations on centennial-to-millennial timescales. One surprisingly abrupt centennial reversal transition 98 thousand years ago occurred in just 144 years, which is 10 times shorter than previously thought. If such an abrupt event should occur in the future, it could confuse animal navigation, disturb radio communications, and damage satellites, electronic power systems, and global internet systems.
The full research article “Multidecadally Resolved Polarity Oscillations during a Geomagnetic Excursion” is available at http://www.pnas.org/content/early/2018/08/14/1720404115, DOI: 10.1073/pnas.1720404115.
Chuan-Chou Shen, National Taiwan University, Taipei, Taiwan, ROC; Tel: 886-2-33665878; E-mail: email@example.com;
Yu-Min Chou, Southern University of Science and Technology, Shenzhen, P. R. China; Tel: 86-13927454320; E-mail: firstname.lastname@example.org;
Andrew P. Roberts, Australian National University, Canberra, Australia; Tel: 61-2-61251420; Mobile: 61-4-34668243; E-mail: email@example.com.
Prof. Chuan-Chou Shen (shown on monitor) joins the video press conference held at NTU.
NTU holds a video press conference for the study conducted by a multinational team led by Prof. Chuan-Chou Shen.
Opening address by NTU Interim President Tei-Wei Kuo (郭大維).
Prof. Chuan-Chou Shen (left) and the first author of the paper, Prof. Yu-Min Chou (周祐民; right) during a field survey. (Image courtesy of Chuan-Chou Shen)
Prof. Chuan-Chou Shen in a cave in south China. (Image courtesy of Chuan-Chou Shen)
Stalagmites in southern China preserve the data of detailed polarity oscillations and centennial reversal events. (Image courtesy of Chuan-Chou Shen)
Researchers during a cave survey. (Image courtesy of Chuan-Chou Shen)
The geomagnetic field shields the Earth from direct impact of solar wind and cosmic radiation. (Image courtesy of Chuan-Chou Shen)
(A) Stalagmite-revealed unique oscillations of the geomagnetic pole on centennial-to-millennial timescales. One surprisingly rapid reversal event occurred in an approximate 144-year period 98 thousand years ago. (B) The calculated transition path of the geomagnetic pole during the reversal event from 98,360 to 98,216 years before present (yr BP). Star symbol denotes Sanxing Cave where the stalagmite was collected. (Image courtesy of Chuan-Chou Shen)