Both social and engineering factors must be further explored and scrutinized across the globe—as should notions of justice related to flooding impacts and responses.
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Edited by Lisa Tauxe, University of California, San Diego, La Jolla, CA, and approved July 23, 2018 (received for review November 22, 2017)
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.
- multidecadally resolved polarity oscillations
- geomagnetic excursion
- abrupt reversal transition
- asymmetrical interhemispheric polarity drifts
- stalagmite U-Th dating
Footnotes
↵1Y.-M.C., X.J., and Q.L. contributed equally to this work.
- ↵2To whom correspondence may be addressed. Email: river{at}ntu.edu.tw or chouym{at}sustc.edu.cn.
Author contributions: C.-C.S. directed this project; Y.-M.C., Q.L., T.-Q.L., and C.-C.S. designed research; Y.-M.C., X.J., H.-M.H., C.-C. Wu, J.L., Z.J., C.-C. Wang, Y.-F.S., C.-C.C., L.T., M.A.L., Y.P., R.Z., Y.H., Y.-C.C., A.-H.T., and C.-C.S. performed research; Y.-M.C., X.J., Q.L., H.-M.H., C.-C. Wu, J.L., Z.J., T.-Q.L., C.-C. Wang, Y.-F.S., C.-C.C., L.T., M.A.L., Y.P., R.Z., Y.H., Y.-C.C., A.-H.T., A.P.R., X.Z., and C.-C.S. analyzed data; and Y.-M.C., X.J., Q.L., H.-M.H., C.-C. Wu, T.-Q.L., A.P.R., X.Z., and C.-C.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1720404115/-/DCSupplemental.
Published under the PNAS license.
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Multidecadally resolved polarity oscillations during a geomagnetic excursion
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