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Millennial scale cyclicity in the geodynamo inferred from a dipole tilt reconstruction

Nilsson, Andreas LU ; Muscheler, Raimund LU and Snowball, Ian LU (2011) In Earth and Planetary Science Letters 311(3-4). p.299-305
Abstract
Constraining past changes in the strength and configuration of the geomagnetic field provides a valuable perspective on the processes that govern the geodynamo. Here we update a modelled dipole tilt reconstruction for the last 9000 years by using palaeomagnetic records that originate from globally well-distributed sites. Some features predicted by earlier dipole models become more distinct due to added data sets. We identify a dominant 1350-year cycle in the dipole tilt variations and two preferred states of the dipole axis with north geomagnetic pole longitudes confined to either c. 120 degrees West or c. 30 degrees East. The dipole tilt reconstruction is shown to be consistent with independent geomagnetic field intensity data from... (More)
Constraining past changes in the strength and configuration of the geomagnetic field provides a valuable perspective on the processes that govern the geodynamo. Here we update a modelled dipole tilt reconstruction for the last 9000 years by using palaeomagnetic records that originate from globally well-distributed sites. Some features predicted by earlier dipole models become more distinct due to added data sets. We identify a dominant 1350-year cycle in the dipole tilt variations and two preferred states of the dipole axis with north geomagnetic pole longitudes confined to either c. 120 degrees West or c. 30 degrees East. The dipole tilt reconstruction is shown to be consistent with independent geomagnetic field intensity data from western Eurasia, which show generally higher intensities when the dipole is tilted towards this region. Our study implies that VADM reconstructions that are constrained by a biased spatial distribution of data can show variations resulting from dipole tilt instead of true dipole moment. The preferred states of the modelled dipole axis can be related to the four semi-stationary high latitude flux lobes that have been observed at the core-mantle boundary in long-term time averaged palaeomagnetic field models. The tilt episodes towards 30 degrees East in the northern hemisphere are perhaps related to the appearance of a high intensity flux lobe beneath western Eurasia. The dipole tilt reconstruction is highly correlated to millennial scale variations in the length of day that have been reconstructed from ancient records of eclipses, which indicates that the cyclicity may constitute an important component in core flow dynamics. (C) 2011 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Holocene, geomagnetic field, palaeomagnetism, dipole tilt, cosmogenic, radionuclides
in
Earth and Planetary Science Letters
volume
311
issue
3-4
pages
299 - 305
publisher
Elsevier
external identifiers
  • wos:000299609200010
  • scopus:80054122812
ISSN
1385-013X
DOI
10.1016/j.epsl.2011.09.030
language
English
LU publication?
yes
id
0f78ac1e-4de2-4b29-991b-5415a9299b36 (old id 2345020)
date added to LUP
2012-02-24 13:30:59
date last changed
2017-08-06 03:18:23
@article{0f78ac1e-4de2-4b29-991b-5415a9299b36,
  abstract     = {Constraining past changes in the strength and configuration of the geomagnetic field provides a valuable perspective on the processes that govern the geodynamo. Here we update a modelled dipole tilt reconstruction for the last 9000 years by using palaeomagnetic records that originate from globally well-distributed sites. Some features predicted by earlier dipole models become more distinct due to added data sets. We identify a dominant 1350-year cycle in the dipole tilt variations and two preferred states of the dipole axis with north geomagnetic pole longitudes confined to either c. 120 degrees West or c. 30 degrees East. The dipole tilt reconstruction is shown to be consistent with independent geomagnetic field intensity data from western Eurasia, which show generally higher intensities when the dipole is tilted towards this region. Our study implies that VADM reconstructions that are constrained by a biased spatial distribution of data can show variations resulting from dipole tilt instead of true dipole moment. The preferred states of the modelled dipole axis can be related to the four semi-stationary high latitude flux lobes that have been observed at the core-mantle boundary in long-term time averaged palaeomagnetic field models. The tilt episodes towards 30 degrees East in the northern hemisphere are perhaps related to the appearance of a high intensity flux lobe beneath western Eurasia. The dipole tilt reconstruction is highly correlated to millennial scale variations in the length of day that have been reconstructed from ancient records of eclipses, which indicates that the cyclicity may constitute an important component in core flow dynamics. (C) 2011 Elsevier B.V. All rights reserved.},
  author       = {Nilsson, Andreas and Muscheler, Raimund and Snowball, Ian},
  issn         = {1385-013X},
  keyword      = {Holocene,geomagnetic field,palaeomagnetism,dipole tilt,cosmogenic,radionuclides},
  language     = {eng},
  number       = {3-4},
  pages        = {299--305},
  publisher    = {Elsevier},
  series       = {Earth and Planetary Science Letters},
  title        = {Millennial scale cyclicity in the geodynamo inferred from a dipole tilt reconstruction},
  url          = {http://dx.doi.org/10.1016/j.epsl.2011.09.030},
  volume       = {311},
  year         = {2011},
}