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Reconstructing holocene geomagnetic field variation : New methods, models and implications

Nilsson, Andreas LU ; Holme, Richard; Korte, Monika; Suttie, Neil and Hill, Mimi (2014) In Geophysical Journal International 198(1). p.229-248
Abstract

Reconstructions of the Holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long-term solar-terrestrial relationships and as relative dating tools for geological and archaeological archives. Here, we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts, igneous rocks and sediment records. A new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data. To reduce the influence of a few individual records all sedimentary data are resampled in 50-yr... (More)

Reconstructions of the Holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long-term solar-terrestrial relationships and as relative dating tools for geological and archaeological archives. Here, we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts, igneous rocks and sediment records. A new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data. To reduce the influence of a few individual records all sedimentary data are resampled in 50-yr bins, which also means that more weight is given to archaeomagnetic data during the inversion. The sedimentary declination data are treated as relative values and adjusted iteratively based on prior information. Finally, an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties, often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model. As a result of the data adjustments, power has been shifted from quadrupole and octupole to higher degrees compared with previous Holocene geomagnetic field models. We find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr. The new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder, possibly originating from the equator.

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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Archaeomagnetism, Palaeointensity, Palaeomagnetic secular variation
in
Geophysical Journal International
volume
198
issue
1
pages
20 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:84905918453
ISSN
0956-540X
DOI
10.1093/gji/ggu120
language
English
LU publication?
no
id
a3293d8e-9bf7-4a58-984a-2fdad4de9b82
date added to LUP
2016-05-09 12:42:36
date last changed
2018-09-16 04:36:20
@article{a3293d8e-9bf7-4a58-984a-2fdad4de9b82,
  abstract     = {<p>Reconstructions of the Holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long-term solar-terrestrial relationships and as relative dating tools for geological and archaeological archives. Here, we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts, igneous rocks and sediment records. A new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data. To reduce the influence of a few individual records all sedimentary data are resampled in 50-yr bins, which also means that more weight is given to archaeomagnetic data during the inversion. The sedimentary declination data are treated as relative values and adjusted iteratively based on prior information. Finally, an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties, often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model. As a result of the data adjustments, power has been shifted from quadrupole and octupole to higher degrees compared with previous Holocene geomagnetic field models. We find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr. The new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder, possibly originating from the equator.</p>},
  author       = {Nilsson, Andreas and Holme, Richard and Korte, Monika and Suttie, Neil and Hill, Mimi},
  issn         = {0956-540X},
  keyword      = {Archaeomagnetism,Palaeointensity,Palaeomagnetic secular variation},
  language     = {eng},
  number       = {1},
  pages        = {229--248},
  publisher    = {Wiley-Blackwell},
  series       = {Geophysical Journal International},
  title        = {Reconstructing holocene geomagnetic field variation : New methods, models and implications},
  url          = {http://dx.doi.org/10.1093/gji/ggu120},
  volume       = {198},
  year         = {2014},
}