Time-correlation-based regression of the geomagnetic field from archeological and sediment records

Hellio, Gabrielle; Gillet, Nicolas

doi:10.1093/gji/ggy214

Cited by 58 publications

(111 citation statements)

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“…Contrary to our Bayesian curve, the predictions at Mexico City of the most recent geomagnetic global models, BIGMUDI4k.1 (Arneitz et al, 2019), CALS10k.2 (Constable et al, 2016), COV-ARCH, and COV-LAKE (Hellio & Gillet, 2018), strongly smooth the secular variation (Figure 6a). Our Mexican curve is almost systematically below the models between 1500 and 300 BCE.…”

Section: Comparison With Mexican Master Curves and Global Geomagneticcontrasting

confidence: 87%

“…This clearly underlines the necessity of full vector determination for a good resolution of the secular variation of the Earth Magnetic field. (Goguitchaichvili et al, 2018;Mahgoub et al, 2019aMahgoub et al, , 2019b and the predictions of global models BIGMUDI4k.1 (Arneitz et al, 2019), CALS10k.2 (Constable et al, 2016), COV-ARCH, and COV-LAKE (Hellio & Gillet, 2018). (b) Comparison of the curve of the Virtual Axial Dipole Moment (VADM) in Mexico with data from north-western USA (Champion, 1980), the East Pacific Ridge (Gee et al, 2000;Pick & Tauxe, 1993) and Hawaii (Cromwell et al, 2018;Mankinen & Champion, 1993;Pressling et al, 2006;Pressling et al, 2007;Tema et al, 2017;Valet et al, 1998).…”

Section: Comparison With Other Regional Recordsmentioning

confidence: 99%

“…Lacustrine and marine sediments can also be used, but these continuous records provide only relative data that tend to smooth the secular variation of the geomagnetic field. Global models of the field during the Holocene were developed by inversion of absolute and/or relative data using spherical harmonic analysis in space (e.g., Arneitz et al, 2019;Constable et al, 2016;Hellio & Gillet, 2018;Pavón-Carrasco et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…One of the main consequences is the poor knowledge of dipole moment variation prior to 1840. Models disagree when to know if the dipole moment decreased regularly since~750 CE (Poletti et al, 2018) or since~1700 CE after seven centuries of stability (Hellio & Gillet, 2018). The lack of data also prevents a precise understanding of geomagnetic anomalies at the Earth's surface such as the present South Atlantic anomaly (e.g., Campuzano et al, 2019;Terra-Nova et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Secular Variation of the Intensity of the Geomagnetic Field in Mexico During the First Millennium BCE

Hervé

Perrin

Alva‐Valdivia

et al. 2019

Geochem Geophys Geosyst

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In Western Eurasia, the first millennium BCE is characterized by the fastest secular variation of the Earth Magnetic Field observed over the last millennia and by a geomagnetic anomaly centered on the Middle East. On the global scale, the variation of the dipolar field during this period remains poorly constrained because of the lack of data in other geographical areas. Here, we presented 23 new mean archaeointensity data on ceramic sherds dated between 1500 BCE and 200 CE from Chalcatzingo archaeological site in Central Mexico. Archaeointensities were determined using the classical Thellier-Thellier protocol with corrections for TRM anisotropy and cooling rate effects. Our work doubles the number of high-quality archaeointensity data in Mexico during the considered period. Using a Bayesian approach, a new secular variation curve was calculated at Mexico City between 1500 BCE and 200 CE after selection of Mexican archaeointensity data. After a period of oscillations of the intensity between 20 and 40 μT from 1500 to 300 BCE, the curve shows a large maximum`~65 μT in the second century BCE. The corresponding VADM varied between~4.0 and~11.0 × 10 22 Am 2 , which highlights further that the intensity of the geomagnetic field could vary at regional scale over a larger range as previously thought. However, this amplitude variation may be overestimated, as it does not take into account the fast directional variation observed at this time.Plain Language Summary Archaeological baked clays are the best material to reconstitute the past secular variation of the Earth magnetic field, because they acquired a generally stable thermoremanent magnetization usually parallel and proportional to the ambient field at the time of their baking. Global modeling of the geomagnetic field requires a spatial and temporal distribution of data as homogeneous as possible, which is still not the case yet. In spite of its rich archaeological heritage, high-quality archaeointensity data are still very few in Mexico. The present study focuses on pottery sherds dated between 1500 BCE and 200 CE from Chalcatzingo archaeological site in Central Mexico. We obtained 21 new mean archaeointensities, which almost doubles the high-quality Mexican dataset for this period. The new secular variation Mexican curve exhibits oscillations of the intensity between 20 and 40 μT from 1500 to 300 BCE, before a large maximum~65 μT in the second century BCE. This work will help to have a better knowledge of the variation of the dipolar geomagnetic field during the first millennium BCE, when the fastest secular variation over the last millennia was reported in the Middle East ("geomagnetic spikes").

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Section: Comparison With Mexican Master Curves and Global Geomagneticcontrasting

confidence: 87%

Section: Comparison With Other Regional Recordsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Secular Variation of the Intensity of the Geomagnetic Field in Mexico During the First Millennium BCE

Hervé

Perrin

Alva‐Valdivia

et al. 2019

Geochem Geophys Geosyst

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“…Large parts of the Southern Hemisphere, the Asian continent and the high latitudes are scarcely covered. Predictions from SH models are clearly less reliable in areas were data coverage is sparse (see, e.g., Sanchez et al, 2016;Korte et al, 2018;Hellio & Gillet, 2018).…”

Section: Global Data Coveragementioning

confidence: 99%

One Hundred Thousand Years of Geomagnetic Field Evolution

Panovska

Korte

Constable

2019

Reviews of Geophysics

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Paleomagnetic records from sediments, archeological artifacts, and lava flows provide the foundation for studying geomagnetic field changes over 0-100 ka. Late Quaternary time-varying spherical harmonic models for 0-100 ka produce a global view used to evaluate new data records, study the paleomagnetic secular variation on centennial to multimillennial timescales, and investigate extreme regional or global events such as the Laschamp geomagnetic excursion. Recent modeling results (GGF100k and LSMOD.2) are compared to previous studies based on regional or global stacks and averages of relative geomagnetic paleointensity variations. Time-averaged field structure is similar on Holocene, 100 ky, and million-year timescales. Paleosecular variation activity varies greatly over 0-100 ka, with large changes in field strength and significant morphological changes that are especially evident when field strength is low. GGF100k exhibits a factor of 4 variation in geomagnetic axial dipole moment, and higher-resolution models suggest that much larger changes are likely during global excursions. There is some suggestion of recurrent field states resembling the present-day South Atlantic Anomaly, but these are not linked to initiation or evolution of excursions. Several properties used to characterize numerical dynamo simulations as "Earth-like" are evaluated and, in future, improved models may yet reveal systematic changes linked to the onset of geomagnetic excursions. Modeling results are useful in applications ranging from ground truth and data assimilation in geodynamo simulations to providing geochronological constraints and modeling the influence of geomagnetic variations on cosmogenic isotope production rates. Plain Language SummaryEarth's magnetic field is generated by dynamo activity in the planet's liquid outer core. It provides the foundation for modern navigation, protects us from space weather, and through its variations over time provides a mechanism for studying the deep interior of our planet. On timescales beyond a few centuries there are no direct observations, and paleomagnetic records from sediments, archeological artifacts, and lava flows are used for studying the geomagnetic field. They provide a global view of the field used to evaluate new data records, study the field changes (known as paleosecular variation) on centennial to multimillennial timescales, and investigate extreme regional or global events. The average field structure is similar on 10 ky, 100 ky, and million-year timescales. The magnetic dipole moment varies by at least a factor of 4 over 0-100 ka, with higher-resolution models suggesting much larger changes during global excursions. Recent results provide a global view, allowing analysis of geomagnetic excursions, including the Laschamp excursion. Results are useful in applications ranging from ground truth and data assimilation in numerical geodynamo simulations, to providing age constraints for climate records, archeological artifacts, and sediments and for studying impact of Earth's mag...

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Correlation based time evolution of the archeomagnetic field

Schanner

Mauerberger

Korte

et al. 2020

Preprint

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Existing models of the Earth's magnetic field (EMF) for the past millennia show a variety of time-dependent features: The evolution of the South Atlantic Anomaly, the observed dipole decay in recent centuries and the movement of flux patches all take place on timescales of several hundred years (see e.g., Hartmann & Pacca, 2009;Jackson & Finlay, 2015). To accurately describe and study these features, time-resolved models are necessary. Usually, these models are inferred from two classes of data: Data from materials with thermoremanent magnetization, such as volcanic rocks, bricks or burnt clay fragments from archeologic sites, and data from marine or lacustrine sediments with embedded magnetic particles. In this paper we focus on the former class and loosely refer to it as archeomagnetic data. Existing models differ in the approach to global modeling, but are usually constructed using inversion for spherical harmonics (SH) coefficients, truncated at a certain degree.

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Time-correlation-based regression of the geomagnetic field from archeological and sediment records

Cited by 58 publications

References 61 publications

Secular Variation of the Intensity of the Geomagnetic Field in Mexico During the First Millennium BCE

Secular Variation of the Intensity of the Geomagnetic Field in Mexico During the First Millennium BCE

One Hundred Thousand Years of Geomagnetic Field Evolution

Correlation based time evolution of the archeomagnetic field

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