Modelling the archaeomagnetic field under spatial constraints from dynamo simulations: a resolution analysis

Sanchez, Sabrina; Fournier, Alexandre; Aubert, Julien; Cosme, Emmanuel; Gallet, Yves

doi:10.1093/gji/ggw316

Cited by 23 publications

(29 citation statements)

References 52 publications

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“…When using reference curves for dating one must consider the distance Figure 5: Overview of geomagnetic field models and dipole reconstructions for historical times through to ka. Model references: gufm1 (Jackson et al, 2000), HHK1998 (Hongre et al, 1998), SCHA.DI.00 (Pavón-Carrasco et al, 2008b), SCHA.DI.00-F (Pavón-Carrasco et al, 2008a), GMADE2K.1 (Lodge and Holme, 2009), VHLP2008 (Valet et al, 2008), CJL2000 (Constable et al, 2000), A FM, ASD FM, and ASDI FM (Licht et al, 2013), AmR (Sanchez et al, 2016), COV-ARCH and COV-LAKE (Hellio and Gillet, 2018), CALS3k.x, ARCH3k.1, and SED3k.1 Constable, 2003, 2005;Korte et al, 2009 (Ohno and Hamano, 1992), OH1993 (Ohno and Hamano, 1993), CALS10k.x Constable et al, 2016), HFMx, and HFM.OL1.A1 (Panovska et al, 2015;Constable et al, 2016), YOS2000 (Yang et al, 2000), SHA.DIF.14k (Pavón-Carrasco et al, 2014b), MS1982 (McElhinny and Senanayake, 1982), and GEO-MAGIA VADM (Knudsen et al, 2008).…”

Section: Reference Curves and Modelsmentioning

confidence: 99%

Refining Holocene geochronologies using palaeomagnetic records

Korte

Brown

Gunnarson

et al. 2019

Quaternary Geochronology

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The aperiodic nature of geomagnetic field variations, both in intensity and direction, can aid in dating archaeological artefacts, volcanic rocks, and sediment records that carry a palaeomagnetic signal. The success of palaeomagnetic dating relies upon our knowledge of past field variations at specific locations. Regional archaeo-and palaeomagnetic reference curves and predictions from global geomagnetic field models provide our best description of field variations through the Holocene. State-of-the-art palaeomagnetic laboratory practices and accurate independent age controls are prerequisites for deriving reliable reference curves and models from archaeological, volcanic, and sedimentary palaeomagnetic data. In this review paper we give an overview of these prerequisites and the available reference curves and models, discuss techniques for palaeomagnetic dating, and outline its limitations. In particular, palaeomagnetic dating on its own cannot give unique results, but rather serves to refine or confirm ages obtained by other methods. Owing

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Section: Reference Curves and Modelsmentioning

confidence: 99%

Refining Holocene geochronologies using palaeomagnetic records

Korte

Brown

Gunnarson

et al. 2019

Quaternary Geochronology

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“…We chose degree 5 for the limits of the explored ranges because it is often considered as the limit of reliable resolution in archeomagnetic field models (e.g. Licht et al 2013;Sanchez et al 2016). For simplicity the filter was applied to an early snapshot of CHAOS5 where one minimum is found.…”

Section: Surface Intensity Minima In Geomagnetic Field Modelsmentioning

confidence: 99%

Preferred locations of weak surface field in numerical dynamos with heterogeneous core–mantle boundary heat flux: consequences for the South Atlantic Anomaly

Terra-Nova

Amit

Choblet

2019

Geophysical Journal International

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S U M M A R YThe present-day geomagnetic field is characterized by a region of weak surface intensity, the socalled South Atlantic Anomaly (SAA). We identify the locations of surface intensity minima in modern, historical and archeomagnetic field models. We then investigate whether lower mantle thermal heterogeneity may explain the location of the SAA. We run numerical dynamos with heterogeneous core-mantle boundary (CMB) heat flux inferred from a lowermost mantle tomography model, varying dynamo internal control parameters as well as the amplitude of the CMB heat flux heterogeneity. Histograms of the longitude and latitude of surface intensity minima show the persistence of different locations. We find two preferred longitudes of surface intensity minima, one close to the present SAA minimum longitude. In contrast, in the dynamo models and in the archeomagnetic field models the surface intensity minima are often close to the equator, whereas the present-day SAA is at mid-latitudes. We demonstrate that the determining ingredients in dynamo models to reproduce the SAA latitude are related to north-south asymmetries of reversed and normal geomagnetic flux on the CMB. The imposed heterogeneous heat flux leads to more convective and magnetic activities in the Northern Hemisphere. Large time-average upwelling structure below the South Atlantic in the dynamo models correlates well with the present-day SAA region. Scaling laws analysis indicates that the persistence of surface minima longitudes is favored by slow rotation, strong convection and large heat flux heterogeneity. Furthermore, increasing mantle control yields two preferred longitudes and southern surface minima, the latter indicating that the present-day southern location of the SAA is mantle controlled. However, the rareness of mid-latitude minima in dynamo models and archeomagnetic field models leads us to speculate that the SAA midlatitude value at present is possibly unusual.

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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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Modelling the archaeomagnetic field under spatial constraints from dynamo simulations: a resolution analysis

Cited by 23 publications

References 52 publications

Refining Holocene geochronologies using palaeomagnetic records

Refining Holocene geochronologies using palaeomagnetic records

Preferred locations of weak surface field in numerical dynamos with heterogeneous core–mantle boundary heat flux: consequences for the South Atlantic Anomaly

One Hundred Thousand Years of Geomagnetic Field Evolution

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