Emergence and evolution of the South Atlantic Anomaly revealed by the new paleomagnetic reconstruction SHAWQ2k

Campuzano, Saioa A.; Gómez‐Paccard, Miriam; Pavón‐Carrasco, F. J.; Osete, María Luisa

doi:10.1016/j.epsl.2019.01.050

Cited by 78 publications

(119 citation statements)

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“…However, the SAA characterization has been somewhat crude. In this paper we will show that SAA area estimates based on a fixed thershold (De Santis et al, 2013;Pavón-Carrasco and De Santis, 2016;Campuzano et al, 2019) are strongly affected by global axial dipole variations and as such do not represent adequately regional morphological changes. Furthermore, SAA center estimates based on surface minimum positions (e.g.…”

Section: Introductionmentioning

confidence: 92%

“…In contrast, some archeomagnetic field models exhibit persistent minimum surface intensity in the South Atlantic (Brown et al, 2018;Hellio and Gillet, 2018). Campuzano et al (2019) found that the SAA has been expanding and westward drifting since 1400. In addition, based on archeological materials, it was argued that the SAA has influenced the surface geomagnetic field for several millennia in Africa (Tarduno et al, 2015;Hare et al, 2018) and South America (Trindade et al, 2018;Hartmann et al, 2019).…”

Section: Introductionmentioning

confidence: 94%

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Non-monotonous growth and motion of the South Atlantic Anomaly

Amit

Terra-Nova

Lézin

et al. 2020

Preprint

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The South Atlantic Anomaly (SAA) is a region at Earth’s surface where the intensity of the magnetic field is particularly low. Accurate characterization of the SAA is important for both fundamental understanding of core dynamics and the geodynamo as well as societal issues such as the erosion of instruments at surface observatories and onboard spacecrafts. Previous studies applied crude measures of the SAA. Here we propose new measures to better characterize the SAA area and center, accounting for global dipole changes and shape anisotropy. Applying our characterization to a geomagnetic field model covering the historical era, we find that the mean SAA area increase and westward drift rates are twice slower than previously reported. Our results reveal that the SAA area and center are much more time-dependent, including episodes of area decrease, eastward drift and rapid southward drift. We interpret these special events in terms of the secular variation of relevant large-scale geomagnetic flux patches on the core-mantle boundary. Our characterization may be used as a constraint on Earth-like numerical dynamo models.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 94%

Non-monotonous growth and motion of the South Atlantic Anomaly

Amit

Terra-Nova

Lézin

et al. 2020

Preprint

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“…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%

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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“…Understanding the onset and the evolution of this region is challenged by the lack of geomagnetic data -especially paleointensity data-from the Southern Hemisphere. A recent study by Campuzano et al (2019) developed a new geomagnetic field model based on global geomagnetic data. This model links the onset of the South Atlantic Anomaly to reverse flux patches at the core-mantle boundary from 950 AD onwards and suggests that the SAA emerges East of the African continent.…”

Section: Summary Of Thesis Chaptersmentioning

confidence: 99%

“…And when and where did the reverse flux patch form, and when did it start moving westwards (e.g. Jackson et al, 2000;Dumberry & Finlay, 2007, Pavon-Carrasco et al, 2016, Campuzano et al, 2019? A study on 46 and 90 ka lavas from Tristan da Cunha (Shah et al, 2016), indicate the possibility of a persisting or recurring low intensity anomaly in this region.…”

Section: Introductionmentioning

confidence: 99%

Highs, Lows, and Puzzling Intensity Variations of the Earth’s Magnetic Field

Béguin¹

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The Earth's magnetic field has a pivotal role in the Earth Sciences, its applications range from plate tectonics, to magnetostratigraphy. Together with seismology, it is the only window into the deep Earth and the Earth's core. In everyday life, the Earth's magnetic field is important for navigation devices. More importantly, the Earth's magnetic field protects the Earth against harmful solar radiation, and it protects satellites orbiting the Earth. Without the Earth's magnetic field, the atmosphere would have been stripped away and life on Earth would not have been possible. The growth of a stable magnetic field is thought to have been instrumental for the beginning of early life. Understanding the evolution and behavior of the Earth's magnetic field is therefore of great importance. In this thesis I will focus on the study of the strength of the Earth's magnetic field, its intensity. Therefore, I set out to unravel fast and local fluctuations in the direction and strength of the geomagnetic field. Paleointensity-the key to understanding the Earth's magnetic field Methods to derive paleointensity estimates from absolute recorders, e.g. lavas or archaeomagnetic materials, rely on comparing the ancient magnetization of the recorders that was obtained during cooling in the Earth's magnetic field, with a laboratory induced magnetization. As simple as this might sound, obtaining reliable and high quality paleointensity estimates from lavas is notoriously difficult. Besides the laborious effort to obtain paleointensity measurements, there is little consensus on the best approach of interpreting the measurement data and how to distinguish between high and low quality results. The first to propose to obtain information on the past state of the strength of the Earth's magnetic field by studying thermal remanences was Guiseppe Folgheraiter. He proposed that by reheating ancient pottery, the intensity of the ancient magnetization could be compared to the present magnetization (Folgheraiter, 1899). Folgheraiter did find that this method might lead to 'too uncertain results' when the baked vases were reheated several times. Almost forty years later an experimental protocol for estimating the ratio of natural remanent magnetization (NRM) and a laboratory acquired thermal remanence magnetization (TRM) was described by Johann Koenigsberger (1936). Koenigsberger used prologue a comparison of quasi-perpendicular and doubleheating thellier-style paleointensity techniques-towards an optimal protocol 1

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Emergence and evolution of the South Atlantic Anomaly revealed by the new paleomagnetic reconstruction SHAWQ2k

Cited by 78 publications

References 68 publications

Non-monotonous growth and motion of the South Atlantic Anomaly

Non-monotonous growth and motion of the South Atlantic Anomaly

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

Highs, Lows, and Puzzling Intensity Variations of the Earth’s Magnetic Field

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