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Recurrent ancient geomagnetic field anomalies shed light on future evolution of the South Atlantic Anomaly

2022 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 788

Using archeological and geological records, the authors present a probabilistic geomagnetic field model over the past 9,000 years and report evidence for recurrent hemispherical field asymmetries and geomagnetic field anomalies similar to the present-day Sout…

Study snapshot

Publicationmanual · 2022
Study typeother
Reported directionUnclear
Evidence ratingInsufficient

Abstract

Recurrent ancient geomagnetic field anomalies shed light on future evolution of the South Atlantic Anomaly Andreas Nilsson, Neil Suttie, Joseph S. Stoner, Raimund Muscheler. Recurrent ancient geomagnetic field anomalies shed light on future evolution of the South Atlantic Anomaly. PNAS. 2022. 119 (24) e2200749119. doi: 10.1073/pnas.2200749119. Significance Earth’s magnetic field, which is generated through convection in the liquid iron–rich outer core, acts as a shield against harmful particle radiation. During the past two centuries, the field strength has decreased rapidly as an area of weak field has expanded over the South Atlantic Ocean. The decreased shielding effect of the magnetic field in this area has important implications for low Earth-orbiting satellites and space travel. Using archeological and geological records, we have reconstructed the variations of Earth’s magnetic field over the past 9,000 y. We find evidence for recurrent magnetic field anomalies, similar to the present-day South Atlantic Anomaly, which provides insights into underlying geodynamo processes that may help predict the future development of Earth’s magnetic field. Abstract The strength of the geomagnetic field has decreased rapidly over the past two centuries, coinciding with an increasing field asymmetry due to the growth of the South Atlantic Anomaly. The underlying processes causing the decrease are debated, which has led to speculation that the field is about to reverse. Here, we present a geomagnetic field model based on indirect observations over the past 9,000 y and identify potential ancient analogs. The model is constructed using a probabilistic approach that addresses problems with age uncertainties and smoothing of sedimentary data that have hampered previous attempts. We find evidence for recurrent hemispherical field asymmetries, related to quasiperiodic millennial-scale variations in the dipole moment. Our reconstruction indicates that minima in the dipole moment tend to coincide with geomagnetic field anomalies, similar to the South Atlantic Anomaly. We propose that the period around 600 BCE, characterized by a strongly asymmetric field, could provide an analog to the present-day field. The analogy implies that the South Atlantic Anomaly will likely disappear in next few hundred years, accompanied by a return to a more symmetric field configuration and possibly, a strengthening of the axial dipole field. pnas.org

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeother
Effect directionunclear
PopulationNot supplied
Sample sizeNot supplied
Exposurepast 9,000 years (reconstruction); recent past two centuries discussed
Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Using archeological and geological records, the authors present a probabilistic geomagnetic field model over the past 9,000 years and report evidence for recurrent hemispherical field asymmetries and geomagnetic field anomalies similar to the present-day South Atlantic Anomaly. They report that minima in dipole moment tend to coincide with such anomalies and propose the period around 600 BCE as an analog, implying the South Atlantic Anomaly will likely disappear in the next few hundred years with a return to a more symmetric field and possibly a strengthening of the axial dipole field.

Outcomes measured

  • geomagnetic field strength
  • South Atlantic Anomaly (field asymmetry/anomaly)
  • dipole moment variations
  • hemispherical field asymmetries
  • future evolution of the South Atlantic Anomaly

Limitations

  • Study is based on indirect observations (archeological and geological records) rather than direct measurements.
  • Age uncertainties and smoothing of sedimentary data are noted as issues that have hampered previous attempts (addressed via probabilistic approach, but residual uncertainty may remain).
  • No health outcomes or biological endpoints are assessed; relevance is to geomagnetic field evolution and implications for satellites/space travel.
View raw extracted JSON
{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": "geomagnetic field (Earth’s magnetic field)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "past 9,000 years (reconstruction); recent past two centuries discussed"
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "geomagnetic field strength",
    "South Atlantic Anomaly (field asymmetry/anomaly)",
    "dipole moment variations",
    "hemispherical field asymmetries",
    "future evolution of the South Atlantic Anomaly"
  ],
  "main_findings": "Using archeological and geological records, the authors present a probabilistic geomagnetic field model over the past 9,000 years and report evidence for recurrent hemispherical field asymmetries and geomagnetic field anomalies similar to the present-day South Atlantic Anomaly. They report that minima in dipole moment tend to coincide with such anomalies and propose the period around 600 BCE as an analog, implying the South Atlantic Anomaly will likely disappear in the next few hundred years with a return to a more symmetric field and possibly a strengthening of the axial dipole field.",
  "effect_direction": "unclear",
  "limitations": [
    "Study is based on indirect observations (archeological and geological records) rather than direct measurements.",
    "Age uncertainties and smoothing of sedimentary data are noted as issues that have hampered previous attempts (addressed via probabilistic approach, but residual uncertainty may remain).",
    "No health outcomes or biological endpoints are assessed; relevance is to geomagnetic field evolution and implications for satellites/space travel."
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "geomagnetic field",
    "South Atlantic Anomaly",
    "dipole moment",
    "field asymmetry",
    "geodynamo",
    "probabilistic model",
    "archeological records",
    "geological records",
    "9,000 years",
    "600 BCE"
  ],
  "suggested_hubs": []
}
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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1073/pnas.2200749119
PubMed: Not supplied

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