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Schlagwörter:
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Zusammenfassung:
The geomagnetic field varies on a range of spatial and temporal scales. Recent global, multi-millennial models greatly improved our knowledge of the geomagnetic field and geomagnetic excursions. However, these models are limited by the spatial and temporal data distribution and magnetic and age uncertainties of underlying data. Variations in the production rates of cosmogenic radionuclides, such as 10Be, reconstructed from ice cores and sediments provide an independent proxy of paleointensity variations. We selected nine global 10Be records with good age control and trustworthy production rate signals. The productions estimated from paleomagnetic field models are in very good agreement with the measured 10Be data. The 10Be records are then combined with paleomagnetic data to better constrain the geomagnetic field evolution over the past 70 ka. Two approaches are explored, 10Be records inverted in the models as a function of the dipole only and of all Gauss coefficients, in the same way as paleomagnetic intensities. Model predictions and global field maps show that the cosmogenic isotope records have regional effects on the reconstructed variations, especially those with high resolution (Greenland ice cores), and over periods when available in large numbers, such as the Laschamps excursion period. It is not fully clear whether these reflect regional geomagnetic influences on isotope production or if they are artefacts not related to regional magnetic field variations. In general, 10Be data confirm the variations already resolved with the paleomagnetic data, thus, serving as an independent test for the global geomagnetic field models.
