ALBERT

Description: Cosmogenic radionuclide records from polar ice cores provide unique insights into past cosmic ray flux variations. They allow reconstructions of past solar activity, space weather, and geomagnetic field changes, and provide insights into past carbon cycle changes. However, all these applications rely on the proportionality of the ice core radionuclide records to the global mean production rate changes. This premise has been long debated from a model and data-perspective. Here, we address this issue through atmospheric mixing model experiments and comparison to independent data. We find that all mixing scenarios, which do not assume complete tropospheric mixing, result in a polar bias. This bias is more prominent for geomagnetic field changes than solar modulation changes. The most likely scenario, supported by independent geomagnetic field records and marine 10Be during the Laschamps geomagnetic field minimum, results in a dampening of geomagnetic field induced changes by 23-37% and an enhancement of solar-induced changes by 7-8%. During the Holocene, we do not find conclusive evidence for a polar bias. We propose a correction function that allows deconvolving the glacial ice core record in order to restore proportionality to the global mean signal.

Description: 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 〈sup〉10〈/sup〉Be, reconstructed from ice cores and sediments provide an independent proxy of paleointensity variations. We selected nine global 〈sup〉10〈/sup〉Be 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 〈sup〉10〈/sup〉Be data. The 〈sup〉10〈/sup〉Be records are then combined with paleomagnetic data to better constrain the geomagnetic field evolution over the past 70 ka. Two approaches are explored, 〈sup〉10〈/sup〉Be 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, 〈sup〉10〈/sup〉Be data confirm the variations already resolved with the paleomagnetic data, thus, serving as an independent test for the global geomagnetic field models.

Description: The project “Bimbim’s Team: A Journey to the Planets” was awarded by Europlanet with the main goal to awaken children’s curiosity for planetary sciences. Science outreach to children is a major challenge for professionals in any field, especially because of the complexity involved. Initiating children into scientific subjects is not a trivial task. In his project, we tackle the challenge of reaching as many children as possible, combining science and art in an innovative strategy. “Bimbim’s team” are puppets theater characters which have the power to fascinate children and transmit science in an unconventional way. Short movies were produced with three stories about the planets: general overview of all solar system planets, Earth and Mars. The videos come with illustrations and animations to better express the scientific content. They were recorded in three languages (Portuguese, English and French) in hopes of reaching an international scale. We expect that these stories will also call the attention of schools and parents to bring science closer to their children. Another outcome of the project is the involvement of female scientists and the possibility to attract more scientists, especially the minority groups.

Description: Paleosecular variation (PSV) is a phenomenon that describes how the Earth's magnetic field is constantly changing through time and space. Thermal remanent magnetization (TRM) spot data retained in fired archaeological objects and lavas can be used to create global and/or regional PSV models for the past few thousand years. Numerous regional PSV curves with reasonable resolution were successfully created in several European countries, the United States, Mexico, China, and the Near East. On the other hand, due to a lack of TRM data, several low-latitude regions and the majority of southern hemisphere regions do not currently have comparable models. Egypt is one of these regions without a PSV model, despite having many ancient sites with a wealth of archaeological knowledge. According to the GEOMAGIA50.v3 database, Egypt has 170 intensity, 27 inclination, and 1 declination data points for the past 6,000 years. One conspicuous feature from the previous Egyptian data set is the presence of two intensity peaks (≈80 μT) at ≈1400 BC and ≈500 BC, which are accompanied by steep inclination (〉70〈sup〉o〈/sup〉). These peaks can be correlated to the so-called Levantine Iron Age geomagnetic anomaly (LIAA), which was proposed for the first time in the Near East around ≈ 980 BCE. In this study, a reference PSV curve for Egypt will be constructed. This reference curve can be used as an effective dating method for ancient Egyptian artefacts. Furthermore, using the curve, it is conceivable to observe how the LIAA has changed across time and space.

Description: Magnetic field reversals, which occur when the polarity of the field reverses and the global field strength drops to its lowest level, are the most significant changes in the Earth's magnetic field identified by paleomagnetic data collected mostly from volcanic and sediment records. Matuyama-Brunhes (MB), the most recent field reversal that happened ~780,000 ago, is documented by tens of these records, offering the opportunity to study the mechanism of reversal and features of the magnetic field during polarity transition globally. Nevertheless, some MB records lack precise chronology information, have challenges with magnetization acquisition (sediments), provide discontinuous paleomagnetic data (volcanics), and they are unevenly distributed around the globe. Such limitations raise doubt on some proposed magnetic field features during MB, such as preferred virtual geomagnetic poles (VGP) paths, recurring VGP clusters, and precursor and rebound phases. Likewise, using these non-ideal data records for constructing spherical harmonic global models may result in an inaccurate interpretation of the transition field, including field morphology and the evolution of dipole and non-dipole field contributions. We constructed a suite of global models based on various data sets. Data inputs are classified according to type, geographic distribution, age data reliability, temporal resolution, reliability of demagnetization and relative paleointensity results, and consistency of these results among adjacent records. By comparing the model outputs from each data category, we will identify the robust magnetic field characteristics during MB reversal.