An Antarctic view of Beryllium-10 and solar activity for the past millennium |
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Authors: | Gilles Delaygue Edouard Bard |
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Institution: | 1. Universit?? Aix-Marseille III/CNRS/IRD/Coll??ge de France, CEREGE, Europ?le de l??Arbois BP80, 13545, Aix-en-Provence Cedex4, France 2. Universit?? Joseph Fourier-Grenoble I/CNRS, LGGE, 54 rue Moli??re, 38402, Saint-Martin-d??H??res Cedex, France
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Abstract: | Beryllium-10 in ice provides a valuable proxy of solar activity. However, complex production pathways, atmospheric transport, and deposition processes impede its quantitative interpretation. Here, we examine the influence of deposition processes on two Be-10 ice core records from Central Antarctica (South Pole and Dome Fuji stations), covering the last millennium. We try to quantify how Be-10 variations in ice relate to variations in Be-10 production, and the bias associated to this relationship. An independent bias estimation is provided by comparing atmospheric radiocarbon variations reconstructed from tree rings and deduced from Be-10 variations. Both techniques suggest an uncertainty of the order of 10% in Be-10 production. This uncertainty estimate does not account for the geographical origin of Be-10, which remains a major issue. Because both Be-10 records are so similar, we propose to average them as a means to decrease the unshared (non solar) variability. This average record provides a new reconstruction of solar modulation parameter ?? and total solar irradiance over the last ~1,300?years. The lowest solar activity is found during the so-called Sp?rer Minimum (around AD 1450). The highest activities are found during the 8th century and over the last decades: as shown in previous studies, our results suggest that the recent solar activity is not exceptionally high for the last millennium. |
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