Revealing a Solar Cycle Resonance through tree-rings

Résumé

Abstract Tree-ring data is one of the best proxy sources for studying the dynamics of the Earth’s climate system. However, paleoclimatic studies often face multiple problems that can influence the quality of the obtained information. The success in analyzing these proxies is thus crucial for understanding the nature of these dynamics. Here we introduce a new data-driven approach that facilitates the detection and extraction of cyclic components from tree-ring time series. To this end, we firstly tested this approach on artificial time series then we applied it on over 6000 tree-ring time series collected from 242 sites and 66 tree-species around the world. Based on the use of the autocorrelation functon(ACF) analysis and a consecutive filtering, the decomposition of the tree-ring time series revealed the existence of 8 harmonic modes (HMs) of cyclicity. We found that cyclicity inherent in tree-ring time series follows two resonance processes. Furthermore, an assumption model explaining the relationship between these different harmonic modes and which corroborated well with the extracted cycles was also introduced. The consistency of the achieved data among the widely separated sites as well as the spectacular accuracy of our findings compared to different studies give evidence to assign these 8 HMs as a truly global signature. Our analysis suggests that this global signature is related to the resonance of the solar activity given the very close relationship found between these HMs and the solar cycle. The resonance process, demonstrated by our study could be of great importance for earth-climate system and solar dynamo theories.

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