Global Beryllium-7 Dynamics: Nonlinear Scaling Properties, Spatial Classification, and Sensitivity to Atmospheric Teleconnections

This study investigated the complex temporal behavior of cosmogenic Beryllium-7 (7Be) by analyzing daily activity concentrations from 21 monitoring stations in the CTBTO network, spanning the years 2010 through 2017. By applying multifractal detrended fluctuation analysis (MF-DFA), it was established that 7Be time series exhibit significant nonlinear scaling behaviors. The results indicate a broad multifractal spectrum (Δα ranging from 0.17 to 0.66), with statistically significant multifractality observed at all locations except RN45 and RN47. Leveraging the extracted spectral width and Hölder exponents, current study utilized the K-means algorithm to categorize the global stations into three distinct clusters based on their dynamic signatures. Furthermore, this study assessed the external forcing of 7Be variations via multifractal cross-correlation analysis against five major indices: the Southern Oscillation Index (SOI), North Atlantic Oscillation (NAO), and solar activity markers (Total, Northern, and Southern hemisphere sunspot numbers). While cross-correlations varied across indices, the NAO emerged as the dominant driver. Notably, station RN16 (Yellowknife, Canada) displayed the highest sensitivity to these external drivers, suggesting a unique coupling between atmospheric/solar indices and isotope concentration at this latitude.