Cosmogenic radiosulfur tracking of solar activity and the strong and long-lasting El Niño events.

Reconstruction of past solar activity or high-energy events of our space environment using cosmogenic radionuclides allows evaluation of their intensities, frequencies, and potential damages to humans in near space, modern satellite technologies, and ecosystems. This approach is limited by our understanding of cosmogenic radionuclide production, transformation, and transport in the atmosphere. Cosmogenic radiosulfur ( 35 S) provides additional insights due to its ideal half-life (87.4 d), extensively studied atmospheric chemistry (gas and solid), and ubiquitous nature. Here, we report multiyear measurements of atmospheric 35 S and show the sensitivity of 35 S in tracking solar activity in Solar Cycle 24 and regional atmospheric circulation changes during the 2015/2016 El Niño. Incorporating 35 S into a universal cosmogenic radionuclide model as an independent parameter facilitates better modeling of production and transport of other long-lived radionuclides with different atmospheric chemistries used for reconstructing past astronomical, geomagnetic, and climatic events.