The Solar Component of the Atmospheric ¹⁴C Record

Abstract

Heliomagnetic modulation of the cosmic ray flux causes variations in annual ¹⁴C production during the 11 yr solar cycle. Sunspot, auroral, and ¹⁰Be records suggest that century type ¹⁴C oscillations are also primarily influenced by the sun rather than climate. The history of decadal and bi-decadal ¹⁴C production rates during the past 9700 years, as derived from the ¹⁴C content in tree-rings using a carbon reservoir model, indicates at least two recurring patterns of solar change. Increases in ¹⁴C production rate that peak at 30% and last ca. 280 years (“Spörer types”) are repeated 8 times at irregular intervals while similar fluctuations that last only ca. 200 years (“Maunder types”) are found 9 times. The decadal and bi-decadal records of atmospheric Δ¹⁴C and model-derived ¹⁴C production rates, with long-term trend removed, are displayed in 1000 yr intervals.