High-resolution records of ¹⁰Be in endogenic travertine from Baishuitai, China: A new proxy record of annual solar activity?

The accurate reconstruction of past solar activity is a prerequisite for assessing the role of solar forcing on climate variations. Cosmogenic ¹⁰Be, produced by galactic cosmic rays and stored in natural archives such as ice cores and lake sediments, has been shown to be the most reliable as an indicator of past solar activity, although reconstructions at a higher, annual, resolution have remained elusive due to dating imprecision and uncertainties concerning the effect of depositional processes. Here, we employ a methodology that facilitates the annual reconstruction of past cosmic-ray and solar activity variations. An annual ¹⁰Be record is assembled from an endogenic travertine in Baishuitai, China, covering the period 2001–2016 CE. We demonstrate that the effect of depositional processes when ¹⁰Be is incorporated into travertine can be accounted for using the associated ⁹Be and potassium (K) contents, and that the resulting corrected ¹⁰Be content significantly correlates with the modeled global ¹⁰Be production rates with a time lag of 1.5–2.5 years. Our results from the Baishuitai endogenic travertine suggest that the ¹⁰Be record in such carbonate sediments has considerable potential as a high resolution proxy for past cosmic-ray and solar activity variations.