Atmospheric <sup>81</sup>Kr as an Integrator of Cosmic‐Ray Flux on the Hundred‐Thousand‐Year Time Scale
Jake Zappala, Daniel Baggenstos, Christoph Gerber, Wei Jiang, B. Mack Kennedy, Zheng‐Tian Lu, J. Masarik, Peter Mueller, Roland Purtschert, Ate Visser
Abstract
Abstract The atmospheric abundance of 81 Kr is a global integrator of cosmic rays. It is insensitive to climate shifts, geographical variations, and short‐term solar cycle activity, making it an ideal standard to test models of cosmic‐ray flux on the time scale of 10 5 years. Here we present the first calculation of absolute 81 Kr production rates in the atmosphere, and a measurement of the atmospheric 81 Kr/Kr abundance via the Atom Trap Trace Analysis method. The measurement result significantly deviates from previously reported values. The agreement between measurement and model prediction supports the current understanding of the production mechanisms. Additionally, the calculated 81 Kr atmospheric inventory over the past 1.5 Myr provides a more accurate input function for radiokrypton dating.