Abrupt climate change and millennial-scale cycles: an astronomical mechanism
Abstract. Contributing to the poor understanding of abrupt climate change is the lack of a known mechanism for a ~1470-yr quasi-periodicity, leading to debates as to its existence. This oscillation is associated with the controversial Bond cycle, which has been by some as stochastic resonance, and is a harmonic resonating with Heinrich, Dansgaard-Oeschger ice-rafting debris events, as well as millennial-scale ENSO events in the Pacific. Suggestions of a solar link to the Bond cycle were made but there is no known solar periodicity of this length. Here, statistically-significant results of a comparison between TSI reconstructions based on Antarctic 10Be data and the modelled interaction of the solar and lunar cycles that produce a 1470-yr cycle are presented. These results confirm the cycle’s existence, its astronomical mechanism, and the major lunar role in the timing of all these ice-rafting debris events. The associated data show that the occurrence of Bond events coincides with maximum gravitational forcing and peak TSI, both associated with minimum Sun-Earth distance that are influenced by both the perihelion and the Moon. These findings are consistent with previous suggestions by Bond and other researchers that amplified gravitational and solar forcing may be involved. The results also indicate that the Moon’s gravitation influences patterns of cosmogenic isotopes at millennial time-scales.
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