The 10.8 years solar cycle recorded in sea sediments during the last 4000 years

The thermoluminescence (TL) and carbonate profiles are measured in shallow water Ionian Sea cores, dated precisely by radiometric and tephroanalysis methods. Their time series, covering the last 4000 years, are obtained at time intervals of 3.096 and 3.87 years. We show that the 10.8 yr cyclicity is always present in each of time series analysed. A study of the amplitudes and phases of the wave is performed by the method of superposition of epochs. The phase shift of the TL and of the CaCO3 waves is ∼π. The persistency of the wave is assured in the last 3000 years by the cyclogram analysis. The power involved in this component of the signals is however small. Since the time series which we have extracted from the Ionian Sea cores bear some relation to the climatic factors forcing the deposition of the coastal carbonatic mud, these results may be interpreted as a proof that the Schwabe cycle of the Sun, associated with the irradiance variability, is directly involved in the climatic changes of the terrestrial archives.