The CaCO₃ profile in a recent Ionian sea core and the tree ring radiocarbon record over the last two millennia

Abstract

The calcium carbonate (CaCO₃) profile of a recent sediment core, drilled in the Ionian Sea in 1979, is studied. The CaCO₃ content of the sediment has been measured at regularly spaced intervals of Δd = 0.25 cm corresponding to δt = 3.87 yr from AD 170 to the present. The CaCO₃ profile of the core closely resembles the radiocarbon time series as deduced from tree ring data. The two records have a correlation coefficient of about 0.8 and show strikingly similar long-term variations. This result presumably follows from the fact that both systems take part in the carbon cycle. The spectral analysis of the CaCO₃ time series reveals the presence of the well known periodicity with period ca ¦200 years, characteristic of the Δ¹⁴C record. Since the CaCO₃ content of sea sediments is governed by biological, physical and chemical processes in surface sea waters, which in turn are strongly influenced by climatic conditions, and since the ≈ 200 yr Δ^l4C wave is known to be governed by solar modulation of galactic cosmic rays, the tuning of these two records on the same frequencies suggests a strong sun-climate relationship.