North Atlantic climatic oscillations revealed by deep Greenland ice cores

Five long-term oxygen isotope (δ) records along ice cores are discussed, in particular two from the Greenland ice sheet that exhibit persistent δ oscillations with a quasi-periodicity of ca. 2550 years. A detailed study of the δ cycles in the Wisconsin glaciation show that they cannot be ascribed to discontinuities in the cores, nor to ice-dynamic instabilities in the ice sheet. In the Holocene, the δ cycles are less pronounced, but they are concurrent with the fluctuating glacier extention elsewhere, which substantiates their climatic significance. An anti-correlation with 14C concentration in atmospheric CO2, and with 10Be deposition rates on the ice sheets, suggests a connection between climate and solar processes, but a conclusion on this point must await clarification of the terrestrial circulation and mixing processes, and the relationship between the solar outputs of radiation and particulate matter.