Evidence of 550-year and 1000-year cyclicities in North Atlantic circulation patterns during the Holocene

Sedimentological colour data obtained from North Atlantic deep-sea sediment core NEAP15K provide a continuous climate record for the last 11500 yr with a mean sampling interval of 515 yr. Variations in sediment lightness, a proxy for changes in North Atlantic Deep Water (NADW) circulation, are characterized by high-frequency fluctuations with periodicities equivalent to 550 and 1000 yr, as well as a approximate to 1600-yr cyclicity comparable to that reported in other studies of Holocene climate. Cross-spectral analysis suggests that the 550-yr and 1000-yr cyclical variations in NADW circulation were coherent with fluctuations in atmospheric conditions over Greenland, where both these periodicities have been identified previously in the Holocene GISP2 delta(18)O record (Stuiver et al., 1995). A similar statistical comparison provides evidence that high-frequency (550-yr) variability in NADW circulation patterns may have been linked to short-term variations in atmospheric C-14 values during the Holocene. In general, NADW production was lower and C-14 levels were higher when colder climatic conditions prevailed. These results imply that the pattern of NADW production has been a significant factor affecting centennial- to millennial-scale Holocene climate variability in the North Atlantic region.