The pacemaker always rings twice

Abstract

We generated new, long, high-resolution, climate proxy records from Deep Sea Drilling Project (DSDP) Sites 607 and 609 in the subpolar North Atlantic over the interval 225-970 ka, which have pronounced variability at periods <19 kyr, shorter than any solar forcing due to Earth's changing orbital parameters. This high-frequency variability results from a transfer of variance from primary orbital frequencies (1/23, 1/40 kyr). Previous work suggesting that high-frequency climate variability in the region may be paced by variations in tropical Atlantic climate or by insolation forcing at low latitudes is not supported by comparison of our records with either records of dust and CaCO 3 accumulation at Ocean Drilling Program (ODP) Site 663 in the subtropical Atlantic or with time series of equatorial insolation. Rather the majority of suborbital scale (1/19 kyr > f > 1/7 kyr) variance in our North Atlantic climate proxy records is shown, using bispectral and cross-bispectral methods, to be explainable as harmonics and/or combination tones of orbital-scale climatic variability of the North Atlantic region itself. Thus the timing and amplitude of high-frequency climate change in the North Atlantic region appears to be a nonlinear function of variations in high-latitude climate at Milankovitch frequencies.