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 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.