Late Pleistocene 100-Kyr Glacial Cycles Paced by Precession Forcing of Summer Insolation

Climate variability over the past 800,000 years has long been described as being dominated by ~100-kyr glacial cycles, and researchers have debated whether these glacial cycles were driven by Earth’s orbital cycles of eccentricity, obliquity and precession. Some recent studies have suggested that these ~100-kyr glacial cycles are best characterized as groupings of two or three 41-kyr obliquity cycles; however, age uncertainties have made it difficult to distinguish whether the dramatic changes in ice-sheet size were more associated with 41-kyr obliquity or ~23-kyr precession cycles. We compare the impacts of obliquity and precession on glacial cycles using improved age estimates to analyse orbital phases during the onset of glacial terminations. Terminations are dated using a 640-kyr multiproxy stack of eight North Atlantic benthic δ 18 O records with well-constrained probabilistic age estimates derived from correlating North Atlantic ice-rafted debris to instances of abrupt Asian monsoon variability in high-resolution 230 Th-dated speleothems. Rayleigh’s R statistics for the precession and obliquity phases of terminations demonstrate that, although both have statistically significant effects, the precession phase is more predictive of termination onset, particularly for the largest events. Thus, we conclude that Late Pleistocene ice sheets were sensitive to the precession forcing of Northern Hemisphere summer insolation intensity.