| Early Pleistocene glacial cycles in marine O-18 exhibit strong obliquity pacing, but there is a perplexing lack of precession variability despite its important influence on summer insolation intensity - the presumed forcing of ice sheet growth and decay according to the Milankovitch hypothesis. This puzzle has been explained in two ways: Northern Hemisphere ice sheets instead respond to insolation integrated over the summer, which is mostly controlled by obliquity, or anti-phased precession-driven variability in ice volume between the hemispheres cancels out in global O-18, leaving the in-phase obliquity signal to dominate. We evaluated these ideas by reconstructing Laurentide Ice Sheet (LIS) meltwater discharge to the Gulf of Mexico from 2.55-1.70Ma using... |
