Distinct roles for precession, obliquity and eccentricity in 100kyr glacial cycles

Attempts to discriminate between the specific roles of precession, obliquity and eccentricity in glacial/interglacial transitions have been hindered by imprecise age control. We circumvent this problem by focussing on the morphology of deglaciation/termination, which we show depends strongly on the relative phasing of precession versus obliquity. We demonstrate that while both parameters are important, precession has more influence on deglacial onset, while obliquity is more important for attainment of peak interglacial conditions and glacial inception. We find that the set of precession peaks responsible for terminations since 0.9Ma is a subset of those ‘candidate peaks’ which begin while obliquity is increasing. Specifically, termination occurs with the first candidate peak following a minimum in eccentricity. Thus the gross morphology of 100kyr glacial cycles appears largely deterministic.