A Model of the Ice Age Cycle

Abstract

Time series analyses of the δ18O signal in deep sea sedimentary cores have very clearly established that ice volume fluctuations throughout the late Pleistocene have been dominated by an almost periodic oscillation with a characteristic time-scale of 105 years. Although statistically significant variance is also found at the expected Milankovitch periods corresponding to the precession of the equinoxes and to the variation of orbital obliquity, the dominance of the 105 year signal has been difficult to understand because the strength of the astronomical forcing at this period is negligibly small. The analysis presented here shows that this period arises naturally in a new model which includes the nonlinearity due to ice sheet flow and a more accurate description of the process of glacial isostatic adjustment than has been employed previously.