Depth and orbital tuning : a new chronology of glaciation and nonlinear orbital climate change

Abstract

It is suggested that orbital tuning casts a false light upon the chronology of glaciation and the understanding of the climatic response to orbital variations. By developing a new age-model, independent of orbital assumptions, a significant non-linear response to orbital forcing becomes evident in the [delta] 18 0 record. The new age-model also indicates glacial terminations two through eight are 8,000 years older than the orbitally based estimates. A simple obliquity threshold model is presented which reproduces the timing, amplitude, and observed non-linearities of the [delta] 18 0 record; and supports the plausibility of the new age-model and the inferred non-linear climatic response.