Changing climatic response: a conceptual model for glacial cycles and the Mid-Pleistocene Transition

摘要: Abstract. Milankovitch's astronomical theory of glacial cycles, attributing ice age climate oscillations to orbital changes in Northern Northern-Hemisphere insolation, is challenged by the paleoclimatic record. The climatic response variations insolation far from trivial. In general cycles are highly asymmetric time, with slow cooling interglacials glacials (inceptions) and very rapid warming (terminations). We shall refer this fast-slow dynamics as "saw-tooth" shape This non-linearly related time-symmetric forcing. However, most pronounced challenge Milankovitch Mid-Pleistocene Transition (MPT) occurring about one million years ago. During that event, prevailing 41 kyr corresponding almost harmonic obliquity cycle were replaced longer saw-tooth shaped a time scale around 100 kyr. MPT must have been driven internal response, since it does not correspond any apparent order identify possible mechanisms causing observed dynamics, relevant study simplified models capability generating temporal behavior similar records. present simple oscillator type model approach, two variables, temperature anomaly an volume analogous, memory term. generalization albedo feedback included terms effective multiplicative coupling between latter term (representing degrees freedom) external drive. reproduces asymmetry late Pleistocene suggests can be explained regime shift, aided noise, period 1 frequency locking 2–3 same cycle. change has suggested result gradual decrease atmospheric greenhouse gas concentration. presence chaos (non-autonomous) critical dependence on initial conditions raises fundamental questions predictability.