100-kyr ice age cycles as a timescale matching problem

Abstract. The dominant periodicity of the late Pleistocene glacial cycles is roughly 100 kyr, rather than other major astronomical periods such as 19, 23, 41, and 400 kyr. Various models explain this fact through distinct dynamical mechanisms, including synchronization of self-sustained oscillations and resonance in mono- or multi-stable systems. However, the variety of proposed models and dynamical mechanisms could obscure the essential factor for realizing the 100-kyr periodicity. We propose the hypothesis that the ice-sheet climate system responds to astronomical forcing at the ~100-kyr periodicity because the intrinsic timescale of the system is closer to 100 kyr than to other major astronomical periods. We support this idea with analyses and sensitivity studies of several simple ice age models with contrasting mechanisms.