Exploring the structure of the mid-Pleistocene revolution with advanced methods of time-series analysis

Abstract

 The mid-Pleistocene climate transition is a complex global change leading to Late Pleistocene ice ages with increased mean ice volume and dominant 100-ka cycle. A thorough understanding of this transition demands quantitative investigations in the time and frequency domains, and in the “stochastic domain”. Three methods of time-series analysis are presented which have been adapted for this purpose. They are tested by means of predefined, artificial time series and applied to benthic oxygen isotope (δ¹⁸O) records which serve as ice volume indicator. Results are as follows: (a) The time-dependent mean shows an increase of 0.35‰ vs PDB from 942 to 892 ka. (b) Evolutionary spectral analysis reveals an abrupt increase of 100-ka cycle amplitude at approximately 650 ka. (c) Probability density function exhibits a bifurcation behavior at approximately 725 ka. These findings point to a multiple transition from a more linear climate system to a strong nonlinear system. The significant lead of the transition in mean, in relation to the 100-ka amplitude change and bifurcation is left open for explanation.