The Milankovitch theory states that the orbital eccentricity, precession, andobliquity of the Earth influence our climate by modulating the summerinsolation at high latitudes in the northern hemisphere. Despite considerablesuccess of this theory in explaining climate change over the Pleistocene epoch(2.6 to 0.01 Myr ago), it is inconclusive with regard to which combination oforbital elements paced the 100 kyr glacial-interglacial cycles over the latePleistocene. Here we explore the role of the orbital elements in pacing thePleistocene deglaciations by modeling ice-volume variations in a Bayesianapproach. When comparing models, this approach takes into account theuncertainties in the data as well as the different degrees of model complexity.We find that the Earth's obliquity (axial tilt) plays a dominant role in pacingthe glacial cycles over the whole Pleistocene, while precession only becomesimportant in pacing major deglaciations after the transition of the dominantperiod from 41 kyr to 100 kyr (the mid-Pleistocene transition). We also findthat geomagnetic field and orbital inclination variations are unlikely to havepaced the Pleistocene deglaciations. We estimate that the mid-Pleistocenetransition took place over a 220 kyr interval centered on a time 715 kyr ago,although the data permit a range of 600--1000 kyr. This transition, occurringwithin just two 100\,kyr cycles, indicates a relatively rapid change in theclimate response to insolation.
展开▼
