On the Cause of the Mid‐Pleistocene Transition

• Published in: Reviews of Geophysics Vol. 59; no. 2
• Main Authors: Berends, C. J., Köhler, P., Lourens, L. J., Wal, R. S. W.
• Format: Book Review
• Language: English
• Published: 01.06.2021
• ISSN: 8755-1209; 1944-9208
• DOI: 10.1029/2020RG000727

The Mid‐Pleistocene Transition (MPT), where the Pleistocene glacial cycles changed from 41 to ∼100 kyr periodicity, is one of the most intriguing unsolved issues in the field of paleoclimatology. Over the course of over four decades of research, several different physical mechanisms have been proposed to explain the MPT, involving non‐linear feedbacks between ice sheets and the global climate, the solid Earth, ocean circulation, and the carbon cycle. Here, we review these different mechanisms, comparing how each of them relates to the others, and to the currently available observational evidence. Based on this discussion, we identify the most important gaps in our current understanding of the MPT. We discuss how new model experiments, which focus on the quantitative differences between the different physical mechanisms, could help fill these gaps. The results of those experiments could help interpret available proxy evidence, as well as new evidence that is expected to become available. Plain Language Summary For the past 1.2 million years, during the Late Pleistocene, the Earth has gone through glacial cycles (“ice ages”) of ∼120,000 years in duration. Before that, during the Early Pleistocene, glacial cycles lasted only ∼41,000 years. The cause of this change in duration (called the “Mid‐Pleistocene Transition”, or MPT) is not clear. We review the different explanations for the MPT that have been proposed by different researchers over the past few decades, comparing them to each other and to the available evidence. Key Points Different physical mechanisms have been proposed to explain the Mid‐Pleistocene Transition; all are plausible, none are certain Evidence of a Pleistocene cooling trend (required for many mechanisms to act) remains inconclusive More systematic model studies could help fill in the gaps in the current knowledge