The Mid-Pleistocene Climate Transition

Abstract

The timing of ice ages over the past ∼2,600 thousand years (kyr) follows pacing by cyclical changes in three aspects of Earth's orbit that influence the solar energy received as a function of latitude and season. Explaining the large magnitude of the climate changes is challenging, particularly so across the period of time from ∼1,250 to 750 ka—the Mid-Pleistocene Transition or MPT. The average repeat time of ice age cycles changed from an earlier 41-kyr rhythm to longer and more intense glaciations at a spacing of about 100 kyr. Explaining this change is very difficult because there was no corresponding change in the orbital pacing that would trigger a change in timing. While the first generation of hypotheses looked largely to changes in the behavior of Northern Hemisphere ice sheets, more recent work integrates ice behavior with new data capturing the evolution of other important aspects of past climate. A full explanation is still lacking, but attention increasingly focuses on the ocean carbon cycle and atmospheric CO2 levels as the crucial agents involved in the MPT. ▪ The pattern of climate changes connected to the ice ages of the past few million years changed radically between about 1,250 and 750 thousand years ago, a time known as the Mid-Pleistocene Transition or MPT. ▪ While the glacial cycles were ultimately triggered by cyclical changes in Earth's orbit, the changes across the MPT came from changes in the Earth system itself, most likely in the form of a change in the carbon cycle. ▪ The dramatic change in many essential aspects of climate—ice volume, temperature, rainfall on land, and many others—in the absence of an external change suggests how important feedbacks are to the climate system. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 51 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Drastic changes in Depositional Environments at the Ross Sea Continental Margin since the Mid-Pleistocene: More evidence for West Antarctic Ice Sheet collapse

“…This interval belongs to the later part of the MPT, characterized by extended glacial conditions (Fig. 5c) (Clark et al, 2006;Bol'Shakov, 2015;Daruka and Ditlevsen, 2016;Herbert, 2023). This period signifies a sudden reorganization of the climate system, occurring in at least two discernible stages, i.e., MIS 25-22 and MIS 22-16.…”

The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene

“…There is, in fact, little support for such a scenario. Overall, Earth has had the same climate regime during the last ~1 million years, since the shift to deep, long (~100 kyr) glacial-interglacial cycles with the Mid-Pleistocene Climate Transition (Clark et al, 2006;Herbert, 2023). Maximal Pleistocene ice sheet cover in the Northern Hemisphere was attained during multiple Middle Pleistocene glaciations rather than during the last glacial cycle (Batchelor et al, 2019).…”

Planktonic foraminiferal assemblages as tracers of paleoceanographic changes within the Northern Benguela current system since the Early Pleistocene

“…This period in the Benguela region was characterized by higher SST variations linked to 41-kyr obliquity cycles as well as the increase of the meridional thermal gradient, which led to the intensification of the upwelling phases (Christensen and Giraudeau, 2002;Etourneau et al, 2009;Martinez-Garcia et al, 2010;Rosell-Melé et al, 2014) and the alternation of possible Benguela Niño/Niña conditions. The highest amplitude of SST glacial-interglacial variability was recorded during the Early-Middle Pleistocene Transition (EMPT), a period between 1.4 and 0.4 Ma, during which a switch from 41-kyr to 100-kyr orbital cycle occurred (Berger and Jansen, 1994;Head and Gibbard, 2015;Herbert, 2023). The planktonic foraminiferal dataset for Hole U1575A and U1576A detected phases of southward/northward shifts of the ABF (up to 24°35´ S), within part of the studied stratigraphic sequence corresponding to the EMPT (Fig.…”

“…Several studies suggested the occurrence of Benguela Niño/Niña events during the Pliocene-Pleistocene time intervals (e.g., Ufkes and Kroon, 2012;Rosell-Melé et al, 2014). Particularly, since the onset of the Early-Middle Pleistocene Transition (EMPT), a strong glacial-interglacial sea surface temperature (SST) variability occurred, possibly promoting the development of Benguela Niño/Niña conditions (Herbert, 2023).…”