Editor’s summary

The mid-Pleistocene transition (MPT), approximately 1.25 to 0.85 million years ago, was a period during which the glacial cycle changed from 41,000 years to 100,000 years in duration. It is widely believed that the cause of the MPT was a slowdown of deep ocean circulation punctuated by a collapse at about 0.90 million years ago. Hines et al. found no evidence of a dramatic change in deep ocean circulation over the MPT, only modest ocean circulation adjustments. Their data also illustrate how the deep ocean is able to sequester carbon dioxide without substantial changes in circulation geometry. —Jesse Smith

Abstract

The mid-Pleistocene transition (MPT) [~1.25 to 0.85 million years ago (Ma)] marks a shift in the character of glacial-interglacial climate (1, 2). One prevailing hypothesis for the origin of the MPT is that glacial deep ocean circulation fundamentally changed, marked by a circulation “crisis” at ~0.90 Ma (marine isotope stages 24 to 22) (3). Using high-resolution paired neodymium, carbon, and oxygen isotope data from the South Atlantic Ocean (Cape Basin) across the MPT, we find no evidence of a substantial change in deep ocean circulation. Before and during the early MPT (~1.30 to 1.12 Ma), the glacial deep ocean variability closely resembled that of the most recent glacial cycle. The carbon storage facilitated by developing deep ocean stratification across the MPT required only modest circulation adjustments.