# Southern Hemisphere initiation of the mid-Pleistocene transition

## TL;DR

The mid-Pleistocene climate shift was likely triggered by Antarctic ice growth, not Northern Hemisphere processes.

## Contribution

New evidence shows Southern Hemisphere ice dynamics initiated the mid-Pleistocene transition.

## Key findings

- Antarctic ice sheet growth primed the climate system for the MPT.
- Buoyancy redistribution from icebergs reduced Northern Hemisphere deep water formation.
- Southern Hemisphere processes initiated the MPT, followed by Northern Hemisphere climatic dominance.

## Abstract

The mid-Pleistocene transition [MPT; between ~1.25 and 0.7 million years ago (Ma)] marks when Earth’s glacial pacing switched from 41,000- to 100,000-year cyclicity. Here, we present a South Pacific hydrogenous neodymium isotope record tracking changes in deep ocean circulation spanning 1.5 to 0.5 Ma. This record indicates that the MPT was not triggered by Northern Hemisphere (NH) processes. Instead, the growth of Antarctic ice sheets to a critical size (~1.8 Ma) primed the climate system for the MPT, with iceberg release and melting transferring buoyancy out of the Southern Ocean. This iceberg-associated buoyancy redistribution ultimately reduced deep water formation in the NH, an observation supported by our data. Once the MPT was initiated in the Southern Hemisphere, its subsequent climatic changes were dominated by NH processes.

A South Pacific neodymium isotope time series suggests Antarctic ice sheet growth triggered the mid-Pleistocene transition.