Evidence for a Northern Hemispheric trigger of the 100,000-y glacial cyclicity

Significance Causes of the Mid-Pleistocene Transition (MPT) from 41- to 100-ky interglacial–glacial cyclicity are debated because it occurred without changes in solar forcing, thus indicating internal climatic drivers. This study reconstructs the deep Atlantic Ocean water-mass structure through the MPT using neodymium isotopes and distinguishes Northern and Southern Hemisphere precursors. North Atlantic results document changes in glacial erosion/weathering preceding the cyclicity shift, including a major erosional episode just before a global ocean circulation weakening between ∽950–860 ka. The findings indicate changes in Northern Hemispheric ice sheets prior to that weakening were central in shaping the cyclicity shift and the post-MPT glacial climate, whereby removal of weathered material exposed crystalline bedrock, resulting in increased bedrock–ice friction that facilitated larger ice sheets.