New research shows that shifting Antarctic circulation after the last Ice Age released ancient deep-ocean carbon into the atmosphere. Using Southern Ocean sediment cores, scientists traced how expanding Antarctic Bottom Water mixed long-isolated, carbon-rich waters upward. The findings reveal a major but underappreciated driver of early Holocene warming.New research shows that shifting Antarctic circulation after the last Ice Age released ancient deep-ocean carbon into the atmosphere. Using Southern Ocean sediment cores, scientists traced how expanding Antarctic Bottom Water mixed long-isolated, carbon-rich waters upward. The findings reveal a major but underappreciated driver of early Holocene warming.