Heinrich events

Heinrich events are massive, episodic discharges of icebergs from the Laurentide Ice Sheet into the North Atlantic Ocean, identified by layers of ice-rafted debris in marine sediment cores. These events represent catastrophic instability in a continental ice sheet — not gradual melting but abrupt collapse — and each event released enough freshwater to disrupt North Atlantic deep water formation and trigger hemispheric cooling.

Heinrich events demonstrate that ice sheets are not passive responders to climate but active dynamical systems capable of internal oscillations driven by basal hydrology, ice stream dynamics, and calving feedbacks. They are closely related to Dansgaard-Oeschger events and the Younger Dryas, forming a family of abrupt transitions that characterize the last glacial period. See Abrupt Climate Change.