8.2-Kiloyear Event

The 8.2-kiloyear event was an abrupt cooling of global temperatures that began about 8,200 years ago and lasted two to four centuries, marking the start of the Northgrippian stage of the Holocene epoch. It was triggered when the glacial lakes Ojibway and Agassiz, dammed by the collapsing Laurentide Ice Sheet in northeastern North America, suddenly drained into the North Atlantic Ocean, disrupting ocean circulation. Greenland ice cores show cooling of 3.3 degrees Celsius below the decadal average within less than 20 years, tropical coral records from Indonesia show roughly 3 degrees of cooling, and atmospheric methane fell by about 80 parts per billion, a 15 percent drop, as the event's effects spread across multiple continents.