Map of where the Glacial Lake Agassiz was located in North America. The Glacial Lake Agassiz covered much of the Canadian province of Manitoba, extending into Saskatchewan and Ontario, and south into North Dakota and Minnesota.

Credit: Minnesota River Basin Data Center

A deluge of fresh water from glacial Lake Agassiz, flowing into the North Atlantic via the Great Lakes and the St. Lawrence Seaway, may have triggered the cold climate during the Younger Dryas time, about 1200 years ago.