THE IMPACT OF GLACIAL LAKE RUNOFF ON THE GOLDTHWAIT AND CHAMPLAIN SEAS - THE RELATIONSHIP BETWEEN GLACIAL LAKE AGASSIZ RUNOFF AND THE YOUNGER DRYAS

The freshwater flux to the North Atlantic Ocean during the last deglaciation included runoff (meltwater plus precipitation) from glacial Lake St Lawrence (ca. 11.6 ka BP), from glacial Lake Agassiz (10.9-9.9 and 9.5-8.0 ka BP) and from glacial Lake Barlow-Ojibway (9.5-8.0 ka BP). Runoff from the glacial lakes does not appear to have mixed with the deep water of the Goldthwait Sea in the Gulf of St Lawrence and was part of the surface outflow to the North Atlantic Ocean. Radiocarbon-dated invertebrate faunal assemblages show that the major impact of Lake Agassiz runoff to the North Atlantic Ocean during the 10.9 to 9.9 ka BP interval occurred after 10.5 ka BP, resulting in the freshening of the Champlain Sea. The Younger Dryas cold episode, on the other hand, began about 11.0 ka BP. The discordance between the major impact of Lake Agassiz runoff on the Champlain Sea and the beginning of the cold episode indicates that Lake Agassiz runoff did not trigger the Younger Dryas cooling. However, the runoff from glacial Lake Agassiz may have sustained the cold climate during the latter part of the Younger Dryas cold episode.