Changes in the bathymetry and volume of glacial Lake Agassiz between 11,000 and 9300 14C yr BP

The volume and surface area of glacial Lake Agassiz varied considerably during its 4000-year history. Computer models for seven stages of Lake Agassiz were used to quantify these variations over the lake's early history, between about 11,000 and 9300 C-14 yr B.P. (ca. 13,000 to 10,300 cal yr B.P.). Just after formation of the Herman strandlines (ca. 11,000 C-14 yr B.P.), the volume of Lake Agassiz appears to have decreased by >85% as a consequence of the abrupt rerouting of overflow to its eastern outlet from its southward routing into the Mississippi River basin. This drainage released about 9500 km(2) of water into the North Atlantic Ocean via the Great Lakes and Gulf of St. Lawrence. Following closure of this eastern routing of overflow, the lake reached its maximum size at about 9400 C-14 yr B.P. with an area of >260,000 km(2) and a volume of >22,700 km(3). A second major reduction in volume occurred shortly after that, when its volume decreased >10% following the opening of the Kaiashk outlet to the east into the Great Lakes, and 2500-7000 km(3) of water was released into the North Atlantic Ocean. These discharges may have affected ocean circulation and North Atlantic Deep Water production. (C) 2000 University of Washington.