ABSTRACT: Digital reconstruction of the Paleo-Laurentian Great Lakes.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Ten colour-shaded relief maps of paleogeography in this poster show how water surface elevations and shorelines of the paleo-Great Lakes changed with time since 11.3 ka. The reconstructions were motivated by paleoclimatic research of the Younger Dryas cool interval dependent, in part, on the modelling and estimation of meltwater flow through the paleo-Great Lakes to the North Atlantic Ocean (Moore et al. 2000. Paleoceanography 15, 4-18). Land drainage area outside of ice margins, lake area, and lake volume for each major basin, required for the flow modelling, were obtained by use of an ArcInfo geographic information system. For each reconstruction, a 30-arc second digital terrain model (DTM) of the former ground surface was derived by backtilting a DTM of present topography to remove the effects of differential glacio-isostatic rebound based on the evidence of upwarped glacial lake shorelines. Reconstruction of the former Great Lakes, since retreat of the Laurentide Ice Sheet is mostly dependent on evidence and interpretation of changing lake outlets and major inflows from other lakes along the ice margin. The water balance for all reconstructed phases was assumed to be positive such that lakes always overflowed their outlets. Lake water filled basins and overflowed the lowest outlets over their basin=s rim. Lake drainage and lake elevation switched to lower or higher outlets when impounding ice margins retreated or advanced. Erosion of outlets lowered lake surfaces. Lakes were raised or lowered by increased or decreased flow through relatively narrow deep outlets. Since 11.3 ka, the total water surface area of the Great Lakes ranged from 19 % larger to 59 % smaller than their present area.

Bibliography of Canadian Geomorphology