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TitleUsing a paleo-environmental event to better understand future climatic-hydrological impact on the Laurentian Great Lakes
AuthorLewis, C F M; Croley, T E, II; Blasco, S M; King, J W; McAndrews, J H; McCarthy, F M G; Brooks, G R; Medioli, B E; Todd, B J
SourceCanadian Quaternary Association, program and abstracts/Association canadienne pour l'étude du Quaternaire, programme et résumés; 2007 p. 113
Alt SeriesEarth Sciences Sector, Contribution Series 20070115
MeetingCanadian Quaternary Association (CANQUA) meeting; Ottawa, ON; CA; June 4-8, 2007
AreaGreat Lakes; Canada; United States of America
Subjectshydrogeology; environmental geology; Nature and Environment; water levels; lake water; environmental studies; environmental analysis; paleoenvironment; hydrologic environment; hydrologic budget; climate change
ProgramEnhancing resilience in a changing climate
AbstractThe history of the Great Lakes since their formation during the last deglaciation is, as yet, a largely unused dimension of knowledge that provides many examples of changing climate, hydrology and limnology. Evaluations of past events provide a context for understanding change in the lakes, and for validating numerical models to increase confidence in the results of future scenarios, needed for effective adaptation and management of aquatic resources. An episode of hydrological closed-basin conditions (lake levels below overflow outlets) was revealed by recent assessment of past lake-level data and differential glacial rebound. This closed-basin event, about 7900 14C BP recognized in the Huron and Michigan basins, is the impact of dry early Holocene climate on the lake system, once it was isolated from water supply by glacial meltwater. The scientific objective is to determine the relationship between climate and hydrology for this event (i.e. sensitivity of water levels to climate change) which is a key parameter for modelling future water levels under projected climatic scenarios. Current progress consists of 1) validation of the Great Lakes lowstand through investigations in the French River-North Bay area, Lake Simcoe basin and in other lake basins, 2) paleoclimatic estimation based on existing records, and 3) exploratory climatic-hydrologic modelling. Paleoclimatic reconstructions based on the pollen record suggest that northern Minnesota is a good modern analog for the Georgian Bay region during the early Holocene. Existing pollen profiles from about 20 small lakes were subjected to pollen-climate transfer function analysis which yielded mean July and January temperatures and mean annual precipitation. Most showed a convergence of higher temperatures with lower precipitation than present with most droughty conditions on the western side of the Great Lakes basin. Exploratory modelling through collaboration with NOAA and use of their high-resolution hydrological model of the Great Lakes basin shows that warmer and drier climates relative to the present climate might close the lakes, e.g. a 3ºC rise with accompanying drops in precipitation ranging from 37 % to 61 %. Future modelling will consider the climatic-hydrologic effects of early Holocene insolation, wind-fields, and paleogeography which have not yet been incorporated.