Paleoclimate Change and the Closed Great Lakes: Paleohydrological Sensitivity Under Higher Amplitude Conditions
Abstract
The estimation of future Great Lakes water elevations for global warming climate scenarios requires our understanding of the relationship of lake level shifts to climate change. Some scenarios, based on global circulation models, suggest the Great Lakes will be lower than suggested by historically recorded variability. (Experiments in transposition of various climates to the Great Lakes basin show that historical climate variation is relatively small.) Modest climate change could be significant; for example a Midwest US climate would lower Lake Superior by about 12 m, bringing lake levels below the outflow channel sill ("closed" lake) in 37 years. We intend to reconstruct and model past closed-lake conditions to evaluate climate-hydrology sensitivity for higher-amplitude conditions of change. We infer water levels, of tens of meters below overflow outlets, from geological evidence in the Erie and Michigan-Huron basins for a severe dry climate between about 7900 and 7000 BP. The evidence consists of elevations of C-14 dated indicators of former lake-levels such as isolation basins, abandoned strandlines, submerged tree stumps, and sediment unconformities, all corrected for glacial isostatic rebound. A new project will quantify the closed-lake event by reconstructing former topography and bathymetry with GIS technology and a digital elevation model of the Great Lakes basin. We will determine mean paleoclimatic parameters from geological, ecological, and geochemical proxies. We will develop probable paleoclimates for the transitions into and out of closed-lake conditions by shifting modern climates to fit the paleoclimatic parameters. Paleohydrological modeling will recover information about the sensitivity of the Great Lakes to climate change under high-amplitude conditions.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMGC22A..04L
- Keywords:
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- 1600 GLOBAL CHANGE;
- 1630 Impact phenomena;
- 1655 Water cycles (1836);
- 1845 Limnology;
- 4239 Limnology