In this study, temporal and spatial variability of ice cover in the Great Lakes are investigated using historical satellite measurements from 1973 to 2010. The seasonal cycle of ice cover was constructed for all the lakes, including Lake St. Clair. A unique feature found in the seasonal cycle is that the standard deviations (i.e., variability) of ice cover are larger than the climatological means for each lake. This indicates that Great Lakes ice cover experiences large variability in response to predominant natural climate forcing and has poor predictability. Spectral analysis shows that lake ice has both quasi-decadal and interannual periodicities of ~8 and ~4 yr. There was a significant downward trend in ice coverage from 1973 to the present for all of the lakes, with Lake Ontario having the largest, and Lakes Erie and St. Clair having the smallest. The translated total loss in lake ice over the entire 38-yr record varies from 37% in Lake St. Clair (least) to 88% in Lake Ontario (most). The total loss for overall Great Lakes ice coverage is 71%, while Lake Superior places second with a 79% loss. An empirical orthogonal function analysis indicates that a major response of ice cover to atmospheric forcing is in phase in all six lakes, accounting for 80.8% of the total variance. The second mode shows an out-of-phase spatial variability between the upper and lower lakes, accounting for 10.7% of the total variance. The regression of the first EOF-mode time series to sea level pressure, surface air temperature, and surface wind shows that lake ice mainly responds to the combined Arctic Oscillation and El Niño–Southern Oscillation patterns.

A review of the current state of knowledge on climate change due to an ’enhanced greenhouse effect’ and the response of the climate and hydrologic systems to a changing atmosphere is provided. In particular, the survey presents historic trends in and the impacts of climate change on temperature, precipitation, evapotranspiration, runoff and Great Lakes levels. While much of the impacts research in the Great Lakes-St. Lawrence basin has used equilibrium 2 × CO2 scenarios, the transient scenarios for 2030 and 2050 from the Canadian Centre for Climate Modelling and Analysis and the United Kingdom Hadley Centre coupled atmosphere-ocean global circulation models are also described. If the significant declines in runoff and lakes levels suggested by climate change scenarios are realized, there could be serious supply-demand mismatches and water allocation issues. The issue of climate change reinforces the need for continued cooperative planning and management of the water resources of the Great Lakes-St. Lawren... Cet article offre un survol de l’état actuel de la connaissance sur le changement climatique attribuable à un «effet de serre accru» et de la réaction du climat et des systèmes hydrologiques à une atmosphère changeante. En particulier, l’étude présente les tendances historiques des impacts du changement climatique sur la température, les précipitations, l’évapotranspiration, les écoulements et les niveaux des Grands Lacs. Bien qu’une grande partie de la recherche sur les impacts dans le bassin des Grands Lacs et du Saint-Laurent repose sur des scénarios 2 × CO2 d’équilibre, l’article décrit aussi les scénarios transitoires pour 2030 et 2050 des modèles couplés de circulation générale atmosphère-océan du Centre canadien de la modélisation et de l’analyse climatique et du Centre Hadley du Royaume-Uni. Si les déclins considérables dans les écoulements et les niveaux des lacs que suggèrent les scénarios de changement climatique venaient à se produire, cela pourrait alors se traduire par de graves écarts entre...