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The influence of the Laurentian Great Lakes on the climate of surrounding regions is significant, especially in leeward settings where lake-effect snowfall occurs. Heavy lake-effect snow represents a potential natural hazard and plays important roles in winter recreational activities, agriculture, and regional hydrology. Changes in lake-effect snowfall may represent a regional-scale manifestation of hemispheric-scale climate change, such as that associated with global warming. This study examines records of snowfall from several lake-effect and non-lake-effect sites throughout most of the twentieth century in order to 1) determine whether differences in snowfall trends exist between these settings and 2) offer possible linkages between lake-effect snow trends and records of air temperature, water temperature, and ice cover. A new, historic record of oxygen isotope [␦ 18 O ] data from the sediments of three eastern Finger Lakes in central New York is presented as a means (CaCO ) 3 of independently assessing changes in Great Lakes lake-effect snowfall. Results reveal a statistically significant increasing trend in snowfall for the lake-effect sites, whereas no trend is observed in the non-lake-effect settings. The Finger Lake oxygen isotope record reflects this increase in lake-effect snow through a statistically significant trend toward lower ␦ 18 O values. Records of air temperature, water temperature, and lake ice suggest that (CaCO ) 3 the observed lake-effect snow increase during the twentieth century may be the result of warmer Great Lakes surface waters and decreased ice cover, both of which are consistent with the historic upward trend in Northern Hemispheric temperature due to global warming. Given projected increases in future global temperature, areas downwind of the Great Lakes may experience increased lake-effect snowfall for the foreseeable future.

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