1. Meteorological Service of Canada, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4, Department of Geography, University of Toronto, Toronto, Ontario, Canada M5S 3G3, Département de Géologie, UMR CNRS 6143, Faculté des Sciences et Techniques, Université de Rouen, France, and Freshwater Institute, Fisheries and Oceans Canada, Winnipeg, Manitoba, Canada R3T 2N6