Cold water and high ice cover on Great Lakes in Spring 2014

Very cold temperatures across much of North America caused by the recent anomalous meridional upper air flow - commonly referred to in the public media as a polar vortex (for details, see Blackmon et al. [1977] and National Climatic Data Center, State of the climate: Synoptic discussion for January 2014, http://www.ncdc.noaa.gov/sotc/synoptic/2014/1) - have contributed to extreme hydrologic conditions on the Great Lakes. The Great Lakes are the largest system of lakes and the largest surface of freshwater on Earth - Lake Superior alone is the single largest lake by surface area.