Though North America is a full month into astronomical spring, the Great Lakes have been slow to give up on winter. As of April 22, 2014, the Great Lakes were 33.9% ice covered. Lake Superior dominated the pack. The picture below was from just a few days ago when the lake was still nearly 64% ice covered where the ice was nearly a foot thick on average.
This amount of ice still left on the Great Lakes is clearly above average and far above the last few years. Ice was completely gone by this date in 2012 and just 3.6% last year. The Lakes reached their peak ice cover on March 6th when 92.2 % of water was covered, the second highest level in four decades of records. At that point, ice on many of the Lakes topped 2 feet, with some of the bays more than 6 feet thick. Air temperatures in the Great Lakes region has been well below average since December, and the cool pattern is being reinforced along the coasts because the water is absorbing less sunlight and warming less than in typical spring conditions. The graph below, based on data from Environment Canada, shows the 2014 conditions for all of the Great Lakes in mid-April compared to the past 33 years.
Lake Superior ice cover got as high as 95.3% on March 19. By April 22, it was reported at 59.9%; Lake Huron was nearly 30.4%. As many as 70 ships have been backed up in Lakes Michigan, Huron, and Erie, waiting for passage into ports on Lake Superior. The U.S. Coast Guard has been grouping ships together into small convoys after they pass through locks at Sault Ste. Marie, in order to maximize ice-breaking efficiency and to protect ships from damage.
Superior is the world’s largest freshwater lake by area (82,100 square kilometers or 31,700 square miles) and the third largest by volume. The waters average 147 meters (483 feet) in depth, and the basin is believed to hold about 10 percent of the world’s liquid fresh water.