1 Apr 14 – U.S. Coast Guard icebreakers challenged by Lake Superior ice as thick as six feet (1.8 m)in places are not expected to make it into Marquette Harbor for several days, delaying the local opening of the shipping season.
The ice thickness is at least three feet in some places, four feet in others, said Mark Dobson, vessel traffic controller for the Coast Guard’s Operation Taconite in Sault Ste. Marie. In the middle of Lake Superior, ice rubble fields six feet thick were being encountered.
The cutters can be moving along decently and then hit a “rock solid” section of ice, said Dobson. In some cases, ships have needed four hours to move one mile.
This winter’s tremendous ice cover on Lake Superior is the thickest it’s been in two decades.
http://www.miningjournal.net/page/content.detail/id/596524/Ice-breakers-challenged.html?nav=5006
Thanks to Greg for this link
“At the western end of the big lake the ice breakers are having a bad time of it,” says Greg. “One ice breaker broke down the very first day and had to return to port. The thick ice has now damaged shipping vessels and these have returned to port. This is all highly unusual.”