On coming upbound in the St-Lawrence at this time of the year ships will encounter ice and frasil ice some 20 miles from Quebec City, having not met any ice prior to that, they sometimes figure there isn't going to be any, by the time they get to Quebec , the sea chest are filled-up and that is where the problems occur. Last week, the river was ice free up until Montreal, a few days later after cold temperatures and north-easterly winds , the river was covered in ice.
Mind you that is not a reason for not using the system installed back in 2006 on the MSC TUSCANY but things have changed a lot since the ship was reflagged from Greece to Hong Kong back in 2007.