Ice banks between 40 and 50 centimetres thick have caused a number of merchant ships and passengers ferries to become stuck or forced to stay in port. It's the worst Baltic freeze for 15 years.
Jonas Lindvall, controller of the ice breaking unit at the Swedish Maritime Administration told Radio Sweden's Dave Russell that the ice is a real problem.
"About 85 percent of the trade to and from Sweden comes via the sea. There's a lot of industry in the north affected, particularly the paper industry, " he said.
"The ice wouldn't usually be a problem for the merchant ships, the problem now is that it's very windy, about 20 metres per second and that means that the ice is moving rapidly, there are lots of ridges with ice that's making it problematic for the ships, so they need help from the ice breakers to get back to the different ports," he added.
The winds are set to ease within the next 24 hours but the ice will stay for one to two months.