Marine Atlantic has been struggling to clear a backlog of more than 200 tractor-trailers waiting at its terminal in North Sydney, N.S., following a week of heavy ice conditions that led to cancelled ferry crossings and delays.

The Canadian Coast Guard icebreaker CCGS Henry Larsen is escorting ferries through the ice as they make the trip between Cape Breton and Port aux Basques, in southwestern Newfoundland.

Two ferries, the MV Highlanders and the MV Blue Puttees, were trapped in ice overnight Wednesday off the coast of Cape Breton. The Highlanders freed itself the next day, but the Blue Puttees needed a path cut by a third ferry, the MV Atlantic Vision.

Blue Puttees in ice

Marine Atlantic is asking the Coast Guard to send in heavier ice breakers to help it get through ice in the Cabot Strait. (CBC)

"This is unusual," Marine Atlantic spokesman Darrell Mercer says. "The ice conditions that we're seeing this year, it's been called some of the worst ice we've seen in decades.

"So from that perspective it's been a challenging year. From an ice perspective it's been a very cold winter, a lot of storm systems moving through and because of that we've seen a higher presence of ice.

"It's absolutely up to Mother Nature. We can hope that she cooperates and we start to see some spring weather finally."

The ferries are on schedule Sunday and Mercer expects the backlog to clear.