Warm winter keeps Great Lakes ice coverage very low

An icebreaker may be an unlikely sight in the Port of Thunder Bay this year, as ice coverage across the Great Lakes remains low.

"We are having a historically low ice year and that's due basically entirely to the fact that we've had a really warm winter so far," said Jay Austin of the University of Minnesota Duluth's Large Lakes Observatory.

"Ice cover is a very, very strong function of average winter air temperatures," he said. "We've just really had no conditions that have been conducive to the formation of ice.

"We had some cooler air earlier [last] week and there was a bit of an uptick in coastal lake ice, but really very little, if any, on the open lake."

Austin said that prior to 1998, 50 to 60 per cent of Lake Superior would be covered in ice at this time of year; in the years after 1998, the normal ice coverage for the lake would be 25 or 30 per cent.

According to the Great Lakes Environmental Research Laboratory, total ice cover across all the Great Lakes was 6.1 per cent as of Feb. 22, 2024.

"Why the air temperature this winter is as warm as it is can be due to a number of different factors," Austin said. "This is a strong El Niño year, and so that plays a significant role in upper midwest air temperatures.

"And of course there are the effects of long-term trends toward warmer air because of us changing the chemistry of the atmosphere," he said. "We pump carbon dioxide into the atmosphere and we trap more heat.

"There are several factors that are contributing to the fact that we're having this very warm winter, and it's going to take some time before we really understand exactly what was responsible for the really anomalous conditions we're having."

Austin said there are "clear ecological impacts" when there's not much ice.

"The coastal ice serves as a refuge for spawning fish," he said. "Coastal ice can also act as armour against coastal erosion, and so we will expect there to be enhanced coastal erosion from spring storms this year.

"There are going to be cultural and commercial effects. You don't have people going over to the Wisconsin south shore to visit the ice caves. Sitting here in Duluth, we don't see people ice fishing off the shore."

The lack of ice could mean an extended shipping season, however, and Austin said ice cover is a good predictor of conditions coming later in the year.

"What we should expect in a year like this, with very little ice cover, is that the the start of the summer season, where the lake starts forming a warm layer on top, will be considerably earlier this year," he said. "So I predict that instead of the early July onset of those conditions, we might see that in mid-to-late May this year.

"That typically leads to warmer water temperatures through the summer."

It also means there may not be a need for an ice breaker to visit the Port of Thunder Bay in advance of the 2024 shipping season.

"This year, the ice is well-below the normal for this region," said Guillaume Paradis, ice-breaking superintendent for the central region with the Canadian Coast Guard (CCG). "At the approach of the opening of the Soo Locks, if there is a need, an ice breaker will go [to] Thunder Bay to help.

"But at this point, there is not a lot of ice in the bay."

In an email, a CCG spokesperson said that during periods of low ice coverage, coast guard vessels remain on standby for any ice breaking requests, "to keep waterways clear and open to prevent potential flooding caused by ice jams," as well as respond to any search and rescue operations or marine pollution incidents.

Ice breaking is getting underway in other places, however, with the CCGS Samuel Risley scheduled to start breaking ice in the Thessalon, Ont., area on or around Feb. 25.

"The purpose of this operation is to break up the ice to allow commercial vessels safe and efficient movement," the CCG said in a media release.

"It is recommended that all traffic on the ice — including pedestrians, fishers, snowmobilers, and all-terrain vehicle
operators — leave the ice during ice-breaking operations," the release states. "The ice may move, creating a real danger for anyone on it.

"Additionally, plan activities carefully and use extreme caution after operations are complete as the ice will remain unstable even once the icebreaker has left the area."