Frozen lake could affect local weather

HOUGHTON – Lake Superior is nearly three-quarters iced over at the end of January, and experts say there’s a possibility it will be covered completely before winter’s end, for the first time since the winter of 1996-97.

But even without 100 percent ice cover, the situation will likely have a major effect on Keweenaw weather for the remainder of the season, as the western portion of the lake is already almost completely covered.

“The big impact we’ll see is shutting down the lake effect snow,” said Dr. Guy Meadows, director of Michigan Technological University’s Great Lakes Research Center. Lake effect snow occurs when weather systems from the north and west pick up evaporating lake water that’s warmer than the air, then drop it as snow after reaching land. Ice cover blocks that evaporation.

But the ice could also contribute to more frigid temperatures, Meadows added, as the warmer lake water won’t have the chance to moderate the temperatures of those same northerly weather systems.

George Leshkevich, a physical scientist with NOAA’s CoastWatch team, said the only large area of open water left on Lake Superior is over its deepest area, in the eastern basin between Keweenaw Bay and Whitefish Bay. Whether that area freezes up depends on temperatures in the coming weeks.

Forecasts show temperatures topping out in the single digits for most of the next 10 days, making continued ice buildup likely.

“At this point in time, if there’s cold and calm weather, the ice can grow fairly quickly, because we’re to the point where the water temperature is near the freezing point,” Leshkevich said.

On the other hand, strong winds can break up ice that’s already formed, pushing it into open water and piling it vertically both above and below the water line. This can mean underwater buildups of as much as nine meters.

The Soo Locks are currently closed for the winter and all shipping on the lake has halted, but these buildups can cause problems in the spring, including in waters around the Keweenaw, Leshkevich said. Even icebreaker ships, he said, can’t do much about ice so deep.

The ice can also have positive effects though, he noted. Lake Superior’s whitefish and some other fish, for example, need ice cover to protect their spawning beds from winter storms. Heavy ice, therefore, should lead to good fishing.

Meadows said invasive nuisance species have been thriving at the bottom of Lake Superior in recent years largely because of warmer temperatures, so “cooling things back down will be a good thing in that sense.”

Leshkevich said this year’s ice cover is significantly greater than what’s been seen in recent years, but that it would have been considered normal as recently as the ’70s and ’80s. 2003 saw about 95 percent ice coverage, he said, and there were heavy ice years in the mid-’90s, but the general trend has been for less ice.

“In 2011-12 there was almost no ice cover, very little on the Great Lakes as a whole,” he said.

Meadows said what surprised him most about this year’s ice buildup was the overall change in lake temperatures since 2011-12, considering the massive volume of Lake Superior water.

“It’s amazing considering that Superior holds over half the water in the Great Lakes,” he said.

Meadows said his guess is that Lake Superior won’t freeze over entirely, but he admits that’s based partially on wishful thinking regarding upcoming weather patterns.

“I suspect the weather will change for the warmer rather than colder,” he said.