An aerial view of Lake Superior from Thursday, when ice cover reached about 85 percent, is shown. (Photo courtesy of the National Oceanic and Atmospheric Administration CoastWatch)

MARQUETTE — Lake Superior’s ice coverage has greatly surpassed expectations this year.

Earlier in the season, forecasters predicted the lake would reach just over 50 percent ice coverage this winter. But as of Friday, Lake Superior was over 85 percent covered, far exceeding the prediction and the lake’s long-term average of 55 percent, according to the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory, or GLERL.

This year’s frigid conditions triggered the rapid expansion of the ice that exceeded predictions, said Jia Wang, a research ice climatologist and physical oceanographer at GLERL.

“This year’s weather is very strange in Lake Superior; it’s a colder temperature than the rest of the other lakes,” Wang said, noting this is due to the “Arctic vortex” that hit Lake Superior at full force in late January.

Wind and wave conditions, in combination with temperature, are the major factors contributing to the widespread ice coverage this year, said Joe Phillips, a meteorologist at the National Weather Service office in Negaunee Township.

“The big ingredients for ice coverage to grow would be low waves and cold temperatures,” Phillips said. “So in order to make big waves, you have to have high winds; so if you have a period of calm winds with really cold temperatures, the ice coverage can grow. In January, we had a pretty significant cold period here and that helped to freeze up a lot of the water. Then we had a couple of storms recently that broke it up, … (but) because we’ve been cold for a good bit for the past few weeks a lot of that has grown and solidified.”

Lake Superior’s ice cover has nearly doubled since early February, as it ranged from 40 to 50 percent for much of the first week of that month. But since Feb. 17, it has ranged from 70 to 86 percent, peaking at 86 percent Thursday.

Earlier this week, ice coverage increased about 10 percent within 12 hours, rising from around 75 percent at 2 p.m. Wednesday to nearly 85 percent by 2 a.m. Thursday.

Thursday’s peak of 86 percent is also nearly 10 percent higher than the maximum coverage reached last year; and far exceeds the level observed during the same dates in 2017 and 2018, which were 1 percent and 56 percent, respectively.

With cold temperatures in the forecast for the coming days, Wang thinks it’s likely 90 percent coverage could be reached this week.

While 90 percent is higher than average, Wang and Phillips emphasized that it’s not necessarily a historic event; ice cover of 90 percent and above has occurred several times in the last 20 years, in the years of 2015, 2014, 2009 and 2003.

“It is a little abnormal to have that much ice cover so early in the season, but it’s certainly not unusual. We’ve seen it a number of times,” Phillips said.

However, seeing ice coverage exceeding 95 percent is a much rarer event on the lake, Wang said, noting that he doesn’t anticipate seeing 100 percent coverage this year.

The last time the lake ice reached 100 percent coverage was 1996, which is the only time 100 percent coverage on Lake Superior has been noted since records started in 1973, according to GLERL data.

With most of the lake frozen over, it can also have impacts on the area’s weather, as less moisture is able to escape with the lid of ice over the water. This means there’s less moisture the lake can contribute to forming lake-effect snow and cloud cover, Phillips said.

The rate and timing of the lake’s eventual thaw will also impact the area’s weather, Phillips said, noting that it “will certainly be a heavy player in what happens.”

“I think a lot of folks know that in the U.P., being positioned between three Great Lakes, our weather can easily change just based off of conditions on the lake,” Phillips said. “As we get through spring, we start approaching the time when the lake starts thawing out and the amount of ice coverage is going to be a factor in our weather.”

Many residents might be wondering how quickly the lake will thaw and exactly what impact it’ll have on spring weather, but it’s difficult to predict due to the many variables involved, Phillips said.

“It’s hard to tell right now, a lot of that is going to depend on how quickly that warms up in the spring,” Phillips said. “The amount of precipitation or rainfall that we get could play a big factor in that as well. And if the winds pick up as well, the waves could break up some of that ice. But it’s hard to tell how quickly or when it’s going to break up.”

For an overview of current, historical and forecasted ice coverage on the Great Lakes, visit www.glerl.noaa.gov/data/ice/#overview.

For more information and daily updates on ice coverage, thickness and more metrics on Lake Superior specifically, visit: www.glerl.noaa.gov/res/glcfs/glcfs-ice.php?lake=s&type=F&hr=01

Cecilia Brown can be reached at 906-228-2500, ext. 248. Her email address is cbrown@miningjournal.net.