Amid a prolonged deep freeze that has left more than 85 percent of the Great Lakes frozen, schools closed and produced eye-catching winter scenes, shippers, anglers, boaters and even weather watchers are wondering what the arctic conditions will mean for lake activity in the months ahead.

Ice fishermen may rejoice and tourists marvel at the ice caves along the Lake Michigan shoreline or the partially frozen Niagara Falls in Ontario, but the second straight year of ice coverage surpassing 85 percent could bring cooler temperatures in the region in the spring, delay fish spawning and extend lake level gains of recent years, according to scientists.

It all depends, they say, on evaporation, rainfall and how fast the ice melts.

"When you have this much ice, it means it's around longer than it typically is" after the freeze, said state climatologist Jeff Andresen, a professor at Michigan State University.

As of Thursday, a near record-breaking 98 percent of Lake Erie and 82.6 percent of Lake Ontario were iced over, said the National Oceanic and Atmospheric Administration. With several more subfreezing days ahead, levels could challenge last year's peak of 92.5 percent during an unusually cold and snowy winter.

The National Weather Service forecasts subfreezing cold locally at least through Wednesday, with a low of minus 7 Friday morning.

The region's temperature last crossed the freezing mark Feb. 11, when the high was 34 — normal for mid-February.

A jet stream has settled over the region since last month, funneling cold air across bodies of water that might already have shown lower-than-normal temperatures at winter's start, Andresen said.

"It didn't take as long for the water to cool down. If you look at the growth of the ice especially in the last three or four weeks, it's extraordinary and way, way above what it typically is."

Usually by this point in the winter season, the region has had "a period of thaws or at least some let up" from deep freezes, Andresen said, "but that has not been the case this year."

That can affect conditions later on. "When we come into spring with an unusually large ice pack, we do tend to see slightly cooler temperatures," Andresen said.

Climate scientists have found that heavy ice cover may help raise low water in the Great Lakes and protect shorelines and wetlands from erosion, while the extreme cold could also kill some insect pests and slow the migration of invasive species.

Although national weather experts predict a temporary break in the pattern as soon as early March, the Great Lakes could "likely see a lag or delay in the break up of the ice," Andresen said. "I would think that's a pretty strong bet for the early spring at this point."

The extended stretch of cold weather has left ice-breakers with an uphill struggle to keep Lake Erie ports open.

Conditions on the shallowest of the Great Lakes are especially treacherous because northeastern gales last weekend caused ice ridges as high as 5-7 feet to form in spots, said Chief Warrant Officer Robert Zamora, ice officer for the U.S. Coast Guard station in Detroit.

"As you run through the lake north to south, pressure ridges have stacked up, one on top of another, like a domino effect ... that's what we are encountering right now," he said. "The wind stands up ridges 5 to 7 feet tall and they just freeze up.

"We have a few ice breakers out there looking for paths into port," but the continued cold and wind has made that difficult, Zamora said.

Ice caves forming

Ice levels on the other Great Lakes are 91.5 percent of Lake Superior, 63.2 percent of Lake Michigan and 92.8 percent of Lake Huron. Lake Ontario's level, 82.6 percent, is just 3.1 percent below its record ice cover, 85.7 percent, set in 1979.

Lake Michigan last year broke a 37-year-old record with ice spread across 93.29 percent of the lake. Westerly winds, which break up the ice and move it around, are partly to blame for Lake Michigan's low ice cover this year, said George Leshkevich of the Great Lakes Environmental Research Laboratory.

"Lake Michigan is even more difficult, it seems, to freeze over even compared with Lake Superior," because it runs north and south, he explained.

It's been cold enough for a long enough time to again form ice caves along the shoreline of Lake Michigan outside Traverse City. The caves are formed by wind and waves pushing new ice on top of existing ice.

Glen Arbor resident Eric LaPaugh says the caves aren't quite as big as they were last year. Thirty-foot ice formations were spotted on Leelanau County's shoreline last winter, attracting many visitors.

For people interested in seeing the caves, LaPaugh says to not to walk on the mound of the cave because it's hollow, and that they could fall through the ice.

Ice-breaking tugs in the Sturgeon Bay area of Wisconsin have been active keeping shipping Lake Michigan channels open, said Ensign Tom Morrell, a Coast Guard spokesman based in Milwaukee.

Last year's ice levels fell just short of the all-time record, 94 percent, set in 1979, and delayed spawning seasons for some Great Lakes fish. The extensive ice coverage also helped boost water levels on the lakes, which had been below average for years.

After last year's ice cover, "water levels were pretty much back to average by last summer when they were at record lows a year and a half earlier," said John Bratton, a senior scientist with LimnoTech. Bratton added that was "more directly a result of rainfall."

Scientific reports last year showed that rising and falling water levels in the Great Lakes are influenced by evaporation, rain and snowfall in ways not fully understood and are becoming less predictable as the climate warms.

Last winter's bitterly cold weather formed ice on areas of the lakes that reduced evaporation by blocking water vapor from rising into the atmosphere, keeping water temperatures cool well into summer.

Many in and around the lakes have waited for lake levels to rebound closer to their historical averages because they allow commercial vessels to carry more cargo, recreational boats to enter and exit marinas and harbors more easily, and property owners to enjoy their more traditional shorelines.

They also help stop the development of algae in shallow areas, which have created toxic blooms. It's possible algae blooms could be delayed this year, Bratton said, but "what tends to have a bigger effect is how the snow melts and what the rain is like in the spring."

Associated Press contributed.

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