Northern lakes start turning to ice … in more ways than one

Northwoods Notebook

Blue jays may be high on the list when the Christmas Bird Count takes place Dec. 18 in southern Dickinson County. (Betsy Bloom/Daily News photo)

A sign of the season and the region: Six Mile Lake a week ago had only an edging of ice along the shorelines but by midweek was almost covered over — and had a fisherman willing to risk venturing out, though not far from shore.

Ice doesn’t begin to form in earnest on a lake until it has undergone a water “turnover.” Warmer water is less dense, so in summer stays atop the lake. The lowest layer often remains cold even through the hottest months, with little circulation between top and bottom.

But as the days shorten and temperatures drop in autumn, the surface water becomes more dense and heavy, breaking down the “thermal stratification” in the lake. Eventually the entire lake achieves about the same temperature. This allows wind to churn oxygenated water into the lower layers — the “turnover,” explained Paul Fafard, field sampling technician for the International Institute for Sustainable Development’s Experimental Lakes Area, a freshwater laboratory in northwestern Ontario, Canada.

“Lake turnover is extremely important in freshwater lakes, as it is the event that is responsible for replenishing dissolved oxygen levels in the deepest lake waters,” Fafard wrote in 2018 on the group’s webpage, https://www.iisd.org. “When the lakes are a uniform temperature and density, it takes relatively little wind energy to mix water deep into the lake. Wind moves highly oxygenated surface water to the lake bottom, forcing low oxygen water from the lake bottom up to the surface where it becomes saturated with oxygen. This is critical for aquatic organisms, as once the lakes freeze over for the winter, no new oxygen gets mixed into the lake from the atmosphere, and what is in the lake must last until ice goes off in the spring.”

So while November started out fairly mild, the month has taken enough of a cold turn to lower the lake’s overall temperature, allowing the ice to finally take hold and spread.

I’m assuming the smaller size of Six Mile Lake is the main reason why it has substantial ice while other area lakes still showed little. But it likely signals the colder conditions are here to stay.


Coordinator Phyllis Carlson of Quinnesec has again put out the call for volunteers to help with the local Christmas Bird Count, set for Saturday, Dec. 18.

The effort is part of the National Audubon Society’s 122nd annual 24-hour “bird census” within designated areas in the U.S., Canada, and many countries in the Western Hemisphere. Data gathered is analyzed to gauge how avian populations might be expanding their numbers and range, or losing ground.

The local count takes place in about the lower one-third of Dickinson County, from the borders with Florence County to the west to Menominee County to the east, and from the Marinette County border north to Granite Bluff, Carlson said. Given the amount of territory to be covered, the more eyes in the field, the better the tally should be.

Volunteers do not have to commit an entire day but can spend as little as a couple of hours searching a set area, Carlson said. Since all information must be filed through the local coordinator, those who might want to volunteer or offer other assistance need to contact Carlson at pcarlson279@gmail.com or 906-774-5868.

So far, reports have come in from other parts of the region that some winter finches have been sighted — pine and evening grosbeaks, purple finches, common redpolls — but not in high numbers locally. The first snowy owls also have been photographed in other counties, especially along the Lake Superior shoreline in Marquette, but again have not been numerous enough to raise hopes of an “irruption” year for these species in the Upper Peninsula.

Still, the local Christmas Bird Count usually produces at least one unexpected find for the list. A golden eagle, more common out west than in the Upper Peninsula, was among the noteworthy finds in Dickinson County in 2020.

Betsy Bloom can be reached at 906-774-2772, ext. 240, or bbloom@ironmountaindailynews@com.


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