Algae and ice? Glaciologist weighs in on 'amazing' ice formation spotted on Manitoba lake

It was a strange sight captured on a Manitoba lake – disc-like hunks of ice speckled with what appeared to be green algae.

The photo was taken in Brereton Lake and posted to a Whiteshell community Facebook group.

“In more than 60 years, I’ve never seen the lake freezing with algae still present. Scary!” the poster wrote alongside the image.

Residents responded, noting Brereton, a lake about 135 kilometres east of Winnipeg, has been ‘like pea soup’ since August.

CTV News spoke with glaciologist and associate professor in the University of Alberta’s department of Earth and atmospheric sciences, Jeffrey Kavanaugh to get his take on what caused the eye-catching phenomena.

"This is a beautiful photo showing just how amazing ice can be in our environment, especially in Canada, and the beauty you might capture on a morning stroll."

While he agrees the disc-like shapes look like pancake ice, the round formations that form when a thin layer of ice gathers on the surface of water agitated by wind or waves, he doesn’t believe current conditions on the lake point to that.

“Looking at lake level data, it doesn’t look like the lake level has dropped much over the last week or so, not enough to strand this lake ice up high, and it doesn’t look like the lake ice is piled up as you’d expect by wave action or wind action,” he said in an interview Wednesday.

More likely, he says, the ice wasn’t formed on the lake, but was rather a frost sheet that formed on the boat launch, which then melted back in a way that was modified by what’s beneath it.

“And what’s beneath it looks like an algal-rich mud flat.”

Kavanaugh says as it cooled, the sheet either contracted or dried, creating cracks. Those cracks were then warmed by the sun, causing the ice to melt away from the margins where the cracks occurred, amplifying their appearance.

As for the algae, he says the shallow water and mud flats are common settings for the blooms, thanks to the speed at which the sun can heat them. As water retracts during the colder months, algae can be left behind on mud flats.

The glaciologist warns he has not visited the scene to verify for himself, though a trip to Manitoba lake country sounds quite lovely, he says.

However, Kavanaugh guesses by the time he could travel to Brereton Lake, the phenomenon might be gone altogether thanks to the mild conditions.

He says the person who snapped the photo was likely in the right place at the right time to behold the icy rarity.

“These icy features that have a short lifespan are often missed or often require a very specific set of conditions to form in the first place, and so the likelihood of seeing something like this might well be quite low.”