What are those weird folds of ice on the Mississippi River in Minneapolis?

    MINNEAPOLIS (WCCO) -- The multiple layers and swirls atop the Mississippi River between Third and Hennepin avenues in downtown Minneapolis have been fascinating passersby.

"It looks just like a holiday frosting this season!" said Minneapolis resident Nancy Birrell.

You could say it's "icing on the cake" of our first snowstorm, bringing joy and curiosity to Minneapolis.

Those layers and swirls are technically called "frazil ice." Area residents are saying they have never seen such a sight.

"It's a little bit celestial looking," Birrell said.

But another ice-watcher worried about the color.

"I noticed that the water looks extremely dirty compared to when I walked past here five years ago," said Ian Antonio. "It was really clear... now it's extremely dirty."

According to weather experts in Ontario, frazil ice is a kind of slush ice. It forms when cold air temperatures and wind chill combine to cause surface water temperature to be cooled below the freezing point.

Once the water reaches "super-cooled" temperatures, solid ice is unable to form because the water is either moving or flowing too fast. As that slushy ice travels downstream, it eventually piles against obstructions like islands, bridge piers and abutments.

As the frazil ice comes to rest, it accumulates, thus causing a wavy appearance, as though it has been folded in on itself in wintry rolls.

"When the water is turbulent and keeps getting mixed around a bit... that can prevent it from freezing over completely and you get these slushy ice crystals that form that really cool, undulating pattern," said NEXT Weather Meteorologist Mike Augustyniak.

Here in the U.S., frazil ice can be most famously found in Yosemite National Park and in the Hudson River — and now, in Minneapolis.