Chris Brisson sends these photos of an unusual ice formation she spotted on the river in town today — “floating whimsies” as she called them.
They appear to be so-called ice pancakes, or ice pans. According to the Weather Network and other sources, they typically form in rivers when temperatures fluctuate widely. Unlike large ice sheets that form on calm waters, the turbulent flow of rivers disrupts the normal freezing process. They’re most commonly seen in areas where there’s some water movement but not too much — places like river bends or areas with gentle wave action.
The process begins with the formation of frazil ice, a slushy mixture of ice crystals and water. As temperatures drop further, frazil clusters start to freeze into larger flat plates, separated by a layer of lingering slush. The flowing water beneath prevents these plates from joining together completely.
The distinctive circular shape and raised edges of pancake ice result from the constant movement and collisions in the river. As the ice plates bump into each other repeatedly, their edges become raised and slushy, while the repeated collisions grind off sharp edges, creating their characteristic circular shape.
