You’ve heard of blizzards, and maybe even the polar vortex, but have you heard of ice pancakes? What about ice bites or ice jams? These unique names sound fascinating, but some of these phenomena can also be dangerous.
In early February, the National Weather Service office in Detroit issued a flood warning along Michigan’s St. Clair River due to an ice jam. Both the Canadian and US Coast Guards worked to break that ice jam, which caused “significant flooding of homes and businesses” in the area.
An ice jam occurs when pieces of floating ice build up and block the flow of water in rivers and streams.
“The main concern with ice jams is flooding,” said Jennifer Gray, CNN Meteorologist. “The most common places for ice jams are usually near bridges and sharp turns in rivers. When large chunks of ice flow up against a bridge, that bridge acts like a dam causing the water to back up behind it.”
Mark White, Deputy Director for the St. Clair County Office of Homeland Security and Emergency Management, told CNN that there were a couple of hundred homes that had some flood damage from that event earlier this month.
There were also impacts to the gas supply, electric, and other utilities because the water levels rose “so darn quickly to our coastal area along the St. Clair River,” White noted.
The National Weather Service office in Great Falls, Montana, warned that if temperatures remain well below freezing for the next several days, the potential for ice jams will continue to increase.
They warn residents in low-lying areas to remain alert for possible flooding conditions.
“Ice jams are like chain-reaction car crashes on an icy or snowy road,” says Chad Myers, CNN Meteorologist. “Most jams occur on flat slowly lumbering rivers, not on swift-moving streams.”
Bites, pancakes and balls
This week, because of the bitter cold temperatures across much of the central US, peculiarities such as ice pancakes, ice bites, and ice balls are starting to pop up.
Ice pancakes, much like their namesake, look exactly like you think they would, round flat discs made of ice. They are very common in the Arctic, but typically only start making an appearance in the lower forty-eight states once the temperature hits below zero for several days.
You will not find ice pancakes on land. This phenomenon is limited strictly to bodies of water such as rivers, lakes, or oceans.
Once those bodies of water are cold enough, the chunks of ice that have started to form will knock against each other forming elliptical-shaped discs with rounded edges.
“A signature feature of pancake ice is raised edges or ridges on the perimeter, caused by the pancakes bumping into each other from the ocean waves,” the National Snow and Ice Data Center explains.
Another signature winter spectacle is ice balls. These are more common than ice pancakes, usually making an appearance every winter along bodies of water and shorelines. Similar to pancake ice, it is the agitation caused by the waves that create the rounded shape.
“Ice balls form when turbulent water near the shore breaks up a layer of slushy ice,” says Haley Brink, CNN Meteorologist. “As the waves crash ashore, it causes the ice to spin in place, which smooths it to form spheres.”
Ice bite events are associated with frigid cold weather. Ice formation in rivers often causes reductions in flow downstream, which drops water levels, making them unnavigable. This can have a significant impact at St. Louis, leading to low water levels that ground navigation and expose water intakes.
“The lower portions of the upper Mississippi and the Illinois River are seeing relatively decent flows and levels are good for navigation, especially around St. Louis, but extreme cold outbreaks give us a concern for ice bites which takes flow out of the river. Ice gets created in the pools, we drop a lot of flow, which drops stages and becomes an issue for potential groundings,” says Justin Palmer, hydrologist with the North Central River Forecast Center in Minnesota.
CNN’s Rebekah Riess, Dave Alsup, and Tom Sater contributed to this story