On the Sheyenne River near Leonard, ND, there is a bend in the river which causes the water to swirl.
In the fall when there are leaves in the river, the leaves get caught in the eddy. When the river freezes in the fall, it sometimes does this. The slower water within the eddy gets colder than the faster water in the main current causing the water in the eddy to freeze first. Because the eddy is moving in a circle, the ice forms a perfect circle.
This year, the very cold November/early December caused the river to freeze over in about five days so the ice circle is only about 40 feet across and already frozen in. the still picture shows the ice circle on Dec. 3, 2014.
Last fall, the ice circle formed during weather consistently near 32 degrees so it took longer to freeze, resulting in a 55 foot circle. The motion video is from November 2013. A great big thank-you to George Loegering for sending his almost magical ice circle pictures.
- Meteorologist John Wheeler
