Ice circles are unique phenomena that occur in rivers, streams, and creeks all over the world. Most go unnoticed but a few have been seen by people and captured on video or in pictures. Ice circles are rare and form under very specific conditions that often change rapidly, making ice circles quick forming and quick to disappear as well.
Ice circles form in eddies of slow moving rivers when the river’s temperature is at freezing level or lower. The river has to be moving at a very specific rate; too fast and the eddy is disrupted, and too slow and the eddy freezes along with the rest of the river, stream or creek. The current in the river has to be slow enough that an eddy forms and freezes slowly over a period of time, causing the circle of ice on the surface to freeze and continue moving in the pattern of the eddy.
Ice circles are also known as ice disks or ice pans. They always form in cold climates and have been recorded most frequently in North America and Scandinavia, although ice circles have been seen in England and Wales as well. Ice circles can vary in size depending on the eddy and the weather, but ice circles have been documented that are 50 feet in diameter.
In terms of geography ice circles form in the outer bends of rivers. This area is the most likely to form an eddy due to the bend in the river or stream as the physical bend of the river’s banks causes the current to form a circular pattern in the shallows. Over time an eddy can erode some of the riverbank creating a distinct part of the river where the current isn’t as strong. When the river dips to or below freezing in temperature the surface of the water freezes into a thin layer of ice; as the eddy currents rotate in a circle a force called rotational shear separates the ice over the surface of the eddy from the more stable ice covering stiller waters of the river near the shoreline. This ice chunk rubs against the surrounding ice as it turns which makes the circle’s edges smooth.
The earliest known ice circle was spotted in 1895 in the Mianus River, but subsequent ice circles have been observed in England, Wales, Norway, North Dakota, New York and Idaho. Various scientific magazines have more information on the latest observations of ice circles worldwide, although many go unreported.
Scientists study ice circles in laboratory settings but often do not have the chance to study them in their naturally occurring states due to the rarity in which ice circles occur. However, there are increased reporting methods available to help scientists understand this unique phenomena as observers of ice circles can take pictures, videos and measurements of ice circles that occur in their areas.
There are still questions regarding how ice circles form in waters around the world that are dramatically different from one another. For instance, ice circles form in the waters of Lake Baikal that are much differently composed than ice circles in Wales or the United States. Each river, stream, lake or creek that forms ice circles does so under similar conditions but in ways that are unique to each location. Scientists find it nearly impossible to predict the existence or formation of ice circles as they naturally occur.
Ice circles are phenomena that deserve continued study and increased publicity so that people in more northern, cold climates can keep on the lookout for such a unique event. If you or someone you know happens to come across an ice circle, take pictures or a video! Documenting ice circles as they form naturally in various bodies of water is integral to the study of ice circles and continued research from scientists around the world.
An ice circle in motion
Video from Tim Engleman.
WDAZ News. Facebook. Web access 16 February 2015. https://www.facebook.com/video.php?v=552468648169459
Ten Fascinating Natural Phenomena. The Independent. Web access 16 February 2015. http://www.independent.co.uk/environment/nature/ten-fascinating-natural-phenomena-1988668.html?action=gallery&ino=6