Ice discs, ice circles, ice pans, ice pancakes or ice crepes are a very rare natural phenomenon that occurs in slow moving water in cold climates. They are thin circular slabs of ice that rotate slowly on a body of water's surface.

Types

Ice discs

Ice discs form on the outer bends in a river where the accelerating water creates a force called 'rotational shear', which breaks off a chunk of ice and twists it around. As the disc rotates, it grinds against surrounding ice — smoothing into a circle. A relatively uncommon phenomenon, one of the earliest recordings is of a slowly revolving disc spotted on the

Mianus River The Mianus River is a river in Westchester County, New York, and Fairfield County, Connecticut, in the United States. It begins in the town of North Castle, New York (east of Armonk) in a series of ponds at about altitude. Flowing northeast ...

and reported in an 1895 edition of ''

Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it i ...

''.

Ice pans

River specialist and geography professor Joe Desloges states that ice pans are "surface slabs of ice that form in the center of a lake or creek, instead of along the water’s edge". As water cools, ice crystals form into '

frazil ice Frazil ice is a collection of loose, randomly oriented ice crystals millimeter and sub-millimeter in size, with various shapes, e.g. elliptical disks, dendrites, needles and of an irregular nature. Frazil ice forms during the winter in open-wate ...

' and can cluster together into a pan-shaped formation. If an ice pan accumulates enough frazil ice and the current remains slow, the pan may transform into a 'hanging dam', a heavy block of ice with high ridges and a low centre.

Formation

Conditions

It is believed that ice circles form in

eddy currents Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magne ...

. It has been shown that existing ice discs can maintain their rotation due to melting.

Physics

Ice circles tend to rotate even when they form in water that is not moving. The ice circle lowers the temperature of the water around it, which causes the water to become denser than the slightly warmer water around it. The dense water then sinks and creates its own circular motion, causing the ice circle to rotate.

Size

An unusual natural phenomenon, ice disks occur in slowly moving water in cold climates and can vary in size, with circles more than 15 metres (49 ft) in diameter observed. Ice Circle of Vana-Vigala in Estonia is reported to have had a diameter of over 20 meters, whilst one approximately 298 feet (91 meters) in diameter appeared in

Westbrook, Maine Westbrook is a city in Cumberland County, Maine, United States and a suburb of Portland. The population was 20,400 at the 2020 census, making it the fastest-growing city in Maine between 2010 and 2020. It is part of the Portland– South Portla ...

in January 2019.

Notable Examples

Ice discs have most frequently been observed in

Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, Norway, and Swe ...

and North America. An ice disc was observed in

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

in December 2008 and another one in

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

in January 2009. An ice disc was observed on the Sheyenne River in North Dakota in December 2013. An ice circle of approximately in diameter was observed and photographed in Lake Katrine, New York on the

Esopus Creek Esopus Creek is a tributary of the Hudson River that drains the east-central Catskill Mountains in the U.S. state of New York. From its source at Winnisook Lake on the slopes of Slide Mountain, the Catskills' highest peak, it flows across Ulst ...

around 23 January 2014. In Idaho,

extreme weather Extreme weather or extreme climate events includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Often, extreme events are based on a locati ...

led to a rare sighting of an ice disc on the Snake River on 22 January 2014. On 14 January 2019, an ice disc approximately 298 feet (91 metres) wide on the

Presumpscot River The Presumpscot River () is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed June 30, 2011 river located in Cumberland County, Maine. It is the main outlet of Sebago Lake. The riv ...

in Westbrook,

Maine Maine () is a U.S. state, state in the New England and Northeastern United States, Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and territories of Canad ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

drew wide media attention. A smaller disc was reported by park rangers in

Baxter State Park Baxter State Park is a large wilderness area permanently preserved as a state park in Northeast Piscataquis, Piscataquis County in north-central Maine, United States. It is in the North Maine Woods region and borders the Katahdin Woods and W ...

, in northern Maine, the same month. In January 2020, an ice disc appeared on the

Kennebec River The Kennebec River (Abenaki: ''Kinəpékʷihtəkʷ'') is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed June 30, 2011 river within the U.S. state of Maine. It rises in Moosehead ...

Skowhegan Skowhegan () is the county seat of Somerset County, Maine. As of the 2020 census, the town population was 8,620. Every August, Skowhegan hosts the annual Skowhegan State Fair, the oldest continuously-held state fair in the United States. Sk ...

In January 2021 a large ice circle was discovered via satellite imagery and on 23 February 2021, an ice disc estimated to be 196–202 metres (643 – 663 feet) wide was confirmed on the

Taltson River The Taltson River is a roughly river in the Northwest Territories of Canada that drains into the Great Slave Lake. There are three hydroelectric power control structures on the river, and one power station. Name The river was formerly known as th ...

Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...

(just below Tsu Lake). It was estimated to be rotating at approximately 20–25 minutes per rotation.

Artificial ice circles

Artificial ice circles have also been created by cutting a large circle in a sheet of ice. These artificial creations are called "

ice carousel An ice carousel is a circular piece of ice made to spin like a carousel within a larger body of water, often a frozen lake. It is a man-made phenomenon, made by cutting the floating ice sheet, unlike the natural rotating ice circles. History In 2 ...

s". Record setting ice carousels are recorded by the World Ice Carousel Association.

References

External links

*Video of ice disc in Germany: *Video of ice disc in Ontario, Canada: {{ice Bodies of ice Water ice River morphology Vortices Circles