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Ice circle

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Ice disk on Vigala river (Estonia) filmed by a drone, January 2019.
Ice circles on the Doncaster River, Quebec
A long exposure image showing the rotation of the large ice circle on the Esopus Creek in New York

Ice discs, ice circles, ice pans, ice pancakes[1] 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.[2] As the disc rotates, it grinds against surrounding ice — smoothing into a circle.[3] A relatively uncommon phenomenon, one of the earliest recordings is of a slowly revolving disc spotted on the Mianus River and reported in an 1895 edition of Scientific American.[4][5]

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' and can cluster together into a pan-shaped formation.[6] 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.[7]

Formation

Conditions

It is believed that ice circles form in eddy currents.[8] It has been shown that existing ice discs can maintain their rotation due to melting.[9]

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.[10]

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 feet) in diameter observed.[11][12][13][14] Ice Circle of Vana-Vigala in Estonia is reported to have had a diameter of over 20 meters,[15] whilst one approximately 298 feet (91 meters) in diameter appeared in Westbrook, Maine in January 2019.[16]

Notable examples

Tsu Lake ice circle. Taltson River, Northwest Territories. 23 February 2021.

Ice discs have most frequently been observed in Scandinavia and North America. An ice disc was observed in Wales in December 2008 and another one in England in January 2009.[17][3] An ice disc was observed on the Sheyenne River in North Dakota in December 2013. An ice circle of approximately 15 m (50 ft) in diameter was observed and photographed in Lake Katrine, New York on the Esopus Creek around 23 January 2014. In Idaho, extreme weather 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 in Westbrook, Maine, United States drew wide media attention.[18][19][20] A smaller disc was reported by park rangers in Baxter State Park, in northern Maine, the same month.[21] In January 2020, an ice disc appeared on the Kennebec River in Skowhegan, Maine, United States[22]

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 ft) wide was confirmed on the Taltson River, Northwest Territories (just below Tsu Lake). It was estimated to be rotating at approximately 20–25 minutes per rotation.[23]

Artificial ice circles

Main article: Ice carousel

Artificial ice circles have also been created by cutting a large circle in a sheet of ice.[24] These artificial creations are called "ice carousels". Record setting ice carousels are recorded by the World Ice Carousel Association.[25]

See also

  • Foam line – Accumulations of foam on the surface of freshwater water courses or bodies
  • El Ojo - Rotating floating circular island in Argentina's Paraná Delta, consisting of vegetation and soil

References

  1. ^ "Ice pancakes float along a river in the Highlands". BBC News. Retrieved 18 September 2021.
  2. ^ Patrick Garrity (7 February 2010). "VIDEO: Moscow Ice Disk a rarity of nature". Burlington FreePress.com. Archived from the original on 30 July 2012. Retrieved 19 February 2010.
  3. ^ a b "Spinning ice disc phenomenon seen in British river for first time". Telegraph.co.uk. Telegraph Media Group Limited. 13 January 2009. Archived from the original on 19 January 2009. Retrieved 22 April 2010.
  4. ^ Bates, J. M. (9 February 1895). "A revolving ice cake". Scientific American. 72 (6): 86. Retrieved 30 November 2013.
  5. ^ Rickard, B et al: Unexplained Phenomena, page 190. Rough Guides, 2000.
  6. ^ Joe Desloges. "Perfect "Ice Circle" Forms near Toronto, Canada". Retrieved 14 January 2009. cited in: Scroggins, Kate; Roberts, Rob (18 December 2008). "Man stumbles on round, spinning 'creek circle'". Posted Toronto. National Post. Archived from the original on 6 September 2010. Retrieved 29 October 2010.
  7. ^ Joe Desloges. "Perfect "Ice Circle" Forms near Toronto, Canada". Retrieved 14 January 2009.
  8. ^ "Crop Circles in the Ice: How Do Ice Circles Form?". Modern Notion. 22 December 2015. Retrieved 16 January 2019.
  9. ^ Dorbolo, S; Adami, N.; Dubois, C.; Caps, H.; Vandewalle, N.; Barbois-Texier, B. (2016). "Rotation of melting ice disks due to melt fluid flow". Phys. Rev. E. 93 (3): 1–5. arXiv:1510.06505. Bibcode:2016PhRvE..93c3112D. doi:10.1103/PhysRevE.93.033112. hdl:2268/195696. PMID 27078452. S2CID 118380381.
  10. ^ MacFarlane, Drew. "Maine River's Massive Disk of Spinning Ice a Sight to Behold". The Weather Channel. Retrieved 18 March 2019.
  11. ^ Daniel Ostler. "Rare Sighting of an Ice Disk in Idaho". news.yahoo.com. Archived from the original on 2 February 2014.
  12. ^ "Giant ice circle spinning in Esopus Creek". recordonline.com. Retrieved 16 January 2019.
  13. ^ Blake Nicholson, Unusual ice circle forms in North Dakota river Archived 11 December 2014 at the Wayback Machine, 26 November 2013, Associated Press
  14. ^ Pete Thomas, Giant spinning ice circle discovered in North Dakota’s Sheyenne River Archived 25 January 2015 at the Wayback Machine, 26 November 2013, GrindTV
  15. ^ Jaan Viska: Jääratas pöörlemas Vana-Vigalas – mitte ainult kylauudis.ee, 11. jaanuar 2017
  16. ^ "Massive spinning ice disc forms in US river". BBC News. 16 January 2019. Retrieved 16 January 2019.
  17. ^ "Ice disc brings touch of Scandinavia to Devon river". Times Online. The Times. 14 January 2009. Retrieved 22 April 2010.
  18. ^ "Ice disk mania draws crowds, boosts business in Westbrook". WMTW ABC News. 19 January 2019. Retrieved 19 January 2019.
  19. ^ "Massive spinning ice disc forms in US river". BBC News. 16 January 2019. Retrieved 16 January 2019.
  20. ^ "Onlookers share theories, find meaning in giant Maine ice disc". Bangor Daily News. 15 January 2019. Retrieved 16 January 2019.
  21. ^ "Westbrook isn't the only place in Maine with an ice disk". Millinocket, Maine: WMTW ABC News. Associated Press. 18 January 2019. Retrieved 19 January 2019. Officials at Baxter State Park in northern Maine shared a photo of an ice disk that's about 30 or 40 feet wide, located in wilderness more than 200 miles north of much larger disk that formed in Westbrook.
  22. ^ "Ice disk appears in the big eddy in Skowhegan". Retrieved 23 January 2020.
  23. ^ (K. Cox, personal communication, 23 February 2021).
  24. ^ Cook, Greg. "Mainers Create World's Largest (So They Say) Ice Merry-Go-Round". Wonderland.
  25. ^ "Fancy a spin? Quebecers in Abitibi break world record for largest ice carousel". CBC News. 11 December 2019.

Further reading

Wikimedia Commons has media related to ice circles.
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