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Phénomène rare : un disque de glace géant... by lemondefr72 წლის პენსიონერი, ჟორჟ ლეგერინგი, იშვიათ ფენომენს, „ყინულის დისკოს“ გადააწყდა ჩრდილოეთ დაკოტაში (აშშ) მდინარე შაიენზე. ამ ვიდეოზე, რომელიც ინტერნერტში გავრცელდა და არაერთმა მედია საშუალებამ გააშუქა, მკაფიოდ სჩანს წრეზე მოძრავი ყინული, რომლის დიამეტრიც 15 კმ იქნება და ნელა ბრუნავს წყლის ზედაპირზე. Telegraph-ის მიერ გამოკითხული მეტეოროლოგების აზრით, ცივი და ჯერ კიდევ თბილი წყლის ნაკადებს შორის სხვაობამ გამოიწვია ზედაპირზე ყინულის პატარა ბლოკების წარმოქმნა. ნაკადები ამ ადგილას ქმნის მორევებს, ნაწილები კი აგლუტინირდება ერთმანეთზე და იქმნება საოცარი წრე.
Nature's answer to a whirlpool (minus the bubbles): Extremely rare spinning ice circle over 50ft wide forms in North Dakota river
- A naturally-occurring phenomenon has developed in North Dakota's Sheyenne River, which feeds into the Red River north of Fargo
- Experts say record-high air pressures at the weekend quickly froze parts of the warm river water
- Parts of the ice were picked up by an eddy and started to spin, picking up more pieces
- The end result was an ice circle measuring over 50 feet wide that has fascinated locals
On the surface, it almost looks as though someone has installed a hot tub in the middle of a lake - bubbling jets of water breaking the otherwise perfectly calm waters of the Sheyenne River.
But these aren't bubbles, and, far from someone having added a touch of spa luxury to the North Dakota stretch of water, this perfectly spherical disturbance in the water is made of ice.
The incredible spinning circle of ice, which was spotted by George Loegering while out hunting with relatives, is entirely natural albeit extremely rare.
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Spinning disc: Experts say a combination of cold, dense air last weekend and an eddy in the river likely caused this 'rare' ice circle in a North Dakota river
The retired engineer said that when he first saw the floating disc he couldn't believe his eyes.
The 73-year-old said: 'At first I thought, no way! It was surreal. You looked at it and you thought, how did it do that?'
He calculated the disk's diameter to be about 55 feet, took photos and videos of it and then turned to the internet for more information about what he, his brother-in-law and nephew had seen.
'It's not an unknown phenomenon, but it is relatively rare,' said Loegering, who lives in rural Casselton, about 20 miles west of Fargo.
Allen Schlag, a National Weather Service hydrologist in Bismarck, and Greg Gust, a weather service meteorologist in Grand Forks, said a combination of cold, dense air last weekend and an eddy in the river likely caused the disk.
'It's actually quite beautiful,' Schlag said.
'It's not a continuous sheet of ice,' explains National Weather Service hydrologist for Bismarck, Allen Schlag
The cold, dense air — the air pressure Saturday in nearby Fargo was a record high for the city for the month of November, according to Gust — turned the river water into ice, but since the water was relatively warm it didn't happen all at once.
Floating bits of ice got caught in the eddy and started to spin in a circle.
'It's not a continuous sheet of ice,' Schlag said.
'If you were to throw a grapefruit-size rock on it, it would go through.
'It's not a solid piece of ice — it's a collection of ice cubes.'
Loegering said the spinning disk had frozen up but was still visible in the river.
The phenomenon is not unknown in the Arctic, Scandanavia and Canada, but pretty rare elsewhere.
Normally they are thought to occur at bends in the 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 perfect circle.
North Dakota locals who have been admiring the ice circle are wondering how long it will last. The Sheyenne River freezes over each winter
Mr Loegering said: 'I'm not sure how long it was there (spinning),' he said.
'It had to be quite a long time.
'If you look at the picture, you can see growth rings on the disk.'
Mr Schlag said he was surprised by the size of the ice circle, which he said would be more likely on a larger river such as the Missouri.
'That might be one of the better examples I've seen,' he said.
'It's a pretty cool one.'
Read more: http://www.dailymail.co.uk/news/article-2514162/Eerie-rare-ice-circle-forms-North-Dakota-Sheyenne-River.html#ixzz2ph8SJd7B
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