Spinning snow and ice circles grace a local waterway

The chances of spotting a floating, spinning ice or snow circle in a local stream are relatively slim, experts and enthusiasts agree.

Yet those chances vastly improve when winter walkers prowl along riverbanks — which is exactly what Heidi Conant did Saturday at Otter Creek below Middlebury.

There they were, more than a dozen of them, pirouetting like white flapjacks, nudging each other in the slow-moving water.

Conant, a Winooski resident whose ancestors lived and worked along the Otter Creek for generations, said Tuesday she has encountered several large floating ice disks in her lifetime, but never a cluster of smaller ones.

The congregation she observed over the weekend appeared to have been partially formed on top of foam that can sometimes be seen, year-round, in sluggish, eddying water.

"It looked like pizza dough that you would not want to eat," Conant said.

Gentle, spinning collisions between ice disks and with neighboring ice are responsible for grinding down rough edges and creating nearly perfect circles, most scientists agree.

It sounds simple. But more complex fluid dynamics might be at play, literally below the surface.

A team of Belgian physicists in 2015 theorized that a disk's spinning motion might be the result of water melting from the underside of the ice slab, and then creating a vortex as it spirals down through the relatively warmer water.

Published online in Physical Review E, that study notes the rotation of the ice sped up when scientists increased the temperature of the underlying water.

But ice circles also form in extremely cold water.

In early February 2010, members of the Green Mountain Valley School Nordic Team documented a spinning ice disk in the Little River in Moscow, near Stowe.

That disk, reported Tim Weston, was thick enough to support his weight.

Common sense would dictate that these uncommon wonders of nature be admired and/or studied from the safety of shore.

See also: Frazil Ice and Ice Meadows

Contact Joel Banner Baird at 802-660-1843 or joelbaird@freepressmedia.com. Follow him on Twitter @VTgoingUp.