Did a Massive Ice Disk Really Form in Maine's Presumpscot River?

[jtbell]

A giant ice disk, almost perfectly circular, has formed in the Presumpscot River in Westbrook, Maine:

https://www.npr.org/2019/01/16/6858...ice-disk-takes-center-stage-mesmerizing-maine

As it slowly rotated, contact with one shore smoothed away the irregularities at its edge.

 

[davenn]

WOW
now that is pretty cool ... in more ways than just one

 

[jtbell]

cool ... in more ways than just one

I first saw this on TV, on the CBS morning news. The reporter doing a standup on the bridge overlooking the disk commented that as a Louisiana boy, he had been looking forward to his first visit to Maine. Then he found out the temperature: 10F (-12C). He probably had to find a warm coat in a hurry.

 

[Borg]

Another ice disk grabs attention in Maine

It's like aliens leaving crop circles.

 

[256bits]

So why isn't someone taking advantage of a "green" merry-g-round formed by Mother Nature, putting seats on it and charging $ for the ride of a life time.
Something to tell your grandkids that you rode on the Presumpscot Swirl.

 

[LURCH]

I was actually expecting someone to put a little tiny Lunar Landing Module, with a little US flag next to it. And maybe stamp some itsy-bitsy footy prints into the ice.

 

[LURCH]

Btw; does anyone else see a really evil grinning face in there?

 

[Baluncore]

River flows in from top right, flows out bottom left.
The disk formed in a back eddy and then moves up river until it engages with river flow.
Disk is driven by river current and so rotates counter-clockwise.
Then the curve of the fixed ice on the bank holds it in place.

 

[snorkack]

So how common or rare are ice discs on freezing rivers?
How do the major freezing North American rivers do - Saint Lawrence with its upper courses Niagara, Detroit, SS Clair and Mary, Ottawa, Nelson, Mackenzie, Yukon?

Niagara has a steady Whirlpool between the lower rapids - how does this freeze?

 

[LURCH]

Lived on the St Clair River for over 25 years; never once saw a disc.

 

[Baluncore]

So how common or rare are ice discs on freezing rivers?

They are rare enough to be interesting. I have seen pictures of smaller disks in a Swedish river. How many processes are there in nature that produce a geometrical wheel?

Disk formation requires a steady flow in the river, with an eddy that can catch and hold free surface ice. If the water flow is such that the water enters the pool on the surface, then sinks down in the eddy to exit deep, then floating ice may not be lost from the eddy and so may build up. If at some level of flow, an eddy collects logs or debris, it will probably be able to form an ice disk. The river level and flow rate needs to be steady, without pulsating waves that might break up the disk or push it over the stationary guides against the bank. For that reason, lower energy rivers are candidates, like the Presumpscot River with little drop, weirs and meanders.

Google Earth History did not show earlier ice disks in that location, but that does not say you won't find them somewhere else. The problem is having a clear sky in winter. Bubbles or scum areas that form in eddies look more like spiral or elliptical galaxies, they certainly do not form geometric circles.

 

[BillTre]

Similar are the floating islands made of matted vegetation that can in some cases rotate.
This might have been discussed in previous thread here.
In this case, the mat has to be detached from it surroundings (sides and bottom) and have sufficient current on one side vs. the other to rotate it.

 

[Baluncore]

That is an interesting vegetation circle … 34°15'07″S 58°49'47″W, as there appear to be elliptical harmonics present.

In this case, the mat has to be detached from it surroundings (sides and bottom) and have sufficient current on one side vs. the other to rotate it.

I think in the case of vegetation circles it will not be driven by water currents but by variable winds. I would expect a vegetation disk to roll around inside the outer circle with high peripheral friction, a bit like a cycloidal drive, https://en.wikipedia.org/wiki/Cycloidal_drive

As the vegetation island rotates one way, it's centroid moves in the other sense, not continuously, but only as the wind direction changes. On the other hand, an ice disk appears to be a true circle that rotates continuously about one point, with very low peripheral friction. The radius and centre of rotation may change only slowly as the disk develops, then melts and breaks up.

 

[Tom.G]

Don't think I'll be visiting, air fare is over USD $900.

 

[Baluncore]

Don't think I'll be visiting, air fare is over USD $900.

Likewise, the photos will have to satisfy me. It should have melted by now.

Has anyone found an ice disk by satellite yet?
Post the latitude, longitude and date here.

Google Earth Pro is free, it has a time slider to view historical images.
Feel the chill in your bones as you look back through the mists of time at the frost and snow.

Search clues. A low energy river with weirs and pools, or with meanders. Maybe in a pool at the bottom of a small waterfall, or at a sharp bend in a river. Also consider bays with sea ice, or bays in lakes that freeze during winter.
I expect ice disks to form during the spring thaw when the river starts to flow again, when surface ice on a pool breaks free from the bank.