The anchors don't offer a scientific explanation and sound like dithering idiots but I thought some might find this of interest.

http://www.cnn.com/video/data/2.0/video/us/2013/11/28/newday-spinning-ice-disk-in-river.cnn.html

I saw that on another forum. The interesting thing I noticed was it being a perfect circle. Weird stuff I agree!

Here are a few more at different locations:

http://www.youtube.com/watch?v=7JoGXbP0bVg

http://www.youtube.com/watch?v=mCJaG0ZVoV8

http://www.burlingtonfreepress.com/article/20100207/MULTIMEDIA/100207016/?nclick_check=1

http://www.youtube.com/watch?v=l_VVOjGqpao

Learn something everyday. Neat !

Some moron on a news site where people comment afterwards said it was a hoax and that someone got out on the ice and cut a circle. Obviously the man has never been on river ice. LOL

For me I'm surprised it doesn't happen more often. Seems to me all it takes is an eddy and floating chunks of ice that spin until they form a circle. If there are any edges that are irregular or stick out the surrounding ice will grind them off.