I got a call from Dean Kjerland at Art On Water Gallery yesterday, alerting me to some lily pad-like ice floes circulating below the Ames Mill dam. He wondered whether they were pollution related. Rob Schanilec at By All Means Graphics theorized that last summer’s repairs to the adjacent retaining wall may be causing a different circulation pattern in the water, as he doesn’t remember this phenomenon occurring.
Update 12/25: Patrick Enders emailed me this photo of a single large ice circle at the foot of the dam that he took with his iPhone about 1-2 weeks ago. He says in a comment below that there were two of them.