The ice flow started gaining attention when workers in nearby office buildings in Westbrook returned to work on Monday.
In addition to the ice sheet's symmetrical form, which makes for stunning pictures, the circle is captivating because it continues to move in a counter-clockwise rotation. Pictures and videos of the marvel have been republished by outlets around the world, including news websites in the UK and New Zealand .
Tina Radel, the town's marketing and communications manager, told the Associated Press that the ice flow formed in a part of the river that has a circular current, which creates a whirlpool effect.
But experts say there may be a more complicated scientific explanation for how it formed.
Paul Nakroshis, an associate professor of physics at the University of Southern Maine, told Maine Public that he started reading research papers on similar ice circles after this one popped up this week. He said one paper was published in a well-respected journal in 2016 that theorized the spinning had to do with ice melting underneath the disk.
When the ice melts, he explained, it becomes more dense and sinks downward, creating "a vortex that causes the disk to rotate." But Nakroshis said he's not sure that theory works when applied to the Presumpscot River, which is much colder than the temperatures created in the lab experiment.
"So most likely the cause of the rotation is just the river water going by the disk, and once it starts rotating in that direction it's probably going to continue," Nakorshis told Maine Public.
City officials told WGME that the disk in Maine will likely only stick around for a few days, until it either melts or the entire river freezes.
So the ice circle has become somewhat of a tourist destination for Mainers looking to catch a glimpse of the rare site.
Meanwhile, the circle is offering entertainment for local birds as a naturally occurring carousel.
Rob Mitchell, who owns an office building near the ice circle, told the Portland Press Herald that ducks are sitting on the spinning ice sheet like it's a "big Lazy Susan."
"It's a big duck-go-round," he said.
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