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Thursday, January 24, 2019

VIDEO: Cool ice

Brown researcher sets up webcam to watch Maine ice disk


To watch and get hypnotized by this ice disk, check YouTube at: https://www.youtube.com/watch?v=TVB4VU3zx8A

A Brown University researcher is keeping a close eye on a strange natural phenomenon that’s been stirring up the internet recently.

In mid-January, residents of Westbrook, Maine, noticed a circular ice disk, hundreds of feet in diameter, slowly spinning in the Presumpscot River. Drone video of the formation taken by town officials promptly went viral. 

The sheer size of the disk and its eerie resemblance to the face of the Moon captivated many and led to some wild speculation about its origins. (Spoiler alert: It’s not aliens.)

For Chris Horvat, a postdoctoral researcher at the Institute at Brown for Environment and Society (IBES), the disk was a serendipitous research opportunity. 

Horvat is a polar oceanographer who studies the connections between sea ice and climate. He realized that he had an interesting research specimen held captive in a place where it’s easily monitored.


“We’re interested in seeing how individual pieces of sea ice, which are called floes, evolve — and it’s hard to do,” Horvat said. 

“But with this ice disk, we don’t have to get a ship up to the Arctic, we don’t have to fly drones or any of that. It’s right in the middle of a city. So we have all these buildings and infrastructure around that we can use to get a look at it.”

And while a freshwater ice chunk in a river isn’t the same thing as sea ice, Horvat says, it’s still a suitable analog to test some of the techniques he uses to study sea ice evolution. 

So working quickly with town officials and local businesses, Horvat used some of his research funds from Brown to set up a webcam, which has been keeping a constant eye on the disk for a few days now.

One technique that Horvat hopes to evaluate using the disk is the use of computer vision algorithms in studying how ice floes change over time. The hope is that these techniques will help quantify how floes move or stick in place, as well as how they shrink or grow depending upon the conditions around them.

“Now we have images of a floe, updated minute by minute, that we can apply these techniques to,” Horvat said. “That’s a pretty unique opportunity.”

And it just so happened that this opportunity appeared when Horvat had a bit of time on his hands. 

His research is funded in part through the National Oceanic and Atmospheric Administration, which is subject to the ongoing federal government shutdown. Uncertainty surrounding future paychecks and upcoming field campaigns left Horvat open to exploring other projects.

“One of my government employee friends and I were talking about what we’re supposed to do during the shutdown,” Horvat said. “He suggested two options. One was painting his apartment, and the other one was taking a look at this ice disk in Maine.”

It started as “kind of a jokey conversation,” Horvat says, and he wasn’t even aware that the disk existed at the time. But the more he looked at images of the disk on the internet, the more interested he became.

“I thought that because the cost of installing a webcam there is so small compared with the cost of doing field research, it’s an opportunity we should take advantage of,” he said.

But research value aside, ice disks are just neat to look at, Horvat says. They’re fairly rare, though others have been recorded. 

They’re formed, according to Horvat, through a combination of a river’s geometry and temperature conditions. In the case of the Maine disk, it took shape at a bend in the river that produces circulations known as back eddies.

“You get this circulation pattern that on the surface looks like a vortex,” Horvat said. “Ice that’s formed downstream will hit this vortex and form an ever-larger chunk. As it spins, it rubs against the side of the river and that’s what makes it symmetrical.”

In the days since the camera started running, there’s already been a significant change in the disk’s behavior. Specifically, it stopped spinning. That’s probably because frigid temperatures are freezing the water around the disk, causing it to get stuck, Horvat says. He’s interested to see what happens next.

“It might just freeze in place and become a part of this river ice that’s spanning the river,” he said. “Or if it gets warm enough, maybe the power of the river will be enough to break the ice that’s holding it to the bank.”

Time, and a constant webcam view, will tell.

“It’s exciting [to watch] the life and death of this ice disk,” Horvat said. “It’s not something I thought I’d be spending all my time staring at images of, but it’s been fun.”