ANCHORAGE (KTUU) - It looks like an alien landscape: thousands of near-perfect spheres of ivory white trapped in glassy-clear ice in a highway-like stretch of frozen river.
When KTUU viewer Danny Foster saw the scene, he was on his snow machine a few miles up the Wulik River near Kivalina, Alaska, a village of just a few hundred located north of Kotzebue, on his way to a favorite fishing spot.
He knew he had to take some pictures.
Photo courtesy of Danny Foster
He did that, and also dug out some of the balls through the ice. When he held them, they disintegrated “like a slushie” but were rounded into perfectly-formed snowballs, some as big as a cantaloupe.
Foster sent the photos to Channel 2, where our weather team had a look but decided to pass them on to the National Oceanic and Atmospheric Association.
“We didn't really have any ideas. I hadn't seen or heard of it before,” said Crane Johnson, Service Coordination Hydrologist at the River Forecast Center for NOAA.
He did some googling and hit on some luck: the same day he got KTUU’s photo, another article came out on CNN about what looked like the same phenomenon in Finland.
He then emailed a nationally-renowned ice scientist with the US Army Corps of Engineers, who filled him in on the process for how this ice forms.
“It definitely takes a unique set of conditions,” he says.
In some cases, the snow balls froze above the water level, making an uneven, icy surface (Photo courtesy of Danny Foster)
Because water on a river is moving, the water temperature drops below freezing before it starts to form ice crystals. This is called “supercooling”- when the temperature is below freezing point but not yet solid.
As the water continues to chill, it forms what is called “frazil ice,” loose, randomly oriented ice crystals formed in moving water that can coagulate or form a sort of sludge.
Usually, those come in the shape of discs or “pans” that you might see drifting down a river near freeze-up.
Flat frazil ice pans forming on a river in Kansas (Photo USGS-Kansas Twitter)
But sometimes instead of pans, the frazil ice forms into balls that starts to build around itself and turn into essentially compacted slushballs. Reports from Russia suggest that they can get up to three feet across.
But why do they form? That’s a question that still isn’t entirely known, but scientists have suspicions.
“We suspect if you have supercooled water with frazil ice that starts to bond, and there's wave action, instead of pans, it forms balls,” says Johnson. That explains why some of the most well-recorded sightings occur in large lakes, such as Lake Superior in the Midwest.
Basically, by adding wave action to the water, the flat pans start to get rounded, compacting on one another.
Matthew Storm of UAF Geophysical Institute’s Snow, Ice and Permafrost Research Group said this “rounding and tumbling” has even happened away from water on bumpy rides in snowmachine sleds.
Johnson said the waves likely would have been blowing upriver creating breaks.
Then, of course, the waves had to stop at some point to allow the slush balls to get suspended in place with a convenient glassy-smooth viewing window.
“It was unique to see them frozen in place like that,” he said.
Johnson said seeing such rare ice formations that leave the scientists stumped - at least temporarily - is something that his group looks forward to, although it is rare.
“I would say maybe every other year, we get a really unusual photo where within a group it's like ‘No, I haven't seen that and it takes a little bit of research to find out.’”
Photo courtesy of Danny Foster
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