By Bill Willis
January 29, 2018
- Discovery Lake hasn’t frozen solid since late February 2015, much less had a covering of snow
- Snow circles or discs are natural occurrences on streams and rivers
- Circles often rotate due to slow moving underwater currents (eddies) that smooth the outer ice edge creating the floating circle
- Ice circles can be observed in lakes, but are far less common than in rivers
Discovery Lake is known to change elevation, color, texture, and now firmness? What has happened or gotten into this water body? Has the reduction in algae made that much difference; is it a result of the cold; rock throwers; methane, or are the dipping ducks and geese up to something? Wondering has turned into wandering around the lake trying to determine what could have formed the circles as the lake morphs again.
Beginning in early January 2018, the temperatures on campus dipped to unseasonal lows (4°F) and stayed below 32°F for 208 hours. On January 3rd, as the lake began to freeze, it also received a covering of snow, resulting in patches of ice, snow covered ice and some unfrozen water. As subfreezing temperatures continued, the lake eventually froze over completely except where the waterfowl were.
Within that week, seven circular patterns were observed in the ice between EPA and NIEHS. Initially they were slightly irregular with a whitish center, but appeared to become more circular as the days passed. They were estimated to reach more than six feet across.
Things were getting interesting and questions were being asked as to “why?”
Fish, turtles, and plankton would have been too sluggish to create such symmetrical shapes. Waterfowl were too busy taking care of their own ice clearing. Currents and possibly temperature layering in the lake couldn't be ruled out entirely. It seems reasonable that water currents, and continued subfreezing temperatures, not wind are partly responsible, but it doesn't explain why the circles are where they are. Could throwing a rock into super cooled lake water cause the water to freeze in a circular pattern? That may be a plausible explanation for what was seen. Unfortunately, the ice thickness couldnlt be checked safely, but many of the circles could still be seen as the ice around them melted away. As the freeze continued, the lake actually made low frequency grinding sounds like a phonograph needle on a vinyl record that could be audible from the lake walking trail. Ice must have been moving.
Although an element of mystery remains about the causes of lake circles, eddies and/or melting are contributing to rotating ice circles in rivers and streams.