New insights regarding ice rings! You might want to catch up with the original post:
Waves in Slush!
I heard from a few people who describe ice rings forming by waves in slush, not the more popular circumferential crack theory.
Bubbles cause these. Every “bloop” creates a wave and when it’s snowing on open water and slowly forming the white ice, this is what happens. I watched it when I was like ten sitting on our dock.
-Bobby
Bobby’s observations suggest that there wasn’t any black (congelation) ice.
Another Big Lake resident emphasized how many springs there are in Big Lake, some with a 5-7 ºF higher temperature compared to surrounding waters. He describes conditions for ice rings at a spring site near his house:
Just at freezing temperature, wet heavy snow. It skimmed over just enough to cause a thin layer of ice/snow mix and with the temperature hardly below freezing overnight and no more snow accumulation the next day the slight waves from the spring caused that very thin ice to break up just slightly in a circular pattern and then it dipped down into the teens and froze solid like that. The thin layer of ice/snow may have been more like a sheet of slush.
-Andy Weber
Andy said that the amplitude of the waves generated by the spring in the summer is about 1 inch (2 cm). The ice ring feature he watched form was 80-90 feet across.
It is really helpful to have these actual observations, but even so, I struggle to understand how waves would form ice rings.
I’m assuming these are capillary waves. One problem is that where ice rings intersect, they don’t look anything like where capillary waves intersect—we don’t see the ghost of the second set of circles:
And how would a wave sort the slush into bands of more and less saturated snow? Does water accumulate at the nodes between the crests and troughs?
I struggle with the scale too … it seems unlikely that a point source could generate waves to a distance of > 150 feet, as seen at Big Lake.
And of course, what causes the source of the bubbles? To make matters worse, I received photos of ice rings where there are no sources of springs or bubbles! These photos are from a hatchery overflow channel in Leavenworth, WA. Thanks to Kyle Sullivan-Jones for sharing!
This overflow channel is about as close to a laboratory setting as we could hope for. Unfortunately, the simpler setting creates more questions than answers!
Observations
These features formed when a lot of snow (14 inches, 36 cm), and then rain, fell on open water. There is little or no black ice, as revealed by the classic rock throw test (see video below). The heavy snow matches conditions at Big Lake (8 inches, 20 cm).
There is little or no source for bubbles or upwelling! This is the real bugger.
The overflow channel is a cement structure. The water is 1-2 feet deep (30-60 cm) and the bottom consists of sandy dirt and small rocks. There is very little vegetation (a possible source for bubbles) and very little room for convection! Kyle thinks the water level was rising in the channel when the ice formed … I’d like to know more about what that looks like.
The video below has three clips (from Kyle):
- A rock throw test.
- The upstream end of the channel. You can see open water (closest to the natural river bed) transitioning to thin slush. Note the density of lake stars. Given the setting, I’d guess that lake stars have more to do with surface debris than with upwelling. It is consistent to observe more lakes stars nearer to the edge of ice cover.
- Ice rings at the far end of the channel.
Conclusions
The crack theory of ice ring formation seems less likely! Bubbling has been observed to form rings in slushy water (Big Lake interviews). But rings can also form without an obvious source of bubbles or upwelling (Leavenworth). What the heck?!?
Big thanks to Kyle, Andy, and folks in the Big Lake Community Forum who shared their observations.
Some thoughts: could both be true? Could bubbles/springs come up under a layer of thin ice and be the starting spot for the cracking model? I struggle with the same questions around the way a wave would travel through slush for that distance. The crack theory makes sense to me when I think of it as the cracks being flaking of a curved edge rather than circumferential cracking.
Also, in the hatchery outflow, are there sources of incoming water from the hatchery? One of the ring formations seems like it starts from a corner, which seems like a logical place for a pipe to be dumping water in from the hatchery. There seem like there are multiple ring formations there though, so maybe that thought doesn’t lead anywhere.
The way the rings die out close to the wall seems like it could support there being black ice under it all. It would theoretically be older and thicker along the edges and less likely to crack under the weight of the snow, right?
Anyway, envious of the extent of your rabbit hole. Fun stuff to think about.
I’ve emailed the hatchery … hoping to hear if there is any water pumped in or out of the channel.
From the literature (Knight, 1987):
> A heavy snowfall probably prevents the formation of a continuous ice cover, because any little patch of impermeable ice sheet that did form would be depressed immediately by the falling snow, flooded, and covered by slush.
> The writer has found himself surprised at the range of phenomena that occur when snow on lakes is transformed into slush. One could hardly imagine so many different things happening in a physical process that seems at first so simple, before seeing what actually does happen.
Hmm, I’m not sophisticated in crystal formation but your Knight reference makes me think a spot freezes and floats, is covered in heavy snow, sinks, freezes more around the edge, floats again to get covered in snow again, then the edge sink and the process continues. Not sure that could explain the large circles or their “frequency”.
Oh, interesting! I haven’t considered anything like this. But I really like it … If the centers of the rings are nucleation points that would make the patterns at ring intersections a bit more intuitive for me. Using different words … this is a question about what the freezing of slush looks like. If a lake is covered in a uniform bed of slush … could the freezing pattern radiate out from nucleation points. This is what happens for black ice … but in that case … the pattern is controlled by ice’s crystal lattice.
Thanks for chiming in! Cool idea!