Bubble rings in pond ice

[Malcolm Banks]

Following the snowfall just over a week ago I duly swept the snow off my pond and resisted any attempts to break the ice or provide a "breathing hole".
I did notice bubbles of many sizes in the ice that appeared to be trapped gas (mostly oxygen I hope). When I looked more closely today there appeared to be a series of about 8 bubble formations that were ring shaped, whilst in other areas the bubbles were more evenly distributed. My wife thinks it's a bit nerdy but I should like to know what causes the bubble rings. My best guess is oxygen given off by a columnar oxygenating plant such as Hornwort (Ceratophyllum demersum) that I know is in and around that area, but is also elewhere with no rings visible, so I would be grateful for any authoritative suggestions.
M

[Kayleigh]

Toxic gasses can get trapped by ice the rotting leaves and pond plants can produce it.
I am not saying you should do this or I am right but I melt a small amount of my pond as the birds drink form it.

[Malcolm Banks]

Thanks Kayleigh - Yes for sure the pond ecosystem continues to work in the winter, albeit at a much reduced rate, and the normal byproducts, including gases of various kinds will be produced. I am pretty assiduous in fishing out leaves (when not frozen) and removed about half of the sludge from the pond about 6 weeks ago, so I am hopeful that a good proportion of the gas will be oxygen. I am still curious about the rings though.

Couldn't agree more with you about providing liquid water for the birds, not just for drinking but for feather care. I do my best to keep my birdbath ice free, the first kettle of boiling water in the morning is not for the tea!
M

[tom00_uk]

Originally Posted by Malcolm Banks

Couldn't agree more with you about providing liquid water for the birds, not just for drinking but for feather care. I do my best to keep my birdbath ice free, the first kettle of boiling water in the morning is not for the tea!
M

dont forget though that boiled water will freeze faster than unboiled water

[Brocakat]

I've heard of this tale - is it for real ?

[Malcolm Banks]

Yes, good question Brocakat, a flashback to schooldays physics - I remember the maxim but not the cause, so just checked it out and it appears that the causes may be multifactorial but although it occurs and is real, no-one really knows exactly why it occurs. Try:
Can hot water freeze faster than cold water?
quite an interesting read, thanks for the prompt Tom00.
I am assuming that you mean the boiled water and not the bubble rings, which were definately real.
M

[free spirit]

I think you will find that the ice is thicker in some areas than others. I have found when I have picked a small sheet of ice off a pond it has a flat surface but is uneaven under neath, but still has a sort of pattern of thickness. example I think the rings are formed when the ice portrudes slightly more below the surface only in small ares, and where it is thinest it will form a bubble, well thats my theory.
free spirit.

[Malcolm Banks]

Mmmm.....I can see what you mean but if some sort of ring-shaped protrusions in the underside of the ice are the cause, what causes them to form and what is it about this formation that restricts it to one particular area of the pond about 50cm wide that runs from the middle of the pond to within 20cms of the eastern edge?
I should have added that the bubble rings are restricted to the area that has the longest sun exposure where C. demersum is growing. Other regions of the pond either do not have Hornwort or are in an area that gets more shade. This would tend to favour the oxygenating columnar plant theory, but then I may be suffering from an objectivity deficit disorder.
M

[free spirit]

I know we have fluctuations in air currents above the pond. What if we have air and gas fluctuations below the ice? and this may be linked to a larger irregular ice pattern forming......or is this theoretical rubbish...LOL.
free spirit

[tom00_uk]

the sun is probably hitting a substance that's darker than the ice and melting a small bit, this void then fills with air leaving the ice and is repeated until the surface is covered in snow etc cancelling out the sun

these ice fluctuations in thickness will also come about from the propagation sites for the ice, you can do this your self by freezing water in a smooth sided vessel and also in the same shaped vessel with a few twigs etc sticking through the surfaces. instead of the ice just forming thick round the edge it will also be thicker round the object. repeated breaking of ice on a pond etc surface is carried out to strengthen ice as it will refreeze thicker and you can end up with a surface to drive on or land a plane