Ice Teeth in Iowa

Welcome back to the River Ice Photo Blog! It’s been a while since my last post – in between I retired and became a Professor Emeritus and moved 5000 km (~3000 miles) to the east coast of Canada.  It’s been a mild winter here – up until now at least – and so I’ve not done much river ice hunting.  However, for the first post of 2015 we have some great photos by David M. Brenner – a river ice enthusiast in Ames, Iowa.  David calls these “ice teeth”.

ice teeth-1 c

 

Here’s another picture that David describes as the U-shaped terminus of a lead.

U shaped terminus of a lead c

David writes, “I associate them with open leads that have no frazil ice.  The spacing and regularity can make them look like tractor tracks.  The card in one of the images is for scale.”

He also says that, “On our rivers there are often open areas that never freeze.  Some of the open areas are where warm urban water comes out of storm sewers.  Some are where the fast moving (thalweg) water moves too fast to freeze.  The surrounding ice is strong enough to walk on, especially in 2010.  The teeth form along open leads during cold snaps, and when new have sharp fresh edges.  They are not a melting thing.  I do not know what regulates their even spacing but it may have something to do with water speed etc.  They need the attention of a Physicist.”

I’ve not seen these before, so if any of you river ice experts out there have an explanation of what might be happening here – please comment below.

If you would like to see some of David’s river ice videos, please check out the following links:

Ice teeth formation on the skunk river:
https://www.youtube.com/watch?v=NFCiVph-pHU

David’s youtube channel which is all river ice
https://www.youtube.com/user/TheDbrenner

Thanks David for sharing your photos!

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About Faye Hicks

I am a professor emeritus, civil engineer, animal lover and writer.
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2 Responses to Ice Teeth in Iowa

  1. Steve Daly says:

    I interpret the “ice teeth” as ice dendrites growing on a thin layer of supercooled water at the surface. I associate them with low flow velocities and generally see them on ponds and puddles. However a thin layer of supercooled water can form during frigid weather on flowing water if the buoyancy flux due to heat transfer is strong enough to counter the mixing caused by the flow turbulence. (I admit this is dangerous territory as spontaneous nucleation in a thin layer of supercooled water was once held to be the source of all frazil ice – that is not the case. In almost all river situations the turbulence of the flowing water overcomes the buoyancy flux of the surface heat transfer – but not always.) In puddles, for example, the water surface will supercool in cold weather until ice is nucleated – usually at the edge of the puddle where dirt and other material causes spontaneous nucleation. Then the dendrites will shoot out from the edge across the puddle. The ice will further thicken due to heat transfer and the spaces between the dendrites will freeze as well. Because the dendrites formed first they will be thicker than the remaining ice and will be visible for some time due to their greater thickness.
    The dendrites are rapid ice growth along the a-axis of the ice crystal. There seems to be no limit to the speed at which the dendrites can grow. Their growth velocity is limited only by the rate at which the latent heat can be removed. There is a whole science of dendrite growth too vast to summarize here – and I am not that familiar with it. One interesting aspect is that given a plane surface and certain degree of supercooling, the dendrites will form with a regular spacing, as seen here.

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