I live near a river in the Pacific NW (USA) and it has been cold (low teens °F, around -10°C) for over a week. The river is about 5-6 feet (1.5–1.8 metre) deep and moving fast enough so the river at the surface is completely ice free. The bottom of the river has ice attached to the rocks and occasionally the ice pops off and floats to the surface. This seems to indicate that either the rocks are below freezing or the water is supercooled and forms ice at the rock because the speed of the water at the rock surface is slower.

Has there been an analysis of this phenomenon?

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    $\begingroup$ its called anchor ice. en.wikipedia.org/wiki/Anchor_ice and should have popped up if you tried googling "ice at the bottom of stream". $\endgroup$
    – John
    Jan 16 at 2:02
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    $\begingroup$ @John Thanks. It didn't occur to me to Google that phrase. $\endgroup$ Jan 16 at 2:09
  • $\begingroup$ @John so is the reason it forms at the bottom because the turbulent mixing higher up prevents it from remaining frozen?? $\endgroup$ Jan 16 at 9:23
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    $\begingroup$ @JeopardyTempest Frazil ice formation seems to be the important step: en.wikipedia.org/wiki/…. $\endgroup$ Jan 16 at 18:12


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