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During an ice age, would it be possible for a great lake to be frozen while a relatively nearby river was still running? To help illustrate my point:

Would it be possible for Lake Michigan (or parts of it) to be frozen up to ten meters deep? All the while the Missouri River was still running around Kansas City? Or would all surrounding bodies of water necessarily be frozen solid?

Are such varying temperatures and conditions feasible in any way? What should be taken into account?

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    $\begingroup$ All you need a new Glacial Maximum. $\endgroup$
    – AlexP
    Commented May 30, 2019 at 21:03
  • $\begingroup$ Do you count the Missouri as running if it is not frozen solid? Or does only open water = running? $\endgroup$
    – Willk
    Commented May 30, 2019 at 22:45
  • $\begingroup$ @Willk, Perhaps my question was a bit backwards. I was wondering if all surrounding waters would be frozen solid under such conditions. Or if some close bodies of water could still be (partially) liquid or in motion. To answer your question: Yes. Not frozen soild = running. $\endgroup$
    – McMurphy
    Commented May 30, 2019 at 22:55
  • $\begingroup$ I have a problem during extra cold winters (significant periods below 0F) where water continues to flow under the snow pack. It then crosses my driveway which is clear of snow. Some of it does freeze which eventually creates a dam, but it keeps right on flowing. $\endgroup$
    – rtaft
    Commented May 31, 2019 at 13:49
  • $\begingroup$ "Or would all surrounding bodies of water necessarily be frozen solid?" Which bodies are you referring to? $\endgroup$
    – RonJohn
    Commented May 31, 2019 at 14:48

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Sure, and it did. While there was no Lake Michigan during the Last Glacial Maximum, the Laurentide Ice Sheet was up to a 1500 meters or more thick around the Chicago area, while it never reached as far south as Kansas City, which means rivers would be running during the summer. A sufficiently large river could run all year (albeit frozen over).

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It sort of depends. Rivers rarely (if ever) have a single source for their headwaters. Rivers are a collection of hundreds of smaller tributaries.

Sealing a single source, even a major one in ice would certainly reduce the flow of water downstream, but unless you remove the majority it will still flow to some degree.

So the real question I think we need to ask is, what all is frozen? Once you define that I think you will be able to answer it yourself.

A few things to consider:

  • Is the glacial area spreading or retreating?
    • If it is expanding you can expect the flow of the river to continue to dwindle
    • If it is retreating (end of the ice age) you'd likely see larger flows.
    • If its just sort of stable the edges of the glaciers will melt, providing a regular flow, probably heavier in the summer months and lower in the winter months...possibly turning off completely in the winter.
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    $\begingroup$ It's a minor point, but Lake Michigan isn't a source for the Missouri river. That being said, this scenario would certainly reduce the flow from tributaries of the Missouri in Montana, Idaho, Wyoming, and North Dakota due to the likely extent of the ice sheets. $\endgroup$
    – Brian
    Commented May 31, 2019 at 18:36
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I think I can realistically say that the Glacial Ice was, in fact far far deeper that a handful of meters. Most estimates range from the mile-thick to only a couple of thousand meters. In most cases, it is considered that the Missouri river's current location is a direct result of the glaciers depositing earth, rocks, etc at the terminal edge. Prior to the Ice Ages, it is thought that there simply were no 'great lakes', they were scraped from the earth by ice over long periods of time.

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    $\begingroup$ You have your measurements backwards. A couple of thousand meters is more than a mile. $\endgroup$
    – Keith Morrison
    Commented May 30, 2019 at 22:49
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    $\begingroup$ Specifcally, a mile is about 1600m. $\endgroup$
    – David Richerby
    Commented May 31, 2019 at 10:57
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Perhaps quickly-moving water would keep better-mixed and a more uniform temperature, and thus you wouldn't have some parts (e.g. the surface) freezing while other parts are significantly warmer?

I wonder if the movement also warms via friction as water molecules rub against the banks and bottom, or against other water molecules?

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the physics of water is unusual, in that as it approaches freezing point, it becomes less dense - thus ice forms on the surface. Below the Ice at the North pole is sea water.
Now - bring this down scale a bit.

Yes you can have water below metres of ice. Inland though - where does it come from and go to? If the surface (think air temperature) is frozen, then rain will fall as snow or ice, and not penetrate the ground to provide water to flow beneath the ice, or, indeed, to support the ice above it. You will have some water below the ice, but it won't be in a hurry to go anywhere because there is no new water collecting (until spring, if you have one) Depending on the length of time you are projecting, whilst the river will continue to run because it is warmer than the ice, so will 'melt' it's way out by hydraulic pressure, eventually it will cease.

A

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