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nrron t1_ja6l9ka wrote

The freezer is generally a lot colder than outdoor temps even in the winter and amount of water in the lake is significantly greater than what you’re going to freeze in a freezer.

Also water in a freezer is being cooled on all sides. A lake is only freezing because of cold air over the water. There’s no cold air around or below the water

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Second-Officer-Alex t1_ja6l3p2 wrote

Because is not in contact with the ground, or any warmer/insulated surface. In other words, the water in the freezer is loosing heat all around, not just the top.

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GalFisk t1_ja6temu wrote

If you live in a place that gets cold enough in the winter, you can see this phenomenon on roads when it starts to get cold. The roadway on bridges will be frost-covered in the morning, because they have had cold air all around them, while roadways the ground is still clear.

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coffeeshopAU t1_ja8bzta wrote

It’s a combination of a few things - insulation from the ground, the fact that ice floats instead of sinks, and the sheer volume of water present in a lake compared to an ice cube tray.

First, if you dig below the surface the ground is actually pretty good at staying warm or at least preventing the temperature from dropping below freezing. So a lake is only going to be experiencing freezing temperatures at its surface where it makes contact with the air.

Next, ice floats. If ice sank, it would fill up the lake from the bottom, overwhelming the effects of insulation from the ground because new ice near the surface would be constantly produced from contact with cold air. But because ice floats, it protects the water below it from the cold air. If the temperature is barely below freezing, that’s enough to insulate the water in the lake. If it’s really really cold outside it might be enough to freeze several feet of ice, but eventually it would be enough to start insulating the water below. Not as well as the ground, but enough that the water would be freezing at a much slower rate than if it were in direct contact with the air.

Finally, lakes are really big and have a lot of water in them, and temperatures are usually not cold enough for a long enough period of time to freeze a lake all the way through. A small pond might slowly freeze all the way through from top to bottom if the weather is really really cold for a really really long time. But a big lake with lots of water that is being insulated on all sides by ground and ice would take years to freeze all the way to the bottom. Maybe even decades.

Meanwhile, an ice cube tray, a) does not have the insulating effect of the ground; water can be frozen from all directions. If you pull ice cubes out before they’re fully frozen, you’ll actually see a “bubble” of liquid water trapped inside the ice because of how it freezes from all sides (instead of a layer on top) and b) has very little water in it compared to a lake, and only takes minutes to hours to freeze through instead of years or decades.

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mkomaha t1_ja7vqtd wrote

The water in the freezer is only freezing about an inch of water(ice cube). Lake water will free several inches.

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MeGrendel t1_ja86f7f wrote

Two reasons:

  1. Lakes freeze from the top because the air is the mechanism that is removing heat from the water on the surface, so the surface freezes first, and as ice is lighter than water, it does not sink.
  2. The heat-sink effect of the ground the lake is in. Ever notice that in winter bridges freeze over before the highway on the ground? That's why.
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yono1986 t1_jabidg1 wrote

Depth and quantity of water. Relative to a trough or bucket, a lake is huge. If it's cold enough to freeze a lake down 18 inches, a 12-in tall bucket will freeze solid, while the 20 ft deep lake will not.

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