Hi, I read that in Antarctica, water under ice is warmer than the atmosphere above the ice, and many animals hide underwater to stay warm. Sea lions and what not. Why is that? Thanks!
In: Planetary Science
Coomb had a great response. If you want something super simple.
Water retains temperature better than air does. That’s why temperature is difference neat bodies of water like oceans and big lakes.
Liquid water can’t get a whole lot colder than 0° C / 32° F otherwise, it would turn into ice. It can get a little bit colder if it’s under pressure or it’s salt water, both of which lower the freezing point, but only by a couple of degrees.
On the other hand, depending on where you are in Antarctica, the air is either always colder than that, or colder than that during almost all of the year except for the peak of summer.
If you’re confused about why water that’s underneath ice is warmer than the ice, it’s because water has the convenient (for us) property that liquid water is actually densest at around 4° C, and the density decreases as it gets colder than that. That means if you have a bunch of water that’s very close to freezing, and some other water that’s at 4° C, the warmer water will sink down, away from the surface, and that means it gets insulated from the very cold air by all the water above it. In an ocean, there’s enough water that it’s impossible for all of the water to freeze except where the ocean is very shallow. And the water below the ice will always be warmer than the ice, because otherwise it would be part of the ice.
ELI5: Antarctica is extremely cold, right? Lots of cold air, like at -50°F.
The water under ice is water. And water can’t be colder than 32°F. If it was, it would be ice.
In the past, some water became ice and floated to the surface of the water, and the ice protects the water from the extremely cold air. So water can continue to stay liquid water under sheets of ice.
“Why doesn’t all the water turn to ice?”
A small glass of water completely freezes faster than a bucket of water right?
The more water you have, the more cold it takes to cool it down. And the ocean is enormous, so it would take a heck of a lot of cold. The earth is warm enough for water to be water and not ice.
Wow, that’s a really interesting question! From what I understand, the weight of the ice on top of the water creates pressure that can raise the temperature of the water underneath. I’m not exactly sure how it all works, but I hope someone can explain it better!
Think of it like a blanket, where it’s warmer underneath and cooler on the top layer which is exposed to the open air. That’s one of the reasons anyway, there’s a lot more at play than that though.
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