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Does Pressure Keep The Deep Ocean From Freezing? No. But you were probably hoping for a more in-depth answer, so let's take a deep dive to the bottom of the Mariana trench, the deepest part of the ocean. Down here, there's 11km of water pressing down on you from above, and the weight of all that water generates around 1000 times atmospheric pressure. And pressure can melt ice - like, you only need 500 times atmospheric pressure to melt ice down to negative four degrees celsius. If you have 1000 times atmospheric pressure (like at the bottom of the Mariana trench), then you'll melt ice down to around
negative nine celsius. But that's for fresh water. For salty sea water, everything more or less gets shifted colder depending on the salinity: on the ocean's surface, salt water doesn't freeze until around two degrees celsius below zero; at 500 times atmospheric pressure salt water doesn't freeze until around six degrees celsius below zero, and at the bottom of the Mariana trench, salt water wouldn't freeze until around 11 degrees below 0. But for various reasons related to circulation and salinity and temperature and convection and the fact salt water freezes into freshwater ice. for complicated reasons, deep ocean water is
often around 0° to 4° celsius, and doesn't get much colder than 2 degrees celsius below zero, which are temperatures at which the water would stay liquid from salt alone, even without the additional pressure. So while pressure could in principle keep the ocean from freezing, it doesn't really get a chance. Alright, now's your chance to try out the new math and science courses from this video's sponsor, Brilliant.org. This course shows you how to analyze Airbnb data to figure out the best place to buy a rental property, and this one teaches you how to program by coding a familiar-looking game. Hands-on
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