Freezing point of water changes with salinity and impurities. By definition a liquid cannot be below its freezing point until it has completed its phase change.

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RetroTechie a day ago | parent | next [-]

> By definition a liquid cannot be below its freezing point until it has completed its phase change.

Supercooled water is a thing: (and I've seen it a few times myself)

https://en.wikipedia.org/wiki/Supercooling

	▲	wahern a day ago \| parent \| next [-]
		Superheating, too, and that's something that can happen in a microwave, occasionally causing severe burns when superheated water flash boils. AFAIU, it's the same phenomenon--lack of nucleation sites to kick-off the phase transition.
	▲	mrloopex a day ago \| parent \| prev [-]
		Does that mean every TTT diagram is wrong? Nevermind I just learned about CCT diagrams. I guess having only one year of materials engineering means I should STFU. :)

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FromHoiPolloi a day ago | parent | prev [-]

Yes. My point was that it's easier(?) to get below freezing point above water than below. So while the cold air keeps the upper part of the iceberg (relatively) intact - it will slowly melt below the sea until the center of gravity changes enough to flip over.