Once Antarctica chilled enough for the seawater around it to start freezing, a strange chemical fact came into play: there is no such thing as saltwater ice. When seawater freezes, it leaves its salt behind. The water around the forming ice thus becomes even saltier—and saltier water can stay liquid at colder temperatures. So whenever a bit of seawater freezes, it creates two things: freshwater ice and extremely salty, extremely cold liquid water.
