Why don the oceans freeze?
The amount of water and salt in them contribute to it. Also it is circulated, warm to colder sea. In Arctic and Antarctic, they do, ice cap at the North Pole is over the ocean. As the top layer freezes it throws away salt where by making lower layers saltier and more difficult to freeze. Also this saltier layer is thicker which slowly settles down bringing warmer water to the top which again prevents the whole ocean to freeze.
