Why doesn the Arctic Ocean freeze all the way through?
To begin with, I assume you know that when water begins cooling, it becomes less dense as it cools below about 39°F. This is why lakes, ponds, and then oceans begin to freeze from the top down. We have a graphic and text with more on this. Also, salty sea water freezes at about 29°F. In the Arctic, the 10 – 15 feet of ice that covers the central Arctic Ocean is a pretty good insulator, which helps keep the water below the ice warm enough not to freeze. Also, relatively warm water enters the Arctic Ocean between Iceland and Europe and circles the entire ocean below the ice. A layer of colder water, called the halocline, keeps this warmer water from melting the ice above. If you look at our Arctic Ocean hides icy puzzles graphic, you will see how this works. If you click on “Arctic Ocean currents” on the graphic, you’ll see how the water flows. Clicking on number 3 will show you a cross section of the water with the layers, including he halocline. You might also be interested in a story
