Sea Ice

Sea ice is frozen seawater. Because ice is less dense than its melt, sea ice floats. Sea ice covers about 7% of the Earth’s surface, or about 12% of the world’s oceans. In the North, it is found in the Arctic Ocean, in areas just below it and in other cold oceans, seas and gulfs; in the Antarctic, it occurs in various areas around Antarctica (the continent). Due to the combined action of winds, currents and air temperature fluctuations, sea ice expanses are very dynamic. In the fall and winter, the ice grows progressively thicker, defining floes of various sizes that collide against each other. This activity also goes on in the spring and summer, but during that time part of the ice melts. This ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Unlike sea ice, which is saline, icebergs are made from fresh water. They may be enclosed within sea ice expanses and drift along with it.