Sea ice, ice drift, and oceanic circulation

The episodic freezing over of the surface waters is arguably the most striking feature of the Southern and Arctic Oceans as well as some subarctic oceans such as the Baltic and Okhotsk Seas. Millions of square kilometers are covered by ephemeral layers of ice that are on average less than 1 m thick. This pack ice is highly dynamic, drifting on the underlying ocean currents, and its distribution is greatly influenced by prevailing winds. The ice is not simply an impervious layer of frozen water, but does in fact provide a variety of habitats to create a productive biome which is pertinent in the biogeochemical processes in the surface waters and at the air–ocean interface.