Most parts of the Arctic Ocean are a kilometer deep and are continuously covered with ice whose thickness varies between 1-10 m. About one third of the Arctic Ocean is shallow, in particular the region at the continental shelf. Over these shelf areas, ice is absent at least a part of the year, but ice is found year-round over the deep ocean.

Ice conditions all over the world have been mapped systematically for more than 100 years but in remote areas the old data are scarce, unreliable and dependent on daring expeditions. Today’s global satellite information systems are extremely useful for ice mapping and together with submarine measurements a database is available regarding to the Arctic ice conditions. Arctic ice and also climate is governed by two major movement systems: the Transpolar Drift and the Beaufort Gyre. The transpolar drift runs across the Arctic Ocean from Siberia to the Fram Strait between Greenland and Svalbard. Air temperatures and solar radiation and thus the ice thickness of multi-year ice is only partly a function of altitude. The ice extent and thickness is also strongly affected by the warm Gulf Stream which is the reason the Norwegian sea is free of ice throughout the year. Icebergs are most frequently seen around the coast of Greenland but some icebergs have been spotted on odd places like offshore Ireland (1907) and at the Norwegian coast (1929).

Seasonal Variations

Summer
In summer time, the Arctic ice cap is free at most places in the vicinity of the coast. However, because of ocean currents, the cap is continually drifting around at speeds up to 10 kilometers a day. The thickness of the cap ranges from 3 to 4 meters. Under pressure of sea currents local ridges are able to build up to a thickness of 10 to 20 meters. The diameter of the ice cap is in the order of 3500 km. In the open waters between the ice cap and the coast, icebergs and fields of pack ice are floating around. The fields of pack ice may exclude local shipping traffic for periods of days to weeks. The icebergs pose a danger to shipping and fixed infrastructure (moored vessels, platforms, pipelines) in water depths up to 100 meters. In these water depths icebergs may scrape the seabed causing deep scars of up to 100 m width, 10 m depth below the mud line and 50 km in length.