Sea Ice
Arctic sea ice cover varies substantially over the year, with end-of-winter ice cover generally being two to three times as large as at the end of summer. Sea ice is an important element of the Arctic system: (1) acting as a barrier between the underlying ocean and the atmosphere, (2) limiting the amount of absorbed solar energy during the summer due to its high albedo, (3) providing a habitat for biological activity, and (4) limiting human access to the Arctic Ocean.