In accordance with the Endangered Species Act, the US Fish and Wildlife Service designates as critical habitat 187,000 square miles of on-shore barriers islands, offshore sea-ice, and other areas in northern Alaska, to help ensure the regional protection of polar bears.

http://www.bbc.co.uk/news/world-us-canada-11836156
http://www.doi.gov/news/pressreleases/US-Fish-and-Wildlife-Service-Announces-Final-Designation-of-Polar-Bear-Critical-Habitat.cfm