The designation by the department's Fish and Wildlife Service identifies geographic areas containing features considered essential for the conservation of the polar bear that require special management or protection, an Interior Department release said Wednesday.
The designation covers onshore barrier islands, den areas and offshore sea ice in and around Alaska.
"This critical habitat designation enables us to work with federal partners to ensure their actions within its boundaries do not harm polar bear populations," Tom Strickland, assistant secretary for Fish and Wildlife and Parks, said.
"Nevertheless, the greatest threat to the polar bear is the melting of its sea ice habitat caused by human-induced climate change," he said.
"We will continue to work toward comprehensive strategies for the long-term survival of this iconic species."
The polar bear was protected under the Endangered Species Act as threatened, range-wide, on May 15, 2008, due to loss of sea ice habitat caused by climate change.