The Army's research facility includes a permafrost tunnel — about a third of a mile long — that has Ice Age-era animal bones jutting out from the walls.
About 130 U.S. soldiers are returning to their bases after being deployed to a remote Alaska island amid a spike in Russian military activity in the area.
Russian military planes and navy vessels, including two submarines, have come close to Alaska in the past week as Russia and China conducted joint drills.
