Survival, evasion, resistance and escape (SERE) specialists going through upgrade training learn how to construct an igloo on Utqiaġvik (Barrow), Alaska, Jan. 14, 2021. Igloos were originally used by the Inuit tribe of northern Alaska and are still in use today. They provide warmth and shelter from extreme winds and sub-zero temperatures. (U.S. Air Force photo by Master Sgt. Ryan M. Dewey)