Inside a small building surrounded by a gate on a military base in Anchorage, Alaska, sits one of North America's most important first lines of defense.
Maj. Christopher Perham unlocks the gate that leads in, followed by a series of doors.
"This is the base of our operations here," Perham says.
He's part of the Alaska Air National Guard in the 176th Air Defense Squadron. But he works for the North American Aerospace Defense Command, better known as NORAD, which is headquartered thousands of miles away in Colorado.
"We have approximately 40 operators on a day-to-day basis that conduct the mission," Perham says. "We have several sections. We've got identification. We have surveillance."
The patch on his uniform puts it this way: "Eyes of the North" — a reference to the mission here, watching for threats every hour of every day.
KUNC investigative reporter Michael de Yoanna travels with the U.S. Air Force to the Bering Strait to explore the threat climate change poses to national security, as part of a collaboration with Reveal. Listen to and read the full story here.