Tucked against glacier-capped mountains, the Begich Towers loom over Whittier, Alaska. More than 80 percent of the small town’s residents live in the Cold War-era barracks in this former secret military port, whose harbor teems every summer with traffic: Barnacle-encrusted fishing boats, sightseeing ships, sailboats, superyachts and cruiseliner monstrosities. This summer, coronavirus travel restrictions put a damper on tourism in the usually buzzing port. Then came warnings of a potentially devastating tsunami.