McMURDO STATION, Antarctica—It’s often said that Seafarers “sail the seven seas,” and a recent voyage—all the way to Antarctica—proves it. Why? To transport needed supplies, especially fuel, to the U.S. South Polar research station there on McMurdo Sound. It’s a decades-long resupply mission named, appropriately, Operation Deep Freeze (ODF). It’s quite a long ocean-going trek down to the ice-clad continent. But Seafarers union members are used …