A splash of Arctic ice down my back and a hug from a hairy Norse sea god confirmed my initiation into the Arctic Explorer’s Club after my Havila Voyages cruise ship crossed the Arctic Circle.   For seasoned sailors, the crossing is a milestone. For my fellow passengers aboard the Havila Pollux off Norway’s northern coast, it was a lively deck party. We celebrated our crossing with a sailor’s rum drink known as black magic, a concoction that warms the soul and energizes the spirit....