The sky is gunmetal gray, a shade somewhere between inviting and malicious. We’re 40 miles due east of Tromsø, Norway, a city that sits on the Norwegian Sea more than 180 miles north of the Arctic Circle. Yesterday, kiteboarders were ripping across the frigid late-April water propelled by gusty winds, a testament to the commonly held belief that of the three Scandinavian bloodlines—Norwegian, Danish, and Swedish—Norwegians are the most hardcore. The proponents of that stereotype, however, have yet to meet Kenth Fjellborg, Arctic Swede.

“Get dressed! Put your boots on!” Fjellborg shouts to jolt us out of the heated van. “When we get going, we’re not going to stop! The sun is hiding in the sky, but we’re going to go right into the white! Men, you do the number one outside. The outhouse is not for gentlemen. But I hate it when pee is spread over the snow.”

It’s the first morning of our journey, and the marching—or, rather, mushing—orders have begun. Six of us, all neophytes, will be guided by Fjellborg on one of his most rigorous Arctic dogsledding adventures. We’re lined up like a United Nations train: Fjellborg is in front; the three American, one British, and two Swedish sledding rookies are in the middle; and 26-year-old Norwegian-­Scottish guide Amanda Calder, who wears two knives at all times—one for dogs and one for ­humans—brings up the rear.

We’ll each lead a team of five or six dogs on a five-day, 160-mile journey from the old Rognli homestead, which sits in the Signal Valley, on a historic backcountry “highway” between Norway and Sweden. We’ll climb 2,400 feet into the Arctic tundra, then travel southeast along frozen waterways that will lead us to Fjellborg’s home in the Swedish village of Poikkijärvi. Poikkijärvi is on the banks of the Torne River, directly across the water from Jukkasjärvi, the village Fjellborg’s ancestors first inhabited in 1690. Nine ­generations of Fjellborgs have lived within ...