Trainee David Kullualik, of Iqaluit, Nunavut, of Canada's northern territories, looks through binoculars from the bridge of the Finnish icebreaker MSV Nordica as it sails through ice floating on the Chukchi Sea off the coast of Alaska while traversing the Arctic's Northwest Passage, on July 16, 2017. #

Photography and video equipment brought along by an Associated Press team on assignment aboard the Finnish icebreaker MSV Nordica is laid out on the ship's deck on July 8, 2017, while sailing toward the Bering Strait in the North Pacific Ocean. #

Polar maritime lawyer Scott Joblin, from the Australian National University in Canberra, looks over a map aboard the Finnish icebreaker MSV Nordica on July 6, 2017. #

Jyri Viljanen, left, captain of the Finnish icebreaker MSV Nordica and Harri Venalainen, chief officer, navigate from the bridge through ice floating on the Chukchi Sea off the coast of Alaska on July 16, 2017. #

Field biologist Paula von Weller, 45, of Portland, Oregon, aboard the MSV Nordica as it sails in the North Pacific Ocean toward the Bering Strait on July 11, 2017. "Few people in the world get to sail the Northwest Passage," said von Weller, who will be marking her second passage after traveling through with another Finnish icebreaker in 2015. She is observing wildlife in the Arctic and hopes this time to see the elusive narwhal, the unicorn of the sea. "I've been fascinated with the Arctic. It is very special to me. I think it's just this mythical place." #

Trainee David Kullualik, 24, of Iqaluit, Nunavut, aboard the MSV Nordica on July 12, 2017. Kullualik is earning sea days toward his training and hopes to be a captain someday. "Our instructor said it was a trip of a lifetime. I said I don't know about that, I grew up around them [polar bears] and the ice is around us nine months of the year," said Kullualik. "I have three kids and I'm just trying to put food on the table. I think of them all the time." #

Chief steward Mika Tiilikka, 54, aboard the Finnish icebreaker MSV Nordica on July 14, 2017. Tiilikka, who has been growing his beard for 17 years, has worked aboard icebreakers since 2002 and spends about half the year at sea. He told his mother at the age of four that he wanted to be a chef and a sailor and grew up learning her recipes like sauerkraut and pork soup. "She's my inspiration," Tiilikka said. #

Electrician Kaija Peuhkuri, 42, in the machine shop of the MSV Nordica on July 12, 2017. Peuhkuri started as a cook on ships over 20 years ago before going back to school and becoming an electrician on icebreakers in 2009. Growing up on a farm working on machines, she prefers working away at sea as opposed to commuting to a job at home. "I don't want to do this every morning," she said of having to drive to work. "Here, I come downstairs every morning, have a cup of coffee, and I'm at work." #

Radar shows sea ice ahead of the MSV Nordica as chief officer Harri Venalainen navigates the ship through the Beaufort Sea while traversing the Arctic's Northwest Passage, on July 16, 2017. While icebreakers are equipped with sensitive radar systems, ultimately it's up to the ability and experience of the person at the helm to ensure the ship only breaks ice when it’s unavoidable. #

The bow of the MSV Nordica drives through sea ice as it sails the Victoria Strait on July 21, 2017. The icebreaker is equipped with several heavy-duty engines and a hardened bow and hull that allow it either to drive through thin layers of ice or to crush thicker sheets by rising onto the ice with the help of its rounded hull. The ship's massive weight breaks the ice from above. #

A block of sea ice floats in the Franklin Strait in the wake of the MSV Nordica on July 22, 2017. Sea ice forms when the top layer of water reaches freezing point, usually around the start of October. As temperatures continue to fall, this first-year ice grows downward until it is several feet thick. If the ice survives the following summer melt, then it becomes second-year ice. Another cycle and it becomes multi-year ice, which is the toughest kind. #

The azimuth thruster and hull of the Finnish icebreaker MSV Nordica, seen underwater in the Dolphin and Union Strait off the coast of Canada, on July 19, 2017. The thrusters, which can turn 360 degrees, can break ice up to one-meter thick by churning the water underneath. #

Researchers Tiina Jaaskelainen, right, and Daria Gritsenko do yoga in the warm weather aboard the Finnish icebreaker MSV Nordica as it sails the Bering Sea on July 13, 2017. #

Nigel Greenwood, assistant ice navigator and retired Royal Canadian Navy rear admiral, climbs down the six flights of stairs from the bridge to the mess hall for dinner aboard the MSV Nordica on July 12, 2017. #

In this July 13, 2017, photo, trainee David Kullualik is reflected in a deck door window looking out to sea as researcher Ilona Mettiainen reclines in a massage chair aboard the MSV Nordica. #

The sun sets over melting sea ice on Peel Sound along the Northwest Passage in the Canadian Arctic Archipelago, on July 23, 2017. Because of global warming, more sea ice is being lost each summer than is being replenished during winters. Although sea ice is likely to continue forming each winter, it may be restricted to even higher latitudes. Less sea ice coverage also means that less sunlight will be reflected off the surface of the ocean in a process known as the albedo effect. The oceans will absorb more heat, further fueling global warming. #

Ice navigator Captain David "Duke" Snider, from left, Canadian Coast Guard Captain Victor Gronmyr, U.S. Coast Guard Commander Bill Woityra, assistant ice navigator Nigel Greenwood, and biologist Paula von Weller talk over dinner in the mess hall aboard the MSV Nordica on July 10, 2017. #

A bird's wake is cast on the water as the American island of Little Diomede, Alaska, left, and behind it on the right, the Russian island of Big Diomede, are seen from the MSV Nordica in the Bering Strait, on July 14, 2017. The international dateline divides the two islands, putting them currently 20 hours apart despite roughly 2.4 miles (3.8 kilometers) between them. Due to this time difference, Little Diomede is sometimes referred to as Yesterday Isle and Big Diomede as Tomorrow Island. #

Researcher Daria Gritsenko looks out toward the American island of Little Diomede, Alaska, and behind it on the right, the Russian island of Big Diomede on July 14, 2017. #

Tiina Jaaskelainen, second from left, and fellow researchers look out from the MSV Nordica as it arrives in Nuuk, Greenland, after traversing the Northwest Passage, on July 29, 2017. #