In March 2014, Eric Larsen and Ryan Waters set out to traverse nearly 500 miles across the melting Arctic Ocean, unsupported, from Northern Ellesmere Island to the geographic North Pole. Despite being one of the most cold and hostile environments on the planet, the Arctic Ocean has seen a steady and significant reduction of sea ice over the past seven years due to climate change. Because of this, Larsen’s and Waters’ trip—dubbed the “Last North Expedition”—is expected to be the last human-powered trek to the North Pole, ever.

Filled with stunning, full-color photos and GPS maps plotting his progress, On Thin Ice is Larsen’s first-person account of this historic two-man expedition. Traveling across the retreating sea ice on skis, snowshoes, and even swimming through semi-frozen arctic slush, Larsen and Waters each pulled over 320 pounds of gear behind them on sleds through temperatures that plummeted to nearly 70 degrees below zero. At times, they covered little over a mile a day. They were stalked by polar bears and ran out of food. It was, in Larsen’s words, “easily one of the most difficult expeditions in the world.”

More than just a heart-stopping adventure narrative, however, On Thin Ice offers an intimate and haunting look at the rapidly changing face of the Arctic due to global climate change.

Eric Larsen has skied to both the geographic North Pole and South Pole, twice. He was also the first person to reach both poles under human power, and the summit of Mount Everest in a single calendar year. He has raced in the John Beargrease Sled Dog Marathon, summited Mount McKinley, and biked across the United States. A filmmaker, Larsen created “Melting: Last Race to the Pole,” a documentary about his “Save the Poles” expedition, which premiered on Animal Planet in December 2015. Larsen gives motivational and educational lectures to schools, universities, non-profits, and corporations around the world. A frequent media commentator, he has been featured in the New York Times, Time magazine, Outside magazine, National Geographic, The Guardian, and Men’s Journal, as well as on CNN, NBC News, CBS News, and BBC News, among other outlets. He lives in Boulder, Colorado.

Hudson Lindenberger is a Boulder-based adventure writer. His work has been published in Men’s Journal,Skiing, 5280, Women’s Running, Elevation Outdoors, and Story.