High in the Arctic, myth is melting into reality: as temperatures rise, newly ice-free waters are turning the Northwest Passage from a fable into navigable waterways.  And while global superpowers, like America, Russia and China, see great economic benefit in finding a northern route that can act as a new superhighway for goods to equal the Panama and Suez Canals, at the same time we are losing sight of the real impacts on Arctic peoples, wildlife, and ecosystems. Global warming is ravaging the Arctic-and threatening the planet’s stability-while we jockey for position for control of emerging waterways.  Kieran Mulvaney explores all of these issues in his great new book, “Arctic Passages: Ice, Exploration, and the Battle for Power at the Top of the World.” He is our guest today and, yes, we talk about President Trump’s Greenland fascination as well as the best tourist option for getting close to polar bears.