https://www.wired.com/story/want-to-study-permafrost-get-it-before-its-gone/ > This story originally appeared on Undark and is part of the Climate Desk collaboration. > To enter the Fox permafrost tunnel—one of the only places in the world dedicated to the firsthand scientific study of the mix of dirt and ice that covers much of the planet’s far northern latitudes—you must don a hard hat then walk into the side of a hill. The hill stands in the rural area of Fox, Alaska, 16 miles north of Fairbanks. The entrance is in a metal wall that’s like a partially dissected Quonset hut, or an enlarged hobbit hole. A tangle of skinny birches and black spruce adorn the top of the hill, and a giant refrigeration unit roars like a jet engine outside the door—to prevent the contents of the tunnel from warping or thawing.