Cartographers working on the latest edition of the National Geographic Atlas of the World say that Arctic sea ice loss is the greatest visible change compared with previous editions of the map outside of the “breakup of the U.S.S.R.”

According to National Geographic, in the 10th edition of the Atlas, which will be released on September 30, the depiction of multiyear ice—or ice that has survived for at least two summers—is now a significantly smaller area than on previous maps.

“You hear reports all the time in the media about this,” said National Geographic Geographer Juan José Valdés. “Until you have a hard-copy map in your hand, the message doesn’t really hit home.”