Arctic sea ice, NASA/Goddard Space Flight Center

The amount of Arctic ice left has been steadily shrinking. But it’s now dwindled by so much that National Geographic has said their updated maps will feature a much smaller ice sheet, in what they’re calling the most visible change to the atlas since the break up of the U.S.S.R.

National Geographic drew its current map of the Arctic in its 1989 edition of the Atlas. Since then, though, the decrease of not just the area, but the volume of Arctic sea ice (as seen in the graphic below, charting sea ice volume from 1979 to the present) has been sharp. The newest edition, which comes out in September, will redraw the lines into a significantly smaller area, based on NASA and the NSIDC data on the amount of remaining multiyear ice.