From the air, the largest glacier on the biggest ice sheet in the world looks the same as it has for centuries; massive, stable, blindingly white. But beneath the surface it’s a totally different story. East Antarctica’s Totten Glacier is melting, fast, from below. Thanks to warm ocean upwellings flowing into the glacier—in some places at the rate of 220,000 cubic meters per second—it’s losing between 63 and 80 billion tons of previously frozen fresh water every year.