A massive and surprising change is unfolding around Antarctica. Scientists have discovered that the Southern Ocean is getting saltier, and sea ice is melting at record speed, enough to match the size of Greenland. This change has reversed a decades-long trend and is letting hidden heat rise to the surface, melting the ice from below. One of the most dramatic signs is the return of a giant hole in the ice that hadn’t been seen in 50 years. The consequences are global: stronger storms, warmer oceans, and serious trouble for penguins and other polar wildlife.