Scientists have observed an unexpected phenomenon in Antarctica this year—it’s missing enough sea ice to cover all of Argentina. Antarctica loses its most ice yearly at the end of February during the continent’s summer, then the ice regenerates as temperatures drop again. But this year that hasn’t happened. The amount of sea ice right now is about 1 million square miles below the recent average, or about the size of Argentina, and scientists don’t yet know why. “The game has changed,” Ted Scambos, a glaciologist at the University of Colorado Boulder, told CNN. “There’s no sense talking about the odds of it happening the way the system used to be, it’s clearly telling us that the system has changed.”