A new study in the journal Nature Geoscience found that warm ocean water is melting Antarctica’s ice sheets from below, contributing to sea level rise. Most of the observed melting is in West Antarctica, where more than 20 percent of the ice sheet has retreated across the sea floor. The study cited satellite data that show more than 10 percent of the continent’s glaciers are in retreat—as opposed to less than 2 percent of glaciers that are growing. If all of Antarctica’s ice melted, worldwide sea levels would rise by about 200 feet.