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.

This matters because Totten glacier and its ice shelf are the only thing keeping an area of ice larger than the state of California from breaking up. If all that ice were to end up in the ocean tomorrow, sea levels would rise by 10 to 20 feet—flooding San Francisco’s iconic Ferry Building, most of Manhattan’s Lower East Side, and the Lincoln Memorial in Washington, DC.

In some ways, this should come as no surprise. For decades researchers have been projecting that the planet’s polar ice reserves will wither in the face of rising temperatures. But more recent satellite data, models, and fieldwork have revealed that it’s happening faster than anyone expected. And increasingly, scientists are finding evidence to pin that Antarctic acceleration on a less obvious aspect of climate change: wind.

Last year, researchers from the US and Australia discovered that churn from deep undersea canyons was bathing the underside of Totten glacier in water warm enough to melt it. But the mechanisms were still a mystery. On Wednesday, they published a study showing that westerly winds blowing off the coast of Antarctica are driving the upwelling, and leading to faster ice flow on the glacier.

To get a feel for why that’s not normal, it helps to understand what’s going on at the ocean-ice interface. As glaciers and ice shelves melt, they deposit their cold, fresh water onto the ocean surface, where it sits above warmer, saltier, denser water. It’s not a gradual transition, but a sharp one. Like when your bottle of salad dressing settles in the refrigerator and you have to shake it back up before serving. That line is called a thermocline, and scientists can measure exactly where it is in the water column. If it rises up to where the glacier is, that’s when you get melting.

Surface wind causes warm water to upwell at the continental shelf break, the warm water melts Totten Ice Shelf from below, and the glacier responds by speeding up. Chad A. Greene, University of Texas Institute for Geophysics

By comparing satellite images with oceanic wind records and water temperature and salinity data streaming in from a sensor floating nearby, the team was able to track the thermocline at Totten over time. They found that when the winds blew strong from the west, warm water rushed up and into the glacier. When the winds blew from the east, the thermocline sank back down and melting ceased.