Thwaites Glacier reaches speeds of more than 33 feet (11 m) per day. The black box shows the location of four subglacial lakes that drained in 2013, increasing the glacier's speed by about 10 percent.
The ice surface above the lakes sank by as much as 20 meters (66 feet) in less than a year due to the drainage. Subglacial lakes are commonly seen with fast-flowing glaciers.
A new technique revealed how meltwater from lakes beneath Thwaites Glacier drained into the sea. It is the largest outflow from sub-glacial lakes reported for this region of West Antarctica.