The huge cavity – which is approximately 1,000 feet tall, about as tall as New York City's Chrysler Building – is growing at the bottom of the Thwaites Glacier and is large enough to have once contained 14 billion tons of ice, according to NASA. Most of that ice melted over the last three years.
"We have suspected for years that Thwaites was not tightly attached to the bedrock beneath it," Eric Rignot of the University of California, Irvine, and NASA's Jet Propulsion Laboratory in Pasadena, California, said in a NASA post. Rignot is a co-author of the new study, which was published in Science Advances. "Thanks to a new generation of satellites, we can finally see the detail," he said.
Scientists captured the cavity with the help of radar on its Operation IceBridge, which began in 2010 and studies links between the climate and conditions at the Earth's polar regions. The researchers also reportedly used data from Italian and German spaceborne radars.
"[The size of] a cavity under a glacier plays an important role in melting," the study's lead author, Pietro Milillo of JPL, said in a statement. "As more heat and water get under the glacier, it melts faster."
According to NASA, the entire Thwaites Glacier, which is the size of Florida, is responsible for about 4 percent of global sea level rise and holds enough ice to raise the world's oceans by a little over 2 feet.
The Thwaites Glacier is extremely difficult for scientists to reach, but soon they will be able to get a much better picture of what's happening. The International Thwaites Glacier Collaboration between the U.S. and the United Kingdom will begin field experiments in the Southern Hemisphere summer of 2019-20.
A recent study showed that ice in Antarctica is melting six times faster than it did in the 1980s, including in areas that were previously thought to be stable.
"Understanding the details of how the ocean melts away this glacier is essential to project its impact on sea level rise in the coming decades," Rignot told NASA.
Fox News' Chris Ciaccia contributed to this report.