According to a new study published in the journal Nature, the massive glacier, which had been stable for several thousand years, is now slipping into the ocean at an increasing rate.
The ice sheet of concern, the Thwaites system, which sits in a depression below sea level, has previously been kept at bay by an outer wall, a mixture of rock and ice, along the ocean. But that wall -- now weakened -- has been destabilized by rising ocean temperatures.
"This is really happening," Thomas P. Wagner, a climatologist and researcher who has helped NASA conduct several polar ice studies, told The New York Times. "There's nothing to stop it now. But you are still limited by the physics of how fast the ice can flow."
The Thwaites glacier is the portion of West Antarctica most vulnerable to accelerated melting and collapse. But author of the new study, Ian Joughin, says Thwaites' collapse will likely endanger the entire West Antarctic ice sheet.
"Imagine trying to take out part of a building and expecting the other half to keep on standing," he explained to National Geographic.
Joughin, a researcher who studies glaciers at the University of Washington, says Thwaites and other portions of West Antarctica won't simply melt away as much as they will suffer mechanical failure -- the glaciers calving off into the ocean in the form of icebergs, the ice sheet slipping slowly into the ocean.
Though the complete collapse of Thwaites will be slow -- 200 years if melting increases, and 900 regardless -- Joughin and his colleagues say the runaway ice sheet is unstoppable.
Thwaites' disintegration will raise the level of the ocean by roughly two feet. Should the rest of the West Antarctic ice sheet follow suit, sea level would rise 11 feet.
Scientists say human-caused global warming is likely accelerating the glacier's collapse, but that a range of factors are at play (some natural), including: stronger winds, warmer ocean water contacting the glacier, and ozone layer holes present above the South Pole.