The fate of the West Antarctic Ice Sheet, one of the most vulnerable glacial systems on Earth, has become a central scientific and policy question as global sea levels continue to rise. Researchers agree that the collapse of parts of this ice sheet is now likely, but major uncertainty remains over how quickly it will happen and what that means for communities across the world.
The West Antarctic Ice Sheet contains enough frozen water to raise global sea levels by five metres. If that volume were released into the ocean, it would redraw coastlines and threaten major cities including New York, Miami, Houston and New Orleans. An estimated one billion people worldwide live less than ten metres above sea level.
The first major warning came in 2014, when NASA announced evidence that several glaciers draining into the Amundsen Sea were losing ice faster than snowfall could replace it. Researchers said at the time that the retreat appeared irreversible.
Two years later, a study published in *Nature* suggested that the process could unfold much faster than previously believed. The research described “marine ice cliff instability,” a mechanism in which towering cliffs of glacial ice can break apart rapidly once they are exposed. This raised the possibility of a runaway collapse that would accelerate sea-level rise within decades rather than centuries.
The Intergovernmental Panel on Climate Change responded by including a scenario in which global sea levels could rise by more than two metres by the end of this century if emissions remain high. A long-term projection showed the potential for up to fifteen metres of sea-level rise by the year 2300.
Not all researchers, however, agree with the runaway collapse theory. A growing number of studies have identified factors that could slow down retreat. They include the collapse of cliffs into a slurry of broken sea ice that forms a temporary barrier, and the geological “rebound” of land as ice mass decreases. Recent findings suggest that the bedrock beneath Antarctica can rise much faster than previously assumed, potentially stabilising parts of the ice sheet over time.
Despite these counter-arguments, many glaciologists say the risk remains substantial. Scientists point to examples including the sudden collapse of the Larsen B ice shelf in 2002, which destabilised the glaciers behind it almost immediately. Similar processes are now being observed in West Antarctica, especially around the Thwaites Glacier, sometimes referred to as the “Doomsday Glacier.”
There is also a growing concern over surface melt caused by warmer air. Meltwater can deepen cracks in ice shelves and lubricate the ground beneath glaciers, hastening their flow towards the ocean. Some researchers argue that many computer models underestimate this effect, which could bring faster retreat than expected.
Current projections from the IPCC estimate between half a metre and one metre of sea-level rise by 2100. That figure includes melt from Antarctica and Greenland, shrinking mountain glaciers, and the expansion of warmer seawater. If the most rapid collapse processes prove correct, Antarctica alone could double that contribution.
Scientists say the level of climate pollution released in the coming decades will determine the size of the risk. “The one thing we do know is that the more carbon dioxide we put into the atmosphere, the greater the danger,” said Robert Kopp, a climate policy specialist at Rutgers University.
Regardless of how quickly the ice sheet collapses, experts warn that the shape of the world’s coastlines will change dramatically. Many regions face an inevitable future of higher tides, stronger storms, and the need for costly adaptation measures such as sea walls, land restoration and population relocation.
By the end of this century, our coastal maps may look very different from those of today. The question scientists are working to answer is not whether the oceans will rise, but how soon and how high.