Key glaciers in West Antarctica are in an irreversible retreat, a study team led by the US space agency (Nasa) says.
It analysed 40 years of observations of six big ice streams draining into the Amundsen Bay and concluded that nothing now can stop them melting away.
Although these are abrupt changes, the timescales involved are likely measured in centuries, the researchers add.
If the glaciers really do disappear, they would add roughly 1.2m to global sea level rise.
The new study has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union, but Nasa held a teleconference on Monday to brief reporters on the findings.