The melting of part of an ice sheet in Greenland is nearing tipping point and further environmental damage could follow, researchers said.
Analysis of the Jakobshavn drainage basin revealed that the central-western Greenland ice sheet is reaching a stage from which it cannot recover.
Data indicated that a critical threshold has been reached after a century of accelerated melting.
"We might be seeing the beginning of a large-scale destabilisation, but at the moment we cannot tell, unfortunately," said Dr Niklas Boers from the Potsdam Institute for Climate Impact Research, one of the two authors of the research.
"So far, the signals we see are only regional, but that might simply be due to the scarcity of accurate and long-term data for other parts of the ice sheet."
Dr Boers and Martin Rypdal from the Arctic University of Norway concluded that this part of the Greenland ice sheet is losing stability, and is very close to tipping into a state of accelerated melting, PNAS said on Monday.
Should that scenario play out, it will not be possible to save the sheet even if the Arctic warming trend was halted in the coming decades.
An ice sheet can only maintain its size if the loss of mass from melting is replaced by snow falling on to its surface. The warming of the Arctic disrupts that cycle.
As the surface of the ice is exposed to higher temperatures, it leads to more melting, height reductions and accelerated loss of mass.
After a point, this process cannot be reversed because a much colder climate would be needed for the ice sheet to regain its original size.
"We need to monitor the other parts of the Greenland ice sheet more closely, and we urgently need to better understand how different positive and negative feedback might balance each other, to get a better idea of the future evolution of the ice sheet," Dr Boers said.
The work is part of the Tipes project, co-ordinated and led by the University of Copenhagen in Denmark and the Potsdam institute in Germany.