Researchers from the University of Washington, using computer modeling, also report that the West Antarctic ice sheet is collapsing.
"Our simulations provide strong evidence that the process of marine ice-sheet destabilization is already under way on Thwaites Glacier, largely in response to high subshelf melt rates," the authors wrote in the study, to be published May 16 in Science. "Similar behavior also may be under way on neighboring Pine Island Glacier."
If there is good news, the scientists say, it's that the collapse could take anywhere from 200-900 years. However, once started, it's unlikely to stop.
"One potential way in which the retreat of these glaciers could be stabilized would be if during its retreat the grounding line -- the boundary between floating and grounded ice -- were to reach a region of the ice-sheet bed where the bed slopes towards the ocean," said glaciologist Jonathan Kingslake of the British Antarctic Survey, who wasn't involved in either study. "The authors show that almost no regions of such stabilizing bedrock exist in this region behind the current grounding line. Hence, they conclude, the retreat is likely to continue unstably for decades to come."
The idea that the glacier's retreat once started could not be stopped has been discussed since the 70s, Anandakrishnan said. "We've crossed a critical threshold. We finally have enough observations to put it all together and say 'We're finally in this state.'"