They say they've discovered two openings that could channel warm seawater to the base of the huge Totten Glacier and bring the threat of potentially disastrous melting.
The glacier is bigger and thinning faster than all the others in East Antarctica.
It contains enough ice to raise the global sea level by at least 11 feet (3.4 meters), according to researchers from the University of Texas at Austin
who were among the authors of a new study
published this week in the journal Nature Geoscience.
Scientists had previously detected warm water on the seaward side of the glacier. But until now, they had found no evidence that it could threaten coastal ice.
"We now know there are avenues for the warmest waters in East Antarctica to access the most sensitive areas of Totten Glacier," said Jamin Greenbaum, a University of Texas Ph.D. candidate and the lead author of the study.
Worries about other parts of Antarctica
The two gateways on the seafloor that lead to the base of the glacier offer an explanation for why Totten Glacier has been melting so fast.
Scientists have already warned about the consequences of melting ice in West Antarctica. NASA said last year that glacial retreat in some areas "appears unstoppable."
The increase in sea levels that would be caused by the melting of all the ice in Totten Glacier is estimated to be roughly equivalent to the contribution from a collapse of the entire West Antarctic Ice Sheet.
The United Nations' report on climate change last year estimated sea levels could rise between 1 foot and 3 feet by 2100. Such a rise could displace tens of millions of people from coastal areas around the world.
Melt could become 'irreversible'
But that calculation doesn't factor in the latest research on Antarctica.
"While the Totten melt may take several centuries, once change has begun our analysis reveals it would likely be irreversible," Greenbaum said in comments cited by the Australian Antarctic Division
To prevent the process from becoming unstoppable, atmospheric and oceanic conditions would need to change so that snowfall outpaces coastal melting, the researchers said.
The scientists gathered their data through a series of aerial surveys using technology that can scan the ice and seafloors in areas that are inaccessible to icebreakers. The team included researchers from the United States, Australia and the United Kingdom.