BUENOS AIRES • Meltwater could undermine the walls of ice holding back Antarctica's glaciers, scientists reported, a finding that underscores concern about the potential for a significant sea-level rise.

The ice shelves, formed over thousands of years, serve as dams to prevent much of the continent's snow and ice from flowing towards the ocean.

Scientists found that about 60 per cent of the ice shelf area is vulnerable to a process called hydrofracturing, in which meltwater seeps into the shelves' crevasses, some of which are hundreds of metres deep, and triggers collapse.

"This meltwater is heavier than ice, so it can penetrate through the entire ice thickness, just like a knife," said climate scientist Lai Ching-yao at Columbia University's Earth Institute in New York.

It is unclear how long such a process might take. Antarctic weather is highly variable, making it difficult for scientists to determine how much of a role is being played by human-caused climate change.

Dr Lai said, however, that previous research suggested meltwater could cover the ice shelves in about a century.

The new study, published in the journal Nature, used artificial intelligence to identify ice-fracture features in nearly 260 satellite images of 50 ice shelves across the continent. Those ice shelves surround about 75 per cent of the Antarctic coastline.

Finding vulnerabilities in the ice shelves buttressing the glaciers above was a surprise, Dr Lai said.

"Previously, we thought there are going to be places vulnerable to hydrofracture, but that those places might not matter at all for the ice sheet," Dr Lai said.

Scientists fear that losing ice shelves to hydrofracturing will leave Antarctica's ice sheets, which are as big as the United States and Mexico combined, a more direct pathway to the ocean. That could accelerate ice loss and contribute to sea-level rise.

Dr Alexandra Isern, head of Antarctic studies for the US National Science Foundation and who was not involved in the study, said that if "we start seeing the collapse of some of this ice that is there like a wall holding back everything behind it, it's just going to accelerate the pace of sea-level rise beyond what we're probably predicting right now".

REUTERS